Effects of an aquatic protocol on electromyography activation and strength of lower limb muscles in blind women: A randomized controlled trial.

In orienteering, a specially prepared map and a compass are used to navigate point to point in unfamiliar and uneven ground. Races test navigational skill, and running ability of the competitors. High levels of fitness and running speed are requested to cover long distances and climbs, and to compete successfully in international events. The strength of knee flexor and extensor muscles was investigated in young male orienteers. Eight junior Italian team orienteers (experimental group, EG, age, 19±1.6yr; weight, 62±7.0kg; height, 175±5.4cm; BMI, body mass index, 20±1.3kg/m2), and a control group (CG) of 8 cross country track and fields runners (20±4.5yr; 67±3.6kg; 179±3.5cm; 21±1.2kg/m2) volunteered. Right lower limb was dominant for all participants. Running capacities were tested on 3000m mean running speeds (EG, 17.8±1.0km/h; CG, 20.1±0.2km/h). Each athlete performed 5 repetitions of right and left knee flexion and extension at the angular speeds of 60-120-180-240-300deg/sec respectively. The peak torques of each movement at different angular speeds were measured by an isokinetic dynamometer. The obtained values were averaged within subject. Descriptive statistics were computed within group, movement, angular speed, and side. The differences between groups were compared by Mann-Whitney test; those within group, between sides were compared by Wilcoxon test. Statistical significance was set at 5% for all comparisons. Ages, weights, heights, and BMI of EG and CG did not differ (p>0.05, for all comparisons). CG runners were significantly faster than EG (p 0.05 for all comparisons). On average, EG performed peak torques larger than those obtained by CG, in both sides, and movements. The differences were significant in right knee flexor muscles at 60, 120, 300deg/sec (p<0.04; 0.03; 0.05 respectively), in left knee flexors at 60deg/sec (p<0.04), and in right knee extensor muscles at 60deg/sec (p<0.02). Further investigations into this matter should be extended to a larger group of participants and to other muscular districts. Data could be of interest for athletes, coaches, and physicians to allow a correct training planning, to prevent accidental injuries, and also to quantify the effects of rehabilitation.

Full text Figures and data Side by side Abstract Editor's evaluation Introduction Methods Results Discussion Data availability References Decision letter Author response Article and author information Metrics Abstract Background: Postoperative knee instability is one of the major reasons accounting for unsatisfactory outcomes, as well as a major failure mechanism leading to total knee arthroplasty (TKA) revision. Nevertheless, subjective knee instability is not well defined clinically, plausibly because the relationships between instability and implant kinematics during functional activities of daily living remain unclear. Although muscles play a critical role in supporting the dynamic stability of the knee joint, the influence of joint instability on muscle synergy patterns is poorly understood. Therefore, this study aimed to understand the impact of self-reported joint instability on tibiofemoral kinematics and muscle synergy patterns after TKA during functional gait activities of daily living. Methods: Tibiofemoral kinematics and muscle synergy patterns were examined during level walking, downhill walking, and stair descent in eight self-reported unstable knees after TKA (3M:5F, 68.9 ± 8.3 years, body mass index [BMI] 26.1 ± 3.2 kg/m2, 31.9 ± 20.4 months postoperatively), and compared against 10 stable TKA knees (7M:3F, 62.6 ± 6.8 years, 33.9 ± 8.5 months postoperatively, BMI 29.4 ± 4.8 kg/m2). For each knee joint, clinical assessments of postoperative outcome were performed, while joint kinematics were evaluated using moving video-fluoroscopy, and muscle synergy patterns were recorded using electromyography. Results: Our results reveal that average condylar A-P translations, rotations, as well as their ranges of motion were comparable between stable and unstable groups. However, the unstable group exhibited more heterogeneous muscle synergy patterns and prolonged activation of knee flexors compared to the stable group. In addition, subjects who reported instability events during measurement showed distinct, subject-specific tibiofemoral kinematic patterns in the early/mid-swing phase of gait. Conclusions: Our findings suggest that accurate movement analysis is sensitive for detecting acute instability events, but might be less robust in identifying general joint instability. Conversely, muscle synergy patterns seem to be able to identify muscular adaptation associated with underlying chronic knee instability. Funding: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Editor's evaluation This paper presents a new method for evaluating joint instability at the knee after total knee replacement. The work is a valuable contribution that is based on solid evidence. The results should be of particular interest to those who study this important clinical problem. https://doi.org/10.7554/eLife.85136.sa0 Decision letter Reviews on Sciety eLife's review process Introduction Postoperative knee instability is one of the major reasons accounting for unsatisfactory outcomes, as well as a major failure mechanism leading to revision surgery after primary total knee arthroplasty (TKA). However, postoperative knee instability is not well defined clinically, and the boundaries between stable and unstable TKA knees are still poorly understood. This lack of understanding is likely due to the multitude of factors that are associated with knee instability, including inadequate soft-tissue balancing (Hosseini Nasab et al., 2019; Song et al., 2014), loss of ligamentous integrity (Nagle and Glynn, 2020), and improper component sizing (Nagle and Glynn, 2020; Parratte and Pagnano, 2008). Clinical assessment of joint stability relies on passive laxity examinations and patient-reported outcome measures (PROMs). Manual stress tests, including the anterior/posterior drawer, Lachman, and varus/valgus tests, as well as questionnaires such as the Knee injury and Osteoarthritis Outcome Score (KOOS) (Roos et al., 1998), Oxford Knee Score (OKS) (Dawson et al., 1998), University of California and Los Angeles (UCLA) Activity Scale (Zahiri et al., 1998), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (Bellamy et al., 1988) are widely used in clinical practice to assess knee instability after TKA. However, such clinical assessments are highly subjective with large inter-rater variability (Mears et al., 2022). With the goal to objectively investigate knee instability, methods for quantifying passive knee laxity such as the KT-1000/2000 (White et al., 1991; Ishii et al., 2005), Telos (Murer et al., 2021; Moser et al., 2022; Jung et al., 2006), Rotometer (Moewis et al., 2016; Lorbach et al., 2012), and Rolimeter (Schuster et al., 2011) devices, all generally combined with stress radiography, have been presented. Studies using these techniques have demonstrated that passive knee laxity plays a key role for functional outcomes and patient satisfaction after TKA (Oh et al., 2015; Jones et al., 2006). Nevertheless, it remains unclear whether self-reported instability after TKA is reflected in implant kinematics in vivo during functional activities of daily living. Specifically, both downhill walking and stair descent are considered as challenging tasks for subjects with knee pathologies (Stacoff et al., 2005; Simon et al., 2018), and could therefore present relevant activities for provoking feelings of instability. As the primary actuators of the locomotion system, muscles play a critical role in guiding motor functionality as well as supporting stability of the knee joint. Muscular deficits are often observed after TKA and closely correlate with physical impairment and limitations in daily activities (Berman et al., 1991; Walsh et al., 1998). Well-coordinated muscular activity is thought to be necessary for normal gait patterns (Berman et al., 1991). Here, adaptation of muscle recruitment patterns in the early postoperative phase, where increased knee extensor (quadriceps) and flexor (hamstrings) co-activation has generally been observed, is thought to enhance knee stability (Lundberg et al., 2016; Benedetti et al., 2003). However, whether such muscular adaptation is temporary and can be reversed in the long term after TKA remains controversially discussed (Benedetti et al., 2003; Thomas et al., 2014). Moreover, it remains unknown whether such adaptive strategies persist in unstable knees, or whether different lower limb muscle synergy patterns develop to compensate for deficits in knee stability. While the accurate assessment of tibiofemoral kinematics during functional activities is challenging, the recent development of dynamic video-fluoroscopy systems now provides access to implant kinematics with a high level of accuracy and without soft-tissue artefact throughout consecutive cycles of gait activities (Taylor et al., 2017; Schütz et al., 2019b; Schütz et al., 2019a; List et al., 2020). Such systems have recently allowed investigations into the impact of activity (Schütz et al., 2019a) and implant geometry (Schütz et al., 2019b; List et al., 2020) on tibiofemoral kinematics during functional activities such as level walking, downhill walking, and stair descent, and can be combined with electromyography (EMG) to assess muscle activation synergies and its role on modulating joint kinematics (Benedetti et al., 2003; Taylor et al., 2017; Ardestani et al., 2017). As such, the application of these approaches to subjects with stable and unstable knees after TKA could establish whether compensation mechanisms continue to occur, but also elucidate the role of neuromuscular activation and coordination on kinematic adaptations in the joint. To understand tibiofemoral kinematics in unstable TKA knees and its interaction with muscle activation strategies, the objective of this study was to investigate in vivo tibiofemoral implant kinematics and muscle synergy patterns in subjects with stable and self-reported unstable knees after TKA during functional activities of daily living using dynamic video-fluoroscopy and EMG. Specifically, we aimed to establish whether unstable knees exhibit higher levels of relative tibiofemoral motion and distinct muscle synergy patterns/strategies than their stable counterparts. Methods Study cohorts In total, 17 subjects (age ≥45 years, pain VAS ≤3) with 18 replaced knees implanted with Persona cruciate retaining (CR) TKA components and an ultra-congruent (UC) inlay (Zimmer Biomet, Warsaw, IN, USA) were recruited at least 1 year postoperatively. Both cruciate ligaments were sacrificed in all TKA knees. Of the 18, 8 TKA knees (3M:5F, 68.9 ± 8.3 years, 31.9 ± 20.4 months postoperatively, body mass index [BMI] 26.1 ± 3.2 kg/m2) were recruited from subjects reporting episodes of buckling, shifting, or giving away of the operated knee during daily activities in the 3 months prior to recruitment, with or without clinical signs of instability (unstable cohort). Ten TKA knees were recruited into the stable group (7M:3F, 62.6 ± 6.8 years, 33.9 ± 8.5 months postoperatively, BMI 29.4 ± 4.8 kg/m2) from subjects with no sensation of instability in the operated knee in the same 3-month period prior to recruitment. Subjects with significant problems of the lower extremities other than knee instability were excluded from participation in this study, as well as those presenting low back pain, neurological problems, patellofemoral symptoms, aseptic loosening, collateral ligament reconstruction, or an inability to perform the motion tasks, understand and/or sign the informed consent form. The project was approved by the Zürich cantonal ethics committee (BASEC no. 2019-01242) and all subjects provided their written informed consent prior to participation. Clinical assessment For each subject, clinical assessment of postoperative outcome was performed at the Schulthess Clinic Zürich, including manual passive laxity tests (anterior/posterior drawer and Lachmann, varus/valgus stress, and sagittal passive range of motion [RoM]), as well as PROMs (OKS, COMI-Knee, EQ-5D-5L, and UCLA activity score). Experimental procedure Level gait (straight ahead on a level floor), downhill walking (10° inclined slope), and stair descent (three 18 cm steps) were radiographically imaged at 30 Hz using the single plane ETH Moving Fluoroscope (List et al., 2017), which allowed in vivo tibiofemoral kinematics to be captured throughout complete cycles of each activity. Measurement protocols for the three activities have been described previously (Schütz et al., 2019a; List et al., 2020), but are briefly described here: Prior to each motion task, trials without fluoroscopic imaging were performed until the subject felt comfortable walking with the Moving Fluoroscope. For all activities, three to five valid cycles (heel-strike to heel-strike for gait activities) were measured. Heel-strike detection was performed using eight force plates (Kistler AG, Winterthur, Switzerland, 2000 Hz, force threshold: 25 N) or heel marker trajectories (Vicon MX system; Oxford Metrics Group, Oxford, UK; 200 Hz) where no force plates were available. Muscular activations were recorded using a wireless 16-channel surface EMG system (Trigno, Delsys, USA) throughout all activities. EMG electrodes were placed on eight muscles of the TKA limb: rectus femoris, vastus medialis, vastus lateralis, semitendinosus, biceps femoris, tibialis anterior, gastrocnemius medialis, and gastrocnemius lateralis. All measurement systems were temporally synchronized. For confirmation of previous clinical assessments, subjects were asked to report any feelings of instability on a four-point scale after each activity. Data processing Fluoroscopic images were distortion corrected (Foresti, 2009) before 2D → 3D registration was performed to determine the 3D poses of the implant components for each frame of the activity cycles using an in-house registration software (Burckhardt et al., 2005) (registration errors: <1° for all rotations, <1 mm for in-plane, and <3 mm for out of plane translations; List et al., 2017; Foresti, 2009). To describe relative tibiofemoral rotations, the joint coordinate system approach reported by Grood and Suntay, 1983 was used based on the local coordinate systems of the respective implant components. Tibiofemoral condylar A-P translations were defined based on the movement of the weighted mean location of the 10 nearest points on each condyle relative to a plane on the tibial plateau (Schütz et al., 2019a; List et al., 2020). Kinematic parameters including tibiofemoral A-P translations, flexion/extension, ab/adduction, and internal/external rotation angles during all gait activities, were interpolated to 101 data points per cycle. Condylar A-P translations were presented relative to the corresponding medial condyle position at the initial heel-strike of each trial. For each task, the RoM of all kinematic parameters was determined and separated into stance and swing phases. The intercondylar A-P RoM (lateral RoM − medial RoM) was then used to evaluate the transverse plane pivot pattern. EMG data were processed in R (version 4.2.0, R Foundation for Statistical Computing, Vienna, Austria) using package ‘musclesyneRgies v1.2.5’ (Santuz, 2022). All EMG signals were filtered (high-pass, cut-off frequency 50 Hz, fourth order; full wave rectified; low-pass, cut-off frequency 20 Hz, fourth order), amplitude normalized to the maximum value in each subject activity (Santuz et al., 2017), and time normalized to 200 data points, assigning 100 points to the stance and 100 to the swing phases (Santuz et al., 2018b). This time-normalization approach was chosen to ensure that the results could be interpreted independently of the absolute duration of gait events. Muscle synergy weights (time-independent coefficients), as well as the corresponding activation patterns (time-dependent coefficients), were extracted using a non-negative matrix factorization algorithm and subsequently functionally classified using k-mean clustering to evaluate the consistency of muscle synergies across each group (stable vs unstable) and activity (total of six classifications). Here, the number of classified muscle synergies in each group was imposed based on the average number of muscle synergies extracted per activity (4 for level gait and downhill walking, 3 for stair descent). The full width at half maximum (FWHM) and centre of activity (CoA) of each classified synergy activation pattern were further evaluated and compared between the two groups. The centre of activity, employed to estimate the timing of main activation, was calculated as the angle of the vector in polar coordinates that points to the centre of mass of the circular distribution defined between 0° and 360° or, in other words, between one touchdown and the next (Cappellini et al., 2016). Statistics Statistical analysis was performed using MATLAB (R2022a, MathWorks, Natick, MA, USA) and R (version 4.2.0). Two sample t-tests were conducted to compare differences in kinematic parameters using Bonferroni correction to account for possible interdependencies (tibiofemoral A-P translation RoMs, rotation RoMs), as well as in FWHM and CoA of corresponding classified activation patterns between groups. Non-parametric statistics using the Chi-squared test were performed to assess differences between the two groups in sex ratio, as well as in passive hyperextension, drawer tests, and varus/valgus stress tests. One-dimensional statistical parametric mapping (Pataky et al., 2016) was used to test the effects of knee instability on all kinematic parameters over the time series of a gait cycle. One-way analyses of variance (ANOVAs) were used to examine the effects of knee instability on the muscle synergy weights that demonstrate significant differences in FWHM/CoA of corresponding activation patterns between the groups. For any parameters that exhibit statistical significance between the two groups, corresponding Cohen’s d effect size (ES) was determined. Statistical significance was set to p < 0.05. Results Clinical assessment Passive clinical examination revealed that one stable knee and all unstable knees showed signs of mild hyperextension (Table 1). One stable knee and five out of eight unstable knees exhibited increased passive sagittal and coronal laxity. No other differences in the clinical examination were observed between the two groups. Inferior OKS and COMI-Knee scores were observed in the unstable knees, even though comparable UCLA activity and EQ-VAS scores were observed between the two groups. Table 1 Clinical assessment data of the stable and unstable groups shown as mean ± standard deviation of each parameter. BMI: body mass index; PTS: posterior tibial slope; RoM: range of motion; OKS: Oxford Knee Score; COMI-Knee: Core Outcome Measures Index-Knee; EQ-VAS: EQ-Visual Analogue Scales. Bold values indicate a significant difference. Baseline dataStable (N = 10)Unstable (N = 8)pSex ratio7M:3F3M:5F0.168Age [years]62.6 ± 6.868.9 ± 8.30.096BMI [kg/m2]29.4 ± 4.826.1 ± 3.20.113Time post-op [months]33.9 ± 8.531.9 ± 20.40.779PTS [°]82.0 ± 2.482.3 ± 3.00.863Inlay thickness [mm]11.3 ± 1.011.8 ± 1.70.511Knee flexion RoM [°]125.0 ± 7.8126.3 ± 6.40.720Hyperextension1/108/8<0.01Drawer tests1/105/80.019Varus/valgus stress tests1/105/80.019UCLA activity score8.3 ± 1.37.9 ± 1.10.465OKS46.0 ± 2.042.9 ± 3.80.040COMI-Knee0.2 ± 0.60.9 ± 0.80.044EQ-VAS84.5 ± 13.481.3 ± 17.10.660 A-P translations Video-fluoroscopic analysis of the functional kinematics revealed no significant differences were found in the relative A-P positions of the medial and lateral condyles at heel-strike between subjects of the stable and unstable groups (Supplementary file 1). Moreover, comparable mean A-P translations, A-P RoMs and pivot patterns were found between groups for the medial and lateral condyles throughout the stance and swing phases of all activities (Figure 1 and Table 2). For level and downhill walking, variability was generally higher in unstable TKA knees than in their stable counterparts. Interestingly, however, unstable knees exhibited less variability in medial condylar A-P translation during late-stance and early-swing phases (≈60–75% gait cycle) compared to stable knees. Figure 1 Download asset Open asset Tibiofemoral A-P translations in stable and unstable total knee arthroplasty (TKA) knees during level walking (left), downhill walking (middle), and stair descent (right). Means (solid lines) and standard deviation (shaded areas) of A-P translations in both groups are presented. Dotted colour lines indicate the mean toe-offs for the stable and unstable groups. Table 2 Mean ± standard deviation of the anterior-posterior(A-P) tibiofemoral positions for the medial and lateral condyles, flexion/extension (Flex/ex), adduction/abduction (Ab/ad), and internal/external (Int/ext) rotation angles in stable and unstable groups during all activities. A-P translation RoM [mm]Stance phaseSwing phaseMedialLateralDiffMedialLateralDiffLevel walkingStable5.4 ± 1.45.1 ± 1.0−0.3 ± 2.27.0 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± No significant differences in knee were observed between the two groups during the stance or swing phase for all tasks (Figure 2). the range of during the stance phase of downhill walking exhibited a significant between the cohorts (unstable ± stable ± p < Table Figure 2 Download asset Open asset Tibiofemoral throughout a gait in stable and unstable total knee arthroplasty (TKA) knees during level walking (left), downhill walking (middle), and stair descent (right). Means (solid lines) and standard (shaded areas) of both groups are presented. Dotted lines indicate the mean toe-offs for each group. Table 3 Mean ± standard deviation of knee range of flexion/extension and internal/external for the stance and swing phases of level walking, downhill walking, and stair significant was observed between stable and unstable groups in during downhill walking RoM phaseSwing ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± during activity the unstable three subjects reported the of joint instability while the activities. Interestingly, all three subjects reported instability during the more challenging activities of downhill walking and stair descent, where kinematic were (Figure Figure 3 Download asset Open asset Mean and standard across subjects of the tibiofemoral A-P translations in the stable and unstable groups without reported instability during the activities. In addition, mean and standard across trials of three from the unstable group who reported instability during the activities are shown in colour lines indicate the mean toe-offs for the stable and unstable groups, as well as for each unstable total knee arthroplasty (TKA) knee with reporting instability. Muscle synergy analysis In a comparable number of muscle synergies were extracted between stable and unstable knees during level walking (stable ± vs unstable ± downhill walking ± vs ± and stair descent ± vs 3.2 ± these number of the number of classified synergies was set to for level walking and downhill walking, and 3 for stair descent (Figure The of muscle synergies to total muscle synergies was increased from level gait to downhill walking in the stable group vs but from to in the unstable group. The were lower (stable vs unstable in both groups during stair level and downhill walking, each classified synergy was by the knee extensor or knee flexor (hamstrings) muscle groups, distinct synergies were the stable knees in a comparable between level walking and of subjects exhibited this and downhill walking and However, these synergies were less observed in unstable knees during downhill walking and compared to level walking and as well as to the stable knees during downhill stair descent, three by the knee and knee or could be in both the stable and unstable but were more found in the stable knees and than their unstable and Figure Download asset Open asset muscle synergies in both stable and unstable total knee arthroplasty (TKA) knees during level walking, downhill walking, and stair Muscle synergy as well as (solid lines) and standard (shaded areas) of the corresponding activation patterns are presented for each activity. rectus femoris, vastus medialis, vastus lateralis, tibialis anterior, medial lateral gastrocnemius medialis, gastrocnemius lateralis. Muscle synergies exhibited activation Knee extensor muscles were during early stance or throughout stance walking and stair while the to the stance throughout stance and swing phases (Figure of the knee flexor muscles were during stance as well as at As the exhibit a pattern of activation, at early stance and early swing during level walking, while presenting a more activation during downhill walking and stair The FWHM of the classified synergy activation patterns of the and knee flexors were higher in the unstable than the stable knees = p = during stair descent (Table results were found in the FWHM of the knee extensor and activations between the two groups during all activities. No differences were observed in the CoA of any synergies the activation pattern by during level walking = p < (Table but the corresponding classified muscle synergy was found in three out of the eight unstable knees. The showed muscle weights between the groups during level walking and stair descent (Supplementary file 2). Table Mean ± standard deviation of full width at half maximum (FWHM) of the activation patterns corresponding to knee and knee flexor muscle groups during level walking, downhill walking, and stair differences were observed between stable and unstable knees during stair descent in and knee flexor muscles with an effect size of classified synergy corresponding to and knee flexor muscles was observed in a number of unstable knees ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Table Mean ± standard deviation of centre of activity (CoA) of the activation patterns corresponding to knee and knee flexor muscle groups during level walking, downhill walking, and stair significant was observed between stable and unstable knees during stair descent in muscles with an effect size of classified synergy corresponding to and knee flexor muscles was observed in a number of unstable knees ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Discussion Knee instability is one of the reasons for unsatisfactory outcomes after accounting for to of and Pagnano, et al., 2017). However, the relationships between self-reported assessment of instability and knee functionality in daily living remain unclear. moving video-fluoroscopy and we compared kinematic parameters of knee joint as well as muscle synergy between subjects who at the stability of their and those who were with its functional Our results indicate that kinematic including A-P translations and knee rotations, as well as their RoMs during functional activities, were generally comparable between stable and unstable TKA knees. However, increased in muscle synergy patterns between subjects and across activities, during challenging tasks such as stair descent, as well as prolonged activation of the classified knee flexor were observed in the unstable group. differences between groups plausibly reveal muscular adaptation strategies that develop as a compensation mechanism for feelings of joint instability and to possible unstable events. these in muscular strategies, however, specific of acute instability were still reported by subjects during the and analysis of their data revealed in kinematic patterns from those of both the stable and unstable groups. suggest that accurate movement analysis might be highly sensitive for detecting acute instability

Full text Figures and data Side by side Abstract Editor's evaluation Introduction Methods Results Discussion Data availability References Decision letter Author response Article and author information Metrics Abstract Background: Postoperative knee instability is one of the major reasons accounting for unsatisfactory outcomes, as well as a major failure mechanism leading to total knee arthroplasty (TKA) revision. Nevertheless, subjective knee instability is not well defined clinically, plausibly because the relationships between instability and implant kinematics during functional activities of daily living remain unclear. Although muscles play a critical role in supporting the dynamic stability of the knee joint, the influence of joint instability on muscle synergy patterns is poorly understood. Therefore, this study aimed to understand the impact of self-reported joint instability on tibiofemoral kinematics and muscle synergy patterns after TKA during functional gait activities of daily living. Methods: Tibiofemoral kinematics and muscle synergy patterns were examined during level walking, downhill walking, and stair descent in eight self-reported unstable knees after TKA (3M:5F, 68.9 ± 8.3 years, body mass index [BMI] 26.1 ± 3.2 kg/m2, 31.9 ± 20.4 months postoperatively), and compared against 10 stable TKA knees (7M:3F, 62.6 ± 6.8 years, 33.9 ± 8.5 months postoperatively, BMI 29.4 ± 4.8 kg/m2). For each knee joint, clinical assessments of postoperative outcome were performed, while joint kinematics were evaluated using moving video-fluoroscopy, and muscle synergy patterns were recorded using electromyography. Results: Our results reveal that average condylar A-P translations, rotations, as well as their ranges of motion were comparable between stable and unstable groups. However, the unstable group exhibited more heterogeneous muscle synergy patterns and prolonged activation of knee flexors compared to the stable group. In addition, subjects who reported instability events during measurement showed distinct, subject-specific tibiofemoral kinematic patterns in the early/mid-swing phase of gait. Conclusions: Our findings suggest that accurate movement analysis is sensitive for detecting acute instability events, but might be less robust in identifying general joint instability. Conversely, muscle synergy patterns seem to be able to identify muscular adaptation associated with underlying chronic knee instability. Funding: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Editor's evaluation This paper presents a new method for evaluating joint instability at the knee after total knee replacement. The work is a valuable contribution that is based on solid evidence. The results should be of particular interest to those who study this important clinical problem. https://doi.org/10.7554/eLife.85136.sa0 Decision letter Reviews on Sciety eLife's review process Introduction Postoperative knee instability is one of the major reasons accounting for unsatisfactory outcomes, as well as a major failure mechanism leading to revision surgery after primary total knee arthroplasty (TKA). However, postoperative knee instability is not well defined clinically, and the boundaries between stable and unstable TKA knees are still poorly understood. This lack of understanding is likely due to the multitude of factors that are associated with knee instability, including inadequate soft-tissue balancing (Hosseini Nasab et al., 2019; Song et al., 2014), loss of ligamentous integrity (Nagle and Glynn, 2020), and improper component sizing (Nagle and Glynn, 2020; Parratte and Pagnano, 2008). Clinical assessment of joint stability relies on passive laxity examinations and patient-reported outcome measures (PROMs). Manual stress tests, including the anterior/posterior drawer, Lachman, and varus/valgus tests, as well as questionnaires such as the Knee injury and Osteoarthritis Outcome Score (KOOS) (Roos et al., 1998), Oxford Knee Score (OKS) (Dawson et al., 1998), University of California and Los Angeles (UCLA) Activity Scale (Zahiri et al., 1998), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (Bellamy et al., 1988) are widely used in clinical practice to assess knee instability after TKA. However, such clinical assessments are highly subjective with large inter-rater variability (Mears et al., 2022). With the goal to objectively investigate knee instability, methods for quantifying passive knee laxity such as the KT-1000/2000 (White et al., 1991; Ishii et al., 2005), Telos (Murer et al., 2021; Moser et al., 2022; Jung et al., 2006), Rotometer (Moewis et al., 2016; Lorbach et al., 2012), and Rolimeter (Schuster et al., 2011) devices, all generally combined with stress radiography, have been presented. Studies using these techniques have demonstrated that passive knee laxity plays a key role for functional outcomes and patient satisfaction after TKA (Oh et al., 2015; Jones et al., 2006). Nevertheless, it remains unclear whether self-reported instability after TKA is reflected in implant kinematics in vivo during functional activities of daily living. Specifically, both downhill walking and stair descent are considered as challenging tasks for subjects with knee pathologies (Stacoff et al., 2005; Simon et al., 2018), and could therefore present relevant activities for provoking feelings of instability. As the primary actuators of the locomotion system, muscles play a critical role in guiding motor functionality as well as supporting stability of the knee joint. Muscular deficits are often observed after TKA and closely correlate with physical impairment and limitations in daily activities (Berman et al., 1991; Walsh et al., 1998). Well-coordinated muscular activity is thought to be necessary for normal gait patterns (Berman et al., 1991). Here, adaptation of muscle recruitment patterns in the early postoperative phase, where increased knee extensor (quadriceps) and flexor (hamstrings) co-activation has generally been observed, is thought to enhance knee stability (Lundberg et al., 2016; Benedetti et al., 2003). However, whether such muscular adaptation is temporary and can be reversed in the long term after TKA remains controversially discussed (Benedetti et al., 2003; Thomas et al., 2014). Moreover, it remains unknown whether such adaptive strategies persist in unstable knees, or whether different lower limb muscle synergy patterns develop to compensate for deficits in knee stability. While the accurate assessment of tibiofemoral kinematics during functional activities is challenging, the recent development of dynamic video-fluoroscopy systems now provides access to implant kinematics with a high level of accuracy and without soft-tissue artefact throughout consecutive cycles of gait activities (Taylor et al., 2017; Schütz et al., 2019b; Schütz et al., 2019a; List et al., 2020). Such systems have recently allowed investigations into the impact of activity (Schütz et al., 2019a) and implant geometry (Schütz et al., 2019b; List et al., 2020) on tibiofemoral kinematics during functional activities such as level walking, downhill walking, and stair descent, and can be combined with electromyography (EMG) to assess muscle activation synergies and its role on modulating joint kinematics (Benedetti et al., 2003; Taylor et al., 2017; Ardestani et al., 2017). As such, the application of these approaches to subjects with stable and unstable knees after TKA could establish whether compensation mechanisms continue to occur, but also elucidate the role of neuromuscular activation and coordination on kinematic adaptations in the joint. To understand tibiofemoral kinematics in unstable TKA knees and its interaction with muscle activation strategies, the objective of this study was to investigate in vivo tibiofemoral implant kinematics and muscle synergy patterns in subjects with stable and self-reported unstable knees after TKA during functional activities of daily living using dynamic video-fluoroscopy and EMG. Specifically, we aimed to establish whether unstable knees exhibit higher levels of relative tibiofemoral motion and distinct muscle synergy patterns/strategies than their stable counterparts. Methods Study cohorts In total, 17 subjects (age ≥45 years, pain VAS ≤3) with 18 replaced knees implanted with Persona cruciate retaining (CR) TKA components and an ultra-congruent (UC) inlay (Zimmer Biomet, Warsaw, IN, USA) were recruited at least 1 year postoperatively. Both cruciate ligaments were sacrificed in all TKA knees. Of the 18, 8 TKA knees (3M:5F, 68.9 ± 8.3 years, 31.9 ± 20.4 months postoperatively, body mass index [BMI] 26.1 ± 3.2 kg/m2) were recruited from subjects reporting episodes of buckling, shifting, or giving away of the operated knee during daily activities in the 3 months prior to recruitment, with or without clinical signs of instability (unstable cohort). Ten TKA knees were recruited into the stable group (7M:3F, 62.6 ± 6.8 years, 33.9 ± 8.5 months postoperatively, BMI 29.4 ± 4.8 kg/m2) from subjects with no sensation of instability in the operated knee in the same 3-month period prior to recruitment. Subjects with significant problems of the lower extremities other than knee instability were excluded from participation in this study, as well as those presenting low back pain, neurological problems, patellofemoral symptoms, aseptic loosening, collateral ligament reconstruction, or an inability to perform the motion tasks, understand and/or sign the informed consent form. The project was approved by the Zürich cantonal ethics committee (BASEC no. 2019-01242) and all subjects provided their written informed consent prior to participation. Clinical assessment For each subject, clinical assessment of postoperative outcome was performed at the Schulthess Clinic Zürich, including manual passive laxity tests (anterior/posterior drawer and Lachmann, varus/valgus stress, and sagittal passive range of motion [RoM]), as well as PROMs (OKS, COMI-Knee, EQ-5D-5L, and UCLA activity score). Experimental procedure Level gait (straight ahead on a level floor), downhill walking (10° inclined slope), and stair descent (three 18 cm steps) were radiographically imaged at 30 Hz using the single plane ETH Moving Fluoroscope (List et al., 2017), which allowed in vivo tibiofemoral kinematics to be captured throughout complete cycles of each activity. Measurement protocols for the three activities have been described previously (Schütz et al., 2019a; List et al., 2020), but are briefly described here: Prior to each motion task, trials without fluoroscopic imaging were performed until the subject felt comfortable walking with the Moving Fluoroscope. For all activities, three to five valid cycles (heel-strike to heel-strike for gait activities) were measured. Heel-strike detection was performed using eight force plates (Kistler AG, Winterthur, Switzerland, 2000 Hz, force threshold: 25 N) or heel marker trajectories (Vicon MX system; Oxford Metrics Group, Oxford, UK; 200 Hz) where no force plates were available. Muscular activations were recorded using a wireless 16-channel surface EMG system (Trigno, Delsys, USA) throughout all activities. EMG electrodes were placed on eight muscles of the TKA limb: rectus femoris, vastus medialis, vastus lateralis, semitendinosus, biceps femoris, tibialis anterior, gastrocnemius medialis, and gastrocnemius lateralis. All measurement systems were temporally synchronized. For confirmation of previous clinical assessments, subjects were asked to report any feelings of instability on a four-point scale after each activity. Data processing Fluoroscopic images were distortion corrected (Foresti, 2009) before 2D → 3D registration was performed to determine the 3D poses of the implant components for each frame of the activity cycles using an in-house registration software (Burckhardt et al., 2005) (registration errors: <1° for all rotations, <1 mm for in-plane, and <3 mm for out of plane translations; List et al., 2017; Foresti, 2009). To describe relative tibiofemoral rotations, the joint coordinate system approach reported by Grood and Suntay, 1983 was used based on the local coordinate systems of the respective implant components. Tibiofemoral condylar A-P translations were defined based on the movement of the weighted mean location of the 10 nearest points on each condyle relative to a plane on the tibial plateau (Schütz et al., 2019a; List et al., 2020). Kinematic parameters including tibiofemoral A-P translations, flexion/extension, ab/adduction, and internal/external rotation angles during all gait activities, were interpolated to 101 data points per cycle. Condylar A-P translations were presented relative to the corresponding medial condyle position at the initial heel-strike of each trial. For each task, the RoM of all kinematic parameters was determined and separated into stance and swing phases. The intercondylar A-P RoM (lateral RoM − medial RoM) was then used to evaluate the transverse plane pivot pattern. EMG data were processed in R (version 4.2.0, R Foundation for Statistical Computing, Vienna, Austria) using package 'musclesyneRgies v1.2.5' (Santuz, 2022). All EMG signals were filtered (high-pass, cut-off frequency 50 Hz, fourth order; full wave rectified; low-pass, cut-off frequency 20 Hz, fourth order), amplitude normalized to the maximum value in each subject activity (Santuz et al., 2017), and time normalized to 200 data points, assigning 100 points to the stance and 100 to the swing phases (Santuz et al., 2018b). This time-normalization approach was chosen to ensure that the results could be interpreted independently of the absolute duration of gait events. Muscle synergy weights (time-independent coefficients), as well as the corresponding activation patterns (time-dependent coefficients), were extracted using a non-negative matrix factorization algorithm and subsequently functionally classified using k-mean clustering to evaluate the consistency of muscle synergies across each group (stable vs unstable) and activity (total of six classifications). Here, the number of classified muscle synergies in each group was imposed based on the average number of muscle synergies extracted per activity (4 for level gait and downhill walking, 3 for stair descent). The full width at half maximum (FWHM) and centre of activity (CoA) of each classified synergy activation pattern were further evaluated and compared between the two groups. The centre of activity, employed to estimate the timing of main activation, was calculated as the angle of the vector in polar coordinates that points to the centre of mass of the circular distribution defined between 0° and 360° or, in other words, between one touchdown and the next (Cappellini et al., 2016). Statistics Statistical analysis was performed using MATLAB (R2022a, MathWorks, Natick, MA, USA) and R (version 4.2.0). Two sample t-tests were conducted to compare differences in kinematic parameters using Bonferroni correction to account for possible interdependencies (tibiofemoral A-P translation RoMs, rotation RoMs), as well as in FWHM and CoA of corresponding classified activation patterns between groups. Non-parametric statistics using the Chi-squared test were performed to assess differences between the two groups in sex ratio, as well as in passive hyperextension, drawer tests, and varus/valgus stress tests. One-dimensional statistical parametric mapping (Pataky et al., 2016) was used to test the effects of knee instability on all kinematic parameters over the time series of a gait cycle. One-way analyses of variance (ANOVAs) were used to examine the effects of knee instability on the muscle synergy weights that demonstrate significant differences in FWHM/CoA of corresponding activation patterns between the groups. For any parameters that exhibit statistical significance between the two groups, corresponding Cohen's d effect size (ES) was determined. Statistical significance was set to p < 0.05. Results Clinical assessment Passive clinical examination revealed that one stable knee and all unstable knees showed signs of mild hyperextension (Table 1). One stable knee and five out of eight unstable knees exhibited increased passive sagittal and coronal laxity. No other differences in the clinical examination were observed between the two groups. Inferior OKS and COMI-Knee scores were observed in the unstable knees, even though comparable UCLA activity and EQ-VAS scores were observed between the two groups. Table 1 Clinical assessment data of the stable and unstable groups shown as mean ± standard deviation of each parameter. BMI: body mass index; PTS: posterior tibial slope; RoM: range of motion; OKS: Oxford Knee Score; COMI-Knee: Core Outcome Measures Index-Knee; EQ-VAS: EQ-Visual Analogue Scales. Bold values indicate a significant difference. Baseline dataStable (N = 10)Unstable (N = 8)pSex ratio7M:3F3M:5F0.168Age [years]62.6 ± 6.868.9 ± 8.30.096BMI [kg/m2]29.4 ± 4.826.1 ± 3.20.113Time post-op [months]33.9 ± 8.531.9 ± 20.40.779PTS [°]82.0 ± 2.482.3 ± 3.00.863Inlay thickness [mm]11.3 ± 1.011.8 ± 1.70.511Knee flexion RoM [°]125.0 ± 7.8126.3 ± 6.40.720Hyperextension1/108/8<0.01Drawer tests1/105/80.019Varus/valgus stress tests1/105/80.019UCLA activity score8.3 ± 1.37.9 ± 1.10.465OKS46.0 ± 2.042.9 ± 3.80.040COMI-Knee0.2 ± 0.60.9 ± 0.80.044EQ-VAS84.5 ± 13.481.3 ± 17.10.660 A-P translations Video-fluoroscopic analysis of the functional kinematics revealed no significant differences were found in the relative A-P positions of the medial and lateral condyles at heel-strike between subjects of the stable and unstable groups (Supplementary file 1). Moreover, comparable mean A-P translations, A-P RoMs and pivot patterns were found between groups for the medial and lateral condyles throughout the stance and swing phases of all activities (Figure 1 and Table 2). For level and downhill walking, variability was generally higher in unstable TKA knees than in their stable counterparts. Interestingly, however, unstable knees exhibited less variability in medial condylar A-P translation during late-stance and early-swing phases (≈60–75% gait cycle) compared to stable knees. Figure 1 Download asset Open asset Tibiofemoral A-P translations in stable and unstable total knee arthroplasty (TKA) knees during level walking (left), downhill walking (middle), and stair descent (right). Means (solid lines) and standard deviation (shaded areas) of A-P translations in both groups are presented. Dotted colour lines indicate the mean toe-offs for the stable and unstable groups. Table 2 Mean ± standard deviation of the anterior-posterior(A-P) tibiofemoral positions for the medial and lateral condyles, flexion/extension (Flex/ex), adduction/abduction (Ab/ad), and internal/external (Int/ext) rotation angles in stable and unstable groups during all activities. A-P translation RoM [mm]Stance phaseSwing phaseMedialLateralDiffMedialLateralDiffLevel walkingStable5.4 ± 1.45.1 ± 1.0−0.3 ± 2.27.0 ± 2.55.7 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± No significant differences in knee were observed between the two groups during the stance or swing phase for all tasks (Figure 2). the range of during the stance phase of downhill walking exhibited a significant between the cohorts (unstable ± stable ± p < Table Figure 2 Download asset Open asset Tibiofemoral throughout a gait in stable and unstable total knee arthroplasty (TKA) knees during level walking (left), downhill walking (middle), and stair descent (right). Means (solid lines) and standard (shaded areas) of both groups are presented. Dotted lines indicate the mean toe-offs for each group. Table 3 Mean ± standard deviation of knee range of flexion/extension and internal/external for the stance and swing phases of level walking, downhill walking, and stair significant was observed between stable and unstable groups in during downhill walking RoM phaseSwing ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± during activity the unstable three subjects reported the of joint instability while the activities. Interestingly, all three subjects reported instability during the more challenging activities of downhill walking and stair descent, where kinematic were (Figure Figure 3 Download asset Open asset Mean and standard across subjects of the tibiofemoral A-P translations in the stable and unstable groups without reported instability during the activities. In addition, mean and standard across trials of three from the unstable group who reported instability during the activities are shown in colour lines indicate the mean toe-offs for the stable and unstable groups, as well as for each unstable total knee arthroplasty (TKA) knee with reporting instability. Muscle synergy analysis In a comparable number of muscle synergies were extracted between stable and unstable knees during level walking (stable ± vs unstable ± downhill walking ± vs ± and stair descent ± vs 3.2 ± these number of the number of classified synergies was set to for level walking and downhill walking, and 3 for stair descent (Figure The of muscle synergies to total muscle synergies was increased from level gait to downhill walking in the stable group vs but from to in the unstable group. The were lower (stable vs unstable in both groups during stair level and downhill walking, each classified synergy was by the knee extensor or knee flexor (hamstrings) muscle groups, distinct synergies were the stable knees in a comparable between level walking and of subjects exhibited this and downhill walking and However, these synergies were less observed in unstable knees during downhill walking and compared to level walking and as well as to the stable knees during downhill stair descent, three by the knee and knee or could be in both the stable and unstable but were more found in the stable knees and than their unstable and Figure Download asset Open asset muscle synergies in both stable and unstable total knee arthroplasty (TKA) knees during level walking, downhill walking, and stair Muscle synergy as well as (solid lines) and standard (shaded areas) of the corresponding activation patterns are presented for each activity. rectus femoris, vastus medialis, vastus lateralis, tibialis anterior, medial lateral gastrocnemius medialis, gastrocnemius lateralis. Muscle synergies exhibited activation Knee extensor muscles were during early stance or throughout stance walking and stair while the to the stance throughout stance and swing phases (Figure of the knee flexor muscles were during stance as well as at As the exhibit a pattern of activation, at early stance and early swing during level walking, while presenting a more activation during downhill walking and stair The FWHM of the classified synergy activation patterns of the and knee flexors were higher in the unstable than the stable knees = p = during stair descent (Table results were found in the FWHM of the knee extensor and activations between the two groups during all activities. No differences were observed in the CoA of any synergies the activation pattern by during level walking = p < (Table but the corresponding classified muscle synergy was found in three out of the eight unstable knees. The showed muscle weights between the groups during level walking and stair descent (Supplementary file 2). Table Mean ± standard deviation of full width at half maximum (FWHM) of the activation patterns corresponding to knee and knee flexor muscle groups during level walking, downhill walking, and stair differences were observed between stable and unstable knees during stair descent in and knee flexor muscles with an effect size of classified synergy corresponding to and knee flexor muscles was observed in a number of unstable knees ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Table Mean ± standard deviation of centre of activity (CoA) of the activation patterns corresponding to knee and knee flexor muscle groups during level walking, downhill walking, and stair significant was observed between stable and unstable knees during stair descent in muscles with an effect size of classified synergy corresponding to and knee flexor muscles was observed in a number of unstable knees ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Discussion Knee instability is one of the reasons for unsatisfactory outcomes after accounting for to of and Pagnano, et al., 2017). However, the relationships between self-reported assessment of instability and knee functionality in daily living remain unclear. moving video-fluoroscopy and we compared kinematic parameters of knee joint as well as muscle synergy between subjects who at the stability of their and those who were with its functional Our results indicate that kinematic including A-P translations and knee rotations, as well as their RoMs during functional activities, were generally comparable between stable and unstable TKA knees. However, increased in muscle synergy patterns between subjects and across activities, during challenging tasks such as stair descent, as well as prolonged activation of the classified knee flexor were observed in the unstable group. differences between groups plausibly reveal muscular adaptation strategies that develop as a compensation mechanism for feelings of joint instability and to possible unstable events. these in muscular strategies, however, specific of acute instability were still reported by subjects during the and analysis of their data revealed in kinematic patterns from those of both the stable and unstable groups. suggest that accurate movement analysis might be highly sensitive for detecting acute instability

(1) Background: Squatting is one of the common closed-kinetic chain (CKC) exercises for knee rehabilitation. Some patients cannot perform squatting exercises on land occasionally due to knee pain. Several studies had suggested that lower limb muscle activities are lower in water than on land while performing CKC exercises. The purpose of this study is to investigate the surface electromyography (sEMG) activities of Rectus femoris (RF) and Biceps femoris (BF) muscles when doing a squatting exercise in water and on land. (2) Methods: This was a cross-sectional experimental study. A total of 20 healthy participants (10 males, 10 females) were recruited by convenience sampling. The sEMG of RF and BF muscles in water and on land were collected and the knee motions were videotaped. Participants were instructed to perform closed kinetic-chain back squatting exercises at a specific speed (30 beats per minute) in water and on land at angular speed of 45°/s. Eight repetitions of the squatting exercise (0–90° knee flexion) were performed. The mean percentage maximal voluntary contraction (%MVC) between two muscles was compared in two conditions. The %MVC of RF and BF muscles at different specific knee flexion angles (30°, 60° and 90° knee flexion) was also identified. (3) Result: Muscle activities of RF (p = 0.01) and BF (p < 0.01) muscles were significantly lower in water than on land. The %MVC of RF and BF muscles was found to be 15.01% and 10.68% lower in water than on land respectively. For different knee angle phases, the differences in %MVC between land and water had significant difference for both RF muscles and BF muscles. (4) Conclusion: This study found a difference of mean percentage MVC of RF and BF muscles between land and water in different phases of squatting. The water medium reduced the two muscles’ activities to a similar extent. The result showed that the aquatic environment allows an individual to perform squatting with less muscle activation which may serve as an alternative knee exercise option for patients who encounter difficulty in land squatting due to lower limb muscle weakness or a high level of knee pain.

The effect of hip abductor strengthening exercises on lower limb strength asymmetry and balance in women with multiple sclerosis: A randomized controlled clinical trial

IntroductionReduced muscle strength is a high risk factor for type 2 diabetes mellitus, and this association is especially strong in non-obese male individuals. However, it remains unclear how reduced muscle strength affects susceptibility to diabetes. We have examined whether lower limb muscle strength is associated with insulin resistance in non-obese Japanese male subjects.MethodsMeasurements from 64 non-diabetic, non-obese, middle-aged Japanese men were analyzed. Insulin sensitivity in muscle was measured using the hyperinsulinemic-euglycemic clamp. Isometric muscle strength of the knee extensor and flexor muscles was evaluated using a dynameter.ResultsLower muscle strength of knee flexors, but not knee extensors, was associated with impaired muscle insulin sensitivity (knee flexor muscles: low, medium, and high strength was 6.6 ± 2.2, 7.3 ± 2.0, and 8.8 ± 2.2 mg/kg per minute, respectively, p for trend < 0.05; knee extensor muscles: low, medium, and high strength was 7.3 ± 2.5, 7.5 ± 2.2, and 7.8 ± 2.3 mg/kg per minute, respectively, p for trend = 0.73). Knee flexor muscle strength was also identified as an independent determinant of insulin sensitivity in the multiple regression analysis (β = 0.274, p = 0.036).ConclusionsDiminished strength of knee flexor muscles, but not knee extensor muscles, was associated with muscle insulin sensitivity in non-diabetic, non-obese Japanese male subjects.

본 논문은 만성 뇌졸중 환자의 트레드밀 경사도 훈련이 하지 근육의 활성도에 미치는 영향을 알아보기 위한것으로 32명의 대상자를 무작위로 대조군인 <TEX>$0^{\circ}$</TEX>훈련군 10명과 실험군인 <TEX>$5^{\circ}$</TEX>훈련군 10명과 <TEX>$10^{\circ}$</TEX>훈련군 12명으로 나누어 실험하였다. 6주간의 훈련 후 하지 근육 중 넙다리곧은근, 넙다리두갈래근, 앞정강근, 장딴지근의 활성도 정도를 근전도를 통해 검사하였다. 연구의 결과 넙다리곧은근과 장딴지근은 각 그룹에서 각각 의미있는 변화를 보였지만 넙다리두갈래근과 앞정강근은 실험군에서만 의미있는 변화를 보였다. 또한 각 그룹간 비교에서는 넙다리곧은근이 대조군과 <TEX>$5^{\circ}$</TEX>훈련군 사이에서 앞정강근이 대조군과 <TEX>$10^{\circ}$</TEX>훈련군 사이에서 의미있는 변화를 보였다. 따라서 트레드밀 경사도 보행 훈련이 하지 근육의 활성화에 효과가 있음을 알 수 있다. The purpose of this study was to identify the effect of treadmill gradient training on lower limb muscle activity in chronic stroke patients. The subject were 32 stroke patients.. Subjects were randomly divided into three group which were control group(<TEX>$0^{\circ}$</TEX>treadmill training(n=10)) and experimental group(<TEX>$5^{\circ}$</TEX>treadmill training (n=10) and <TEX>$10^{\circ}$</TEX>treadmill training(n=12)). Three groups received treadmill gradient training for 30 minutes while 3 times per week for 6 weeks in addition to conventional physical therapy. Muscle strength was measured by EMG on rectus femoris, biceps femoris, tibialis anterior and gastrocnenius for muscle activities. In comparison of activity of rectus femoris and gastrocnemius between pre and post value, the activity of rectus femoris was significant in the experimental and control group(p<.05) and the activity of biceps femoris was significant in the <TEX>$5^{\circ}$</TEX>treadmill gait training group and <TEX>$10^{\circ}$</TEX>treadmill gait training group(p<.05). The activity of tibialis anterior was significant in the <TEX>$5^{\circ}$</TEX>treadmill gait training group and <TEX>$10^{\circ}$</TEX>treadmill gait training group(p<.05). In comparison of the difference of activity of rectus femoris among 3 groups, there was a significant difference between the <TEX>$5^{\circ}$</TEX>treadmill gait training group and control group(p<.05). and difference of activity of tibialis anterior was significant difference between the <TEX>$10^{\circ}$</TEX>treadmill gait training group and control group(p<.05). These findings suggest that <TEX>$5^{\circ}$</TEX>treadmill gait training group and <TEX>$10^{\circ}$</TEX>treadmill gait training group can be used to improve lower limb muscle activity in chronic stroke patient. In conclusion, these treadmill gradient training helped improving function of gait ability in chronic stroke patient.

Toward the definition of a minimum input model for an EMG analysis in clinics

Objectives: To investigate the influence of regular Tai Chi (TC) practice and jogging on muscle strength and endurance in the lower extremities of older people. Methods: Twenty one long term...

A great number of studies showed in the last years that static stretching performed immediately before athletic activity has negative effects on lower extremity performance during athletic activities like vertical jump and sprint. All of this research associated with static stretching evaluated performance in the agonist musculature. The co-activity of the antagonist muscles, on the other hand, is also important when an activity is performed or during joint stabilisation. Changes in the activity of the antagonist muscles, either decrease or increase during sports can influence the related athletic performance. There is limited number of published studies in the literature investigating the effects of stretching the antagonist muscles on agonist muscle activity during jump performance. Therefore, the aim of this study was to investigate the effects of static stretching of the muscles that acts as antagonists in relation to the more agonist muscles during jumping on biomechanical data, vertical jump height and electromyographic (EMG) activity of the agonist muscles during vertical jump performance. Eleven healthy elite female athletes (mean age, 23.0 ± 6.2 years; mean height, 176.2 ± 9.1 cm; mean body mass, 67.5 ± 12.4 kg) participated to this study. All of the subjects performed the protocols for stretching intervention, non-stretching (control) and static stretching, in a randomised order on different days within one week. Static stretching, which comprised four consecutive repetitions, was held for 30 seconds in the hip flexor, knee flexor and ankle dorsi-flexor muscles. To determine if stretching intervention of the antagonist muscles affects performance, subjects carried out a squat jump test before and immediately following the intervention. Vertical jump height, EMG activity of the hip extensor, knee extensor and ankle plantar-flexor muscles of both legs, joint flexion angle of the hip, knee and ankle as kinematic and power analysis as kinetic variable was tested during the squat jump. The EMG activity in total of 12 muscles from both legs was recorded from the following exact points; (a) at which each subject began the concentric phase of the jump, (b) between the start of jump and take-off, (c) at take-off, (d) between take-off and landing, (e) at landing where the fingers contacted the ground and (f) at the contact of heel with the ground. There were no significant EMG activity differences between the stretching and control intervention in the hip extensor, knee extensor and ankle plantar-flexor muscles of both legs at the measured six vertical jump phases (p > 0.05). Similarly, the hip, knee and ankle range of motion during the squat jump divided to ten timelines did not represent significant differences between the stretching and control group (p > 0.05). In contrast, according to the 2 × 2 repeated measures ANOVA model, the vertical jump height following the static stretching of the antagonist muscles showed a significant stretch type x time interaction (stretching group: before 161 ± 18 mm, after 167 ± 21 mm; control group: before 169 ± 20 mm, after 166 ± 19 mm; p = 0.019). Although the statistical significant difference for the vertical jump height following stretching, the 6 mm increase is not clinical meaningful. Therefore, according to the results of the present study it seems that static stretching of the antagonist muscles involved in the squat jump activity does not affect the squat jump performance evaluated with EMG activity, kinematic and kinetic analyses. Acknowledgement The authors would like to express appreciation for the support of the Department of the Scientific Research Projects of Uludag University (Project Number = HDP(T)−2016/13)

Introduction. Osteoporosis and osteopenia are related to changes in the quantity and quality of skeletal muscle and contribute to a decreased level of muscle strength. The purpose of this study was to evaluate the impact of Nordic walking training on muscle strength and the electromyographic (EMG) activity of the lower body in women with low bone mass. Material and methods. The participants of the study were 27 women with low bone mass. The sample was randomly divided into two groups: a control group and an experimental group. Women from the experimental group participated in 12 weeks of regular Nordic walking training. Functional strength was assessed with a 30-second chair stand test. The EMG activities of the gluteus maximus (GMax), rectus femoris (RF), biceps femoris (BF), soleus (SOL), and lumbar (LB) muscles were measured using a surface electromyogram. Results. Nordic walking training induced a significant increase in the functional strength (p = 0.006) of the lower body and activity of GMax (p = 0.013) and a decrease in body mass (p = 0.006) in women with reduced bone mass. There was no statistically significant increase in the EMG activities of the RF, BF, SOL, or LB muscles. The study did not indicate any significant changes in functional muscle strength, the EMG activity of the lower body, or anthropometry in women from the control group. Conclusions. Nordic walking training induces positive changes in lower body strength and the electromyographic activity of the gluteus maximus as well as a decrease in body mass in women with low bone mass.

The effects of grade and speed on leg muscle activations during walking

Introduction: Stroke reduces lower extremity muscle strength bilaterally, predominantly on the affected side. Stroke rehabilitation focuses on training the hemiparetic extremities, whereas functional activities require the recruitment of bilateral lower extremity muscles. Objectives: This research is aimed at studying the effectiveness of additional structured strength training of unaffected lower extremity (ULE) on balance and gait among acute poststroke individuals. Methods: This Nonrandomized Controlled Trial included 28 clinically stable acute poststroke individuals aged 20-80 years, with the first episode of stroke, and who could walk 5 m with or without assistive devices. The subjects were assigned to either an experimental group (n = 14) or a control group (n = 14). Both groups received 12 sessions of conventional stroke rehabilitation focusing on the affected side. In addition, individuals in the experimental group received structured strength training for the ULE. Main Outcome Measure: Balance, gait, and muscle strength of the ULE were measured pre and after 2 weeks of intervention using Brunel Balance Assessment (BBA), Wisconsin Gait Scale (WGS), 2D gait analysis (Kinovea software), and a handheld dynamometer, respectively. Results: The strength in the ULE of the experimental group improved significantly in all the muscle groups, whereas the control group showed improvements only in hip flexors, hip extensors, knee flexors, and ankle dorsiflexors. However, the strength gains in the hip flexors, hip abductors, knee extensors, and ankle dorsiflexors were significantly greater in the experimental group. Additionally, there was a significant difference among the groups in the BBA (p = 0.001) and WGS scores (p = 0.012). The kinematic variables of gait showed better knee flexion (p = 0.006), dorsiflexion angles (p = 0.016), and gait speed (p = 0.008) in the experimental group. Conclusion: Additional structured lower extremity strengthening of the ULE led to improved strength of ULE, resulting in better balance function and gait among individuals with acute stroke. Trial Registration: ClinicalTrials.gov identifier: CTRI/2018/12/016685.

Our previous study has developed FIVE, futsal neuromuscular warm-up program to improve physical performance components and prevent the incidence of futsal injury. Experimental research was needed to verify the effect of FIVE program on physical performance components affecting injury, such as lower limb muscle strength. This study aimed to investigate the effect of FIVE program on the lower limb muscle strength among young futsal players. Ninety-five young male futsal players were recruited using purposive random sampling from futsal clubs in Indonesia. The players were randomized into 2 groups; 42 players were in the experimental (EXP) group, and 53 players were in the control (CON) group. The EXP group performed FIVE exercises in addition to their regular futsal training, and the CON group performed their regular futsal training only. Both groups performed the intervention three times per week within 6 weeks. All players completed pre-and post-intervention lower limb muscle strength tests comprising the isometric leg strength, isometric hip abduction strength, and isometric hip adduction. The strength test was conducted using dynamometer. Changes in performance (pre- vs. post-intervention) of each group were analyzed using paired t-test and Wilcoxon Test. The pre- and post-strength test changes (Δ post-pre) between EXP and CON group was compared using independent T-test and Mann Whitney test. Statistical significance was set to P<0.05. Thirty-one players dropped out in this study. This study showed all measurements on lower limb muscle strength improved significantly in the EXP group (P<0.05) while hip abduction and hip adduction strength were significantly decreased in the CON group. Improvement of isometric hip abduction and adduction strength in the EXP group was significantly different from the CON group (P=0.00 and P=0.00, respectively). Results suggest that FIVE could be an alternative warm-up program to improve lower limb muscle strength among young futsal players.

This paper concentrates on the analysis of the human body of lower limb muscles and the effect of the gait motion. Eight human lower limb muscles are selected, containing: hip extensor: (semitendinosus and biceps femoris), hip flexor: (rectus femoris and vastus medialis), knee extensor: (vastus lateralis, rectus femoris, vastus medialis), knee flexor: (lateralis gastrocnemius, medialis gastrocnemius and semitendinosus), ankle plantar flexion: (lateralis gastrocnemius and medialis gastrocnemius), ankle dorsal flexor: (tibialis anterior). The Telemyo 2400 DTS and Vicon MX system is used to collect gait parameters and surface Electromyography (sEMG) of lower limbs when 10 healthy subjects walk on the oil trails recovery or fall from slipping during leg heel contacting trail moment to swing leg heel contacting trail moment (the first double support and single support phase). Moreover, this paper compares and analyzes the muscles reaction and gait parameters change about hip, knee and ankle after subjects suffer the interference and then slip or fall. The results indicate that increasing the stretching hip, the knee flexion and ankle dorsiflexion movement contributes to human recovery balance from unexpected slip. The results of this research will explore new ideas and provide a reference value for the formulation of anti-slip strategy, rehabilitation training and the development of lower limb walker.