Peak Knee Flexion Research Articles

A comparison of isokinetic muscle strength in patients with chondromalacia patella: a cross-sectional study.

Chondromalacia patella (CMP), which is one of the most common causes of anterior knee pain in young adults, is often accompanied by reflex inhibition of the quadriceps muscle. In this respect, a significant correlation between isokinetic parameters and knee muscle strengths would be expected. We hypothesized that an isokinetic dynamometer, which objectively evaluates muscle strength, may be an important guide in detecting muscle weakness in new-onset CMP and determining early treatment strategies. A total of 113 participants (mean age 30.33 ± 6.96 years, min: 18, max: 44) were recruited and divided into two groups, thus a CMP group (n=48) and a control group (n=65). The symptom duration of the CMP group and the demographic characteristics of all participants were recorded. Knee flexion and extension muscle strengths were measured at angular velocities of 60°/s and 180°/s [Knee extension Peak Torque at 60°/s (PTE60), Knee flexion Peak Torque at 60°/s (PTF60), Knee extension Peak Torque at 180°/s (PTE180), Knee flexion Peak at 180°/s (PTF180) respectively] (five sets) using an isokinetic dynamometer. We also recorded the total work done in flexion and extension (TWDF and TWDE). A modified MRI staging system based on the Outerbridge arthroscopy system was used to stage CMP. Isokinetic dynamometric parameters were compared between CMP patients and healthy volunteers. 59 healthy volunteers (90.8%) were right-side dominant and 6 (9.2%) left-side dominant. 33 CMP patients (68.8%) were right-side dominant, and 15 (31.3%) left-side dominant. 20 (41.7%) CMP patients were classified as Stage 1, 20 (41.7%) as Stage 2, and 8 (16.7%) as Stage 3. All the PTF60, PTE60, PTF180, and PTE180 values were significantly lower in the CMP group than in healthy controls (all p < 0.05). CMP symptom duration ≥ 6 months was associated with significantly lower knee muscle strength than with symptom duration < 6 months (p < 0.05). Also, a statistically negative correlation was found between MRI stages and PTE60 values (p < 0.05). In conclusion, our findings show that the isokinetic dynamometer reveals muscle weakness in CMP patients, and weakness in isokinetic parameters was negatively correlated with symptom duration and MRI stages. Isokinetic knee muscle strength testing, together with other functional tools, enables the assessment of muscle weakness and early rehabilitation planning for patients with CMP.

Gender Comparisons and Associations between Lower Limb Muscle Activation Strategies and Resultant Knee Biomechanics during Single Leg Drop Landings

(1) Background: We aimed to compare gender differences in knee biomechanics and neuromuscular characteristics, and to determine the relationships between lower limb muscle pre-activations and knee biomechanics during a single leg drop landing, in order to identify riskier landing patterns to prevent injury and intervene properly. (2) Methods: Descriptive laboratory cross-sectional study on 38 healthy untrained subjects with low to moderate physical activity status. (3) Results: During the initial-contact phase of landing, females demonstrated greater peak vertical ground reaction force (GRF) normalized to body weight (49.12 ± 7.53 vs. 39.88 ± 5.69 N/kg; p &lt; 0.001; Hedge’s g = 1.37), peak knee anterior reaction force normalized to body weight (0.23 ± 0.04 vs. 0.17 ± 0.05 N/kg; p &lt; 0.001; Hedge’s g = 1.33), and decreased pre-activation of the semitendinosus (45.10 ± 20.05% vs. 34.03 ± 12.05%; p = 0.04; Hedge’s g = 0.67). The final regression equation was peak knee anterior reaction force = 0.024 + 0.025 (peak knee flexion moment) − 0.02 (semitendinosus-to-vastus lateralis pre-activation ratio) + 0.003 (peak vertical GRF) (R2 = 0.576, p &lt; 0.001). (4) Conclusions: Overall, the data provided in this study support that a reduced semitendinosus-to-vastus lateralis pre-activation ratio predicted an increase in knee anterior reaction force and potentially an increase in ACL forces. Female non-athletes had gender-specific landing characteristics that may contribute to ACL injury. Future studies are warranted to consider more possible predictors of non-contact ACL injury.

Wearing a back-support exoskeleton impairs single-step balance recovery performance following a forward loss of balance – An exploratory study

Back-support exoskeletons (BSEs) are a promising ergonomic intervention for reducing physical demands on the low-back, but little is known regarding whether BSE use alters balance recovery following external perturbations. Hence, we investigated the effects of wearing a BSE on single-step balance recovery following a forward loss of balance. Sixteen (8 M, 8F) young, healthy participants were released from static forward-leaning postures and attempted to recover their balance with a single step while wearing a BSE (backXTM) with three different levels of support torque (i.e., no torque, low, and high) and in a control condition (no exoskeleton). Lean angle was increased until they failed in two consecutive trials to recover their balance with a single step. The maximum lean angle from which individuals could successfully recover was not significantly altered when wearing the BSE. However, wearing the BSE under all torque conditions increased reaction times. The BSE also impeded hip flexion (i.e., decrease in both peak hip flexion angle and angular velocity), resulting in decreased peak knee flexion velocity, knee range of motion, and step length. Measures of the margin of stability decreased significantly in the high-torque BSE condition. Overall, our results suggest that use of a BSE that provides external hip extension torque impairs balance recovery responses. Future work extending kinetic analyses to recovery responses, as well as a study of recovery when responding to slips and trips while walking, would offer a more complete picture of how a BSE may impact balance recovery following a loss of balance.

Patellofemoral contact forces and knee gait mechanics 3 months after ACL reconstruction are associated with cartilage degradation 24 months after surgery

Evaluate patellofemoral cartilage health, as assessed by quantitative magnetic resonance imaging (qMRI) T2 relaxation times, 24-months after ACL reconstruction (ACLR) and determine if they were associated with patellofemoral contact forces and knee mechanics during gait 3 months after surgery. Thirty individuals completed motion analysis during overground walking at a self-selected speed 3 months after ACLR. An EMG-driven neuromusculoskeletal model was used to determine muscle forces, which were then used in a previously described model to estimate patellofemoral contact forces. Biomechanical variables of interest included peak patellofemoral contact force, peak knee flexion angle and moment, and walking speed. These same participants underwent a sagittal bilateral T2 mapping qMRI scan 24-months after surgery. T2 relaxation times were estimated for both patellar and trochlear cartilage. Paired t-tests were used to compare T2 relaxation times between limbs while Pearson correlations and linear regressions were utilized to assess the association between the biomechanical variables of interest and T2 relaxation times. Prolonged involved limb trochlear T2 relaxation times (vsuninvolved) were present 24-months after surgery, indicating worse cartilage health. No differences were detected in patellar cartilage. Significant negative associations were present within the involved limb for all the biomechanical variables of interest 3 months after ACLR and trochlear T2 relaxation times at 24-months. No associations were found in patellar cartilage or within the uninvolved limb. Altered involved limb trochlear cartilage health is present 24-months after ACLR and may be related to patellofemoral loading and other walking gait mechanics 3 months after surgery.

Relationship Between Age and Running Kinematics in Female Recreational Runners.

Sex-based analyses are important when studying running kinematics. Females experience a unique aging process and demonstrate differences in running biomechanics from males. The purpose was to determine the relationship between age and running kinematics in female runners. Forty-six female runners (18-65y) ran at self-selected jogging and maximal speed on a treadmill. Lower-extremity joint kinematics were calculated, and 2 principal component analyses (jogging speed and maximal speed) were performed from kinematic variables. Regression was used to examine the relationship between age and identified components, and between age and the variables with the highest loadings within these components. For jogging speed, there was a positive relationship between age and ankle varus at initial contact and a negative relationship between age and peak eversion, hip adduction, knee flexion, dorsiflexion, and hip adduction at initial contact (Ps < .05). For maximal speed, initial contact ankle frontal plane angle became more positive with age, and there was a negative relationship with age and peak eversion, dorsiflexion and knee flexion, and knee flexion and hip adduction at initial contact (Ps < .05). Primarily distal joint angles decreased with increasing age in female recreational runners at self-selected running speeds.

Muscle activation timing and knee biomechanics during single leg hop in subjects with and without anterior cruciate ligament reconstruction: a case study

The Single Leg Hop test (SLHT) is commonly performed to determine readiness to return to sport (RTS) after anterior cruciate ligament (ACL) injury and reconstruction [1]. Usually, the between-limb symmetry of hop distance is considered as a criterion to clear the athletes to RTS. However, athletes may pass this criterion despite ongoing biomechanical and neuromuscular deficits. Several works developed an instrumented approach of the SLHT to assess biomechanical parameters associated to ACL injury risk [1]. Although it is known that muscle pre-activation timing during landing can be altered in patients with ACL reconstruction (ACLR) [2], thus exposing them to a reinjury risk, very few studies have related biomechanical parameters with electromyographic (EMG) signals of the involved muscles. The aim of this preliminary study is to assess muscle pre-activation timing prior to SLHT landing in both ACLR and HC athletes and to associate this information with ACL injury-related kinematic and kinetic parameters. Two male soccer athletes (Tegner Activity Score ≥ 6) participated in the study, one healthy (HC) and one with ACLR (12 months before the test; injured limb: left). They performed three SLHT landing on a force plate (AMTI, USA, 1000 Hz) after standardized warm-up. The 3D trajectories of 52 markers were measured by an optoelectronic system (Vicon, 200 Hz) [3]. Eight wireless bipolar EMG electrodes (MiniWave, Cometa, Italy) were placed on Vastus Medialis (VM), Vastus Laterialis (VL), Semitendinous (ST) and Biceps femoris (BF) on both limbs according to the SENIAM guidelines [4]. All instruments were electronically synchronized. Foot-force plate contact was identified by setting a threshold of 20 N on the vertical GRF (vGRF) [5]. EMG onset prior to landing was identified according to [2]. A set of ACL injury risk-related parameters were then extracted: peak vGRF (vGRF peak ), peak knee flexion and abduction moment (KMflex peak KMabd peak ), and knee flexion at initial contact (KflexIC). Also, for each SLHT, the hop distance was assessed (SLH dist ). The Limb Symmetry Index (LSI) was then calculated for each parameter. For each athlete and each limb, the SLH with the greater hopping distance was considered for further data processing. Muscle pre-activation timing was shorter in ACLR subject than HC in all muscles (Table 1). ACLR subject also showed higher values in peak knee moments, especially in the injured limb, as well as greater asymmetry for most of the investigated parameters, especially knee angles and moments. In the ACLR subject, the lower muscle pre-activation timing prior to landing may lead to an uncoordinated movement and to a deficit in muscle force generation to stabilize the joint, thus increasing knee injury risk [2]. This timing was even shorter in the injured limb. From a biomechanical point of view, a greater asymmetry was found in the ACLR subject with respect to the HC in both kinematic and kinetic parameters. On the contrary, hop distance LSI did not show any clear difference between the two participants. These results corroborate the hypothesis that evaluating only hop distance is reductive.

Effects of Foam Rolling on Strength and Flexibility of Hamstring Muscles

Foam rolling is frequently implemented in warm-up prior to an exercise session. The purpose of this study was to evaluate the acute effects of a short bout of foam rolling on maximal knee flexion strength along with active and passive hamstring flexibility. Methods: Fourteen healthy young participants were included in this within-subject randomized controlled trial. After warm-up a short bout (two sets of 60 s) of foam rolling was performed on the intervention leg (counterbalanced leg dominance) while the contralateral leg was used as a control. Measurement of peak knee flexion torque and hamstring passive and active range of motion were performed on both sides in counterbalanced order. An analysis of variance was conducted to evaluate differences between the two groups. Results: Our results did not show significant differences between the intervention and control leg for any of the assessed parameters. Conclusion: The main findings are that a short bout of foam rolling does not affect maximal knee flexion strength and that the foam rolling intervention does not further affect flexibility although hamstring passive flexibility increases following a warm-up. Based on our results we conclude that short bouts of foam rolling can be used prior to exercise, as they have no deleterious effect on muscle performance. Foam rolling before exercise should be recommended solely based on individual preference.

Validity of an artificial intelligence, human pose estimation model for measuring single-leg squat kinematics

Few studies have investigated the validity of 2D pose estimation models to evaluate kinematics throughout a motion and none have included adolescents. Adolescent athletes completed single-leg squats while 3D kinematic data and 2D sagittal and frontal plane videos were recorded. Sagittal and frontal plane joint motion throughout the single-leg squats and angles at peak knee flexion were compared among 2D pose estimation, 3D motion analysis, and traditional 2D motion analysis techniques. Statistical parametric mapping compared waveforms while Pearson’s correlation compared the relationships of joint angles at peak knee flexion among techniques, respectively. We observed significant waveform differences between 2D pose estimation and 3D motion analysis at the beginning and end of the squat for sagittal plane hip and knee motion, for most of the squat for frontal plane hip motion, and throughout the entire squat for sagittal plane ankle motion and frontal plane pelvic motion. We observed moderate-to-strong relationships (r = 0.68-0.94) for sagittal plane joint angles between 2D pose estimation and 3D techniques. We observed fair correlations (r = 0.53-0.54) for frontal plane pelvic and hip joint angles between 2D pose estimation and 3D motion analysis. We observed poor relationships for the frontal plane knee angle between 3D motion analysis with 2D pose estimation (r = 0.20) and traditional 2D motion analysis (r = 0.05), respectively, but observed a strong relationship (r = 0.95) between the 2D techniques. 2D pose estimation is a valid alternative to 3D motion analysis and traditional 2D motion analysis for evaluating most sagittal and frontal plane angles during a single-leg squatting task.

Differences in causes of stiff knee gait in knee extensor activity or ankle kinematics: A cross-sectional study

BackgroundStiff knee gait (SKG), a common occurrence after the onset of stroke, is caused by hyperactivity of the rectus femoris during the swing phase. Another cause of SKG is the weakness of push-off in hemiparetic gait. Prior research did not consider the effect of the magnitude of knee extensors in their subjects. Research questionDoes the cause of SKG differ between patients with high and low knee extensor activities during the swing phase? MethodsWe examined 38 patients with chronic stroke hemiplegia who presented with SKG. After placing an inertia sensor and an electromyogram, patients walked 10 m at a comfortable speed. All patients were categorized per the sign of the principal component 2 (PC2) as a component with large factor loadings of knee extensors attained from the electromyographic amplitude during the early swing phase of the paretic limb. Then, the kinematic parameters of knee flexion and other gait parameters in each group were compared, and a correlation analysis was performed. ResultsIn the high PC2 group, the timing of peak knee flexion during the swing phase was early, and vastus lateralis activity during the preswing phase negatively correlated with the knee-flexion angle during the swing phase. In the low PC2 group, the angular velocity of ankle plantar flexion at the toe-off was slow, which positively correlated with the knee-flexion angle during the swing phase. SignificanceThe cause of SKG could be an inappropriate activity of the vastus lateralis rather than the rectus femoris in patients with high knee extensor activity and slow plantar-flexion velocity at toe-off in patients with low knee extensor activity. Not all causes of SKG in patients with hemiplegia are common, and different treatment strategies are needed per the individuality of spastic knee extensor activity.

Isokinetic knee muscle strength asymmetry in university sweep rowers

The prevalence of musculoskeletal injuries in sweep rowing is high. As nearly 50% of power during sweep rowing is contributed by the legs, the presence of muscle imbalances may predispose rowers to overuse injuries. The purpose of the study was to assess knee muscle strength symmetry between dominant and non-dominant limbs of male and female rowers. A descriptive, quantitative research design was used. Twenty-four male and 13 female rowers aged 18–26 years participated. Bilateral isokinetic knee flexion and extension peak torque and hamstrings/quadriceps (H/Q) ratios were assessed at 60°/s and 180°/s using an isokinetic dynamometer. The data was analysed using Mann-Whitney U and Wilcoxon rank tests and significance was set at p≤0.05. In males, the dominant knee extension torque values at 60°/s and 180°/s were significantly larger than that of the non-dominant side (p≤0.05). In females, the non-dominant eccentric H/Q ratio at 60°/s was 15% larger than that of the dominant side (p=0.019). Bilateral differences observed in knee extension torque for males and in H/Q ratio for females highlight the need for isokinetic testing of sweep rowers, to improve performance and prevent injury.

Effects of Variations in Hemiparetic Gait Patterns on Improvements in Walking Speed

IntroductionCurrent research suggests that self-selected walking speed is an important indicator of hemiparetic gait rehabilitation outcome and can be targeted for improvement. Analysis of the relationship between walking speed and the kinematic profiles of the hemiparetic gait cycle can be expanded by comparing variations in their time dependant waveforms. MethodsThis paper is a pilot study to explore utilising the Linear Fit Method to compare the gait of a group of stroke survivors against a healthy baseline with respect to walking speed. This produced a set of parameters with clear physiological meaning that describe the variation of the hemiparetic gait pattern from the healthy pattern. A linear regression analysis was then performed comparing the resulting parameters against gait speed. ResultsSignificant linear relationships (p<0.05) were found between the Linear Fit parameters describing the hemiparetic gait pattern variations and walking speed in both paretic and non-paretic limbs. Most notably peak paretic knee flexion reduced by 20° and peak paretic hip abductions reducing to a nearly normal pattern while peak paretic hip flexions increased by 10°. The non-paretic hip flexion peak extensions remained 10° below the healthy comparison hip abduction offset was reduced but remained at nearly 2.5° to 5° from the healthy comparison. ConclusionsAs stroke survivors achieved higher walking speeds some aspects of their gait became more similar to the healthy comparison though others had no relation, or their differences became more pronounced. Combined, these relations show how paretic and non-paretic joint kinematics can be used to start identifying and quantifying effective compensatory hemiparetic gait patterns.

Breast Support Alters Trunk And Knee Joint Biomechanics During Double Limb Landing

Female athletes have a greater prevalence of traumatic knee injury than male athletes. Sex-based differences in injury rates emerge with maturation and the development of sex-specific traits including breast development. Breast support is known to alter trunk biomechanics during running tasks while in landing trunk orientation has been shown to mediate ACL strain. However, the effect of breast support on knee joint biomechanics has not been previously investigated. PURPOSE: To examine the effects of breast support on trunk and knee joint biomechanics during double limb landing. METHODS: Fourteen female collegiate athletes performed five double-limb landing trials in each of three sports bra conditions: no support, low support, and high support. Three-dimensional kinematics (240 Hz, Qualisys) and ground reaction forces (1200 Hz, AMTI Inc.) were recorded simultaneously. Visual 3D (C-Motion Inc.) was used to calculate peak trunk segment angles as well as peak knee joint angles and extension moments. A repeated measures ANCOVA with post-hoc pairwise comparisons were used to evaluate the effect of breast support on knee biomechanics. RESULTS: Increasing levels of breast support were associated with reductions in peak knee flexion (p = 0.008), peak knee valgus angles (p = 0.011) and peak knee valgus moments (p = 0.033) while there were no changes in peak knee moments (p = 0.216). Trunk flexion at initial contact (p = 0.024) and peak trunk flexion (p = 0.002) increased in response to greater breast support. CONCLUSIONS: The current data revealed a multi-joint mechanical adaptation in response to lower levels of breast support. These altered biomechanical patterns are consistent with a greater risk of traumatic knee injury including ACL rupture.

Kinematic Differences Between Landing Phase During Double And Single Leg Jumping Tasks

Anterior cruciate ligament (ACL) injury risk is often examined using the initial landing/takeoff phase following a drop off a box during a drop vertical jump (DVJ) task, while the second landing after maximum jump is not typically examined. As ACL injuries are frequently sustained during similar rapid deceleration maneuvers, the second landing during a DVJ and a single leg countermovement (SLC) jump may better simulate injury risk mechanics. PURPOSE: To investigate differences between landing phases during double and single leg jumping tasks. METHODS: 15 collegiate basketball players (height: 180.8 ± 14.0 cm, mass: 80.8 ± 19.0 kg) completed 3 DVJ and 3 maximum SLC jumps on each limb. Takeoff phase (TO) was defined as the first jump/landing and the landing phase (LN) was defined as the second landing for each task. High performance (HP) side was determined as the limb with the highest SLC jump compared to the low performance (LP) side. Standard 3D motion analysis was used to determine joint kinematics at peak knee flexion during each phase. A two-factor repeated measures ANOVA (p < 0.05) was used to determine differences between phase (TO, LN) and side (HP, LP). RESULTS: A main effect of phase during the DVJ was found for knee flexion (p < 0.001, TO: -83.1 ± 10.6°, LN: -68.6 ± 10.8°), knee abduction (p = 0.004, TO: -7.4 ± 5.2°, LN: -4.7 ± 4.9°), and hip flexion (p < 0.001, TO: 60.5 ± 11.7°, LN: 37.3 ± 13.1°) with a significant interaction between phase and side for hip adduction (p = 0.015). During the SLC jump, a main effect of phase was found for knee (p = 0.002, TO: -66.2 ± 8.7°, LN: -58.3 ± 10.8°) and hip (p = 0.005, TO: 48.7 ± 15.1°, LN: 35.4 ± 10.0°) flexion. A main effect of side was found for hip adduction (p = 0.029, HP: 5.3 ± 6.5°, LP: 8.4 ± 6.7°). No significant main effects were present for knee abduction during the SLC (p > 0.05). CONCLUSIONS: Collegiate basketball players exhibit greater knee and hip flexion and knee abduction during the initial land of the DVJ compared to the landing following maximum jump. Similarly, players also exhibit greater knee and hip flexion during the takeoff phase of a single leg task compared to the landing. However, they exhibit lower hip adduction on their higher performing limb. Between phase differences of each task outline the importance of identifying high-risk mechanics during both takeoff and landing.

Asymmetry In Single Leg Vertical Countermovement Hop Kinematics In Collegiate Female Soccer Players

Multidirectional sports such as soccer have a high incidence rate of anterior cruciate ligament injury. Asymmetries between limb have been linked to such non-contact injuries, thereby outlining the importance of screening measures that may identify at-risk groups. Specifically, tasks such as a vertical single leg countermovement (SLC) jump can provide an objective measure of frontal and sagittal plane asymmetries. PURPOSE: To identify lower limb asymmetries during a SLC jump. METHODS: 25 collegiate female soccer players (height: 167.4 ± 6.0 cm, mass: 67.16 ± 6.6 kg) completed 3 maximum SLC jumps on each limb. The side with the highest average jump height was defined as the high performance (HP) side and compared to the low performance side (LP). An 8 camera markerless motion capture system was utilized to analyze kinematic data at peak knee flexion during both the takeoff (TO) and landing (LN) phase using advanced machine learning. Force platforms measured the peak takeoff and landing vertical ground reaction force (GRF). A two-factor repeated measures ANOVA (p < 0.05) was used to determine differences between side (HP, LP) and phase (TO, LN) during the SLC task. RESULTS: 52% of the players had greater jump performance on their preferred kicking side. A main effect of side (p = 0.035) and phase (p < 0.001) was found for knee flexion (HP: TO 67.2 ± 7.2°, LN 60.5 ± 10.8°; LP: TO 65.0 ± 6.5°, LN 58.8 ± 7.2°). Likewise, a main effect of side (p < 0.001) and phase (p < 0.001) was found for GRF (HP: TO 1373 ± 236 N, LN 2238 ± 435 N; LP: TO 1341 ± 224 N, LN 2088 ± 280 N). A phase main effect was found for both hip flexion (p = 0.002) (HP: TO 49.8 ± 10.9°, LN 42.5 ± 11.9°; LP: TO 50.8 ± 10.1°, LN 41.0 ± 12.8°) and adduction (p = <0.001) (HP: TO 8.1 ± 4.4°, LN 5.5 ± 4.9°; LP: TO 8.7 ± 3.8°, LN 5.1 ± 5.7°). Significant main effects were not present for knee abduction (p > 0.05). CONCLUSIONS: Collegiate female soccer players demonstrate greater knee and hip flexion and hip adduction occur during the take-off phase of the single leg vertical jump compared to the landing phase. Additionally, the leg with greater performance has increased knee flexion during both take-off and landing which corresponds to greater peak force. These identified asymmetries between phase and limb could be considered important factors in monitoring potentially at-risk populations.

The relationship between lower-limb body composition with isokinetic performance in futsal players: Body composition and performance in futsal players

BACKGROUND: Optimal neuromuscular performance is essential for futsal athletes and it has been linked to body composition. AIM: The present study aimed to verify the relationship between absolute (total amount; kg) and relative (percentage; %) lower-limb and thigh lean and fat mass with isometric and dynamic maximal strength in professional futsal players. METHOD: Sixteen male elite futsal athletes participated in this study. Unilateral lower-limb and thigh lean and fat mass were evaluated using DXA (Dual-Energy X-ray Absorptiometry) and strength performance using unilateral isokinetic concentric-eccentric knee extension (KE) and flexion (KF) peak torque (PT), KE and KF isometric PT at 30° and 70°, and hamstrings-to-quadriceps ratios (H:Q). RESULTS: Unilateral lower-limb lean mass amount showed a significant positive correlation with concentric and isometric KE PT (60°/s: r=0.58; 30°: r=0.55; 70°: r=0.65), and with concentric (60°/s: r=0.61), eccentric (60°/s: r=0.67) and isometric (30°:r=0.79; 70°: r=0.70) KF PT. No significant relationship between lower-limb lean and fat mass percentage with isokinetic performance was verified. Thigh lean mass amount had a significant positive correlation with concentric and isometric KE PT (60°/s:r=0.52; 30°: r=0.51; 70°: r=0.84) and also with concentric (60°/s: r=0.75) and eccentric KF PT (60°/s:r=0.54), while thigh fat mass amount was only associated with eccentric KF PT (r=0.54). No significant correlation between lower-limb and thigh body composition with H:Q ratios was observed. CONCLUSION: In conclusion, contrary to the relative (%) values, absolute (kg) lower-limb and thigh fat and lean mass present a significant correlation with dynamic and isometric KE and KF performance in futsal players.

Dual Tasking May Increase ACL Injury Risk By Decreasing Knee Flexion Angle During Jump Landing

Non-contact anterior cruciate ligament (ACL) injuries are common among young athletes playing team sports. They must coordinate cognitive and motor processes to adapt an appropriate response to visual stimuli. It is unclear how divided attention to distractors impacts landing mechanics and ACL injury risk factors. PURPOSE: To investigate effects of dual tasking on ACL injury risk factors during jump landing using the Eriksen Flanker task. METHODS: Fourteen healthy females (age: 21 ± 2 years, mass: 64 ± 7 kg, height: 1.7 ± 0.1 m) participated in the study. They stood on a portable force platform (28 cm tall), jumped diagonally at a 60° angle to their right, landed on two in-ground force platforms and performed a second jump to their right or left at a 60° angle. The direction of the second jump appeared on a screen in front of the participant. The signal was either shown before movement (baseline) or during the flight phase of the first jump (dual task). The signal for the dual task conditions showed five arrows and participants jumped in the direction of the middle one. The four other arrows either pointed to the same direction as the middle arrow (congruent) or in the opposite direction (incongruent). Knee flexion angles, knee valgus angles, and external knee valgus moments were determined during the first 100 ms of landing. Repeated measures ANOVA was used to test for main effects of jump direction, dual task condition and interactions. RESULTS: There were significant main effects of jump direction, dual task condition, and their interaction for initial and peak knee flexion angles (p ≤ 0.009). Initial knee flexion angle (10.5 ± 5.1°vs. 14.5 ± 6.6°, p = 0.01) and peak knee flexion angle (56.2 ± 5.1° vs. 60.3 ± 5.9°, p = 0.003) were significantly lower during dual tasking when jumping to the right. There were no significant differences between the congruent and incongruent dual tasks or when jumping to the left. CONCLUSION: Initial and peak knee flexion angles were decreased when the visual stimuli was presented mid-flight rather than at the beginning of the jump when jumping to the right (lateral to the knee). However, the incongruent Flanker task did not significantly affect knee flexion angle. Further research focusing on mid-flight decision making with a more challenging incongruent visual stimuli that mimics dynamic team sports is merited.

Effects of Relative Inertial Load on Quadriceps Electromyography during Maximal Effort Flywheel-based Iso-Inertial Training (FIT) Squats

The effects of inertial load on quadriceps electromyography (EMG) during flywheel-based iso-inertial training (FIT) squats is unclear. Healthy, resistance-trained males (n=8) and females (n=8) completed five sets of five maximal-effort squats with varying inertial loads in a randomized order. Sagittal plane knee joint angles and surface EMG activity of the vastus lateralis (VL) were measured. Average knee angular velocity, but not peak knee flexion or total excursion, decreased during both the concentric and eccentric phases with increasing inertial load (p&lt;0.001) in both sexes. Integrated EMG (iEMG) activity increased with increasing inertial load for all muscles (p&lt;0.001). VL iEMG and peak amplitude were significantly greater in females. However, peak EMG amplitude was not significantly different among inertial loads for either sex. Mean EMG amplitude during the concentric phase and eccentric phases of the VL tended to be greater in females. Increasing relative inertial load increases quadriceps iEMG activity due to greater exercise duration, but has minimal effects on EMG amplitude.

35. Effect of surgical intervention on gait function in patients with symptomatic lumbar canal stenosis

<h3>BACKGROUND CONTEXT</h3> Gait impairment is one of the primary symptoms of degenerative lumbar canal stenosis (LCS), yet it is poorly understood due to a lack of quantitative data on kinematics and kinetics during the gait. Gait analysis is a well-established tool for the quantitative assessment of gait disturbances, providing a functional diagnosis, assessing treatment plan and monitoring of disease progress. <h3>PURPOSE</h3> To analyze the effect of decompression surgery on gait characteristics in patients with LCS. <h3>STUDY DESIGN/SETTING</h3> Prospective non-randomized comparative study at a teaching hospital. <h3>PATIENT SAMPLE</h3> Eighteen patients with symptomatic LCS and 18 healthy volunteers. <h3>OUTCOME MEASURES</h3> Gait quality: spatiotemporal, kinetic and kinematic parameters functional outcome: ODI, VAS. <h3>METHODS</h3> Eighteen patients with single-level LCS and 18 healthy volunteers were prospectively recruited. All the patients with symptomatic LCS underwent TLIF (transforaminal lumbar interbody fusion) surgery. Gait analysis was perfomed preoperatively and six months postoperatively as per standard protocol. The spatiotemporal, kinematic and kinetic parameters were analyzed. The Kolmogorov-Smirnov test and coefficient of skewness and kurtosis was used to assess the normality of distribution. Pre- and postoperative clinical outcomes, spatial-temporal, kinetic and kinematic data were compared with the paired t-test or Wilcoxon signed-rank test according to the normality of the distribution. Unpaired t-test was used to compare the two groups. Stepwise linear regression models were used to detect significant relationships between changes in ODI and VAS score, and parameters describing gait function. <h3>RESULTS</h3> Significant improvement was noted in ODI (p < 0.05) and VAS scores (p < 0.05) six months post-surgery. Spatiotemporal (Stride time [p=0.01], Swing phase % [p=0.01], Double support phase % [p=0.02], Mean velocity [p < 0.01], Cadence [p < 0.01], Stride length [p < 0.01], Step length [p < 0.01] and step width [p < 0.01])and kinetic parameters (peak hip [p < 0.01], knee [p < 0.01] and ankle power [p < 0.01], vertical GRF [p=0.01]) were significantly better following surgery, reaching normal levels when compared to healthy individuals. The kinematic parameters (trunk tilt [p=0.02], peak hip extension [p < 0.01], peak knee flexion in stance [p=0.01] and swing phase [p < 0.01], peak ankle dorsiflexion in stance [p < 0.01] and swing phase [p=0.04], GPS [p < 0.01] and GDI [p < 0.01]) were significantly improved following surgery but did not reach normal levels when compared to controls. A significant correlation was found between change in ODI and VAS score with change in certain kinematic parameters (knee power, stance time, ankle plantarflexion, peak ankle dorsiflexion moment, GDI, swing time, peak ankle dorsiflexion in swing, peak hip and knee flexor moment). <h3>CONCLUSIONS</h3> Decompression surgery in LCS produces improvement in gait parameters, pain scores, and functional outcome that significantly improves walking tolerance and speed. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Mechanical Factors Contributing to Altered Knee Extension Moment during Gait after ACL Reconstruction: A Longitudinal Analysis.

This study aimed to comprehensively examine the extent to which knee flexion angle at initial contact, peak knee flexion angle, and vertical ground reaction force (vGRF) contribute to knee extension moments during gait in individuals with anterior cruciate ligament (ACL) reconstruction. Overground gait biomechanics were evaluated in 26 participants with ACL reconstruction at three time points (about 2, 4, and 6 months after the surgery). Knee flexion angle at initial contact, peak knee flexion angle, peak vGRF, and peak knee extension moment were calculated for each limb during the early stance phase of gait for all three time points. A change score from baseline (time point 2 - time point 1 and time point 3 - time point 1) along with limb symmetry values (ACL - non-ACL limb values) was also calculated for these variables. Multiple linear regressions utilizing classical and Bayesian interference methods were used to determine the contribution of knee flexion angle and vGRF to knee extension moment during gait. Peak knee flexion angle and peak vGRF positively contributed to knee extension moment during gait in both the reconstructed ( R2 = 0.767, P < 0.001) and nonreconstructed limbs ( R2 = 0.815, P < 0.001). Similar results were observed for the symmetry values ( R2 = 0.673, P < 0.001) and change scores ( R2 = 0.731-0.883; all P < 0.001), except that the changes in knee flexion angle at initial contact also contributed to the model using the change scores in the nonreconstructed limb (time point 2 - time point 1: R2 = 0.844, P < 0.001; time point 3 - time point 1: R2 = 0.883, P < 0.001). Bayesian regression evaluating the likelihood of these prediction models showed that there was decisive evidence favoring the alternative model over the null model (all Bayes factors >1000). Standardized β coefficients indicated that changes in knee flexion angle had a greater impact (>2×) on knee extension moments than vGRF at both time points in both limbs ( βvGRF = 0.204-0.309; βkneeflexion = 0.703-0.831). The findings indicate that both knee flexion angle and peak vGRF positively contribute to altered knee extension moments during gait, but the contribution of knee flexion angle is much greater than vGRF. Therefore, treatment strategies targeting these variables may improve knee loading after ACL reconstruction.

Bone-Patellar Tendon-Bone Autograft Harvest Prolongs Extensor Latency during Gait 2 yr after ACLR.

Bone-patellar tendon-bone (BPTB) graft harvest for anterior cruciate ligament reconstruction alters patellar tendon properties, which inflict poor quadriceps neuromuscular function. BPTB autografts are associated with higher rates of posttraumatic osteoarthritis, which in turn is associated with pathological gait. The purpose of this study was to investigate the latency between the time of peak quadriceps activity and the peak knee flexion moment during gait, between those with BPTB grafts ( n = 23) and other graft types (hamstring autograft or allografts, n = 54), 5 ± 2 months and 2 yr (25 ± 3 months) after anterior cruciate ligament reconstruction. We hypothesized that longer latencies would be observed in the BPTB graft group in the involved limb. We expected latencies to shorten over time. Knee moments and quadriceps EMG were collected during gait, and vastus medialis, vastus lateralis, rectus femoris (RF), and quadriceps latencies were calculated. Linear mixed-effects models were used to compare latencies between graft types and over the two time points. The main effects of graft type were observed for vastus medialis ( P = 0.005) and quadriceps ( P = 0.033) latencies with the BPTB graft group demonstrating longer latencies. No main effects of graft type were observed for vastus lateralis ( P = 0.051) and RF ( P = 0.080) latencies. Main effects of time were observed for RF latency ( P = 0.022). Our hypothesis that the BPTB graft group would demonstrate longer extensor latency was supported. Contrary to our second hypothesis, however, latency only improved in RF and regardless of graft type, indicating that neuromuscular deficits associated with BPTB grafts may persist 2 yr after surgery. Persistent deficits may be mediated by changes in the patellar tendon's mechanical properties. Graft-specific rehabilitation may be warranted to address the long-term neuromechanical deficits that are present after BPTB graft harvest.