Knee Extension Force Research Articles

Older Compared With Younger Adults Performed 467 Fewer Sit-to-Stand Trials, Accompanied by Small Changes in Muscle Activation and Voluntary Force.

Background: Repetitive sit-to-stand (rSTS) is a fatigue perturbation model to examine the age-effects on adaptability in posture and gait, yet the age-effects on muscle activation during rSTS per se are unclear. We examined the effects of age and exhaustive rSTS on muscle activation magnitude, onset, and duration during ascent and descent phases of the STS task.Methods: Healthy older (n = 12) and younger (n = 11) adults performed rSTS, at a controlled frequency dictated by a metronome (2 s for cycle), to failure or for 30 min. We assessed muscle activation magnitude, onset, and duration of plantar flexors, dorsiflexors, knee flexors, knee extensors, and hip stabilizers during the initial and late stages of rSTS. Before and after rSTS, we measured maximal voluntary isometric knee extension force, and rate of perceived exertion, which was also recorded during rSTS task.Results: Older vs. younger adults generated 35% lower maximum voluntary isometric knee extension force. During the initial stage of rSTS, older vs. younger adults activated the dorsiflexor 60% higher, all 5 muscle groups 37% longer, and the hip stabilizers 80% earlier. Older vs. younger adults completed 467 fewer STS trials and, at failure, their rate of perceived exertion was ~17 of 20 on the Borg scale. At the end of the rSTS, maximum voluntary isometric knee extension force decreased 16% similarly in older and younger, as well as the similar age groups decline in activation of the dorsiflexor and knee extensor muscles (all p < 0.05).Conclusion: By performing 467 fewer STS trials, older adults minimized the potential effects of fatigability on muscle activation, voluntary force, and motor function. Such a sparing effect may explain the minimal changes in gait after rSTS reported in previous studies, suggesting a limited scope of this perturbation model to probe age-effects on muscle adaptation in functional tasks.

Microcirculatory Responses to Muscle and Tendon Exercises in Individuals With and Without Type 2 Diabetes Mellitus and the Association Between Microcirculatory and Exercise Performance.

Background: This study aimed to measure and compare (1) the microcirculation and microcirculatory responses of the muscles and tendons at rest and during isometric muscle contractions in participants with and without diabetes mellitus (DM) and (2) to determine correlations between microcirculation and muscle strength. Methods: Sixty-three participants with type 2 DM and 42 physically matched controls were recruited. Baseline measurements of the microcirculation of the rectus femoris (RF) and medial gastrocnemius (MG) muscles and patellar (PT) and Achilles tendons (AT), as well as their microcirculatory changes during maximal isometric exercises, were performed and recorded by using near-infrared spectroscopy and a red laser. Data on various laboratory tests (including glycated hemoglobin, triglyceride, high-density cholesterol), the monofilament test, and the ankle-brachial index were also obtained. Results: The baseline measurements indicated that, compared with the controls, the diabetic participants had lower oxygen saturation (SpO2) in their RF and MG muscles (both P < 0.001), and the total hemoglobin in the diabetic PT and AT was higher (P = 0.001 and P = 0.01). The minimal SpO2 levels in the aforementioned muscles during isometric contractions were lower in the diabetes group than in the control group (P ≤ 0.001). Furthermore, there were correlations between the microcirculatory change of the RF muscle and the knee extension force. Conclusions: This study demonstrated the effects of diabetes on the microcirculation of skeletal muscles and tendons during baseline measurements and responses to maximal isometric exercises. The results support the need for preventive strategies for diabetic muscles to prevent adverse complications when performing resistance training.

The Effect of Resistance Exercise Priming in the Morning on Afternoon Sprint Cross-Country Skiing Performance.

We tested whether a single session of heavy-load resistance priming conducted in the morning improved double-poling (DP) performance in the afternoon. Eight national-level male cross-country skiers (mean [SD]: 23 [3]y, 184 [6]cm, 73 [7]kg, maximum oxygen consumption = 69 [6]mL·kg-1·min-1) carried out 2days of afternoon performance tests. In the morning, 5hours before tests, subjects were counterbalanced to either a session of 3 × 3 repetitions (approximately 85%-90% 1-repetition maximum) of squat and sitting pullover exercises or no exercise. The performance was evaluated in DP as time to exhaustion (TTE) (approximately 3min) on a treadmill and 30-m indoor sprints before and after TTE (30-m DP pre/post). Furthermore, submaximal DP oxygen cost, countermovement jump, and isometric knee-extension force during electrical stimulation were conducted. Participants reported perceived readiness on test days. Resistance exercise session versus no exercise did not differ for TTE (approximately 3min above) (mean ± 95% confidence interval = 3.6% ± 6.0%; P = .29; effect size [ES], Cohen d = 0.27), 30-m DP pre (-0.56% ± 0.80%; P = .21; ES = 0.20), 30-m DP post (-0.18% ± 1.13%; P = .76; ES = 0.03), countermovement jump (-2.0% ± 2.8%; P = .21; ES = 0.12), DP oxygen cost (-0.13% ± 2.04%; P = .91; ES = 0.02), or perceived readiness (P ≥ .11). Electrical stimulation force was not different in contraction or relaxation time but revealed low-frequency fatigue in the afternoon for the resistance exercise session only (-12% [7%]; P = .01; ES = 1.3). A single session of heavy-load, low-volume resistance exercise in the morning did not increase afternoon DP performance of short duration in high-level skiers. However, leg low-frequency fatigue after resistance priming, together with the presence of small positive effects in 2 out of 3 DP tests, may indicate that the preconditioning was too strenuous.

No correlation between symmetry-based performance measures and patient-related outcome prior to and after total knee arthroplasty.

Standardized outcome measures are crucial for the evaluation of different treatment and rehabilitation regimes in patients after total knee arthroplasty (TKA). Performance-based measures are necessary to capture different aspects of physical function. High reliability and agreement of five performance-based measures were hypothesized to differentiate between measurement error and change in test performance. Secondary outcomes are the correlation of performance-based measurements to KSS and WOMAC prior to surgery (baseline) and 10weeks thereafter (t3). The test-retest reliabilities and agreements of the 1-m walk test, the stair-climbing test, the timed-up-and-go test, the weight-balanced-chair-rising test and the isometric maximum knee extension force in patients undergoing total knee replacements were studied. The intraclass correlation coefficient was calculated and a Bland-Altman analysis performed. The weight-balanced-chair-rising test showed a symmetry at baseline = 0.77, 5 ± 1days after surgery (t1) = 0.50, 9 ± 1days (t2) = 0.59 and (t3) = 0.80. All performance tests showed high intraclass correlation coefficients (ICC = 0.81-0.99). The 10-m walk test, stair climbing test, and the timed-up-and-go test showed high agreement in the Bland-Altman analysis. The Bland-Altman analysis for the weight-balanced-chair-rising test and isometric knee extension force indicated high agreement at 5 and 9days postoperatively, but the relative measurement error increased pre- and 10weeks postoperatively. In conclusion, symmetry, as an important outcome after TKA, is a reliable and rather unique item that should unquestionably be added to established measurements like walking tests or survey-based function assessment. The implementation of standardized performance-based measures to assess physical function in rehabilitation procedures will help to improve the more objectively based assessment of different rehabilitation protocols. II.

Fish Protein Ingestion Induces Neural, but Not Muscular Adaptations, Following Resistance Training in Young Adults.

Purpose: Nutritional supplementation in conjunction with exercise is of interest for the prevention or improvement of declines in motor performances in older adults. An understanding of the effects on both young and older adults contributes to its effective application. We investigated the effect of fish protein ingestion with resistance training on neural and muscular adaptations in young adults using interventions and assessments that have already been tested in older adults.Methods: Eighteen young adults underwent 8 weeks of isometric knee extension training. During the intervention, nine participants ingested 5 g of fish protein (n = 9, Alaska pollack protein, APP), and the other nine participants ingested casein as a control (n = 9, CAS) in addition to daily meals. Before, during, and after the intervention, the isometric knee extension force, lower extremity muscle mass, and motor unit firing pattern of knee extensor muscles were measured.Results: Maximum voluntary contraction (MVC) was significantly increased in both APP and CAS groups from 0 weeks to 4, 6, and 8 weeks of intervention (p < 0.001), but there were no significant differences between the groups (p = 0.546–0.931). Muscle mass was not significantly changed during the intervention in either group (p = 0.250–0.698). Significant changes in motor unit firing rates (p = 0.02 and 0.029 for motor units recruited at 20–40% of MVC and at 40–60%) were observed following the intervention in the APP but not CAS (p = 0.120–0.751) group.Conclusions: These results suggest that dietary fish protein ingestion changes motor unit adaptations following resistance training in young adults.

Neural Correlates of Knee Extension and Flexion Force Control: A Kinetically-Instrumented Neuroimaging Study.

Background: The regulation of muscle force is a vital aspect of sensorimotor control, requiring intricate neural processes. While neural activity associated with upper extremity force control has been documented, extrapolation to lower extremity force control is limited. Knowledge of how the brain regulates force control for knee extension and flexion may provide insights as to how pathology or intervention impacts central control of movement.Objectives: To develop and implement a neuroimaging-compatible force control paradigm for knee extension and flexion.Methods: A magnetic resonance imaging (MRI) safe load cell was used in a customized apparatus to quantify force (N) during neuroimaging (Philips Achieva 3T). Visual biofeedback and a target sinusoidal wave that fluctuated between 0 and 5 N was provided via an MRI-safe virtual reality display. Fifteen right leg dominant female participants (age = 20.3 ± 1.2 years, height = 1.6 ± 0.10 m, weight = 64.8 ± 6.4 kg) completed a knee extension and flexion force matching paradigm during neuroimaging. The force-matching error was calculated based on the difference between the visual target and actual performance. Brain activation patterns were calculated and associated with force-matching error and the difference between quadriceps and hamstring force-matching tasks were evaluated with a mixed-effects model (z > 3.1, p < 0.05, cluster corrected).Results: Knee extension and flexion force-matching tasks increased BOLD signal among cerebellar, sensorimotor, and visual-processing regions. Increased knee extension force-matching error was associated with greater right frontal cortex and left parietal cortex activity and reduced left lingual gyrus activity. Increased knee flexion force-matching error was associated with reduced left frontal and right parietal region activity. Knee flexion force control increased bilateral premotor, secondary somatosensory, and right anterior temporal activity relative to knee extension. The force-matching error was not statistically different between tasks.Conclusion: Lower extremity force control results in unique activation strategies depending on if engaging knee extension or flexion, with knee flexion requiring increased neural activity (BOLD signal) for the same level of force and no difference in relative error. These fMRI compatible force control paradigms allow precise behavioral quantification of motor performance concurrent with brain activity for lower extremity sensorimotor function and may serve as a method for future research to investigate how pathologies affect lower extremity neuromuscular function.

Clinical Outcome After Replacement of Distal Femur/Proximal Tibia in a Heterogeneous Patient Cohort: Function Following Tumour, Trauma, and Loosening

Background: Distal femur and proximal tibia replacements as limb-salvage procedures with good outcome parameters for patients with tumours have been broadly described. However, the overall midterm outcome in a mixed, heterogeneous patient collective is still unclear. Patients and Methods: We retrospectively analysed 59 consecutive patients (33 for primary and 26 for revision surgery) between 1998 and 2017. Indication for implantation was tumour (n=16), periprosthetic fracture (n=14), traumatic fracture (n=14), infection (n=10), aseptic loosening (n=3), and pathological fracture (n=2). The mean follow-up duration was 3 years. Clinical functions were evaluated by Toronto Extremity Salvage Score and Knee Society Score. Knee extension and flexion force were measured. Results: The overall survival rate of arthroplasties was 59% (n=35). Major complications were observed in 36 (61%) patients. During the follow-up period, 14 (24%) patients died. We recorded periprosthetic joint infection in 21 (36%) patients, recurrence of tumour in two (3%), and aseptic implant failure in three (5%). The mean Toronto Extremity Salvage Score was 66±33, and the mean Knee Society Score was 49±30. The mean extension force on the operated side was significantly reduced at 60° and 180° compared to the healthy side (p=0.0151 and p=0.0411, respectively). Conclusion: Distal femur and proximal tibia replacements showed limited clinical function in a heterogeneous patient collective. Indication for implantation should be considered carefully.

Does dark chocolate have an ergogenic impact on emotional state, vegetative nervous system and strength performance?

The aim of this research is to assess the acute effect of consuming a dark chocolate with lemon (DCL) bar on the emotional state, the vegetative nervous system, and strength performance. This protocol was carried out by eleven male trained cyclists and trail runners (age: 27 ± 12 years old), who tested, in random order, either DCL bar containing flavonoids or a white chocolate bar (placebo) before a simulated competition of knee extension force. Their precompetitive state anxiety (SA), blood pressure, heart rate variability (HRV), and electroencephalography (EEG) responses were measured before and after eating the bars. The maximal voluntary force (MVC) of the knee extensor and the time to exhaustion (TTE) at 20% of MVC were recorded 2 h after eating the bars. Compared to placebo, DCL decreases significantly (p &lt; 0.05) the SA and the systolic blood pressure. An increase of α and a decrease of β waves with a moderate effect size (d = 0.7) were found in the prefrontal cortex, whereas no significant change was observed for HRV and MVC. However, an increase (+22%) of TTE with a moderate effect size (d = 0.5) was found. These findings suggest the potential role of flavonoids to decrease precompetitive anxiety as a complementary routine to improve strength performance.

Correlation of paretic knee extension strength with gait speed after stroke: A meta-analysis

BACKGROUND AND OBJECTIVE: Numerous studies have addressed the relationship between paretic knee extension strength and comfortable walking speed after stroke. However, the correlations reported are highly variable. This review sought to summarize the correlational data using meta-analysis. METHODS: Relevant literature was identified via a search of 3 bibliographic databases. Articles were screened and perused for inclusion. Included articles were examined for information on the sample studied, procedures for measuring strength and gait speed, and correlations reported between the 2 variables. Meta-analysis was used to calculate a summary correlation. RESULTS: Of 299 unique articles, 18 met inclusion criteria. Articles were diverse in regard to samples studied, procedures described, and correlations reported. Meta-analysis using data from all included studies revealed a summary correlation of 0.51. For studies using hand-held or isokinetic dynamometry, the summary correlation was 0.46 and 0.59 respectively. CONCLUSIONS: This study provides a better indication of the correlation between paretic knee extension strength and comfortable gait speed than individual studies. The correlation is high enough to provide support for the routine measurement of paretic knee extension force for individuals who have experienced a stroke.

History-Dependence of Muscle Excitation and Oxygenation During Isometric Knee Extension Force Production

PURPOSE:This study examined the issue of history-dependence on muscle excitation and oxygenation by using surface electromyography (EMG) and near-infrared spectroscopy (NIRS).METHODS: Eight male participants performed isometric knee extension force production tasks that started at four levels of initial force production (30, 40, 60, 70% of maximal voluntary contraction, MVC) and commonly converged to the production of 50% of MVC by increasing or decreasing knee extension forces. We quantified the integrated electromyogram (iEMG), total hemoglobin (tHb), and the desaturation rate of muscle tissue (TSI&lt;sub&gt;SLOPE&lt;/sub&gt;) of the vastus lateralis and compared the differences in the quantified variables between the experimental conditions.RESULTS: For the four levels of initial forces production, all the variables showed significant linear relationships with outcome forces. However, the magnitudes of the variables were varied depending on the contraction history at the terminal phase where the identical level of force production (50% of MVC) was required. At the terminal phase, the iEMG was affected by the time history of both mode (e.g., increment or decrement) and magnitude (e.g., 10% or 20% change of MVC), while the tHb and TSI&lt;sub&gt;SLOPE&lt;/sub&gt; showed significant differences between the time history of mode only.CONCLUSIONS:The main result of the current study demonstrates the history-dependence of the changes in physiological demands in muscle activation. In particular, the indices of muscle excitation and oxygenation at the same level of force were varied depending on the time history of contraction, which implies the indices of muscle excitation and oxygenation may not be invariant component to specify the levels of outcome forces.

Acute effect of tendon vibration applied during isometric contraction at two knee angles on maximal knee extension force production

The aim of the current study was to investigate the effect of a single session of prolonged tendon vibration combined with low submaximal isometric contraction on maximal motor performance. Thirty-two young sedentary adults were assigned into two groups that differed based on the knee angle tested: 90° or 150° (180° = full knee extension). Participants performed two fatigue-inducing exercise protocols: one with three 10 min submaximal (10% of maximal voluntary contraction) knee extensor contractions and patellar tendon vibration (80 Hz) another with submaximal knee extensor contractions only. Before and after each fatigue protocol, maximal voluntary isometric contractions (MVC), voluntary activation level (assessed by the twitch interpolation technique), peak-to-peak amplitude of maximum compound action potentials of vastus medialis and vastus lateralis (assessed by electromyography with the use of electrical nerve stimulation), peak twitch amplitude and peak doublet force were measured. The knee extensor fatigue was significantly (P<0.05) greater in the 90° knee angle group (-20.6% MVC force, P<0.05) than the 150° knee angle group (-8.3% MVC force, P = 0.062). Both peripheral and central alterations could explain the reduction in MVC force at 90° knee angle. However, tendon vibration added to isometric contraction did not exacerbate the reduction in MVC force. These results clearly demonstrate that acute infrapatellar tendon vibration using a commercial apparatus operating at optimal conditions (i.e. contracted and stretched muscle) does not appear to induce knee extensor neuromuscular fatigue in young sedentary subjects.

Effectiveness of impedance parameters for muscle quality evaluation in healthy men

We investigated the relationship between impedance parameters and skeletal muscle function in the lower extremities, as well as the effectiveness of impedance parameters in evaluating muscle quality. Lower extremity impedance of 19 healthy men (aged 23–31 years) measured using the direct segmental multi-frequency bioelectrical impedance analysis were arc-optimized using the Cole–Cole model, following which phase angle (PA), {R}_{i}/{R}_{e}, and β were estimated. Skeletal muscle function was assessed by muscle thickness, muscle intensity, and isometric knee extension force (IKEF). IKEF was positively correlated with PA (r = 0.58, p < 0.01) and β (r = 0.34, p < 0.05) was negatively correlated with {R}_{i}/{R}_{e} (r = − 0.43, p < 0.01). Stepwise multiple regression analysis results revealed that PA, β, and {R}_{i}/{R}_{e} were correlated with IKEF independently of muscle thickness. This study suggests that arc-optimized impedance parameters are effective for evaluating muscle quality and prediction of muscle strength.

INFLUENCE OF AN ACUTE BOUT OF SELF-MYOFASCIAL RELEASE ON KNEE EXTENSION FORCE OUTPUT AND ELECTRO-MECHANICAL ACTIVATION OF THE QUADRICEPS.

In contrast to static stretching (SS), previous research has demonstrated increases in flexibility after an acute bout of self-myofascial release (SMR) without any subsequent decreases in force output. Previous research has utilized measures of surface electromyography (sEMG) and mechanomyography (MMG) to examine the influence of SS on the electrical and mechanical processes of muscle activation, respectively. However, there is a lack of research examining the potential changes in electro-mechanical muscle activation post-SMR. To examine the influence of SMR, via an acute bout of foam rolling (FR) to the vastus lateralis (VL), on the expression of knee extension force output and the inter-muscular electro-mechanical activation of the quadriceps musculature. Randomized crossover trial. Twenty (10 males, 10 females) recreationally-active participants with prior FR experience completed both SMR and control (CON) testing protocols during separate testing sessions that were conducted in a randomized order 48 hours apart. During the SMR protocol, participants performed 3 sets of 60 seconds of FR over the VL portion of their quadriceps musculature, with 60 seconds of rest between sets. During the CON protocol, participants quietly sat upright for 10 minutes. Peak knee extension force output -(Forcepeak) data, as well as sEMG and MMG data from the VL and the rectus femoris (RF) were collected during maximal voluntary isometric contractions (MVICs) before and after both testing protocols. Root mean square sEMG and MMG amplitudes were calculated to represent electro-mechanical muscle activation of the VL (VL-sEMGRMS, VL-MMGRMS) and RF (RF-sEMGRMS, RF-MMGRMS) musculature. Repeated measures analyses of variance (RM ANOVAs) identified a significant (p < 0.05) increase in Forcepeak within the SMR protocol among males, but no change among females. No statistically significant changes in any electro-mechanical muscle activation measures were identified pre-to-post-SMR within either sex. In contrast to the SS literature body, these results suggest that SMR does not influence the electro-mechanical aspects of muscle activation during MVICs. These results provide support for the absence of decreases in force output post-SMR, but further examination regarding the potential muscle mass influence of SMR on electro-mechanical muscle function remains warranted. 2c.

Changes in brain activity induced by the N-back task are related to improved dual-task performance

Dual-task performance often influences athletic competition results. Previous studies have suggested that cognitive tasks might improve dual-task performance. However, the factors that contribute to the manner in which cognitive tasks improve dual-task performance remain unknown. This study aimed to examine whether changes in brain activity induced by cognitive tasks are associated with improvement in dual-task performance. Nineteen young healthy adults performed an N-back and a reaction task on different days. A dual-task was constructed by combining a force-control and a calculation task. In the force-control task, participants adjusted their knee extension force according to target waves. In the calculation task, participants were required to subtract and respond to auditory stimuli delivered via earphones. We evaluated dual-task performance before and after performing each cognitive task. Additionally, we measured cerebral hemodynamic activity using near-infrared spectroscopy during the performance of each cognitive task. As a result, performing the N-back task improved performance in the force-control task under the dual-task setup. Furthermore, increase in oxyhemoglobin in a part of the right dorsolateral prefrontal cortex during the N-back task was positively correlated with improved force control during the subsequent dual-task. Cognitive tasks can be easily performed in a clinical field. Thus, cognitive tasks could be incorporated in traditional physical training. Future research should investigate whether the present findings can translate to improving performance in athletic competitions.

Telomere shortening is associated with poor physical performance in knee osteoarthritis.

Telomere length is a hallmark characteristic of ageing and age-related diseases. Osteoarthritis (OA) is the most common cause of joint pain and physical disability in the elderly. Previous studies have revealed the role of telomere shortening in OA; however, the relationship between telomere length, muscle strength and physical performance in knee OA patients remains unknown. The aim of the present study was to investigate the association of telomere length and physical performance in patients with knee OA. A total of 202 patients with knee OA and 60 healthy controls were enrolled in the study. The quality of life was assessed using Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index and Short Form Health Survey. The skeletal muscle mass was examined using bioelectrical impedance analysis, while the muscle strength was analyzed using hand grip force and isometric knee extension force. The physical performance of patients with knee OA was also investigated using gait speed, Timed up and go test (TUGT), Sit to stand test and 6-min walk test (6MWT). Blood leukocyte relative telomere length (RTL) was assessed using real time quantitative PCR. The mean blood leukocyte RTL in knee OA subjects was significantly lower compared with healthy controls (P<0.001). Knee OA patients with RTL values in the lowest quartile had a slow gait speed (P=0.006) and prolonged TUGT time (P=0.03). Multivariate regression analyses and multiple logistic regression analyses adjusted for age, sex, waist circumference, body mass index, fat mass, skeletal muscle index and the total WOMAC demonstrated that gait speed, TUGT and 6MWT were associated with longer RTL (P-trend<0.05). These findings suggested that poorer physical performance was associated with shorter RTL. Therefore, leukocyte telomere length and physical performance tests, especially gait speed, TUGT and 6MWT, could predict the health status and quality of life in patients with knee OA.

Sagittal And Frontal Plane Joint Moments Of The Sumo Deadlift During Shod And Barefoot Conditions

Sumo style deadlifting has recently become more prevalent. Barefoot-style lifting has also become increasingly popular with claims such as increased force production and improved “grounding” of the foot. However, the biomechanics of sumo deadlifting while barefoot have not been examined. PURPOSE: To examine the effects on the hip, knee, and ankle joint moments during a sumo deadlift when comparing shod and barefoot conditions. METHODS: Ten subjects (27.3±3.5 yrs, 1.74±0.13m, 77.97±17.34kg) with minimum six months of deadlift experience (7.6±4.6 yrs), who were free from lower extremity injury, performed 1 repetition maximum (1RM; 137.7±43.0 kg) testing on day 1. This testing was performed in self-selected footwear. On day 2, a minimum of 72 hours later, subjects lifted 70% of their 1RM during a 3-dimensional analysis. Subjects performed one set of five continuous repetitions of a sumo deadlift in shod and barefoot conditions in randomized order. Five minutes of rest was given between sets. Marker data were collected using Qualisys Track Manager, sampling at 240Hz. Force data were collected using Bertec force plates, sampling at 1200Hz. Raw marker and force data were imported into Visual3D. Marker and force data were filtered using a fourth-order lowpass Butterworth filter at 8Hz. Peak internal sagittal and frontal plane joint moments of the hip, knee, and ankle were calculated during the concentric phase of each repetition. Peak vertical ground reaction force was measured during the concentric phase. RESULTS: No significant differences were detected in peak hip extension moment (p=0.855), hip abduction (p=0.288), knee extension (p=0.607), knee abduction (p=0.926), ankle plantarflexion (p=0.376), ankle eversion (p=0.739), or peak vertical ground reaction force (p=0.558). CONCLUSIONS: There is no evidence to suggest that the barefoot lifting style increases performance capabilities when lifting the same weight as in the shod condition. Additionally, there is no evidence to suggest that there is any increased risk in excess frontal plane joint moments during barefoot lifting. Future research should examine the 1RM capabilities in both shod and barefoot conditions to determine if differences exist during maximal compared to submaximal efforts.

Mechanical and Material Tendon Properties in Patients With Proximal Patellar Tendinopathy.

IntroductionThe effect of chronic patellar tendinopathy on tissue function and integrity is currently unclear and underinvestigated. The aim of this cohort comparison was to examine morphological, material, and mechanical properties of the patellar tendon and to extend earlier findings by measuring the ability to store and return elastic energy in symptomatic tendons.MethodsSeventeen patients with chronic (>3 months, VISA-P < 80), inferior pole patellar tendinopathy (24 ± 4 years; male = 12, female = 5) were carefully matched to controls (25 ± 3 years) for training status, pattern, and history of loading of the patellar tendon. Individual knee extension force, patellar tendon stiffness, stress, strain, Young’s modulus, hysteresis, and energy storage capacity, were obtained with combined dynamometry, ultrasonography, magnetic resonance imaging, and electromyography.ResultsAnthropometric parameters did not differ between groups. VISA-P scores ranged from 28 to 78 points, and symptoms had lasted from 10 to 120 months before testing. Tendon proximal cross-sectional area was 61% larger in the patellar tendinopathy group than in the control group. There were no differences between groups in maximal voluntary isometric knee extension torque (p = 0.216; d < −0.31) nor in tensile tendon force produced during isometric ramp contractions (p = 0.185; d < −0.34). Similarly, tendon strain (p = 0.634; d < 0.12), hysteresis (p = 0.461; d < 0.18), and strain energy storage (p = 0.656; d < 0.36) did not differ between groups. However, patellar tendon stiffness (−19%; p = 0.007; d < −0.74), stress (−27%; p< 0.002; d < −0.90) and Young’s modulus (−32%; p = 0.001; d < −0.94) were significantly lower in tendinopathic patients compared to healthy controls.DiscussionIn this study, we observed lower stiffness in affected tendons. However, despite the substantial structural and histological changes occurring with tendinopathy, the tendon capacity to store and dissipate energy did not differ significantly.

Patients outcome after distal femur- and proximal tibia replacement

Aims and Objectives:Mega-knee-arthroplasty are rare and indications are heterogeneous after fracture, tumour and infection. The outcome after distal femur- and/or proximal tibia replacement are unclear. We therefore wanted to analyse the postoperative outcome in case of primary and revision surgery. We hypothesize that I) Implantation of distal femur- and/or proximal tibia replacement are associated with reduced range of motion and function compared to the contralateral side and II) implantation in case of primary surgery is associated with better outcome than in case of revision surgery.Materials and Methods:We retrospectively analysed all patients in our trauma department between 1998 and 2017 who underwent a MUTARS distal femur replacement or proximal tibia replacement (Implantcast GmbH, Buxtehude, Germany). We collected general patients’ data, rang of motion, determined the Toronto extremity selvage score (TESS), musculoskeletal tumour society score (MSTS), knee society score (KSS) and Western Ontario MacMaster questionnaire (WOMAC) Score. Knee extension and flexion force was measured.Results:We included 59 patients with a mean age of 65+/-20 years. Out of these we had 19 (32%) male and 40 (68%) female patients. Mean follow up (f/up) was 36+/-57 month (range: 1-218).Indication for R-TKA was periprosthetic fractures (n=14), tumour (n=16), infection (n=10), traumatic fracture (n=14), aseptic loosening (n=3) and pathologic fracture (n=2). Indication for primary implantation was given in 33 (56%) patients and for implantation in case of revision surgery in 26 (44%) patients. Mean TESS was 66+/-33, mean MSTS was 14+/-7, mean KSS was 49+/-30, mean WOMAC was 36+/-26.Mean flexion on the operated side was 83°+/-24° compared to the healthy side (115°+/-20°) (p<0.001). Mean extension force on the operated side at 60° was 20+/-12 (Nm) compared to 77+/-58 (Nm) on the not operated side (p=0.31). Mean flexion force on the operated side at 60° was 32+/-26 (Nm) compared to 53+/-42 (Nm) on the not operated side (p=0.43). In case of revision surgery significant worse function scores in the TESS and KSS could be overserved (both p<0.05).Conclusion:Implantation of a distal femur- and/or proximal tibia replacement are associated with loss of flexion, a trend to reduced extension and flexion power compared to the contralateral side. In case of primary surgery better functional results in terms of function Scores can be expected than in case of revision surgery.

Decreased ankle and hip isometric peak torque in young and middle-aged adults with chronic ankle instability

ObjectivesTo compare ankle, knee and hip isometric peak torque between young and middle-aged adults with CAI, copers and un-injured controls. DesignCross-sectional. SettingResearch Laboratory. ParticipantsOne hundred fifty-six young and middle-aged adults with or without CAI volunteered. Main outcome measuresA handheld dynamometer measured isometric dorsiflexion, plantarflexion, knee extension, hip extension and hip abduction peak force during a 5 s trial. Average peak torque was calculated and normalized to body mass. ResultsA significant Age by Injury interaction for dorsiflexion suggest middle-aged un-injured controls (p < 0.001) and copers (p < 0.001) had lower isometric peak torque compared to their young adult counterparts, but there were no differences between young and middle-aged adults with CAI (p > 0.05). Significant Injury main effects suggest the CAI group had decreased plantarflexion (p = 0.004) and hip extension (p = 0.010) strength compared to un-injured controls, but not copers (p > 0.05). Significant Age main effects for all primary outcome measures were observed, indicating peak torque decreased with age (p < 0.05). ConclusionsRegardless of age, isometric ankle and hip peak torque was lower in participants with CAI compared to un-injured controls, but not copers. These findings provide further evidence towards the impact of CAI in both young and middle-aged adults.

Force control characteristics for generation and relaxation compared between the upper and lower limbs

We investigated the characteristics for force generation and relaxation compared between upper and lower limb. Participants were instructed to control the force of isometric elbow flexion or knee extension as quickly and accurately as possible. They performed the following two tasks: 1) Generation task, they increased their force from 0% maximum voluntary force (MVF) to 20%, 40%, or 60% MVF, 2) Relaxation tasks, they decreased their force from 60% MVF to 40%, 20%, or to 0% MVF. As a result, variable error of upper limb was greater than that of lower limb at all magnitudes in generation task. The peak rate of force development was greater in lower limb than in upper limb at all magnitudes in both tasks. The results indicate that it is more difficult to control relaxation of force accurately by upper limb than by lower limb under conditions that involve forces with low magnitude of control.