Knee Extensor Torque Research Articles

The Effect of Protein Supplementation and Playing Time on Recovery Kinetics During a Congested Basketball Schedule.

Despite being widely promoted, protein supplementation's overall effectiveness during demanding basketball schedules remains unclear. This study investigated whether increased protein intake can accelerate recovery of muscle function during a 6-day congested basketball microcycle consisting of three consecutive games while accounting for the impact of playing time. In a randomized, two-trial, cross-over, double-blind repeated measures design, eighteen male basketball players were assigned to a high (High PT) or a moderate (Mod PT) playing time group and participated in two trials, receiving daily either milk protein (PRO trial) or an isoenergetic amount of carbohydrates. Each trial included three consecutive games (days 1-3) and a 72 h recovery period following Game 3 (days 4-6), during which players participated in low-load practice sessions. Isometric and isokinetic peak torque of knee extensors and flexors in the dominant limb, serum creatine kinase (CK) concentration, and erythrocyte glutathione (GSH) levels were assessed prior to each game and practice session. CK increased (p < 0.01) on game days in both groups but recovered earlier in Mod PT compared to High PT. Both eccentric and concentric peak torque was impaired (p < 0.01) up to 24-48 h post-G3 in a velocity-dependent manner. Eccentric peak torque of knee flexors at 60°/s declined to a greater extent in High PT compared to Mod PT (p < 0.01). Protein supplementation resulted in higher erythrocyte GSH concentration at pre-G2 (p < 0.05) and pre-G3 (p < 0.05) compared to placebo in both groups but did not affect any of the study outcomes. Increased protein intake during a congested basketball schedule increases erythrocyte GSH concentration but does not accelerate recovery of muscle function.

Effects of Off-Season Heavy-Load Resistance Training on Lower Limb Mechanical Muscle Function and Physical Performance in Elite Female Team Handball Players.

Background/Objectives: Team handball involves a high number of rapid and forceful muscle actions. Progressive heavy-load resistance training is known to enhance mechanical muscle function; however, its transfer into functional performance in team handball athletes remains largely unknown. The current study aimed to analyze the effects of eight weeks undulating heavy-load resistance training on lower limb mechanical muscle function and sports-specific performance in elite female team handball players. Methods: Players from the Danish Women's Handball League were block randomized to perform an off-season resistance training program (RT, n = 12, 23.0 ± 2.7 yr) or follow a training-as-usual control program (CON, n = 15, 24.1 ± 3.8 yr). All study participants were tested before and after an eight-week period during the off-season phase, including assessments of maximal isometric knee extensor and flexor peak torque, rate of torque development, countermovement jump (CMJ) power/work, and sports-specific performance (maximal vertical countermovement jump height, sprint capacity, team handball-specific on-court agility). Results: Agility performance improved for RT (-3.5%, p = 0.008), different from CON (p < 0.001) following eight weeks of designated resistance training. Additionally, CON demonstrated impaired agility (+4.0-7.3%, p < 0.05) and 20-m sprint (+1.9%, p = 0.002) performance. Maximal knee extensor peak torque increased in RT (4.5%, p = 0.044). Vertical CMJ flight height (JH) increased in both groups (RT +4.8%, p = 0.012, CON +8.4% p = 0.044); however, jump height relative to ground level (JHGL) increased in RT only (+8.0%, p = 0.013). Conclusions: In conclusion, designated resistance training during the off-season period is effective in maintaining and improving essential components of sports-specific performance and maximal knee extensor strength in elite female team handball players. Comparable protocols of twice-a-week heavy-load resistance training may also be beneficial in other types of intermittent elite team sports (i.e., football, basketball) that include maximal jumping actions, short-distance sprints, and rapid change of direction movements.

Decreased Knee Extensor Torque During Single-Limb Stance: A Computer Simulation Study of Compensations and Consequences

Background/Objectives: For over 50 years, it has been suggested that the plantar flexors and hip extensors can compensate for weak knee extensors and prevent collapse of the leg during a single-limb stance. However, the effects of these compensations have not been studied thoroughly. The purpose of this computer simulation study was to determine, for a given posture, the hip and ankle net joint torque (NJT) required to prevent leg collapse due to systematic decreases in knee NJT and to determine the effect of these compensations on the horizontal ground reaction force. Methods: Single-limb stance was simulated using a static, multisegmented model in eight different postures. For each posture, the knee NJT was systematically decreased. The ankle and knee NJT necessary to prevent lower extremity collapse, along with any net horizontal ground reaction forces, were then calculated. Results: Decreases in knee NJT required linear increases in ankle and hip NJT to prevent the limb from collapsing. There were greater increases in ankle NJT compared to hip NJT, resulting in posteriorly-directed horizontal ground reaction forces. While the magnitudes were different, these findings applied to all postures simulated. Conclusions: For a given posture, ankle and hip NJTs can compensate for a decrease in knee NJT. However, this resulted in a horizontal ground reaction force, which was in the posterior direction for all the postures examined. This horizontal ground reaction force would induce an acceleration on the body’s center of mass that, if not accounted for, could have deleterious effects on achieving a task objective.

Associations between skeletal muscle phenotype, positional role, and on-ice performance in elite male ice hockey players.

We evaluated associations between muscle phenotype, positional role, and on-ice performance in male U20 Danish national team ice hockey players. Sixteen players (10 forwards, six defensemen) participated in a game with activity tracking. Resting thigh muscle biopsies were analyzed for metabolic enzyme activity and protein expression linked to performance. On-ice intermittent exercise capacity, repeated sprint ability, and maximal isometric knee-extensor torque were also assessed. No significant position-specific muscle phenotype characteristics were found, but forwards generally exhibited higher levels of several membrane proteins (p = 0.100-0.991). NAKα2, NAK∑, KATP, ClC-1, and NHE1 showed significant correlations with total distance (r = 0.52-0.59, p = 0.016-0.046), however, within positions these only persisted for KATP (r = 0.70, p = 0.024) and NAKα2 (r = 0.57, p = 0.085) in forwards, where CS enzyme activity also displayed a strong association with distance covered (r = 0.75, p = 0.019). For high-intensity skating, NAKα2 (r = 0.56, p = 0.025) and KATP (r = 0.50, p = 0.048) similarly exhibited the strongest associations, persisting within forwards (r = 0.63, p = 0.052 and r = 0.72; p = 0.018, respectively). In conclusion, although several muscle proteins involved in ion and metabolic regulation were associated with performance, only NAKα2 and KATP displayed consistent relationships within positions. Moreover, CS enzyme activity was strongly related to total distance within forwards, coherent with the proposed importance of oxidative capacity in intense intermittent exercise.

Effects of repetitive peripheral magnetic stimulation on knee joint extensor strength in older persons receiving day services.

To verify the effects of repetitive peripheral magnetic stimulation (rPMS) on knee joint extensor strength and motor ability in older adults receiving day services. Thirty Hz rPMS using Talent Pro® was applied to the bilateral vastus lateralis, vastus medialis, and rectus femoris of 12 older persons (mean age 83.8 ± 4.5 years) attending a day service center and receiving functional training by a physical therapist. The intervention was performed for 20 minutes per day, three times per week, for a total of 4 weeks. Evaluations before and after the intervention included maximum voluntary contraction (MVC), knee extensor torque induced by rPMS (rPMS-induced torque), pain (visual analog scale: VAS), thigh circumference, comfortable 5-m walking time, 30-second chair-stand test (CS-30), Timed-Up-and-Go Test (TUG), and Functional Reach Test (FRT). MVC and rPMS-induced torque were measured using the μ-Tas F-1®. MVC significantly increased in both lower limbs after the intervention (right/left: 72.4 ± 23.5 Nm/72.9 ± 23.0 Nm) compared with immediately before the intervention (right/left: 59.9 ± 17.2 Nm/64.5 ± 21.0 Nm). No significant changes were observed in MVC between one month before the intervention and immediately before the start of the intervention, and between the end of the intervention and one month after the end of the intervention. rPMS-induced torque, TUG, and CS-30 improved significantly after the intervention compared with immediately before the intervention. Intervention using rPMS increases MVC- and rPMS-induced torque and improves motor ability in older adults. Because rPMS is a simple means of increasing muscle strength, it is expected to be widely used in the future.

Sex Differences Exist in the Relationship Between Vertical Jump Performance Biomechanical Parameters and Hamstring/Quadriceps Ratio in Adolescent U18 Track and Field Athletes.

Isokinetic metrics are suggested to be related to vertical jump performance, but little is known about the possible sex differences in this relationship in adolescent track and field athletes. The aim of the study was to examine the possible sex differences in the strength of the relationship between the kinetic parameters of the vertical squat jump with arms akimbo, the countermovement jump with arms akimbo, and the countermovement jump with free arm swing with the isokinetic parameters of the knee extensor and flexor muscles (angular velocities: 60°/s and 300°/s). In total, 35 (males: 21, females: 14) U18 track and field athletes were examined. The results revealed that the Men U18 group had higher vertical jump performance, higher values in the kinetic parameters of the vertical jump tests, higher knee extensor torque, and higher knee flexor torque in the non-dominant leg compared to the Women U18 group. Significant (p < 0.05) sex differences were observed in the relationship between the isokinetic parameters and the vertical jump performance metrics, as the Women U18 athletes relied more on the knee flexor torque than Men U18 athletes, and demonstrated a stronger negative relationship between selected isokinetic metrics and the pre-stretch gain in the vertical jump tests. In conclusion, it is recommended that young female track and field athletes minimize interlimb asymmetry and improve the convention ratio in their non-dominant leg to optimize vertical jump performance.

Relative muscular effort in the older adults during the sit-to-stand task: Monitoring neuromuscular reserve and movement limitations

BackgroundDue to lower maximum strength, older adults purportedly need to exert greater muscular effort to stand up from a chair. This study investigated joint-specific muscular effort during a sit-to-stand by calculating relative-muscular-effort and investigating differences between healthy older and young adults. MethodsFifteen older (age: 69.9 ± 3.5 years) and 15 young (age: 22.2 ± 2.6 years) adults performed five self-paced sit-to-stand trials. Kinematic and kinetic data were collected and used to calculate inverse dynamics net joint moment. Peak isometric knee and hip extensor torques were measured and used as inputs to regression models that predicted angle- and velocity-dependent maximum potential net joint moment. Knee and hip relative-muscular-effort were calculated as the net joint moment during the task and their maximum capacity. FindingsKnee and hip extensor relative-muscular-effort did not differ between age groups during momentum-transfer and extension phases of the sit-to-stand. However, peak knee and hip moments during the sit-to-stand, knee and hip maximum potential moments as well as peak knee and hip torques were significantly lower in older adults compared to young adults. InterpretationAlthough there were age-related decreases in muscle strength and joint kinetics during the sit-to-stand task in older adults, the findings that older adults exhibited similar knee and hip relative-muscular-effort to young adults suggests that neither knee nor hip extensors operated close to their maximum capacity during this task. Therefore, neuromuscular reserve in knee and hip strength may not be a critical limiting factor for healthy older adults during the two phases of sit-to-stand.

Females demonstrate lower levels of activity, psychological readiness and strength symmetry after anterior cruciate ligament reconstruction than males, and also recovery of quadriceps strength and hop symmetry is delayed in females undergoing reconstruction with a quadriceps tendon autograft.

To investigate sex-based recovery differences in patients undergoing anterior cruciate ligament reconstruction (ACLR) with a hamstring (HT) or quadriceps (QT) tendon autograft. This study included 97 patients, including 50 females (HT = 25, QT = 25) and 47 males (HT = 24, QT = 23), assessed presurgery and at 12- and 24-month postoperatively via surveys, laxity, isokinetic knee extensor and flexor torque and a 6-hop performance battery. Limb symmetry indices (LSIs) were calculated. Outcomes were compared between males and females, as well as within each graft type. Males reported significantly higher Tegner scores at 12 (p = 0.029) and 24 (p = 0.031) months, Anterior Cruciate Ligament Return to Sport after Injury scores at 12 (p = 0.009) and 24 (p = 0.010) months, and a significantly higher lateral hop LSI at 12 (p = 0.045) months, knee extensor torque LSI at 12 (p = 0.020) months, and knee flexor torque LSI at 12 (p = 0.001) and 24 (p = 0.039) months. Females undergoing ACLR with a QT (vs. HT) graft demonstrated a lower knee extensor torque LSI at 12 (p = 0.006) months, a lower lateral hop LSI at 12 (p = 0.038) months, and a lower medial hop LSI at 12 (p = 0.042) months. Females reported less activity and psychological readiness, as well as strength symmetry. Furthermore, the recovery of quadriceps strength and hop symmetry was delayed in females (vs. males) undergoing ACLR with a QT graft. A better understanding of these differences will assist in counselling on expectations, determining the most appropriate graft construct and permitting more targeted rehabilitation. Level IV.

Alpha band oscillations in common synaptic input are explanatory of the complexity of isometric knee extensor muscle torque signals.

We investigated whether the strength of oscillations in common synaptic input was explanatory of knee extensor (KE) torque signal complexity during fresh and fatigued submaximal isometric contractions, in adults aged from 18 to 90years. The discharge times of motor units were derived from the vastus lateralis muscle of 60 participants using high-density surface EMG, during 20s isometric KE contractions at 20% of maximal voluntary contraction, performed before and after a fatiguing repeated isometric KE contraction protocol at 60% of maximal voluntary contraction. Within-muscle coherence Z-scores were estimated using frequency-domain coherence analysis, and muscle torque complexity was assessed using multiscale entropy analysis and detrended fluctuation analysis. Alpha band (5-15Hz) coherence was found to predict 23.1% and 31.4% of the variance in the complexity index under 28-scales (CI-28) and detrended fluctuation analysis α complexity metrics, respectively, during the fresh contractions. Delta, alpha and low beta band coherence were significantly increased due to fatigue. Fatigue-related changes in alpha coherence were significantly predictive of the fatigue-related changes in CI-28 and detrended fluctuation analysis α. The fatigue-related increase in sample entropy from scales 11 to 28 of the multiscale entropy analysis curves was significantly predicted by the increase in the alpha band coherence. Age was not a contributory factor to the fatigue-related changes in within-muscle coherence and torque signal complexity. These findings indicate that the strength of alpha band oscillations in common synaptic input can explain, in part, isometric KE torque signal complexity and the fatigue-related changes in torque signal complexity.

Knee muscle strength and steadiness for individuals with anterior cruciate ligament reconstruction and knee osteoarthritis

BackgroundStrength and neuromuscular decrements following knee musculoskeletal injury may accelerate knee osteoarthritis development. This study assessed isometric knee extensor and flexor strength and steadiness between individuals with knee injury, i.e., ligament reconstruction, and knee osteoarthritis to healthy age-matched controls. MethodsFour cohorts (1: knee injury and 2: age-matched controls, and 3: radiographic knee osteoarthritis and 4: age-matched controls) were recruited. Participants performed maximal voluntary isometric knee extensor and flexor contractions. Then, strength (e.g., peak and rate of torque development) and steadiness (e.g., peak power, mean, and median frequency) were derived from each raw torque-time curve and associated power spectral density. A Kruskal-Wallis H test and Spearman's rho correlation analysis assessed cohort differences and association between knee extensor and flexor strength and steadiness. FindingsThe young adult control and knee injury cohorts exhibited greater knee extensor and flexor strength than the older, knee osteoarthritis cohort (p < 0.043). The knee injury cohort, despite being as strong as their healthy counterparts, were significantly less steady with a 92% increase in peak power frequency (p = 0.046). The osteoarthritis cohort exhibited 157% less total power compared to the knee injury and young control cohorts (p < 0.019). Knee extensor and flexor peak torque, rate of torque development, and mean torque exhibit a significant, positive relation with total power (p < 0.018). InterpretationIndividuals with knee injury and disease may exhibit weaker or less steady knee musculature, predisposing them to degenerative joint disease. Clinicians may need to restore knee extensor and flexor steadiness to facilitate better joint neuromuscular control.

Clinical and Radiological Outcomes at ≥10-Year Follow-up After Matrix-induced Autologous Chondrocyte Implantation in the Patellofemoral Joint

Background: Matrix-induced autologous chondrocyte implantation (MACI) has demonstrated encouraging outcomes in the treatment of knee cartilage defects, although limited research is available on its longer term (≥10 years) sustainability in the patellofemoral joint. Purpose: To report the clinical and radiological outcomes at ≥10 years in a prospectively recruited cohort of patients undergoing MACI in the patellofemoral joint and compare outcomes in patients undergoing MACI on the patella versus the trochlea. Study Design: Case series; Level of evidence, 4. Methods: The current study prospectively enrolled 95 patients who underwent patellofemoral MACI, of whom 29 (13 patella, 16 trochlea) underwent concomitant tibial tubercle osteotomy. Patients were assessed preoperatively and at 2, 5, and ≥10 years using a range of patient-reported outcome measures (PROMs) including the Knee injury and Osteoarthritis Outcome Score, the 36-item Short Form Health Survey, and the frequency and severity of knee pain as well as patient satisfaction, full active knee flexion and extension, and peak isokinetic knee extensor and flexor torques. High-resolution magnetic resonance imaging (MRI) was performed to assess pertinent graft parameters, as well as determine an overall MRI composite score, per the Magnetic Resonance Observation of Cartilage Repair Tissue scoring system. Results were analyzed according to the graft location (patella or trochlea). Results: Of the 95 patients recruited, 82 patients (41 patella, 41 trochlea) were available for a clinical review at ≥10 years after surgery (mean follow-up, 11.9 years [range, 10-15 years]). For the whole patellofemoral MACI cohort, all PROMs significantly improved over time (P < .05), with no significant changes (P > .05) observed in any MRI-based score from 2 to ≥10 years after surgery. At ≥10 years, 90.2% (n = 74) were satisfied with MACI in relieving their knee pain, and 85.4% (n = 70) were satisfied with the improvement in their ability to participate in sports. No differences (P > .05) were observed in PROMs between those undergoing patellar MACI and those undergoing trochlear MACI, although a significant group effect was observed for limb symmetry indices of knee extensor (P = .009) and flexor (P = .041) strength, which were greater in those undergoing patellar (vs trochlear) MACI. No statistically significant differences (P > .05) were observed between patellar and trochlear grafts on any MRI-based measure. In the cohort assessed at ≥10 years after surgery, 4 patients (2 patella, 2 trochlea) demonstrated graft failure on MRI scans, although a further 3 patients (all trochlea) were omitted from the ≥10-year review for having already progressed to total knee arthroplasty. Conclusion: Good clinical scores, high levels of patient satisfaction, and adequate graft survivorship were observed at ≥10 years after MACI on the patella and trochlea.

Peak Oxygen Uptake is Slope Dependent: Insights from Ground Reaction Forces and Muscle Oxygenation in Trained Male Runners

BackgroundThe aim of this study is to explore the effect of treadmill slope on ground reaction forces and local muscle oxygenation as putative limiting factors of peak oxygen uptake in graded maximal incremental running tests. Thirteen trained male runners completed five maximal incremental running tests on treadmill at − 15%, − 7.5%, 0%, 7.5% and 15% slopes while cardiorespiratory and local muscle oxygenation responses as well as ground reaction forces were continuously recorded. Blood lactate concentration and isometric knee extensor torque were measured before and after each test.ResultsPeak oxygen uptake was lower at − 15% slope compared to all other conditions (from − 10 to − 17% lower, p < 0.001), with no difference between − 7.5 and + 15% slope. Maximal heart rate and ventilation values were reached in all conditions. The negative external mechanical work increased from steep uphill to steep downhill slopes (from 6 to 92% of total external work) but was not correlated with the peak oxygen uptake reduction. Local muscle oxygenation remained higher in − 15% slope compared to level running (p = 0.003).ConclusionsSimilar peak oxygen uptake can be reached in downhill running up to − 7.5% slope. At more severe downhill slopes (i.e., − 15%), greater negative muscle work and limited local muscle deoxygenation occurred, even in subjects familiarized to downhill running, presumably preventing the achievement of similar to other condition’s peak oxygen uptake.Key PointsTrained male runners can reach like level running V̇O2peak at moderate but not at severe negative slope.Negative external mechanical work increases with increasing negative slope.At maximal intensity Vastus Lateralis muscle oxygenation is higher in steep negative slope.Knee extensor isometric muscle torque is preserved after maximal level and uphill running, but reduced after downhill running, despite lower blood lactate.Progressive reduction of V̇O2 at maximal effort with increasing negative slope might be related to the metabolic consequences of increased lower limb negative external work (i.e., eccentric muscle actions).

Modern multiligament knee injury surgical reconstruction techniques can achieve excellent knee function and patient satisfaction, with low complication rates.

To report on the recovery of strength and functional capacity symmetry following multiligament knee surgical reconstruction (MLKR), as well as the capacity of athletes to return to sport. This prospective cohort study recruited 47 patients undergoing MLKR between February 2018 and July 2021. Forty patients had full outcome assessment postoperatively at 6, 12 and 24 months and were included in the analysis, 75% were knee dislocation one injuries and 60% were injured playing sport. Patient-reported outcome measures (PROMs) assessed included the International Knee Documentation Committee score, the Knee Outcome Survey, the Lysholm Knee Score and the Tegner Activity Scale (TAS). Patient satisfaction was also assessed. Objective assessment included assessment of active knee flexion and extension range of motion (ROM), the single (single horizontal hop for distance [SHD]) and triple (triple horizontal hop for distance [THD]) hop tests for distance and peak isokinetic knee flexor/extensor torque. All PROMs significantly improved (p < 0.001) from presurgery to 24 months postsurgery. At 24 months, 70% of patients were satisfied with their sports participation. Active knee flexion (p < 0.0001) and extension (p < 0.0001) ROM significantly improved over time, as did the limb symmetry indices (LSIs) for the SHD (p < 0.0001), THD (p < 0.0001), peak knee extensor (p < 0.0001) and flexor (p = 0.012) torque. While LSIs for the SHD, THD and knee flexor strength tended to plateau by 12 months, knee extensor strength continued to improve from 12 to 24 months. The majority of patients undergoing modern MLKR surgical techniques and rehabilitation can achieve excellent knee function, with low complication rates. Level IV.

Poster 227: Prospective Clinical and Radiological Follow-Up Beyond 10 Years in Patients Undergoing Matrix-Induced Autologous Chondrocyte Implantation (MACI) in the Patellofemoral Joint

Objectives: Matrix-induced autologous chondrocyte implantation (MACI) has demonstrated encouraging outcomes in the treatment of knee cartilage defects, though limited research is available on its longer-term (≥10 years) sustainability in the patellofemoral joint. This prospective study sought to present and report the clinical and radiological outcome beyond 10 years in a prospectively recruited cohort of patients undergoing MACI in the patellofemoral knee joint. Methods: The current study included 82 patients (patella = 41, trochlea = 41) assessed at ≥10 years following patellofemoral MACI. Patients were assessed preoperatively and at 2, 5 and ≥10 years via the Knee Injury and Osteoarthritis Outcome score (KOOS), the 36-item Short Form Health Survey (SF-36), the frequency (VAS-F) and severity (VAS-S) of knee pain, patient satisfaction, active knee range of motion (ROM) and peak isokinetic knee extensor and flexor torque. High-resolution magnetic resonance imaging (MRI) assessed pertinent measures of graft outcome as per the magnetic resonance observation of cartilage repair tissue (MOCART) system, as well as an overall MRI composite score. Results were analyzed according to the graft location (patella or trochlea). Results: While no statistically significant differences (p&gt;0.05) were observed between those undergoing patella or trochlea MACI across the majority of demographic (age, weight, BMI), injury history (duration of symptoms) or surgery (defect size, prior procedures, requirement for concomitant patellofemoral re-alignment) variables, a significantly higher (p=0.013) proportion of males was seen in the trochlea MACI group. All patient-reported outcome measures significantly improved (p&lt;0.05), with no differences observed between those undergoing patella or trochlea MACI. No group differences (p&gt;0.05) were observed in active knee flexion or extension ROM between groups, though those undergoing patella (versus trochlea) MACI demonstrated significantly greater postoperative quadriceps (Figure 1) and hamstring strength limb symmetry indices. No statistically significant decline (p&gt;0.05) was seen from 2 years to final follow-up in any MRI-based measure, with no MRI-based differences observed between patella (Figure 2) and trochlea (Figure 3) grafts. In the cohort assessed at ≥10 years post-surgery, 4 patients (patella n=2, trochlea n=2) demonstrated graft failure on MRI, though a further 3 patients (all trochlea) were omitted from ≥10-year review that had already progressed toward total knee arthroplasty. Conclusions: Good clinical scores, high levels of patient satisfaction and adequate graft survivorship were observed at ≥10 years following MACI to the patella or trochlea.

Knee Extensor Torque Steadiness and Quadriceps Activation Variability in Collegiate Athletes 4, 6, and 12 Months After ACL Reconstruction.

Quadriceps performance after anterior cruciate ligament reconstruction (ACLR) is typically characterized by peak force/torque, but the ability to generate consistent knee extensor torque may be clinically meaningful. The purpose of this study was to evaluate knee extensor torque steadiness and quadriceps activation variability in collegiate athletes 4 to 12 months after ACLR. It was hypothesized that between-limb asymmetries in torque steadiness and activation variability would be observed and that steadiness would be associated with activation variability and peak knee extensor torque symmetry. Case-control study; Level of evidence, 3. A total of 30 National Collegiate Athletic Association Division I athletes completed maximal voluntary isometric contractions 4, 6, and 12 months after ACLR. Torque and surface electromyography of the superficial quadriceps were recorded. Torque steadiness was calculated as the mean difference between initial and low-pass filtered torque signals and was expressed as a percentage of peak torque. Quadriceps activation variability was calculated similarly and was expressed as a percentage of peak electromyography. Linear mixed models were used to assess change in torque steadiness and activation variability over time. Associations between torque steadiness of the operated limb, activation variability, and quadriceps strength symmetry were evaluated using the Spearman correlation coefficient. Limb-by-time interactions were detected for torque steadiness and activation variability (P < .001), with reductions (improvements) in limb steadiness and activation variability observed with increasing time since surgery. Between-limb differences in torque steadiness and activation variability were observed at 4 and 6 months postoperatively (P < .05). Significant associations between operated limb torque steadiness and quadriceps activation variability were observed at 4 months (P < .001) and 6 months (P < .01). Torque steadiness of the operated limb was associated with peak knee extensor torque symmetry at 4 months (r S = -0.49; P < .01) and 6 months (r S = -0.49; P < .01). In collegiate athletes, impaired knee extensor torque steadiness of the operated limb and associated abnormal quadriceps activation patterns were observed 4 to 12 months after ACLR, and the consistency of knee extensor torque production was associated with greater quadriceps strength asymmetries, particularly 4 to 6 months after surgery. Operated limb torque steadiness and activation variability improved from 4 to 12 months after ACLR. Clinical assessment of knee extensor torque steadiness after ACLR may improve prognosis and specificity of rehabilitation efforts.

Effect of Step Load Based on Time under Tension in Hypoxia on the ACL Pre-Operative Rehabilitation and Hormone Levels: A Case Study.

The aim of the study was to determine the effect of step load in hypoxia on the effectiveness of preoperative rehabilitation (PR) and hormone levels based on a case study. Introduction: We assessed the impact of variables such as rate of movement and time under tension (TUT) in normobaric hypoxia on the levels of growth hormone (GH), insulin-like growth factor 1 (IGF-1), and erythropoietin (EPO). Additionally, the impact of step load on the hypertrophy and strength of knee extensors and flexors was assessed. Methods: The work uses a case study, the research subject of which was a 23-year-old female professional handball player. The tests included an isokinetic assessment of the peak torque of knee extensors and flexors as well as body composition analysis. Results: The results showed a more than (10.81-fold) increase in GH after the microcycle with time under tension (TUT). The deficit between the lower limbs was also reduced. Conclusions: Using a hypoxic environment based on an appropriate altitude, combined with changes such as a short rest break between sets and a controlled tempo of movement with an eccentric phase, TUT may offer an alternative to the PR process, especially among athletes who care about fast RTS.

Measurement of Knee Extensor Torque During Repetitive Peripheral Magnetic Stimulation: Comparison of the Forces Induced by Different Stimulators.

To investigate the factors that induce strong contractions during repetitive peripheral magnetic stimulation (rPMS) and compare the muscle torque induced by two stimulators (Stim A and Stim B) with different coil properties. rPMS was applied to the right vastus lateralis of 30 healthy young adults. Stim A contained a 10.1 cm2 rectangular iron core coil, while Stim B contained a 191 cm2 round coil. The knee extensor torque (KET) induced by rPMS at 30 Hz was measured isometrically and divided by the maximum voluntary contraction (MVC) to obtain a relative value of MVC (%MVC). KET at 100% intensity of Stim A (A100%, 1.08 T) was compared to those at 100% or 70% intensity of Stim B (B100%, 1.47 T vs. B70%, 1.07 T). Additionally, we conducted a comprehensive literature search for studies that measured the KET during rPMS. Both the mean values of %MVC using B100% and B70% were significantly greater than that using A100%. Furthermore, the KET induced by Stim B was found to be larger than that described in previous reports, unless booster units were used to directly stimulate the main trunk of the femoral nerve. Stim B induced a stronger muscle contraction force than Stim A did. This may be because the larger the coil area, the wider the area that can be stimulated. Additionally, a circular coil allows for deeper stimulation.

A RANDOMIZED CONTROLLED TRIAL EVALUATING AN ACCELERATED WEIGHT-BEARING REHABILITATION PATHWAY AFTER MATRIX-INDUCED AUTOLOGOUS CHONDROCYTE IMPLANTATION FOR SYMPTOMATIC KNEE CARTILAGE DEFECTS

INTRODUCTION &amp; AIMS Matrix-induced autologous chondrocyte implantation (MACI) has demonstrated encouraging outcomes in treating symptomatic knee cartilage lesions which, if untreated, can progress toward early osteoarthritis. Rehabilitation is imperative to optimize outcome, though has been traditionally conservative. This study investigated the long-term outcomes of an accelerated return to full weight bearing (WB) after MACI. METHODS This prospective randomized controlled trial (RCT) allocated 35 patients (37 knees) to a 6-week (n=18) or 8-week (n=19) return to full WB after MACI. Patients were evaluated pre-operatively and at 1, 2, 5 and ≥10 years, via patient-reported outcome measures (PROMs) including the Knee Osteoarthritis Outcome Score (KOOS). Single limb hop capacity and peak knee extensor and flexor torque were assessed, with limb symmetry indices (LSIs) calculated. Magnetic resonance imaging (MRI) evaluated repair tissue, while a validated MRI composite graft score was calculated. RESULTS While the 6-week WB group reported significantly better 1-year KOOS Quality of Life scores, no other differences (p&amp;gt;0.05) in PROMs existed. The peak knee extensor torque LSI significantly improved (p&amp;lt;0.0001) over time, with mean LSIs of 100.8 (6-week) and 99.1 (8-week) at ≥10 years. No group differences (p&amp;gt;0.05) were observed in hop LSIs. A non-significant decline (p&amp;gt;0.05) was observed for the MRI composite score from 1-year to final ≥10-year review and, apart from a significant group effect (p=0.028) for graft tissue intensity in favor of the 6-week group suggesting repair tissue more reflective of native cartilage, no other MRI-based differences (p&amp;gt;0.05) existed. At ≥10-years, no grafts on MRI had failed, though 3 patients (6-week n=1, 8-week n=2) had progressed toward knee arthroplasty. CONCLUSION The 6-week accelerated rehabilitation program provided comparable clinical and MRI-based outcomes beyond 10 years post-surgery, without jeopardizing the graft.

AN INVESTIGATION OF SEX-BASED DIFFERENCES IN PHYSICAL AND PSYCHOLOGICAL RECOVERY, AND RETURN TO SPORT, FOLLOWING ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

INTRODUCTION &amp; AIMS Despite the increasing rate of anterior cruciate ligament (ACL) tears and surgical reconstruction (ACLR), little is known about the post-operative recovery in males versus females. Understanding differences in the recovery between sexes will assist in better tailoring rehabilitation, return to sport (RTS) and counselling pathways. This study investigated sex-based differences in the physical and psychological recovery of both females and males after ACLR. METHODS This study recruited 104 patients (49 females, 55 males) undergoing ACLR. Patients were assessed pre-operatively and at 6, 12 and 24 months post-surgery, via patient-reported outcome measures (PROMs) including the International Knee Documentation Committee (IKDC) form, the Tegner Activity Scale (TAS) and the Anterior Cruciate Ligament Return to Sport after Injury (ACL-RSI) score. Patients embarked on an assessment of peak isokinetic knee extensor (PKET) and flexor (PKFT) torque and a 4-hop performance battery. Limb Symmetry Indices (LSIs) were calculated. The incidence of RTS was investigated. RESULTS All PROMs significantly improved (p&amp;lt;0.05), though females reported significantly lower ACL-RSI (p=0.002) and IKDC (p=0.007) scores. While no sex-based differences were observed in hop test LSIs, males demonstrated significantly higher mean LSIs for PKET at 6 (p=0.037) and 24 (0.047) months, and PKFT at 6 (p=0.007) and 12 (p=0.002) months. At 24-months post-surgery, a significantly greater (p=0.030) percentage of male patients had returned to pivoting sports. CONCLUSION This study demonstrates the disparity between sexes in physical and psychological recovery, as well as RTS status, in community-level patients undergoing ACLR. The development and implementation of enhanced post-operative patient-centered care may be warranted tailored to sex, encompassing rehabilitation, education, and counseling after ACLR to promote increased engagement in rehabilitation.

A RANDOMIZED CONTROLLED TRIAL ASSESSING A BRACE-FREE AND ACCELERATED WEIGHT-BEARING PROTOCOL AFTER SURGICAL REPAIR OF ACUTE PROXIMAL HAMSTRING TENDON AVULSIONS

INTRODUCTION &amp; AIMS Proximal hamstring tendon avulsion from the ischial tuberosity is a significant injury, with surgical repair advocated. After surgery, limited data exists regarding the optimal rehabilitation regime with extensive variation in published protocols. This study investigated patient outcomes following a traditionally conservative (CR) versus accelerated (AR) rehabilitation regimen after proximal hamstring tendon repair. METHODS This prospective randomized controlled trial (RCT) allocated 50 patients undergoing proximal hamstring tendon repair to either a braced, partial weight-bearing rehabilitation regime (CR=25) or an accelerated, unbraced regime, that permitted full weight-bearing as tolerated (AR=25). Patients were evaluated pre-operatively and at 3, 6 and 12 months post-surgery, via patient-reported outcome measures (PROMs) including the Lower Extremity Functional Scale (LEFS), Perth Hamstring Assessment Tool (PHAT) and 12-item Short Form Health Survey (SF-12). The single (SHD), triple (THD) and triple crossover (TCHD) hop tests were assessed at 6 and 12 months, as was peak isometric hamstring strength and peak isokinetic knee extensor and flexor torque. RESULTS All PROMs improved (p&amp;gt;0.05) and, while the AR group reported a significantly better Physical Component Score for the SF-12 at 3 months (p=0.022), as well as a lower severity of hamstring pain at 12 months (p=0.032), there were no other group differences. Peak isometric hamstrings strength and peak isokinetic quadriceps and hamstrings torque symmetry were all comparable between groups (p&amp;gt;0.05). While the AR group demonstrated significantly better (p=0.009) limb symmetry for the THD at 6 months, no other hop test differences were seen between groups. Three re-injuries have been observed (CR=2, AR=1). CONCLUSION After proximal hamstring repair surgery, post-operative outcomes following an accelerated rehabilitation regimen were largely comparable to a traditionally conservative