Knee Flexor Strength Research Articles

A structured accelerated versus control rehabilitation pathway after anterior cruciate ligament reconstruction using autologous hamstrings demonstrates earlier improvement in physical outcomes without increasing graft laxity: A randomized controlled trial

ObjectivesTo investigate whether an accelerated rehabilitation pathway could enhance strength and functional symmetry after ACLR, without affecting laxity. DesignRandomized Controlled Trial. SettingPrivate rehabilitation clinic. Participants44 patients randomized to an ‘Accelerated’ (n = 22) or ‘Control’ (n = 22) rehabilitation intervention. Main outcome measuresGraft laxity (primary outcome), isokinetic knee extensor and flexor strength, hop tests, surveys, sport participation, re-injuries and re-operations. ResultsNo knee laxity differences (p > 0.05) were observed. A significantly greater (p = 0.006) percentage of Accelerated (77.3%) versus Control (59.1%) patients were participating in Level 1 or 2 pivoting sports at 12 months. Greater limb symmetry indices were observed in the Accelerated group for knee extensor strength at 6 (p < 0.0001), 12 (p = 0.010) and 24 (p = 0.005) months, as well as the triple hop at 6 (p = 0.015) and 9 (p = 0.008) months, and the triple crossover hop at 6 (p < 0.0001) and 9 (p = 0.009) months. One ipsilateral re-tear was observed (Control group, 17 months). No differences (p˃0.05) existed in surveys apart from the Anterior Cruciate Ligament Return to Sport after Injury (ACL-RSI) score, better (p = 0.001) in the Accelerated group at 12 months. ConclusionsAccelerated rehabilitation produced earlier improvement in strength and hop LSIs, without increasing graft laxity.

Assessing gait, balance, and muscle strength among breast cancer survivors with chemotherapy-induced peripheral neuropathy (CIPN): study protocol for a randomized controlled clinical trial

BackgroundChemotherapy-induced peripheral neuropathy (CIPN) is a common and understudied consequence of taxane chemotherapy for breast cancer treatment. CIPN symptoms include numbness combined with tingling sensations, persistent shooting, stabbing, or burning pain even in the absence of painful stimuli, lower extremity muscle weakness, and impaired balance. CIPN symptoms often persist for a long time after completion of chemotherapy, causing significant loss of functional abilities and increased risk of falls. Persistent CIPN caused by taxanes represents a therapeutic challenge due to the limited treatment options. Resistance exercise has shown promising results; however, the effect of exercise on CIPN remains understudied. This study aims to assess the effects of exercise on gait, balance, and lower extremity muscle strength after a 16-week home-based exercise program compared to an educational attention control condition.MethodsA sample of 312 women who completed taxane-based chemotherapy for breast cancer and have symptomatic neuropathy is recruited from a community-dwelling sample. Participants are randomized to either a 16-week Home-Based Physical Activity Intervention or an Educational Attention control group. The home-based intervention protocol consists of targeted lower extremity stretches, followed by 10 min each of gait/balance and 10 min of resistive training accessed by hyperlink or DVD. An Exercise Diary records quantitative exercise data. The gait assessment includes temporospatial parameters and lower extremity joint angles using APDM motion sensors. Participants’ balance is assessed using the Sensory Organization Test (SOT) performed using a NeuroCom Balance Master. Isometric strength of hip, knee, and ankle flexor and extensor muscles is assessed using an isokinetic dynamometer, Biodex BX Advantage. In addition, we assess neuropathy symptoms using the FACT-Taxane Additional Concerns Subscale and nerve conduction velocity of the sural and peroneal nerve action potentials. Outcomes are assessed at baseline (prior to randomization) and 16 weeks.DiscussionThere are currently no evidence-based interventions that address the functional declines associated with CIPN. If successful, this program is simple and easy to implement in the standard of care for individuals with CIPN. Gait and balance training have the potential to reduce physical dysfunction associated with CIPN and reduce the burden of disease in cancer survivors.Trial registrationClinicalTrials.gov NCT04621721. Registered on August 3, 2020. ClincialTrials.gov is a primary registry of the World Health Organization International Clinical Trials Registry Platform (WHO ICTEP) network and includes all items from the WHO Trial Registration data set in Trial registration.

Comparison of bilateral isokinetic and isometric strength differences in elite young male and female taekwondo athletes.

Definition of strength imbalance between legs and muscles does not only play a decisive role for higher performance but also prevents sport injury. The purpose of this study was to determine bilateral differences on isokinetic and isometric strength of knee extensor and flexor muscles in male and female elite young taekwondo athletes. Ten male (age: 19.40±0.84 years) and female (age: 18.24±1.42 years) taekwondo athletes of the Turkish national team between 17–20-year of age participated in the study. Concentric peak torque of hamstring (H) and quadriceps (Q) of the dominant (D) and nondominant leg (ND) was evaluated using isokinetic machine (Cybex Humac Norm) at 60° and 180°/sec. Isometric peak torque of both legs was determined at 60°. Significant differences were found between genders (P<0.05). Concentric and isometric knee strength was significantly greater in male than that of female (P< 0.05). Although no significant bilateral strength difference was found in both sexes in concentric and isometric strength (P>0.05), and isometric H strength was in favor of the dominant leg 15% for men athletes and 11% for women. H/Q ratio was similar between gender and legs. The study revealed no bilateral knee strength asymmetry in both male and female taekwondo athletes. However, male had 20%–30% higher isometric and concentric knee extensor and flexor strength than female in both legs.

Shape differences in the semitendinosus following tendon harvesting for anterior cruciate ligament reconstruction.

Following hamstring autograft anterior cruciate ligament reconstruction (ACLR), muscle length, cross-sectional area, and volume are reduced. However, these discrete measures of morphology do not account for complex three-dimensional muscle shape. The primary aim of this study was to determine between-limb semitendinosus (ST) shape and regional morphology differences in young adults following tendon harvest for ACLR and to compare these differences with those in healthy controls. In this cross-sectional study, magnetic resonance imaging was performed on 18 individuals with unilateral ACLR and 18 healthy controls. Bilaterally, ST muscles were segmented, and shape differences assessed between limbs and compared between groups using Jaccard index (0-1) and Hausdorff distance (mm). Length (cm), peak cross-sectional area (cm2 ), and volume (cm3 ) were measured for the entire muscle and proximal, middle, and distal regions, and compared between limbs and groups. Compared to healthy controls, the ACLR group had significantly (p < 0.001, Cohen's d = -2.33) lower bilateral ST shape similarity and shape deviation was significantly (p < 0.001, d = 2.12) greater. Shape deviation was greatest within the distal region of the ACLR (Hausdorff: 23.1 ± 8.68 mm). Compared to both the uninjured contralateral limb and healthy controls, deficits in peak cross-sectional area and volume in ACLR group were largest in proximal (p < 0.001, d = -2.52 to -1.28) and middle (p < 0.001, d = -1.81 to -1.04) regions of the ST. Overall, shape analysis provides unique insight into regional adaptations in ST morphology post-ACLR. Findings highlight morphological features in distal ST not identified by traditional discrete morphology measures. Clinical significance: Following ACLR, risk of a secondary knee or primary hamstring injury has been reported to be between 2-to-5 times greater compared to those without ACLR. Change in semitendinosus (ST) shape following ACLR may affect force transmission and distribution within the hamstrings and might contribute to persistent deficits in knee flexor and internal rotator strength.

Musculoskeletal Asymmetry in Young Soccer Players: Differences between the Dominant and Nondominant Leg

The purpose of this investigation was to clarify the differences in the musculoskeletal profiles between the dominant leg (DL) and nondominant leg (NDL) of Japanese soccer players. This study included 227 young elite soccer players (121 males and 106 females with mean ages of 19.0 and 17.5 years, respectively). Anthropometric measurements were obtained. In addition, joint range of motion measurements was performed for internal rotation of the hip, ankle dorsiflexion, and knee extension. Muscle flexibility tests were performed on the iliopsoas, quadriceps femoris, hamstring, gastrocnemius, and soleus muscles. Moreover, isometric knee extension, flexion strength, and isometric hip abduction strength were measured. Single-leg balance tests were also performed. As a result, in male soccer players, DL's knee flexor strength and hip abductor strength were significantly stronger than in the NDL. In female soccer players, knee extension and knee flexion strength of the DL were significantly stronger than the NDL. In male soccer players, the hamstring-quadriceps ratio of the DL was significantly greater than NDL. DL demonstrated a significantly lesser center of pressure excursion in the single-leg balance test in male and female soccer players. In both male and female soccer players, the quadriceps muscle of DL was significantly more flexible than those of the NDL. There was no difference in the internal rotation angle of the hip joint between the DL and NDL in male soccer players. In contrast, the internal rotation angle of the DL was significantly (1.6°) greater than NDL in female soccer players. For some anthropometric measurements, muscle flexibility tests and joint range of motion measurements, the difference between the DL and NDL was significant but not large enough to be clinically relevant. In conclusion, the present study showed musculoskeletal asymmetry between the DL and NDL in young male and female soccer players.

The Dose-Response of the Nordic Hamstring Exercise on Biceps Femoris Architecture and Eccentric Knee Flexor Strength: A Randomized Interventional Trial.

To examine the dose-response of the Nordic hamstring exercise (NHE) on biceps femoris long head (BFlh) architecture and eccentric knee flexor strength. Randomized interventional trial. Forty recreationally active males completed a 6-week NHE training program consisting of either intermittent low volumes (group 1; n = 10), low volumes (group 2; n = 10), initial high volumes followed by low volumes (group 3; n = 10), or progressively increasing volumes (group 4; n = 10). A 4-week detraining period followed each program. Muscle architecture was assessed weekly during training and after 2 and 4weeks of detraining. Eccentric knee flexor strength was assessed preintervention and postintervention and after 2 and 4weeks of detraining. Following 6weeks of training, BFlh fascicle length (FL) increased in group 3 (mean difference = 0.83cm, d = 0.45, P = .027, +7%) and group 4 (mean difference = 1.48cm, d = 0.94, P = .004, +14%). FL returned to baseline following detraining in groups 3 and 4. Strength increased in group 2 (mean difference = 53.6N, d = 0.55, P = .002, +14%), group 3 (mean difference = 63.4N, d = 0.72, P = .027, +17%), and group 4 (mean difference = 74.7, d = 0.83, P = .006, +19%) following training. Strength returned to baseline following detraining in groups 2 and 3 but not in group 4. Initial high volumes of the NHE followed by lower volumes, as well as progressively increasing volumes, can elicit increases in BFlh FL and eccentric knee flexor strength. Low volumes of the NHE were insufficient to increase FL, although as few as 48 repetitions in 6 weeks did increase strength.

Effects of Whole-Body Vibration Therapy on Knee Osteoarthritis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

IntroductionKnee osteoarthritis is a leading cause of disability and medical costs. The effect of whole-body vibration in knee osteoarthritis is controversial. The aim of this study was to assess the effects and safety of whole-body vibration on pain, stiffness, physical function, and muscle strength in patients with knee osteoarthritis.MethodsPubMed, Scopus, Web of Science, Physiotherapy Evidence Database (PEDro) and EMBASE databases were searched (date last accessed 1 April 2021) using the key words “vibration” and “knee osteoarthritis”, to identify all randomized controlled trials related to whole-body vibration and knee osteoarthritis. Outcomes related to pain, stiffness, physical function, muscle strength, adverse events were included. The risk of bias and quality were assessed by the Cochrane Collaboration tool and PEDro scale. A systematic review and meta-analysis were performed. Subgroup analysis was performed for low- and high-frequency interventions.ResultsA total of 14 randomized controlled trials involving 559 patients with knee osteoarthritis met the inclusion criteria. Nine studies were good-quality trials (PEDro score=6–8), and 5 studies were fair-quality trials (PEDro score=4–5). Ten studies were included in the meta-analysis. One study showed negative effects of whole-body vibration on knee osteoarthritis. The duration of whole-body vibration ranged from 4 to 24 weeks. Meta-analysis revealed that whole-body vibration with strengthening exercises has a significant treatment effect on pain score (standardized mean difference (SMD) = 0.46 points, 95% confidence interval (95% CI) = 0.20–0.71, p = 0.0004), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC-function) (SMD = 0.51 points, 95% CI = 0.27–0.75, p < 0.0001), Timed Up and Go (TUG) test (SMD = 0.82 points, 95% CI = 0.46–1.18, p < 0.00001), extensor isokinetic peak torque (SMD = 0.65 points, 95% CI = 0.00–1.29, p = 0.05), peak power (SMD = 0.68 points, 95% CI = 0.26–1.10, p = 0.001), and extensor isometric strength (SMD = 0.44 points, 95% CI = 0.13–0.75, p = 0.006). Both low-frequency (10–30 Hz) and high-frequency (30–40 Hz) whole-body vibration were associated with significant changes in pain, physical function, and knee extensor strength (p < 0.05). WBV was not associated with significant changes in stiffness, balance ability, quality of life, and knee flexor strength. No adverse events were reported.ConclusionMeta-analysis showed that low-frequency and high-frequency whole-body vibration had additional positive effects compared with strengthening exercises alone on pain, knee extensor muscle strength, and physical function in individuals with knee OA. Whole-body vibration with strengthening exercises can be incorporated into treatment protocols.LAY ABSTRACTKnee osteoarthritis is a leading cause of disability and medical costs. Osteoarthritis leads to pain, stiffness, swelling and loss of function, resulting in poor quality of life. Whole-body vibration is a non-invasive treatment that has been proposed to improve muscle strength and physical performance. This analysis of 14 randomized controlled trials showed that, compared with exercise alone, whole-body vibration with exercise had positive effects on pain, physical function, and knee extensor muscle strength in patients with knee osteoarthritis. Based on these findings, we recommend whole-body vibration used together with strengthening exercises for knee osteoarthritis.

Strength, Flexibility and Postural Control of the Trunk and Lower Body in Participants with and without Patellofemoral Pain

Patellofemoral pain (PFP) is a frequent knee condition. The aim of this study was to investigate strength, flexibility and postural control in people with and without PFP. Fifty-five participants between 14 and 54 years of age (PFP = 18, control group = 37) were included. Strength and flexibility for all trunk, hip, knee and ankle muscle groups were measured along with postural control outcomes. Analyses were conducted based on the “affected” and “non-affected” leg within-group and between-groups. Between-groups analysis demonstrated a statistically lower strength of trunk muscles (range: 35.8–29.3%, p &lt; 0.001), knee extensors (20.8%, p = 0.005) and knee flexors (17.4%, p = 0.020) in PFP participants. Within-group analysis proved an 8.7% (p = 0.018) greater hip internal rotation strength and ankle extension flexibility (p = 0.032) of the “affected side” in PFP participants. This was, to our knowledge, the first study to investigate the strength of all trunk muscle groups. The results indicate that participants with PFP exhibit impaired strength of trunk muscle groups, along with knee muscle deficits, which may present a rehabilitation target. Clinicians should consider implementing trunk strengthening exercises into PFP programs along with knee-targeting exercise programs.

Persistent knee flexor strength deficits identified through the NordBord eccentric test not seen with “gold standard” isokinetic concentric testing during the first year after anterior cruciate ligament reconstruction with a hamstring tendon autograft

ObjectiveTo investigate the recovery of knee flexor muscle strength evaluated with a Nordic hamstring eccentric test (NordBord) compared with an isokinetic concentric test (Biodex) during the first year after anterior cruciate ligament (ACL) reconstruction using a hamstring tendon autograft. DesignProspective observational registry study; level of evidence, 3. SettingPrimary care. ParticipantsCross-sectional data of 127 patients (45% women, mean age 24.9 ± 8.1 years) were extracted from a rehabilitation outcome registry at 10 weeks and 4, 8 and 12 months after ACL reconstruction with hamstring tendon autograft. Main outcome measuresAll patients performed a concentric Biodex test, and an eccentric NordBord test on the same occasion or within seven days of the concentric test. The primary outcome was the limb symmetry index between the respective tests. ResultsA greater knee flexor symmetry deficit was observed with the eccentric test compared with the concentric test at all follow-ups with clinically relevant differences at 4 (11.8% ± 12.7% [CI 7.8–15.8%]) and 8 months (13.4 ± 11.9 [CI 9.7–17.2%]. ConclusionThe eccentric NordBord test was able to identify clinically relevant deficits in knee flexor strength symmetry that were not identified by gold standard isokinetic concentric testing during the first year among patients treated with an ACL reconstruction using a hamstring tendon autograft.

Strength and Biomechanical Risk Factors for Noncontact ACL Injury in Elite Female Footballers: A Prospective Study.

This study aimed to determine if a preseason field-based test battery was prospectively associated with noncontact anterior cruciate ligament (ACL) injury in elite female footballers. In total, 322 elite senior and junior female Australian Rules Football and soccer players had their isometric hip adductor and abductor strength, eccentric knee flexor strength, countermovement jump (CMJ) kinetics, and single-leg hop kinematics assessed during the 2019 preseason. Demographic and injury history details were also collected. Footballers were subsequently followed for 18 months for ACL injury. Fifteen noncontact ACL injuries occurred during the follow-up period. Prior ACL injury (odds ratio [OR], 9.68; 95% confidence interval (95% CI), 2.67-31.46), a lower isometric hip adductor to abductor strength ratio (OR, 1.98; 95% CI, 1.09-3.61), greater CMJ peak take-off force (OR, 1.74; 95% CI, 1.09-3.61), and greater single-leg triple vertical hop average dynamic knee valgus (OR, 1.97; 95% CI, 1.06-3.63) and ipsilateral trunk flexion (OR, 1.60; 95% CI, 1.01-2.55) were independently associated with an increased risk of subsequent ACL injury. A multivariable prediction model consisting of CMJ peak take-off force, dynamic knee valgus, and ACL injury history that was internally validated classified ACL injured from uninjured footballers with 78% total accuracy. Between-leg asymmetry in lower limb strength and CMJ kinetics were not associated with subsequent ACL injury risk. Preseason field-based measures of lower limb muscle strength and biomechanics were associated with future noncontact ACL injury in elite female footballers. These risk factors can be used to guide ACL injury screening practices and inform the design of targeted injury prevention training in elite female footballers.

Muscle power is more important than strength in preventing falls in community-dwelling older adults

The primary purpose of this study was to determine whether muscle strength or power is a better predictor of fallers (including both single and recurrent) in everyday living conditions among community-dwelling older adults. Secondly, we identified the optimal threshold of the identified fall predictors to best differentiate fallers from non-fallers. Ninety-four healthy older adults (72.0 ± 5.5 years) participated in the study. After reporting retrospective falls from the past year, participants were assessed for isometric strength capacities of the knee extensors and flexors. Lower limb power performance was calculated based on the time used to complete the five times sit-to-stand (STS) test. Fifty-six participants (59.6%) reported not falling, and 38 participants (40.4%) reported one or more falls in the past year. No significant differences were found between non-fallers and fallers for knee extensor (p = 0.729) and flexor (p = 0.157) strength capabilities. Non-fallers took significantly less time to complete the STS test (p = 0.010) and demonstrated more leg muscle power (p = 0.016) than fallers. The overall accuracy of classifying fallers and non-fallers was 63.8% and 64.9% for leg muscle power and the STS duration, respectively. The leg power and STS duration optimal cutoff values to discriminate fallers and non-fallers were determined as 1.3 W/(kg × m) and 12 s. Results suggest that STS leg muscle power is more predictive of everyday living falls than strength in community-dwelling older adults. Findings provide valuable information to assist with screening high fall risk older adults and develop muscle power training-based interventions to prevent falls in this population.

Effects of Blood Flow Restriction Training on Clinical Outcomes for Patients With ACL Reconstruction: A Systematic Review.

Knee muscle atrophy and weakness are common impairments after anterior cruciate ligament (ACL) reconstruction. Blood flow restriction (BFR) training represents a new approach to treat such impairments. However, limited evidence currently exists to support this intervention in related patients. To appraise literature comparing the effects of BFR training with conventional therapy on knee muscle morphological and strength properties in ACL-reconstructed patients. PubMed, SPORTDiscus, CINAHL, and Cochrane Central Register databases were searched for relevant articles from January 1991 through April 2021. Articles were minimum Level 3 evidence focusing on knee muscle morphologic as well as extensor and flexor strength outcomes in ACL-reconstructed patients of all graft types. Systematic review. Level 2. Critical appraisal instruments (Downs and Black checklist, Cochrane Collaboration tool, ROBINS-1 tool) were used to evaluate study quality. We independently calculated effect sizes (ESs) (Cohen d) between groups in each study. The Strength of Recommendation Taxonomy grading scale was used for clinical recommendations. Six articles (4 randomized control studies, 1 nonrandomized study, and 1 case-control study) met inclusion criteria. Exercises paired with BFR training included open kinetic chain, closed kinetic chain, and passive applications. Diverse assessments and time of intervention were observed across studies. ESs ranged from trivial to large in favor of BFR training for muscle morphological (d = 0.06 to 0.81) and strength assessments (d = -0.12 to 1.24) with CIs spanning zero. At this time, grade B or inconsistent and limited-quality patient-oriented evidence exists to support using BFR training to improve or maintain thigh muscle size as well as knee extensor and flexor strength in ACL-reconstructed patients. ESs indicated no consistent clinically meaningful differences when compared with conventional therapy. Subsequent analyses should be repeated as new evidence emerges to update practice guidelines.

Correlation Between Y-Balance Test and Balance, Functional Performance, and Outcome Measures in Patients Following ACL Reconstruction.

BackgroundThe Y-Balance test (YBT) is commonly used to evaluate balance after anterior cruciate ligament reconstruction (ACLR). However, several studies have also used it as a functional performance test (FPT).PurposeThis study aimed to examine the relationship between YBT scores and measures of knee joint laxity, static balance, knee flexor and extensor torque and strength ratio, and FPTs.Study DesignRetrospective cohort study.MethodsFifty-nine patients who underwent ACLR using hamstring autografts were retrospectively analyzed. The Pearson correlation coefficient was used to determine the strength of the association between scores on the YBT and selected outcomes including laxity measured via the KT-2000 arthrometer, static balance measured via the Biodex Balance System, isokinetic muscle torque and hamstring-to-quadriceps (HQ) ratio, and performance on the single leg hop test and the single leg vertical jump test.ResultsForty-six men and 13 women were included. The mean age and follow-up period were 29.6 ± 9.6 years and 12.4 ± 2.1 months, respectively. The KT-2000 arthrometer measures, Biodex Balance System scores, and HQ ratio measurements were not significantly correlated with the YBT scores. All YBT scores, except the YBT-anterior score, correlated with the isokinetic extensor and flexor torques (r-values: 0.271–0.520). All the YBT scores had significant weak to moderate correlations with the single leg hop test and single leg vertical jump test scores: YBT-anterior (r = 0.303, r = 0.258), YBT-posteromedial (r = 0.475, r = 0.412), YBT-posterolateral (r = 0.525, r = 0.377), and YBT-composite (r = 0.520, r = 0.412).ConclusionPost-ACLR YBT scores correlated with functional performance and muscle strength, but not with static balance, joint laxity, and HQ ratios. The YBT scores as a measure of balance are related to improved functional performance and isokinetic torque measures.Level of evidence3

The effect of ankle flexibility on the relationship between knee isokinetic strength and the speed of underwater dolphin kicks in male competitive swimmers

BACKGROUND: Lower-extremity muscle strength and ankle flexibility play key roles in underwater swimming movements. OBJECTIVES: To investigate the relationship between knee isokinetic strength and the speed of underwater dolphin kicks (UDK-S) in competitive male swimmers and identify whether ankle flexibility affects the association between knee isokinetic strength and UDK-S. METHODS: Fifty-two highly trained male swimmers participated in this study. The speed at which the participants travelled 15 m performing UDKs was calculated as UDK-S. Knee flexor and extensor concentric isokinetic strength at fast (240∘/s) and slow (60∘/s) velocities and ankle flexibility were evaluated. Bayesian framework analysis was conducted to examine the relationship between these variables and determine whether this relationship is influenced by ankle flexibility. RESULTS: There was strong-to-extremely strong evidence (Bayes factor = 24.4 to 198.3) that knee extensor (60∘/s) and knee flexor (60∘/s and 240∘/s) strength are positively and generally moderately correlated with UDK-S. Ankle plantar flexion flexibility was identified to be a moderator between knee extensor strength (60∘/s) and UDK-S. CONCLUSIONS: Knee extensor and knee flexor strength were significantly correlated with UDK-S, and the relationship between knee muscle strength and UDK-S was influenced by ankle plantar flexion flexibility in male competitive swimmers.

Knee Flexor Eccentric Strength, Hamstring Muscle Volume and Sprinting in Elite Professional Soccer Players with a Prior Strained Hamstring.

Simple SummaryGiven the link between a prior hamstring injury and the increased risk of suffering a subsequent injury in professional soccer, an understanding of the features displayed by previously injured players is important. The aim of the present study was to investigate if players with a history of hamstring injury exhibit bilateral deficits in knee flexor eccentric strength, hamstring muscle volume, and sprinting performance. The eccentric knee flexor strength was greater in the previously injured limbs compared to both the contralateral uninjured limbs in the previously injured group and the uninjured limbs in the previously uninjured players. Previously injured limbs showed possibly larger short heads of the biceps femoris and likely semitendinosus muscle volumes. Sprinting performances in the 5-m were possibly worse in players with a history of hamstring muscle strain injury compared to the previously uninjured players.The aim was to determine if players with a prior hamstring strain injury (HSI) exhibit bilateral deficits in knee flexor eccentric strength and hamstring muscle volume and differences in sprinting performance compared with players without a history of HSIs. Forty-six male professional soccer players participated in this study. Eccentric knee flexor strength, hamstring muscle volume (MRI), and a 20-m running sprint test (5- and 10-m split time) were assessed at the start of the preseason. Eccentric knee strength of the previously injured limbs of injured players was greater (ES: 1.18–1.36) than the uninjured limbs in uninjured players. Previously injured limbs showed possibly larger biceps femoris short heads (BFSh) and likely semitendinosus (ST) muscle volumes than the contralateral uninjured limbs among the injured players (ES: 0.36) and the limbs of the uninjured players (ES: 0.56), respectively. Players who had experienced a previous HSI were possibly slower in the 5-m (small ES: 0.46), while unclear differences were found in both the 10-m and 20-m times. Players with a prior HSI displayed greater eccentric knee flexor strength, possibly relatively hypertrophied ST and BFSh muscles, and possibly reduced 5-m sprinting performances than previously uninjured players. This can have implication for the design of secondary hamstring muscle injury prevention strategies.

Anterior cruciate ligament reconstruction with ultrasound-guided femoral nerve block does not adversely affect knee extensor strength beyond that seen with intravenous patient-controlled analgesia at 3 and 6 months postoperatively

BackgroundThis study aimed to investigate the effect of anterior cruciate ligament (ACL) reconstruction with an ultrasound-guided femoral nerve block (FNB) on knee extensor strength weakness 3 and 6 months, and graft rupture in the 1 year following ACL reconstruction. MethodsOne hundred and seven patients who underwent ACL reconstruction were included in this retrospective study. The patients were divided into two groups stratified by the method of postoperative pain management. The FNB group included 66 patients, and there were 41 patients in the intravenous patient-controlled analgesia (iv-PCA) group. The isokinetic peak torque of knee flexor and extensor was measured preoperative, 3 and 6 months after ACL reconstruction. Muscle strength measurements were performed using the BIODEX dynamometer at a velocity of 60°/s and 180°/s. Peak torque of knee extensor and flexor strength, estimated pre-injury capacity (EPIC), body weight ratio (BW), and graft rupture incidence were compared between the two groups. ResultsThere were no statistically significant differences in the knee extensor and flexor strength for all items at 3 and 6 months after ACL reconstruction. There was also not a statistically significant difference in the graft rupture incidence between the two groups: FNB group was two patients, 3.0% vs. iv-PCA group was one patient, 2.4% (p = 0.86). ConclusionACL reconstruction with ultrasound-guided FNB does not affect knee extensor strength at 6 months, nor graft rupture at 1 year postoperatively.

The Effect of Blood Flow Restriction Training on Muscle Atrophy Following Meniscal Repair or Chondral Restoration Surgery in Active Duty Military: A Randomized Controlled Trial.

Recently, blood flow restriction (BFR) training has gained popularity as an alternative to high-load resistance training for improving muscle strength and hypertrophy. Previous BFR studies have reported positive treatment effects; however, clinical benefits to using BFR following meniscal repair or chondral surgery are unknown. The purpose of this study was to determine the effect of resistance exercises with BFR training versus exercises alone on self-reported knee function, thigh circumference, and knee flexor/extensor strength postmeniscal or cartilage surgery. Single-blinded randomized controlled trial in an outpatient military hospital setting. Twenty participants were randomized into 2 groups: BFR group (n = 11) and control group (n = 9). Participants completed 12weeks of postoperative thigh strengthening. The BFR group performed each exercise with the addition of BFR. Both groups continued with the prescribed exercises without BFR from 12weeks until discharged from therapy. Thigh circumference and self-reported knee function were measured at 1, 6, 12, and 24weeks postoperatively along with knee extensor and flexor strength at 12 and 24weeks. Change scores between time points were calculated for knee function. Limb symmetry indices (LSI) were computed for thigh circumference and knee strength variables. Seventeen participants were included in the final analyses (BFR = 8 and control = 9) due to COVID-19 restrictions. There were no interactions or main effects for group. Time main effects were established for change in knee function scores, thigh circumference LSI, and knee extensor strength LSI. However, knee flexor strength LSI had no main effect for time. The outcomes of this trial suggest that resistance exercises with and without BFR training may result in similar changes to function, thigh atrophy, and knee extensor strength postmeniscus repair/chondral restoration, though further study with larger sample sizes is needed.

Utilization of Mid-Thigh Magnetic Resonance Imaging to Predict Lean Body Mass and Knee Extensor Strength in Obese Adults.

Purpose:To train and test a machine learning model to automatically measure mid-thigh muscle cross-sectional area (CSA) to provide rapid estimation of appendicular lean mass (ALM) and predict knee extensor torque of obese adults.Methods:Obese adults [body mass index (BMI) = 30–40 kg/m2, age = 30–50 years] were enrolled for this study. Participants received full-body dual-energy X-ray absorptiometry (DXA), mid-thigh MRI, and completed knee extensor and flexor torque assessments via isokinetic dynamometer. Manual segmentation of mid-thigh CSA was completed for all MRI scans. A convolutional neural network (CNN) was created based on the manual segmentation to develop automated quantification of mid-thigh CSA. Relationships were established between the automated CNN values to the manual CSA segmentation, ALM via DXA, knee extensor, and flexor torque.Results:A total of 47 obese patients were enrolled in this study. Agreement between the CNN-automated measures and manual segmentation of mid-thigh CSA was high (>0.90). Automated measures of mid-thigh CSA were strongly related to the leg lean mass (r = 0.86, p < 0.001) and ALM (r = 0.87, p < 0.001). Additionally, mid-thigh CSA was strongly related to knee extensor strength (r = 0.76, p < 0.001) and moderately related to knee flexor strength (r = 0.48, p = 0.002).Conclusion:CNN-measured mid-thigh CSA was accurate compared to the manual segmented values from the mid-thigh. These values were strongly predictive of clinical measures of ALM and knee extensor torque. Mid-thigh MRI may be utilized to accurately estimate clinical measures of lean mass and function in obese adults.

Relationship Between Isokinetic Knee Strength and Single-Leg Drop Jump Performance 9 Months After ACL Reconstruction.

Background:Deficits in knee strength after anterior cruciate ligament reconstruction (ACLR) surgery are common. Deficits in the single-leg drop jump (SLDJ), a test of plyometric ability, are also found.Purpose:To examine the relationship between isokinetic knee strength, SLDJ performance, and self-reported knee function 9 months after ACLR.Study Design:Cross-sectional study; Level of evidence, 3.Methods:Knee isokinetic peak torque, SLDJ jump height, contact time, and reactive strength index (RSI), as well as International Knee Documentation Committee (IKDC) scores were assessed in 116 male, field-sport athletes at 9.2 months after ACLR. SLDJ testing took place in a 3-dimensional biomechanics laboratory. Linear regression models were used to analyze the relationship between the variables.Results:A significant relationship was found between ACLR-limb isokinetic knee extensor strength and SLDJ jump height (P < .001, r 2 = 0.29) and RSI (P < .001, r 2 = 0.33), and between ACLR-limb isokinetic knee flexor strength and SLDJ jump height (P < .001, r 2 = 0.12) and RSI (P < .001, r 2 = 0.15). A significant positive relationship was also found between knee extensor asymmetry and SLDJ jump height asymmetry (P < .001, r 2 = 0.27) and SLDJ reactive strength asymmetry (P < .001, r 2 = 0.18). Combined ACLR-limb jump height and contact time best predicted IKDC scores (P < .001, r 2 = 0.12).Conclusion:Isokinetic knee extension strength explained approximately 30% of SLDJ performance, with a much weaker relationship between knee flexion strength and SLDJ performance. Isokinetic strength and SLDJ performance were weak predictors of variation in IKDC scores.

The effect of static and dynamic muscle stretching as part of warm-up procedures on stretching on isokinetic strength, functional movement screen, flexibility and agility in Korean national foil fencers

The purpose of this study was to investigate the effect of combined static and dynamic stretch as part of warm-up procedures on isokinetic strength, functional movement screen (FMS), flexibility, and agility in Korean national foil fencers. Twelve Korean fencers (mean age 29.3±3.6yrs, Career: 16.6±3.1yrs, Height: 171.4±9.5cm, Weight: 67.3±12.4kg) participated in this study (Male: 7, age 30.0±3.2yrs, Career: 16.7±2.2yrs, Height: 177.1±8.1cm, Weight: 75.1±9.9kg; Female: 5, age 28.4±4.4yrs, Career: 16.4±4.3yrs, Height: 163.4±3.9cm, Weight: 56.3±4.1kg). Fencers measured FMS, isokinetic strength of knee joint, flexibility, agility at pre (1-week) and post (4-week). Fencers performed a warm-up program three times a week for four weeks. As a results, FMS scores (11.8±2.3 to 14.4±1.6, p&lt;0.05), strength of dominant knee flexors (115.5±26.0 to 126.0±26.6, p&lt;0.05), change-step jump (66.0±6.8 to 69.4±5.6, p&lt;0.05), trunk forward flexion (12.0±7.7 to 13.9±6.5, p&lt;0.05) were significantly higher in post-test than pre-test, respectively. However, the results for front-rear step, trunk backward extension were not significant differences between pre-test and post-test. These results suggest that the fencing-specific warm-up program based on stretching is effective on strength of knee flexors, agility by increasing flexibility, improving stability, mobility.