Interlimb Strength Research Articles

Investigating the association between intralimb strength ratio, interlimb strength and range of motion asymmetry index, and functional limitations with fall incidence among older adults: protocol for a prospective cohort study

The present study aims to identify the intralimb strength ratio, interlimb strength and range of motion asymmetry index in elderly individuals and then investigate the association between these asymmetry indices...

Intra- and inter-limb strength imbalance and asymmetry in soccer: A comparison of elite senior and junior players.

Evaluation of muscle strength imbalance can be an important element in optimizing the training process of soccer players. The purpose of the study was to examine isokinetic peak torque (PT) and total work (TW) exerted by both knee extensors (quadriceps or Q) and flexors (hamstrings or H), intra-limb imbalance and the magnitude and direction of inter-limb asymmetry in top elite senior (n = 109) and junior (n = 74) soccer players. An isokinetic dynamometry was used to measure maximum peak torque of quadriceps (PT-Q) and hamstrings (PT-H) at an angular velocity of 60° ·s-1, as well as the total work for extensors (TW-Q) and flexors (TW-H) at an angular velocity of 240° ·s-1 in the dominant (DL) and non-dominant leg (NDL) during concentric muscle contraction. Intra-limb imbalance and inter-limb asymmetries were calculated using a standard equation. Statistical analysis using t-test and Mann-Whitney U-test revealed: (a) no differences (p > 0.05) between groups for PT-Q and PT-H, (b) greater strength levels (p < 0.05) for TW-Q and TW-H of senior players than juniors, and (c) no differences (p > 0.05) between groups for intra-limb imbalance and inter-limb asymmetry. Additionally, Pearson's chi-kwadrat (χ2) analysis showed no differences (p > 0.05) between groups for intra-limb imbalance and inter-limb asymmetry in relation to the 'normative' values accepted in the literature that indicate an increase in the risk of knee injury. This study shows that isokinetic assessment can be an important tool to identify imbalances/asymmetries and to develop strategies to reduce the risk of muscle injury.

Exploring the relationship between lower limb strength, strength asymmetries, and curvilinear sprint performance: Findings from a pilot study.

Team sports involve various sprinting actions, including curvilinear sprints, yet their neuromuscular factors have been understudied. The aim of this cross-sectional study was to investigate the relationship between lower limb muscle strength, strength asymmetries, linear sprint and curvilinear sprint performance. At two visits 12 male (age: 24.8 ± 4.7 years, height: 1.82 ± 0.06 m, body mass: 80 ± 6.58 kg) and 6 female (age: 20.8 ± 1.33 years, body height: 1.60 ± 0.02 m, body mass: 55.3 ± 2.88 kg) student-athletes completed isometric strength measurements of the knee flexors (KF), knee extensors (KE), hip abductors (HABD), hip adductors (HADD), as well as linear sprint and curvilinear sprint to the right and left. Sprint split times over 30 m (t30) were measured and curvilinear sprint split time deficits (t30deficit) and inter-limb strength asymmetries were calculated. Very large negative correlations were observed between HADD and HABD strength on one side and t30 of curvilinear sprint to the left (r = -0.75 and -0.71; p < 0.001) and right (ρ = -0.81 and -0.70; p < 0.001) on the other. The regression model consisting of HADD, HABD, and KF explained 76% and 67% of the variance in left and right curvilinear sprint t30, respectively. Similarly, 59% of the left curvilinear sprint t30deficit variance was explained by the HABD and KF strength. High inter-limb HABD strength symmetry was related to better left and right curvilinear sprint t30 (r = 0.71 and ρ = 0.75, p < 0.001). These results highlight the pivotal role of hip strength for curvilinear sprint speed, and emphasize the need of symmetrical HABD muscle strength to optimize neuromuscular function during curvilinear sprint.

Bilateral differences of isokinetic knee extensor strength are velocity- and task-dependent

ABSTRACT The purpose of this study was to investigate the concordance of isokinetic bilateral strength differences of the knee extensors in single- and multi-joint movement tasks. One hundred and nineteen male athletes performed isokinetic legpresses at 0.1 m/s and 0.7 m/s as well as isokinetic knee extensions at 60°/s and 180°/s. Bilateral differences and directed bilateral differences (sign indicating the direction of the difference) were calculated for all measurements. Bland-Altman-Plots were plotted to investigate if the different conditions detect bilateral differences of the same magnitude. Additionally, concordance correlations for the directed bilateral differences of the different tests were calculated to investigate magnitude and direction. The results indicate poor to fair concordance between the bilateral differences in the legpress conditions as well as between single- and multi-joint tasks. The single-joint knee extensions displayed a moderate level of agreement. Bilateral strength differences in isokinetic movement tasks are dependent on movement velocity and the nature of the task (single- or multi-joint movement) in the lower extremities. Both the value and the direction of the strength differences show no clear pattern across the investigated measurements and cannot be used interchangeably. Therefore, to assess interlimb strength balance, multiple different tests should be performed.

Reducing Limb Asymmetry in Females Collegiate Basketball: A Randomized Trial

Background and Aim: Interlimb strength asymmetry has garnered significant attention in the field of sports science for its potential to influence both athletic performance and injury risk. Despite this, there is a noticeable gap in the literature concerning its impact on elite female collegiate basketball players. The study aims to assess the effectiveness of targeted weaker limb strength training in reducing jump strength asymmetry among elite female college basketball players. Materials and Methods: A randomized controlled design was used, involving 24 elite female college basketball players from Guangzhou Sports University. The Experimental Group underwent specialized training for the weaker limb, while the Control Group followed balanced training. The primary outcome was the change in the maximum ground reaction force (GRF) during single-leg jumps. Linear Mixed-Effects models were used for statistical analysis, with a two-tailed significance level of p&lt;0.05. Result: The intervention was effective in reducing Countermovement Jump Asymmetry and Horizontal Jump Asymmetry with statistical significance (p-values 0.0045 and 0.029, respectively) but did not significantly impact Lateral Jump Asymmetry (p-value 0.2733). These findings were consistent when comparing the Experimental and Control groups post-intervention (p-values 0.0055 and 0.0474 for Countermovement and Horizontal, respectively; 0.3995 for Lateral). Time and group interaction analyses were significant but not universally consistent across all measures after the Bonferroni correction. Overall, the intervention had a mixed but generally positive effect on jump asymmetry. Conclusion: The study demonstrates that targeted weaker limb strength training can effectively reduce jump strength asymmetry in elite female collegiate basketball players. These findings have implications for athletic training regimens aimed at both improving performance and reducing the risk of injury.

Lower Extremity Asymmetry Values Derived From Multiple Strength Testing Modes Are Associated With Perceived Functional Capabilities Among University Athletes.

Background: Muscle strength asymmetry and athlete introspective measures are associated with musculoskeletal (MSK) sport injury and reinjury. However, the interrelationship between mechanical and subjective measures of concentric and eccentric limb function needs further exploration. This includes investigating if an athlete's perception of their overall MSK function influences limb asymmetry across different testing modalities. Objectives: To (i) explore the interrelationship between mechanical and subjective measures of lower limb function in university athletes and (ii) compare the consistency in interlimb strength asymmetries across different strength tests in groups of athletes with good, fair, and poor perceived limb function. Methods: University athletes (n = 175; n = 87 females) from six sports completed four tests of muscle strength, power, and plyometric function along with an assessment of perceived limb function using the Sport Fitness Index (SFI). Participants were categorized into high (GOODSFI), fair (FAIRSFI), and poor (POORSFI) perceived overall MSK function (perceived function) groups. Strength asymmetry indexes evaluated interlimb differences in concentric and eccentric maximal strength, countermovement jump (CMJ) impulse, unilateral CMJ height, and reactive strength index in unilateral repeat hop testing. Cumulative link mixed-effects models assessed the relationship between strength asymmetries and perceived limb function. Results: The POORSFI group showed increased asymmetry in concentric strength testing (p = 0.022), more consistent interlimb asymmetries (p < 0.001), and reduced overall muscle strength compared to the GOODSFI group. Conclusion: Higher interlimb asymmetry in maximal concentric strength measures along with reduced muscle strength was found in the POORSFI group compared to the GOODSFI group. The POORSFI group also showed greater consistency in muscle strength asymmetry derived across different tasks.

The influence of inter-limb asymmetries in muscle strength and power on athletic performance: a review

The aim of this review was to examine the available literature on inter-limb strength and power asymmetries and their effect on sports performance. In total, 31 studies were included. The findings indicate a negative effect of strength asymmetries on change of direction, sprinting, cycling and kicking performance. They may also be detrimental to jumping performance, however, more research is needed to confirm this. The findings on power asymmetries are more inconsistent and indicate that asymmetries measured with various power tests may affect some performance measures. For example, jumping performance is affected by the power asymmetries measured with jumps, but not by those measured with change of direction tests. Furthermore, the correlation between asymmetry tests and performance outcomes can be affected by the type of sport, training period and the magnitude of the asymmetry. To better understand the effects of strength and power asymmetries on athletic performance, further research is needed, particularly on the effects on sport-specific performance tests.

Should We Use Unilateral or Bilateral Tasks to Assess Maximal and Explosive Knee Extensor Strength in Patients with Knee Osteoarthritis? A Cross-Sectional Study.

Deficits in maximal and explosive knee extensor strength, which are usually assessed with unilateral tasks, are substantial in patients with knee osteoarthritis (KOA). The aim of this study was to investigate the clinical relevance of unilateral vs. bilateral tasks for assessing knee extensor strength in patients with KOA. This was achieved primarily by comparing unilateral and bilateral inter-limb strength asymmetries and secondarily by examining the relationship between unilaterally and bilaterally measured strength, and performance-based and self-reported function. Twenty-four patients with unilateral KOA (mean age: 65 ± 7 years) performed isometric gradual and explosive maximal voluntary contractions to assess, respectively their maximal and explosive strength. Performance-based and self-reported function were also evaluated with standard functional tests and questionnaires, respectively. Inter-limb asymmetries of maximal and explosive strength did not differ significantly between unilateral (mean asymmetry: 26 ± 15%) and bilateral tasks (22 ± 21%). In the same way, the relationships between knee extensor strength—measured either unilaterally or bilaterally—and performance-based or self-reported function were not influenced by the type of task. In conclusion, it does not seem to make a difference in terms of clinical relevance whether maximal and explosive knee extensor strength are evaluated with unilateral or bilateral tasks in KOA patients.

Does piriformis muscle syndrome impair postural balance? A case control study

Background and purpose While patients with musculoskeletal disorders reported postural balance impairments, it is unknown whether patients with piriformis muscle syndrome (PMS) may exhibit postural balance disorders compared to controls. The aim was to compare postural balance in patients with PMS to controls in static and dynamic conditions. Material and methods Twelve patients with PMS and twelve controls were enrolled. Static postural balance was assessed by calculating the symmetry index (SI) in the unipedal posture. To measure vision contribution, the Romberg index (RI) was computed. Dynamic postural balance was evaluated with the Timed up and go test (TUGT). Besides, inter-limb strength asymmetry (SA), pain and the short form-36 (SF-36) were assessed. Results The PMS group (PMSG) exhibited significant (p < 0.001) higher SI in eyes opened (EO) and eyes closed (EC) conditions compared to the control group (CG). Besides, PMSG had significant higher RI (p < 0.05), TUGT scores (p < 0.001), SA values (p < 0.05), pain intensity (p < 0.001), and worse SF-36 scores on all physical health (p < 0.05) and psychological health (only in vitality and mental health [p < 0.05]), compared to CG. Conclusion Our data revealed impaired static and dynamic postural balance, and reduced quality of life in PMSG compared to CG. Postural balance impairments could explain the poor quality of life, which are likely due to the higher SA and higher pain intensity. Clinicians and physiotherapists should consider postural balance disorders while designing rehabilitation programs in these patients.

Intra- and Inter-Limb Strength Asymmetry in Soccer: A Comparison of Professional and Under-18 Players.

(1) Background: the present study examined the isokinetic peak torque exerted by both knee extensors and flexors, anterior–posterior imbalance and the magnitude and direction of inter-limb asymmetry in professional and academy soccer players. (2) Methods: one hundred soccer players (professional = 50, elite academy = 50) volunteered to take part in this investigation. An isokinetic dynamometer was used to measure the knee extensor (quadriceps) and flexors muscle (hamstrings) torques of the limbs as well as inter-limb asymmetries—using a standard percentage difference equation. (3) Results: professional players exhibited significantly greater (effect size [ES] = large) strength levels in the quadriceps and hamstrings under both testing conditions, significantly higher (small to moderate) intra-limb ratio values for 60°·s−1 but not for the 300°·s−1 test condition, significantly (small to moderate) lower inter-limb asymmetry values for all test conditions, with the exception of the hamstrings at 60°·s−1 and the direction of asymmetry was poor to slight, indicating that limb dominance was rarely the same between groups. (4) Conclusions: this study shows that isokinetic assessments, i.e., peak torque exerted by both knee extensors and flexors and intra-limb ratio, and the subsequent inter-limb asymmetry, i.e., magnitude and direction, can differentiate between professional and academy soccer players.

The Calculation, Thresholds and Reporting of Inter-Limb Strength Asymmetry: A Systematic Review.

The prevalence of inter-limb strength differences is well documented in the literature however, there are inconsistencies related to measurement and reporting, and the normative values and effects associated with inter-limb asymmetry. Therefore, the aims of this systematic review were to: 1) assess the appropriateness of existing indices for the calculation of asymmetry, 2) interrogate the evidence basis for literature reported thresholds used to define asymmetry and 3) summarise normative levels of inter-limb strength asymmetry and their effects on injury and performance. To conduct this systematic review, scientific databases (PubMed, Scopus, SPORTDiscus and Web of Science) were searched and a total of 3,594 articles were retrieved and assessed for eligibility and article quality. The robustness of each identified asymmetry index was assessed, and the evidence-basis of the identified asymmetry thresholds was appraised retrospectively using the references provided. Fifty-three articles were included in this review. Only four of the twelve identified indices were unaffected by the limitations associated with selecting a reference limb. Eighteen articles applied a threshold to original research to identify "abnormal" asymmetry, fifteen of which utilised a threshold between 10-15%, yet this threshold was not always supported by appropriate evidence. Asymmetry scores ranged between and within populations from approximate symmetry to asymmetries larger than 15%. When reporting the effects of strength asymmetries, increased injury risk and detriments to performance were often associated with larger asymmetry, however the evidence was inconsistent. Limitations of asymmetry indices should be recognised, particularly those that require selection of a reference limb. Failure to reference the origin of the evidence for an asymmetry threshold reinforces doubt over the use of arbitrary thresholds, such as 10-15%. Therefore, an individual approach to defining asymmetry may be necessary to refine robust calculation methods and to establish appropriate thresholds across various samples and methodologies that enable appropriate conclusions to be drawn.

Persistent quadriceps activation failure reduces in ACL reconstructed patients submitted to strength training based on force steadiness and visual feedback

Background:Quadriceps activation failure after anterior cruciate ligament reconstruction (ACLr) is related to the inhibition of alpha-motor units and results in muscle weakness. The quadriceps activation failure limits the rehabilitation outcomes, especially strength gains that are essential to the return to sport and to minimize the risk for the onset of knee osteoarthritis. Exercises involving force steadiness could reduce the variability of motor unit discharge rate and contribute to the force enhancement. On the other hand, force steadiness during isometric contractions involves controlling the fluctuations in the force signals, which might be enhanced by visual feedback. Therefore, the combination of force steadiness and visual feedback could have potential benefits for patients with persistent quadriceps activation failure.Objectives:To determine the effect of strength training with force steadiness and visual feedback on knee extension torque, knee stability, and knee pain in patients with persistent quadriceps activation failure after ACLr.Methods:Twenty-five patients (43.7±12.2 years-old, 69.8±10.8 kg, and 1.69±0.09 m, 10 men) with persistent quadriceps activation failure after ACLr non-responders to a conventional rehabilitation protocol were included in this case series. All protocols were approved by the local institutional ethics board. Persistent quadriceps activation failure was diagnosed based on the clinical history, temporal diphase with physical therapy protocol, non-gain of quadriceps strength after around 20 sessions of physiotherapy in the 9th month of rehabilitation, quadriceps weakness in the clinical examination, and abnormal isokinetic assessment (peak extensor torque<100 Nm, asymmetry in peak extensor torque>50%, or asymmetry in peak torque>70 Nm). All patients were submitted to an ACLr surgery performed by the same surgeon with semitendinosus-gracilis autograft. The intervention considered three sessions/week and lasted until 20 sessions or auto-perception of functional knee stability. The intervention and torque measurements were performed with an isokinetic device. A warmed up for 10 minutes on a cycle ergometer without load (60 rpm) was performed. After, they performed knee extension following a trapezoid curve feedback. Due to strength unbalances between ACLr and non-ACLr limbs, we used five series of 8 and 5 repetitions, respectively. The training was performed at a workload between 60% and 70%. Knee extension peak torque was determined at baseline and after training protocol. Proportions of responders and non-responders were extracted considering a threshold of 25.02 Nm. Knee pain (any painful feeling at the knee developed between the last and new session) and stability (same knee stiff sensation when they had not suffered the ACL injury) were also assessed as a binary proportion. A mixed ANOVA with 2 factors [time (before and after intervention), and limb (ACLr and non-ACLr limb)] was performed to compare the knee extension peak torque. To compare the proportion of intervention responders, knee stability, and pain before and after intervention the 2-tailed McNemar test was performed.Results:Training improved knee extension peak torque in the ACLr limb (98.2±47.2 to 155.2±78.9, Δ=57.0 Nm, p=0.031) and the non-ACLr (169.6±86.9 to 209.5±101.8, Δ=39.9 Nm, p=0.178). At baseline, lower torque was found in the ACLr limb (169.6±86.9 vs. 98.2±47.2, Δ=71.4, p=0.003) and remain different after training protocol (209.5±101.8 vs. 155.2±78.9, Δ= 54.3, p=0.026). Most of the patients (84%) increased knee extension peak torque (p<0.001), 72% increased self-reported knee stability (p<0.001), and 52% decreased knee pain (p<0.001).Conclusion:Strength training with force steadiness and visual feedback was an effective intervention to improve knee extensor torque in ACLr patients with persistent quadriceps activation failure identified 9 months after an auto-graph ACL surgery. We found that 21 out of 25 patients were able to respond positively to the intervention. The intervention also improved the self-report of stability and pain. Although the difference in torque between limbs suggests that the asymmetries persisted after the intervention. This intervention might be the first rehabilitation stage in persistent quadriceps activation failure. The next rehabilitation stage to normalize the inter-limb strength needs to be explored.

Lower-Limb Muscle Strength, Anterior-Posterior and Inter-Limb Asymmetry in Professional, Elite Academy and Amateur Soccer Players.

Given the importance of the lower-limb strength and strength balance in soccer players and its relationship with injury prevention and performance, the present study compared quadriceps and hamstrings strength, the conventional (Hconc:Qconc), functional (Hecc:Qconc) hamstrings-to-quadriceps ratio and inter-limb strength asymmetry in professional, elite academy and amateur male soccer players. In this cross-sectional study, two hundred-six soccer players (professional = 75, elite academy = 68, amateurs = 63) volunteered to participate. Quadriceps and hamstrings isokinetic peak torque was investigated at 60°.s-1 in both the concentric and eccentric modality and at 300°.s-1 in the concentric modality. The conventional Hconc:Qconc, functional Hecc:Qconc ratio and quadriceps and hamstrings inter-limb strength asymmetry were then calculated. Professional players presented greater quadriceps and hamstrings strength than elite academy (effect size from small to moderate) and amateur players (moderate to very large). Both the conventional Hconc:Qconc and functional Hecc:Qconc ratio were greater in professional than elite academy and amateur players (small to moderate). Overall, quadriceps and hamstrings inter-limb strength asymmetry was greater in amateurs than professional (small to very large) and elite academy (trivial to large) players. The present findings provide coaches and medical staffs with normative lower-limb muscle strength data on professional, academy and amateur soccer players. Overall lower-limb muscle strength and inter-limb strength asymmetry could be used to evaluate possible inference on injury prevention and performance. The hamstrings-to-quadriceps ratio poorly differentiates between the soccer players background and offers limited prediction for injury prevention and performance.

The condition of the contralateral knee may induce different degrees of knee extensor strength asymmetry and affect functionality in individuals with unilateral or bilateral osteoarthritis

BackgroundLoss of knee extensor strength in individuals with knee osteoarthritis (KOA) may induce inter-limb strength asymmetries and alter functionality. The aims were to analyse whether the condition of the uninvolved knee (advanced to severe KOA or no affection) may induce different degrees of knee extensor strength asymmetry in individuals with KOA and to study whether functionality may differ in cases of unilateral or bilateral KOA. MethodsSixty-eight subjects with advance-to-severe KOA were categorized into two groups (unilateral or bilateral KOA). The knee extensor strength ratio (KESR), and self-reported and performance-based functionality were analysed and compared. Sex and age were independent factors. One- and two-way analysis of variance assessed for significant between-group differences (95% confidence interval (CI)). ResultsParticipants with unilateral KOA presented with 20% knee extensor strength asymmetry. The mean difference with the bilateral KOA group in terms of Knee Extensors Strength Ratio was 0.2 (95% CI 0–0.3; P = 0.021), of the Oxford Knee Scale score was 4.2 (95% CI 3.4–5.1; P = 0.037), and of the Timed Up and Go was 1.3 s (95% CI 0.5–2.2; P > 0.05). There were significant sex and age interactions (P < 0.05). ConclusionsIndividuals with unilateral or bilateral KOA present with different degrees of knee extensor strength asymmetry. The non-affected knee seems to help to better develop functional tasks in cases of unilateral condition. The findings may help the design of tailored strengthening interventions in which each knee condition in individuals with KOA should be considered.

Inter-limb strength asymmetry in adolescent distance runners: Test-retest reliability and relationships with performance and running economy

ABSTRACT The purpose of this investigation was, firstly, to quantify the test-retest reliability of strength measures in adolescent distance runners; and secondly, to explore the relationships between inter-limb strength asymmetry and performance and running economy (RE) in a similar cohort of young runners. For the reliability study, twelve (n = 6 female) post-pubertal adolescent distance runners performed an isometric quarter-squat on a dual force plate and unilateral isometric hip extension and hip abduction tests on two occasions. For the correlation study, participants (n = 31) performed the strength tests plus a submaximal incremental running assessment and a maximal running test. Running economy was expressed as the average energy cost of running for all speeds below lactate turnpoint and was scaled for body mass using a previously calculated power exponent. Allometrically scaled peak force during the quarter-squat and peak torque in the hip strength tasks showed acceptable levels of reproducibility (typical error ≤6.3%). Relationships between strength asymmetry and performance and RE were low or negligible (r < 0.47, p > 0.05), except for hip abduction strength asymmetry and RE in the female participants (r = 0.85, p < 0.001, n = 16). Practitioners should consider inter-limb hip abduction strength asymmetry on an individual level, and attempting to reduce this asymmetry in females may positively impact RE.

Effects of enhanced cutaneous sensory input on interlimb strength transfer of the wrist extensors.

The relative contribution of cutaneous sensory feedback to interlimb strength transfer remains unexplored. Therefore, this study aimed to determine the relative contribution of cutaneous afferent pathways as a substrate for cross‐education by directly assessing how “enhanced” cutaneous stimulation alters ipsilateral and contralateral strength gains in the forearm. Twenty‐seven right‐handed participants were randomly assigned to 1‐of‐3 training groups and completed 6 sets of 8 repetitions 3x/week for 5 weeks. Voluntary training (TRAIN) included unilateral maximal voluntary contractions (MVCs) of the wrist extensors. Cutaneous stimulation (STIM), a sham training condition, included cutaneous stimulation (2x radiating threshold; 3sec; 50Hz) of the superficial radial (SR) nerve at the wrist. TRAIN + STIM training included MVCs of the wrist extensors with simultaneous SR stimulation. Two pre‐ and one posttraining session assessed the relative increase in force output during MVCs of isometric wrist extension, wrist flexion, and handgrip. Maximal voluntary muscle activation was simultaneously recorded from the flexor and extensor carpi radialis. Cutaneous reflex pathways were evaluated through stimulation of the SR nerve during graded ipsilateral contractions. Results indicate TRAIN increased force output compared with STIM in both trained (85.0 ± 6.2 Nm vs. 59.8 ± 6.1 Nm) and untrained wrist extensors (73.9 ± 3.5 Nm vs. 58.8 Nm). Providing ‘enhanced’ sensory input during training (TRAIN + STIM) also led to increases in strength in the trained limb compared with STIM (79.3 ± 6.3 Nm vs. 59.8 ± 6.1 Nm). However, in the untrained limb no difference occurred between TRAIN + STIM and STIM (63.0 ± 3.7 Nm vs. 58.8 Nm). This suggests when ‘enhanced’ input was provided independent of timing with active muscle contraction, interlimb strength transfer to the untrained wrist extensors was blocked. This indicates that the sensory volley may have interfered with the integration of appropriate sensorimotor cues required to facilitate an interlimb transfer, highlighting the importance of appropriately timed cutaneous feedback.

Relationship Between Lower Extremity Strength Asymmetry And Jump And Sprint Performance

The relationship between inter-limb strength asymmetry and athletic performance is not clearly well-known. Different results in the literature makes it difficult to form a common consensus on this issue. The aim of this study was to investigate the relationship between inter-lower limb strength asymmetry (ILLSA) values and jump and sprint performances. Forty-eight individuals (21.5±2.8 years, 1.74±0.1 m, 67.3±9.7 kg) voluntarily participated in this study. All participants participated in squat (SJ), countermovement jump (CMJ), 40m sprint run tests and right and left isokinetic concentric knee flexion and extension strength (IS) test at low (60°.s -1 ) and high (300°.s -1 ) angular velocities. The symmetry angle formula was used in order to determine the isokinetic knee strength asymmetry values between inter-lower limb. According to the results it was revealed that there was no relation (p>0.05) between ILSSA at low and high angular velocities and squat jump (r = -0.106 0.200), countermovement jump (r = -0.11 0.087) and 40m sprint (r = 0.012 0.810) performance. In conclusion, there is no negative or positive relationship between inter limb isokinetic knee strength symmetry angle and jump and sprint performances in physically active individuals.

Functional electrical stimulation following anterior cruciate ligament reconstruction: a randomized controlled pilot study

BackgroundInadequate quadriceps strength following anterior cruciate ligament reconstruction (ACLR) often results in alterations in gait pattern that are usually reported during loading response. Neuro-muscular electrical stimulation (NMES) is frequently used to overcome this quadriceps weakness. Despite the beneficial effects of NMES, persistent deficits in strength and gait are reported. The aim of this study was to investigate the feasibility of applying quadriceps functional electrical stimulation (FES) during walking in addition to standard rehabilitation, in the initial stage of ACLR rehabilitation.MethodsSubjects were randomized to quadriceps FES synchronized with walking group (n = 10) or quadriceps NMES (duty cycle of 10 s on/10 s off) group (n = 13). Both interventions were performed for 10 min three days a week, in addition to a standard rehabilitation program. Assessments were performed up to 2 weeks before the ACLR (pre-ACLR), and 4 weeks postoperatively. Outcomes measured were gait speed, single limb stance gait symmetry, quadriceps isometric peak strength ratio (peak strength at 4 weeks/peak strength pre-ACLR) and peak strength inter-limb symmetry. Gait outcomes were also assessed 1-week post-surgery.ResultsSubjects in both groups regained pre-ACLR gait speed and symmetry after 4 weeks of rehabilitation, with no difference between groups. However, although pre-ACLR quadriceps peak strength was similar between groups (FES - 205 Nm, NMES − 225 Nm, p = 0.605), subjects in the FES group regained 82% of their pre-quadriceps strength compared to 47% in the NMES group (p = 0.02). In addition, after 4 weeks, the FES group had significantly better inter-limb strength symmetry 0.63 ± 0.15 vs. 0.39 ± 0.18 in the NMES group (p = 0.01).ConclusionsQuadriceps FES combined with traditional rehabilitation is a feasible, early intervention treatment option, post-ACLR. Furthermore, at 4 weeks post-surgery, FES was more effective in recovering quadriceps muscle strength than was NMES. While spatiotemporal gait parameters did not differ between groups, kinetic and kinematic studies may be useful to further understand the effects of quadriceps FES post-ACLR. The promising results of this preliminary investigation suggest that such studies are warranted.Trial registrationISRCTN 02817399. First posted June 29, 2016.

Time course of interlimb strength transfer after unilateral handgrip training

"Cross-education" is the increase in strength or functional performance of an untrained limb after unilateral training. A major limitation for clinical translation from unilateral injury includes knowledge on the minimum time for the emergence of crossed effects. Therefore, the primary purpose was to characterize the time course of bilateral strength changes during both "traditional" ( n = 11) and "daily" ( n = 8) unilateral handgrip training in neurologically intact participants. Traditional training included five sets of five maximal voluntary handgrip contractions 3 times/wk for 6 wk whereas daily training included the same number of sessions and contractions but over 18 consecutive days. Three pre- and one posttest session evaluated strength, muscle activation, and reflex excitability bilaterally. Time course information was assessed by recording handgrip force for every contraction in the trained limb and from a single contraction on every third training session in the untrained limb. Six weeks of traditional training increased handgrip strength in the trained limb after the 9th session whereas the untrained limb was stronger after the 12th session. This was accompanied by increased peak muscle activation and bilateral alterations in Hoffmann reflex excitability. Daily training revealed a similar number of sessions (15) were required to induce significant strength gains in the untrained limb (7.8% compared with 12.5%) in approximately half the duration of traditional training. Therefore, minimizing rest days may improve the efficiency of unilateral training when the trained limb is not the focus. Establishing a "dose" for the time course of adaptation to strength training is paramount for effective translation to rehabilitative interventions. NEW & NOTEWORTHY Unilateral handgrip training using a "traditional" protocol (3 times/wk; 6 wk) increased strength bilaterally after 9 (trained arm) and 12 (untrained arm) sessions. "Daily" training (18 consecutive days) increased strength in the untrained limb in a similar number of training sessions, which was accomplished in approximately half the time. Within clinical populations when the focus is on the untrained limb, reducing rest days may optimize the recovery of strength.

Correlation between quadriceps and hamstrings inter-limb strength asymmetry with change of direction and sprint in U21 elite soccer-players

The aim of this study was to investigate the relationship between in quadriceps and hamstrings inter-limb strength asymmetry and change of direction, sprinting and jumping abilities in U21 elite soccer players. Twenty-seven soccer players volunteered for this study. Isokinetic quadriceps and hamstrings peak torque was measured at high and low angular velocities, both in concentric and eccentric modalities. Performance in agility T-test, 20 + 20 m shuttle-test, 10 m and 30 m sprint, squat jump (SJ) and counter-movement jump (CMJ), were measured. Overall, time on agility T-test and 20 + 20 m shuttle-test was moderately and positively correlated with the quadriceps and hamstrings inter-limb eccentric peak torque asymmetry, both at high and low angular velocities. In addition, time on 10 m and 30 m sprints was moderately and positively correlated with the hamstrings inter-limb high-velocity concentric peak torque asymmetry. SJ and CMJ showed trivial to small correlations with hamstrings and quadriceps inter-limb peak torque asymmetry. The present results provide further information insight the role of lower-limb muscle strength balance in COD, sprinting and jumping performance.