Quadriceps and Hamstrings Activation Peaks Earlier as Athletes Repeatedly Hop, but There are Differences Depending on ACL Reconstruction Technique.

Background: After Anterior Cruciate Ligament Reconstruction (ACLR) athletes face the challenge of regaining their previous competitive level while avoiding re-injury and early knee joint cartilage degeneration. Quadriceps and hamstrings strength reductions and neuromuscular alterations potentially related to risk of re-injury are present after ACLR and relate to deficits in muscle activation. Design: Cross-sectional laboratory study. Purpose: To examine quadriceps and hamstrings muscle activation during repeated hops in healthy pivoting-sport athletes and those who had undergone ACLR (bone-tendon-bone and semitendinosus graft) who had met functional criteria allowing return to training. Methods: Surface electromyography (SEMG) was recorded from vastus medialis and lateralis and medial and lateral hamstrings bilaterally during 30 seconds' repeated hopping in male athletes on average eight months after ACLR surgery (5-12 months). All patients underwent hamstring (HS) (n=24) or bone-tendon-bone (BTB) reconstruction (n=20) and were compared to healthy controls (n=31). The SEMG signals were normalized to those obtained during maximal voluntary isometric contraction. Results: A significant time shift in peak muscle activation (earlier) was seen for: vastus medialis and vastus lateralis activation in the control group, in the BTB group's healthy (but not injured) leg and both legs of the HS group. A significant time shift in peak muscle activation was seen for lateral hamstrings (earlier) in all but the BTB group's injured leg and the medial hamstrings in the control group only. Lower peak activation levels of the vastus lateralis (p\<0.001) and vastus medialis (p\<0.001) were observed in the injured compared to healthy legs and lower peak lateral hamstrings activity (p\<0.009) in the injured leg compared to control leg. Decline in medial hamstring peak activation (p\<0.022) was observed between 1st and 3rd phase of the hop cycle in all groups. Conclusion: Repeated hop testing revealed quadriceps and hamstring activation differences within ACLR athletes, and compared to healthy controls, that would be missed with single hop tests. Level of evidence: 3.

Between-Limb Symmetry in ACL and Tibiofemoral Contact Forces in Athletes After ACL Reconstruction and Clearance for Return to Sport.

Background: Current return-to-sport (RTS) criteria after anterior cruciate ligament (ACL) reconstruction (ACLR) include demonstrating symmetry in functional and strength tests. It remains unknown if at the time that athletes are cleared to RTS, they exhibit between-limb symmetry in ACL and tibiofemoral contact forces or if these forces are comparable with those in uninjured athletes. Purposes: To (1) examine ACL and tibiofemoral contact forces in athletes who underwent ACLR and were cleared to RTS and (2) compare the involved leg to the healthy contralateral leg and healthy controls during functional tasks. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 26 male athletes who underwent ACLR were tested at the time of RTS during tasks that included single-leg vertical, horizontal, and side jumps; cutting maneuvers; and high-intensity running. We used an electromyography-constrained musculoskeletal modeling workflow to estimate ACL and tibiofemoral contact forces and compared the results with those of 23 healthy male participants. Results: The ACLR group presented no differences in peak tibiofemoral contact forces in the involved limb compared with the control group. However, there were significant between-limb differences mainly due to higher contact forces in the uninvolved (healthy) limb of the ACLR group compared with the control group. In the ACLR group, ACL forces were significantly higher in the uninvolved limb compared with the involved limb during cutting and running. Lateral contact forces were lower in the involved compared with the uninvolved limb, with large effect sizes during cutting (d = 1.14; P < .001) and running (d = 1.10; P < .001). Conclusion: Current discharge criteria for clearance to RTS after ACLR did not ensure the restoration of symmetric loading in our cohort of male athletes. ACL force asymmetry was observed during cutting and running, in addition to knee loading asymmetries on several tasks tested.

Single leg vertical jump performance identifies knee function deficits at return to sport after ACL reconstruction in male athletes.

OBJECTIVES: Vertical jump performance (height) is a more representative metric for knee function than horizontal hop performance (distance) in healthy individuals. It is not known what the biomechanical status of athletes after anterior cruciate ligament (ACL) reconstruction (ACLR) is at the time they are cleared to return to sport (RTS) or whether vertical performance metrics better evaluate knee function. METHODS: Standard marker-based motion capture and electromyography (EMG) were collected from 26 male athletes cleared to RTS after ACLR and 22 control healthy subjects during single leg vertical jumps (SLJ) and single leg drop jumps (SLDJ). Performance outcomes, jump height and the Reactive Strength Index, were calculated. Sagittal plane kinematics, joint moments and joint work were obtained using inverse dynamics and lower limb muscle forces were computed using an EMG-constrained musculoskeletal model. Muscle contribution was calculated as a percentage of the impulse of all muscle forces in the model. Between-limb and between-group differences were explored using mixed models analyses. RESULTS: Jump performance, assessed by jump height and Reactive Strength Index, was significantly lower in the involved than the uninvolved limb and controls, with large effect sizes. For the ACLR group, jump height limb symmetry index was 83% and 77% during the SLJ and SLDJ, respectively. Work generation was significantly less in the involved knee compared to uninvolved limb and controls during the SLJ (p<0.001; d=1.19; p=0.003, d=0.91, respectively) and during the SLDJ (p<0.001; d=1.54; p=0.002, d=1.05, respectively). Hamstrings muscle contribution was greater in the involved compared to the uninvolved limb and controls, whereas soleus contribution was lower in the involved limb compared to controls. CONCLUSIONS: During vertical jumps, male athletes after ACLR at RTS still exhibit knee biomechanical deficits, despite symmetry in horizontal functional performance and strength tests. Vertical performance metrics like jump height and RSI can better identify interlimb asymmetries than the more commonly used hop distance and should be included in the testing battery for the RTS.

Single leg hop for distance symmetry masks lower limb biomechanics: time to discuss hop distance as decision criterion for return to sport after ACL reconstruction?

BACKGROUND: We evaluated the lower limb status of athletes after anterior cruciate ligament reconstruction (ACLR) during the propulsion and landing phases of a single leg hop for distance (SLHD) task after they had been cleared to return to sport. We wanted to evaluate the biomechanical components of the involved (operated) and uninvolved legs of athletes with ACLR and compare these legs with those of uninjured athletes (controls). METHODS: We captured standard video-based three-dimensional motion and electromyography (EMG) in 26 athletes after ACLR and 23 healthy controls during SLHD and calculated lower limb and trunk kinematics. We calculated lower limb joint moments and work using inverse dynamics and computed lower limb muscle forces using an EMG-constrained musculoskeletal modelling approach. Between-limb (within ACLR athletes) and between-group differences (between ACLR athletes and controls) were evaluated using paired and independent sample t-tests, respectively. RESULTS: Significant differences in kinematics (effect sizes ranging from 0.42 to 1.56), moments (0.39 to 1.08), and joint work contribution (0.55 to 1.04) were seen between the involved and uninvolved legs, as well as between groups. Athletes after ACLR achieved a 97%±4% limb symmetry index in hop distance but the symmetry in work done by the knee during propulsion was only 69%. During landing, the involved knee absorbed less work than the uninvolved, while the uninvolved knee absorbed more work than the control group. Athletes after ACLR compensated for lower knee work with greater hip work contribution and by landing with more hip flexion, anterior pelvis tilt, and trunk flexion. CONCLUSION: Symmetry in performance on a SLHD test does not ensure symmetry in lower limb biomechanics. The distance hopped is a poor measure of knee function, and largely reflects hip and ankle function. Male athletes after ACLR selectively unload the involved limb but outperform controls on the uninvolved knee.

Symmetry in Triple Hop Distance Hides Asymmetries in Knee Function After ACL Reconstruction in Athletes at Return to Sports.

BACKGROUND: After anterior cruciate ligament reconstruction (ACLR), a battery of strength and hop tests is frequently used to determine the readiness of an athlete to successfully return to sports. However, the anterior cruciate ligament reinjury rate remains alarmingly high. PURPOSE: To evaluate the lower limb function of athletes after ACLR at the time when they had been cleared to return to sports (RTS). We aimed to evaluate if passing discharge criteria ensures restoration of normal lower limb biomechanics in terms of kinematics, kinetics, work, and percentage work contribution during a triple hop for distance. STUDY DESIGN: Controlled laboratory study. METHODS: Integrated 3-dimensional motion analysis was performed in 24 male athletes after ACLR when cleared to RTS and 23 healthy male controls during the triple-hop test. The criteria for RTS were (1) clearance by the surgeon and the physical therapist, (2) completion of a sports-specific on-field rehabilitation program, and (3) limb symmetry index >90% after quadriceps strength and hop battery tests. Lower limb and trunk kinematics, as well as knee joint moments and work, were calculated. Between-limb differences (within athletes after ACLR) and between-group differences (between ACLR and control groups) were evaluated using mixed linear models. RESULTS: Although achieving 97% limb symmetry in distance hopped and displaying almost 80% symmetry for knee work absorption in the second rebound and third landing, the ACLR cohorts demonstrated only 51% and 66% limb symmetry for knee work generation in the first and second rebound phases, respectively. During both work generation phases of the triple hop, the relative contribution of the involved knee was significantly smaller, with a prominent compensation from the hip joint (P < .001, for all phases) as compared with the uninvolved limb and the controls. In addition, patients deployed a whole body compensatory strategy to account for the between-limb differences in knee function, mainly at the hip, pelvis, and trunk. CONCLUSION: Symmetry in the triple hop for distance masked important deficits in the knee joint work. These differences were more prominent during work generation (concentric-propulsive) than work absorption (eccentric-landing). CLINICAL RELEVANCE: Symmetry in hop distance during the triple hop test masked significant asymmetries in knee function after ACLR and might not be the appropriate outcome to use as a discharge criterion. Differences between limbs in athletes after ACLR were more prominent during the power generation than the absorption phase.

Current perspectives and clinical practice of physiotherapists on assessment, rehabilitation, and return to sport criteria after anterior cruciate ligament injury and reconstruction. An online survey of 538 physiotherapists.

OBJECTIVES: To evaluate the perspectives and clinical practice of physiotherapists regarding rehabilitation after anterior cruciate ligament reconstruction (ACLR). DESIGN: Online survey. SETTING: Survey platform. PARTICIPANTS: Greek physiotherapists. OUTCOME MEASURES: The survey consisted of 7 sections: participant demographics, importance of ACLR rehabilitation, clinical measurements, practice, criteria to progress rehabilitation, return to running and return to sport. RESULTS: Significant variability in measures and criteria used for clinical decision-making were found including: limb symmetry in strength and function, knee range of motion and effusion, progression, and return to sport criteria. The majority of the practitioners (28.3%) extrapolate knee strength from hop capacity. Return to running ranged from 3 to 5 months post-operatively reflecting that this was tied to physical capacities, not time from surgery. 70.0% of the Greek physiotherapists would allow return to sport ≤9 months after ACLR. Agreement was found in using: physical measures, function, and dynamic stability in ACLR rehabilitation, but the mode and interpretation varied substantially. Less than 29.0% of the physiotherapists reported using patient-reported outcome measures in their decision-making. CONCLUSION: Current ACLR rehabilitation practices in Greece are largely not aligned with the contemporary scientific evidence and guidelines.

Evaluating lower limb tendinopathy with Victorian Institute of Sport Assessment (VISA) questionnaires: a systematic review shows very-low-quality evidence for their content and structural validity-part I.

PURPOSE: The Victorian Institute of Sport Assessment (Achilles tendon-VISA-A, greater trochanteric pain syndrome-VISA-G, proximal hamstring tendinopathy-VISA-H, patellar tendon-VISA-P) questionnaires are widely used in research and clinical practice; however, no systematic reviews have formally evaluated their content, structural, and cross-cultural validity evidence. The measurement properties referring to content, structural and cross-cultural validity of the VISA questionnaires were appraised and synthesized. METHODS: The systematic review was conducted according to Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) methodology. PubMed, Cochrane, CINAHL, EMBASE, Web of Science, SportsDiscus, grey literature, and reference lists were searched. Development studies and cross-cultural adaptations (12 languages) assessing content or structural validity of the VISA questionnaires were included and two reviewers assessed their methodological quality. Evidence for content (relevance, comprehensiveness, and comprehensibility), structural, and cross-cultural validity was synthesized. A modified Grading of Recommendations Assessment Development and Evaluation (GRADE) approach was applied to evidence synthesis. RESULTS: The VISA-A presented very-low-quality evidence of sufficient relevance, insufficient comprehensiveness, and inconsistent comprehensibility. VISA-G displayed moderate-quality evidence for sufficient comprehensibility and very-low-quality evidence of sufficient relevance and comprehensiveness. The VISA-P presented very-low-quality evidence of sufficient relevance, insufficient comprehensiveness, and inconsistent comprehensibility, while VISA-H presented very-low evidence of insufficient content validity. VISA-A displayed low-quality evidence for structural validity concerning unidimensionality and internal structure, while VISA-H presented low-quality evidence of insufficient unidimensionality. The structural validity of VISA-G and VISA-P were indeterminate and inconsistent, respectively. Internal consistency for VISA-G, VISA-H, and VISA-P was indeterminate. No studies evaluated cross-cultural validity, while measurement invariance across sexes was assessed in one study. CONCLUSIONS: Only very-low-quality evidence exists for the content and structural validity of VISA questionnaires when assessing the severity of symptoms and disability in patients with lower limb tendinopathies. LEVEL OF EVIDENCE: IV. REGISTRATION: PROSPERO reference-CRD42019126595.

A systematic review evaluating the clinimetric properties of the Victorian Institute of Sport Assessment (VISA) questionnaires for lower limb tendinopathy shows moderate to high-quality evidence for sufficient reliability, validity and responsiveness-part II.

PURPOSE: The evaluation of measurement properties such as reliability, measurement error, construct validity, and responsiveness provides information on the quality of the scale as a whole, rather than on an item level. We aimed to synthesize the measurement properties referring to reliability, measurement error, construct validity, and responsiveness of the Victorian Institute of Sport Assessment questionnaires (Achilles tendon-VISA-A, greater trochanteric pain syndrome-VISA-G, proximal hamstring tendinopathy-VISA-H, patellar tendon-VISA-P). METHODS: A systematic review was conducted according to Consensus-based Standards for the Selection of Health Measurement Instruments methodology (COSMIN). PubMed, Cochrane, CINAHL, EMBASE, Web of Science, SportsDiscus, grey literature, and reference lists were searched. Studies assessing the measurement properties concerning reliability, validity, and responsiveness of the VISA questionnaires in patients with lower limb tendinopathies were included. Two reviewers assessed the methodological quality of studies assessing reliability, validity, and responsiveness using the COSMIN guidelines and the evidence for these measurement properties. A modified Grading of Recommendations Assessment Development and Evaluation (GRADE) approach was applied to the evidence synthesis. RESULTS: There is moderate-quality evidence for sufficient VISA-A, VISA-G, and VISA-P reliability. There is moderate-quality evidence for sufficient VISA-G and VISA-P measurement error, and high-quality evidence for sufficient construct validity for all the VISA questionnaires. Furthermore, high-quality evidence exists with regard to VISA-A for sufficient responsiveness in patients with insertional Achilles tendinopathy following conservative interventions. CONCLUSIONS: Sufficient reliability, measurement error, construct validity and responsiveness were found for the VISA questionnaires with variable quality of evidence except for VISA-A which displayed insufficient measurement error. LEVEL OF EVIDENCE: IV. REGISTRATION DETAILS: Prospero (CRD42018107671); PROSPERO reference-CRD42019126595.

Lumbo-pelvic proprioception in sitting is impaired in subgroups of low back pain-But the clinical utility of the differences is unclear. A systematic review and meta-analysis.

BACKGROUND: Altered spinal postures and altered motor control observed among people with non-specific low back pain have been associated with abnormal processing of sensory inputs. Evidence indicates that patients with non-specific low back pain have impaired lumbo-pelvic proprioceptive acuity compared to asymptomatic individuals. OBJECTIVE: To systematically review seated lumbo-pelvic proprioception among people with non-specific low back pain. METHODS: Five electronic databases were searched to identify studies comparing lumbo-pelvic proprioception using active repositioning accuracy in sitting posture in individuals with and without non-specific low back pain. Study quality was assessed by using a modified Downs and Black's checklist. Risk of bias was assessed using an adapted tool for cross-sectional design and case-control studies. We performed meta-analysis using a random effects model. Meta-analyses included subgroup analyses according to disability level, directional subgrouping pattern, and availability of vision during testing. We rated the quality of evidence using the GRADE approach. RESULTS: 16 studies met the eligibility criteria. Pooled meta-analyses were possible for absolute error, variable error, and constant error, measured in sagittal and transverse planes. There is very low and low certainty evidence of greater absolute and variable repositioning error in seated tasks among non-specific low back pain patients overall compared to asymptomatic individuals (sagittal plane). Subgroup analyses indicate moderate certainty evidence of greater absolute and variable error in seated tasks among directional subgroups of adults with non-specific low back pain, along with weaker evidence (low-very low certainty) of greater constant error. DISCUSSION: Lumbo-pelvic proprioception is impaired among people with non-specific low back pain. However, the low certainty of evidence, the small magnitude of error observed and the calculated "noise" of proprioception measures, suggest that any observed differences in lumbo-pelvic proprioception may be of limited clinical utility. PROSPERO-ID: CRD42018107671.

Vertical and Horizontal Hop Performance: Contributions of the Hip, Knee, and Ankle.

BACKGROUND: Single-leg vertical and horizontal hop tests are commonly used to assess performance of healthy athletes and as a measure of progress during rehabilitation from knee injury. It is unclear if they measure similar aspects of leg function, as the relative joint contributions of the hip, knee, and ankle joints during propulsion and landing are unknown. HYPOTHESIS: The proportion of work done by the hip, knee, and ankle will not be the same for these 2 jump types and will vary for propulsive and landing phases. STUDY DESIGN: Cross-sectional cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: Twenty physically active participants completed instrumented single-leg hop analysis in both vertical and horizontal directions. Joint peak power, work generated or absorbed, and percentage contribution of each joint during propulsive and landing phases were compared between tasks using paired t tests. RESULTS: Vertical hop was performed with roughly similar contributions of the hip, knee, and ankle for both propulsion (31%, 34%, 35%, respectively) and landing (29%, 34%, 37%, respectively). Horizontal hop distance was mostly (87%) determined by the hip and ankle (44% and 43%), but landing was mostly (65%) performed by the knee with lesser contribution from the hip and ankle (24% and 11%). Propulsive phase showed a proximal-to-distal temporal sequence for both hop types, but landing was more complex. CONCLUSION: Performance during vertical and horizontal hops (jump height and jump distance, respectively) measures different aspects of hip, knee, and ankle function during the propulsive and landing phases. CLINICAL RELEVANCE: Assessment of knee joint function during rehabilitation should not be done using a horizontal hop. The knee contributes about a third to vertical hop height, but only about an eighth to horizontal hop distance. Practitioners carrying out performance testing using either vertical or horizontal hops should be mindful of the relative contributions for meaningful training inferences to be derived.

Notions of "optimal" posture are loaded with meaning. Perceptions of sitting posture among asymptomatic members of the community.

BACKGROUND: Notions of "optimal" posture are widespread in modern society and strongly interconnected with preconceived beliefs. OBJECTIVES: To quantitatively evaluate spinal posture among members of the community during habitual sitting, and when asked to assume an "optimal" posture. DESIGN: Observational study. METHODS: Marker-based kinematic analyses of the head, spine, and pelvis were conducted on 100 individuals. Habitual sitting posture and self-perceived "optimal" posture, and whether participants believed that their habitual sitting reflected an "optimal" posture, were evaluated. The Wilcoxon signed-rank test assessed angular differences between the two postures adopted. Exploratory post-hoc analyses were conducted by using the Mann-Whitney U test to assess differences between genders. RESULTS: None of the participants stated that their habitual sitting was "optimal". Statistically significant differences were observed in most of the measured angles (p < 0.001) between habitual and self-perceived "optimal" posture. In habitual sitting posture, a significant interaction with gender was found only in the thoracolumbar (p < 0.05) and pelvic (p < 0.001) angles, with small effect sizes. In self-perceived "optimal" posture females were more extended in the head, upper thoracic, lower thoracic, lumbar and pelvic (p < 0.01) regions, than the males. CONCLUSIONS: A group of young, asymptomatic participants, consistently changed their habitual sitting posture to a more upright posture when asked to assume an "optimal" sitting posture, although the amount of change observed varied between spinal regions. These findings also highlight gender differences in not just habitual sitting posture, but also the degree to which habitual sitting posture is modified when trying to assume an "optimal" sitting posture.

Measuring only hop distance during single leg hop testing is insufficient to detect deficits in knee function after ACL reconstruction: a systematic review and meta-analysis.

OBJECTIVE: To systematically review the biomechanical deficits after ACL reconstruction (ACLR) during single leg hop for distance (SLHD) testing and report these differences compared with the contralateral leg and with healthy controls. DESIGN: Systematic review with meta-analysis. DATA SOURCES: A systematic search in Pubmed (Ovid), EMBASE, CINAHL, Scopus, Web of Science, PEDro, SPORTDiscus, Cochrane Library, grey literature and trial registries, was conducted from inception to 1 April 2018. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Studies reporting kinematic, kinetic and/or electromyographic data of the ACLR limb during SLHD with no language limits. RESULTS: The literature review yielded 1551 articles and 19 studies met the inclusion criteria. Meta-analysis revealed strong evidence of lower peak knee flexion angle and knee flexion moments during landing compared with the uninjured leg and with controls. Also, moderate evidence (with large effect size) of lower knee power absorption during landing compared with the uninjured leg. No difference was found in peak vertical ground reaction force during landing. Subgroup analyses revealed that some kinematic variables do not restore with time and may even worsen. CONCLUSION: During SLHD several kinematic and kinetic deficits were detected between limbs after ACLR, despite adequate SLHD performance. Measuring only hop distance, even using the healthy leg as a reference, is insufficient to fully assess knee function after ACLR. PROSPERO trial registration number CRD42018087779.

Dual Kinect v2 system can capture lower limb kinematics reasonably well in a clinical setting: concurrent validity of a dual camera markerless motion capture system in professional football players.

OBJECTIVES: To determine whether a dual-camera markerless motion capture system can be used for lower limb kinematic evaluation in athletes in a preseason screening setting. DESIGN: Descriptive laboratory study. SETTING: Laboratory setting. PARTICIPANTS: Thirty-four (n=34) healthy athletes. MAIN OUTCOME MEASURES: Three dimensional lower limb kinematics during three functional tests: Single Leg Squat (SLS), Single Leg Jump, Modified Counter-movement Jump. The tests were simultaneously recorded using both a marker-based motion capture system and two Kinect v2 cameras using iPi Mocap Studio software. RESULTS: Excellent agreement between systems for the flexion/extension range of motion of the shin during all tests and for the thigh abduction/adduction during SLS were seen. For peak angles, results showed excellent agreement for knee flexion. Poor correlation was seen for the rotation movements. CONCLUSIONS: This study supports the use of dual Kinect v2 configuration with the iPi software as a valid tool for assessment of sagittal and frontal plane hip and knee kinematic parameters but not axial rotation in athletes.