The effect of plyometric training and moderating variables on stretch-shortening cycle function and physical qualities in female post peak height velocity volleyball players.

Purpose: Although several studies investigated the effect of plyometric training on physical performance, there is a lack of clarity regarding the effectiveness of plyometric training or its moderator variables in youth female volleyball players. The primary aim of this study was to explore the effect of horizontal plyometric training on explosive stretch-shortening cycle hops and jumps in the vertical and horizontal directions in female post peak height velocity (PHV) volleyball players. The secondary aim was to assess the influence of participant and training related moderators on horizontal plyometric training in post-PHV volleyball players. Methods: A total of 23 post-PHV volleyball players participated in this 8-week intervention with horizontal plyometric exercises, twice a week. Pre-testing and post-testing included bilateral and unilateral vertical sub-maximal hopping, horizontal jumping and hopping, and a drop jump test. The effectiveness of the intervention was assessed using a paired t-test. The influence of internal moderators such as age, maturity and body mass and external moderators such as training volume were assessed using regression and correlation analysis. Results: An 8-week plyometric training improved sub-maximal hopping at 2.5 Hz left by 4.4%, bilateral sub-maximal hopping at 2.0 Hz by 9.5% and bilateral sub-maximal hopping at 2.2 Hz by 6.8% in post-PHV female volleyball players. Horizontal jumping and hopping, reactive strength index and other sub-maximal hopping conditions did not improve significantly. Body mass had a large moderating effect on vertical unilateral sub-maximal hopping at 2.5 Hz right (p = 0.010, η 2 = 0.314), vertical unilateral hopping at 3.0 Hz right (p = 0.035, η 2 = 0.170), and vertical unilateral hopping at 3.0 Hz left (p = 0.043, η 2 = 0.203). Training volume together with generalized joint hypermobility moderated right leg triple broad hop performance, whereas maturity and age did not moderate any variables. Conclusion: This study determined that 8 weeks of horizontal plyometric training can improve unilateral absolute leg stiffness in post-PHV female volleyball players, and this training effect can be moderated by body mass. Furthermore, the training effect on triple hopping performance on the right leg can be moderated by combined training volume with generalized joint hypermobility.

Effect of Footwear Versus Barefoot on Double-Leg Jump-Landing and Jump Height Measures: A Randomized Cross-Over Study.

Background: Assessing individuals in their own athletic footwear in clinics is common, but can affect movement, performance, and clinical measures. Purpose: The aim was to compare overall Landing Error Scoring System (LESS) scores, injury risk categorization, specific LESS errors, and jump heights between habitual athletic footwear and barefoot conditions. Study design: Randomized cross-over laboratory study. Methods: Eighty healthy individuals (55% male) completed the LESS following standard procedures (i.e., land from a 30-cm box to a distance of 50% of body height and then jump upwards maximally). Participants performed the LESS three times in two randomized conditions: footwear and barefoot. LESS data were extracted from 2D videos to compare group-level mean LESS scores, group-level and individual-level injury risk categorization (5-error threshold), specific landing errors, and jump heights between conditions. Results: LESS scores were significantly greater (0.3 errors, p=0.022) and jump heights were significantly lower (0.6 cm, p=0.029) in footwear than barefoot, but differences were trivial (d = 0.18 and -0.07, respectively) and not clinically meaningful. Although the number of high injury-risk participants was not statistically different at a group level (p=1.000); 27 individuals (33.8%) exhibited a clinically meaningful difference between conditions of one error or more in LESS score, categorization was inconsistent for 16.3% of individuals, and four of the 17 landing errors significantly differed between conditions. Conclusion: At a group level, habitual athletic footwear does not meaningfully influence LESS scores, risk categorization, or jump height. At an individual level, footwear can meaningfully affect LESS scores, risk categorization, and alter landing strategies. Use of consistent protocol and footwear is advised for assessing movement patterns and injury risk from the LESS given the unknown predictive value of this test barefoot. Level of Evidence: Level 3.©The Author(s).

Effect of an overhead goal on landing error scoring system and jump height measures.

OBJECTIVES: Compare overall Landing Error Scoring System (LESS) scores, risk categorisation, specific LESS errors, and double-leg jump-landing jump heights between overhead goal and no goal conditions. DESIGN: Randomised cross-over. SETTING: Laboratory. PARTICIPANTS: 76 (51% male). MAIN OUTCOME MEASURES: Participants landed from a 30-cm box to 50% of their body height and immediately jumped vertically for maximum height. Participants completed three trials under two random-ordered conditions: with and without overhead goal. Group-level mean LESS scores, risk categorisation (5-error threshold), specific landing errors, and jump heights were compared between conditions. RESULTS: Mean LESS scores were greater (0.3 errors, p < 0.001) with the overhead goal, but this small difference was not clinically meaningful. Similarly, although the number of high-risk participants was greater with the overhead goal (p = 0.039), the 9.2% difference was trivial. Participants jumped 2.7 cm higher with the overhead goal (p < 0.001) without affecting the occurrence of any specific LESS errors. DISCUSSION: Performing the LESS with an overhead goal enhances sport specificity and elicits greater vertical jump performances with minimal change in landing errors and injury-risk categorisation. Adding an overhead goal to LESS might enhance its suitability for injury risk screening, although the predictive value of LESS with an overhead goal needs confirmation.

Kinematics of recreational male runners in "super", minimalist and habitual shoes.

We conducted an exploratory analysis to compare running kinematics of 16 male recreational runners wearing Nike Vaporfly 4% (VP4), Saucony Endorphin racing flat (FLAT), and their habitual (OWN) footwear. We also explored potential relationships between kinematic and physiological changes. Runners (age: 33 ± 12 y, V˙ O2peak: 55.2 ± 4.3 ml · kg-1·min-1) attended 3 sessions after completing an V˙ O2peak test in which sagittal plane 3D kinematics at submaximal running speeds (60%, 70% and 80% ʋ V˙ O2peak) were collected alongside economy measures. Kinematics were compared using notched boxplots, and between-shoe kinematic differences were plotted against between-shoe economy differences. Across intensities, VP4 involved longer flight times (6.7 to 10.0 ms) and lower stance hip range of motion (~3°), and greater vertical pelvis displacement than FLAT (~0.4 cm). Peak dorsiflexion angles (~2°), ankle range of motion (1.0° to 3.9°), and plantarflexion velocities (11.3 to 89.0 deg · sec-1) were greatest in FLAT and lowest in VP4. Foot-ground angles were smaller in FLAT (2.5° to 3.6°). Select kinematic variables were moderately related to economy, with higher step frequencies and shorter step lengths in VP4 and FLAT associated with improved economy versus OWN. Footwear changes from OWN altered running kinematics. The most pronounced differences were observed in ankle, spatiotemporal, and foot-ground angle variables.

Clinical Implications of Landing Distance on Landing Error Scoring System Scores.

CONTEXT: The Landing Error Scoring System (LESS) screens for risk of noncontact anterior cruciate ligament injury. The LESS requires individuals to jump forward from a 30-cm box to a distance of 50% of their body height. However, different landing distances have been cited in the scientific literature. OBJECTIVE: To examine whether landing distance influences LESS outcomes. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS OR OTHER PARTICIPANTS: Seventy young active individuals (34 males, 36 females). INTERVENTION(S): Participants performed 3 × 30-cm jump-landing tasks under 2 landing conditions in randomized order: (1) 50% of body height (d50%), (2) self-selected distance (dss). MAIN OUTCOME MEASURE(S): Mean LESS scores, proportions of individuals categorized at high (LESS: ≥ 5 errors) and low (LESS: < 5 errors) injury risk, and landing distances were compared between conditions using generalized estimating equations. Consistency of risk categorization was examined using odds ratios (ORs) and McNemar tests. McNemar and Wilcoxon signed rank tests were used to compare the occurrence of specific LESS errors. RESULTS: Participants landed closer to the box under the dss condition (difference = -23.28 [95% CI = -20.73, -25.81]%, P < .001). Group mean LESS scores (difference = -0.01 [95% CI = -0.59, 0.57] error, P = .969) and risk categorization (OR = 0.94 [95% CI = 0.47, 1.88], P = .859) were similar between conditions. However, individual-level risk categorization was inconsistent in 33% of participants, as was the occurrence of specific errors. CONCLUSIONS: Using dss during the LESS might lead to different LESS errors and risk categorizations at an individual level than using d50%. Given that individual LESS scores are of primary interest in clinical and sport settings and the injury-risk threshold has not been validated for dss, we recommend use of the original LESS protocol. When only group mean LESS scores or proportions of at-risk individuals are of interest, using dss is feasible to facilitate the testing of large cohorts.

An exploration of normative values in New Zealand to inform the Targeted Interventions for Patellofemoral Pain approach.

BACKGROUND: The Targeted Interventions for Patellofemoral Pain studies (TIPPs) have identified three subgroups exist in United Kingdom and Turkish patellofemoral pain (PFP) populations: Strong; Weak and Tight; and Weak and Pronated, based on six clinical assessments. The thresholds used to develop the subgrouping algorithms were based on normative values sourced from various populations and countries. OBJECTIVES: Explore normative scores from the clinical assessments in a singular non-PFP population whilst considering potential differences between ethnicities and sex (primary aim). Revisit inter-rater reliability of each assessment (secondary aim). DESIGN: Cross-sectional and test-retest. METHOD: The six assessments; rectus femoris length, gastrocnemius length, patellar mobility, hip abductor strength, quadriceps strength, and Foot Posture index (FPI) were measured in 89 New Zealanders (34% Maori, 45% female). Two raters independently assessed 17 participants to examine inter-rater reliability. RESULTS: Significant interactions between ethnic group and sex were noted for rectus femoris length and patella mobility. Maori versus European males exhibited greater rectus femoris tightness (p = 0.001). Maori versus European females demonstrated greater patellar mobility (p = 0.002). Females were significantly weaker than males in normalised strength measures (p < 0.001), and had lower FPIs. Mean differences between testers for all measures were small and not significant, except for FPI which had a 2.0 point median difference (p = 0.021). CONCLUSIONS: Our results indicate that sex is an important factor worth considering within the TIPPs subgrouping approach, more than ethnicity, especially for the normalised strength measures. The sub-optimal reliability of FPI warrant reconsideration of its inclusion within TIPPs.

The Influence of Asymptomatic Hypermobility on Unanticipated Cutting Biomechanics.

BACKGROUND: Generalized joint hypermobility is an important risk factor for knee injuries, including to the anterior cruciate ligament (ACL). Examining movement patterns specific to hypermobile individuals during sport-specific movements could facilitate development of targeted recommendations and injury prevention programs for this population. HYPOTHESIS: Asymptomatic hypermobile participants will present kinematics measures suggestive of a greater risk of noncontact knee or ACL injuries. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: Forty-two (15 asymptomatic hypermobile and 27 nonhypermobile) individuals performed unanticipated side-step cutting on their dominant and nondominant legs. Ankle, knee, hip, pelvis, and trunk angles in all planes of motion were collected during the first 100 ms after initial contact using a 3-dimensional infrared system. Precontact foot-ground angles were also extracted. Data from hypermobile and nonhypermobile groups were compared using multiple regression models with sex as a confounder. When nonsignificant, the confounder was removed from the model. Effect sizes (Hedge g) were calculated in the presence of significant between-group differences. RESULTS: Hypermobile individuals presented with lower minimum knee valgus angles with a mean difference of 3.5° (P = 0.03, Hedge g = 0.69) and greater peak knee external rotation angles with a mean difference of -4.5° (P = 0.04, Hedge g = 0.70) during dominant leg cutting, and lower peak ankle plantarflexion angles with a mean difference of 4.5° (P = 0.03, Hedge g = 0.73) during nondominant leg cutting compared with nonhypermobile individuals. CONCLUSION: Based on current scientific evidence, however, the identified differences are not crucial biomechanical injury risk factors that could predispose asymptomatic hypermobile individuals to noncontact knee or ACL injuries. CLINICAL RELEVANCE: Further research is needed to highlight differences between hypermobility groups. Knowledge of the differences between these groups may change the physical activity recommendations, prevention of injury, and rehabilitation approaches.

Which jump-landing task best represents lower extremity and trunk kinematics of unanticipated cutting maneuver?

BACKGROUND: The double-leg jump-landing (DLJL) task is commonly used as a movement screen that can be implemented in large cohorts of athletes. However, it is debatable whether the DLJL is ecologically valid and reflects sporting requirements or injury-prone situations, such as cutting and pivoting. RESEARCH QUESTION: Which jump-landing movement variation best represents the kinematics of unanticipated side-step cutting? METHODS: Forty-two participants (25 males and 17 females) performed unanticipated side-step cutting and four jump-landing tasks: DLJL, rotated DLJL (DLJLrot), single-leg jump-landing (SLJL), and rotated SLJL (SLJLrot). Ankle, knee, hip, pelvis, and trunk angles and angular velocities, and pelvic linear accelerations were collected at initial contact and during the first 100 milliseconds after initial contact (minimum, maximum, and range values) using a three-dimensional infrared camera system and inertial measurement units. Pre-contact foot-ground angles and subjective task difficulty ratings were also recorded. Intraclass correlation coefficients (ICC) between cutting and jump-landing kinematics were calculated for each participant and jump-landing variation. Friedman tests with pairwise comparisons were then used to compare the degree of association between the four different jump-landing tasks at the specified time events and to compare the difficulty ratings. RESULTS: Considering the ICC values across the events of interest, the kinematics of the DLJL were the least associated with those of cutting (ICC = 0.00 to 0.81), and DLJLrot (ICC = 0.34 to 0.81) and SLJLrot (ICC = 0.31 to 0.80) biomechanics the most. Participants rated the perceived challenge of the single-leg tasks in a similar manner to cutting (p > 0.103), and the SLJLrot as the most difficult task (median = "neutral", mode = "neutral"). SIGNIFICANCE: Due to their biomechanical associations with cutting maneuver and subjectively-rated difficulty levels, both DLJLrot and SLJLrot may be more appropriate and ecologically valid for screening for risk of injury across a range of sports.

Factors influencing the Landing Error Scoring System: Systematic review with meta-analysis.

OBJECTIVES: Systematically review the literature addressing age, sex, previous injury, and intervention program as influencing factors of the Landing Error Scoring System. DESIGN: Systematic review with meta-analysis. METHODS: Three databases (PubMed, Web of Science®, and Scopus®) were searched on 1 April 2020. Original studies using the Landing Error Scoring System as primary outcome and exploring age, sex, previous injury, and intervention program were included, assessed for risk of bias, and critically appraised. Three meta-analyses were performed using one random and two mixed effect models with dependent variables: sex, previous injury and intervention program, respectively. Grading of Recommendations Assessment, Development and Evaluation was used to evaluate the strength of the evidence. PROSPERO registration number CRD42018107210. RESULTS: Fifty-two studies were included. Pooled data indicated that females have higher Landing Error Scoring System scores than males (p<0.001, mean difference=0.6 error). Participants with previous anterior cruciate ligament injury have higher LESS scores than healthy controls (p=0.004, mean difference 1.2 error). Neuromuscular training programs lasting a minimum of six weeks and other intervention programs decrease Landing Error Scoring System scores (p<0.001, mean difference 1.2 error and p=0.042, mean difference 0.5 error, respectively). There is limited evidence suggesting that age may influence Landing Error Scoring System scores in clinically meaningful manner. Overall, Grading of Recommendations Assessment, Development and Evaluation ratings suggest very low strength of evidence. CONCLUSIONS: History of anterior cruciate ligament injury and undertaking neuromuscular training for a minimum of six weeks meaningfully altered Landing Error Scoring System scores. These findings, however, should be interpreted cautiously considering the very low Grading of Recommendations Assessment, Development and Evaluation rating of the evidence.

Clinical Implications of Jump Distance on Landing Error Scoring System Scores.

CONTEXT: The Landing Error Scoring System (LESS) screens for risk of non-contact Anterior Cruciate Ligament injury. The LESS requires individuals to jump forward from a 30-cm box to a distance of 50% of their body height. However, different landing distances have been used in the scientific literature. OBJECTIVE: To examine whether landing distance influences LESS outcomes. DESIGN: Cross-sectional. SETTING: Laboratory. PARTICIPANTS: Seventy young active individuals (34 males, 36 females). INTERVENTION: Participants performed 3 × 30-cm jump-landing tasks under two landing conditions in randomized order: (1) 50% of body height (d50%), (2) self-selected distance (dss). MAIN OUTCOME MEASURES: Mean LESS scores, proportions of individuals categorized at high (LESS ≥ 5 errors) and low (LESS < 5 errors) injury risk, and landing distances were compared between conditions using Generalized Estimating Equations. Consistency of risk categorization was examined using odds ratios (OR) and McNemar's tests. McNemar's and Wilcoxon signed rank tests were used to compare occurrence of specific LESS errors. RESULTS: Participants landed significantly closer to the box under the dss condition (difference: -23.28 [-20.73 to -25.81]%, p < 0.001). Group mean LESS scores (difference: -0.01 [-0.59 to 0.57] error, p = 0.969) and risk categorization (OR: 0.94 [0.47 to 1.88], p = 0.859) were similar between conditions. However, individual-level risk categorization was inconsistent in 33% of participants, as was the occurrence of specific errors. CONCLUSION: Using dss during LESS might lead to different LESS errors and risk categorization at an individual level compared to d50%. Given that individual LESS scores are of primary interest in clinical and sport settings, and the injury-risk threshold has not been validated for dss, the use of the original LESS protocol is recommended. When only group mean LESS scores or proportions of at risk individuals is of interest, using dss is possible to facilitate large cohort testing.

Landing Error Scoring System scores change with knowledge of scoring criteria and prior performance.

OBJECTIVE: To examine if the knowledge of scoring criteria and prior performance influence Landing Error Scoring System (LESS) outcomes. DESIGN: Cross-sectional. SETTING: Laboratory. PARTICIPANTS: Thirty individuals. MAIN OUTCOME MEASURES: The LESS was tested at Baseline and one week later under two conditions: Pre and Post information. For the Post condition, LESS items were explained to participants, as were their individual Baseline scores. Mean LESS scores and number of individuals categorized at high and low risk were compared between Pre and Post using paired t-tests and McNemar's tests, respectively. McNemar's tests were also used to compare proportions of specific LESS errors between Pre and Post conditions. RESULTS: Mean LESS Post scores (4.7 ± 1.2 errors) were significantly lower than Pre scores (6.6 ± 2.0 errors, p < 0.001) as was the number of individuals at high risk (25 vs 10 participants, p < 0.001). A significantly lower proportion of participants scored an error for the joint displacement item of LESS Post compared to Pre condition (p < 0.001). CONCLUSION: When using the LESS, it is important that tested individuals have no knowledge of scoring criteria or previous errors for a valid assessment of innate jump-landing movement patterns and injury risk.

Is the Landing Error Scoring System Reliable and Valid? A Systematic Review.

CONTEXT: The Landing Error Scoring System (LESS) is a clinical tool often used in research and practice to identify athletes presenting high injury-risk biomechanical patterns during a jump-landing task. OBJECTIVE: To systematically review the literature addressing the psychometric properties of the LESS. DATA SOURCES: Three electronic databases (PubMed, Web of Science, and Scopus) were searched on March 28, 2018, using the term "Landing Error Scoring System." STUDY SELECTION: All studies using the LESS as main outcome measure and addressing its reliability, validity against motion capture system, and predictive validity were included. Original English-language studies published in peer-reviewed journals were reviewed. Studies using modified versions of the LESS were excluded. STUDY DESIGN: Systematic literature review. LEVEL OF EVIDENCE: Level 4. DATA EXTRACTION: Study design, population, LESS testing procedures, LESS scores, statistical analysis, and main results were extracted from studies using a standardized template. RESULTS: Ten studies met inclusion criteria and were appraised using Newcastle-Ottawa Quality Assessment Scale adapted for cross-sectional studies. The overall LESS score demonstrated good-to-excellent intrarater (intraclass correlation coefficient [ICC], 0.82-0.99), interrater (ICC, 0.83-0.92), and intersession reliability (ICC, 0.81). The validity of the overall LESS score against 3-dimensional jump-landing biomechanics was good when individuals were divided into 4 quartiles based on LESS scores. The validity of individual LESS items versus 3-dimensional motion capture data was moderate-to-excellent for most of the items addressing key risk factors for anterior cruciate ligament (ACL) injury. The predictive value of the LESS for ACL and other noncontact lower-extremity injuries remains uncertain based on the current scientific evidence. CONCLUSION: The LESS is a reliable screening tool. However, further work is needed to improve the LESS validity against motion capture system and confirm its predictive validity for ACL and other noncontact lower-extremity injuries.