Assessing muscle strength asymmetry via a unilateral stance isometric mid-thigh pull

Purpose: The purpose of this study was to investigate the within-session reliability of bilateral and unilateral stance isometric mid-thigh pull (IMTP) force-time characteristics including peak force (PF), relative PF and impulse at time bands (0-100, 0-200, 0-250 and 0-300 ms); and to compare isometric force-time characteristics between right and left and dominant (D) and non–dominant (ND) limbs. Methods: Professional male Rugby league and multi-sport collegiate male athletes (n=54, age 23.4 ± 4.2 years, height 1.80 ± 0.05 m, mass:88.9 ± 12.9 kg) performed 3 bilateral IMTP trials, and 3 unilateral stance IMTP trials per leg 60 on a force plate sampling at 600 Hz. Results: Intraclass correlation coefficients (ICC) and coefficients of variation (CV) demonstrated high-within session reliability for bilateral and unilateral IMTP PF (ICC =.94, CV = 4.7–5.5%). Lower reliability measures and greater variability were observed for bilateral and unilateral IMTP impulse at time bands (ICC =.81-.88, CV =7.7-11.8%). Paired sample t-tests and Cohen’s d effect sizes revealed no significant differences for all isometric force-time characteristics between right and left limbs in collegiate male athletes (p >.05, d ≤0.32) and professional rugby league players (p >.05, d ≤0.11), however significant differences were found between D and ND limbs in male collegiate athletes (p <.001, d = 0.43–0.91) and professional rugby league players (p < .001, d = 0.27–0.46). Conclusion: This study demonstrated high within-session reliability for unilateral stance IMTP PF;revealing significant differences in isometric force-time characteristics between D and ND limbs in male athletes

A comparison of dynamic strength index between team-sport athletes

The purpose of this study was to examine the differences in countermovement jump peak force (CMJ-PF), isometric mid-thigh pull peak force (IMTP-PF), and resultant dynamic strength index (DSI) values between team-sport athletes. One hundred and fifteen male and female team-sport athletes performed the CMJ and IMTP to determine peak force (CMJ-PF and IMTP-PF, respectively). Statistically and practically significant differences (p ≤ 0.050; d = 0.49–1.32) in CMJ-PF were evident between teams. Specifically, the greatest CMJ-PFs were produced by the male cricket players and were followed in order by the male basketball, male soccer, female netball, female cricket, and female soccer players. Statistically and practically significant differences (p ≤ 0.045; d = 0.64–1.78) in IMTP-PF existed among sports teams, with the greatest IMTP-PFs were produced by the male soccer players and were followed in order by the male cricket, male basketball, female netball, female soccer, and female cricket players. Statistically and practically significant differences (p ≤ 0.050; d = 0.92–1.44) in DSI were found between teams. These findings demonstrate that CMJ-PF, IMTP-PF, and DSI differ between sports teams and provide normative data for ballistic and isometric PF measures. Strength and conditioning coaches should consider relative changes in CMJ-PF and IMTP-PF when assessing DSI ratios

Comparison of change of direction speed performance and asymmetries between team-sport athletes : application of change of direction deficit

The purpose of this study was twofold: (1) to examine differences in change of direction (COD) performance and asymmetries between team-sports while considering the effects of sex and sport; (2) to evaluate the relationship between linear speed, COD completion time, and COD deficit. A total of 115 (56 males, 59 females) athletes active in cricket, soccer, netball, and basketball performed the 505 for both left and right limbs and a 10-m sprint test. All team-sports displayed directional dominance (i.e., faster turning performance/shorter COD deficits towards a direction) (p ≤ 0.001, g = −0.62 to −0.96, −11.0% to −28.4%) with, male cricketers tending to demonstrate the greatest COD deficit asymmetries between directions compared to other team-sports (28.4 ± 26.5%, g = 0.19–0.85), while female netballers displayed the lowest asymmetries (11.0 ± 10.1%, g = 0.14–0.86). Differences in sprint and COD performance were observed between sexes and sports, with males demonstrating faster 10-m sprint times, and 505 times compared to females of the same sport. Male soccer and male cricketers displayed shorter COD deficits compared to females of the same sport; however, female court athletes demonstrated shorter COD deficits compared to male court athletes. Large significant associations (ρ = 0.631–0.643, p < 0.001) between 505 time and COD deficit were revealed, while trivial, non-significant associations (ρ ≤ −0.094, p ≥ 0.320) between COD deficit and 10-m sprint times were observed. In conclusion, male and female team-sport athletes display significant asymmetries and directional dominance during a high approach velocity 180° turning task. Coaches and practitioners are advised to apply the COD deficit for a more isolated measure of COD ability (i.e., not biased towards athletes with superior acceleration and linear speed) and perform COD speed assessments from both directions to establish directional dominance and create a COD symmetry profile

The application of change of direction deficit to evaluate cutting ability

The purpose of this study was to examine the application of the change of direction deficit (CODD) to a 90° cut test in order to examine whether CODD provides a unique evaluation of an individual’s cutting ability. Thirty-six male collegiate team–sport (23 Rugby/ 13 Soccer) athletes (age: 20 ± 1.4 years; height: 1.80 ± 0.08 m; mass: 83 ± 13.2 kg) participated in the study. Each athlete performed 3 trials of a 20 m sprint (with 5 m and 10 m splits) and 2 change of direction [COD] tests (90° cut and 505 tests) cutting/ turning from both limbs. Completion times for all sprint and COD tests were measured using timing cells. For both COD tests, CODD was determined (COD completion time – 10 m sprint time). Pearson’s correlation was used to explore relationships between sprint times and CODD and completion times. Significant (P 0.05) trivial to small correlations (r ≤ 0.199) were found between sprint variables and 90° cut CODD. Significant (P < 0.001) large to very large correlations (r ≥ 0.531) were revealed between left and right 90° cut and 90° cut CODD. The results suggest the CODD could be applied to isolate and assess cutting ability in COD speed tests that involve a single cutting maneuver. Failure to inspect CODD could lead to incorrect evaluation of an athletes cutting or COD ability

The effect of angle and velocity on change of direction biomechanics : an angle-velocity trade-off

Changes of direction (CODs) are key manoeuvres linked to decisive moments in sport and are also key actions associated with lower limb injuries. During sport athletes perform a diverse range of CODs, from various approach velocities and angles, thus the ability to change direction safely and quickly is of great interest. To our knowledge, a comprehensive review examining the influence of angle and velocity on change of direction (COD) biomechanics does not exist. Findings of previous research indicate the biomechanical demands of CODs are ‘angle’ and ‘velocity’ dependent and are both critical factors that affect the technical execution of directional changes, deceleration and reacceleration requirements, knee joint loading, and lower limb muscle activity. Thus, these two factors regulate the progression and regression in COD intensity. Specifically, faster and sharper CODs elevate the relative risk of injury due to the greater associative knee joint loading; however, faster and sharper directional changes are key manoeuvres for successful performance in multidirectional sport, which subsequently creates a ‘performance-injury conflict’ for practitioners and athletes. This conflict, however, may be mediated by an athlete’s physical capacity (i.e. ability to rapidly produce force and neuromuscular control). Furthermore, an ‘angle-velocity trade-off’ exists during CODs, whereby faster approaches compromise the execution of the intended COD; this is influenced by an athlete’s physical capacity. Therefore, practitioners and researchers should acknowledge and understand the implications of angle and velocity on COD biomechanics when: (1) interpreting biomechanical research; (2) coaching COD technique; (3) designing and prescribing COD training and injury reduction programs; (4) conditioning athletes to tolerate the physical demands of directional changes; (5) screening COD technique; and (6) progressing and regressing COD intensity, specifically when working with novice or previously injured athletes rehabilitating from an injury

Role of the penultimate foot contact during change of direction : implications on performance and risk of injury

Most change of direction biomechanical investigations and current technique guidelines focus on the role of the final foot contact (plant foot contact). However, it is evident that the braking characteristics during the penultimate foot contact play an integral role in deceleration prior to directional changes ≥ 60°; and can therefore, be described as a “preparatory step”. In this review, we examine the role of the penultimate foot contact on change of direction performance and associated biomechanical injury risk factors, and provide technical guidelines for coaching the “preparatory step” during change of direction, to enhance performance and reduce risk of injury

The effect of training interventions on change of direction biomechanics associated with increased anterior cruciate ligament loading : a scoping review

Change of direction (COD) manoeuvres are associated with anterior cruciate ligament (ACL) injury risk due to the propensity to generate large multiplanar knee joint loads. Given the short- and long-term consequences of ACL injury, practitioners are interested in methods that reduce knee joint loads and subsequent ACL loading. An effective strategy to reduce ACL loading is modifying an athlete's movement mechanics to reduce knee joint loading. The purpose of this scoping review was to critically appraise and comprehensively synthesise the existing literature related to the effects of training interventions on COD biomechanics associated with increased knee joint loads and subsequent ACL loading, and identify gaps and recommend areas for future research. A review of the literature was conducted using Medline and Sport DISCUS databases. Inclusion criteria consisted of pre-post analysis of a COD task, a minimum 4-week training intervention, and assessments of biomechanical characteristics associated with increased ACL loading. Of the 1,027 articles identified, 22 were included in the scoping review. Based on current literature, balance training and COD technique modification are the most effective training modalities for reducing knee joint loading (small to moderate effect sizes). One study reported dynamic core stability training was effective in reducing knee joint loads, but further research is needed to definitively confirm the efficacy of this method. Perturbation-enhanced plyometric training, the F-MARC 11 + soccer specific warm-up, Oslo Neuromuscular warm-up, and resistance training are ineffective training modalities to reduce COD knee joint loads. Conflicting findings have been observed for the Core-Pac and mixed training programme. Consequently, practitioners should consider incorporating balance and COD technique modification drills into their athletes' training programmes to reduce potentially hazardous knee joint loads when changing direction. However, training intervention studies can be improved by investigating larger sample sizes (> 20), including a control group, acknowledging measurement error when interpreting their findings, and considering performance implications, to confirm the effectiveness of training interventions and improve adherence

Assessing asymmetries in change of direction speed performance; application of change of direction deficit

The aims of this study were to quantify asymmetries in change of direction (COD) performance via completion time and COD deficit, and determine its influence on asymmetry profiling of COD ability. A secondary aim was to evaluate the relationship between linear speed, 505 time and COD deficit. Forty-three youth netball athletes (age: 15.4 ± 1.1 years, height: 1.71 ± 0.06 m, mass: 63.3 ± 6.6 kg) performed the 505 for both left and right limbs and a 10 m sprint test. Asymmetries in 505 completion time and COD deficit were quantified for dominant (D) (faster) and non-dominant (ND) (slower) directions. Paired sample t-tests revealed significant differences between D and ND directions for 505 time and COD deficit (p < 0.0001, g = -0.53 to -0.60). Substantially greater asymmetries for COD deficit were observed compared to 505 time (p < 0.0001, g = 1.03). Only two subjects displayed an asymmetry ≥10% based on 505 times. Conversely, based on COD deficit, 21 subjects demonstrated asymmetries ≥10%. Large significant associations were observed between 505 time and COD deficit (r = 0.500-0.593, p ≤ 0.002). Large significant inverse associations were demonstrated between 10 m sprint time and COD deficit (r = -0.539 to -0.633, p ≤ 0.001) indicating faster athletes had longer COD deficits. Nine subjects were classified differently for COD ability when comparing standardized scores for 505 time versus COD deficit. Quantification of asymmetries in COD ability should be based on COD deficits; inspection of 505 times only could lead to misinterpretations of an athlete’s COD symmetry and COD ability. Faster youth netball athletes demonstrate longer COD deficits, thus, researchers and practitioners are encouraged to improve their youth netball athletes’ ability to rapidly decelerate, change direction and reaccelerate from 180° turns

The effect of hip joint angle on isometric midthigh pull kinetics

The aim of this study were to compare isometric midthigh pull (IMTP) peak force (PF), time-specific force values (100-, 150-, and 200 ms), rate of force development (RFD) at predetermined time bands (0–100, 0–150, and 0–200 ms) and net forces between 2 commonly adopted hip joint angles (145°[hip145] and 175°[hip175]) with a 145° standardized knee angle. Twenty-eight collegiate athletes (age: 21.7 ± 1.5 years, height: 1.75 ± 0.08 m, mass: 81.5 ± 8.4 kg) performed 2 IMTP trials at each hip joint angle in a randomized counterbalanced order. A subgroup (n = 10) performed the IMTP testing 7 days later to establish the between-session reliability. Intraclass correlation coefficients (ICCs) and coefficient of variation (CV) demonstrated high within-session reliability and acceptable variability for all IMTP kinetics at each posture (ICC ≥ 0.86, CV ≤ 13.7%), excluding hip175 RFD 0–100 ms and net force at 100 ms which demonstrated greater variability (CV = 18.1–18.5%). High between-session reliability and acceptable variability were observed for all IMTP kinetics at each posture (ICC = 0.72–0.97, CV = 4.5–12.8%), excluding RFD 0–100 ms which demonstrated greater variability for both postures. Hip145 produced significantly greater time-specific force values (p ≤ 0.025, g = 0.25–0.28), RFD at predetermined time bands (p ≤ 0.001, g = 0.59–0.78), and net forces (p ≤ 0.001, g = 0.57–0.74) compared with hip175. Trivial nonsignificant differences were demonstrated between postures for PF and force at 100 ms (p > 0.05, g ≤ 0.14). Significantly greater body weights (weighing period force) were observed with hip175 compared with hip145 (p < 0.001, g = 0.74). Coaches should consider administering a hip145 for IMTP testing as greater IMTP kinetics and lower levels of pretension during the weighing period are achieved with this posture

Differences in biomechanical determinants of ACL injury risk in Change of Direction tasks between males and females: A systematic review and meta-analysis

Background Change of direction (COD) movements are associated with non-contact anterior cruciate ligament (ACL) injuries in multidirectional sports. Females appear at increased risk compared to males, which could be attributable to whole body kinematic strategies and greater multiplanar knee joint loads (KJLs) during COD which can increase ACL loading. Objective The aim of this systematic review and meta-analysis was to examine and quantitatively synthesise the evidence for differences between males and females regarding KJLs and their biomechanical determinants (whole body kinematic strategies determining KJLs) during COD tasks. Methods Databases including SPORTDiscus, Web of Science, and PubMed were systematically searched (July 2021–June 2023) for studies that compared differences in knee joint loads and biomechanical determinants of KJLs during COD between males and females. Inclusion criteria were: (1) females and males with no prior history of ACL injury (18–40 years); (2) examined biomechanical determinants of KJLs and/ or KJLs during COD tasks > 20°; (3) compared ≥ 1 outcome measure between males and females. Studies published between 2000 and 2023 examining a cutting task > 20° with a preceding approach run that compared KJLs or the whole body multiplanar kinematics associated with them, between sexes, using three-dimensional motion analysis. Results This meta-analysis included 17 studies with a pooled sample size of 451 participants (227 males, 224 females). Meta-analysis revealed females displayed significantly less peak knee flexion during stance (SMD: 0.374, 95% CI 0.098–0.649, p = 0.008, I2: 0%); greater knee abduction at initial contact (IC) (SMD: 0.687, 95% CI 0.299–1.076, p = 0.001, I2: 55%); less hip internal rotation (SMD: 0.437, 95% CI 0.134–0.741, p = 0.005, I2: 34%) and hip abduction at IC (SMD: −0.454, 95% CI 0.151–0.758, p = 0.003, I2: 33%). No significant differences were observed between males and females for any internal or externally applied KJLs. All retrieved studies failed to control for strength, resistance training or skill history status. Conclusion No differences were observed in KJLs between males and females despite females displaying greater knee abduction at IC and less peak knee flexion during the stance phase of CODs, which are visual characteristics of non-contact ACL injury. Further research is required to examine if this translates to a similar injury risk, considering morphological differences in strain characteristics of the ACL between males and females. This observation may in part explain the disproportionate ACL injury incidence in female multidirectional athletes. Further higher quality controlled research is required whereby participants are matched by skill training history, resistance training history and strength status to ensure an appropriate comparison between males and females