Suzi Edwards

Does a drop landing represent a whole skill landing and is this moderated by fatigue

This study aimed to determine whether the landing phase of a drop landing (DL) differed with respect to a complete jumping and landing task, a spike jump (SJ), and whether fatigue altered the landing of these movements. Fourteen male volleyball players performed five DL and SJ in a counterbalanced order under two experimental conditions: non‐fatigued and fatigued. Fatigue, induced by repetitive jumping sets, was confirmed by decrements in vertical jump height >25% and increased blood lactate >6 mmol/L. Each landing task was characterized by the resultant ground reaction forces (GRF), sagittal plane kinematics and muscle recruitment patterns of six lower extremity muscles. Two‐way repeated analysis of variance results indicated a main effect of movement on many of the GRF, kinematic and electromyographic variables characterizing landing, indicating that the two tasks required substantially different lower limb biomechanics during landing. Although fatigue did not alter the GRF in either task, there were significant movement × fatigue condition interactions. The significant between‐task differences in the biomechanical variables characterizing landing and the differential effects of fatigue on each landing task, question the validity of using a DL as an experimental task to investigate lower limb landing mechanics of whole jumping and landing movements.

A lower limb assessment tool for athletes at risk of developing patellar tendinopathy

PURPOSE Patellar tendon abnormality (PTA) on diagnostic imaging is part of the diagnostic criteria for patellar tendinopathy. PTA and altered landing strategies are primary risk factors that increase the likelihood of asymptomatic athletes developing patellar tendinopathy. Therefore, the aim of this study was to examine the risk factors that are predictors of the presence and severity of a PTA in junior pre-elite athletes. METHODS Ten junior pre-elite male basketball athletes with a PTA were matched with 10 athletes with normal patellar tendons. Participants had patellar tendon morphology, Victorian Institute of Sport Assessment (VISA) score, body composition, lower limb flexibility, and maximum vertical jump height measured before performing five successful stop-jump tasks. During each stop-jump task, both two-dimensional and three-dimensional kinematics and ground reaction forces were recorded. Multiple regression analyses were used to identify factors for estimating PTA presence and severity, and discriminate analysis was used to classify PTA presence. RESULTS Sixty-eight percent of variance for presence of a PTA was accounted for by hip joint range of motion (ROM) and knee joint angle at initial foot-ground contact (IC) during stop-jump task and quadriceps flexibility, whereas hip joint ROM during stop-jump task and VISA score accounted for 62% of variance for PTA severity. Prediction of the presence of a PTA was achieved with 95% accuracy and 95% cross-validation. CONCLUSIONS An easily implemented, reliable, and valid movement screening tool composed of three criteria enables coaches and/or clinicians to predict the presence and severity of a PTA in asymptomatic athletes. This enables identification of asymptomatic athletes at higher risk of developing patellar tendinopathy, which allows the development of effective preventative measures to aid in the reduction of patellar tendinopathy injury prevalence.

Lower limb movement symmetry cannot be assumed when investigating the stop-jump landing.

PURPOSE When investigating lower limb landing biomechanics, researchers often assume movement symmetry between a participants right and left lower limbs for the simplicity of data collection and analysis, although landing tasks often involve dual-limb motion. However, whether lower limb symmetry can be assumed when investigating dynamic, sport-specific movements such as the stop-jump has not been investigated. Therefore, this study aimed to determine whether there were any significant differences in selected kinetic, kinematic, and muscle activation patterns characterizing lower limb biomechanics displayed by the dominant limb compared with the nondominant limb of participants during a stop-jump task. METHODS Sixteen male athletes with normal patellar tendons on diagnostic imaging performed five successful stop-jump trials. Patellar tendon forces (FPT), ground reaction forces, three-dimensional kinematics, and EMG activity of seven lower limb muscles were recorded for the dominant and nondominant lower limbs during each trial. RESULTS During the horizontal landing phase, the dominant lower limb sustained a significantly higher FPT and peak net knee joint extension moment compared with the nondominant lower limb. Furthermore, during the vertical landing phase, the dominant lower limb sustained significantly lower vertical but higher posterior ground reaction forces compared with the nondominant lower limb. Other variables did not significantly vary as a function of lower limb dominance. CONCLUSIONS It is recommended that researchers clearly identify their primary outcome variables and ensure that their experimental design, particularly in terms of lower limb dominance, provides an appropriate framework to investigate possible mechanics underlying unilateral and bilateral knee joint injuries during dual-limb movements such as the stop-jump task.

The Role of the Trunk Control in Athletic Performance of a Reactive Change-of-Direction Task

Abstract Edwards, S, Austin, AP, and Bird, SP. The role of the trunk control in athletic performance of a reactive change-of-direction task. J Strength Cond Res 31(1): 126–139, 2017—Agility is vital to success in team sport competition with the trunk argued to play a key role in sport performance. This study explored the role of trunk control during a reactive change-of-direction task (R-COD) and field-based measures of athletic performance. Twenty male players completed field-based athletic performance assessments (modified Illinois agility test [mIAT], 3 repetition maximum back squat, and 5 countermovement jumps [CMJ]) and R-CODs, during which 3-dimensional ground reaction forces and kinematics were recorded. Trunk control was assessed as the sum of the trunk relative to the pelvis range of motion (ROM) in all 3 planes during the R-COD. Participants with the highest (HIGH, n = 7) and lowest (LOW, n = 7) trunk ROM values were grouped. The HIGH group achieved significantly shorter mIAT time duration, higher CMJ height, and lower knee flexion angles, greater trunk lateral flexion and rotation relative to pelvis, and greater angular momentum during the R-COD compared with the LOW group. Superior athletic performance was associated with decreased trunk control (high trunk ROM) during the R-COD. Although this study suggested that trunk control is a vital component of performance, it is unknown whether this trunk control is inherent or an effect of training history, nor does not support current optimal athletic performance recommendation of decreased trunk motion during R-COD.

Asymptomatic players with a patellar tendon abnormality do not adapt their landing mechanics when fatigued

ABSTRACT This study aimed to explore how asymptomatic athletes with a patellar tendon abnormality (PTA), who are at high risk of developing patellar tendinopathy, alter their landing technique and net patellar tendon loads generated in response to fatigue. Seven asymptomatic players with a PTA performed five successful vertical stop-jump trials before and after a fatigue protocol. Fatigue protocol involved participants repeatedly performing sets of 30 submaximal jump exercises on a sledge apparatus followed by 30 s rest until the task failure criteria were reached. Three-dimensional ground reaction forces, lower limb kinematics and net peak patellar tendon force were recorded during the stop-jump task. No significant between-fatigue condition differences in net patellar tendon loading, or most secondary outcome variables were observed. Only some fatigue changes were seen during the vertical landing phase. Asymptomatic PTA participants did not modify their landing technique or net patellar tendon loading during a stop-jump task in response to fatigue. The lack of between-fatigue condition differences displayed by the asymptomatic PTA participants during both landing phases suggest that these individuals may not be capable of sufficient movement variability in their landing strategies to adapt to fatigue.

Consistency of kinematic and kinetic patterns during a prolonged spell of cricket fast bowling: an exploratory laboratory study

ABSTRACT Due to the high incidence of lumbar spine injury in fast bowlers, international cricket organisations advocate limits on workload for bowlers under 19 years of age in training/matches. The purpose of this study was to determine whether significant changes in either fast bowling technique or movement variability could be detected throughout a 10-over bowling spell that exceeded the recommended limit. Twenty-five junior male fast bowlers bowled at competition pace while three-dimensional kinematic and kinetic data were collected for the leading leg, trunk and bowling arm. Separate analyses for the mean and within-participant standard deviation of each variable were performed using repeated measures factorial analyses of variance and computation of effect sizes. No substantial changes were observed in mean values or variability of any kinematic, kinetic or performance variables, which instead revealed a high degree of consistency in kinematic and kinetic patterns. Therefore, the suggestion that exceeding the workload limit per spell causes technique- and loading-related changes associated with lumbar injury risk is not valid and cannot be used to justify the restriction of bowling workload. For injury prevention, the focus instead should be on the long-term effect of repeated spells and on the fast bowling technique itself.

Caution using data from triaxial accelerometers housed in player tracking units during running

ABSTRACT Usage of accelerometers within player tracking devices in sport to quantify load, vertical ground reaction force (vGRF) or energy expenditure is contrary to placement guidelines. This study aimed to determine whether trunk-mounted accelerometers were a valid and reliable method to estimate thoracic segment or centre of gravity (COG) acceleration or vGRF, and the whether the elasticised harness contributes to the overestimation of acceleration. Ten male amateur rugby players performed five linear running tasks per lower limb at three speeds, twice, each with a different player tracking unit. Three-dimensional data were recorded and triaxial accelerometers were attached lateral to the device on the harness and skin and both shanks. Accelerometers demonstrated poor reliability (ICC:0.0–0.67), high variability (CV%:14–33%) and change in mean (41–160%), and were not valid to estimate vertical acceleration of the COG and thoracic segment nor vGRF. Caution is advised when utilising trunk-mounted triaxial accelerometer data as it is not a valid or reliable means to estimate peak vertical acceleration for its thoracic location nor whole-body COG acceleration or vGRF during running. To improve player tracking instrument validity and reliability, a new attachment method and/or harness material(s), that reduce or eliminate extraneous acceleration during running, are urgently required.