MECHANICAL DETERMINANTS OF SPRINT PERFORMANCE IN ELITE AND SUB-ELITE FIELD HOCKEY PLAYERS

The aim of the present study was to investigate the difference in the horizontal mechanical determinants of sprint performance in highly-trained elite field hockey players versus sub-elite field hockey players. Thirty-five highly trained field hockey players (1 8 elite international players and 17 sub-elite players) were tested during the competitive season. They performed a maximal 40 meter sprint. Distance was tracked over time via a 312 Hz laser (Laser Technology, Inc) and used to calculate, for each individual, a horizontal force-velocity profile. Elite players showed a larger theoretical maximal horizontal velocity (vO) compared to the sub-elite hockey players. No significant differences in theoretical maximal horizontal force (FO) and horizontal power (Pmax) between the groups were observed. Large variability especially in the sub-elite groups was observed in FO and vO, indicating the potential for individualized training program focusing on the weaker parameter

INFLUENCE OF PLAYING LEVEL ON THE KINEMATICS AND KINETICS OF THE RUGBY SCRUM

The aim of this study was to examine the force production, lower body kinematics and kinetics of front row rugby union forwards during the engagement phase of a simulated rugby union scrum. Twenty-eight male front row players were divided into three groups; professional, senior and junior amateur players. Players performed five trials based on the International Rugby Board scrum engagement sequence. Three dimensional motion analysis and force plate data were used to determine joint angles and reaction forces both on the scrum machine and on the ground. Professional front row forwards generated significantly greater force during the engagement phase compared to both senior and junior amateur players. Professional players had a significantly greater knee abduction angle and generated larger peak hip joint power compared to both junior and senior players

Muscle tuning and preferred movement path: do we need a paradigm shift or should we redefine the old? – comment on Nigg et al.

In the feature paper “Muscle tuning and preferred movement path – a paradigm shift“, Benno Nigg and colleagues discuss that the impact and pronation paradigm should be abandoned as there is not enough biomechanical and epidemiological evidence supporting these paradigms. We agree that the paradigms, as defined in the paper, are currently not supported by strong scientific evidence however we argue that the lack of evidence originates from shortcomings in the methodological approach to these paradigms. In our commentary, we argue for a redefinition of the paradigms rather than defining two ‘new’ paradigms. A better methodological approach and definitions of the paradigms based on the current evidence are needed rather than to abandon them

FATIGUE-RELATED ASYMMETRY AND INSTABILITY DURING A 3200-M TIME-TRIAL PERFORMANCE IN HEALTHY RUNNERS

The purpose of this study was to examine fatigue effects on symmetry and stability during a maximal effort running time-trial m). Recreational runners had continuous recordings of 3D trunk acceleration parameters (spatio-temporal, RMS vector ratio, step symmetry, and stride regularity) during the lT. Statistical analysis was carried out using generalised estimating equations (GEE) to investigate longitudinal changes (laps two to eight) compared to baseline (lap one), while statistically adjusting for running speed. Runners had significantly longer contact times (4m lap onwards), higher mediolateral root mean square (RMS) ratio (3d lap onwards), lower vertical symmetry and vertical RMS ratio (final lap). Coaches could use these results to recognize, minimize, and delay fatigue related onset of asymmetries and instabilities possibly through training strategies

ENERGETIC COST OF RUNNNING STABILITY EVALUATED WITH WIRELESS TRUNK ACCELEROMETRY

The purpose of this study was to determine inter-individual variance in the energetic cost of running (Ec) using dynamic stability measures derived from a single tri-axial trunk accelerometer. These measures were extracted from fifteen male recreational runners at their fastest steady-state treadmill running speed. A select group of dynamic stability measures were entered in a hierarchical regression to explain Ec (kcal.km-1) after reducing dimensionality with factor analysis. Two dynamic stability parameters could explain an additional 9.9% of inter-individual variance in Ec over and above body mass, attributed to anteroposterior (AP) stride regularity (6.5%) and mediolateral (ML) sample entropy (3.4%). Our results suggest that recreational male runners with better stability in terms of greater AP stride consistency and greater ML trunk movement complexity have an energetic advantage at running speeds approximating race pace

THE EFFECT OF STEP WIDTH CONTROL ON LOAD CARRIAGE ECONOMY

The purpose of this study was to assess the influence of step width on load carriage economy. Fifteen healthy volunteers (age = 25 ± 3 years; stature = 1.78 ± 0.07 m; body mass = 73.6 ± 10.1 kg) completed three trials in a randomised order. Each trial differed by load carriage method and involved walking on a force-instrumented at 3km.h-1 with 0, 3, 12 and 20 kg. This protocol was then repeated with step width controlled to each participant’s preferred unloaded width. Relative load carriage economy was measured using the Extra Load Index (ELI). Load carriage economy was significantly worse in the head loading method compared to the other two method with step width uncontrolled (p = 0.02) and controlled (p = 0.02). For the trials where step width was uncontrolled, there was a significant difference in step width from unloaded walking between the different loading methods (p = 0.01) but no significant difference between load mass (p = 0.39). There was no difference in ELI between preferred and controlled step widths. Based on the data presented here, moderate alterations in step width caused by load carriage do not appear to influence load carriage economy

THE INFLUENCE OF HEEL HEIGHT ON ANKLE KINEMATICS DURING STANDING, WALKING, JOGGING AND SIDESTEPPING IN CHILDREN

The aim of this study was to quantify the effects of heel-forefoot height on ankle kinematics during locomotion in children. Measurements were taken by a motion capture system and a force plate on five children. They were asked to perform standing, walking, jogging and sidestepping in barefoot, low heel, standard heel and high heel shoe conditions. Results showed that rearfoot plantarflexion angle was different from shoe rake during standing. There was more ankle plantarflexion as heel height increased during walking, jogging and sidestepping. Ankle inversion velocity increased with shod condition but not significantly. High heel height will affect ankle kinematics during locomotion, which may increase the risk of foot problems. Children and their parents should choose footwear with caution

FORCE-SHARING BETWEEN TRICEPS SURAE MUSCLES DURING REHABILITATION EXERCISES FOR ACHILLES TENDINOPATHY

The purpose of this study was to determine individual muscle forces of the Triceps Surae during a range of rehabilitation exercises for Achilles tendinopathy. We used experimental data (N=4) and musculoskeletal modelling to estimate muscle force (dynamic optimization). We observed clear peak muscle force differences between exercises. In addition, the force-sharing strategies used by the participants (i.e., individual muscle contribution to the total force produced within the Triceps Surae) were different between exercises. These preliminary results could be helpful to objectively determine the progression in exercise loading throughout rehabilitation programs. Additionally, new information regarding the influence of the type of exercise on load distribution within the Triceps Surae may better orientate practitioners in the choice of exercise

ACUTE EFFECTS OF OUTDOOR SURFACES ON RUNNING GAIT SYMMETRY AND REGULARITY ASSESSED BY TRUNK ACCELEROMETRY

The purpose of this study was to investigate if trunk accelerometry measures were influenced by outdoor surface while running. A sample of highly-trained (n=12) and recreational (n=17) ran on three independent surfaces, namely asphalt, synthetic track, and wood-chip. Dependent accelerometry measures were step frequency (SFREQ), step symmetry (SSYM), stride regularity (SREG), axis contribution to total amplitude (RMSRATIO) and sample entropy (SEN). Surface effects on accelerometry measures were consistent for both running groups. Several significant differences existed between wood-chip and either asphalt or synthetic track. The results suggest that surface specific considerations should be made when quantifying trunk accelerometry measures related to running gait symmetry and regularity during running

EFFECT OF FOOTWEAR ON LOWER LIMB KINEMATICS IN CHILDREN DURING SIDESTEP

Wearing shoes has been shown to affect children’s gait and neuromuscular development. This study aims to evaluate the effect of supportive shoes and flexible shoes on children’s lower limb kinematics during sidestep. Fourteen children aged 6 to 13 years, with no foot deformity were recruited. A motion analysis system and a force plate were used for motion capture. Compared to jogging, sidestep has increased sagittal plane motion and a different frontal plane movement pattern. The supportive shoes allowed smaller midfoot sagittal range of motion (ROM) and higher peak knee flexion whereas flexible shoes showed increased motion in the first metatarsophalangeal joint (MPJ), midfoot and hip with increased ankle eversion velocity and knee less internally rotated. Conventional supportive school shoes allowed less motion in healthy children’s feet, thus affecting negatively on long term lower limb functional development