5954 research outputs found
Sort by
THE ROAD TO 2024 OLYMPIC GOLD MEDAL: A CASE REPORT OF THREE ELITE BEACH VOLLEYBALL PLAYERS
Get PDFThe anthropometrics, limbs maximum isometric force and jump performance in beach-volleyball players were described. Three female elite beach volleyball players selected to participate in the 2022 World Championships Circuit were recruited to participate in the study. Body composition, squat, supine, and rowing isometric maximal force, and power test, squat, and countermovement jumps were measured. Body fat percentage varied between 13 and 24.2%. Squat, supine and rowing isometric force (N) presented median (M) and interquartile ranges (IQR) of 145 (128, 186.6), 40 (33, 66.75) and 65.2 (57.6, 76,6). The height (cm), absolute (W) and relative power (W/kg) M and IQR range values were 32.55 (27.32, 35.10), 32.69 (31.50, 34.69) and 44.18 (40.65, 46.30). Findings can guide morphological and physical training for elite players
LOWER LIMB ASYMMETRY DURING THE SKELETON PUSH START
Get PDFThe aim of this study was to identify the presence and performance implication of asymmetry within the skeleton push start. Motion data were captured on 13 international skeleton athletes, using a custom 9-camera computer vision system. 6 maximal effort pushes were captured allowing the reconstruction of a 0–15 m push. Intra-limb differences for spatiotemporal variables and the change in velocity (ΔV) across a step were analysed. A negative relationship existed between 5 – 15 m split time and ΔV across a stride. Athletes who maximise their velocity across a stride were more likely to perform well in the skeleton push start. Though athletes employed different strategies based on inside and outside leg ΔV to achieve their performance outcome
KNEE JOINT LOADING OF SCISSOR-KICK JUMP LANDINGS: A COMPARISON BETWEEN ELITE AND RECREATIONAL BADMINTON PLAYERS
Get PDFBadminton players at all levels perform a variety of badminton specific jump-stroke movements during training and match play, which expose their knees to high loads during the subsequent landing phase. Therefore, the purpose of this study was to compare the knee joint kinematics and kinetics of elite and recreational male badminton players during scissor-kick jump landings. Ten Danish national male badminton players and 10 recreational male badminton players completed a series of simulated scissor-kick jumps in a biomechanical laboratory. Three-dimensional knee joint angles and external joint moments were recorded for the non-racket leg during the landing phase. One-dimensional statistical parametric mapping was used to statistically compare the landing kinematics and kinetics of the knee for elite and recreational players. The landing phase was highly similar between groups and associated with high external knee abduction moments, particularly for the recreational players, which resemble those previously reported in sports specific single-leg landing situations with high ACL injury risk. The only significant difference observed between elite and recreational players were found in the push-off phase, where elite players generate more power from the muscles around the knee joint, through greater external adduction and inwards rotations moments, allowing them to accelerate significantly faster forward upon landing compared to recreational players. The high knee loads players experience during scissor-kick landings may contribute to the high incidence of knee injuries observed in both elite and recreational badminton
UPPER LIMB KINETICS BETWEEN TWO DIFFERENT STANCES IN A TENNIS FOREHAND DRIVE: A PRELIMINARY STUDY
Get PDFThe purpose of this study was to compare the joint moments of force of the upper limb between one forehand drive performed in quasi-static stance (QSS) (with both feet on the ground at the impact) and one forehand performed with a dynamic frontal weight transfer stance (DS) (with both feet off the ground at the impact). One high-performance tennis player was recorded with an optical system with a frequency of 240Hz during both techniques. Three forehands in QSS and three in DS were selected for analysis. Results demonstrated that the forehand performed with QSS could present higher moments of force, especially in the shoulder joint abdu/addu (QSS:45.5 vs DS:52.8 Nm), moreover, the DS presented higher racket velocity compared with the QSS forehand drive (DS: 32.7(0.4) vs QSS:31.5(0.4) m/s). The results of this study could present an important information for tennis coaches as for their players in order to understand which forehand technique creates higher joint loads, and, therefore adapt the practice for each situation
TREADMILL RUNNING: HOW LONG BEFORE BIOMECHANICS REACH A STEADY STATE?
Get PDFThe purpose of this study was to investigate short-term biomechanical changes during treadmill running and whether footwear influenced this adaptation. Forty-five adults with experience in treadmill running over the last year performed an 8.5-min trial at a self-selected speed with three different midsole hardness. Kinetics, kinematics, soft-tissue vibrations and electromyographic activity were recorded at minutes 0, 2, 4, 6 and 8. The fastest adjustments were an increase of active peak and foot inversion. Step frequency and lower limb stiffness decreased then plateaued at minute 6. Duty factor, contact and flight times didn’t reach a plateau. No time effect was found for passive peak, loading rate, leg muscle activity and soft-tissue vibrations. We recommend a minimum habituation period of 8-minutes to ensure that a maximum of biomechanical parameters reach a steady state
THE EFFECTIVENESS OF BOXING HEADGUARDS WITH THERMOPLASTIC POLYURETHANE INSERTS IN MITIGATING LINEAR AND ANGULAR IMPACT ACCELERATIONS TO THE HEAD USING A DYNAMIC HEAD MODEL
Get PDFThe purpose of this study was to examine the capacity of commercial boxing headguards and an experimental thermoplastic polyurethane (TPU) liner to mitigate the risk of concussions. Headguards were tested dynamically across a range of impact locations using simulated head impacts with a pneumatic horizontal impactor to explore the behavior of the headguards. This study showed differences between headguard types in mitigating concussion risk resulting from linear and angular accelerations of the head. The results demonstrated that introducing TPU into a headguard reduces concussion risk most prominently by decreasing peak resultant linear acceleration (PRLA) and peak resultant rotational acceleration (PRRA) of the head. This study provides information about the performance of commercial headguards and suggests an avenue for further TPU research
INFLUENCE OF TECHNICAL SIGNATURE ON ROWING ERGOMETER PERFORMANCE
Get PDFThe purpose of this study was to evaluate the influence of technical signature parameters on rowing ergometer performance defined as power mean handle. 20 high levels rowers were evaluated at their competitive stroke rate on a RowPerfect 3 ergometer. Linear-mixed model analyses revealed that mean power handle was influenced by the power produced by the legs, trunk and arms during the drive phase. The ability to produce the highest relative maximal power throughout the drive phase, whatever its peak value, was important to improve segments powers. Finally, trunk power was enhanced by an earlier peak power of the trunk, and higher trunk and pelvis ranges of motion. These technical elements are important to consider for rowing performance
ARE THIGH MUSCLE ACTIVATION PATTERNS DURING DROP JUMPS DEPENDENT ON SEX AND FATIGUE? A PILOT STUDY IN COMPETITIVE SOCCER PLAYERS
Get PDFThe purpose of this study was to identify whether sex- and fatigue-dependent effects occur in muscle activation patterns during drop jumps. Therefore, 12 (5 female, 7 male) competitive soccer players performed five drop jumps (DJs) in a rested and fatigued state. Lactate, jump height, maximum knee flexion angle and the quadriceps to hamstring muscle activation ratio (QHGRF ratio) were compared via repeated-measures MANOVA, and effect sizes were used for interpretation. In the fatigued state, jump height and maximum knee flexion angles were reduced (large effect), and the left limb showed an non-significant medium effect towards an increased QHGRF ratio. Additionally, a sex-specific medium effect of the QHGRF ratio of the left limb indicates a higher QHGRF ratio for males. This indicates a tendency towards a quadriceps-dominant landing strategy in at least one limb
THE EFFECT OF TAI CHI TRAINING ON ANKLE PROPRIOCEPTION IN PARTICIPANTS WITH CHRONIC ANKLE INSTABILITY
Get PDFObjective: To determine the effect of Tai Chi training on ankle proprioception in participants with Chronic Ankle Instability (CAI). Design: Randomized controlled trial. Method: Forty participants with CAI were randomly divided into a Tai Chi group and a control group, with 20 participants in each group. The Tai Chi group underwent 24-styled simplified Tai Chi rehabilitation training 3 times a week for 8 weeks, while the Control group did not undergo any rehabilitation training. The angular displacement of ankle proprioception (kinesthesia) was collected from both groups before and after rehabilitation training for data analysis. Result: After 8 weeks of training, participants in the Tai Chi group showed significant improvement in ankle proprioception (
UPPER BODY VIBRATION TRANSMISSION IN CYCLING
Get PDFThis study aimed to identify the effects of vibration frequency on upper body transmissibility in cycling. We hypothesized, that vibrations around 15 Hz are transmitted more intensely to the upper body than vibrations around 45 Hz. The effect of the independent variable vibration frequency on the dependent variable vibration transfer ratio of the torso and the hand-arm system was analysed. Nineteen amateur cyclists (75.1 ± 5.7 kg, 1.78 ± 0.05 m) performed test rides on a racing bike which was mounted on two vibration plates. During the vibration interventions VIB LOW (Front-/ Rear dropout: 17 Hz / 12 Hz), VIB MED (Front-/ Rear dropout: 32 Hz / 27 Hz) and VIB HIGH (Front-/ Rear dropout: 47 Hz / 42 Hz) accelerations at the lower back, neck, hand and acromion were recorded with 3D sensitive accelerometers. Transfer ratios occurred in between 1.82 ± 0.51 from the lower back to the neck for VIB LOW and 0.06 ± 0.03 from the hand to the shoulder for VIB HIGH. The lower back – neck and hand - shoulder transfer ratios decreased from VIB LOW to MED to HIGH significantly, which supports our initial hypothesis. These results suggest that vibrations around/below 15 Hz contribute substantially to upper body vibration exposure in cycling