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SPATIAL, TEMPORAL, AND KINETIC VARIABLES DURING THE EARLY ACCELERATION PHASE OF SPRINTING
Get PDFThis study evaluated the relationships between spatial, temporal, and kinetic variables and velocity during the early acceleration phase of sprinting. Ten women and ten men performed sprints across two force platforms. Pearson’s and partial correlation coefficients removing the effect of sex were used to assess relationships between step and sprint velocity during the first four steps and a variety of variables. Significant (p ≤ 0.05) correlations and partial correlations were found between overall sprinting velocity and subject height, countermovement jump, average horizontal force, vertical force, H:V force, stride frequency, foot contact duration and step distance. During the acceleration phase of sprint training, it may be important to liberalize step length after the first two steps. A variety of other recommendations are made
ACUTE EFFECTS OF SMALL CHANGES IN CRANK LENGTH ON TORQUE WAVEFORM DURING SUBMAXIMAL PEDALLING
Get PDFThe purpose of the present study was to evaluate the acute effects of small changes in crank-arm length and pedalling power on crank torque-angle profile during seated cycling. Twelve amateur cyclists participated and performed 12 sets of 5-min submaximal pedalling on a special cycle ergometer (4 intensities x 3 crank lengths). Principal Component Analysis technique was used to analyse ten crank torque-angle curves of the right leg. A longer crank increased the crank torque of the front leg (30-125º) in order to lift the rear leg (200-320º), contrary to the effect of increasing pedalling power. Furthermore, pedalling with the longest crank required higher torque values after reaching peak torque (110-170º) compared to the shortest ones. In conclusion, contrary to the lore, a longer crank requires a higher mechanical effort compared to a shorter crank for pedalling at the same intensity
Change in shock attenuation during marathon running
Get PDFThe purpose of this study was to estimate shock attenuation during marathon running using inertial measurement units attached on the foot and sacrum. Eleven male runners were recruited as subjects from the participants of the official marathon race. Two inertial measurement units (IMUs) attached on the foot and sacrum operated at 200 Hz and stored three axis acceleration data in the memory through the marathon race. Absolute acceleration was transferred power spectrum density (PSD) by FFT and a transfer function was calculated by PSD of the sacrum relative to the foot. The results showed that the impact acceleration was recognized from 11 to 18 Hz at the foot and was attenuated between the foot and the sacrum. It is suggested that this method could be useful to evaluate shock attenuation during endurance running easily and might be used to give appropriate feedback in real time to decrease injury risk
THE EFFECT OF VISUAL GAZE LOCATION ON BLOCK-START BIOMECHANICS IN ATHLETICS
Get PDFThis study investigated the effects of varying visual gaze location (VGL), by means of externally-focused instruction, during the block-start “set” phase with the intention of optimizing block-start biomechanics for faster starts in an athlete-specific manner. Nine collegiate sprinters performed a series of block-starts while directing their VGL to their personal baselines, and at 0.5m, 1m, 2m and 3m from the start line. Twelve infrared opto-reflective cameras and one force plate were utilized to assess trunk, hip, knee and centre of mass kinematics, and blocks push-phase kinetics. An eyetracker was used to determine participants’ VGL. Some postural changes observed were a significant decrease in pelvic height in the “set” position, and more upright trunk postures at toe-off from the blocks, when participants gazed further at 2m and 3m. Gazing at 1m was effective in eliciting changes to pelvic horizontal velocity. These results suggest that manipulating VGL could help certain athletes to optimize their block-start biomechanics for faster starts. Coaches can consider redirecting VGL in addition to usual instructional methods to improve the block-start performances of athletes
THE LOCAL BIOMECHANICAL ANALYSIS OF LOWER LIMB ON COUNTER-MOVEMENT JUMP BETWEEN BAREFOOT AND SHOD PEOPLE WITH DIFFERENT FOOT MORPHOLOGY
Get PDFThe aim of this study was to explore the kinematic variations in knee and ankle joints and the ground reaction force between habitually barefoot (HBM) and shod males (HSM) during countermovement jump. Twenty-eight males (14 HBM,14 HSM) participated in this experiment. An 8-camera Vicon motion system was used to collect the kinematic data of knee and ankle joints from 3 dimensions and the force plate was used to collect the ground reaction force in take-off phase. Results in take-off phase showed that HSM produced two peak forces to take off and showed significantly greater knee ROM in sagittal plane, as well as greater ankle inversion and external rotation. In conclusion, the foot morphological differences can result in the different influence on jump performance. The relevant practioner should pay close attention to the effect of foot morphology on jump in training
JOINT ANGLES AND FORCES ON WRIST STRUCTURES DURING VARIATIONS OF YOGA POSES
Get PDFThe current study analysed joint angles of the wrists and forces on the structures in the hands and wrists in a hyperextended position and a neutral position during three different yoga poses. Participants (n = 9) performed three yoga poses (plank, side plank, and upward dog), with their wrists in a hyperextended position (H) and a neutral position (N). Each pose was completed three times for 10 seconds in H and N, for a total of six trials per pose. A two-way Repeated Measures ANOVA found significant differences in both wrist joint angles and GRF between H and N. Due to the suggested path transmission of forces, as well as the increased longitudinal loading that comes with wrist hyperextension, it is recommended that plank, side plank, and upward dog be performed in a neutral wrist position
HOW DOES WHOLE BODY BALANCE CONTROL INTERACT WITH STROKE PERFORMANCE DURING THE TENNIS SERVE?
Get PDFThe purpose of this study was to investigate whether there is an interaction between mechanisms used to control whole body balance and racket performance. Fourteen experienced tennis players (nine males and five females; age, 21.5±3.9 yr; height, 1.7± 0.1 m; body mass 65.8± 8.1 kg) completed 10 successful tennis serves. Twelve optoelectronic cameras were used to collect kinematic data at 200 Hz (BTS bioengineering, Milan, Italy). Linear regression using 1D Statistical Parametric Mapping was used to identify interactions between the extrapolated centre of mass (XCoM) displacement in the anteroposterior direction and the changes in arms/trunk segment angular momentum, and peak anterior-posterior racket velocity. Overall, no meaningful relationships were found, except for a small time interval during the forward swing phase in which a greater increase in trunk angular momentum was associated with increased maximum racket velocity
COMPARISON OF FOOT MORPHOLOGY AND PREFERRED SHOE FOR IMPROVING RUNNING SHOE FITTING
Get PDFThe purpose of this study was to compare the shoe internal space and foot shapes of different type for increasing sense of shoe fitting. 347 healthy subjects (male=160; female=187) without any pathological conditions of the foot participated in this study. 11 pairs of running shoes have different size (230-280mm) with same material and appearances were prepared and the shapes of shoe last were also measured for these shoes. In order evaluating the sense of shoe fitting, 6 fit indicators were analysed by comparing the shape of shoe last with foot morphology. We could find that people with wider feet tend to wear tighter shoes and narrower feet preferred to wear looser shoes that seems to significantly affect by the experience. And the sense of shoe fitting was significant different from gender and foot type which can be used as important data for recommending shoe size and to make customized shoe
CHOICE OF DATA PROCESSING INFLUENCES PRACTICAL INTERPRETATION OF KICK LEG JOINT KINETICS DURING THE IMPACT PHASE OF BALL KICKING
Get PDFThe aim of this study was to compare different methods processing kick leg joint moments during the ball impact phase of football instep kicking. Kicking motions and GRFs from eighteen semi-professional footballers were captured by three-dimensional motion analysis (1000Hz) and joint moments were derived using four conventional, and two advanced (time-frequency filter) methods. Ankle, knee and hip moments at ball contact were all different between processing method (P \u3c 0.017), with large pairwise effect sizes (d \u3e 0.8). Choice of data processing influences practical interpretation of ball kicking motions. Filtering ‘through’ the impact phase introduces considerable error, so truncating and extrapolating joint moments before contact should be performed. Use of these methods highlight the importance of: a) training the ankle dorsiflexors for resisting forced plantarflexion upon ball contact, b) developing coaching cues that co-ordinate whole-body action to complement passive knee extension in the final stage of the downswing and c) tailoring training/ coaching of kicking skills to an individual’s preferred movement strategy
USING WEARABLE TECHNOLOGY TO DETECT CHANGES TO TRUNK POSITION AND POWER IN CYCLING
Get PDFThis pilot study aimed to quantify the change of CoM acceleration when the trunk position and the power output was varied during indoor cycling. Triathletes (n=4) performed a varied indoor cycling power protocol in their natural training environment whilst wearing a trunk (sacrum) mounted wearable device containing a triaxial accelerometer. Mediolateral acceleration increased 26% as athletes moved from the drops position, to the aerodynamic position and back to the drops position. Although longitudinal acceleration increased 8%, minimal differences in anteroposterior CoM magnitude were observed. Power output was found to have an effect on both the mediolateral and longitudinal acceleration alongside increases in RPE. The results indicate that accelerometers may be effective in monitoring changes to trunk position and power output