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SUPERPOSITION PRINCIPLE APPLIED TO THE OPTIMIZATION OF KICK-TO-STROKE RATIO OF BACKSTROKE
Get PDFBackstrokers acknowledge there is an apparent rhythm in swimming that is characterised by the periodic motion of the arms and legs, which must be optimally sychnronized for effective performance. However, unlike the freestyle crawl where the optimal kick-stroke ratio is established at 3:1, there is a limited understanding of the optimal ratio for backstrokers. By separating the velocity contributions of the kick and stroke, the superposition principle can be utilised to find the optimal kick-stroke ratio to maximize swimming distance, the area below the superimposed velocity curve. This paper intends to mathematically establish this ratio and thus improve the performance of backstrokers
THE IMPACT OF THERAPEUTIC ANKLE TAPING ON THE KINEMATICS OF THE LOWER EXTREMITY WHILE RUNNING
Get PDFOverpronation is a misalignment of the calcaneus resulting from flattening of the medial longitudinal arch, which may lead to an overuse injury in runners. It is suggested that taping may control the position of the calcaneus to correct foot pathologies associated with overpronation. This pilot study explored the effect of ankle taping on the kinematics of the lower extremity while running. Fifteen healthy participants ran on a treadmill with a Kinesio Tape®, Leuko Tape®, and a no tape condition while being video recorded for 3D analysis. No significant changes in the selected lower extremity kinematic variables were seen among the tape and no tape conditions. Participants demonstrated an average Foot Posture Index score of 2.2±1.5, which is considered neutral. Ankle taping may be more beneficial in altering lower extremity kinematics in runners with higher values of pronation and at faster running speeds
AERODYNAMIC EFFECTS OF A PANEL ORIENTATION IN VOLLEYBALL FLOAT SERVE
Get PDFThe purpose of this study was to clarify the aerodynamic and trajectory characteristics on four type volleyballs using the wind tunnel experiments and a hitting robot. We confirmed, in particular, that the critical Reynolds number (Recr) changed depending on the ball types and panel orientations. Recr for Mizuno ball (conventional) was determined to be ~2.8 × 105 (Drag coefficient; Cd = 0.16) on panel orientation A and ∼2.0 × 105 (Cd = 0.20) on panel orientation B. On the other hand, Recr for Mikasa ball (Olympic Official) was ∼2.9 × 105 (Cd = 0.16) in the panel orientation A and ∼3.3 × 105 (Cd = 0.15) in panel orientation B. Moreover, we found that the landing position of all volleyballs varied depending on the ball type and the orientation of the panel. In particular, Molten ball has a longer flight distance than other balls and its landing point was biased toward the left side. On the other hand, Mikasa ball had a relatively short flight trajectory and its landing point was biased to the right. Therefore, it can be hypothesized that during a float serve, the flight trajectory will change depending on the type of volleyball and their orientation
EFFECTS OF RUNNING BIOMECHANICS ON THE OCCURRENCE OF ILIOTIBIAL SYNDROME IN MALE RUNNERS — A PROSPECTIVE STUDY
Get PDFThis study aimed to determine the gait characteristics that easily induce ITBS and explore the gait changes after the occurrence of ITBS. 30 healthy male runners participated in our study, 15 in ITBS and control group respectively. All participants underwent two gait trials, namely, before the first day of their routine running and after 8 weeks. After 8 weeks of running, the ITBS group exhibited greater peak anterior pelvic tilt and hip flexion angle than the control group. The ITBS group showed increased peak trunk inclination angle, whereas the control group demonstrated lower peak hip flexion and peak hip adduction than those at the beginning of running. Decreased peak hip flexion and peak hip adduction angle was a gait adjustment strategy that could be used to avoid ITBS occurrence. Excessive trunk posture and pelvic activity during running are also ITBS risk factors
ADDUCTOR MUSCLE STRESS AND HIP JOINT LOAD IN 90° CUTTING MANOEUVRES AND THEIR POSSIBLE LINK TO GROIN INJURIES
No full textEpidemiological studies on groin injuries in soccer have often linked them to kicking and cutting manoeuvres (CM) although no biomechanical studies exist that prove this link for CMs. The present study investigated the hip joint kinematics and kinetics of a 90° CM. Thirteen participants were investigated with a 3D movement analysis system and a force platform. Results showed hip joint angles to be slightly higher than in previous studies on smaller CM angles. Hip moments in the frontal and transverse plane were similar to those of inside passing while the muscle stress in gracilis and adductor longus were 43 % and 44 % lower compared to passing. Therefore, CMs might not put the groin region under a dangerous load, allowing for a shift of focus in injury prevention to kicking and passing movements
EXAMINING THE RELIABILITY AND VALIDITY OF THE FITBIT® CHARGE 2™ ON STEP COUNT DURING TREADMILL EXERCISE
No full textThe purpose of this study was to determine the reliability and validity of the Fitbit® Charge 2™ to count steps during a treadmill protocol. The participants wore a Fitbit® Charge 2™ on their wrist. 16 participants who met inclusion criteria were assigned to the following testing conditions; GPS stride length/manual stride length and hold/no-hold onto the handrails of the treadmill. The participants completed a walking protocol that included light (60% of HRR) intensities. The Fitbit® Charge 2™ step count and the manually counted steps were documented. Intraclass Correlation Coefficients (ICC) analysis found that the Fitbit® Charge 2™ was not reliable or valid to count steps
KINETIC FACTORS DIFFERENTIATING MID-TO-LATE SPRINT ACCELERATION PERFORMANCE IN SPRINTERS AND SOCCER PLAYERS
Get PDFHigh-speed running in soccer is an important skill, however, the underlying kinetic factors are not fully understood. Ground reaction forces from steps 8 to 24 of maximal-effort sprints were captured for 24 soccer players and 28 track and field athletes using 54 force plates. Correlations between discrete force variables and horizontal acceleration were assessed, and statistical parametric mapping revealed performance associations across entire waveforms. Track and field athletes produced higher forces (mean anteroposterior: 1.56 N·kg-1) across shorter contacts (0.101 s) than soccer players (1.27 N·kg-1, 0.110 s). Interestingly, the technical ability to apply force and the performance-differentiating parts of stance were similar across groups. Thus, practitioners should perhaps target physical (force production) rather than technical factors to improve soccer players’ sprint abilities
TRACKING OF STRENGTH TRAINING: VALIDATION OF A MOTION-RECOGNITION ALGORITHM & A PILOT TOWARDS 1RM, MUSCLE LOADING AND FATIGUE INDEX USING A SMARTWATCH APP
Get PDFUbiquitous wrist-worn devices have become a noteworthy research topic in motion recognition of strength training exercises. This study was designed to develop a watchOS and iOS application and assess its exercise recognition and repetition counting accuracy. Furthermore, as a pilot, a method to estimate the 1 repetition maximum and muscle stress and fatigue is explored. To test the exercise recognition and repetition counting accuracy, a workout consisting of nine sets with five randomly ordered resistance training exercises and repetition amounts was conducted when wearing an Apple Watch. Overall mean %error in exercise recognition was 3.5% and 0.92% in repetition counting. In the future, this app can also be used for estimation of 1 repetition maximum, muscle stress and fatigue
FORCE AND POWER OUTPUTS OF TRUNK-TWIST DURING BAR TWIST EXERCISE -INFLUENCE OF LENGTH AND MASS OF BARS-
Get PDFThe purpose of this study was to investigate force and power outputs during bar twist exercises using barbell shafts, considering various moment of inertia (MOI), corresponding to changes in the bar length and mass. Twenty-one male college athletes performed the bar twist exercise using five barbell shafts: one normal barbell shaft, two long barbell shafts (with changes only in the length), and two heavy barbell shafts (with changes only in the mass). Kinematic and kinetic data were recorded using the Vicon system (250 Hz) and two force platforms (1,000 Hz). The results obtained in this study revealed that: (1) Peak angular velocity of bar and upper trunk for the long barbell shaft condition was higher than the heavy barbell shaft condition; (2) For higher MOI, the trunk-twist torque was higher; and (3) Even when the barbell shaft had equal MOI, the heavy bar showed higher trunk-twist torque prior to the bar rotation
ANALYZING VERTICAL JUMP AND STANDING LONG JUMP POWER RATIOS TO DETERMINE LOWER EXTREMITY INJURY RISK USING AUROC CURVES
Get PDFThe purpose of this study examined the ability to predict previous knee and thigh injuries in athletes by assessing allometrically scaled ratios of average power and peak power results from VJ (vertical jump) and SLJ (standing long jump) testing using ROC curves. The strength and conditioning testing data and medical records of 26 female NCAA-I from soccer and volleyball teams were examined. Data examined included isokinetic knee flexion and extension, VJ power, and SLJ power outputs. Previous thigh or knee injury was compared to scaled average power ratio, peak power ratio, and calculated z-scores for average power ratio and peak power ratio. The use of AUROC to assess power output from the performance tests of the VJ and the SLJ to determine injury risk poorly predicts the possibility of a previous knee or a thigh injury