SYNCHRONIZATION OF SPRINTING BETWEEN BLIND AND GUIDE SPRINTERS: A CASE STUDY

This study aimed to evaluate the magnitude of synchronization between blind and guide sprinters for elite and sub-elite pairs. Two pairs of male blind sprinters and their guide sprinters performed 60-m sprints during which ground reaction force and sprinting motion were recorded. Although flight time and propulsive force in sub-elite pair showed significant and moderate difference between the sprinters, there were trivial and small differences in variables between the sprinters of elite pair. Moreover, the correlation (r = 0.97 and 0.84) in the thigh angle in the sagittal plane between blind and guide sprinters was high with no phase shifting for the elite pair compared to the sub-elite pair during the initial acceleration phase. The results indicate that the magnitude of synchronization is likely high in an elite pair of blind and guide sprinter especially during the initial acceleration phase

KINETICS OF SINGLE SESSION INTRA-INDIVIDUAL DIFFERENCE IN SPRINT ACCELERATION: A CASE STUDY

This case study aimed to investigate inter-repetition differences in joint kinetics for a single athlete during the acceleration phase of sprinting. One well-trained male sprinter performed three maximal effort 40-m sprints in an indoor experimental site. Using the fastest and slowest trials, spatiotemporal, ground reaction forces, and joint moment variables were calculated step to step for 16 steps. The fastest trial was accompanied by the greater mean net anteroposterior force. Moreover, there were greater hip extension and ankle plantar flexion moments, as well as a smaller knee extension moment, in the fastest trial. Accordingly, producing greater hip extension and ankle plantar flexion moments while suppressing the knee extension moment leads to better sprint acceleration through the greater propulsive force in the initial acceleration section

STEP-TO-STEP SPATIOTEMPORAL DETERMINANTS OF FEMALE SPRINT PERFORMANCE DURING THE ENTIRE ACCELERATION PHASE

The purpose of this study was to clarify the kinematic determinants of maximal effort female sprint performance during the entire acceleration phase of a single sprint. Fifteen sub-elite female sprinters completed a 60 m maximal effort sprint from starting blocks over a long force platform system. Ground reaction force data was used to calculate step length, step frequency, support time and flight time. Pearson’s product moment correlation coefficient was used to clarify the association between the rate of changes in these spatiotemporal variables and acceleration at every step. Peformance determinants elucidated included the rate of changes in step length (1st to 10th steps), step frequency (2nd to 7th steps), support time (1st to 5th steps) and flight time (4th to 7th steps). Results were considered similar to past research on male sprinters, although showed slightly different correlations

DIFFERENCES BETWEEN CONTROL AND SUPPRESSED ARM SPRINT RUNNING DURING THE MAXIMUM VELOCITY PHASE

The purpose of this study was to clarify sprint characteristic differences between control and suppressed arm sprint running during the maximum velocity phase. Baseball players (n=15) completed a 50 m control and suppressed arm trial, and ground reaction force was measured with force platforms. Sprint characteristics were calculated during the stride that maximum velocity was reached. Cohen’s d effect size with 95% confidence intervals and paired T-tests elucidated differences between trials. The maximum velocity decreased by 7.06% during the suppressed arm trial, compared to the control, probably caused by the suppressed arm condition. There were further decreases in propulsive (12.67%), braking (7.40%), vertical (2.81%) and effective vertical (5.95%) mean forces, suggesting significant ground reaction force differences between trials during the maximum velocity phase

DYNAMIC CONTRIBUTIONS OF SUPPORT LEG JOINT TORQUES TO THE GENERATION OF THE IPSILATERAL KNEE JOINT MOTION AND GROUND REACTION FORCE IN SPRINTING

This study aimed 1) to quantify the contributions of the support leg joint torques to the generation of the anteroposterior forces, and 2) to clarify major contributors to the support leg knee joint angular velocity in terms of generating factors of the motion-dependent term (MDT) in sprinting. Dynamic contributions of the support leg joint torques in the maximal speed sprinting for elite and sub-elite sprinters were calculated, and the generating factors of the MDT were quantified The results showed that 1) ankle plantar flexion torque is the largest contributor to the generation of propulsive force regardless of performance level, and 2) the major contributors to the support knee flexion for sub-elite sprinter were ankle plantar flexion and hip flexion torques

Kinetic factors differentiating mid-to-late sprint acceleration performance in sprinters and soccer players

High-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

GROUND REACTION FORCE OF THE FIRST TRANSITION DURING ACCELERATED SPRINTING: A PILOT STUDY

This study aimed to show changes in step-to-step ground reaction forces around the first transition during maximal accelerated sprinting with a typical sprinter. One male sprinter performed five 60-m maximal accelerated sprints, during which ground reaction forces through 50 m were recorded with 54 force platforms. There were sudden shifts of values for step frequency, support time, vertical impulse and braking and propulsive mean forces at around the 5th step as the first sprint transition. These sudden shift of variables support the concept of sprint transition during acceleration phase. The findings of this study would be interesting for the future study of locomotor control and practically useful for considering the strategy of accelerated sprinting

EVALUATION OF SPEED CHANGE IN 100 M SPRINT RUNNING

The purpose of this study was to propose a method to evaluate speed in 100m running with modified exponential equations. The speed changes in 100m sprint race of ninetysix sprinters (62 men and 34 women) were measured with a LAVEG system. The 100m race was divided into the acceleration and deceleration phases based on the maximum speed, and speed were estimated. 1) The exponential equations proposed in this study well estimated the speed change pattern of the 100m on the different record groups. The average errors between the official time and the time estimated were 0.024±0.040s in men and 0.04±0.039 in women. 2) The maximum speed was the most important factor for both men and women sprinters to achieve best performance the race. 3) The men world class sprinters accelerated quickly (large k), but reached the maximum speed later than the other sprinters, which resulted in shorter deceleration phase and smaller decreases in speed after reaching the maximum speed

THE EFFECT OF LOWER LIMB WEARABLE RESISTANCE LOCATION ON SPRINT RUNNING STEP KINEMATICS

This study quantified changes in step kinematics between unloaded, thigh, and shank wearable resistance (WR) at 2% body mass (BM) during over ground sprint running. Eleven male athletes completed two maximal effort sprint trials over 52 m of in-ground force plates, for each condition. There were no significant (p \u3e 0.05) changes in sprint times between all conditions. Compared to unloaded sprinting, shank WR significantly changed step frequency (SF) (-2.1% acceleration phase and -2.5% max velocity phase (MVP)), contact times (CT) (2.1% MVP) and flight times (3.3% MVP); thigh WR significantly changed SF (-1.4% MVP) and CT (2.9% MVP). It appears peripheral loading (2% BM) of the thigh and shank affects SF and CT but not step length and width. Such differential loading could be used to train different mechanical determinants of speed

KINEMATICS OF THORAX AND PELVIS DURING MAXIMAL ACCELERATED SPRINTING

Changes in thorax and pelvis movements during acceleration phase of maximal sprinting, which relate to acceleration ability, are still unknown. This study aimed to clarify the changes in thorax and pelvis movements during maximal accelerated sprinting and its relation to better acceleration ability. Twelve sprinters performed a 60-m sprint, during which 3D kinematics of the sprinters were obtained. The same patterns of motions were maintained for thorax and pelvis respectively throughout the entire acceleration phase, although phase profiles of relative movements between thorax and pelvis in three planes differed. Moreover, results indicated that effective acceleration is characterised by suppressed trunk bend, delayed trunk rotation, and forward tilted pelvis in the middle acceleration section and suppressed trunk bend in the final acceleration section