SPATIAL, TEMPORAL, AND KINETIC VARIABLES DURING THE EARLY ACCELERATION PHASE OF SPRINTING

This 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

SEX-BASED ANALYSIS OF SPRINT ACCELERATION

This study assessed a variety of kinetic, spatial, and temporal variables during the early acceleration phase of sprinting for both men and women (N = 20) during standing and sprinter position starts. Forces, step distance, time, and velocity measured from the first four steps of each start via force platforms were compared across start, step, and sex via ANCOVA while removing the effect of height or weight. Velocity increased from step 1 to steps 2 and 3; while overall velocity was lower for women and the standing start (p \u3c 0.05). There were interactions of start * sex for horizontal force, ratio of horizontal to vertical force, overall velocity, and overall time (p \u3c 0.05). Men’s performance tended to be more negatively affected when using the standing start than women’s performance

BIOMECHANICAL ANALYSIS OF THE FASTBALL THROWN FROM THE WIND-UP AND THE STRETCH

This study assessed the biomechanics associated with the fastball thrown in two conditions. Fifteen men pitched from the wind-up and stretch beginning and landing on force platforms. Doppler radar was used to assess ball velocity. A paired samples t-test was used to determine differences in ball velocity, propulsive and landing phase kinetics, as well as time, distance, and subject velocity from the propulsive to landing phase. The stretch produced 5.55% more horizontal ground reaction force, a higher horizontal to vertical force ratio, 35.05% greater vertical rate of force development (RFD) in the propulsive phase, and 8.85% higher horizontal and 24.65% vertical RFD upon landing (p ≤ 0.05). The wind-up produced 39.49% greater horizontal RFD in the propulsive phase (p ≤ 0.05). These variations of the fastball use different mechanisms to achieve similar (p = 0.77) ball velocities

KINETIC, SPATIAL, AND TEMPORAL ASSESSENT OF OVERSPEED TOWING WITH ELASTIC TUBING

Subjects (N = 15) performed sprints over force platforms in a normal condition and in three overspeed conditions of differing elastic tube stretch length. Kinetic and kinematic data were derived. A 3 x 4 RM ANOVA was used to analyze the results. The horizontal and vertical ground reaction force (GRF), and the ratio of horizontal to vertical GRF did not differ among conditions (p ˃ 0.05). However, ground contact time was 8.3% to 10.4% shorter, time between steps was 1.4% to 2.7% lower, distance between steps was up to 1.2% greater, and velocity was 3.7% higher in some overspeed towing conditions compared to the normal condition (p ≤ 0.05). Longer tube conditions were more optimal in most cases. Compared to normal running, overspeed towing results in increased sprinting velocity despite no differences in horizontal or vertical kinetics compared to normal running

BIOMECHANICAL ANALYSIS OF TIRE FLIPPING WITH TIRES OF DIFFERENT MASSES AND THEIR POTENTIAL SPECIFICITY TO SPRINTING

This study compared the kinetics of tire flipping with different mass tires and sprinting to evaluate the potential specificity of this training stimulus. Subjects (N=15) performed tire flips with a 54.3 kg tire, a 102.1 kg tire, and sprinted on two large force platforms. Dependent variables included peak horizontal ground reaction force (HGRF), peak vertical GRF (VGRF), horizontal to vertical GRF ratio (H:V), and rate of vertical GRF development (VRFD). A RM ANOVA was used to analyze the data. Significant main effects were found for all dependent variables (p ≤ 0.03). Post-hoc analysis showed that the tires were different (p ≤ 0.04) for all dependent variables except for VRFD (p = 0.99). Post-hoc analysis showed that the 54.3 kg tire was more similar to the kinetics of sprinting for HGRF, VGRF, and H:V. Only tire flipping with a lighter tire was similar to key kinetic parameters of sprinting

SEX-BASED ANALYSIS OF THE BIOMECHANICS OF PITCHING

This study assessed sex-based differences in the lower extremity kinetics and ball velocity during pitching. Fifteen men baseball players and fifteen women softball players threw fastballs on two force platforms, to assess propulsive and landing biomechanics. Doppler radar was used to assess ball velocity. Kinetic and kinematic data comparing men and women were analyzed with independent samples t-test. Paired samples t-test were used to assess difference between the propulsive and landing phases. Pearson’s bivariate correlations were used to assess the relationship between study variables and ball velocity. Few sex-based difference in the magnitude and rate of propulsive force development exist. Sex based differences (p \u3c 0.05) were found for all but one landing phase variable. None of the biomechanical variables assessed were related to ball velocity

KINEMATIC AND KINETIC ANALYSIS OF THE HORIZONTAL HANG CLEAN PERFORMED WITH A VARIETY OF LOADS AND THEIR COMPARISON TO THE SPRINT START

This study evaluated kinetic and kinematic aspects of the horizontal hang clean (H-HC) at a variety of loads and also compares these results to the standing sprint start (SSS). Subjects were tested during the H-HC at 30%, 50% and 70% of their five-repetition maximum (5RM), and during the SSS, using two force platforms. Analysis revealed significant differences for the H-HC conditions for the propulsive phase vertical GRF (p ≤ 0.001), propulsive phase horizontal to vertical GRF ratio (H:V) (p = 0.001), subject/barbell displacement (p ≤ 0.001), and velocity (p ≤ 0.001). The propulsive H:V of the H-HC at 30% of the 5 RM was correlated to the propulsive H:V of the first step of the SSS (p = 0.04, r = 0.55). To maximize subject anterior displacement and velocity and propulsive H:V, practitioners should use the H-HC with loads of 30% of the 5 RM. Training in this manner offers specificity for sprinting starts

THE ROLE OF SHOE SOLE DUROMETER ON JUMPING KINETICS

This study investigated the relationship between shoe heel density (HD), toe density (TD) and the peak ground reaction force (GRF) and rate of force development (RFD) during jumping. This study also assessed the reliability of the durometer to assess shoe soles. Subjects included 12 men. Shoe HD and TD were assessed via durometer and kinetics were determined during the countermovement jump on a force platform. A Pearson bivariate correlation analysis was performed. Results reveal that HD was not correlated with GRF (r = -.22, p = .50) or RFD (r = -.14, p = .67). Similarly, TD was not correlated with GRF (r = -.29, p = .37) or RFD (r = -.28, p = .37). Intraclass correlation coefficients for the heel and toe durometer were .95 and .92, respectively. Jumping kinetics were not mediated by shoe sole characteristics, though the durometer was reliable for assessing shoe soles

BIOMECHANICAL ANALYSIS OF LOADED PLYOMETRIC EXERCISES

Plyometric intensity and specificity are determined by the exercises performed. This study assessed ground reaction forces (GRF) in the frontal (F), horizontal-anterior (H), and vertical (V) planes, and the ratio of H to V GRF (H:V) of plyometric exercises and load conditions. Subjects (N=15) performed five plyometric variations with five handheld loads on two force platforms. A two-way RM ANOVA was used. Analysis of F GRF revealed main effects for plyometric exercise (p = 0.004). Analysis of H GRF revealed main effects for plyometric load (p = .042) and plyometric exercise (p ≤ 0.001). Analysis of V GRF revealed main effects for plyometric load (p ≤ 0.001) and plyometric exercise (p ≤ 0.001). Analysis of H:V revealed main effects for plyometric exercise (p ≤ 0.001). Practitioners should use the plyometric exercises and loads that optimize the kinetics and transfer of training

KINETIC ANALYSIS OF AGILITY LADDERS DRILLS AND THEIR COMPARISON TO SPORT-SPECIFIC MOVEMENTS SUCH AS SHUFFLING AND SPRINTING

This study assessed agility ladder drills for the purpose of comparing kinetic characteristics of these drills to one another, and to sprinting and shuffling. Subjects (N=30) performed six agility ladder drills as well as sprinted and shuffled to the left and right over two large force platforms. A repeated measure ANOVA was used to assess horizontal and vertical ground reaction force (GRF) and the ratio of horizontal to vertical GRF, averaged from three steps for each drill. Significant main effects were found for all variables (p ≤ 0.001). Post-hoc analysis identified differences (p ≤ 0.05) between the agility drills as well as between the agility drills and the sprinting and shuffling. Results can be used to guide the progression of agility ladder drills based on known intensity and allow practitioners to prioritize drills that are most similar to sport-specific movements such as sprinting and shuffling