Coop DeRenne

Effects of preload 4 repetition maximum on 100-m sprint times in collegiate women.

Linder, EE, Prins, JH, Murata, NM, Derenne, C, Morgan, CF, and Solomon, JR. Effects of preload 4 repetition maximum on 100-m sprint times in collegiate women. J Strength Cond Res 24(5): 1184-1190, 2010-The purpose of this study was to determine the effects of postactivation potentiation (PAP) on track-sprint performance after a preload set of 4 repetition maximum (4RM) parallel back half-squat exercises in collegiate women. All subjects (n = 12) participated in 2 testing sessions over a 3-week period. During the first testing session, subjects performed the Controlled protocol consisting of a 4-minute standardized warm-up, followed by a 4-minute active rest, a 100-m track sprint, a second 4-minute active rest, finalized with a second 100-m sprint. The second testing session, the Treatment protocol, consisted of a 4-minute standardized warm-up, followed by 4-minute active rest, sprint, a second 4-minute active rest, a warm-up of 4RM parallel back half-squat, a third 9-minute active rest, finalized with a second sprint. The results indicated that there was a significant improvement of 0.19 seconds (p < 0.05), when the second sprint was preceded by a 4RM back-squat protocol during Treatment. The standardized effect size, d, was 0.82, indicating a large effect size. Additionally, the results indicated that it would be expected that mean sprint times would increase 0.04-0.34 seconds (p < 0.05), when using a preload 4RM squat protocol. There were no significant differences between Control pre and posttests (p > 0.05). The findings suggest that performing a 4RM parallel back half-squat warm-up before a track sprint will have a positive PAP affect on decreased track-sprint times. Track coaches, looking for the “competitive edge” (PAP effect) may re-warm up their sprinters during meets.

Contributing factors for increased bat swing velocity.

Bat swing velocity is an important characteristic of successful hitters in baseball and softball. The purpose of this literature review is threefold. First, before describing what components and training methods have been investigated to improve bat swing velocity, it is necessary to discuss the importance of bat swing velocity and batted-ball velocity. The second purpose is to discuss bat weight during on-deck circle warm-up, bat weight during resistance training, resistance training with an overload of force, performance of additional supplemental resistance exercises, the relationship between strength, power, lean body mass, and angular velocity and bat swing velocity, and the relationship between improvements in strength, power, lean body mass, and angular velocity and improvements in bat swing velocity. The third purpose of this review is to recommend some practical applications based on research results.

Effect of various warm-up devices on bat velocity of intercollegiate baseball players.

Szymanski, DJ, Beiser, EJ, Bassett, KE, Till, ME, Medlin, GL, Beam, JR, and DeRenne, C. Effect of various warm-up devices on bat velocity of intercollegiate baseball players. J Strength Cond Res 25(2): 287-292, 2011-A variety of warm-up devices are available to baseball players to use before their game at-bat. Past baseball research evaluating warm-up devices indicates that implements that are ±12% of standard game bat weight produce the greatest bat velocities for high school and intercollegiate players. The purpose of this study was to examine the effect of various warm-up devices on bat velocity (BV) of intercollegiate baseball players. Twenty-two Division I intercollegiate baseball players (age = 20.0 ± 1.5 years, height = 182.6 ± 8.3 cm, body mass = 91.4 ± 11.4 kg, lean body mass = 78.8 ± 8.9 kg, % body fat = 13.6 ± 3.8) participated in a warm-up with 1 of 10 weighted devices on separate days. Each of the 10 testing sessions consisted of a standardized warm-up, 3 dry swings as hard as possible with the assigned warm-up device, 2 comfortable dry swings with a standard game baseball bat followed by 3 game swings (20-second rest between swings) while hitting a baseball off of a batting tee with the same standard game baseball bat. Results indicated that there were no statistically significant differences in BV after using any of the 10 warm-up devices. For male intercollegiate baseball players, results indicate that warm-up devices varying from 623.7 to 2,721.5 g (22-96 oz.) did not change mean BV of a standard game baseball bat, suggesting that intercollegiate players can use any of the 10 warm-up devices in the on-deck circle and maintain their BV. Therefore, personal preference as to which warm-up implement to use in the on-deck circle is advised.

The relation between anthropometric and physiological variables and bat velocity of high-school baseball players before and after 12 weeks of training.

Szymanski, DJ, Szymanski, JM, Schade, RL, Bradford, TJ, McIntyre, JS, DeRenne, C, and Madsen, NH. The relation between anthropometric and physiological variables and bat velocity of high school baseball players before and after 12 weeks of training. J Strength Cond Res 24(11): 2933-2943, 2010-The purpose of this article was to investigate the relation between anthropometric and physiological variables to linear bat swing velocity (BV) of 2 groups of high-school baseball players before and after completing a 12-week periodized resistance exercise program. Participants were randomly assigned to 1 of 2 training groups using a stratified sampling technique. Group 1 (n = 24) and group 2 (n = 25) both performed a stepwise periodized resistance exercise program and took 100 swings a day, 3 d·wk−1, for 12 weeks with their normal game bat. Group 2 performed additional rotational and full-body medicine ball exercises 3 d·wk−1 for 12 weeks. Fourteen variables were measured or calculated before and after 12 weeks of training. Anthropometric and physiological variables tested were height, body mass, percent body fat, lean body mass (LBM), dominant torso rotational strength (DTRS) and nondominant torso rotational strength (NDTRS), sequential hip-torso-arm rotational strength measured by a medicine ball hitters throw (MBHT), estimated 1 repetition maximum parallel squat (PS) and bench press (BP), vertical jump (VJ), estimated peak power, angular hip velocity (AHV), and angular shoulder velocity (ASV). The baseball-specific skill of linear BV was also measured. Statistical analysis indicated a significant moderately high positive relationship (p ≤ 0.05) between prelinear BV and pre-NDTRS for group 1, pre-LBM, DTRS, NDTRS, peak power, and ASV for group 2; moderate positive relationship between prelinear BV and preheight, LBM, DTRS, peak power, BP, PS, and ASV for group 1, preheight, body mass, MBHT, BP, and PS for group 2. Significantly high positive relationships were indicated between postlinear BV and post-NDTRS for group 1, post-DTRS and NDTRS for group 2; moderately high positive relationships between postlinear BV and post-LBM, DTRS, peak power, BP, and PS for group 1, postheight, LBM, VJ, peak power for group 2; moderate positive relationships between postlinear BV and postheight, body mass, MBHT, and VJ for group 1, postbody mass, MBHT, BP, PS, and ASV for group 2. Significantly low positive relationships were indicated between prelinear BV and prebody mass, MBHT, and VJ for group 1, pre-VJ and AHV for group 2; postlinear BV and post-AHV for group 2. These data show that significant relationships do exist between height, body mass, LBM, rotational power, rotational strength, lower body power, upper and lower body strength, AHV, and ASV to linear BV of high-school baseball players. Strength coaches may want to consider using this information when designing a resistance training program for high-school baseball players. Those recruiting or scouting baseball players may want to use this information to further develop ways of identifying talented players. However, one should be cautious when interpreting this information when designing strength training programs for high-school baseball players to increase linear BV.

Afterschool physical activity program to reduce obesity-related cancer risk: a feasibility study.

Background. Cancer is linked to obesity, and Native Hawaiian childhood obesity rates are high. We examined the feasibility of incorporating a physical activity intervention into an afterschool program for elementary school children. Methods. Anthropometric and fitness measures were taken at baseline and 12 weeks later for 68 students in 2 schools. In one, the supervisor delivered a model curriculum. In the other, a supervisor with physical education training created the curriculum. Results. We found a significant decrease in skinfold thicknesses and increase in distance covered in the 3-minute walk-run test. Conclusions. Incorporating daily physical activity into afterschool programs is feasible and effective, but teacher interest is critical, and the nonmandatory nature of this venue may limit children’s participation.