THE EFFECT OF WHOLE BODY VIBRATION ON THE DYNAMIC STABILITY OF WOMEN BASKETBALL PLAYERS

This study investigated the effect whole body vibration (WBV) on the dynamic stability of NCAA Division I women basketball players. Eleven subjects were evaluated in two test conditions including one with and one without WBV. After each condition, subjects were tested for time to stabilization (TTS) on a force platform during bilateral, right leg, and left leg countermovement jumps (CMJ). Results of the statistical analysis revealed no significant difference in TTS between the vibration and non-vibration conditions for the bilateral (p = 0.24) and right leg (p = 0.48) CMJ. A significant difference was found between the conditions demonstrating a shorter TTS in the non-vibration condition for the left leg CMJ (p = 0.04, d = 0.57, ηp ² = 0.36). Acute WBV has no effect on and in some cases impairs dynamic

THE EFFECT OF REMOTE VOLUNTARY CONTRACTIONS DURING FAST STRETCH SHORTENING CYCLE ACTIVITY

This study evaluated the effect of remote voluntary contractions (RVC) on depth jump performance. Subjects performed the depth jump in a RVC condition and a condition without RVC (NO-RVC). Ground reaction force (GRF), impulse (I), and reactive strength index (RSI) were assessed with a force platform. Data were analyzed using a two way ANOVA. Analysis of GRF showed no significant main effects for RVC condition (p = 0.46) and no interaction for RVC condition and gender (p = 0.11). Analysis of I showed no significant main effects for RVC condition (p = 0.99) and no interaction for RVC condition and gender (p = 0.61). Analysis of RSI showed no significant main effects for RVC condition (p = 0.78) and no interaction for RVC condition and gender (p = 0.20). Remote voluntary contractions appear to offer no performance benefits for exercises such as the depth jump

FORCE, VELOCITY, AND POWER ADAPTATIONS IN RESPONSE TO A PERIODIZED PLYOMETRIC TRAINING PROGRAM

This study assessed kinetic, kinematic and temporal adaptations to the countermovement jump in response to a 6 week periodized plyometric training program. Twenty recreationally active women were randomly assigned to a plyometric training or control group. Testing consisted of 3 maximal countermovement jumps on a force platform prior to and after the six weeks of training. A two-way repeated measures ANOVA was used to assess differences between pre- and post-testing sessions and between groups. Post-test eccentric and concentric velocity, power and jump height were significantly greater (p < 0.05) in the training group. Periodized plyometric training is effective for increasing jump height, and augmentations are likely due to enhanced eccentric velocity

THE EFFECT OF REMOTE VOLUNTARY CONTRACTIONS ON STRENGTH AND POWER TASKS OF WOMEN

This study evaluated the effect of remote voluntary contractions (RVC’s) on the performance of closed kinetic chain exercises. Subjects performed the squat and jump squat in a RVC condition and a condition without RVC’s (NO-RVC’s). Peak ground reaction force (GRF), rate of force development during the first 100 ms (RFD 100), RFD to peak GRF (RFD-P), and jump squat height (JH) were assessed with a force platform. Data were analyzed with a one way ANOVA. Results revealed there were no significant differences between RVC and NO-RVC conditions for peak GRF for either the squat (p = 0.11) or jump squat (p = 0.47), RFD 100 for either the squat (p = 0.25) or jump squat (p = 0.23), RFD-P for either the squat (p = 0.88) or jump squat (p = 0.38), or for JH for the jump squat (p = 0.68)

GENDER DIFFERENCES IN KNEE EXTENSOR AND FLEXOR PERFORMANCE

The purpose of this study was to evaluate gender differences in peak torque (PT), rate of torque development (RTD), power, and work during isometric (ISOM) knee extension and isokinetic (ISOK) knee extension and flexion. Forty-four university women and men volunteered to perform the test exercises on a computerized dynamometer. Data were reduced with manufacturer software and were analyzed with an independent-samples t-test in order to determine gender differences. Results revealed significant differences (P &#8804; 0.001) for ISOM PT and ISOK PT, RTD, power, and work. Gender differences in knee extensor and flexor performance are present, with women demonstrating a range of 68.9 to 76.9% of their male counterparts. Conversely, the rate of force production is not gender specific during ISOM knee extension

THE ACUTE TIME COURSE OF CONCURRENT ACTIVATION POTENTIATION

This study evaluated the acute time course of the ergogenic effect of concurrent activation potentiation (CAP). Forty-two men and women, including CAP non-responders and responders, performed a 5 second isometric knee extension on a dynamometer with the use of remote voluntary contractions (RVC). Mean torque was assessed in seven 500 millisecond (ms) time periods. A two-way repeated measures ANOVA revealed significant main effects for time period (p &#8804; 0.001), but no significant interaction between time period and CAP non-responders and responders (p > 0.05). The ergogenic effects of CAP are accrued during the first 1000ms. Concurrent activation potentiation responders produce greater initial force than the CAP non-responders, without a concomitant acceleration in force decay throughout the time course

ECCENTRIC MUSCLE ACTIONS PRODUCE 36% TO 154% LESS ACTIVATION THAN CONCENTRIC MUSCLE ACTIONS

This study evaluated the differences in eccentric and concentric phase muscle activation of variety of muscles during lower body resistance training exercises. Surface electromyography data (EMG) from 12 subjects was analyzed for the eccentric and concentric phases of the squat, deadlift, step-up, and lunge. Data from the test exercises were averaged for the eccentric and concentric phase for each muscle group to produce a comprehensive measure of activation differences between the eccentric and concentric phases. A paired samples t-test revealed differences between eccentric and concentric phase activation for all muscles assessed (p &#8804; 0.05). Results demonstrated that during lower body multi-joint exercises the eccentric phase produced 36% to 154% less muscle activation that the concentric phase

RATE OF FORCE DEVELOPMENT AND TIME TO PEAK FORCE DURING PLYOMETRIC EXERCISES

Rate of force development (RFD) during the first 100 and 250 msec of the positive acceleration phase of plyometric exercises and time to peak force were determined in 23 NCAA Div. I athletes. Subjects performed a countermovement jump (CMJ), cone hop (CH), tuck jump (TJ), single leg CMJ (SLJ), and squat jump with 30% 1 RM squat (SJ30) on a force platform. Results showed SLJ and SJ30 had lower RFD100 and higher time to peak force, while CH and TJ had higher RFD100 and shorter time to peak force. These findings are in agreement with previous research that shows that quick movement exercises have high RFD. However, RFD250 may be an inappropriate measure to classify very quick jumps, such as the CH, because RFD values approach zero or become negative when subjects are close to or already leaving the ground

RELIABILITY OF THE REACTIVE STRENGTH INDEX AND TIME TO STABILIZATION DURING DEPTH JUMPS

Reliability of reactive strength index (RSI) and time to stabilization (TTS) was examined during three maximal effort depth jumps from 30cm (N=22). Measures of jump height (JH), ground contact time (CT), RSI and TTS were obtained and analyzed for reliability. The JH, CT and RSI were shown to be highly reliable from trial-to-trial (ICCsingle > 0.9). Time to stabilization was not reliable from trial-to-trial (ICCsingle < 0.5). The RSI can be used to monitor performance or to optimize the height of depth jumps. Results suggest that coaches utilizing these procedures with large numbers of athletes may be able to use a single measure of RSI rather than repeated trials. Time to stabilization reliability must be improved before attempting to use it to quantify the landing phase of plyometric exercises

ELECTROMYOGRAPHICAL ANALYSIS OF LOWER EXTREMITY MUSCLE ACTIVATION DURING VARIATIONS OF THE LOADED STEP UP EXERCISE

This study evaluated the biceps femoris, gluteus maximus, gluteus medius, rectus femoris, semitendonosus, vastus lateralis, and vastus medialis activation during four variations of the step up exercise. The exercises included the step up, crossover step up, diagonal step up, and lateral step up. Fifteen women who regularly engaged in lower body resistance training performed the four exercises with 6RM loads on a 45.72cm plyometric box. Data were collected with a telemetered EMG system, and RMS values were calculated for EMG data for eccentric and concentric phases. Results of a repeated measures ANOVA (p&#8804;0.05) revealed a variety of differences in muscle activation between the exercises