Research examining postactivation potentiation (PAP) in recreationally trained individuals (RTI) shows mixed results. Because the balance of PAP and fatigue after heavy-load exercise influences performance outcomes, recovery duration after the stimulus might explain inconsistent results noted in RTI. The purpose of this study was to investigate the effect of recovery duration after a potentiating stimulus on muscular power in RTI. Twelve healthy RTI males (age = 23 +/- 1 yr, height = 174.6 +/- 2.5 cm, mass = 86.3 +/- 6.6 kg, 1 repetition maximum [1RM]:mass = 1.4 +/- 0.1, body fat = 15.1 +/- 2.5 %) minimally possessing 1 year of back squat experience participated. A control session assessed baseline measures on a 30-second Wingate Test. During experimental sessions, subjects performed a back squat exercise (1 set of 5 repetitions at 85% 1RM), rested for 5, 10, 15, or 20 minutes, and performed the Wingate Test. No significant differences existed among control and experimental conditions in all outcome variables; however, maximal values (regardless of rest duration) for absolute peak power (APpwr) (+7.1%), relative peak power (RPpwr) (+7.1%), and fatigue index (FI) (+8.9%) significantly differed from respective control values. The rest duration eliciting maximal PAP significantly correlated (r = -0.771) with relative 1RM. Although recovery duration failed to influence performance after a heavy-load exercise in RTI, discrepancies in individual strength might have influenced the time subjects potentiated. These results suggest stronger subjects might potentiate with less rest after a stimulus (5-10 min), whereas weaker subjects require longer rest durations (15-20 min).

Because of the relative newness of mouthpieces, there are few investigations into using performance mouthpieces during sport and physical activity to substantiate claims of performance enhancement. The purpose of this study was to investigate the acute effect of a commercially available, noninjury preventive, performance mouthpiece on practical acute performance measures of power and strength. A within-subjects design was used to evaluate 21 (N = 21) recreationally trained college aged males on the performance of a maximum countermovement vertical jump (CMVJ) from a force platform and 1 repetition maximum (1RM) bench press exercise for the following conditions: with mouthpiece (MP) and without mouthpiece (noMP). Rate of force development (RFD) and peak vertical force (PF) were derived from force platform data. Statistical analysis revealed no significant differences between conditions for CMVJ height (p = 0.13), RFD at 200 ms (p = 0.09), PF (p = 0.08), and 1RM bench press (p = 0.45). These data indicate that the use of this particular jaw aligning mouthpiece specifically in an attempt to produce an ergogenic effect on performance is unwarranted.

Whole-body vibration (WBV) may potentiate vertical jump (VJ) performance via augmented muscular strength and motor function. The purpose of this study was to evaluate the effect of different rest intervals after WBV on VJ performance. Thirty recreationally trained subjects (15 men and 15 women) volunteered to participate in 4 testing visits separated by 24 hours. Visit 1 acted as a familiarization visit where subjects were introduced to the VJ and WBV protocols. Visits 2-4 contained 2 randomized conditions per visit with a 10-minute rest period between conditions. The WBV was administered on a pivotal platform with a frequency of 30 Hz and an amplitude of 6.5 mm in 4 bouts of 30 seconds for a total of 2 minutes with 30 seconds of rest between bouts. During WBV, subjects performed a quarter squat every 5 seconds, simulating a countermovement jump (CMJ). Whole-body vibration was followed by 3 CMJs with 5 different rest intervals: immediate, 30 seconds, 1 minute, 2 minutes, or 4 minutes. For a control condition, subjects performed squats with no WBV. There were no significant (p> 0.05) differences in peak velocity or relative ground reaction force after WBV rest intervals. However, results of VJ height revealed that maximum values, regardless of rest interval (56.93 ± 13.98 cm), were significantly (p < 0.05) greater than the control condition (54.44 ± 13.74 cm). Therefore, subjects' VJ height potentiated at different times after WBV suggesting strong individual differences in optimal rest interval. Coaches may use WBV to enhance acute VJ performance but should first identify each individual's optimal rest time to maximize the potentiating effects.

Cooper, CN, Dabbs, NC, Davis, J, and Sauls, NM. Effects of lower-body muscular fatigue on vertical jump and balance performance. J Strength Cond Res 34(10): 2903–2910, 2020—Lower-body fatigue can lead to a decline in vertical jump (VJ) and balance performance due to decreased motor control and coordination. The purpose is to determine the effects of lower-body fatigue on VJ and balance performance. Twenty-four recreationally trained individuals participated in a single 1-hour familiarization and testing session. Participants were familiarized with balance, countermovement vertical jump (CMVJ), and static vertical jump (SVJ) using the Vertec. Three trials of static and dynamic balance tests were completed. Three trials of a SVJ and CMVJ were completed in a randomized order pre/post fatigue protocol. Three trials of double-leg and single-leg tests were performed. Dependent t tests analyzed differences between pre/post fatigue protocol for jumping and balance measures. There was a significant (p < 0.001) difference between pre/post measures for SVJ-H (height), CMVJ-H, and CMVJ peak power (PP). Results showed an interaction (p < 0.05) for group by time for CMVJ-H, CMVJ-peak force (PF), SVJ-PF, and SVJ-PP. There were no main effects (p > 0.05) for time or group for SVJ-rate of velocity development and SVJ-impact force (IF). There were no interactions, time effects, and group effects for balance variables (p > 0.05). Bosco protocol decreased VJ height and PF in SVJ, and VJ height and PF, IF, peak velocity, and PP for CMVJ potentially due to decreased muscle control, coordination, and force-generating capacity after fatigue. Practitioners should consider fatiguing effects on individuals performing jumping motions but it seems that fatigue has no effect on balance.

Whole-body vibration (WBV) may enhance human performance via augmented muscular strength and motor function if used before performance. Because warm-up is a crucial aspect of preparation for performance, it remains unknown if WBV may enhance bat speed. The purpose of this study was to investigate the effect of WBV warm-up on bat speed. Eleven National Collegiate Athletic Association division I and 11 recreationally trained female softball players volunteered to participate. Subjects randomly performed 3 different warm-up conditions consisting of WBV alone, dry swings alone (DS), and WBV with dry swings (WBVDS). Whole-body vibration was performed on a pivotal vibration platform at a frequency of 25 Hz and an amplitude of 13 mm for one 30-second bout. Thirty seconds after each warm-up condition, 5 maximal bat swings were recorded. There was no significant (p > 0.05) difference between groups by training status, and there was no significant (p > 0.05) difference between WBV (42.39 +/- 9.83 mph), DS (40.45 +/- 11.00 mph), or WBVDS (37.98 +/- 12.40 mph) conditions. These results indicate that WBV warm-up may be used in place of DS to achieve similar bat speeds. Future research should investigate different combinations of WBV warm-up using various frequencies, durations, amplitudes, and rest times.

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Context: Research into alleviating muscle pain and symptoms in individuals after delayed-onset muscle soreness (DOMS) has been inconsistent and unsuccessful in demonstrating a useful recovery modality.Objective: To investigate the effects of short-term wholebody vibration (WBV) on DOMS over a 72-hour period after a high-intensity exercise protocol.Design: Randomized controlled clinical trial. Setting: University laboratory.Patients or Other Participants: Thirty women volunteered to participate in 4 testing sessions and were assigned randomly to a WBV group (n ¼ 16; age ¼ 21.0 6 1.9 years, height ¼ 164.86 6 6.73 cm, mass ¼ 58.58 6 9.32 kg) or a control group (n ¼ 14; age ¼ 22.00 6 1.97 years, height ¼ 166.65 6 8.04 cm, mass ¼ 58.69 6 12.92 kg).Intervention(s): Participants performed 4 sets to failure of single-legged split squats with 40% of their body weight to induce muscle soreness in the quadriceps. The WBV or control treatment was administered each day after DOMS.Main Outcome Measure(s): Unilateral pressure-pain threshold (PPT), range of motion (ROM), thigh circumference, and muscle-pain ratings of the quadriceps were collected before and for 3 days after high-intensity exercise. Each day, we collected 3 sets of measures, consisting of 1 measure before the WBV or control treatment protocol (pretreatment) and 2 sets of posttreatment measures.Results: We observed no interactions for PPT, thigh circumference, and muscle pain (P . .05). An interaction was found for active ROM (P ¼ .01), with the baseline pretreatment measure greater than the measures at baseline posttreatment 1 through 48 hours posttreatment 2 in the WBV group. For PPT, a main effect for time was revealed (P , .05), with the measure at baseline pretreatment greater than at 24 hours pretreatment and all other time points for the vastus medialis, greater than 24 hours pretreatment through 48 hours posttreatment 2 for the vastus lateralis, and greater than 24 hours pretreatment and 48 hours pretreatment for the rectus femoris. For dynamic muscle pain, we observed a main effect for time (P , .001), with the baseline pretreatment measure less than the measures at all other time points. No main effect for time was noted for thigh circumference (P ¼ .24). No main effect for group was found for any variable (P . .05).Conclusions: The WBV treatment approach studied did not aid in alleviating DOMS after high-intensity exercise. Further research is needed in various populations.Key Words: range of motion, edema, pressure-pain threshold Key PointsExposure to whole-body vibration did not effectively manage delayed-onset muscle soreness after high-intensity exercise in healthy, recreationally trained women. Researchers should study treatments to alleviate muscle pain in various populations.

Enhancing vertical jump performance is critical for many sports. Following high intensity training, individuals often experience exercise induced muscle damage (EIMD). Many recovery modalities have been tested with conflicting results. The purpose of this investigation was to determine the effect of whole-body vibration (WBV) on vertical jump performance following EIMD. 27 females volunteered for 7 sessions and were randomly assigned to a treatment or control group and administered each testing day. Vertical jump performance was assessed via vertical jump height (VJH), peak power output (PPO), rate of force development (RFD), relative ground reaction force (GRFz), and peak activation ratio of the vastus medialis (VM) via electromyography (EMG) before and after 3 days of EIMD via split squats. Two testing sets were collected each day, consisting of pre measures followed by WBV or control, and then post second measures. A 2x8 (group x time) mixed factor analysis of variance (ANOVA) was conducted for each variable. No significant interactions or group differences were found in any variable. Significant main effects for time were found in any variable, indicating performance declined following muscle damage. These results indicate that WBV does not aid in muscle recovery or vertical jump performance following EIMD.