Abstract available in the Medicine & Science in Sports & Exercise.

PURPOSE: To examine changes in muscle architecture, reactive strength, and explosive ability in collegiate volleyball players throughout a competitive season. METHODS: Ten female volleyball players (20.4 ± 1.1 y, 178.3 ± 4.8 cm, 72.6 ± 5.3 kg) were recruited for the study. Athletes were tested at pre-season (T1), pre-taper (T2), and post-taper (T3) on measures of vastus lateralis muscle thickness (MT), pennation angle (PA), and fascicle length (FL) using ultrasonography, countermovement jump reactive strength index modified (RSImod), and peak power allometrically scaled (PPa). Training load (TL: session RPEduration) and strength training volume-load times displacement (VLd) were monitored for 15 wks. One-way repeated measures ANOVAs were used for analysis with alpha level set at p≤0.05. RESULTS: There was a reduction in VLd/wk (p<0.001, d=3.1) and TL/wk (p<0.001, d=2.7) between in-season (T1-T2) and tapering (T2-T3) training phases. There were time effects for MT (p<0.001) and PA (p=0.03). Post-hoc pairwise comparisons revealed changes in MT (increase T1-T2: p<0.001, d=2.8 and T1-T3: p<0.001, d=1.7; decrease T2-T3: p=0.01, d=0.6), PA (increase T1-T2: p=0.02, d=3.9), and no changes in FL or PPa. Despite no time effect, RSImod showed an increasing trend from T2-T3: p=0.04, d=0.23. CONCLUSIONS: In-season training resulted in favorable changes in muscle architecture, which remained elevated above pre-season values following the taper. These changes coupled with the reductions in TL and VLd during the taper may be related to changes in stretch-shortening cycle function during a sport-specific task as inferred from the changes in RSImod

PURPOSE: To examine the relationships between muscle architecture and countermovement jump height, peak power, and maximal strength in collegiate volleyball players. METHODS: Fifteen female volleyball players (20 ± 1.3y, 176.3 ± 6.6cm, 70.1 ± 8.4 kg) were recruited as part of an ongoing athlete monitoring program. Athletes were tested on measures of vastus lateralis (VL) and lateral gastrocnemius (LG) muscle thickness (MT), pennation angle (PA), and fascicle length (FL) using ultrasonography; countermovement jump height (CMJH, n = 14 and peak power allometrically scaled (CMJPPa, n = 14); and isometric peak force allometrically scaled (IPFa, n = 12). Pearson’s product moment zero-order correlations were used for analysis with critical alpha set to p ≤ 0.05. RESULTS: Analysis revealed a positive relationship between VL MT and IPFa (r = 0.64, p = 0.025) and an inverse relationship between LG MT and CMJH (r = -0.54, p = 0.048). There were positive relationships between VL PA and all performance measures and between LG PA and CMJPPa (r = 0.54 to 0.71, p. < 0.05), and inverse relationships between VL FL and CMJPPa and between LG FL and all performance measures (r = -0.59 to -0.67, p < 0.05). CONCLUSIONS: Better jumpers had larger PA and shorter FL in both VL and LG, and stronger athletes had greater MT in VL, showing that differences in muscle architecture can influence performance parameters. Considering these findings and the results from previous longitudinal studies demonstrating the effects of heavy strength training on muscle architecture, it is recommended that collegiate volleyball athletes incorporate heavy lower body strength training into their training plan in order to increase PA in VL and LG and MT in VL.