Hypohydration reduces vertical ground reaction impulse but not jump height

Abstract

This study examined vertical jump performance using a force platform and weighted vest to determine why hypohydration (approximately 4% body mass) does not improve jump height. Measures of functional performance from a force platform were determined for 15 healthy and active males when euhydrated (EUH), hypohydrated (HYP) and hypohydrated while wearing a weighted vest (HYP(v)) adjusted to precisely match water mass losses. HYP produced a significant loss of body mass [-3.2 +/- 0.5 kg (-3.8 +/- 0.6%); P < 0.05], but body mass in HYP(v) was not different from EUH. There were no differences in absolute or relative peak force or power among trials. Jump height was not different between EUH (0.380 +/- 0.048 m) and HYP (0.384 +/- 0.050 m), but was 4% lower (P < 0.05) in HYP(v) (0.365 +/- 0.52 m) than EUH due to a lower jump velocity between HYP(v) and EUH only (P < 0.05). However, vertical ground reaction impulse (VGRI) was reduced in both HYP and HYP(v) (2-3%) compared with EUH (P < 0.05). In conclusion, this study demonstrates the failure to improve jump height when HYP can be explained by offsetting reductions in both VGRI and body mass.

Effect of Hypohydration on Muscle Endurance, Strength, Anaerobic Power and Capacity and Vertical Jumping Ability: A Meta-Analysis

“…Of these, 129 were considered trained [11, 12, 18, 24, 32-34, 36, 37, 40-42, 44] and 155 untrained [7,8,13,14,17,19,20,25,30,31,33,35,38,39,43,45]. Their physical characteristics are presented in Table 2.…”

“…The correlation coefficient was imputed [22] and taken as 0.56, which represents the weighted mean correlation coefficient computed from the raw experimental results of 20 individual studies provided by six researchers [7,11,14,17,24,25]. Several research articles included more than one treatment effect for a given type of muscle performance.…”

“…In fact, following this time point, any residual effects of exercise [11,12] or heat stress [13,14] were considered null.…”

“…Of the 28 articles retained for analysis, hypohydration was induced via heat exposure in ten [8, 17, 33, 35-38, 40, 42, 44], via exercise plus heat exposure in ten [13,14,18,19,24,25,30,39,41,43], via exercise in a sweat suit in two [34,45], and via fluid restriction in six [7,11,12,20,31,32]. Although Webster et al [12] used exercise in a sweat suit and Judelson et al [11] used exercise plus heat exposure to dehydrate participants, the dehydration mode was All studies except that by Bosco et al [31] provided the percent change in BW (i.e., hypohydration level).…”

“…In fact, our results demonstrate that hypohydration impacts jumping performance in a manner different from its effect on muscle endurance, strength, and anaerobic capacity and power. Moreover, any physiological disadvantage associated with hypohydration for this variable may potentially be offset by a ''BW'' advantage [14]. Categorical variables were dummy-transformed with k -1, where k is the number of levels of the original variable.…”