Pre-Exercise Hypohydration Effects On Jumping Ability And Muscle Strength, Endurance And Anaerobic Capacity: A Meta-Analysis

Abstract

A recent systematic review reported that pre-exercise hypohydration (PEH) impairs skeletal muscle performance. The extent to which PEH influences muscular performance-related outcomes remains to be quantified using standard meta-analytic procedures. PURPOSE: To determine the magnitude of the effects of PEH on leg and arm muscle strength, leg muscle endurance and anaerobic capacity, and jumping ability using a meta-analytic approach. METHODS: Studies were located via database searches and cross-referencing. Inclusion criteria: standard measures of muscular performance; hydration level in the euhydrated control group < 0.5% ≥ -1% bodyweight (BW); hypohydration level in the experimental group > 1% BW and > 0.5% than control BW. Exclusion criteria: diuretics- and caloric restriction-induced BW loss. Results were analyzed using a random-effect model for mean weighted summary effects and a random-effect analog to the ANOVA for subgroup analyses. RESULTS: Thirty-five research articles were retrieved, among which 11, 4, 7 and 4 met the inclusion criteria for muscle strength, muscle endurance, anaerobic capacity and jumping ability, respectively, providing 27, 7, 11 and 11 effect estimates. Mean BW decrease in experimental groups was 3.0 ± 1.4%, 3.2 ± 0.5%, 3.2 ± 1.2% and 2.5 ± 1.3% for muscle strength, muscle endurance, anaerobic capacity and jumping ability, respectively (range: 1.3 to 5.7%). Mean muscle strength fell by 4.6% (95% CI: 2.9 to 6.3%) with PEH relative to control, with leg (3.8%, 95% CI: 0.4 to 7.2%) and arm (4.8%, 95% CI: 2.9 to 6.8%) strength declining similarly. PEH resulted in a mean decrease in muscle endurance of 11.7% (95% CI: 0.002 to 23.4%) and a decline in anaerobic capacity by 5.7% (95% CI: 1.5 to 9.9%). When pooled together, results of studies indicated that the decline in muscular performance is not significantly different between studies with BW losses ≤ or > 3%. PEH did not alter jumping ability compared with control. CONCLUSIONS: PEH of 1.5 to 5.5% BW does not affect jumping ability, but decreases leg (-4%) and arm (-5%) muscle strength, as well as leg muscle endurance (-12%) and anaerobic capacity (-6%) in a significant and practical manner. The opinions or assertions contained herein should not to be construed as official or reflecting the views of the Army or the DoD.