Fluid loss during tennis matches is associated with reduced muscle strength in sport-specific limbs

BACKGROUND: Dehydration is common in tennis, yet the relationship between fluid loss and muscle strength during actual match play remains unclear. This study examined the association between body water loss and changes in muscle strength in competitive university tennis players. METHODS: A cross-sectional study was conducted with 20 male university tennis players (age: 20.6±1.6 years) during the regional qualifying round of the All Japan Student Indoor Tennis Championships. Body mass, grip, back, and toe strength were measured before and immediately after matches. Body water loss was calculated from body mass changes, and associations between fluid loss and changes in muscle strength were examined using Pearson's correlation coefficients. RESULTS: Mean body water loss was 0.7±0.8%. Although overall pre-post differences in muscle strength were not significant, body water loss was negatively correlated with changes in right-hand grip strength (r=-0.54, P<0.05) and toe strength in both feet (right: r=-0.45, P<0.05; left: r=-0.58, P<0.01). After adjusting for total games played, the associations remained significant for right-hand grip strength (partial r=-0.60, P=0.007) and left toe strength (partial r=-0.58, P=0.009). Subjective fatigue increased significantly but was not associated with strength changes. CONCLUSIONS: Mild body water loss during competitive tennis matches was associated with reductions in muscle strength in some frequently used limbs. However, given the modest level of dehydration and the correlational design of the study, these findings should be interpreted cautiously, as match workload may have influenced both fluid loss and neuromuscular responses.