Relationship between objective and subjective hydration measures on sprint performance among soccer players during actual matches in hot and humid environment

BACKGROUND: Studies that investigate the effect of hydration on soccer performance in the heat are mostly carried out in a laboratory-controlled environment or simulated setting. Generally, on site, hydration is measured subjectively. Hence, the relationships between objective and subjective hydration measures during actual soccer matches in natural hot and humid environment with performance remain unclear.

METHODS: Forty-two soccer players (age: 27.34 ± 3.62 years; BMI: 23.80 ± 2.70 kg / m2; temperature: 30.8 ± 1.92 º C; humidity: 82 ± 1.4 %) hydration status were assessed using urine specific gravity (USG) and bodyweight (BW) as the objective measures, meanwhile, thirst was measured subjectively using a thirst scale. For performance evaluation, 20 and 50 m sprint time were measured before and after match.

RESULTS: The results showed a significant relationship between USG and sprint time (r = 1.00 (CI 0.98 - 0.99); p < 0.05), and as expected, USG at post-match was significantly higher than pre-match (p < 0.05) indicating dehydration. In line, changes (between post and pre-match) in BW also showed positive relationship with changes in sprint time (r = 0.99 (CI 0.98 - 0.99); p < 0.05). Not to our expectation, the self-reported thirst level was not found to be correlated with USG and sprint time.

CONCLUSIONS: Objective measures better reflect hydration status and predict sprint performance compared to subjective measure when playing in hot and humid environment. Players need to monitor their hydration status to maintain their sprint performances.