Temporal Effects On Anaerobic Performance: A Comparative Study Of Morning And Evening Sprint Tests

Anaerobic performance varies throughout the day, with evening measurements often demonstrating higher values for metrics like peak power and anaerobic capacity, particularly in laboratory settings. It is not known if field-based tests can demonstrate these differences. PURPOSE: To investigate the influence of time of day on anaerobic sprint performance in collegiate athletes using the Running-based Anaerobic Sprint Test (RAST). METHODS: Eleven physically active college students (5 females, 6 males (age: 23.6 ± 1.36, height: 172 ± 4.8, weight: 70.7 ± 9.24) participated in this trial. RAST protocol was used twice under standardized conditions: once in the morning (06:00-08:00) and once in the evening (17:00-19:00), with a three-day rest between sessions. The RAST protocol measured peak power output, anaerobic capacity, relative peak power, and fatigue index. Paired t-test was used to assess the differences in performance. RESULTS: No statistically significant differences were found between morning and evening performances on the RAST performance measures. However, evening peak power output, anaerobic capacity and relative peak power were higher than morning by 3.4%, 8.5%, and 13.8% (p > 0.05), respectively. Fatigue index was also 14% (p > 0.05) higher in the evening than in the morning (Table). CONCLUSION: Peak power, anaerobic capacity, and relative peak power show clinically meaningful increase in the evening as compared to morning. However, these differences are not statistically significant. Table: Differences in RAST performance between morning and evening - Variables Morning Evening p-value Peak power output (W) 422.73 ± 85.14 433.45 ± 109.63 0.91 Relative peak power output (W.kg-1) 6.45 ± 0.82 7.36 ± 1.36 0.85 Anaerobic capacity (W) 2097.02 ± 613.18 2171.14 ± 587.37 0.85 Fatigue Index (%) 26.09 ± 4.061 29.91 ± 4.76 0.89 Level of significance was set at p < 0.05