The Effect Of Time Of Day On Jump Potentiation In Distance Runners

Abstract

The Effect of Time of Day on Jump Potentiation in Distance Runners. Time of day is a key factor that influences athletic performance. No study has specifically investigated the effect of early morning vs. late afternoon training on jump potentiation in distance runners. This is important because circadian rhythms and alterations in sleep patterns can affect training adaptations and athletic performance. PURPOSE: To determine whether the time of day influence jump potentiation in distance runners. METHODS: We recruited 18 male runners that were divided into two groups: novice runners (NOV) with ≤3 years of racing experience (n=6; age 34.7±6.4) and experienced runners (EXP) with ≥3 years of experience (n=12; age 34.5±5.1). Chronotypes were identified using the Horne-Ostberg's Morningness-Eveningness questionnaire and sleep quality was assessed with the Pittsburgh Sleep Quality Index. Counter movement jump (CMJ) was determined with the My Jump App. CMJ height was measured after 5 min warm-up and after 30 min test (70% HRR) of running on a treadmill at 8:00 am and 8:00 pm. Following the 30 min test treadmill CMJ height was measured at 0, 3, 6 and 9 minutes of recovery. RESULTS: The overall sleep quality of the athletes were poor (5.4 ±3.8, n=18). The NOV group were poor sleepers (6.5±3.6, n=6) whereas the EXP group were at the limit score to become poor sleepers (4.8±3.9 n=12). The majority (77.3%, n=14) of the runners were morning types and 22.2% (n=4) were intermediate types. CMJ height in the EXP group was increased at 0 min of recovery and was decreased to warm-up levels at 3, 6 and 9 min (p< 0.01) during morning test. Interestingly, jump potentiation only occurred in the morning while no significant increases were observed in the evening in the EXP group (p=0.6). The NOV group had no changes in jump potentiation in both morning and evening tests. CONCLUSION: We conclude that jump potentiation could be only observed during morning in experienced distance runners probably because of their chronotypes.