Effects of Time of Day on Pacing in a 4-km Time Trial in Trained Cyclists

Abstract

Context: Time of day has been shown to impact athletic performance, with improved performance observed in the late afternoon–early evening. Diurnal variations in physiological factors may contribute to variations in pacing selection; however, research investigating time-of-day influence on pacing is limited. Purpose: To investigate the influence of time-of-day on pacing selection in a 4-km cycling time trial (TT). Methods: Nineteen trained male cyclists (mean [SD] age 39.0 [10.7] y, height 1.8 [0.1] m, body mass 78.0 [9.4] kg, VO2max 62.1 [8.7] mL·kg−1·min−1) completed a 4-km TT on 5 separate occasions at 08:30, 11:30, 14:30, 17:30, and 20:30. All TTs were completed in a randomized order, separated by a minimum of 2 d and maximum of 7 d. Results: No time-of-day effects were observed in pacing as demonstrated by similar power outputs over 0.5-km intervals (P = .78) or overall mean power output (333.0 [38.9], 339.8 [37.2], 335.5 [31.2], 336.7 [35.2], and 334.9 [35.7] W; P = .45) when TTs were performed at 08:30, 11:30, 14:30, 17:30, and 20:30. Preexercise tympanic temperature demonstrated a time-of-day effect (P < .001), with tympanic temperature higher at 14:30 and 17:30 than at 08:30 and 11:30. Conclusion: While a biological rhythm was present in tympanic temperature, pacing selection and performance when completing a 4-km cycling TT were not influenced by time of day. The findings suggest that well-trained cyclists can maintain a robust pacing strategy for a 4-km TT regardless of time of the day.

Higher evening metabolic responses contribute to diurnal variation of self-paced cycling performance

“…These findings are in line with previous studies showing a greater endurance performance in the evening during a cycling time trial [ 10 , 14 , 19 , 30 ], intermittent running test [ 7 ] or self-paced running exercise [ 8 ]. However, these findings are in contrast with other studies demonstrating no diurnal variation of endurance performance in response to a self-paced cycling time trial: 4 km [ 9 ], 15 min [ 31 ], 4×5-min [ 17 ], submaximal cycling exercise [ 12 ], maximal cycling [ 32 ] or running [ 33 ] exercises. These discrepancies could be explained by the chronotype of the participants and/or the habitual training time [ 20 , 21 , 34 ].…”

“…Particularly, some previous investigations have shown better endurance performance in the evening compared to the morning during submaximal cycling [ 10 ] or maximal [ 11 ] running exercise. In contrast, findings from other studies failed to show significant diurnal variation of endurance performance during similar types of exercise [ 9 , 12 , 13 ].…”

“…Indeed, the diurnal variation of short-term performance has been widely confirmed by several previous studies with a nadir (minimum) in the morning and a peak (maximum) in the evening [ 1 , 3 , 4 , 5 , 6 ]. However, conflicting findings have been reported regarding the effect of TOD on long-duration endurance performance [ 1 , 7 , 8 , 9 ]. Particularly, some previous investigations have shown better endurance performance in the evening compared to the morning during submaximal cycling [ 10 ] or maximal [ 11 ] running exercise.…”

“…Although athletes’ pacing behaviour is widely recognized as an essential determinant of endurance performance, TOD effects have been examined considerably more during externally paced [ 1 , 6 , 7 ] than self-paced exercises [ 9 , 19 ]. To the best of the authors’ knowledge, only two studies have explored the diurnal variation of endurance performance and cardiorespiratory responses during self-paced cycling exercise [ 9 , 19 ].…”

“…Although athletes’ pacing behaviour is widely recognized as an essential determinant of endurance performance, TOD effects have been examined considerably more during externally paced [ 1 , 6 , 7 ] than self-paced exercises [ 9 , 19 ]. To the best of the authors’ knowledge, only two studies have explored the diurnal variation of endurance performance and cardiorespiratory responses during self-paced cycling exercise [ 9 , 19 ]. Findings from these studies were also controversial, with one of them showing faster completion time and higher V̇O 2 in the evening compared to the morning during a 1 km cycling time trial (TT) [ 19 ], while the second one reported no diurnal variation of the same parameters during a 3 km TT [ 9 ].…”