Abstract
Time-of-day dependent fluctuations in exercise performance have been documented across different sports and seem to affect both endurance and resistance modes of exercise. Most of the studies published to date have shown that the performance in short-duration maximal exercises (i.e. less than 1 min - e.g. sprints, jumps, isometric contractions) exhibits diurnal fluctuations, peaking between 16:00 and 20:00 h. However, the time-of-day effects on short duration exercise performance may be minimized by the following factors: (1) short exposures to moderately warm and humid environments; (2) active warm-up protocols; (3) intermittent fasting conditions; (4) warming-up while listening to music; or (5) prolonged periods of training at a specific time of day. This suggests that short-duration maximal exercise performance throughout the day is controlled not only by body temperature, hormone levels, motivation and mood state but also by a versatile circadian system within skeletal muscle. The time of day at which short-duration maximal exercise is conducted represents an important variable for training prescription. However, the literature available to date lacks a specific review on this subject. Therefore, the present review aims to (1) elucidate time-of-day specific effects on short-duration maximal exercise performance and (2) discuss strategies to promote better performance in short-duration maximal exercises at different times of the day.
Highlights
Circadian rhythms are responsible for temporal regulation of numerous physiological phenomena in the human body
The inclusion criteria that were applied to original articles included: (1) the study explored the effects of time of day on one or more aspects of exercise performance; (2) the study assessed time-of-day effects on isometric, isokinetic and dynamic short-duration maximal exercises (3) the study assessed the effects of either acute or chronic interventions on time-of-day dependent fluctuations in exercise performance; (4) the study assessed either direct or indirect (i.e. RPE, neuromuscular efficiency, markers or muscle injury) features of exercise performance; (5) the study was published in indexed journals and was available in English
In order to explore the influence of time of day on dynamic short-duration maximal exercise performance, several studies have assessed the presence of time-of-day dependent fluctuations in both continuous and intermittent exercises
Summary
Circadian rhythms are responsible for temporal regulation of numerous physiological phenomena in the human body. Apart from the core clock system in the SCN, circadian clocks and clock-controlled output genes (CCGs) are present in peripheral tissues such as the liver, heart, kidney, pancreas, adipose tissue and skeletal muscle[6,7,8,9,10,11,12] In this sense, the main synchronizer of the internal clock is solar light[13], but it is known that other non-photic stimuli such as feeding, social contact or physical exercise do modulate the transcriptional activity of clock genes[14,15,16,17]. Short-duration maximal exercises (i.e. less than 1 min - e.g. all-out sprints, maximal jumps or isometric contractions) comprise both modes of exercise and are characterized by higher locomotor requirements[31] and anaerobic energy contributions[32] than longer exercises They represent a robust model to explore time-of-day effects on the musculoskeletal system. The present review aims to (1) elucidate time-of-day specific effects on short-duration maximal exercise performance and (2) discuss strategies to promote better performance in short-duration maximal exercises at different times of the day
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