Does a post-workout high GI meal improve sleep and next day training performance?

Getting enough quality sleep is important for overall health. Although the function of sleep^[1] is not yet fully understood, it is generally accepted that by promoting the maintenance and recovery of the central nervous system and physical recovery, sleep serves as an important regulator of numerous biological aspects, maintaining vital physiological functions, metabolic homeostasis, learning, and memory.

In recent years, there has been a growing interest among the scientific community in the potential effects of sleep on athletic performance^[2], since there are many reasons why sleep could theoretically impact it, as outlined in Figure 1. Despite the finding that athletes generally seem to exhibit similar, or even slightly better, sleep duration and quality than the general public, many athletes have been consistently shown to sleep less than recommended. Moreover, sleep in athletes^[3] can also be undermined by competition, not just due to disturbances in mood, anxiety, and psychological stress, but also because of the great physical stress of high-volume^[4] or high-intensity^[5] exercise.

With sleep being an important part of the post-exercise recovery^[6] process, adequate quality sleep after exercise and before subsequent exercise bouts or athletic events is imperative for promoting sufficient recovery and optimal performance. As such, several strategies, including nutritional interventions to improve sleep, have been investigated. One such nutritional intervention^[7] involves carbohydrate consumption, as some research suggests that high carbohydrate^[8] or high glycemic index^[9] meals ingested close to bedtime may improve sleep by increasing blood tryptophan levels.

Despite the potential effects of carbohydrate consumption on sleep, and the potential effects of sleep on exercise performance, relatively little research has been conducted to investigate the links between these variables. Moreover, there is currently no research examining the effects of post-exercise carbohydrates on sleep and the subsequent effects on next-day exercise performance. The study under review aimed to add to the literature by investigating the effects of a high vs. low glycemic index (GI) meal after an evening high-intensity training (HIT) session on sleep quantity and quality, and on the following morning’s exercise performance in recreationally-trained men.

Sleep has been identified as an important factor contributing to optimal exercise recovery and athletic performance. However, the physical stress of high-intensity exercise may negatively affect sleep. While scientific evidence suggests that nutritional interventions involving carbohydrate ingestion close to bedtime can potentially improve sleep and subsequent exercise performance, little relevant research has been conducted to date. The study under review was the first to investigate the effects of a high vs. low glycemic index meal after an evening high-intensity exercise session on sleep and next-day exercise performance.