The effect of pre-sleep meals with high glycemic index and tryptophan content on sleep profile and athletic performance in female handball players

Nutrition and sleep are critical for athletic performance. The nutrient content of the meals consumed can affect time, sleep and athletic performance. Changes in sleep profile may cause changes in athletic performance. The aim of this study was to investigate the effects of high glycemic index meal (HGIM) and high tryptophan content meal (HTCM) consumed 4 hours before bedtime on sleep profile and athletic performance in female handball players. The study included 16 female handball players over 18 years of age who played in the Super League and volunteered to participate in the study. The participants were divided into two groups by simple randomization method, i.e., the HGIM and the HTCM. The HGIM group consumed a meal with a glycemic index of ≥70, and the HTCM group consumed a meal containing ≥60mg tryptophan 4 hours before bedtime. The sleep profile of the study [length of stay in bed, total sleep time (TST), wakefulness time, sleep efficiency (SE), frequency of awakening after sleep onset (WASO), sleep onset latency (SOL), and sleep stages; Rapid eye movement (REM), light non-rapid eye movement (NREM) and deep NREM, sleep duration and rates] and resting and morning heart rate (HR) were measured with Fitbit smart wristbands for 7 days (3 days pre-intervention, 4 days intervention). Aerobic performance was measured by 30-15 intermittent fitness test (IFT) and anaerobic performance was measured by vertical jump test. According to the results, there was no significant difference between the HGIM and the HTCM groups in terms of TST, SE, WASO, SOL and sleep stages (p>0.05). However, there was a significant increase in length of stay in bed, TST, wakefulness time, REM and mild NREM sleep stages after 1 day intervention in the HTCM group (p<0.05). There was no significant difference between the groups in resting HR and morning HR (p>0.05). However, there was a statistically significant decrease in the mean morning HR after 4 days of intervention in the HGIM group (p<0.05). There was no significant difference between the groups in the pre- and post-test results of 30-15 IFT (VO2max and speed) and vertical jump test (power and height) (p>0.05). However, there was a statistically significant increase in 30-15 IFT in both groups after 4 days of intervention (p<0.05). In vertical jump, no significant change was found in both groups (p>0.05). According to the findings of this study, it was determined that consumption of a meal with high tryptophan content 4 hours before bedtime affected sleep stages, consumption of a high glycemic meal decreased morning HR, and consumption of a tryptophan-rich and high glycemic index meal 4 hours before bedtime increased aerobic performance in female handball players. In conclusion, planning the timing of nighttime meals and regulating the tryptophan content and glycemic index of meals may contribute to improving athletic performance and reducing the risk of overtraining in athletes.