Good sleep is a prerequisite for optimal performance. Given that people spend about one-third of their lives asleep, sleep has substantial development, daily functioning, and health. Perhaps no daytime behavior has been associated more closely with improved sleep than exercise. Researchers have shown that exercise serves as a positive function for sleep. Regular exercise consistently has been associated with better sleep. Moreover, the American Academy of Sleep Medicine considers physical exercise a modality of nonpharmacologic treatment for sleep disorders. When studying the influence of exercise on sleep, most investigators have compared acute and sedentary control treatments. In the study of regular moderate-intensity endurance exercise, researchers also provided compelling evidence that exercise promotes sleep.
However, exercise can negatively affect sleep quality. Exercising immediately before going to sleep is detrimental to sleep quality. Athletes train very hard to improve their on-field performances, but excessive training may decrease performance, known as overtraining syndrome. Researchers have shown that symptoms of overtraining indicate poor-quality sleep. Good sleep is an important recovery method for the prevention and treatment of overtraining in sports practice.
In a recent study in which red-light therapy (wavelength = 670 nm, light dose = 4 J/cm2) was used, researchers indicated that red light could restore glutathione redox balance upon toxicologic insult enhance both cytochrome c oxidase and energy production, all of which may be affected by melatonin. Melatonin is a neurohormone that is produced by the pineal gland and regulates sleep and circadian functions. No one knows whether sleep is regulated by melatonin after red-light irradiation in athletes. Researchers have demonstrated that phototherapy improves muscle regeneration after exercise. A red light could protect human erythrocytes in preserved diluted whole blood from the damage caused by experimental artificial heart-lung machines.
Twenty female athletes of the Chinese People’s Liberation Army team (age = 18.60 ± 3.60 years) participated in the study. All participants were healthy and were not using medications regularly or temporarily during the measurements. Athletes were excluded if they had participated in less than 80% of the scheduled team physical training and basketball sessions for the last 3 months or used any nutritional supplements or pharmacologic agents. All participants provided written informed consent, and the Ethical Committee approved the China Institute of Sport Science study.
Participants were assigned randomly to either a red-light therapy intervention group (n = 10) or non–red-light therapy intervention group (placebo group, n = 10). Measurements were collected at preintervention (baseline) and postintervention (14 days). The exercise training schedule of the 2 groups was unchanged during the 14 days; the red-light treatment group used a red-light therapy instrument every night for total body irradiation for 30 minutes. The training routine of the athletes during the 14 intervention days included 12 exercise sessions with the following specifications: 2 hours of morning training, 2 hours of afternoon training, and no training on Sunday.
The red-light treatment participants lay in the supine position. Continuous illumination was performed using noncoherent red light from a whole-body red-light treatment machine-like Kaiyan’s red light therapy bed, with an average wavelength of 658 nm and a light dose of 30 J/cm2. The whole body received the phototherapy treatment. The placebo participants also lay in the supine position under the red-light device but did not receive any light illumination. All participants wore swimsuits to enhance irradiation from the device and were blind to the treatment.
The Chinese version of the PSQI measured sleep quality. The 19-item measure assesses sleep quality and disturbances over a half-month time interval. The total PSQI score ranges from 0 to 21, and higher scores reflect poorer-quality sleep. The 7 items of this instrument measure several aspects of insomnia: difficulties with onset and maintenance of sleep, satisfaction with the current sleep pattern, interference with daily functioning, noticeable impairment attributed to sleep problems, degree of distress, and concern caused by any sleeping problems.
Participants were instructed to complete as many laps as possible on a 400-m outdoor track during the 12-minute test period. Emphasis was placed on pacing oneself throughout the test. The test administrators counted the laps completed during the 12-minute test period while calling out the time elapsed at 3, 6, and 9 minutes and orally encouraging the participants. At the end of the 12-minute period, the test administrator instructed the participants to stop and used a measuring wheel to determine the fraction of the last lap completed by each participant. This distance was added to the distance determined by the number of laps completed to give the total distance covered during the test.
In humans, the serum level of melatonin, derived mainly from the pineal gland, demonstrates a clear increase at night and a decrease during the day. Given that the masking effects of activities (e.g., exercise, sleep, and food intake) have little effect on the circulating melatonin level's daily pattern, melatonin secretion appears to directly reflect the function of the biological clock as a specific marker of the circadian rhythm.
The study has demonstrated that red-light illumination positively affected sleep quality and endurance performance variables in Chinese female basketball players. Based on previous studies, we can infer that red-light treatment contributes to increased melatonin secretion in the pineal gland and muscle regeneration. Although more studies involving phototherapy, sleep, and exercise performance need to be performed, red-light treatment is a possible nonpharmacologic and noninvasive therapy to prevent sleep disorders after training.
This research project was supported by the National Key Technologies R&D Program Fund of China (2006BAK37B06).
Originally from:
Red Light and the Sleep Quality and Endurance Performance of Chinese Female Basketball Players
Jiexiu Zhao, Ye Tian, Jinlei Nie, Jincheng Xu, Dongsen Liu
J Athl Train. 2012 Nov-Dec; 47(6): 673–678. doi: 10.4085/1062-6050-47.6.08
PMCID: PMC3499892
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