表題番号：2012A-083
日付：2013/10/21
研究課題スポーツパフォーマンス向上のための生体リズムコンディショニング技術の開発
| 研究者所属（当時） | 資格 | 氏名 | |
|---|---|---|---|
| （代表者） | スポーツ科学学術院 | 教授 | 内田 直 |
- 研究成果概要
- 本研究では次の３つの研究を行なっている。内１本は、英文論文として出版された。
１. スポーツパフォーマンスは、一日の中で様々な時間帯で変動する。一日のうち、時間帯別にスポーツに関わる様々なパフォーマンスがどのように変動するのかを調べた。
２．アスリートは、環境隔離室などで生体リズムシフトを行うことができないため、自然光のもとで、光を用いてどの程度位相のシフを行うことができるのかについての実験を行った。
３．一日の早起きがもつ位相シフトの効果についての検証を行った。
成果
１．Circadian variations in muscle strength, darts, Wingate test, and respiratory variables at rest in ultra-short sleep-wake cycle
Abstract
We examined circadian variations in muscle strength, darts, Wingate test, and respiratory variables at rest using the 2-4 h ultra-short sleep-wake protocol. Eight healthy men participated in a 24 h laboratory experiment involving 4 alternating cycles of 2 h sleep and 4 h wakefulness. Performance test (muscle strength, darts and Wingate) and measurement of respiratory variables were conducted at 2 h from uprise and at the time of awakening, respectively. The body temperature rhythm was assessed with the cosinor analysis of rectal temperatures measured throughout the experiment. The data were expressed relative to time of day and circadian phases based on each individual time of body temperature minimum. Wingate performance and respiratory variables (V(・)CO2, V(・)E and RER) generally demonstrated significant variations relative to time of day and circadian phases in parallel with body temperature rhythm. There were no significant variations in muscle strength and V(・)O2. Darts performance was more directly related to subjective fatigue and performance tended to be decreased with increased degree of fatigue. These results emphasize the usefulness of the ultra-short sleep wake-cycle protocol. To assess more elaborate circadian variation in performances, especially accuracy, chronobiological protocols such as ultra-short sleep-wake cycle are required.
２．Changes of the human core body temperature rhythm and sleep structure by 6-hour phase advance treatment under a natural light-dark cycle.
ABSTRACT
Objective
The purposes of this study were to reveal how far the core body temperature rhythm phase advances and the corresponding changes in sleep structure. The extremities of core body temperature rhythm shifts and nocturnal sleep structure changes were examined during 6 days of 6-hour phase advance treatment using bright light and melatonin under the natural light-dark cycle.
Methods
6 healthy males received phase advance treatments with 1 hour bright light exposure after waking, oral melatonin (1.0 mg) administered in the early evening, and advancement of environmental routines intended to advance the onset of the sleep period 1 hour per day. Core body temperature was recorded continuously for 8 days comprising adaptation, baseline, and 6 treatment days. Nighttime sleep quality was evaluated by polysomnography (PSG) on adaptation, baseline, night 3, and night 6.
Results and Conclusion
The core body temperature nadir in each day compared with baseline advanced significantly (p < 0.05). The mean nadir had advanced approximately 4.5 hours from baseline by day 6. The only significant change found in sleep structure was REM sleep duration, which was significantly decreased in day 6 compared with baseline (p< 0.05). Significant negative correlations existed between nadir phase advances and %REM in baseline, day 3, and day 6 recordings. Thus, phase advances greater than 4 hours were possible under natural light-dark condition, although a phase shift of 1 hour per day may be too rapid to maintain normal sleep structure.
３．The Effects of Advancing Circadian Rhythms versus Acute Phase Shift on the Neurobehavioral Functions, Neuromuscular Control and Muscular Strength in the Early Morning
Background: In general, peak athletic performance has been considered to occur during the late afternoon and the early evening hours when the core body temperature is maximum, and to be worse during subjective late night and early morning when core body temperature is minimum. Phase advances occur as the bright light is given after the core body temperature minimum. Athletic games in the early morning or international athletic competitions with transmeridian travel may not be suitable for the optimum performance. To overcome the circadian disturbance, particularly with morning games, phase advance treatment on athletes is required. The effect of phase advance treatment on the morning performance remains unclear. The purposes of this study are 1) to investigate the effects of advancing human circadian rhythms by exposure to bright light versus by acute sleep-wake cycle change on cognitive functions, neuromuscular control, and muscular strength in the early morning, and 2) to assess the effects of holding a new sleep-wake schedule for a few days on cognitive and motor functions.
Design: Six healthy male subjects participated in this study. Following two baseline bed time scheduled from 2200 h to 0600 h, the sleep-wake cycle was advanced 3 hours in the day 3 which sleep episode was scheduled from 1900 h to 0300 h. From the day 4 to the day 7, participants were exposed to bright light for 1 hour after waking. Core body temperature was recorded at one minute intervals by means of a rectal thermistor. Total sleep time, wake after sleep onset and sleep latency, were measured by the activity monitor. Subjective sleepiness and fatigue ratings were performed 5 minutes before scheduled bed time, just after scheduled wake time, and before and after a performance test. The performance test session was conducted at 0800 h in the day 1 (baseline), the day 3 (acute sleep-wake cycle shift), the day 5 (phase advance treatment 1), and the day 7 (phase advance treatment 2). The Test consisted of neurobehavioral assessments, which include the 10-minute Psychomotor Vigilance Task (PVT), Digit Symbol Substitution Test (DSST), and a 4-minute mathematical addition test (ADD), neuromuscular control (Star Excursion Balance Test: SEBT), and muscular strengths including grip strength and back extension. Data were analyzed using a single-factor, repeated-measures ANOVA. When significant effects were found, Bonferroni significant difference test was used for post hoc analysis. Statistical significance was defined as the 95% level of confidence.
Results and Discussions: Compared with that of the day 1 (baseline), the core body temperature nadir from the day 3 through the day 7 significantly advanced (p<0.05). The core body temperature after the day 4 also significantly advanced when compared with that of the day 2 whereas no difference was found between the day 2 and the day 3. These results may indicate that maintaining a new sleep-wake schedule at least 2 days rather than only a day would be preferable to re-entrain the human body temperature rhythm to a 3-hour phase advance life pattern. No significant differences were observed in any sleep parameters and subjective sleepiness and fatigue except for sleepiness before the test session on the day 7 compared with on the day 1. This suggests that acute sleep-wake cycle change for 3 hours does not deteriorate the objective and subjective sleep qualities. Scores of DSST and ADD on the day 3 and during phase advance treatment with bright light exposure were higher than on the day 1, and further improvements were observed during the treatment period compared to on the day 3. These suggest that phase advance treatment or at least maintaining the new schedule for a few days can improve neurobehavioral functions. No statistical change was found in SEBT. It can be considered that there is no circadian rhythmicity in the neuromuscular control. Since there was no difference in grip strength in this study, even though the circadian variation in grip strength with peaking at the late afternoon or early evening exists, this study indicates there is no difference between 0800 h and 3 hours later, 1100 h. Back strength on the day 5 was higher than on the day 1 in this study while strength on the day 3 was not high as on the day 5 indicates a few days were needed to re-entrain to a new sleep-wake schedule. Further studies are essential to confirm the effectiveness of 3-hour phase advance treatment on athletic performance in the early morning.