Fumiaki Hanzawa

Alternating day- and night-game schedules may alter athletes’ daily behavioral patterns without time-zone travel. This study aimed to characterize the game day time lag (GDL) and within-player sleep–wake differences across day- and night-game schedules, as well as compare sleep–wake patterns, breakfast frequency, and perceived condition between schedule exposure groups. This cross-sectional study included 53 Japanese professional baseball players: 16 exposed to day- and night-game schedules (DN group) and 37 exposed only to day games (D group). Sleep–wake timing, meal frequency, and perceived condition were assessed using MCTQ-based items, self-reporting, and eight 100 mm visual analog scales. The GDL was defined as the absolute difference in self-reported midsleep between day- and night-game schedules for each player. The mean GDL in the DN group was 2.2 ± 0.5 h (95% CI: 1.9, 2.4 h). Within the DN group, sleep timing was later for night-game than day-game schedules, whereas sleep duration did not differ. Exploratory comparisons showed later sleep timing, lower breakfast frequency, and lower sleep satisfaction in the DN group than in the D group. The schedule exposure completely overlapped with the team status, limiting interpretation of these differences. These findings suggest the importance of considering differences in sleep timing related to the competition schedule when providing conditioning support to professional athletes.

Physical inactivity as well as breakfast skipping is known as risk factor for various metabolic diseases, such as obesity and type 2 diabetes. We have previously reported that a breakfast skipping model, in which the timing of feeding is delayed, induces abnormal lipid metabolism by altering the circadian rhythm of lipid metabolism-related genes in rats. The purpose of this study was to elucidate the synergistic effect of physical inactivity and breakfast skipping on lipid metabolism. We adopted sciatic neurectomized rats as physically inactive models, because we confirmed that the rats mildly decreased their spontaneous locomotor activity compared to sham-operated rats. And then the physically inactive model rats were fed a mild high-fat diet during zeitgeber time (ZT) 12-0 in the control group and ZT16-0 in the breakfast skipping group for 11 days. Body weight gain and total food intake were similar in both groups. Breakfast skipping induced a significant visceral fat accumulation, which was not observed in our previous breakfast skipping or physically inactive studies. The mRNA levels of clock and lipogenesis-related genes were altered by breakfast skipping in the liver and epididymal adipose tissue, and serum insulin level was altered by breakfast skipping. These results suggest that physical inactivity and breakfast skipping synergistically induces drastic visceral fat accumulation due to the alteration of circadian clock and lipid metabolism in the liver and adipose tissue. Therefore, regular feeding timing plays an important role in the health of a sedentary modern society.