Sex Differences Of Non-Exercise Activity Thermogenesis In Free-Living Collegiate Athletes

Non-exercise activity thermogenesis (NEAT) in athletes is reported to be 20%-50% of daily energy expenditure, with a large variability. It is known to be affected by various factors such as occupation, sex, and age, but few studies have reported these in free-living athletes, and no studies have focused on the sex differences in NEAT. PURPOSE: To determine the sex differences in the volume and activity intensity of NEAT in free-living college athletes. METHODS: NEAT was defined as the activity during waking hours, excluding sport-specific training, warm-up, and games. This cross-sectional study included highly trained Japanese collegiate male athletes (n = 21; age: 19 ± 1 years) and female athletes (n = 10; age: 19 ± 1 years) from the same university. The participants wore the tri-axial accelerometer for seven days, except during sleeping and bathing, and NEAT was calculated using the collected metabolic equivalents (METs) data. Physical activity intensity in NEAT was categorized as sedentary, light, moderate, and vigorous. The relative percentage of NEAT for each intensity activity was calculated. RESULTS: NEAT was widely distributed in both sexes (male athletes: 541-1264 kcal/day, female athletes: 329-858 kcal/day). The male athletes exhibited higher NEAT than the female athletes (791 ± 170 kcal/day vs. 594 ± 193 kcal/day, p = 0.007), although there was no significant difference in body weight-adjusted NEAT (male athletes: 711 ± 39 kcal/day, female athletes: 768 ± 69 kcal/day, p = 0.540). The male athletes spent less time in light-intensity activities (168 ± 35 min/day vs. 267 ± 71 min/day, p = 0.002) and more time in vigorous-intensity activities (7 ± 6 min/day vs. 5 ± 9 min/day, p = 0.003). The Male athletes expended more energy on moderate- (44.4 ± 6.4% vs. 32.4 ± 10.7%, p < 0.001) and vigorous-intensity activities (8.3 ± 7.1% vs. 3.3 ± 6.6%, p = 0.011) and less energy in light-intensity activities (31.1 ± 7.0% vs. 48.9 ± 11.7%, p < 0.011) than the female athletes. CONCLUSION: There are no sex-related differences in the volume of activity of NEAT, but there may be differences in the activity intensity.