Satoshi Nakae

Effects of strenuous exercise on visual perception are independent of visual resolution

Strenuous exercise may have the detrimental effects on visual perception. However, it is unclear whether visual resolution is related to the detrimental effects on visual perception. The purpose of this study was to examine whether the effects of strenuous exercise on visual perception are dependent on visual resolution. Given that visual resolution decreases in the periphery of the visual field, we hypothesized that if visual resolution plays a role in the detrimental effects on visual perception, the detrimental effects may be exaggerated toward the periphery of the visual field. Simple visual reaction time was measured at rest and during cycling at 40% and 75% peak oxygen uptakes (VO(2)). Visual stimuli were randomly presented at 2°, 10°, 30°, and 50° to either the right or left of the midpoint between the eyes with equal probability. RT was fractionated into premotor and motor components (i.e. premotor time and motor time) based on electromyographic recording. The premotor time during exercise at 40% peak VO(2) was not different from that at rest. In contrast, the premotor time during exercise at 75% peak VO(2) was significantly longer than that at rest (p=0.018). The increase in the premotor time was observed irrespective of eccentricity, and the detrimental effects were not exaggerated toward the periphery of the visual field. The motor time was not affected by exercise. The current findings suggest that the detrimental effects of strenuous exercise on visual perception are independent of visual resolution.

Effect of diurnal variations in the carbohydrate and fat composition of meals on postprandial glycemic response in healthy adults: a novel insight for the second-meal phenomenon

Background Meals, particularly carbohydrate intake, determine diurnal blood glucose (BG) excursions. However, the effect of meals with variable carbohydrate content on diurnal BG excursions remains poorly understood, despite routine consumption of meals that vary daily. Objective The aim of this study was to verify our hypothesis that glycemic response is elevated when a meal with a higher carbohydrate content follows a meal with a lower carbohydrate content. Design This was a secondary analysis of a study whose primary endpoint was energy metabolism (e.g., energy expenditure and substrate oxidation). This crossover study was designed to test BG responses to 3 types of meals with different macronutrient contents [regular meals (R), meals with a high-carbohydrate breakfast (CB), and meals with a high-fat breakfast (FB)] using a continuous glucose monitoring system. The R test included 3 meals/d with the same macronutrient composition; the CB test, a high-carbohydrate meal at breakfast, a high-fat meal at lunch, and a high-carbohydrate meal at dinner; and the FB test, a high-fat meal at breakfast, a high-carbohydrate meal at lunch, and a high-carbohydrate meal at dinner. Each test had similar daily macronutrient compositions, except CB and FB had larger variations in carbohydrate content than R. Fourteen healthy young men were tested in random order and underwent whole-body indirect calorimetry. Results Daily peak BG concentrations were higher for the CB (mean ± SD: 143.9 ± 25.3 mg/dL) and FB (140.2 ± 24.8 mg/dL) conditions than for the R condition (127.5 ± 15.7 mg/dL). Postprandial BG peaks after a high-carbohydrate meal were ∼20 mg/dL higher when a previous meal was relatively high-fat than when not high-fat (P < 0.05 for all). A multiple regression analysis indicated that the postprandial glycemic response was negatively associated with the preprandial respiratory quotient. Conclusions Our findings indicate that switching from high-fat to high-carbohydrate meals contributes to larger postprandial BG excursions, along with alterations in prioritization of carbohydrate utilization. This study was registered at the UMIN Clinical Trials Registry as UMIN000028895.