Aizu Naoki

Abstract <p>Motor control is affected by subjective muscle fatigue and attention to the body (body-specific attention). Although voluntary hand movements immediately alter spatial attention, it is unclear whether these voluntary movements also alter body-specific attention to the hand. We aimed to determine whether voluntary hand movements and subjective muscle fatigue immediately affect body-specific attention to the hand. Nineteen healthy adults participated in this study. Body-specific attention to the left hand and subjective muscle fatigue were assessed before and after participants repeatedly moved their left hand to the palmar and dorsal sides. In the visual detection task measuring body-specific attention, participants responded rapidly to a light appearing on a real hand and a dummy hand. Body-specific attention was calculated by subtracting the reaction time of the real hand from that of the dummy hand. To assess subjective muscle fatigue, participants answered a question on an 11-point scale. Changes in body-specific attention were categorized into two groups: with and without muscle fatigue (p &lt; 0.05). In the group without muscle fatigue, body-specific attention was higher after the movements than before (p &lt; 0.05). Additionally, as muscle fatigue increased after the movements, body-specific attention decreased (r = − 0.568, p &lt; 0.05). Our results showed that voluntary hand movements increased body-specific attention to the hand without subjective muscle fatigue, but decreased it with fatigue. These findings suggest that subjective muscle fatigue affects body-specific attention and consequently makes motor control more difficult. Our findings may provide new strategies and interpretations for rehabilitation therapy.</p>

INTRODUCTION: Exercise has been recommended to suppress or prevent cognitive decline. Aerobic exercise (AE) may suppress cognitive decline via the fibronectin type III domain-containing protein 5 (FNDC5)/irisin/brain-derived neurotrophic factor (BDNF) pathway, and resistance training (RT) has a preventive effect on cognitive decline. However, the underlying mechanism remains unclear. This study verified the differences in the effects of AE and RT in suppressing and preventing cognitive decline based on the FNDC5/irisin/BDNF pathway. METHODS: We divided senescence-accelerated mouse-prone 8 into three groups: control (CON), AE, and RT and evaluated their memory during exercise intervention through a novel object recognition (NOR) task. We quantified FNDC5/irisin, mBDNF, and TrkB in the hippocampus using enzyme-linked immunosorbent assay and FNDC5 in skeletal muscle using Western blotting (WB). RESULTS: Behavioral analysis using NOR showed that values for both AE and RT were significantly greater than those for CON. WB analysis showed that the peripheral FNDC5 expression in the skeletal muscle was increased in AE. The expression levels of FNDC5/irisin and mBDNF in the hippocampus were significantly increased in both AE and RT compared with that in CON but that if TrkB was increased only in AE. CONCLUSION: No significant difference was observed between AE and RT in the inhibitory effect on age-related cognitive decline, and both groups were effective. The FNDC5/Irisin/BDNF pathway, which was the focus of this experiment, may be specific to AE. The mechanism that suppresses cognitive decline may differ depending on the type of exercise.