Carbohydrate is a crucial energy fuel for exercise, and carbohydrate supplementation as peri-exercise has beneficial effects on exercise performance. However, recent studies have indicated the possibility that periodized carbohydrate restriction improves exercise performance. Carbohydrate restriction before exercise increases fatty-acid oxidation (FAO) and alternatively prevents carbohydrate consumption during exercise. This may contribute to the prevention of muscle glycogen depletion during endurance exercise competition. Additionally, acute and chronic studies have shown that peri-exercise carbohydrate restriction enhances molecular and functional adaptation related to FAO. Similarly, exercise training in a low-muscle glycogen state accompanied by carbohydrate restriction was reported to enhance mitochondrial biogenesis and improve FAO capacity, aerobic capacity, and endurance performance in untrained and highly trained subjects. The potential mechanism of these metabolic adaptations may be related to elevated circulating fatty-acid and adrenaline concentration during exercise with carbohydrate restriction and/or a low-muscle glycogen state. In addition, a decrease in muscle glycogen content may trigger signaling pathways related to FAO and mitochondria biogenesis by activating proteins with a glycogen-binding domain. This article reviews the effects of exercise with carbohydrate restriction and/or low-muscle glycogen state on metabolic adaptation and exercise performance and describes the molecular mechanisms and availability.
The state in which physical and mental functions are deteriorated with aging is called frailty, and decrease in muscle mass and muscle strength with aging accompanying deterioration of physical function is called sarcopenia. Frailty and sarcopenia are found in older adults, which is a major obstacle to achieve healthy longevity. Estimation of prevalence and number of patients, as well as elucidation of risk factors in frailty and sarcopenia are important for the prevention of frailty and sarcopenia. The prevalence of frailty determined by criteria based on the method of Fried et al. was 5.2% for men and 20.9% for women in a cohort of randomly selected community-living population, and the estimated number of people with frailty was about 0.77 million men and 2,22 million women among the population aged 65 years and over in Japan. The prevalence of sarcopenia by the Asian Working Group for Sarcopenia (AWGS) criteria was 9.6% for men and 7.7% for women. The number of people aged 65 years and over with sarcopenia in Japan was estimated to be 1.64 million for men and 1.39 million for women. The onset of frailty was related to physique, physical function, cognitive function, depression, and various chronic diseases. Depression and lack of exercise were significant risk factors of sarcopenia. Physical activity, nutrition and control of chronic diseases are required for the prevention of frailty and sarcopenia, and the prevention will be an important issue for health and longevity in Japan.
This study evaluates the pertinent cutoffs of Timed Up and Go (TUG) and Chair Stand (CS) tests for detecting cognitive impairment risk in Japanese elderly. Subjects were community-dwelling adults aged 65 or older (N = 455, 129 men and 326 women). Cognitive function was examined using Urakami’s test for Alzheimer’s disease; physical function was examined by TUG and CS. The maximum score for cognitive function was 15; impairment was defined as 12 or less. Receiver operating characteristic (ROC) analyses were performed to find an appropriate cutoff of TUG and CS for cognitive impairment. Furthermore, the sensitivity and specificity of the combined use of these measures independently distinguishing between subjects with and without a risk for cognitive impairment were determined. Fifty-four subjects (12%) scored as impaired on Urakami’s test. The optimal TUG cutoff for cognitive impairment was 6 seconds and 9 seconds for CS. The combined use of TUG and CS, based on a subject being positive on at least one measure, yielded sensitivity of 78% and specificity of 50%. Area under the ROC curve of TUG and CS were respectively 0.67 and 0.66. When divided into two groups according to the TUG cutoff value, the odds ratio of cognitive impairment in the slower group was 2.1 (95% confidence interval 1.25-3.37). For CS cutoff, the slower-group odds ratio was 3.57 (95% confidence interval 2.20-5.81). For TUG and CS combined, the slower-group odds ratio was 2.11 (95% confidence interval 1.03-4.34). TUG and CS are thus potent predictors for cognitive impairment among elderly adults.
The purpose of this study was to assess the effectiveness of 12 months of walking exercise interventions to improve sleep quality in older adults. One-hundred ninety healthy older adults were divided into a 12 months walking exercise group (n = 120) and a control group (n = 70). Furthermore, to investigate whether the difference in step count changes affected sleep quality, the walking exercise group was sub-divided into a high-walking exercise group (n = 60) and a low-walking exercise group (n = 60) according to the median number of percent change of steps. The main outcome measures were daytime sleepiness (Epworth Sleepiness Scale: ESS) and sleep quality (Pittsburgh Sleep Quality Index: PSQI) questionnaires. The high-walking exercise group showed significant improvements in ESS (p < 0.01), PSQI global score (p < 0.01), subjective sleep quality (p < 0.05), sleep disturbance (p < 0.05) compared to the baseline scores. In the high-walking exercise group, the result of average step counts per day was significantly increased compared to the baseline (p < 0.01). These results suggest that the 12 months walking exercise intervention was an effective approach to improve sleep quality in older adults who maintained the increase in step counts during the intervention period.
Many previous studies have reported that static stretching (SS) may decrease muscle stiffness and compromise muscles’ ability to produce maximal strength. However, the effects of SS at different repetition durations and numbers within a constant total time remain unclear. Therefore, the purpose of this study was to examine whether SS for a constant total time (2 min) with different repetition durations and numbers (e.g., 60 s × 2 times, 30 s × 4 times, and 10 s × 12 times) produces different changes in muscle stiffness and strength. Fifteen healthy males (mean age: 23.3 ± 1.0 years) participated in this study. Muscle stiffness was measured during passive ankle dorsiflexion using dynamometer and ultrasonography. In addition, muscle strength of the plantar flexors was measured using a dynamometer at 0° of plantarflexion with the hip and knee joints fully extended. Muscle stiffness and strength were measured before and immediately after SS. Each experimental protocol was conducted in random order with at least a 1-week interval but no longer than a 2-week interval between testing sessions. The results showed that there were no significant interaction effects on muscle stiffness and strength. However, in all experimental protocols, muscle stiffness and strength immediately decreased after SS. In conclusion, SS for a constant total of 2 min decreases muscle stiffness and strength regardless of repetition durations and numbers of each individual SS.
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