Skeletal muscle is an essential tissue that regulates glucose metabolism and locomotive ability. Therefore, gaining skeletal muscle mass is important for maintaining or improving health as well as athletic sport performance. Over the past decade, resistance exercise has been shown to be the most effective method for gaining muscle mass. Acute resistance exercise increases muscle protein anabolism, and repeated training induces protein accumulation and muscle hypertrophy. Similarly, protein anabolism by nutrition intake, particularly protein and amino acid ingestion, is important for regulating skeletal muscle mass. Moreover, recent studies have indicated that a combination of resistance exercise and nutrition intake augments the anabolic effect more than exercise and/or nutrition intake alone. In this review, we discuss the mechanism underlying protein anabolism based on exercise and nutrition intake, as well as recommendations for optimizing protein anabolism by each stimulus based on the latest findings. Finally, recent evidence related to the cumulative effect of resistance exercise in combination with nutritional supplements on muscle protein metabolism is discussed.
Most organisms display various periodicities. Periodicity has been observed in humans in association with sleep, body temperature and hormone secretion. The molecular mechanisms involved are being elucidated by the investigation of clock genes in mammals. The relationship between biological rhythms and disease is also being studied. For example, myocardial infarction occurs more frequently in the morning, and disruption of biological rhythm is associated with obesity and diabetes. Some drugs have different medicinal effects depending on the time of dosing. Drug therapy known as chronotherapy, that takes into account the diurnal rhythm found in a given target disease, is being administered in some cases. Moreover, physiological responses and metabolism differ with time. Therefore, understanding the mechanisms underlying biological rhythms could enable the safe and effective performance of physical activity, in addition to potential medical applications. This review article outlines current understandings of biological rhythmicity and explores the relationship between biological rhythms and exercise, training, and sports.
Accurate assessments of sedentary behavior are critically important to monitor the proportion of prolonged sedentary behavior, to investigate causal relationships with health outcomes, and to test the effectiveness of interventions aimed at reducing sedentary behaviors. The purpose of this review was to provide an overview of assessments of sedentary behavior using wearable devices, and to briefly discuss the future directions of this field. Sedentary behavior is defined as any waking activity characterized by energy expenditure ≤ 1.5 metabolic equivalents and a sitting or reclining posture. Globally accepted wearable devices to assess sedentary behavior are ActiGraph (developed in the United States of America) and activPAL (developed in Scotland). The ActiGraph, worn at the waist, classifies sedentary behavior based on its unique metric of ‘counts’ less than 100 per minute. The activPAL is attached to a participant’s thigh, and classifies sedentary behavior using an inclinometer with a proprietary algorithm. In Japan, Omron’s Active style Pro is the most widely used device to measure sedentary behavior. A systematic review on sedentary behavior measurements in Japan found that almost all studies adopted this device. A data reduction approach is a key process to obtain consistent summary statistics of sedentary behavior. To accomplish this, seven R packages have been developed, mainly for ActiGraph and activPAL. Unfortunately, none of these can integrate data from Japanese devices; although a macro program for processing data from Active style Pro has been developed. Use of activity recognition techniques and multi-sensor devices may reduce measurement errors, and provide contextual information on sedentary behavior. Other challenges include standardization and harmonization of measurement protocols. Tackling these challenges may facilitate international comparisons in sedentary behavior and eventually study integrations.
Grip strength is a well-known indicator of muscle strength. The trajectories of grip strength with increasing age refer to the aging and development process of muscle strength over one’s life span. The levels of muscle strength needed to perform activities of daily living or to prevent older people from developing disabilities are serious geriatric issues. Grip strength has been shown to decline with aging and to be a predictor of the development of geriatric problems, which suggests the lifelong management of grip strength has great potential for the promotion of healthy aging. The focus of this short review was to examine grip strength as an indicator of geriatric issues and to clarify the role of grip strength in relation to healthy aging.
Heat stress treatment is a classic physical therapy, which is employed in the orthopedic field. In the field of physical fitness/sports science, morphological changes of skeletal muscle by heat stress have been well studied. In recent years, energy metabolic adaptations by heat stress have also been actively studied. In this review, we provide an overview of recent findings on heat stress-induced mitochondrial adaptations in skeletal muscles, and further discuss our unpublished data and recent findings in related research fields. First, we summarized heat stress-induced positive regulation of mitochondrial content and its underlying molecular mechanisms from perspectives of mitochondrial biogenesis and degradation. Consequently, we reviewed beneficial effects of heat stress on mitochondrial health in disused and aged muscles, focusing on mitochondrial stress response at the organelle level (mitochondrial selective autophagy; mitophagy) and molecular level (mitochondrial unfolded protein response). Finally, we overviewed future directions to better understand heat stress-induced mitochondrial adaptations in skeletal muscle.
Renalase is a recently discovered flavin adenine dinucleotide (FAD)-dependent soluble monoamine oxidase. It is expressed principally in the kidney, but its expression in the heart, brain, and skeletal muscle has also been confirmed. It is thought that renalase is involved in cardiac function and control of systemic blood pressure primarily by metabolizing circulating catecholamines. Animal experiments have suggested the possibility that exercise is involved in renalase secretion, but this has not been confirmed in human studies. The principal aim of the present study was to investigate the relationship between exercise and renalase concentration in humans. Subjects were young men who were continuously training to run distances of 10-20 km; the total distance that was run in the present study was 30 km. Measurements were performed at four points (before running and after running 10 km, 20 km, and 30 km). The results of one-way analysis of variance examining repeated measurements of serum renalase concentration revealed significant differences (P = 0.007). A significant negative correlation between serum renalase concentration and estimated glomerular filtration rate, which indicates renal function, calculated using serum cystatin C concentration was noted. A significant positive correlation between serum renalase concentration and oxidative stress was observed in the period before exercise and after running 20 km. The present study verified the exercise-induced increase in serum renalase concentration in amateur runners who were continuously training.
Muscle strengthening activity and high muscle strength were reported to protect against the development of type 2 diabetes in middle age. On the other hand, the reported prevalence of type 2 diabetes is higher in former top-level power sports athletes compared to healthy non-athlete men. High muscle strength may be a risk factor for type 2 diabetes. However, it is not clear whether high muscle strength can predict the future development of type 2 diabetes. This study examined the relationship between muscle strength at a young age and the future development of type 2 diabetes in former Japanese college athletes by a historical cohort study. Subjects were male alumni who graduated from the Physical Education School of Juntendo University. Hand-grip strength at college age (1971-1991) and type 2 diabetes history, as determined by follow-up questionnaires (2007-2009, and 2011), were collected. Relationships between hand-grip strength and new cases of type 2 diabetes were analyzed by Cox proportional hazards models and adjusted for relative risks. Data of hand-grip strength and medical history of 617 subjects were collected. The median follow-up period was 27 years, and 29 men developed type 2 diabetes. There was no relationship between incidence of type 2 diabetes and muscle strength level after adjustment for potential risk factors. The adjusted hazard ratios (HRs) and 95% confidence intervals of the low, medium, and high muscle strength categories were 1.00 (reference), 1.12 (0.46-2.70) and 0.70 (0.25-1.92), respectively. We concluded that muscle strength at a young age does not predict the future development of type 2 diabetes in Japanese male athletes.
Cycling is a way for older adults to be physically active and remain healthy. This descriptive epidemiological study investigated the role of sociodemographic, biological, behavioral, and psychological correlates associated with cycling among community-dwelling older adults in Japan. This cross-sectional study, conducted in 2010, included 1,938 community-dwelling older adults aged 65 to 74 years, from three cities in Japan: Bunkyo City (urban area) and Fuchu City (suburban area) in Tokyo, and Oyama City in Shizuoka (rural area). Participants were randomly selected from resident registries and a questionnaire was mailed to each one (response rate of 75.7%). All data was self-reported, including cycling time. Multivariable logistic regression analysis was used to calculate the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for cycling. The proportion of men and women who cycled was 30.1% and 28.3%, respectively. Cycling was strongly associated with residential area: in men, Fuchu (suburban) (ORs = 3.15, 95% CIs = 2.20-4.52), Oyama (rural) (0.14, 0.08-0.25); in women, Fuchu (suburban) (4.15, 2.80-6.16), Oyama (rural) (0.21, 0.11-0.40), compared to Bunkyo (urban). Moreover, cycling was inversely associated with being underweight (0.26, 0.08-0.80) in men; for women, it was inversely associated with living alone (0.51, 0.29-0.90) and with not working (0.56, 0.38-0.84), and positively associated with not driving often (2.81, 1.47-5.40), and with not possessing a driver’s license (2.16, 1.23-3.79). The prevalence of cycling among older adults is relatively high in Japan. However, it varies greatly depending on residential area. Differences in residential areas may be taken into account to promote effective strategies for cycling.
The physiological changes of normal ageing result in diminished input from visual, proprioceptive and vestibular systems, with reduction in the strength of the lower extremities and balance control among the elderly. This systematic review determined the effect of square-stepping exercise (SSE) on balance in older adults. PubMed, CINAHL (EBSCO), Embase, Scopus, the Cochrane Library and the Web of Science database were searched using specific keywords for randomized controlled trials and pseudo-randomized controlled trials published 2006-2016. Two reviewers independently extracted data, which included specific details about study methods, populations, interventions, outcome measures and results. Eight studies were assessed. The meta-analysis of this study indicates that there was a large significant effect on balance [ES 0.94; confidence interval (CI), 0.36 to 1.52]. The strongest effect was found on the BBS [ES 1.83; confidence interval (CI), 0.52 to 3.15]. However, no statistically significant differences were observed between SSE and control groups regarding single leg balance with eyes closed and the Timed Up and Go (TUG) Test. Conclusions, SSE was effective for improving short-term balance in older adults and reduced their risk of falling. High-quality studies with large sample size, including more balance related fall and adherence outcomes measured over a longer period are necessary for further study.
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