Sudden cardiac arrest (SCA) and sudden cardiac death (SCD) during exercise are rare but devastating for a patient and family. The objectives of this review are to provide both school and sport-events’ personnel with an overview of the types of preventions, such as screening tests and cardiac emergency response plans, describe the recommended screening tests and cardiac emergency response plans during exercise, and describe current concerns and challenges in the prevention of SCA or SCD. A literature review was performed. No intervention study was identified. Thus, based on findings from observational studies, the types of prevention against SCA and SCD have been reviewed, and the recommendations for prevention were discussed. The 12-Element AHA Recommendations for Preparticipation Cardiovascular Screening of Competitive Athletes was strongly recommended as a screening test. The 12-lead ECG remained controversial for use as a preparticipation program. Genetic testing was not appropriate for prevention. In addition, concerns and challenges for future studies were discussed. An observational study with rigorous methodology and analysis is feasible and could provide a good understanding as a controlled trial.

View full abstract

Physical activity guidelines have been published by governments to increase physical activity at a national level. Such guidelines commonly include behavior change techniques. To allow guidelines to contribute to physical activity promotion, it is necessary to enhance people’s awareness of these physical activity guidelines. The present article reviews trends regarding studies on the prevalence and socio-demographic correlates of the awareness of physical activity guidelines, and on the relationship between the awareness of guidelines and physical activity behavior change. Compared with the awareness of physical activity guidelines in Canada (20.7-37.3%) and the United States (32.0-36.1%), awareness of physical activity guidelines was less prevalent in Japan (6.1-12.3%). More intensive campaigns promoting physical activity guidelines are necessary in Japan. Regardless of country, those with higher socioeconomic status (higher educational background or household income level) were more likely to be aware of physical activity guidelines. Promotion campaigns targeting those with low socioeconomic status are needed to reduce inequalities in the awareness level of such guidelines. Positive relationships between guideline awareness and physical activity levels have been reported in cross-sectional studies. However, longitudinal studies have not revealed any such positive relationships. Moreover, intervention studies have failed to show any effects of the guidelines on physical activity behavior change. Thus, the awareness of physical activity guidelines appears to have limited influence on physical activity behavior change. Unlike physical activity guidelines, the promotion of Japanese dietary guidelines has been successful in increasing healthy eating behaviors in Japanese adults.

View full abstract

The kidneys play an important role in regulating acid-base and water-electrolyte balance disturbances induced by exercise. In sports medicine, research on renal function during exercise in healthy individuals and athletes is less common than other areas of study such as the respiratory, circulatory, and neuromuscular systems as well as metabolism, since renal function has no direct effect on athletic performance. In this study, we reviewed previous research results obtained in our laboratory and other studies as follows: 1) effects of exercise intensity on renal plasma flow and glomerular filtration rate; 2) effects of exercise intensity on plasma hormone responses and urinary excretion of water and electrolytes; 3) effects of aging on renal function following exhaustive exercise; 4) mechanisms underlying exercise-induced diuresis in healthy volunteers; 5) mechanisms underlying exercise-induced proteinuria (EIP) in healthy volunteers; and 6) effects of exercise combined with angiotensin-converting enzyme (ACE) inhibitor (ACE-I) on the progression of diabetic nephropathy (DN) in obese diabetic model rats. The number of obese diabetes patients is increasing in advanced countries, and the number of hemodialysis (HD) patients per capita in Japan is the highest worldwide. Approximately 42% of patients with DN undergo HD treatment every year. However, regular exercise has not been positively recommended for patients with nephropathy despite being an essential clinical approach for patients with diabetes. Moreover, the ideal exercise regimen for patients with diabetes complicated by nephropathy has not been investigated much. Therefore, a future study should investigate exercise therapy for patients with DN.

View full abstract

Tools are often compared to a part of our own “body”. Since the end of the 20th century, neuroscientists and psychologists have accumulated evidence suggesting that the “tool as a part of the body” is not just a metaphor, but is a fact in the brain. In the introduction of this article, we review a neurophysiological study on the monkey brain that achieved a breakthrough in this area of research. Subsequently, we review studies in humans. In the first section, we explain the psychophysical studies that suggest the perceptual assimilation of tools and hands and neuroimaging reports regarding the neural correlates of perceptual tool-hand assimilation. In the second section, we describe the spatial action capability with tools or extracorporeal objects based on behavioral studies regarding locomotion, such as load-carriage and wheelchair-use. Based on these findings, we discuss current and future research issues regarding the tool-body interaction in the context of neural mechanisms and applications.

View full abstract

This paper reviews the existing literature about muscle hypertrophy resulting from various types of training to document the significance of mechanical and metabolic stresses, and to challenge the conventional ideas of achieving hypertrophy that exclusively rely on high-load resistance training. Low-load resistance training can induce comparable hypertrophy to that of high-load resistance training when each bout or set is performed until lifting failure. This is attributable to the greater exercise volume and metabolic stress achieved with low-load exercise at lifting failure, which, however, results in a prolonged exercise bout. Endurance exercises (walking and cycling) at moderate intensity are also capable of eliciting muscle hypertrophy, but at much slower rates (months rather than weeks) in limited muscle or age groups. Blood flow restriction (BFR) in working muscles, however, accelerates the development of metabolic fatigue, alleviating the time consuming issue associated with low-load or endurance training. These alternative training methods, however, cannot completely replace conventional high-load resistance training, which provides superior strength gain as well as performance improvement even for trained individuals. The alternative approaches, therefore, may be considered for those who are less enthusiastic or under certain medical conditions, or who have limited or no access to proper equipment. However, people should be aware that low-load resistance training or endurance training entails substantial effort and/or discomfort at lifting failure or with BFR. Understanding the advantages and disadvantages of each method will help in assigning the most suitable training program for each client’s goals and needs.

View full abstract

Exercise improves the performance of the cardiovascular system, striated muscle, and bones, and reduces obesity. Exercise provides for mechanical forces, which include fluid flow and stretching. These mechanical stimuli alter gene expression, which induces the physiological and pathological response in the organs and cells. However, the molecular mechanism underlying the conversion of mechanical stress into gene expression remains largely unknown. Recently, it has been reported that the mechanical stimuli alter the localization of the transcriptional co-activators MRTF (myocardin-related transcription factor) and YAP (Yes-associated protein)/TAZ (transcriptional co-activator with PDZ-binding motif) through actin remodeling. Since MRTF and YAP/TAZ are retained in the cytoplasm in a monomeric G (globular)-actin-dependent manner, actin polymerization promotes the translocation of MRTF and YAP/TAZ to the nucleus, and regulates the expression of several genes. The Rho family small GTPase member Rho and its effector, Rho-kinase (Rho-associated kinase), are critical regulators of actin remodeling. Rho/Rho-kinase suppresses the severing of actin through LIMK (LIM-kinase) and cofilin phosphorylation, thus enhancing actin polymerization. Mechanical stimuli induce actin polymerization through the Rho/Rho-kinase-LIMK-cofilin pathway. The Rho/Rho-kinase signaling pathway regulates gene expression and cell lineage by controlling the actin-dependent localization of MRTF and YAP/TAZ in response to mechanical stress. In this review, we focus on the molecular mechanism by which Rho/Rho-kinase controls gene expression in response to mechanical stimuli.

View full abstract

Low back pain (LBP) is a common musculoskeletal disorder that affects the general and athletic populations. Intervertebral disc degeneration (IDD) is one of the causes of LBP and a current topic in the orthopedic and sports medicine fields. The correlation between IDD and LBP seems controversial. In Part I of this review article, we examine the etiology and nature of intervertebral disc degeneration in terms of classification and definitions of lumbar IDD, prevalence of lumbar IDD, and possible risk factors for lumbar IDD. In Part II, we compare IDD and LBP in general and athletic populations.

View full abstract

Muscle mass and strength decline with age. When severe, the loss is called sarcopenia. Sarcopenia is drawing attention worldwide, especially in highly aged societies, as a disease that should be treated. At present, we have limited tools to combat sarcopenia (e.g. resistance training and nutritional intervention), but accumulating knowledge of the molecular and cellular mechanisms of sarcopenia is accelerating the development of pharmacological therapies for sarcopenia. Because sarcopenia is a complicated pathological condition caused and modified by many aging-related factors, such as inactivity, loss of motor neurons, poor nutrition, decline of anabolic hormones, chronic inflammation, oxidative stress, impaired stem cell function, and comorbidity, the proposed target molecules or pathways for pharmacological intervention are diverse. Here we review recent progress in drug development with emphasis on small-molecule compound-based therapies and review the literature to identify new therapeutic targets to prevent, delay, or reverse sarcopenia.

View full abstract

The variable effects of mechanical stimuli induced by exercise on the human body are becoming better understood. Additionally, the indispensable effect of constant gravity on the human body to construct and maintain living organisms is known from observed muscle and bone regression induced by long-term recumbency or visits to gravity-free environments, such as space. Based on reactions of the body, cells faced with various inputs largely depend on gene expression, biochemical processes, or both. Thus, it is easy to imagine that physical input can be converted into a chemical process. The conversion process that changes physical forces (mechanical stimuli) into chemical reactions in a cell is called mechanotransduction. A growing number of studies examining mechanotransduction have led to a new phase in the understanding of exercise-induced effects on organisms.

View full abstract

The number of patients exhibiting metabolic disorders has been pandemically increasing. Physical exercise is widely applied as an ideal therapeutic and preventive way against such metabolic diseases as diabetes due to its high potency of metabolic regulation. It evokes marked facilitation of glucose and lipid metabolism in contracting skeletal muscle. Recent investigations have suggested that 5’AMP-activated protein kinase (AMPK) should be a key molecule in contraction-caused metabolic changes. AMPK is activated in response to the rise in the AMP/ATP ratio following muscle contraction. The activated AMPK suppresses anabolic pathways, but increases catabolic ones to compensate for the ATP shortage. The various metabolic results of AMPK activation are similar to those in contracting skeletal muscle. However, some recent reports using genetically AMPK-disrupted animals reported that AMPK does not necessarily mediate metabolic control by muscle contraction, suggesting the significance of AMPK-independent metabolic pathways. Genetically manipulated animals without molecules of critical significance such as AMPK will tend to acquire compensatory mechanisms. Thus, another approach will be of great help to further understand the role of such key molecules. Thanks to the recent development of analytic systems, it is getting easier to obtain comprehensive information on metabolites. This metabolomics technology has been applied in studies on physical fitness and exercise little by little, providing us with novel findings; although it is not yet popular. Recent results of metabolomic studies in the field of physical exercise, including our investigation demonstrating metabolomic significance of AMPK in contracting skeletal muscle, will be introduced in this review.

View full abstract

The worldwide pandemic of childhood obesity is now recognized as a serious public health concern. Several recent studies have indicated that childhood obesity is inversely associated with academic achievement, suggesting that maintaining a healthy weight likely be important for cognitive development. However, evidence regarding such an association between childhood obesity and cognitive function is still scarce, and the findings remain controversial. Accordingly, my colleagues and I examined the association between childhood obesity and behavioral and event-related brain potential measures of higher-order cognitive functions (i.e., executive control), which are thought to be closely associated with academic achievement. This short review describes these studies. Our main findings indicate that childhood obesity is negatively associated with inhibitory control and action monitoring, which are key aspects of executive control.

View full abstract

Human locomotion is flexible in meeting the requirements of given environmental or task demands. Hence, in everyday life, we can walk, run, and skip in environmental surroundings that vary from hour to hour and even from second to second. In making such flexible adjustments, a sense of “adaptability” attained by the central nervous system plays an important role. In the literature, adaptation studies focusing on locomotion have attracted a great deal of attention in recent years for their potential application to the designing of gait training programs, and as a useful method for revealing the specific mechanisms underlying human locomotion. In this review article, to address how locomotor adaptation is related to social locomotion, the authors introduce knowledge accumulated in recent decades, particularly that related to two different types of locomotor adaptation studies: first, studies that address the general features of locomotor adaptation including underlying neural mechanisms, and second, those that use experimental paradigms of locomotor adaptation to reveal the context-dependency of locomotion. It should be noted that, although knowledge of locomotor adaptation has been increasing, the field is still largely unexplored, and further intensive research in the future is necessary.

View full abstract

Sarcopenia, a degenerative loss of skeletal muscle mass and strength, impacts daily life among the elderly. Because few cohort studies have examined muscle mass, muscular strength, physical performance, and probable confounding factors in detail, the prevalence of sarcopenia among the elderly in Japan is unclear. In this review, we examine the prevalence of sarcopenia based on the criteria of the Asian Working Group for Sarcopenia (AWGS) using a large-scale cohort of randomly selected community-dwelling elderly in Japan. Participants included 949 elderly (479 men and 470 women) aged 65-91 years who participated in the seventh wave examination of the National Institute for Longevity Sciences - Longitudinal Study of Aging between July 2010 and July 2012. The prevalence of low muscle mass was 43.2% in men and 20.2% in women. The prevalence of low muscle strength was 10.0% in men and 21.5% in women, and the prevalence of low physical performance was 5.4% in men and 9.2% in women. The prevalence of sarcopenia based on a diagnosis of low muscle mass, low muscle strength, and low physical performance was 9.6% in men and 7.7% in women. Elderly who were diagnosed with sarcopenia included 1,320,000 men and 1,400,000 women. These data could be of great help to clinicians and healthcare professionals and contribute to the development of prevention and treatment strategies for sarcopenia in Japan.

View full abstract

In order to investigate factors that contribute to eccentric contraction (ECC)-induced loss of tetanic force, Ca²⁺ uptake, Ca²⁺ release, and Ca²⁺-ATPase activity of the sarcoplasmic reticulum (SR) and sarcolemmal Na⁺-K⁺-ATPase activity were examined in rat fast-twitch skeletal muscles that underwent in situ ECC or isometric contraction (ISC) for up to 500 repetitions. The tetanic force at 60 Hz was more depressed in ECC-treated muscles than in ISC-treated muscles. SR Ca²⁺-ATPase activity displayed biphasic changes in response to ECC; after a temporary increase (up to 200 ECC repetitions), the activity decreased. With ECC, SR Ca²⁺ release rate and Na⁺-K⁺-ATPase activity decreased during the first 100 repetitions and remained almost constant thereafter. In contrast, the investigated variables (Ca²⁺-ATPase activity, Ca²⁺ release rate, and Na⁺-K⁺-ATPase activity) were unaltered in ISC-treated muscles. These results indicate that a more pronounced reduction in force output in ECC-treated muscles than in ISC-treated muscles might be attributable, at least in part, to impaired function of the SR Ca²⁺ release channel and/or Na⁺-K⁺-ATPase.

View full abstract

The physiological mechanisms underlying the increases observed in glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) plasma levels with exercise currently remain unknown. Previous studies reported that increases in plasma GLP-1 and PYY concentrations were mediated by a neural pathway, regardless of exercise. Therefore, we investigated the neural regulation of GLP-1 and PYY secretion during exercise in rats using a hindlimb muscle contraction model. Hindlimb muscle contraction was induced by electrically stimulating the sciatic nerve for 20 min (5 V, 5 Hz). A fasting arterial blood sample (Baseline) was taken. Rats were subjected to 20 min of hindlimb muscle contraction in vivo, and blood samples were collected at the end of the hindlimb muscle contraction protocol. Although GLP-1 and PYY levels were significantly increased after hindlimb muscle contraction (P < 0.001, respectively), no significant differences were observed in GLP-1 or PYY levels between sham and vagotomy trials. On the other hand, GLP-1 and PYY levels after hindlimb muscle contraction were significantly lower in the sciatic nerve deafferentation trial than in the sham trial (P < 0.01, respectively). These results indicate that the increases observed in GLP-1 and PYY plasma levels with exercise were mediated by the activation of skeletal muscle-derived afferent neurons, and not by mechanisms through the neural pathway of the vagus nerve.

View full abstract

Medial tibial stress syndrome (MTSS) is one of the most common causes of exercise-induced lower leg pain in running athletes. The purpose of this study was to compare plantar flexor activation changes in response to different strike patterns during barefoot and shod running in subjects with and without MTSS. The changes were assessed by observing motion characteristics derived from mechanical factors. The 15 collegiate soccer players who volunteered to participate were divided into two groups (7 MTSS, 8 non-MTSS). Three-dimensional marker positions were recorded with a 12-camera motion capture system (Vicon) operating at 250 Hz while the subjects ran along a runway at 3.3 m/s. Each subject completed the running with and without shoes, and different strike patterns as the forefoot strike pattern (FFS) and rearfoot strike pattern (RFS) were collected. Plantar flexor activation was investigated by software for interactive musculoskeletal modeling (SIMM) based on how the activation ratio changed from 0 to 1 at landing. Compared to controls, the MTSS group had higher tendency muscle activity of the plantar flexors that involved the peroneal muscle during first half of stance (p <0.05). For the stance phase of running, the MTSS group had greater muscle activity during plantar flexion in running with the FFS pattern than running with the RFS pattern (p <0.05). These results suggest that subjects with MTSS have higher activity of the plantar flexors during running, especially with the FFS pattern, which suggests greater stress on soft tissues of the tibial portion and a tendency to develop MTSS.

View full abstract