The Journal of Physical Fitness and Sports Medicine Vol. 6(2017) No. 4

Dementia is recognized as one of the major formidable public health challenges in modern aging societies. Among the several subtypes of dementia, Alzheimer’s disease (AD) is the most frequent, probably accounting for 40-50% of total dementia cases. Recent findings from prospective cohort studies suggest that impairment, found in certain physical performance measures, precedes the clinical diagnosis of AD. The main aim of this review paper is to provide a brief summary of recent findings regarding the associations between middle- to late-life physical performance measures and incident AD and total dementia including AD. This paper also aims to discuss the potential mechanisms underlying the prospective associations between physical performance and incident AD. The reviewed findings suggest that poor baseline status in physical performance measures, including gait performance, muscle strength, balance, aerobic performance, and composite physical performance, is associated with greater risk for the subsequent incidence of AD. Preclinical pathologies leading to AD and physical fitness are named as part of plausible factors underlying the prospective association between physical performance and incident AD. It is also speculated that the prospective association is mostly non-causal, where physical performance measures probably serve as “early markers” of the future incidence of AD. Further studies are expected to establish solid evidence of the prospective association, to clarify the whole picture of the mechanisms underlying the association, and to explore the practical application of physical performance measures in attempts to identify individuals at a higher risk of AD before or early in the disease.

More than 80 years ago, McCay and colleagues first reported that limiting the amount of food provided to experimental animals (i.e. calorie restriction or CR) prolongs their lifespan and suppresses the onset and progression of various age-related diseases. Today, CR remains the most reliable method of delaying aging in experimental animals, and research into its underlying molecular mechanisms is ongoing. CR has been reported to have anti-aging and life-extension effects on primates, with progress being made toward applications for humans. Studies on mechanisms underlying the onset and prevention of lifestyle-related diseases such as diabetes have elucidated the cellular signaling pathways that regulate energy metabolism, and commonalities have been discovered between the targets of existing diabetes drugs and the signaling pathways affected by CR. This finding has led to research into the discovery of drugs that have the anti-aging effects of CR in the absence of food intake limitations, namely CR mimetics (CRM). Several drugs have been reported to extend the lifespan of experimental organisms, which may thus have the potential to also extend human lifespan. In this article, we outline and compare those drugs that have been reported to date and discuss the possibility of taurine as a CRM, which is a topic of our ongoing research.

Lipids are the major components of cells and, in addition to being involved in cell signaling, play a major role in the skeletal muscles. Lipids comprise a large number of molecular species with their different fatty acid compositions, and it is hard to visualize their spatial localization to identify muscle-fiber-specific lipid dynamics. In this short review, we present a molecular imaging technology, matrix-assisted laser desorption/ionization mass spectrometry imaging, capable of imaging small metabolites including lipids. This technology has the potential to reveal the lipid dynamics that occur during muscle contraction and/or disease status.

Since the 1990’s, creatine has become one of the most popular supplements in the world for the purpose of increasing skeletal muscle creatine, increasing skeletal muscle mass, and improving the amount of exercise training. The first patient with brain creatine deficiency was reported around the year 2000, and this patient’s severe clinical symptoms - such as impairment of brain function - drove researchers to start focusing more on the brain and related studies. Both in vitro and in vivo studies have shown creatine in the body to cover a wide range of roles including bioenergetic, anabolic, bone remodeling, anti-oxidant, anti-apoptotic, anti-excitotoxic and neuroprotective. In this short review, we introduce recent findings on the effects of creatine supplementation on brain function closely related to mental health, which directly influences the quality of life of elderly people.

Blood pressure increases transiently during exercise in proportion to exercise intensity as a response to the increased demand for blood flow to the muscles. However, in addition to exercise intensity, many factors, including age and arterial stiffness, affect blood pressure during exercise. Aerobic exercises such as walking and cycling and resistance exercises such as lifting objects and climbing stairs are part of daily life activities. Therefore, exaggerated blood pressure responses to exercise increase the risk of cardiovascular disease. In this paper, the effects of habitual exercise on blood pressure during aerobic and resistance exercise are reviewed.

Inner ocular circulation consists of choroidal and retinal circulation. The inner ocular blood flow nourishes the retina, which plays an important role in vision. It had been thought that inner ocular circulation kept its blood flow constant against circulatory challenges during exercise. Recent studies, however, have revealed that inner ocular blood flow changes during exercise, and that retinal and choroidal circulations show different responses depending on the manner of exercise. This review provides an overview of the responses in inner ocular blood flow to exercise and its relevant factors.

Storage of excessive energy as triglycerides is a fundamental function of adipose tissue. Adipose tissue also secrets a number of hormones termed “adipocytokines” or “adipokines” in response to the systemic nutritional status, thereby constituting a feedback mechanism of metabolic homeostasis. In this regard, adipose tissue senses systemic nutritional conditions and regulates systemic metabolic homeostasis. During the past decade, there has been remarkable progress in the molecular mechanism underlying obesity-induced adipose tissue dysfunction. Accumulating evidence has suggested that a variety of stromal cells induce adipose tissue remodeling, which impairs adipose tissue function such as lipid storage and adipocytokine production, thereby leading to systemic metabolic derangements. Namely, chronic inflammation provides a molecular basis underlying obesity-induced adipose tissue dysfunction. In contrast, nutritional deprivation or malnutrition results in immune dysfunction, at least partly, through adipocytokine dysregulation. Thus, adipose tissue links nutritional conditions and inflammatory responses.

Medial elbow injuries lead to significant performance decrement in baseball. Repetitive throwing alters mechanical physiology. Some of such changes can increase the risk of medial elbow injuries. However, in young baseball players with medial elbow injuries, these changes have not been fully investigated. Thus, the purpose of this study was to investigate the mechanical physiological changes in young baseball players with medial elbow injuries. Side-to-side differences in (1) range of motion (ROM) of shoulder external rotation (ER)/internal rotation (IR), elbow flexion/extension, forearm supination/pronation, trunk rotation, and hip ER/IR; (2) strength of middle trapezius, lower trapezius (LT), and supraspinatus muscles, and shoulder ER/IR; and (3) medial elbow laxity were measured. Side-to-side differences were significant (p < 0.05). ROM of shoulder ER/IR, elbow flexion/extension, forearm pronation, and hip IR on the throwing side were significantly decreased compared to the non-throwing side. Trunk rotation in the direction of the throwing side was significantly decreased compared to the non-throwing side. LT and shoulder IR strength on the throwing side were significantly greater, while shoulder ER strength on the throwing side was significantly weaker than the non-throwing side. Medial elbow joint space of the throwing side was significantly wider than the non-throwing side. In other measurements, no significant differences were observed between the throwing and non-throwing side. According to our findings, young baseball players with medial elbow injuries experience many side-to-side differences in mechanical physiology. The most interesting finding was that younger players with medial elbow injuries displayed decreased shoulder ER ROM, versus an increase reported in many previous studies.

The aim of this study is to understand the head impact during actual collisions between American football players from Japanese universities. The subjects of this study were 23 players who belonged to T university in the Kantoh Collegiate American Football Association Division 2. We used a Vector Mouthguard (i1 Biometrics Inc.) equipped with 6 degrees of freedom (DOF) to measure the head linear acceleration (LA) and rotational acceleration (RA) as well as the head injury criterion (HIC), impact location, and number of impacts during collisions. The average number of collisions per player during a practice and during a game was 14.3 and 15.7, respectively. In terms of positions, the ratio (1:1.3) of total number of impacts for backs to linemen in Japan is lower than that (1:3) in the USA. Both during the games and practices, the range of 10 g < X ≤ 15 g in the average peak LA values was the most frequent, and the distributions were largely skewed toward low values (p < 0.05). The medians during the games and practices were 16.77 g and 15.87 g, respectively. The number of collisions during practices in Japan was significantly higher than that in the USA. Particularly, linemen undergo more head collisions than those of backs. Another common factor is that the impact of head collision during a game is significantly higher than that during a practice. However, data on Japanese university players is limited, and further data collection should be done before determining an accurate estimate of the practical concussion risk threshold.

The purpose of this study was to apply a high-power laser blood flowmeter and laser oxygenation monitor to investigate 1) changes during a single isometric contraction and 2) changes after repeated contractions in blood flow (BF), blood volume (THb), and oxygen saturation (StO₂) in the human Achilles tendon in vivo. Subjects (n = 17) performed isometric contractions at 10%, 30%, and 50% of the maximum voluntary contraction (MVC) for 1 min. Subjects (n = 10) also performed five sets of 50 repetitions at 70% of MVC for 1 second (s), and remained relaxed for 20 min. During isometric contractions at all torque levels, BF decreased significantly from resting level regardless of torque level, whereas THb during contractions tended to decrease with increases in torque level. After repeated contractions, BF, THb, and StO₂ were higher during the recovery period than resting level. These results show that 1) BF in the tendon was already interrupted during 10% of MVC to the same degree as that during 50% of MVC, whereas THb during contractions slightly decreased with increases in the torque level and 2) blood circulation (BF, THb, and StO₂) within the tendon was facilitated further after repeated contractions.

The purpose of this study was to investigate postural stability and lower leg muscular activity in male collegiate soccer players with functional ankle instability (FAI), during a diagonal landing. Twenty-two male collegiate soccer players were divided into an FAI group (n = 11) and healthy control group (n = 11). Muscle reaction times for sudden ankle inversion were measured to evaluate neuromuscular control in the peroneus longus (PL), peroneus brevis (PB), tibialis anterior (TA), gastrocnemius lateral head (GL), and gastrocnemius medial head (GM). Time to anteroposterior stabilization (TTSAP), time to mediolateral stabilization (TTSML), and activity of these muscles during a diagonal single-leg landing was measured. Reaction times in the peroneus muscles were delayed in the FAI group, compared to the control group (PL: P < 0.01, PB: P = 0.02). TTSML was increased in the FAI group, compared to the control group (P = 0.02). Muscular activity of PL, PB, and TA were reduced in the FAI group, compared to controls, during a diagonal single-leg landing (PL: P < 0.05, from 87 ms pre-initial contact [pre-IC] to 108 ms post-initial contact [post-IC], PB: P < 0.05, from 180 ms pre-IC to 123 ms post-IC, TA: P < 0.05, from 65 ms to 203 ms post-IC). Male collegiate soccer players with FAI had increased TTSML and reduced muscle activity in PL, PB, and TA during diagonal single-leg landing. It is important for clinicians to assess the postural stability and function of the lower leg muscle activity, during rehabilitation after ankle sprains.

The purpose of this study was to investigate the tracking of clustered metabolic syndrome (MetS) risk factor taking into account fatness and aerobic fitness from childhood to adolescence in Japanese children. This cohort study included 113 participants (47 boys and 66 girls) who were measured for MetS risk factors at 10 years and 13 years of age. Clustered MetS risk factors (MetS risk score) were calculated from the total gender-specific values (z-scores) of the following five parameters: waist to height ratio (W/H), predicted VO_2peak (_pVO_2peak), triglycerides, high density lipoprotein cholesterol, and mean arterial pressure. The tracking coefficient of MetS risk score from childhood to adolescence was 0.647 (p < 0.001). Correlation coefficients of MetS risk scores (without W/H) between 10 and 13 years of age in the high W/H group (r = 0.713, p < 0.001) were higher than those in the low W/H group (r = 0.402, p < 0.01) In addition, correlation coefficients of MetS risk scores (without _pVO_2peak) between 10 and 13 years of age in the low _pVO_2peak (r = 0.630, p < 0.001) were higher than those in the high _pVO_2peak (r = 0.452, p < 0.01). In conclusion, we found that MetS risk was stable from childhood to adolescence in Japanese children. Furthermore, our results show that both fatness and fitness are crucial for tracking MetS risk.

Recent studies have suggested that the amounts of both moderate to vigorous physical activity and sedentary behavior affect the incidence of type 2 diabetes. Recommendations regarding frequency of aerobic exercise training for persons with type 2 diabetes are to not allow more than 2 consecutive days without aerobic physical activity. This study reanalyzed the data from a Risk Factor Intervention Trial in Japan to examine whether a lack of participation in the exercise program on weekends lessened the benefit of the exercise intervention in hyperglycemia. Thirty-two participants with fasting serum glucose above 126 mg/dl at baseline or with a diagnosis of type 2 diabetes were selected from the original dataset. They had joined an aerobic exercise program at a fitness club for 8 weeks, and serum glucose was measured before and after the intervention. Participants who exercised once or more per week on the weekends (Saturday and/or Sunday) along with their weekday routine showed a significant decrease in serum glucose; and changes in serum glucose were smaller in those who participated less often. Adjustment for baseline serum glucose, undergoing diagnosis, total exercise time and changes in energy intake and body weight did not alter this result. It was shown that in exercise interventions for people with hyperglycemia, recommendations on the maximum sedentary interval, in addition to the minimum duration of exercise, should be considered.