‘Relative age effect’ (RAE) is considered a factor in successful sporting activities. That is, older children in a particular age group are more likely to achieve sporting success than younger ones. Many studies on RAEs have been conducted for the sports systems in North American and European countries. In this article, we elaborate on the RAEs in Japanese athletes of both male and female sports, the association of RAEs with number of years in school and with legal-gambling sports, and give a historical analysis of Japanese baseball. Since 1886, Japan has applied a unique age-grouping for education, which groups students with birthdays from April 1 to March 31 of the following year into the same age category. Therefore, April 1 is the beginning of each ‘new year’, and this specific calendar applies to the education system including elementary, junior high and senior high schools, university (college), as well as to government and private companies. Sports calendars also follow this system, and many professional sports such as baseball, soccer, basketball, and volleyball start the new season in April. Therefore, players born in April, May, and June should have a relative age advantage. We introduce the characteristics and phenomenon of RAEs in Japanese athletes, and discuss several problems that should be addressed in future studies.
Proprioceptive information is provided to the central nervous system by discharges of a large number of primary sensory receptors in the periphery. Studies using single-fiber recordings of sensory afferents have described that various modality of sensory receptors exhibit movement-related discharges. Recent advances in a multi-channel recording technique enable us to consider the contribution of a population of sensory receptors to the encoding of proprioceptive information. Discharges of an ensemble of sensory receptors accurately represent the movement kinematics and trajectory of limbs. Detailed analyses reveal different roles for each modality of sensory receptors in the specific encoding of proprioceptive information from the forelimb among total sensory receptors. Multi-channel recording of sensory receptors affords a new experimental paradigm to explore proprioceptive population coding by sensory receptors.
A muscle capillary network is composed of capillaries and anastomoses, and can be modulated under varying conditions. Although exercise induces growth in the capillary network in healthy individuals, physical deconditioning and diabetes cause regression in the capillary network of skeletal muscle. Vascular endothelial growth factor (VEGF) is a critical factor in maintaining the capillary network in skeletal muscle. In addition, the angiopoietin system, is a second family of essential growth factors, that has been identified. Angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) are important angiogenic factors that bind to their common receptor Tie-2 and assist in vascular development and remodeling. Recent studies have demonstrated the contribution of anti-angiogenic factors in controlling angiogenesis in skeletal muscle. Thrombospondin-1 (TSP-1) was shown to be an angiogenesis inhibitor. A balance between pro- and anti-angiogenic factors tightly modulates capillary regression or growth. A chronic decrease in loading and activity resulted in a regression in the capillary network. We have recently shown that the levels of Ang-1 were lower, while levels of Ang-2 were unaffected in atrophied skeletal muscle. Accordingly, the Ang-2/Ang-1 ratio was higher. In addition, the VEGF/TSP-1 ratio was lower. Thus, capillary regression and growth are associated with complex pro- and anti-angiogenic factors in skeletal muscle. Meanwhile, exercise prevents capillary regression associated with a balance between pro- and anti-angiogenic factors in impaired skeletal muscle. Our study provided clear evidence of reduced oxidative enzyme activity levels and capillary regression in skeletal muscle of diabetes. Therefore, exercise has high potential for preventing capillary regression in impaired muscle.
This article reviews scientific literature on computer-tailored interventions for adults that targeted physical activity and healthy eating. Systematic literature searches were performed using MEDLINE, CINAHL Plus, SPORTDiscus, and the Cochrane Library. Articles that were published in scientific journals were included if they evaluated an intervention for physical activity and healthy eating, or focused on weight loss, and used a randomized design. Thirty-eight articles were identified. Twenty-one (physical activity, 55%) and 22 (food intake, 57.9%) of the 38 studies showed that computer-tailored interventions were more effective than the control. Implications of inconsistency in results and future directions for research are discussed.
Insulin resistance induced by obesity is important in the pathogenesis of metabolic syndrome and type 2 diabetes. On the other hand, recent data suggest that ectopic fat accumulation in muscle and liver induces insulin resistance in these organs, independent of obesity. For example, short-term calorie restriction greatly decreased intrahepatic lipid levels and improved hepatic glucose metabolism in patients with metabolic disease. In addition, short-term aerobic exercise decreased intramyocellular lipid accumulation and improved insulin resistance in skeletal muscle. Similarly, physical inactivity was identified as a risk factor of intramyocellular lipid accumulation during a 3-day high fat diet. Considering the fact that metabolic diseases are frequently observed in lean subjects in East Asian countries, ectopic fat accumulation in insulin target organs may be an important pathogenesis of, as well as a therapeutic target of, metabolic diseases in non-obese subjects. Thus, it may be more appropriate to call fat accumulation in insulin target organs as “intracellular obesity” rather than ectopic fat. Furthermore, it is important to perform additional research to clarify the pathogenesis of metabolic diseases in non-obese subjects.
Major natural disasters can severely affect people’s health. This paper examines the relationship between 3 earthquakes and ambulatory blood pressure monitoring (ABPM). Regarding elevated blood pressure (BP), similar data is evident in all three major earthquakes (Central Italy, China and Japan). The natural disaster spotlighted in this paper is the Great East Japan Earthquake, which occurred in north-east Japan on March 11, 2011 (magnitude 9.0 on the moment magnitude scale [MMS]). During this earthquake, thirteen patients were monitored by ABPM as part of this study, it was noted that participant BP was elevated; but it is worth noting that their home BP did not become elevated until the following day.
This is a brief review of some recent experiments exploring aspects of human limb position sense. It is known that muscle vibration at 80 Hz stimulates muscle spindles to generate a sense of muscle lengthening, representing arm extension for elbow flexors. For the forearm, it was shown in a two-arm position matching task that if the subject was blindfolded or could see their indicator arm made little difference in their ability to indicate the illusion of extension of the reference arm during its vibration. However, when the indicator arm was replaced with a dummy, or the subject used a mirror image of the indicator to achieve a match, the size of the vibration illusion was significantly reduced. It was argued that these two latter conditions represented an arm pointing task rather than a matching task, and this was responsible for signalling a smaller vibration illusion. By means of the techniques of muscle conditioning and of muscle vibration it was shown that it was the difference signal from the two elbow antagonists of each arm that was important, and that the brain compared the difference signals from the two arms to determine the accuracy of arm alignment. It was argued that this mechanism, which relies on the afferent discharges of muscle spindles, could only operate over a limited range of elbow angles. One of the challenges for the future is to define those limits.
This study aimed to examine the effects of walking, a common activity that has previously been reported not to be effective for fall prevention, on fall-related factors among a general population of community-dwelling older adults. A total of 90 men and women, ranging from 65-79 years of age, were randomly allocated into either the walking group (brisk walking) or the balance group (tai chi, balance and strength training) to participate in 12-week supervised and home-based exercise programs. Physical factors (11 items on gait, static/dynamic balance, and strength of the lower extremities), psychological factors (Japanese Falls Efficacy Scale or FES), and daily step counts were assessed. Falls and trips were recorded during the 12-week intervention period. In both groups, significant improvements (P < 0.05) over the 12-week intervention were observed in usual/maximum gait speed, timed up and go, 10-m walk over obstacles, 6-minute walk, functional reach, 30-s chair stand test, and isometric knee extension force. Only the walking group showed significant increases in fall self-efficacy (+3.1 ± 8.0 points) and daily step counts (+3366.4 ± 3212.5 steps/day) (P < 0.05). No significant differences between groups were observed in falls or trips. Our findings suggest that walking among general, community-dwelling older adults was specifically effective in improving fall-related psychological factors and physical activity levels, as well as in improving some fall-related physical factors such as gait, dynamic balance and dynamic strength of the lower extremities, which were also improved by the strength and balance program.
The aim of this study was to clarify the prevalence and distribution of disc degeneration in collegiate rowers and investigate the relationship between disc degeneration progression and low back pain (LBP). In this cross-sectional study, 68 collegiate rowers were evaluated for lumbar disc degeneration using the Pfirrmann classification based on T2-weighted magnetic resonance imaging (MRI). After 2 years, 20 participants underwent follow-up MRI. Injury surveillance to check LBP was conducted between the first examination and follow-up study. The relationship between symptoms and disc degeneration was investigated. Thirty-one (45.6%) rowers had disc degeneration: 48.8% of male rowers and 40.0% of female rowers. After 2 years, disc degeneration progression was observed in 5 (25%) rowers. During the 2 years, 6 rowers reported LBP. In the LBP group, disc degeneration progression was observed in 4 (66.7%) rowers. Significantly more participants in the LBP group than in the non-LBP group (7.1%) (p = 0.014) showed disc degeneration progression. The prevalence of disc degeneration among collegiate rowers was 45.6%, high at the level of the lower lumbar spine. Progression of lumbar disc degeneration was observed in significantly more LBP than non-LBP rowers during the longitudinal study.
Previous studies suggested that taurine (2-aminoethanesulfonic acid) administration enhances glucose uptake, one of the rate-limiting factors for glycogen synthesis. In this study, we investigated the effects of post-exercise taurine administration on glycogen repletion in skeletal muscle in ICR mice. In experiment 1, we orally administered either taurine (0.5 mg/g body weight) solution or physiological saline immediately after treadmill running at 25 m/min for 90 min. The serum free fatty acid (FFA) concentration at 60 min after the exercise was significantly higher in the taurine-treated group compared with the control group (p < 0.05). At 120 min after the exercise, the tibialis anterior muscle glycogen concentration in the taurine-treated group was significantly higher than that in the control group (p < 0.05). In experiment 2, we orally administered either glucose (1 mg/g body weight) solution or glucose solution containing taurine immediately after and at 60 min after the exercise. The area under the curve (AUC) for blood glucose concentration from 0 to 60 min after the exercise was significantly smaller in the taurine-treated group compared with the control group (p < 0.01). Our results show that post-exercise taurine administration enhances glycogen repletion in skeletal muscle. Higher skeletal muscle glycogen concentration by taurine administration may be partly due to the acceleration of glucose uptake. In addition, as the elevation of blood FFA level leads to an increase in fat oxidation, it is possible that a higher serum FFA concentration by taurine treatment is related to the sparing of carbohydrate for glycogen repletion.