Humans perceive their body posture, size, and position in space even when they do not look at their body. The ability to perceive the body correctly is essential to move accurately in space. The purpose of this review is to introduce the reader to the latest views on the role of peripheral afferent signals in the generation and alteration of perception of the body. First, the contribution of proprioceptive and cutaneous signals to perception of the body is introduced. Common methods to investigate these signals are muscle vibration, skin stretch, or electrical stimulation. These methods provide evidence that the perception of the body is flexible. Second, effects of multisensory integration on perception of the body are described. The combination of visual, tactile, proprioceptive, and auditory signals alter the perception of the body, suggesting that multiple sensory signals contribute to perception of the body. Third, the distortion of perception of the body after the loss of sensory signals is reviewed. Anesthesia or amputation of limbs, as well as experimentally-induced disintegration of sensory signals drastically alter the perception of the body. Fourth, neural mechanisms underlying the generation, or alteration, of perception of the body is described. The premotor and parietal cortices play a key role in perception of the body, as they are involved in multisensory integration. In the final section of the review, implications of the ways sensory information shapes perception of our body are discussed for athletic performance.
The health values of exercise and eating are separately established as two independent pillars for human life. However, a substantial amount of evidence shows the physiological crosstalk by which exercise might be associated with hunger and satiety, as regulated by gut hormones. A single bout of exercise tends to suppress the blood levels of orexigenic acylated ghrelin (AG) and to increase the levels of anorectic hormones like peptide YY (PYY) and glucagon-like peptide-1 (GLP-1). It was reported that, while sustained physical activity increases the drive to eat in the fasting state, this seems to be compensated by an improved satiety response to a meal through changes in the gut hormone systems. A few studies reported exercise-induced reductions in the neural responses to food-related cues in higher brain center networks involved in the attentional, emotional and cognitive functions. The present review introduces the latest research on the effects of various types of exercise on the neuroendocrine networks related to hunger, satiety, appetite, and responses to food-related cues, suggesting the physiological rationale for the linkage between exercise and eating in humans. Next, the possibilities of the brain science of exercise and eating for improvements in modern human health in various generational groups are discussed.
Effective behaviors optimized for various situations are enabled by various sensory information. How does the brain deal simultaneously with information from different sensory systems? Investigation of multisensory processing began from neuroanatomical and neurophysiological studies at the level of single neurons. Accumulation of knowledge concerning neurons and progress in recording techniques of human brain activity have led to a massive expansion in recent neuroscientific studies using various combinations of brain activity recording and cognitive tasks. In this paper, we briefly review recent neuroscientific studies related to multisensory convergence and interaction, focusing on electrophysiological and imaging studies in humans.
Skeletal muscle stem cells, known as satellite cells, participate in postnatal skeletal muscle growth, regeneration, and hypertrophy. They are quiescent in the resting state, but are activated after muscle injury, and subsequently replicate and fuse into existing myofibers. The behavior of satellite cells during muscle regeneration is regulated by extrinsic factors, such as the extracellular matrix, mechanical stimuli, and soluble factors. Myokines, muscle-derived secretory factors, are important regulators of satellite cell activation, proliferation, and differentiation. It is well known that muscle injury induces the release of various growth factors from myofibers, and these growth factors affect satellite cells. It has recently been shown that myokines secreted from myofibers without cell damage also regulate satellite cell functions. Here, we summarize myokines with known roles in the regulation of satellite cells and the mechanism underlying this regulatory process.
Sports and physical activity provide multiple social and health benefits to participants, but may also increase the risk of developing musculoskeletal pain and injuries, especially in skeletally immature adolescents. This review outlines the 1) measurement and prevalence of musculoskeletal pain in adolescents, 2) dose-response relationship between the organized sports activity and musculoskeletal pain, 3) high risk population, based on our previously published epidemiological studies in Japan, and finally, 4) prevention strategy and its evaluation. In our school-based cohort study in Unnan, Shimane, a total of 2403 adolescents aged 12 to 18 years responded to two serial surveys, conducted 1 year apart. The prevalence of overall pain was 27.4% (lower limbs: 15.4%, upper limbs: 9.5%, and lower back: 8.5%). Sports activity had a clear linear association with musculoskeletal pain prevalence and risk. The more the adolescents played sports, the more likely they were to have pain or develop pain. Each 1 hour/week of additional sports activity time was associated with a 3% higher probability of having or developing pain. Some population groups were at higher risk of musculoskeletal pain, such as overweight adolescents and regular players with fewer teammates. To optimize the safety and benefits of organized sports activity for adolescents, prevention of musculoskeletal pain should be an important consideration. More observational and intervention studies with quality designs and development of a national surveillance system for (youth) acute and chronic sports injuries are needed in Japan.
During exercise, levels of several hormones are acutely increased in the blood. We previously reported that pre-exercise ingestion of a specific combination of amino acids (arginine, alanine, and phenylalanine; A-mix) increases fat mobilization and ketone body synthesis by increasing secretion of adrenalin and glucagon in healthy active young men. Herein, we sought to determine whether this acute hormone response could be induced upon administration of A-mix combined with exercise in patients with obesity during periods of low-intensity exercise. We performed a randomized crossover study of eleven middle-aged men with obesity without regular exercise habits, administered either A-mix (3 g/dose) or a placebo (3 g of dextrin/dose). Thirty minutes after ingestion, each subject subsequently performed workload tests on a cycle ergometer at 40% of peak oxygen consumption for 1 h. Following oral intake of A-mix, the concentration of plasma ketone bodies was significantly increased during exercise. This was accompanied by a significant increase in the area under the concentration-time curve for glucagon. Taken together, these results indicate that pre-exercise ingestion of the A-mix supplement significantly accelerated hepatic ketone body synthesis via stimulation of glucagon secretion during exercise in men with obesity.
This study aimed to examine the effect of different methods of active recovery (AR) after high-intensity exercise on exercise performance, determined with the Yo-Yo Intermittent Recovery Test level 2 (Yo-Yo IR2) in soccer referees. Using a crossover design, fourteen male soccer referees completed three trials. After resting for 10 min, participants ran approximately 495 meters (m) at 80% of maximum heart rate (HRmax) and, ran approximately 165 m at 90% of HRmax. This was followed by 15 min of passive recovery (control), 15 min of running at 130 beats/min (continuous AR), or 15 min of intermittent AR consisting of alternating 2.5 min intervals of passive recovery and running at 130 beats/min, repeated for 15 min (intermittent AR). Finally, participants performed the Yo-Yo IR2. Blood lactate and salivary cortisol concentrations were determined immediately after the rest, high-intensity exercise, recovery intervention and Yo-Yo IR2 periods. The Profile of Mood States (POMS) Questionnaire was measured after rest and Yo-Yo IR2. Yo-Yo IR2 performance was significantly higher in the intermittent AR trial than in the control trial. Blood lactate concentrations were significantly lower in the continuous and intermittent AR trials than in the control trial after the recovery intervention. No significant between-trial differences were observed in salivary cortisol concentrations. The fatigue score using the POMS increased significantly during the control and continuous AR trials, but not during the intermittent AR trial. In conclusion, AR with intermittent exercise after high-intensity exercise increases Yo-Yo IR2 performance compared to passive recovery.
The purpose of this study was to describe the incidence, severity, mechanism, and intrinsic risk factors for knee injuries in Japanese collegiate rugby union players. Initially, 119 rugby union players from one university club were registered in this prospective cohort study. The occurrence of knee injuries was recorded by a team doctor and athletic trainers during the 2009-2012 playing seasons. The number of knee injuries recorded during these four seasons was 64. The incidence of knee injuries was significantly higher during matches (10.5 injuries/1000 player hours [ph]) than that during training (0.3 injuries/1000 ph). The most common match injury was the medial collateral ligament injury (4.4 injuries/1000 ph). The greatest severity and burden were observed for anterior cruciate ligament injuries (severity: 182.5 days, burden: 310.3 days/1000 ph). A majority of knee injuries were sustained during ruck/maul (26.6%) and step/cutting (20.3%). In addition, a history of injury (odds ratio [OR]: 3.3, 95% confidence interval [CI]: 1.3-8.4, p = 0.01) and rugby experience (<10 years, OR: 2.4, 95% CI: 1.1-5.7, p = 0.03) were considered as intrinsic risk factors for knee injuries. Although the total incidence of knee injuries in collegiate rugby union players was similar to that at a professional level, knee ligament injuries had a higher incidence and severity among college players. Injuries frequently occurred in ruck/maul for forward (FW) players and in step/cutting and being tackled position for back (BK) players. In this game, the risk of knee injury is high, and it varies for each field position, so preventive measures according to field position characteristics are necessary.
The purpose of this study was to compare the lumbar lordotic angle (LL) and pelvic tilt angle (PT) in the simple modified Thomas test (SMTT) position with LL and PT in the Thomas test (TT) position. Participants (n = 20) were between the ages of 23 and 39 and had no history of trauma. LL and PT were measured by X-ray radiographs under three conditions: the SMTT position, TT position, and supine position. At the same time, the distance between the examination table and the popliteal fossa was measured with a ruler. These measurements were compared by one-way analysis of variance. LL (14.6 ± 6.7 degrees [°]) in the SMTT position was significantly lower than in the TT position (18.6 ± 6.6 °) (p < 0.01). PT (33.5 ± 7.6 °) in the SMTT position was significantly higher than in the TT position (31.3 ± 6.9 °) (p < 0.05). The distance between the examination table and the popliteal fossa in the SMTT position (100 ± 37.7 mm) was significantly higher than in the TT position (73.5 ± 27.4 mm) (p < 0.01). These results suggest that LL and PT in the SMTT position are easier to assess than those in the TT position.
Running economy (RE) at an intensity above the lactate threshold (LT) is reported to be the most important aerobic capacity for estimating 1,500-m running performance. The reason that the RE at intensity better reflects the energy metabolism during a 1,500-m run, is that it is performed above the LT intensity running. This study clarified the relationship between an 800-m run, which is performed above the LT intensity, and aerobic capacities, including the RE measured at intensities below and above the LT. This study included 12 well-trained male middle-distance runners (800-m velocity: 25.5 ± 0.5 km·h−1, LT intensity: 79.7 ± 5.1% maximal oxygen uptake [VO2max]). Both the RE of below and above the LT intensity were calculated at 65%VO2max (RE65) and 90%VO2max (RE90). The 800-m velocity was not related to the VO2max or the LT intensity (r = -0.16 and -0.10, respectively). This velocity correlated with both RE90 and RE65, with the correlation coefficient being higher for RE90 (r = -0.80 vs -0.75). Furthermore, the coefficient of determination for the 800-m velocity determined from VO2max, LT intensity and RE90 was higher than that determined from VO2max, LT intensity and RE65 (R2 = 0.522 vs 0.428, P = 0.03 vs 0.06). Based on these results, we concluded that the RE at an intensity above the LT might be better than other aerobic capacities for estimating the 800-m running performance, and more than 50% of this performance can be explained by VO2max, LT intensity and RE at an intensity above the LT.
The maximal accumulated oxygen deficit (MAOD), which is the gold standard for anaerobic energy metabolism capacity, requires multiple tests for evaluation that impose a heavy load on subjects. The maximal accumulated blood lactate (ΔbLa) concentration is also a measure of anaerobic energy metabolism capacity, and is related to the accumulated oxygen deficit (AOD). Thus, AOD has been estimated by using ΔbLa (3.0 mLO2·kg−1·mM−1), but it is unclear if this coefficient is suitable for measurement of supramaximal running of athletes. The purpose of this study was to clarify the estimated expression of AOD by using ΔbLa from the relationship between MAOD and ΔbLa during supramaximal running in middle-distance runners. Eleven male middle-distance runners (800m running velocity: 425.3 ± 7.3 m·min−1) took part in this study. They performed three running tests (maximal, submaximal and supramaximal running test) to evaluate MAOD and ΔbLa. MAOD and ΔbLa were 56.6 ± 6.0 mLO2·kg−1 and 9.9 ± 1.1 mmol·L−1, respectively. We observed a significant positive relationship between MAOD and ΔbLa (r = 0.73); the regression line equation was y = 3.58x + 18.6. Results showed that the AOD per mM of the ΔbLa of athletes was 3.58 mLO2·kg−1, which was 19% higher than the conventional coefficient value.