The purpose of this study was to determine whether neuromuscular activation is affected by blood lactate concentration (La) and the level of oxygen uptake immediately before a cycling sprint (preVO2). The tests consisted of ten repeated cycling sprints for 10 sec with 35-sec (RCS35) and 350-sec recovery periods (RCS350). Peak power output (PPO) was not significantly changed despite an increase in La concentration up to 12 mmol/L in RCS350. Mean power frequency (MPF) of the power spectrum calculated from a surface electromyogram on the vastus lateralis showed a significantly higher level in RCS350. In RCS35, preVO2 level and La were higher than those in RCS350 in the initial stage of the RCS and in the last half of the RCS, respectively. Thus, neuromuscular activation during exercise with maximal effort is affected by blood lactate concentration and the level of oxygen uptake immediately before exercise, suggesting a cyclic system between muscle recruitment pattern and muscle metabolites.
Anthropometry is simple, cheap, portable and non-invasive method for the assessment of body composition. While the Nagamine and Suzuki body density prediction equation has been frequently used to estimate %BF of Japanese, the equation was developed more than 40 years ago and its applicability to the current Japanese population has not been studied. This study aimed to compare %BF results estimated from anthropometry and dual energy X-ray absorptiometry (DXA) in order to examine applicability of the Nagamine and Suzuki equation. Body composition of 45 Japanese males (age: 24.3±5.5 years, stature: 171.6±5.8 cm, body mass: 62.6±7.1 kg, %BF: 15.7±5.6%) were assessed using whole-body DXA (Hologic® QDR-2000) scan and anthropometry using the protocol of the International Society for the Advancement of Kinanthropometry (ISAK). From anthropometric measurements %BF was calculated using the Nagamine and Suzuki equation. The results showed that the Nagamine and Suzuki equation significantly (p<0.05) underestimated %BF of Japanese males compared to the DXA results. There was a trend towards greater underestimation as the estimated %BF values using DXA increased. New %BF prediction equations were proposed from the DXA and anthropometry results. Application of the proposed equations may assist in more accurate assessment of body fatness in Japanese males living today.
It is well known that moderate exercise is beneficial to health. However, the effects of exercise on subjective symptoms in relation to mood and autonomic nervous function have not yet been fully examined. The purpose of this study was to investigate the effects of daily walking on subjective symptoms as well as on mood and autonomic nervous function in people who take no medication but have some general physical complaints. We assessed their symptoms by the Cornell Medical Index (CMI), and mood states by a profile of mood states (POMS) and a frontal alpha laterality ratio. Autonomic nervous function was evaluated by a supine rest basal level, reactivity to orthostatic challenge (physiological stimulus) and to a self-programmed videogame (psychophysiological stimulus) of heart rate (HR), heart rate variability (HRV), baroreflex sensitivity and blood pressure (BP). Repeated measures analysis of variance showed no significant group (control and walking group) ×time (pre- and post- walking period) interaction of CMI scores. In contrast, the A-H sub-scale (anger and hostility) of POMS and basal HR significantly decreased after a 4-week walking period in a walking group compared to a control group. Negative mood score of POMS reduced, and basal high-frequency component of HRV and reactivity to orthostatic challenge of baroreflex sensitivity increased marginally significantly compared to the control group. Multiple regression analysis revealed a significant contribution of A-H to the physical score of CMI, which showed a marginally significant reduction after the experimental period in the walking group. These results suggest that daily walking can improve mood states and shift autonomic balance to parasympathetic predominance, and may consequently contribute to the reduction of subjective symptoms.
This study evaluates the physical and physiological ability of selected soccer players of Kunimi High School in Nagasaki Prefecture, Japan. The Kunimi team is famous for its intensive training, and had won the championship of the All Japan High School Soccer Tournament six times by 2003. We measured physique, body composition, and maximal oxygen uptake of 72 members aged between 16 and 18 years old between 1986 and 1994. They consisted of 66 outfield players (12 forward players, 23 midfielders, 31 defenders) and 6 goalkeepers. Body density was measured by the under-water weighing method, and Brozek's equation was applied to calculate percentage body fat (%Fat, %), fat-free mass (FFM, kg), FFM/height (FFM/Ht, kg·m−1), and FFM index (FFM/Ht3, kg·m−3). The following results were obtained: 1. The average of 66 outfield players was 172.7 cm of height, 64.6 kg of weight, 54.0 cm of girth of thigh, and 90.0 cm of girth of hip, 9.3% of %Fat, 58.6 kg of FFM, 33.9 kg·m−1 of FFM/Ht and 113.8 kg·m−3 of FFM index. The mean vital capacity was 4.25 L and total lung capacity was 5.58 L. The mean maximal ventilation was 138.7 L·min−1, VO2max was 3.95 L·min−1, and VO2max/Wt was 61.4 ml·kg−1·min−1. 2. Goalkeepers were taller and heavier than outfielders, and had a smaller mean value of VO2max/Wt than outfielders (p<0.01). 3. For 23 out of the 72 players measured twice with an interval of about one year, FFM increased and %Fat reduced significantly, while VEmax, VO2max and VO2max/Wt did not change. Kunimi players of the present study had as large a VO2max/Wt as local players, and a similar or slightly smaller VO2max/Wt than national-level players. They had similar %Fat and a similar VO2max/Wt with professional soccer players in England (Davis et al., 1992) while they had much smaller physiques.
Daily monitoring of heart rates is important in health management. Many researchers have analysed heart rate variability by using the resting heart rate because such an analysis can facilitate the early discovery of a variety of illnesses and health conditions. Some problems that arise in measuring heart rate are the feeling of confinement. Therefore, we required a system that could measure the resting heart rate in a static position in such a way that the subject is completely unaware that the measurement is being recorded. We propose a non-restrictive measurement method that uses only an acceleration sensor placed inside a down quilt. This method is easy for home use. The acceleration sensor was placed inside the quilt such that it was positioned opposite to the left-hand side of the subject's chest. Six healthy subjects were requested to lie in the supine position and were covered with the quilt equipped with the acceleration sensor. Mechanical vibrations that resulted from heart activity were carried through the quilt to the acceleration sensor. As a result, periodic vibrations were measured successfully, and in the six subjects, these vibrations were proved to be highly correlated with the R wave of electrocardiograms. The same results were obtained even when the subjects were lying in the left lateral position. The results indicated that our new method, which used an acceleration sensor placed inside a down quilt, was simple and could be used to measure the resting heart rate in a lying position.