Purpose of this study was to examine the recovery process of delayed onset muscle soreness, jump performance, force to contact with the ground and lower limbs movement after intensive jump exercise (IJE), and the relationships between muscle soreness, changes of jump performance and lower limbs movement. Nine males who have experience in special jump exercise participated in this study voluntarily. For the measurement, subjective investigation of the muscle soreness, drop jump performance using a 30 cm high box [jump height, contact time and drop jump index (jump height / contact time)], ground reaction force and movements of lower limbs. This measurement was carried out before IJE (Pre), and at 4 hours (P4), 24 hours (P24) and 72 hours (P72) after IJE. Main results are as follows ; at the time of P24 when intense muscle soreness appeared, significant jump height decreases and contact time increases were shown, and the jump index decreased markedly. This decrease of performance correlated to the change of knee and ankle joint movements during the eccentric phase. At P4, for a subject who felt strong muscle soreness, the decrease of jump height and jump index were considerable. At P72, most subjects recovered to the levels of jump height and contact time to the Pre level. The findings reveal that the jump performances are related to the degree of delayed onset muscle soreness.

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While the session-RPE (rating of perceived exertion) method can quantify training volume in athletes, this method is not able to evaluate energy expenditure (EE) during a training session. We developed an RPE-based activity record for assessing EE during athletic training, and we compared its results to those obtained using the flex-heart rate (flex-HR) method. The EE of nine female collegiate endurance runners was assessed by the RPE-based activity record and flex-HR methods during eight days in the normal training season. Subjects were asked to record their RPE in the record at 5-minute intervals, and to wear a HR monitor during training. All subjects also participated in an incremental treadmill exercise test, which was used to determine their RPE-EE and HR-EE regression equations. Although the RPE-based activity record significantly overestimated EE (RPE-activity record, 572 kcal/session; flex-HR method, 499 kcal/session; p = 0.031), it had high validity relative to the flex-HR method (intra-class correlation coefficient, 0.891; 95% confidence interval, 0.845–0.923) and there were no systematic errors in EE estimation between the two methods. Therefore, the RPE-based activity record can be used to assess EE during training in female runners. However, RPE-based activity record might overestimate EE for athletes who have more intermittent activities during training than endurance runners, because RPE takes more time for returning to the resting level than HR when the intensity of activity declines. Further research is needed to verify the validity of the RPE-based activity record for assessing EE during other sporting activities or measurement conditions, and to identify the factors affecting the degree of estimation error associated with this method.

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Although the trunk segment shows well-coordinated movements in concert with the arms and legs during bipedal walking, little is understood about the neural mechanisms controlling the trunk muscles in response to sudden tactile sensations in the foot during walking. This study examined the cutaneous reflexes (CR) to shed light on the neural mechanisms underlying the regulation of the trunk muscles during walking and standing. Eleven healthy men participated in the study. Electromyographic (EMG) activities were recorded in the trapezius (TRAP), erector spinae (ES), and rectus abdominis (RA) muscles. To elicit CR, non-noxious electrical stimulation of the sural nerve at the ipsilateral lateral malleolus was applied during treadmill walking and tonic contraction of the test muscles during standing. During walking, cutaneous nerve stimulation in the foot gave rise to facilitatory CR in all the muscles, and the amplitude of the CR was strongly modulated in a phase-dependent manner. The amplitude of the background EMG and the amplitude of the CR showed a highly significant correlation in all the muscle tested during standing. However, this was true only in the ES during walking. In the RA, the inhibitory CR during standing changed to a facilitatory one during walking. In addition, reflex ratios were significantly larger during walking than standing. These findings suggest that common neural mechanisms in limb muscles could function in the TRAP and RA, however, in the ES disparate neural mechanisms play a crucial role in modulating cutaneous reflexes during walking and standing.

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The purpose of this cross-sectional study is to investigate the difference in physical activity among elderly living in different areas in Japan (“Bunkyo Ward in Tokyo” (Bunkyo) and “Fuchu City in Tokyo” (Fuchu) as urban areas, and “Oyama Town in Shizuoka” (Oyama) as a non-urban area). Participants were 1859 community-dwelling residents aged 65-74 years, randomly selected from the residential registry (response rate: 68.9%). A mail survey using self-administered questionnaires was conducted. Multivariate logistic regression analyses were used to calculate the adjusted odds ratios (ORs) and 95% confidence intervals (95% CI) of various types of physical activity (eg, walking (Walking), going out (Going-out), bicycling (Bicycling), exercise habits (Exercise)), according to residential areas (reference category: Fuchu), stratified by gender, adjusting for socio-demographic variables. There was a significant difference in Going-out (ORs = 0.61 (95% CI: 0.44-0.86) for men, 0.48 (0.33-0.69) for women)), and Bicycling (0.04 (0.03-0.07) for men, 0.04 (0.02-0.07) for women) in Oyama compared to Fuchu. Furthermore, for women, there was a significant difference in Walking (0.56 (0.38-0.81)) and Exercise (0.59 (0.41-0.85)) in Oyama compared to Fuchu. There was a significant difference in Bicycling and Going-out for men in Bunkyo compared to Fuchu, but there was not a significant difference in other items. Low physical activity levels were observed in the elderly in the non-urban area compared to urban areas. The association was stronger in women. Regional difference might need to be taken into account for an effective physical activity intervention.

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This study aimed to elucidate how body composition, force-generating capacity and jump performances are associated with 50-m sprint velocity in circumpubertal boys, in relation to sprint phases and maturation. One hundred thirty four circumpubertal boys were allocated to preadolescent or adolescent group on basis of the height at the peak height velocity of Japanese boys (154 cm) reported in literature: those with body heights over 154 cm as adolescent group and others as preadolescent group. Body composition was determined by bioelectrical impedance analysis. In addition to maximal voluntary isometric knee extension torque, the performances of counter movement jump (CMJ), rebound jump (RJ), standing long jump (SLJ) and standing 5-step jump (SFJ) were also measured. RJ-index was calculated by dividing height by contact time. The time of 50-m sprint was determined at 10-m intervals. Multiple regression analysis showed that in preadolescent boys, SFJ become a predictor for the sprint speed during acceleration phases, and SFJ, RJ-index and CMJ as predictors for the sprint speeds during maximal speed and deceleration phases. In the adolescent boys, age, CMJ, SLJ, and SFJ become a predictor for the sprint speed during acceleration phases, and torque relative to body mass, CMJ and SFJ were selected as predictors for the sprint speeds during maximal speed and deceleration phases. Thus, the current results indicate that force-generating capacity and jumping ability are determinants for sprint performance in circumpubertal boys, but the relative contribution of each of the two factors differs between preadolescent and adolescent stages and among the sprint phases.

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The purpose of the present study was to examine the importance of the agonist muscle activity of the post-impact 30 ms phase during drop jump (DJ) for effective rebound performance by comparing those of sprint runners and swimmers. The eight sprint runners (SPRINT) and twelve swimmers (SWIM) were participated in this study. They performed DJ from a 0.3-m height box with maximal rebound efforts. Electromyograms (EMG) of the lower leg muscles (medial gastrocnemius [MG], soleus [SOL] and tibialis anterior [TA]), and vertical ground reaction force together with kinematic data were measured simultaneously during DJ. In addition, the onsets of fascicle stretching of the MG and SOL muscles were measured by using high-speed ultrasonography (521Hz) during DJ. The onsets of the fascicle stretching of SOL during DJ were not significantly different between SPRINT and SWIM (15 ± 7 ms and 16 ± 6 ms, respectively). During DJ, SPRINT showed onset of the SOL EMG before the ground contact (-26 ± 19 ms). Meanwhile, SWIM showed the onset of the SOL EMG after the ground contact of DJ (16 ± 19 ms). These results suggest that the SOL muscles for SWIM cannot be fully-activated during the braking phase. Consequently, the rate of force development during the braking phase of DJ and subsequently rebound height could be reduced in SWIM.

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This study aimed to examine the effects of an 8-week physical activity program, which mainly comprised home-based bench-stepping exercise training at the intensity of lactate threshold (LT), on mental health (MH), health-related quality of life (HRQOL), and physical fitness in Japanese returnees from China. Thirty Japanese returnees (63 ± 9 y) participated in the exercise program. Another six subjects were enrolled as the control group. The subjects performed 212 ± 57 min of training, and their daily step counts were increased. Aerobic capacity (LT: 4.5 ± 0.8 vs. 5.5 ± 1.1 METs), lower limb strength (30-s chair stand test [CS-30]: 19.1 ± 5.5 vs. 21.3 ± 5.1 times), and sit-and-reach flexibility (sitting-posture body anteflexion: 36.1 ± 9.4 vs. 39.0 ± 8.4 cm) were significantly increased after the intervention compared with before the intervention. Furthermore, MH, as assessed by the total score of the GHQ-28 (3.4 ± 4.4 vs. 0.3 ± 0.8 points), and the mental component score (MCS) of HRQOL, as evaluated by the SF-36v2 (55.1 ± 11.4 vs. 58.5 ± 10.0), were significantly changed in a positive manner. However, a two-way repeated measures ANOVA (group × period) showed significant interactions for LT and MCS (p<0.05), and a tendency for interactions of CS-30 (p=0.063) and the total score of the GHQ-28 (p=0.098). These results indicate that this bench-stepping exercise program could become a useful health support program for improving physical fitness, as well as MH and HRQOL, in Japanese returnees.

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The effects of physical activity (PA) on bone mass gained during growth in Japanese are not well understood. The purpose of this study was to examine whether changes in PA affected bone mass gained by Japanese schoolchildren, as measured by calcaneus quantitative ultrasound (QUS). Three hundred and seven children aged 9–13 years participated in the study and were followed for a 2-year period. The stiffness index (Stiffness) of the calcaneus was measured by QUS, and PA evaluated by a questionnaire. Participants were divided into two groups according to PA: high (≥ 7 hours/week, H) or low (< 7 hours/week, L). Participants were also divided into four groups according to their 2-year change in PA: consistently high (HH), consistently low (LL), changed from high to low (HL), and changed from low to high (LH). Analysis of covariance was used to compare adjusted Stiffness across all four groups. The adjusted 2-year changes in Stiffness ranked in decreasing order among girls: HH (20.8 %), HL (17.6 %), LH (14.3 %), and LL (12.2 %), respectively (trend test, P = 0.027). This trend was not observed among boys. These results suggest that changes in PA significantly affected bone mass gain among peripubertal girls, and that a continuing PA of more than 7 hours a week (approximately ≥ 60 min/day) from a young age is effective in increasing peak bone mass. However, given the limitations of this study, further robust studies which recruit representative samples and consistently employ validated measurement instruments are needed.

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Very few studies have reported an independent association of the physical activity-related indices with the psychological stress reaction. The present study therefore investigated the association of fitness and screentime as one of the indices of sedentary behavior with the four types of psychological stress reactions and the number of days absent from school for 249 children at a local public school and a metropolitan private school while considering confounding factors. No significant difference was observed in the fitness level of both schools; however, the rate of obesity, the screentime and the level of all psychological stress reactions were significantly worse in the public school. Further, significant differences and trends among the groups classified by fitness level were recognized in the rates of participation in after school activities, feeling of powerlessness and days of absence per year. In addition, the odds ratio of the screentime for depressive and anxiety symptoms was 1.004 (95%CI: 1.000-1.007, p=0.039), while the odds of the fitness level for high feeling of powerlessness and more than five days of absence were 1.582 (95%CI: 1.045-2.396, p=0.030) and 1.434 (95%CI: 1.045-2.396, p=0.015), respectively, after adjusting for the school type, differences in lifestyle and participation in after school activities. In conclusion, the fitness level and the screentime were associated with high psychological stress reactions and the days of absence, independent of the above-mentioned adjusting factors among the children in the present study. Prospective and interventional studies to verify these results are needed.

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