森 寿仁

PURPOSE: We hypothesized that respiratory muscle endurance training (RMET) in hypoxia induces greater improvements in respiratory muscle endurance with attenuated respiratory muscle metaboreflex and consequent whole-body performance. We evaluated respiratory muscle endurance and cardiovascular response during hyperpnoea and whole-body running performance before and after RMET in normoxia and hypoxia. METHODS: Twenty-one collegiate endurance runners were assigned to control (n = 7), normoxic (n = 7), and hypoxic (n = 7) groups. Before and after the 6 wk of RMET, incremental respiratory endurance test and constant exercise tests were performed. The constant exercise test was performed on a treadmill at 95% of the individual's peak oxygen uptake (V˙O2peak). The RMET was isocapnic hyperpnoea under normoxic and hypoxic conditions (30 min·d). The initial target of minute ventilation during RMET was set to 50% of the individual maximal voluntary ventilation, and the target increased progressively during the 6 wk. Target arterial oxygen saturation in the hypoxic group was set to 90% in the first 2 wk, and thereafter it was set to 80%. RESULTS: Respiratory muscle endurance was increased after RMET in the normoxic and hypoxic groups. The time to exhaustion at 95% V˙O2peak exercise also increased after RMET in the normoxic (10.2 ± 2.4 to 11.2 ± 2.6 min) and hypoxic (11.5 ± 2.6 to 12.6 ± 3.0 min) groups, but not in the control group (9.6 ± 3.2 to 9.4 ± 4.0 min). The magnitude of these changes did not differ between the normoxic and the hypoxic groups (P = 0.84). CONCLUSION: These results suggest that the improvement of respiratory muscle endurance and blunted respiratory muscle metaboreflex could, in part, contribute to improved endurance performance in endurance-trained athletes. However, it is also suggested that there are no additional effects when the RMET is performed in hypoxia.

This study investigated effects of downhill (DR) versus level (LR) running training on various muscular and aerobic performances. Eighteen healthy young males conducted either DR (DR group (DRG), n = 10: -10% slope) or LR (LR group (LRG), n = 8) training at a target heart rate (HR) associated with lactate threshold (LT) for 20 min・session− 1, 3 sessions・week− 1, for 5 weeks. Before and after the interventions, the following variables were measured: knee extension torque (-150, -30, 0, 30, 150°・s− 1), leg extension power (simultaneous hip and knee extension: 0.8 m・s− 1), squat and countermovement jump height, rebound jump index (jump height・contact time− 1), 20-m linear sprint and change-of-direction (Pro-agility and V-cut tests) time, and aerobic capacity (maximal oxygen uptake, energy cost at LT, and velocity at maximal oxygen uptake and LT) on a level surface. Throughout the training sessions, HR during running did not differ between the groups (DRG: 77.7% ± 4.6% vs LRG: 76.4% ± 4.6% of maximal HR average across all sessions), while velocity was significantly higher for DRG (14.5 ± 1.1 vs 12.0 ± 1.9 km・h− 1). After the training, DRG significantly improved knee extension torque at all angular velocities (9%-24%) and change-of-direction time for both tests (2%-3%), with no changes in other parameters. LRG significantly improved maximal oxygen uptake (5%), energy cost at LT (3%), and velocity at maximal oxygen uptake (7%), without changes in others. These results suggest that DR training has a greater potential to improve the knee extension strength and change-of-direction ability, but has little effect on the aerobic capacity, compared with HR-matched LR training.

&nbsp;&nbsp;The main purpose of this study was to investigate anthropometry and body composition in 26 male ultramountain runners who participated in Trans Japan Alps Race 2014, a multi-stage ultramountain running race over 415 km to be covered within 5-8 days. The second purpose was to investigate the changes in skinfold thickness during the race. Before the race, all participants were examined in terms of body weight, BMI, skinfold thickness at 8 sites and estimated percentage body fat. In addition, the finishers (n=14) were re-examined in the post-race period. The main findings are summarized below.<br> 1.&nbsp;&nbsp;The participants had a mean (&plusmn;SD) body weight of 62.3&plusmn;5.1 kg, a BMI of 21.5&plusmn;1.4 kg/m², a sum of 8 skinfold thickness of 57.7&plusmn;15.5 mm, and an estimated percentage body fat of 12.0&plusmn;2.4%. There were no significant differences in any parameters between the finishers and the non-finishers.<br> 2.&nbsp;&nbsp;The sum of 8 skinfold thickness in the finishers was significantly reduced by 11.3% after the race (Pre : 55.0&plusmn;13.6 mm, Post : 48.8&plusmn;12.1 mm), representing a dramatic response in comparison with a previous study that investigated ultramarathon runners in a 100-km ultramarathon race (0.9%).<br>

3000m台の高度で重度の急性高山病(AMS)を発症しやすい登山者2例(A、T)を対象とした低酸素順化トレーニングの効果について検討した。2ヵ月間で4回の低酸素トレーニングを実施した(1泊2日を3回、2泊3日を1回)。Aにおいて、仮眠時のSpO2は、2回目に一旦低下がみられたが、3回目、4回目と上昇する傾向を認めた。これらの値の変化は、仮眠時のAMSスコアの変化とも連動し、「4回目のトレーニング時に著しく体調が良いように感じた」という、観察所見とも一致した。Tでは、登山をした際のAMSの特徴は、行動中に頭痛、めまい、ふらつきを感じることが多く、トレーニング中のAMSスコアをみると、椅座位安静時や仮眠時と比較して、運動時にはやや高値を示していた。トレーニング4回目には運動時のSpO2にも増加を認め、観察所見でも、「4回目には体調が著しく良くなっている」という結果であった。

The purpose of this study was to determine the effects of body mass-based squat training on body composition, muscular strength and motor fitness in adolescent boys. Ninety-four boys (13.7 ± 0.6 yrs, 1.60 ± 0.09 m, 50.2 ± 9.6 kg) participated in this study and were randomly assigned to training (n = 36) or control (n = 58) groups. The training group completed body mass-based squat exercise training (100 reps/day, 45 sessions) for 8 weeks. Body composition and muscle thickness at the thigh anterior were determined by a bioelectrical impedance analyzer and ultrasound apparatus, respectively. Maximal voluntary knee extension strength and sprint velocity were measured using static myometer and non-motorized treadmill, respectively. Jump height was calculated using flight time during jumping, which was measured by a matswitch system. The 8-wk body mass-based squat training significantly decreased percent body fat (4.2%) and significantly increased the lean body mass (2.7%), muscle thickness (3.2%) and strength of the knee extensors (16.0%), compared to control group. The vertical jump height was also significantly improved by 3.4% through the intervention. The current results indicate that body mass-based squat training for 8 weeks is a feasible and effective method for improving body composition and muscular strength of the knee extensors, and jump performance in adolescent boys. Key pointsAn 8-wk body mass-based squat exercise training decreased percent body fat in adolescent boys.The body mass-based squat exercise training increased muscle size and strength capability of the knee extensors in adolescent boys.The squat exercise training improves vertical jump height in adolescent boys.

急性高山病(AMS)を発症しやすい登山者の生理的な特徴を把握するため、国内外の3000m台の登山時に重度のAMS症状を頻繁に示し、登山を継続することが困難となった経験のある3名(男63歳・64歳、女38歳)の生理応答を測定した。測定は急性の低酸素曝露時の応答を評価するHVR試験の他に、亜急性の低酸素曝露として常圧低酸素室内に一定時間滞在させて安静、仮眠、運動時に行った。その結果、HVRは基準値(対照群の平均値)に対して三者三様で、それぞれ-1SDを下回る低値、+1SDを上回る高値、±1SD範囲内で下限に近い値であった。亜急性の低酸素曝露時の動脈血酸素飽和度(SpO2)の応答は、安静時では2名が基準値よりも-1SD以上低値を示し、1名は±1SD以内であった。仮眠時と運動時のSpO2は3名とも-1SD以上低かった。心拍数、分時換気量、平均血圧は個人差が大きく、共通した傾向はなかった。