小川 剛司

Abstract We aimed to determine the effects of wearing a cloth face mask on cardiorespiratory response, peak oxygen uptake (Vo₂), respiratory muscle effort, and exercise tolerance during incremental exercise. The study had a randomized crossover design: 11 apparently healthy young men performed the Bruce protocol treadmill test in two conditions, wearing a cloth face mask (CFM) and without CFM (CON), in random order. Minute ventilation and oxygen uptake were measured using a mass spectrometry metabolic analyzer; cardiac output (CO) was measured using an impedance CO monitor; and mouth pressure (P_m) was measured and calculated as an integral P_m to assess respiratory muscle effort. Maximal minute ventilation was 13.4 ± 10.7% lower in the CFM condition than in the CON condition (P < 0.001). The peak Vo₂ (52.4 ± 5.6 and 55.0 ± 5.1 mL/kg/min in CFM and CON, respectively) and CO were not significantly different between the two conditions. However, the integral value of P_m was significantly higher (P = 0.02), and the running time to exhaustion was 2.6 ± 3.2% lower (P = 0.02) in the CFM condition than in the CON condition. Our results suggest that wearing a cloth face mask increased respiratory muscle effort and decreased ventilatory volume in healthy young men; however, Vo₂ remained unchanged. Exercise tolerance also decreased slightly.

Cao, Yinhang, Naoto Fujii, Tomomi Fujimoto, Yin-Feng Lai, Takeshi Ogawa, Tsutomu Hiroyama, Yasushi Enomoto, and Takeshi Nishiyasu. CO2-enriched air inhalation modulates the ventilatory and metabolic responses of endurance runners during incremental running in hypobaric hypoxia. High Alt Med Biol. 23:125-134, 2022. Aim: We measured the effects of breathing CO2-enriched air on ventilatory and metabolic responses during incremental running exercise under moderately hypobairc hypoxic (HH) conditions. Materials and Methods: Ten young male endurance runners [61.4 ± 6.0 ml/(min·kg)] performed incremental running tests under three conditions: (1) normobaric normoxia (NN), (2) HH (2,500 m), and (3) HH with 5% CO2 inhalation (HH+CO2). The test under NN was always performed first, and then, the two remaining tests were completed in random and counterbalanced order. Results: End-tidal CO2 partial pressure (55 ± 3 vs. 35 ± 1 mmHg), peak ventilation (163 ± 14 vs. 152 ± 12 l/min), and peak oxygen uptake [52.3 ± 5.5 vs. 50.5 ± 4.9 ml/(min·kg)] were all higher in the HH+CO2 than HH trial (all p < 0.01), respectively. However, the duration of the incremental test did not differ between HH+CO2 and HH trials. Conclusion: These data suggest that chemoreflex activation by breathing CO2-enriched air stimulates breathing and aerobic metabolism during maximal intensity exercise without affecting exercise performance in male endurance runners under a moderately hypobaric hypoxic environment.

type:Article 本研究は,運動強度や時間,負荷が一定である運動と全力で行う運動の発揮様式の違いによって短時間自転車運動時の機械効率が異なるかを明らかにすることを目的とした.15名の大学陸上競技部に所属し,短距離走および中距離走を専門とする男子大学生が実験に参加した.実験は,事前テストとして,自転車エルゴメーターを用いた漸増負荷運動を行い,最大酸素摂取量(VO2max)および最大下強度における酸素需要量を測定した.別日にそれぞれ,30秒間の全力自転車運動(Wingate test), 120%, 150%, 180%VO2max強度での30秒間の一定負荷運動,および120%VO2max強度での疲労困憊に至るまでの一定負荷運動テストの5つの超最大運動を行った.このとき,酸素摂取量および酸素借を算出し,代謝量に対する仕事量を機械効率として算出した.その結果,3つの強度における一定負荷運動およびWingate testの機械効率には有意な差は見られなかった.しかしながら,疲労困憊までの120%VO2max一定負荷運動時の機械効率は他の運動と比べて有意に低値を示した(p<0.05).以上の結果より,超最大運動での機械効率は,運動継続時間が同じときには運動強度や発揮様式に関わらず一定であるが,運動継続時間に影響を受けることが示唆された. The purpose of this study was to investigate whether the mechanical efficiency (ME) during supra-maximal cycling exercise differs by the difference in exercise intensity, duration and cadence influence. Fifteen college students who belong to a university track and field team performed five supra-maximal exercise tests. The sprint cycling tests were 1) the constant load exhaustive cycling with 120% maximal oxygen uptake (VO2max) pedaling load (MAOD test), the 30- s Wingate test, and three kinds of 30-s sub-maximal sprint cycling with 120, 150, and 180%VO2max pedaling load. The ME was calculated as the amount of work divided by energy supply calculated from VO2 and oxygen deficit. As a result, the ME during the 30-s submaximal sprint cycling test was unchanged regardless of the exercise intensity. It was similar even in the Wingate test, where the power output was not constant. In contrast, the ME of the MAOD test was significantly lower than other sprint cycling tests. Therefore, exercise duration was affected by ME during the sprint cycling exercise, but the ME was constant regardless of exercise intensity and cadence.