小川 剛司

Purpose: This study evaluated the effects of exercise training (ET) and inspiratory muscle-loaded exercise training (IMLET) on ventilatory response and intercostal muscle deoxygenation levels during incremental cycling exercise. Methods: Twenty-one male participants were randomly divided into IMLET (n = 10) or ET (n = 11) groups. All participants underwent a 4-week cycling exercise training at 60% peak oxygen uptake. IMLET loaded 50% of maximal inspiratory pressure (PImax). Respiratory muscle strength test, respiratory muscle endurance test (RMET), resting hypoxic ventilatory responsiveness (HVR) test, and incremental cycling test were performed pre- and post-training. Results: The extent of improvement in the PImax was significantly greater in the IMLET group (24%) than in the ET group (8%) (p = .018), and an extended RMET time was observed in the IMLET group (p < .001). Minute ventilation (V˙E) during exercise was unchanged in both groups before and after training, but tidal volume during exercise increased in the IMLET group. The increase in the exercise intensity threshold for muscle deoxygenation was similar in both groups (p < .001). HVR remained unchanged in both groups post-training. The exercise duration for the incremental exercise until reaching fatigue increased by 7.9% after ET and 6.9% after IMLET (p < .001). Conclusion: The 4-week IMLET improved respiratory muscle strength and endurance but did not alter HVR. Respiratory muscle deoxygenation was alleviated by exercise training, with a limited impact of inspiratory load training.

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 &lt; 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.

type:Article 本研究は児童の呼吸筋力の発達と体力の関係を明らかにすることを目的として,79名の児童(低学年21名,中学年31名,高学年27名) において最大努力吸気圧および呼気圧(PImax および PEmax),肺機能および全身持久力,握力を測定した.その結果,PImax および PEmax は年齢とともに高くなり,低学年よりも高学年で高かった(P<0.05).高学年においてのみ男女差が見られた.PImax および PEmax は年齢,体格や肺機能と関係が見られたほか,男子では握力と,女子では全身持久力と有意な相関関係が見られた. It has been reported that respiratory muscle strength (RMS) may be associated with exercise performance. However, the development of respiratory muscle strength in children is not clear enough. The purpose of this study was to investigate and better understand the development of RMS characteristics associating with physical fitness. A cross-sectional study conducted in 79 Japanese elementary school children (21 lower grade, 31 middle grade, 27 higher grade). We measured maximal inspiratory and expiratory muscle pressure (PImax and PEmax), lung function, endurance exercise performance, and grip strength. Both PImax and PEmax increased with age, and Both PImax and PEmax were higher in the higher grade children than in the lower grade children (P<0.05). Both PImax and PEmax were significantly related to age, body size (height and weight), and lung function, as well as to grip strength in boys and endurance exercise performance in girls.

BACKGROUND: Although numerous studies have reported the effect of inspiratory muscle training for improving exercise performance, the outcome of whether exercise performance is improved by inspiratory muscle training is controversial. Therefore, this study investigated the influence of inspiratory muscle-loaded exercise training (IMLET) on peak oxygen uptake (VO2peak), respiratory responses, and exercise performance under normoxic (N) and hypoxic (H) exercise conditions. We hypothesised that IMLET enhances respiratory muscle strength and improves respiratory response, thereby improving VO2peak and work capacity under H condition. METHODS: Sixteen university track runners (13 men and 3 women) were randomly assigned to the IMLET (n = 8) or exercise training (ET) group (n = 8). All subjects underwent 4 weeks of 20-min 60% VO2peak cycling exercise training, thrice per week. IMLET loaded 50% of maximal inspiratory pressure during exercise. At pre- and post-training periods, subjects performed exhaustive incremental cycling under normoxic (N; 20.9 ± 0%) and hypoxic (H; 15.0 ± 0.1%) conditions. RESULTS: Although maximal inspiratory pressure (PImax) significantly increased after training in both groups, the extent of PImax increase was significantly higher in the IMLET group (from 102 ± 20 to 145 ± 26 cmH2O in IMLET; from 111 ± 23 to 127 ± 23 cmH2O in ET; P < 0.05). In both groups, VO2peak and maximal work load (Wmax) similarly increased both under N and H conditions after training (P < 0.05). Further, the extent of Wmax decrease under H condition was lower in the IMLET group at post-training test than at pre-training (from - 14.7 ± 2.2% to - 12.5 ± 1.7%; P < 0.05). Maximal minute ventilation in both N and H conditions increased after training than in the pre-training period. CONCLUSIONS: Our IMLET enhanced the respiratory muscle strength, and the decrease in work capacity under hypoxia was reduced regardless of the increase in VO2peak.

We tested whether expiratory flow limitation (EFL) occurs in endurance athletes in a moderately hypobaric hypoxic environment equivalent to 2500 m above sea level and, if so, whether EFL inhibits peak ventilation ( V ˙ Epeak ), thereby exacerbating the hypoxia-induced reduction in peak oxygen uptake ( V ˙ O2peak ). Seventeen young male endurance runners performed incremental exhaustive running on separate days under hypobaric hypoxic (560 mmHg) and normobaric normoxic (760 mmHg) conditions. Oxygen uptake ( V ˙ O2 ), minute ventilation ( V ˙ E), arterial O2 saturation (SpO2 ), and operating lung volume were measured throughout the incremental exercise. Among the runners tested, 35% exhibited EFL (EFL group, n = 6) in the hypobaric hypoxic condition, whereas the rest did not (Non-EFL group, n = 11). There were no differences between the EFL and Non-EFL groups for V ˙ Epeak and V ˙ O2peak under either condition. Percent changes in V ˙ Epeak (4 ± 4 vs. 2 ± 4%) and V ˙ O2peak (-18 ± 6 vs. -16 ± 6%) from normobaric normoxia to hypobaric hypoxia also did not differ between the EFL and Non-EFL groups (all P > 0.05). No differences in maximal running velocity, SpO2 , or operating lung volume were detected between the two groups under either condition. These results suggest that under the moderate hypobaric hypoxia (2500 m above sea level) frequently used for high-attitude training, ~35% of endurance athletes may exhibit EFL, but their ventilatory and metabolic responses during maximal exercise are similar to those who do not exhibit EFL.

During exposure to high altitude, hypoxia develops because of reductions in barometric pressure and partial pressure of O2 . Although several studies have examined the effects of hypoxia on exercise performance and physiological responses, such as maximal minute ventilation ( V · Emax ) and maximal oxygen uptake ( V · O2max ), how barometric pressure reduction (hypobaria) modulates them remains largely unknown. In this study, 11 young men performed incremental treadmill running tests to exhaustion under three conditions chosen at random: normobaric normoxia (NN; 763 ± 5 mmHg of barometric pressure, equivalent to sea level), hypobaric hypoxia (HH; 492 ± 1 mmHg of barometric pressure, equivalent to 3500 m above sea level (m a.s.l.)), and hypobaric normoxia (HN; 492 ± 1 mmHg of barometric pressure while breathing 32.2 ± 0.1% O2 to match the inspiratory O2 content under NN). V · Emax was higher in HN than in NN (160.9 ± 10.7 vs. 150.7 ± 10.0 L min-1 , P < 0.05). However, no differences in V · O2max and arterial oxyhemoglobin saturation were observed between NN and HN (all P > 0.05). Time to exhaustion was longer in HN than in NN (932 ± 83 vs. 910 ± 79 s, P < 0.05). These results suggest that reduced air density during exposure to an altitude of 3500 m a.s.l. increases maximal ventilation and extends time to exhaustion without affecting oxygen consumption or arterial oxygen saturation.

type:Article 本稿は教育現場における組立体操と集団行動に対する教職員の認識や実態について調べることを目的とした。調査の方法として現職小学校教員および教職課程所属大学生を対象とする質問紙法を採用した結果,次のことが明らかとなった。第一に,調査対象となった者のうちの多くは組立体操の実施に肯定的であり,集団で活動を行うことによる協働の楽しさや達成感を味わうことをねらいとして実施されていることが明らかとなった。第二に,調査対象においては実施に際する安全を確保すべきとの認識が高く,これについて消極的な認識を示す調査対象者であっても,安全の確保における教育的意義を認める者が多数であった。そして第三に,集団行動の実施についても現職教員では大多数がこれを肯定的に捉えており,単に能率性および安全性だけでなく,児童間でのグループワーク等も集団行動として扱うことでこの活動に教育的意義を見出していることが明らかとなった。 This study was aimed to investigate the recognition and actual condition of a group gymnastics and a group action at the practical education field. Survey was conducted by the questionnaire method for elementary school teachers and university students belonging to teacher's courses. As a result, affirmation of conducting a group gymnastics was the majority as far as assuring children's safety, and the aim of conducting a group gymnastics is to experience the enjoyment of gymnastics and the co-operation by doing a group gymnastics. Moreover, affirmation of conducting a group action is a large majority. The objective is not only to assure an efficiency and safety in education, but also to ensure a group work among children.

We tested the hypothesis that short- term exercise- heat acclimation (EHA) attenuates hyperthermiainduced hyperventilation in humans exercising in a hot environment. Twenty- one male subjects were divided into the two groups: control (C, n = 11) and EHA (n = 10). Subjects in C performed exercise- heat tests [ cycle exercise for similar to 75 min at 58% Vover dotO(2peak) (37 degrees C, 50% relative humidity)] before and after a 6- day interval with no training, while subjects in EHA performed the tests before and after exercise training in a hot environment (37 degrees C). The training entailed four 20- min bouts of exercise at 50% Vover dotO(2peak) separated by 10 min of rest daily for 6 days. In C, comparison of the variables recorded before and after the no- training period revealed no changes. In EHA, the training increased resting plasma volume, while it reduced esophageal temperature (T-es), heart rate at rest and during exercise, and arterial blood pressure and oxygen uptake (Vover dot(O2)) during exercise. The training lowered the T-es threshold for increasing forearm vascular conductance (FVC), while it increased the slope relating FVC to T-es and the peak FVC during exercise. It also lowered minute ventilation (Vover dot(E)) during exercise, but this effect disappeared after removing the influence of Vover dot(O2) on Vover dot(E). The training did not change the slope relating ventilatory variables to T-es. We conclude that short- term EHA lowers ventilation largely by reducing metabolism, but it does not affect the sensitivity of hyperthermia- induced hyperventilation during submaximal, moderate- intensity exercise in humans.

To test the hypothesis that maximal exercise pulmonary ventilation ((V) over dotE(max)) is a limiting factor affecting maximal oxygen uptake ((V) over dotO(2max)) in moderate hypobaric hypoxia (H), we examined the effect of breathing a helium-oxygen gas mixture (He-O(2); 20.9% O(2)), which would reduce air density and would be expected to increase (V) over dotE(max). Fourteen healthy young male subjects performed incremental treadmill running tests to exhaustion in normobaric normoxia (N; sea level) and in H (atmospheric pressure equivalent to 2,500 m above sea level). These exercise tests were carried out under three conditions [H with He-O(2), H with normal air and N] in random order. (V) over dotO(2max) and arterial oxy-hemoglobin saturation (SaO(2)) were, respectively, 15.2, 7.5 and 4.0% higher (all p &lt; 0.05) with He-O2 than with normal air ((V) over dotE(max), 171.9 +/- 16.1 vs. 150.1 +/- 16.9 L/min; (V) over dotO(2max), 52.50 +/- 9.13 vs. 48.72 +/- 5.35 mL/kg/min; arterial oxyhemoglobin saturation (SaO(2)), 79 +/- 3 vs. 76 +/- 3%). There was a linear relationship between the increment in (V) over dotE(max) and the increment in (V) over dotO(2max) in H (r = 0.77; p &lt; 0.05). When subjects were divided into two groups based on their (V) over dotO(2max), both groups showed increased (V) over dotE(max) and SaO(2) in H with He-O(2), but (V) over dotO(2max) was increased only in the high (V) over dotO(2max) group. These findings suggest that in acute moderate hypobaric hypoxia, air-flow resistance can be a limiting factor affecting (V) over dotE(max); consequently, (V) over dotO(2max) is limited in part by (V) over dotE(max), especially in subjects with high (V) over dotO(2max).

This study tested the hypothesis that the extent of the decrement in (.)Vo(2max) and the respiratory response seen during maximal exercise in moderate hypobaric hypoxia (H; simulated 2,500 m) is affected by the hypoxia ventilatory and hypercapnia ventilatory responses (HVR and HCVR, respectively). Twenty men (5 untrained subjects, 7 long distance runners, 8 middle distance runners) performed incremental exhaustive running tests in H and normobaric normoxia (N) condition. During the running test, (.)Vo(2), pulmonary ventilation (Ve) and arterial oxyhemoglobin saturation (Sa(O(2))) were measured, and in two ventilatory response tests performed during N, a rebreathing method was used to evaluate HVR and HCVR. Mean HVR and HCVR were 0.36 +/- 0.04 and 2.11 +/- 0.2 l.min(-1).mmHg(-1), respectively. HVR correlated significantly with the percent decrements in (.)Vo(2max) (%d(.)Vo(2max)), Sa(O(2)) [%dSa(O(2)) = (N-H).N(-1).100], and (.)Ve/(.)Vo(2) seen during H condition. By contrast, HCVR did not correlate with any of the variables tested. The increment in maximal Ve between H and N significantly correlated with %d(.)Vo(2max). Our findings suggest that O(2) chemosensitivity plays a significant role in determining the level of exercise hyperventilation during moderate hypoxia; thus, a higher O(2) chemosensitivity was associated with a smaller drop in (.)Vo(2max) and Sa(O(2)) under those conditions.