Kemi Ole J, Haram Per M, Loennechen Jan P, Osnes Jan-Bjørn, Skomedal Tor, Wisløff Ulrik, Ellingsen Øyvind
Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
Cardiovasc Res. 2005 Jul 1;67(1):161-72. doi: 10.1016/j.cardiores.2005.03.010. Epub 2005 Apr 20.
Current guidelines are controversial regarding exercise intensity in cardiovascular prevention and rehabilitation. Although high-intensity training induces larger increases in fitness and maximal oxygen uptake (VO(2max)), moderate intensity is often recommended as equally effective. Controlled preclinical studies and randomized clinical trials are required to determine whether regular exercise at moderate versus high intensity is more beneficial. We therefore assessed relative effectiveness of 10-week HIGH versus moderate (MOD) exercise intensity on integrative and cellular functions.
Sprague-Dawley rats performed treadmill running intervals at either 85%-90% (HIGH) or 65%-70% (MOD) of VO2max 1 h per day, 5 days per week. Weekly VO2max-testing adjusted exercise intensity.
HIGH and MOD increased VO2max by 71% and 28%, respectively. This was paralleled by intensity-dependent cardiomyocyte hypertrophy, 14% and 5% in HIGH and MOD, respectively. Cardiomyocyte function (fractional shortening) increased by 45% and 23%, contraction rate decreased by 43% and 39%, and relaxation rate decreased by 20% and 10%, in HIGH and MOD, respectively. Ca2+ transient time-courses paralleled contraction/relaxation, whereas Ca2+ sensitivity increased 40% and 30% in HIGH and MOD, respectively. Carotid artery endothelial function improved similarly with both intensities. EC50 for acetylcholine-induced relaxation decreased 4.3-fold in HIGH (p < 0.05) and 2.8-fold in MOD (p < 0.20) as compared to sedentary; difference HIGH versus MOD 1.5-fold (p = 0.72). Multiple regression identified rate of systolic Ca2+ increase and diastolic myocyte relengthening as main variables associated with VO2max. Cell hypertrophy, contractility and vasorelaxation also correlated significantly with VO2max.
The present study demonstrates that cardiovascular adaptations to training are intensity-dependent. A close correlation between VO2max, cardiomyocyte dimensions and contractile capacity suggests significantly higher benefit with high intensity, whereas endothelial function appears equivalent at moderate levels. Thus, exercise intensity emerges as an important variable in future preclinical and clinical investigations.
当前指南在心血管疾病预防与康复中的运动强度方面存在争议。尽管高强度训练能使体能和最大摄氧量（VO₂max）有更大幅度的提高，但中等强度运动通常也被认为同样有效。需要进行对照的临床前研究和随机临床试验来确定中等强度与高强度的规律运动哪个更有益。因此，我们评估了10周的高强度运动与中等强度（MOD）运动对综合功能和细胞功能的相对有效性。
斯普拉格 - 道利大鼠每周5天、每天1小时在跑步机上进行间歇跑步，强度为VO₂max的85% - 90%（高强度组）或65% - 70%（中等强度组）。每周进行VO₂max测试以调整运动强度。
高强度组和中等强度组分别使VO₂max提高了71%和28%。与此同时，出现了强度依赖性的心肌细胞肥大，高强度组和中等强度组分别为14%和5%。高强度组和中等强度组的心肌细胞功能（缩短分数）分别提高了45%和23%，收缩速率分别降低了43%和39%，舒张速率分别降低了20%和10%。Ca²⁺瞬变的时间进程与收缩/舒张过程相似，而Ca²⁺敏感性在高强度组和中等强度组分别增加了40%和30%。两种强度的运动对颈动脉内皮功能的改善相似。与久坐不动相比，乙酰胆碱诱导舒张的半数有效浓度（EC₅₀）在高强度组降低了4.3倍（p < 0.05），在中等强度组降低了2.8倍（p < 0.20）；高强度组与中等强度组的差异为1.5倍（p = 0.72）。多元回归分析确定收缩期Ca²⁺增加速率和舒张期心肌细胞再延长速率是与VO₂max相关的主要变量。细胞肥大、收缩性和血管舒张也与VO₂max显著相关。
本研究表明心血管系统对训练的适应性是强度依赖性的。VO₂max、心肌细胞大小和收缩能力之间的密切相关性表明高强度运动的益处显著更高，而中等强度水平下内皮功能似乎相当。因此，运动强度在未来的临床前和临床研究中成为一个重要变量。
