Mechanical and metabolic determination of VO2 and fatigue during repetitive isometric contractions in situ.
Mechanical and metabolic determination of VO2 and fatigue during repetitive isometric contractions in situ.
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原位重复等长收缩期间 VO2 和疲劳的机械和代谢测定。
DOI：
10.1152/jappl.1998.84.6.1909
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Stainsby,WN
中科院分区：
文献类型：
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作者：
Ameredes,BT;Brechue,WF;Stainsby,WN
研究了犬腓肠肌-跖肌在最佳长度（Lo）和短长度（Ls; ≤ 0.9 <$Lo）下的重复等长强直收缩（1/s），以确定初始长度对原位力学和代谢性能的影响。机械和代谢变量的相应平均值为（Lovs.Ls，均P < 0.05）被动张力（前负荷）= 55 vs. 6 g/g，最大主动强直张力（Po）= 544 vs. 174（0.38 μ Po）g/g，最大血流量（Q stec）= 2.0 vs. 1.4 ml·min-1·g-1，最大摄氧量（V steco 2）= 12 vs. 9 μmol·min-1·g-1。在20分钟的重复收缩中，Lo处的张力下降到0.64 mmHg，表明疲劳;在Ls处的张力没有显著变化。在Lo下收缩的单独肌肉中，将Q stec设置为atLs测量值（1.1 ml·min-1·g-1），导致V steco 2（7 μmol·min-1·g-1）降低，并快速疲劳，达到0.44 Po。这些数据表明：1）Lo的肌肉Q和V o2值高于LS;2）Lo在V o2较高时会出现疲劳，调整代谢需求（张力输出）以匹配供应; 3）Ls张力、Q和V o2较低，缺乏疲劳表明代谢需求充分匹配，通过短肌肉长度降低代谢需求，通过低预负荷优化供应。Loc组和Ls组之间的张力和V steco 2的这些差异表明，在小于Loc的初始长度处等距收缩的肌肉是在次最大条件下工作的。
Repetitive isometric tetanic contractions (1/s) of the canine gastrocnemius-plantaris muscle were studied either at optimal length (Lo) or short length (Ls; ∼0.9 ⋅Lo), to determine the effects of initial length on mechanical and metabolic performance in situ. Respective averages of mechanical and metabolic variables were (Lovs.Ls, allP< 0.05) passive tension (preload) = 55 vs. 6 g/g, maximal active tetanic tension (Po) = 544 vs. 174 (0.38 ⋅ Po) g/g, maximal blood flow (Q˙) = 2.0 vs. 1.4 ml ⋅ min−1⋅ g−1, and maximal oxygen uptake (V˙o2) = 12 vs. 9 μmol ⋅ min−1⋅ g−1. Tension atLodecreased to 0.64 ⋅ Poover 20 min of repetitive contractions, demonstrating fatigue; there were no significant changes in tension atLs. In separate muscles contracting atLo,Q˙ was set to that measured atLs(1.1 ml ⋅ min−1⋅ g−1), resulting in decreased V˙o2(7 μmol ⋅ min−1⋅ g−1), and rapid fatigue, to 0.44 ⋅ Po. These data demonstrate that1) muscles atLohave higher Q˙ andV˙o2values than those atLs;2) fatigue occurs atLowith highV˙o2, adjusting metabolic demand (tension output) to match supply; and3) the lack of fatigue atLswith lower tension, Q˙, andV˙o2suggests adequate matching of metabolic demand, set low by short muscle length, with supply optimized by low preload. These differences in tension andV˙o2betweenLoandLsgroups indicate that muscles contracting isometrically at initial lengths shorter thanLoare working under submaximal conditions.