Vedsted Pernille, Blangsted Anne Katrine, Søgaard Karen, Orizio Claudio, Sjøgaard Gisela
Department of Physiology, National Institute of Occupational Health, Copenhagen, Denmark.
Eur J Appl Physiol. 2006 Jan;96(2):165-77. doi: 10.1007/s00421-004-1216-0. Epub 2004 Oct 5.
Dynamic muscle contractions have been shown to cause greater energy turnover and fatigue than static contractions performed at a corresponding force level. Therefore, we hypothesized that: (1) electro- (EMG) and mechanomyography (MMG), intramuscular pressure (IMP), and reduction in muscle oxygen tension (rTO(2)) would be larger during dynamic (DYN) than intermittent static (IST) low force contractions; and that (2) oxygen tension would remain lower in the resting periods subsequent to DYN as compared to those following IST. Eight subjects performed elbow flexions with identical time-tension products: (1) DYN as a 20 degrees elbow movement of 2 s concentric and 2 s eccentric followed by a 4 s rest; and (2) IST with a 4 s contraction followed by a 4 s rest. Each session was performed for 1 min at 10 and 20% of the maximal voluntary contraction (MVC). The force, bipolar surface EMG, MMG, IMP, rTO(2) were measured simultaneously from the biceps brachii, and the data presented as the mean values together with the standard error of the means. Comparison of the corresponding time periods showed the EMG(rms) and MMG(rms) values to be larger during DYN than IST (concentric phase: DYN vs IST were 14.2 vs 9.4, and 22.0 vs 15.9%(max)-EMG(rms); eccentric phase: in DYN, the MMG was approximately 1.5 and approximately 2.0-fold IST at 10 and 20%MVC, respectively). In contrast, the IMP of the concentric phase in DYN was lower than in IST (2.3 vs 29.5 and 10.9 vs 42.0 mmHg at 10 and 20%MVC, respectively), and a similar picture was seen for the eccentric phase. However, no differences were seen in rTO(2) in either the contraction or the rest periods. In a prolonged rest period (8 s) after the sessions, DYN but not IST showed rTO(2) above baseline level. In conclusion, rTO(2) in DYN and IST were similar in spite of major differences in the MMG and EMG responses of the muscle during contraction periods. This may relate to the surprisingly lower IMP in DYN than IST.
与在相应力水平下进行的静态收缩相比，动态肌肉收缩已被证明会导致更大的能量转换和疲劳。因此，我们假设：（1）在动态（DYN）而非间歇性静态（IST）低强度收缩期间，肌电图（EMG）和肌机械图（MMG）、肌内压（IMP）以及肌肉氧张力降低（rTO₂）会更大；并且（2）与IST之后的静息期相比，DYN之后的静息期氧张力会保持更低。八名受试者进行具有相同时间 - 张力乘积的肘部屈曲：（1）DYN为20度肘部运动，2秒向心收缩和2秒离心收缩，随后休息4秒；（2）IST为4秒收缩，随后休息4秒。每个阶段在最大自主收缩（MVC）的10%和20%下进行1分钟。同时测量肱二头肌的力量、双极表面肌电图、肌机械图、肌内压、rTO₂，并将数据表示为平均值以及均值的标准误差。对相应时间段的比较表明，DYN期间的肌电图（均方根）和肌机械图（均方根）值大于IST（向心阶段：DYN与IST的肌电图（均方根）分别为14.2与9.4以及22.0与15.9%（最大值）；离心阶段：在DYN中，在10%和20%MVC时，肌机械图分别约为IST的1.5倍和约2.0倍）。相反，DYN向心阶段的肌内压低于IST（在10%和20%MVC时分别为2.3与29.5以及10.9与42.0 mmHg），离心阶段也有类似情况。然而，在收缩期或静息期，rTO₂均未观察到差异。在阶段后的延长静息期（8秒），DYN而非IST显示rTO₂高于基线水平。总之，尽管收缩期肌肉的肌机械图和肌电图反应存在重大差异，但DYN和IST中的rTO₂相似。这可能与DYN中肌内压出人意料地低于IST有关。
