PDF(Pubmed)
Abstract：
Background: We investigated the impact of moderate muscle cooling induced by single and intermittent/prolonged cold-water immersions (CWI) on muscle force and contractility in unfatigued state and during the development of fatigue resulting from electrically induced contractions. Methods: Twelve young males participated in this study consisting of two phases [single phase (SP) followed by intermittent/prolonged phase (IPP)], with both phases including two conditions (i.e., four trials in total) performed randomly: control passive sitting (CON) and cold-water immersions (10°C). SP-CWI included one 45 min-bath (from 15 to 60 min). IPP-CWI included three baths (45 min-bath from 15 to 60 min, and 15 min-baths from 165 to 180 min and from 255 to 270 min), with participants sitting at room temperature the rest of the time until 300 min. Blood pressure and intramuscular (Tmu) temperature were assessed, and neuromuscular testing was performed at baseline and 60 min after baseline during SP, and at baseline, 60, 90, 150 and 300 min after baseline during IPP. A fatiguing protocol (100 electrical stimulations) was performed after the last neuromuscular testing of each trial. Results: In unfatigued state, SP-CWI and IPP-CWI reduced electrically induced torque at 100 Hz (P100) but not at 20 Hz (P20), and increased P20/P100 ratio. The changes from baseline for P100 and P20/P100 ratio were lower in IPP-CWI than SP-CWI. Both cold-water immersion conditions slowed down muscle contraction and relaxation, and reduced maximal isokinetic contraction torque, but the changes from baseline were lower after IPP-CWI than SP-CWI. cold-water immersions did not impair maximal voluntary isometric contraction. During the fatiguing protocol, torque fatigue index and the changes in muscle contractile properties were larger after IPP-CWI than SP-CWI, but were in the same range as after CON conditions. The differences of muscle contractile function between SP-CWI and IPP-CWI were accompanied by a lower reduction of superficial Tmu and a smaller increase in systolic blood pressure after IPP-CWI than SP-CWI. Conclusion: IPP-CWI induces a less pronounced fast-to-slow contractile transition compared to SP-CWI, and this may result from the reduced vasoconstriction response and enhanced blood perfusion of the superficial muscle vessels, which could ultimately limit the reduction of superficial Tmu.
摘要：
背景：我们研究了在未疲劳状态下以及在电引起的收缩引起的疲劳发展过程中，单次和间歇性/长时间的冷水浸泡（CWI）引起的适度肌肉冷却对肌肉力量和收缩力的影响。方法：12名年轻男性参加了这项研究，包括两个阶段[单相（SP），然后是间歇/延长阶段（IPP）]。两个阶段都包括两个条件(即，总共进行了四项试验）：对照被动坐姿（CON）和冷水浸泡（10°C）。SP-CWI包括一个45分钟的浴(从15至60分钟)。IPP-CWI包括三个浴（45分钟浴从15到60分钟，和从165到180分钟和从255到270分钟的15分钟浴)，与参与者坐在室温下的其余时间，直到300分钟。评估血压和肌内（Tmu）温度，在基线和基线后60分钟进行神经肌肉测试，在基线，在IPP期间基线后60、90、150和300分钟。在每个试验的最后一次神经肌肉测试之后进行疲劳方案(100次电刺激)。结果：在未疲劳状态下，SP-CWI和IPP-CWI在100Hz（P100）但在20Hz（P20）时未降低电感应扭矩，和增加P20/P100比率。IPP-CWI中P100和P20/P100比率从基线的变化低于SP-CWI。两种冷水浸泡条件都减缓了肌肉的收缩和放松，并降低了最大等速收缩扭矩，但IPP-CWI后的基线变化低于SP-CWI。冷水浸泡不会损害最大自愿等距收缩。在疲劳协议期间，IPP-CWI后的扭矩疲劳指数和肌肉收缩特性的变化大于SP-CWI，但与CON条件后的范围相同。与SP-CWI相比，SP-CWI和IPP-CWI之间的肌肉收缩功能差异伴随着浅表Tmu的降低和IPP-CWI后收缩压的升高较小。结论：与SP-CWI相比，IPP-CWI诱导的快慢收缩转变不太明显，这可能是由于浅表肌肉血管的血管收缩反应减少和血液灌注增强所致，这最终可能会限制表面TMU的减少。
