Ochi Eisuke, Tsuchiya Yosuke, Nosaka Kazunori
Faculty of Bioscience and Applied Chemistry, Hosei University, 3-7-2, Kajino, Koganei, Tokyo, 184-8584, Japan.
Faculty of Modern and Life, Teikyo Heisei University, 4-21-2, Nakano, Tokyo, 164-8530, Japan.
Eur J Appl Physiol. 2016 Dec;116(11-12):2145-2154. doi: 10.1007/s00421-016-3462-3. Epub 2016 Sep 8.
This study compared maximal eccentric (ECC) and concentric (CON) contractions of the elbow flexors for changes in transverse relaxation time (T2) and indirect markers of muscle damage.
Twelve young men performed five sets of six maximal isokinetic (30°/s) ECC with one arm followed by CON with the other arm. Magnetic resonance images to assess T2 and cross-sectional area (CSA) of biceps brachii, brachialis, and brachioradialis, and measurements of maximal voluntary isometric contraction (MVC) torque, range of motion (ROM), and muscle soreness were taken before, immediately after, and 1, 3, and 5 days after each exercise.
MVC torque and ROM decreased greater after ECC than CON (p < 0.05), and muscle soreness developed only after ECC. Biceps brachii and brachialis CSA increased immediately after CON, but delayed increases in brachialis CSA were found only after ECC (p < 0.05). T2 of the muscles increased greater after CON (27-34 %) than ECC (16-18 %) immediately post-exercise (p < 0.05), but returned to baseline by 1 day after CON. The biceps brachii and brachialis T2 increased by 9-29 % at 1-5 days after ECC (p < 0.05). The post-ECC T2 changes showed no significant correlations with the changes in MVC torque, muscle soreness, and CSA, but the T2 increase immediately post-ECC was correlated with the peak T2 in 1-5-day post-ECC (r = 0.63, p < 0.05).
These results suggest that muscle activity during exercise was lower in ECC than CON, and the T2 changes after ECC do not necessarily relate to the changes in other indirect markers of muscle damage.
本研究比较了肘部屈肌的最大离心（ECC）收缩和向心（CON）收缩在横向弛豫时间（T2）和肌肉损伤间接标志物方面的变化。
12名年轻男性用一只手臂进行五组每组6次的最大等速（30°/秒）离心收缩，然后用另一只手臂进行向心收缩。在每次运动前、运动后即刻、运动后1天、3天和5天，采集磁共振图像以评估肱二头肌、肱肌和桡侧腕长伸肌的T2和横截面积（CSA），并测量最大自主等长收缩（MVC）扭矩、活动范围（ROM）和肌肉酸痛情况。
离心收缩后MVC扭矩和ROM的下降幅度大于向心收缩（p<0.05），且肌肉酸痛仅在离心收缩后出现。向心收缩后肱二头肌和肱肌的CSA立即增加，但仅在离心收缩后发现肱肌CSA延迟增加（p<0.05）。运动后即刻，肌肉的T2在向心收缩后增加幅度（27%-34%）大于离心收缩（16%-18%）（p<0.05），但向心收缩后1天恢复至基线水平。离心收缩后1-5天，肱二头肌和肱肌的T2增加了9%-29%（p<0.05）。离心收缩后T2的变化与MVC扭矩、肌肉酸痛和CSA的变化无显著相关性，但离心收缩后即刻T2的增加与离心收缩后1-5天的T2峰值相关（r=0.63，p<0.05）。
这些结果表明，运动期间离心收缩时的肌肉活动低于向心收缩，且离心收缩后T2的变化不一定与其他肌肉损伤间接标志物的变化相关。
