SENSITIVITY OF MUSCLE PROTON SPIN-SPIN RELAXATION-TIME AS AN INDEX OF MUSCLE ACTIVATION
SENSITIVITY OF MUSCLE PROTON SPIN-SPIN RELAXATION-TIME AS AN INDEX OF MUSCLE ACTIVATION
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DOI：
10.1152/jappl.1994.77.1.84
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发表时间：
1994-07-01
影响因子：
3.3
通讯作者：
ENOKA, RM
中科院分区：
文献类型：
--
作者：
YUE, G;ALEXANDER, AL;ENOKA, RM
本研究的目的是确定在给定的运动强度下，检测肌肉质子自旋-自旋弛豫时间（T-2）增加所需的最小收缩次数。五名健康的人类受试者进行了五组锻炼，包括肘屈肌肌肉的同心和偏心收缩，负荷为最大值的25%或80%。在80%的负荷下，五组涉及1，2，5，10或20次重复的练习;在25%的负荷下，五组分别为2，5，10，20或40次重复。在每组运动之前和之后立即对每个受试者的上臂进行成像。使用肢体线圈收集自旋回波图像（重复时间/回波时间= 2，000 ms/30、60、90和120 ms），并计算T-2值。从肘屈肌和肘伸肌以及肱骨骨髓测量信号强度。在80%负荷下，手肘运动2次后肱二头肌短头的T-2增加，5次后肱肌和肱二头肌长头的T-2增加。在25%负荷下，肱二头肌短头重复5次后，肱肌和肱二头肌长头重复10次后，T-2变长。T-2与肘屈肌在任一负荷下的收缩重复次数呈线性关系（r（2）≥ 0.97，P < 0.001）。肘屈肌和肘伸肌的静息T-2值分布不均匀，肱三头肌三个头在一组运动后的T-2值也不同。这些发现表明：1）T-2检测肌肉活动的灵敏度取决于收缩强度，2）在特定范围内，T-2随肌肉做功线性变化，3）手肘关节屈肌或伸肌内的肌纤维募集对于给定任务是不同的。
The purpose of this study was to determine the minimum number of contractions that are needed to detect an increase in the muscle proton spin-spin relaxation time (T-2) at a given exercise intensity. Five healthy human subjects performed five sets of an exercise that included concentric and eccentric contractions of the elbow-flexor muscles with loads that were 25 or 80% of maximum. With the 80% load, the five sets involved 1, 2, 5, 10, or 20 repetitions of the exercise; with the 25% load the five sets were 2, 5, 10, 20, or 40 repetitions. The upper arm of each subject was imaged before and immediately after each set of the exercise. Spin-echo images (repetition time/echo time = 2,000 ms/30, 60, 90, and 120 ms) were collected using an extremity coil, and T-2 values were calculated. The signal intensity was measured from the elbow-flexor and -extensor muscles and from the bone marrow of the humerus. With the 80% load, T-2 increased in the short head of the biceps brachii after two repetitions of the elbow exercise and after five repetitions in the brachialis and the long head of the biceps brachii. With the 25% load, T-2 became longer after five repetitions of the exercise for the short head of the biceps brachii and after 10 repetitions for the brachialis and the long head of the biceps brachii. T-2 varied linearly with the number of contraction repetitions for each of the elbow-flexor muscles at either load (r(2) greater than or equal to 0.97, P < 0.001). The resting T-2 value was not uniformly distributed among the elbow-flexor and -extensor muscles, and the T-2 after a given set of the exercise was different among the three heads of the triceps brachii. These findings suggest that 1) the sensitivity of T-2 for detecting muscle activity depends on the contraction intensity, 2) within a specified range T-2 varies linearly with work performed by the muscle, and 3) recruitment of the muscle fibers is different for a given task among the compartments within the flexor or extensor muscles of the elbow joint.