Fujiwara K, Kunita K, Toyama H
Faculty of Medicine, Kanazawa University, 13-1 Takara-machi, Kanazawa, 920-8640 Japan.
Eur J Appl Physiol. 2000 Mar;81(4):317-24. doi: 10.1007/s004210050049.
We investigated changes in saccadic reaction time in relation to the degree of increase in activity of neck extensor muscles when neck flexion occurred, and assessed the reliability of the measurements. Saccadic reaction time was measured firstly, during neck flexion angles set at 5 degrees increments from 0 degrees (resting position) to 25 degrees, with the chin either resting on a stand or not, and secondly, during shoulder girdle elevator muscles providing a relative muscle force of 30%, with the neck flexion angle maintained at 0 degrees by having the subjects rest their chins on a stand. Saccadic reaction time was evaluated by the latency to the beginning of eye movement toward the lateral target, which was moved at random intervals in 20 degrees amplitude jumps. Muscle activity in the trapezius muscle was evaluated using the mean amplitude of electromyogram recordings. Very high coefficients of reliability in muscle activity and saccadic reaction time were observed between the two sets of tests at 1-h intervals and also among the three trials with a 1-min rest. When their necks were flexed and the subjects rested their chins on a stand, muscle activity increased slightly in accordance with the enlargement of this angle, with no significant change in saccadic reaction time. With the chin not resting on the stand, muscle activity increased gradually, while the saccadic reaction time decreased to that obtained at an average neck flexion angle of 20 degrees. However, the angle where the shortest reaction time was obtained showed considerable individual variation (5-25 degrees ). Activity in the trapezius muscle at a 20 degrees neck flexion angle, with the chin not resting on the stand, was far less than that for 30% maximal voluntary contraction in shoulder girdle elevator muscles. Nevertheless, the saccadic reaction times were roughly equivalent under the two different sets of conditions. No sex differences were observed in terms of saccadic reaction time under any set of conditions.
我们研究了颈部屈曲时眼跳反应时间与颈部伸肌活动增加程度之间的关系，并评估了测量的可靠性。首先，在颈部屈曲角度从0度（休息位置）以5度增量设置到25度的过程中，测量眼跳反应时间，此时下巴要么靠在支架上，要么不靠在支架上；其次，在肩胛带提升肌提供30%相对肌力的情况下，让受试者将下巴靠在支架上，使颈部屈曲角度保持在0度，测量眼跳反应时间。眼跳反应时间通过朝向侧向目标开始眼动的潜伏期来评估，该目标以20度幅度跳跃的随机间隔移动。使用肌电图记录的平均幅度评估斜方肌的肌肉活动。在间隔1小时的两组测试之间以及在休息1分钟的三次试验中，观察到肌肉活动和眼跳反应时间的可靠性系数非常高。当受试者颈部屈曲并将下巴靠在支架上时，肌肉活动随着该角度的增大而略有增加，眼跳反应时间没有显著变化。下巴不靠在支架上时，肌肉活动逐渐增加，而眼跳反应时间缩短至平均颈部屈曲角度为20度时的水平。然而，获得最短反应时间的角度存在相当大的个体差异（5 - 25度）。在颈部屈曲角度为20度且下巴不靠在支架上时，斜方肌的活动远低于肩胛带提升肌最大自主收缩的30%。尽管如此，在两种不同条件下眼跳反应时间大致相当。在任何一组条件下，眼跳反应时间均未观察到性别差异。
