Kamen Gary, Knight Christopher A
Department of Exercise Science, University of Massachusetts at Amherst, Amherst, MA 01003-9258, USA.
J Gerontol A Biol Sci Med Sci. 2004 Dec;59(12):1334-8. doi: 10.1093/gerona/59.12.1334.
This study evaluated changes in motor unit (MU) firing rates in young and older adults during exercise training.
Vastus lateralis MU discharge rates were measured in 8 young and 7 older adults. Each participant performed isometric knee extension contractions at 10%, 50%, and 100% of maximal voluntary contraction or effort (MVC) on two separate occasions. Participants then completed a 6-week resistance exercise training protocol.
Significant increases in maximal force were observed as early as 1 week after the first baseline testing session, and these were accompanied by increases in the MU discharge rate. Exercise training increased maximal voluntary force by 29% and 36% in the young and older adults, respectively. Motor unit discharge rates at 100% of maximal effort were significantly greater in the young (24.7 pps) than in the older adults (17.8 pps). Furthermore, the young adults also exhibited significantly greater discharge rates at 50% MVC, but there were no differences at the 10% force level. Maximal MU discharge rates increased during the 1-week period separating the two initial testing sessions. After the 6-week training period, maximal MU discharge rates were 15% higher for the young adults and 49% higher for the older adults. No changes in discharge rates were observed for either group at 10% or 50% MVC after exercise training.
The early increase in maximal MU discharge rate with repeated maximal force assessment may comprise an important neural mechanism mediating early, rapid gains in muscular force capability.
本研究评估了年轻人和老年人在运动训练期间运动单位（MU）放电频率的变化。
对8名年轻人和7名老年人的股外侧肌MU放电率进行了测量。每位参与者在两个不同的场合，以最大自主收缩或用力（MVC）的10%、50%和100%进行等长膝关节伸展收缩。参与者随后完成了为期6周的抗阻运动训练方案。
早在第一次基线测试 session 后1周就观察到最大力量显著增加，同时MU放电率也增加。运动训练使年轻人和老年人的最大自主力量分别增加了29%和36%。在最大用力的100%时，年轻人的运动单位放电率（24.7次/秒）显著高于老年人（17.8次/秒）。此外，年轻人在50%MVC时的放电率也显著更高，但在10%用力水平时没有差异。在两次初始测试 session 之间的1周内，最大MU放电率增加。在为期6周的训练期后，年轻人的最大MU放电率提高了15%，老年人提高了49%。运动训练后，两组在10%或50%MVC时的放电率均未观察到变化。
随着重复的最大力量评估，最大MU放电率的早期增加可能是介导肌肉力量能力早期快速增加的重要神经机制。
