Muscle Physiology Laboratory, Dept. of Kinesiology, Univ. of Massachusetts, Amherst, Amherst MA 01003, USA.
J Appl Physiol (1985). 2011 Nov;111(5):1345-52. doi: 10.1152/japplphysiol.00367.2011. Epub 2011 Aug 25.
It is generally accepted that the muscles of aged individuals contract with less force, have slower relaxation rates, and demonstrate a downward shift in their force-velocity relationship. The factors mediating age-related differences in skeletal muscle fatigue are less clear. The present study was designed to test the hypothesis that age-related shifts in the force-velocity relationship impact the fatigue response in a velocity-dependent manner. Three fatigue protocols, consisting of intermittent, maximum voluntary knee extension contractions performed for 4 min, were performed by 11 young (23.5 ± 0.9 yr, mean ± SE) and 10 older (68.9 ± 4.3) women. The older group fatigued less during isometric contractions than the young group (to 71.1 ± 3.7% initial torque and 59.8 ± 2.5%, respectively; P = 0.02), while the opposite was true during contractions performed at a relatively high angular velocity of 270°·s(-1) (old: 28.0 ± 3.9% initial power, young: 52.1 ± 6.9%; P < 0.01). Fatigue was not different (P = 0.74) between groups during contractions at an intermediate velocity, which was selected for each participant based on their force-velocity relationship. There was a significant association between force-velocity properties and fatigue induced by the intermediate-velocity fatigue protocol in the older (r = 0.72; P = 0.02) and young (r = 0.63; P = 0.04) groups. These results indicate that contractile velocity has a profound impact on age-related skeletal muscle fatigue resistance and suggest that changes in the force-velocity relationship partially mediate this effect.
人们普遍认为，老年人的肌肉收缩力较弱，放松速度较慢，并且其力量-速度关系呈现下降趋势。介导与年龄相关的骨骼肌疲劳差异的因素尚不明确。本研究旨在检验以下假设：与年龄相关的力量-速度关系的转变以速度依赖的方式影响疲劳反应。通过三个疲劳方案来测试该假设，这些方案由间歇性、最大自主膝关节伸展收缩组成，持续 4 分钟，由 11 名年轻（23.5±0.9 岁，均值±SE）和 10 名老年（68.9±4.3）女性完成。与年轻组相比，老年组在等长收缩时疲劳程度较轻（分别降至初始扭矩的 71.1±3.7%和 59.8±2.5%；P=0.02），而在以相对较高角速度 270°·s(-1)进行收缩时则相反（老年组：28.0±3.9%初始功率，年轻组：52.1±6.9%；P<0.01）。在以中间速度进行收缩时，两组之间的疲劳程度没有差异（P=0.74），该中间速度是根据每个参与者的力量-速度关系选择的。在老年（r=0.72；P=0.02）和年轻（r=0.63；P=0.04）组中，中间速度疲劳方案引起的疲劳与力量-速度特性之间存在显著相关性。这些结果表明收缩速度对与年龄相关的骨骼肌疲劳抵抗力有深远影响，并表明力量-速度关系的变化部分介导了这种影响。
