Petrofsky Jerrold Scott, Laymon Michael
Department of Physical Therapy, Loma Linda University, Loma Linda, CA 92354, USA.
Eur J Appl Physiol. 2002 Apr;86(6):479-86. doi: 10.1007/s00421-002-0588-2. Epub 2002 Feb 23.
Groups of 50 healthy male controls and 50 subjects suffering from paraplegia (aged 20-65 years) were examined as to the inter-relationships between age, paraplegia and the strength, endurance, blood pressure and heart rate responses to fatiguing isometric exercise. Contractions were maintained in both groups under voluntary effort and through a contraction induced by electrical stimulation in the paraplegic group. All contractions were maintained to fatigue at a tension of 40% of the maximal muscle strength in either the handgrip or quadriceps muscles. Muscle strength of the handgrip was higher in the paraplegic subjects than in the controls, averaging 589 N and 463 N, respectively for the two groups. In contrast, quadriceps leg extension strength averaged 696 N in the controls and 190 N in the paraplegic groups; for both groups, ageing was associated with a reduction in muscle strength. While leg endurance was less in the paraplegic group than the control group, handgrip endurance was similar in the two groups, endurance increasing with ageing in both the controls and paraplegics. Both systolic and diastolic blood pressures increased at rest in paraplegic and control subjects with age. The magnitude of the pressor response to exercise also increased with age. This was true during both voluntary exercise and exercise induced through electrical stimulation in the paraplegic groups. The heart rate response (change in heart rate during exercise) to a fatiguing isometric handgrip contraction decreased by about 50% between the ages of 20 and 60 years in both the controls and paraplegics for isometric handgrip exercise. In contrast, heart rate changed little with age during contractions of the quadriceps muscle in paraplegics which were induced by electrical stimulation.
选取了50名健康男性对照组和50名截瘫患者（年龄在20至65岁之间），研究年龄、截瘫与疲劳等长运动时力量、耐力、血压和心率反应之间的相互关系。两组均在自愿用力的情况下保持收缩，截瘫组则通过电刺激诱发收缩。所有收缩均在握力或股四头肌最大肌肉力量的40%张力下保持至疲劳。截瘫患者的握力高于对照组，两组的平均握力分别为589牛和463牛。相比之下，对照组股四头肌伸展力量平均为696牛，截瘫组为190牛；两组中，肌肉力量均随年龄增长而下降。虽然截瘫组的腿部耐力低于对照组，但两组的握力耐力相似，对照组和截瘫患者的耐力均随年龄增长而增加。截瘫患者和对照组的收缩压和舒张压在静息状态下均随年龄增加。运动时的升压反应幅度也随年龄增加。在截瘫组的自愿运动和电刺激诱发运动中均如此。对于等长握力运动，对照组和截瘫患者在20至60岁之间，疲劳等长握力收缩时的心率反应（运动期间心率变化）下降了约50%。相比之下，截瘫患者在电刺激诱发的股四头肌收缩过程中，心率随年龄变化不大。
