Ageing and isokinetic plantar flexion

Abstract

Isokinetic torques (Cybex II) of the plantar flexors in 25 healthy men were compared at 5 angular velocities (30, 60, 90, 120 and 180 degrees X s-1). The purposes were to compare plantar flexion torques in young and old subjects, and to determine whether the expected decrease was significantly associated with age, physical activity, or aerobic fitness. Four groups were studied: young (21.7 +/- 2.0 years) and older (63.3 +/- 2.8 years), active and sedentary. Measurements of height, weight, % body fat, VO2max, and daily leisure energy expenditure (questionnaire) were determined for each subject. Statistical measures of analysis of variance were used to determine significant differences among groups; product moment correlation and stepwise regression analysis were used to describe the degree of association between the dependent variable of plantar flexion torque and the independent variables at each velocity. A decline in torque was observed as the isokinetic velocity of angular motion increased. Age alone was a significant determinant of plantar flexion torque, whereas at the slowest speed, when VO2max was used as an explanatory variable, age was not a significant determinant of torque. At 30 degrees X s-1 47% of the variance in torque was explained by VO2max while at 180 degrees X s-1 49% of the variance was explained by age.

Effects of aging and resistance exercise on determinants of muscle strength

“…It has been reported by Larsson et al (1) that muscle strength is maintained between the ages of 30-50 but after the age of 50 until 70 there is approximately a 30% drop in muscle strength. Similar reductions in muscle force generating capacity with age have been reported by others (2)(3)(4). A large proportion of this decline in strength is due to a reduction in the size and or number of type II or fast twitch muscle fibers (5).…”

The oscillatory behavior of the CoM facilitates mechanical energy balance between push-off and heel strike

“…However, the direction of the heel strike impulse (g) did not change significantly, and the direction of the push-off impulse (b), i.e., the ratio of the forward to vertical impulses, increased with gait speed (Fig. 3B), which may be required to propel the CoM forward with more force at faster gait speeds given the limited plantar flexor torque (Fugl-Meyer, 1981;Cunningham et al, 1987;Zajac, 1989;Neptune and Sasaki, 2005) as opposed to the proportional increase of the heel strike loss with the speed. The average data of overlap parameters had the same order of magnitude as those previously published (Adamczyk and Kuo, 2009;Yeom and Park, 2011) but were smaller in magnitude due to the different gait speed ranges for averaging.…”

Effects of ageing on motor unit activation patterns and reflex sensitivity in dynamic movements

“…Ageing is associated with a decrease in muscle force and power, beginning after the age of 50 (Cunningham et al, 1987;Doherty et al, 1993). This decrease is in large part due to a loss of muscle mass (sarcopenia), which is caused by a progressive decrease in the number of muscle fibers (Brown et al, 1988;Frontera et al, 1991).…”