Comparison between young and older women in explosive power output and its determinants during a single leg-press action after optimisation of load

Abstract

Lower limb explosive power, which is more predictive of functional difficulties than strength per se with women being more at risk than men for disability, has been previously compared between young and older women using systems with fixed inertia. Individuals may have been obliged to use a percentage of their maximum strength that is not ideal for performing the movement at the optimum speed for maximum power output. This study was designed to compare explosive power output and its two determinants, optimal force and optimal speed, during a leg-press action between young and older women after optimising the load for maximum power production. The experiments were carried out on 20 women in good physical condition: 10 older, aged between 65 and 74 years and 10 young, aged between 18 and 30. Explosive power output was measured by setting the initial load at different percentages of maximum isometric strength and measuring the corresponding speed of movement during a leg-press action of the dominant leg. Maximum peak power, which was obtained at 60% of maximum isometric strength in both young and older women, was 61% lower in the older women ( P<0.0001). This was due to a 52% lower optimal force ( P<0.0001) and 21% lower optimal speed ( P<0.01). The ratio of peak power to maximum isometric strength was 22.1% lower in the older women ( P<0.01). After optimising the load, both lower speed of movement and lower strength determine the lower levels of power in older women. Power is more affected by ageing than isometric strength.

Peripheral impairments cause a progressive age-related loss of strength and velocity-dependent power in the dorsiflexors

“…In this mode, a resistance load can be programmed that the dynamometer attempts to hold constant while velocity is measured throughout a ROM. Current dynamometers are unable to maintain a constant load, so movements made in the isotonic mode are not strictly isotonic (15). However, for the purposes of this study, the term isotonic will be used throughout the remainder of this paper to describe this movement type.…”

“…However, with the exception of our recent fatigue study (20), the elderly participants involved in the previous velocity-dependent studies represent the "young" elderly, i.e., Ͻ70 yr of age (5,15,24,29). For some muscle groups, this age range may be too young to effectively characterize power loss.…”

“…IN ADDITION TO A DECLINE IN strength, aging is associated with a loss of voluntary contractile velocity which, when combined with the loss of absolute torque output, results in great reductions in power (5,15,20,24,29). Whereas strength capacity is most easily assessed from static (isometric) contractions, power is measured from more complex dynamic movements that involve both strength and velocity of contractions.…”

“…Despite this understanding, there are few studies that explore age-related changes to muscle power during isotonic (velocitydependent) contractions (5,15,20,24,29).…”

Asymmetrical Lower Extremity Loading Early After Anterior Cruciate Ligament Reconstruction Is a Significant Predictor of Asymmetrical Loading at the Time of Return to Sport

“…The MVC task consisted of an increase to a maximum in the force exerted by the leg muscles. 20 Participants were able to follow their performance on the computer screen and were verbally encouraged to achieve a maximum and to maintain it for at least 2 s before relaxing. A target line was always set on the computer screen at a value 20% higher than the best performance.…”