Age differences in knee extension power, contractile velocity, and fatigability

Abstract

The purposes of this study were to examine age and gender differences in knee extensor strength, power, and fatigue using open- and closed-chain testing procedures. We tested the hypothesis that specific strength (strength/unit muscle mass) would not differ by age, whereas age differences in specific power and fatigue would remain consequent to blunted maximal contractile velocity. Skeletal muscle performance was examined in 28 young (26.9 +/- 0.7 yr) and 24 older (63.6 +/- 0.8 yr) men and women. Assessments included one-repetition maximum strength for knee extension, leg press, and squat; concentric knee extensor peak power, velocity, and fatigability; and sit-to-stand power, fatigability, and relative neural activation (electromyograph activity during sit-to-stand movement normalized to electromyograph activity during isometric maximum voluntary contraction). Thigh lean mass (TLM; kg) was assessed by dual-energy X-ray absorptiometry. Specific strength (N/kg TLM) and specific power (W/kg TLM) were estimated by dividing absolute values by TLM. Age differences in specific strength were observed for knee extension only (young, 41.2 +/- 1.0 N/kg TLM; older, 32.4 +/- 1.0 N/kg TLM; P < 0.05). Adjustment for TLM did not negate age differences in knee extension specific power (25-41% lower in older; P < 0.05) across loads tested. Older adults experienced fatigue across 10 repetitions of knee extension as peak velocity fell by 24% (P < 0.05). Deficits in concentric power persist after adjustment for TLM as maximum contractile velocity falls markedly with aging. Older adults are less capable of sustaining maximum concentric velocity during repetitive contractions. These findings suggest that velocity impairments are a possible contributor to mobility loss and falls risk among older adults. Interventions for improving contractile velocity should be pursued.

Biomechanical Analysis of Gait and Sit-to-Stand Patterns Using a Specially Made Knee Supporter in Healthy Young and Elderly Individuals

“…However, the slower walking speed chosen by the elderly subjects might be also dependent on weakness of the quadriceps muscles caused by aging (Norris et al, 2007;Tiedemann et al, 2005). As noted before, the number of fast twitch fibers decreases with aging (Lexell et al, 1988;Petrella et al, 2005). If the quadriceps muscle is weakened and/or the number of fast twitch fibers of the quadriceps muscles is decreased or vice versa, then the risk of falling, which can cause serious injury, is increased.…”

“…Some previous studies indicated that a systematic decrease in the number of fast twitch fibers of the quadriceps muscles 68 Biomechanical Analysis of Gait and STS occurred with an association of aging (Lexell et al, 1988;Petrella et al, 2005). If the number of fast twitch fibers of the quadriceps muscles was decreased, then the dynamic postural stability would also be decreased because the sensorimotor function would be slowed in these muscles (Lord et al, 1996).…”

“…It was found that older adults exhibited a longer execution time than younger adults for executing STS (Demura and Yamada, 2007), possibly due to the poorer leg muscle strength and lean thigh mass in elderly adults (Petrella et al, 2005). These differences associated with aging will be further concerned with the dynamic function of those muscles.…”

O efeito da atividade física no aparelho locomotor do idoso

“…A perda da potência muscular é maior que a da força devido à perda seletiva das fibras tipo II (fibras de contração rápida). A diminuição da potência muscular determina diminuição da velocidade de contração muscular e esta perda nos músculos responsáveis pela manutenção da postura ortostática pode contribuir para o aumento do número de quedas (19) . Neurologicamente, existe diminuição, eventualmente modulada por sinais aferentes das articulações comprometidas (inibição artrogênica), do número e do tamanho das unidades motoras e isso é também uma causa primária da perda da força muscular (20) .…”

The Dynamics of Respiratory Muscle Changes During the Progression of Chronic Obstructive Pulmonary Disease

“…This is caused by suppressed formation of humoral factors that stimulate protein synthesis, with the simultaneous expression of subclinical inflammation factors (TNf-α, IL-6) and a decline in myocyte apoptosis [28,29].…”