Evidence for a Non-linear Relationship between Leg Strength and Gait Speed

Abstract

Although the relationship between strength and physical performance in older adults is probably non-linear, few empirical studies have demonstrated that this is so. In a population-based sample of adults aged 60-96 years (n = 409), leg strength was measured in four muscle groups (knee extensor, knee flexor, ankle plantar flexor, ankle dorsiflexor) of both legs using an isokinetic dynamometer. A leg strength score was calculated as the sum of the four strength measurements in the right leg. Usual gait speed was measured over a 15.2 metre course. With a linear model, leg strength explained 17% of the variance in gait speed. Non-linear models (quadratic and inverse) explained significantly more variance (22%). The nature of the non-linear relationship was that, in stronger subjects, there was no association between strength and gait speed, while in weaker subjects, there was an association. Body weight and age also explained significant amounts of variance in gait speed, while sex and height did not. The results supported the hypothesis of a non-linear relationship between leg strength and gait speed that is similar for older men and women. This finding represents a mechanism for how small changes in physiological capacity may have substantial effects on performance in frail adults, while large changes in capacity have little or no effect in healthy adults.

Análise de métodos para detectar sarcopenia em idosas independentes da comunidade

“…One of these participants was the oldest participant in the study (84 years) and was the only women to be classified with severe sarcopenia, due to the fact that she met all of the diagnostic criteria. According to Buchner et al, 32 gait speed declines with age, but there is a non-linear correlation between the strength of the lower limbs and normal gait speed. This correlation represents the mechanism through which minor alterations in physiological capacity can have substantial effects on the performance of frail adults, whereas major alterations in healthy adults have little or no effect on their daily function.…”

Frailty in Older Adults: Evidence for a Phenotype

“…There is a growing consensus that markers of frailty include age-associated declines in F lean body mass, strength, endurance, balance, walking performance, and low activity (9,10,(14)(15)(16)(17), and that multiple components must be present clinically to constitute frailty (9,14). Many of these factors are related (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31) and can be unified, theoretically, into a cycle of frailty associated with declining energetics and reserve ( Figure 1). The core elements of this cycle are those commonly identified as clinical signs and symptoms of frailty (9,10,(14)(15)(16).…”

Towards a definition of sarcopenia — results from epidemiologic studies

“…A cutpoint of 0.80 Nm/kg.m(-1) has also been proposed (23). A point where low leg strength starts to impair gait speed cannot be easily identified since gait speed is influenced by other performance factors as well (24). Finally, a potential disadvantage for a clinical application of these proposed cutpoints is the use of an isokinetic strength measurement.…”