Effects of age on muscle power, postural control and functional capacity after short-term immobilization and retraining.

OBJECTIVES: This study investigated the effect of lower limb immobilization and retraining on postural control and muscle power in healthy old and young men. METHODS: Twenty men, nine old (OM:67.3±4.4 years) and eleven young (YM:24.4±1.6 years) underwent 2 weeks of unilateral whole-leg casting, followed by 4 weeks of retraining. Measures included center of pressure (CoP) sway length and area during single- and double-leg stance, maximal leg extensor muscle power, habitual and maximal 10-m gait speed, sit-to-stand performance, and 2-min step test. RESULTS: After immobilization, leg extension muscle power decreased by 15% in OM (from 2.68±0.60 to 2.29±0.63 W/kg, p<0.05) and 17% in YM (4.37±0.76 to 3.63±0.69 W/kg, p<0.05). Double-leg CoP sway area increased by 45% in OM (218±82 to 317±145 mm2; p<0.05), with no change in YM (p=0.43). Physical function did not change after immobilization but sit-to-stand performance (+20%, p<0.05) and 2-min step test (+28%, p<0.05) increased in OM following retraining. In both groups, all parameters returned to baseline levels after retraining. CONCLUSION: Two weeks of lower limb immobilization led to decreases in maximal muscle power in both young and old, whereas postural control was impaired selectively in old men. All parameters were restored in both groups after 4 weeks of resistance-based retraining.

Comfortable and Maximum Gait Speed in Individuals with Chronic Stroke and Community-Dwelling Controls.

BACKGROUND: The relationship between maximum and comfortable gait speed in individuals with mild to moderate disability in the chronic phase of stroke is unknown. OBJECTIVE: This study examines the relationship between comfortable and maximum gait speed in individuals with chronic stroke and whether the relationship differ from that seen in a community-dwelling elderly population. Further, we investigate the influence of age, gender, time post-stroke and degree of disability on gait speed. MATERIALS AND METHODS: Gait speed was measured using the 10-meter walk test (10MWT) and the 30-meter walk test (30MWT) in 104 older individuals with chronic stroke and 154 community-dwelling controls, respectively. RESULTS: We found that the maximum gait speed in individuals with stroke could be estimated by multiplying the comfortable speed by 1.41. This relationship differed significantly from that of the control group, for which the corresponding factor was 1.20. In the stroke group, age, gender and time post-stroke did not affect the relationship, whereas the degree of disability was negatively correlated with maximum speed - but not when included in the multiple analysis. In the community-dwelling population, higher age and female gender had a negative relationship with maximum gait speed. When correcting for those parameters, the coefficient was 1.07. CONCLUSIONS: The maximum gait speed in the chronic phase of stroke can be estimated by multiplying the individual's comfortable gait speed by 1.41. This estimation is not impacted by age, gender, degree of disability and time since stroke. A similar but weaker relationship can be seen in the community-dwelling controls.

The effects of ageing on functional capacity and stretch-shortening cycle muscle power.

[Purpose] To examine the effects of age and gender in an ageing population with respect to functional decline and the relationship between muscle power and functional capacity. [Participants and Methods] The cohort (N=154) was subdivided into youngest-old (65-70 years.; n=62), middle-old (71-75 years.; n=46), and oldest-old (76-81 years.; n=46). Measures of mechanical muscle function included countermovement jump height, muscle power, leg strength and grip strength. Functional performance-based measures included heel-rise, postural balance, Timed Up and Go, and gait speed. [Results] The oldest-old performed significantly worse than the middle-old, whereas the youngest-old did not outperform the middle-old to the same extent. Increased contribution of muscle power was observed with increasing age. Males had consistently higher scores in measures of mechanical muscle function, whereas no gender differences were observed for functional capacity. [Conclusion] The age-related decline in functional capacity appears to accelerate when approaching 80 years of age and lower limb muscle power seems to contribute to a greater extent to the preservation of functional balance and gait capacity at that stage. Males outperform females in measures of mechanical muscle function independent of age, while the findings give no support for the existence of gender differences in functional capacity.