Relationships between lower body strength and the energy cost of treadmill walking in a cohort of healthy older adults: a cross-sectional analysis

Walking net V ˙ O2 rises with advancing age in older women: where to go from here?

PURPOSE

Walking net V ˙ O2 tends to increase with advancing age; however, factors contributing to this relationship have not been widely described. The implications of such findings could inform targeted strategies to promote independent mobility in older adults. Herein, we evaluated the relationship between net V ˙ O2 and age at two submaximal workloads while exploring potential moderators of this relationship.

METHODS

Secondary analyses were performed on 35 older (65 ± 3 years) women who completed a battery of physical assessments including fixed-speed, non-graded and graded (+ 2.5%) treadmill walking with indirect calorimetry to determine net V ˙ O2. Maximal oxygen uptake ( V ˙ O2max), knee extensor maximal isometric voluntary contraction (MVC), peak rate of torque development (RTD), and plantar flexor range-of-motion (PFROM) were also measured.

RESULTS

Bivariate correlations showed non-graded (r = 0.403, p = 0.017) and graded (r = 0.413, p = 0.014) net V ˙ O2 were positively related to age. Notably, these relationships strengthened after adjusting for V ˙ O2max. Regression modeling showed age, RTD:MVC ratio (composite of muscle performance), and PFROM together explained 49% and 34% of the variance in non-graded and graded net V ˙ O2, respectively. Further analyses suggested knee extensor MVC moderates the relationship between non-graded net V ˙ O2 and age, accounting for 9% of the variance [ΔR2 = 0.090, F (1,31) = 4.13, p = 0.05].

CONCLUSION

These data support the premise that, in older women, walking net V ˙ O2 rises with advancing age, and additionally, the RTD:MVC ratio and PFROM are independent correlates of non-graded net V ˙ O2. Exercise interventions with a high degree of training specificity including explosive, velocity-based elements may promote independent mobility in older women.

Value of the 3-min walk test and its association with motor functions in older adults

BACKGROUND

The 3-min walk test (3MWT) has been used in the clinical setting.

OBJECTIVE

To present the 3MWT value and investigate its association with motor and respiratory functions of healthy older adults.

METHODS

Two hundred six older adults and 27 younger adults were enrolled. The 3MWT was assessed by the walking distance within 3 min. Knee extension muscle strength (KEMS), 5-repetition sit-to-stand (5 R-STS), Timed Up and Go (TUG), forced vital capacity (FVC), forced expiratory volume 1.0 (FEV1.0), maximal expiratory pressure (MEP), and maximal inspiratory pressure (MIP) were measured. The 3MWT distance was examined by age group (18-39, 60-69, 70-79, and 80-89 years). A multivariate regression analysis investigated the association between 3MWT and motor function test.

RESULTS

The 3MWT values in each age group were 273-385, 233-414, 93-351, and 171-345 m for men and 215-375, 220-349, 198-325, and 174-332 m for women respectively. The 3MWT values were correlated with age, body mass index (BMI), KEMS, 5 R-STS, TUG, FVC, FEV1.0, MEP, and MIP. On the multivariate regression analysis, 3MWT was significantly associated with BMI (standard beta = -0.18; 95% confidence interval [CI], -3.20 to 0.83), KEMS (standard beta = 0.37; 95% CI, 0.06-0.13), 5 R-STS (standard beta = -0.13; 95% CI, -5.70 to -0.13), and TUG (standard beta = -0.36; 95% CI, -17.15 to -7.73) in older adults (adjusted R2 = 0.47).

CONCLUSIONS

The 3MWT distance decreased with age and was associated with motor and respiratory functions. No range trends were observed among groups. Our findings suggest that 3MWT reflects functional capacity.