Determining the Importance of Meeting Muscle-Strengthening Activity Guidelines: Is the Behavior or the Outcome of the Behavior (Strength) a More Important Determinant of All-Cause Mortality?

Abstract

OBJECTIVE: To determine whether the behavioral participation in muscle-strengthening activity (MSA) or the strength outcome produces the largest reduction in all-cause mortality risk. PATIENTS AND METHODS: The 1999-2002 National Health and Nutritional Examination Survey was used, with follow-up of up to 12.6 years (mean, 9.9 years) (N=2773 adults aged ≥50 years). Participants were placed into 4 groups based on 2 dichotomously categorized variables: lower-extremity strength (LES) of the knee extensors (top quartile) and adherence to MSA guidelines (≥2 MSA sessions per week). Approximately 21% of the population died during follow-up. RESULTS: Compared with individuals not meeting MSA guidelines and not in top quartile for LES, the adjusted hazard ratios (HRs) and 95% CIs were as follows: (1) meets MSA guidelines but not in top quartile for LES (HR=0.96; 95% CI, 0.63-1.45; P=.84), (2) in top quartile for LES but does not meet MSA guidelines (HR=0.54; 95% CI, 0.42-0.71; P<.001), and (3) in top quartile for LES and meets MSA guidelines (HR=0.28; 95% CI, 0.12-0.66; P=.005). Further analyses revealed that individuals in the top quartile for LES who also met MSA and moderate to vigorous physical activity guidelines were at even further reduced risk for premature all-cause mortality (HR=0.23; 95% CI, 0.08-0.61; P=.005). CONCLUSION: These results demonstrate that muscle strength seems to be more important than the behavioral participation in MSA for reducing the risk of premature all-cause mortality.