Muscle-Strengthening Activity and Motivating Factors by Age Group and Cancer History

ABSTRACT Introduction Muscle-strengthening activity is beneficial for mitigating age- and cancer-related muscle loss. This study aimed to describe muscle-strengthening activity among US adults, including by age group and cancer history, and examine motivating factors for exercise and their associations with meeting muscle-strengthening activity recommendations (≥2 d·wk −1 ). Methods Nationally representative data from the Health Information National Trends Survey collected in 2012 and 2019 were analyzed, inclusive of 9068 participants. Participants reported numbers of days of muscle-strengthening activity per week and how much four motivating factors (appearance, enjoyment, guilt, and pressure from others) reflect why they start or continue exercising regularly. Analyses included descriptive statistics for prevalence and Poisson logistic regression. Results Overall, 34.4% reported engaging in muscle-strengthening activity ≥2 d·wk −1 . Among those aged ≥65 yr, 28.6% met muscle-strengthening activity recommendations compared to 42% of those aged 18–35 yr. A lower percentage of adults with cancer histories reported muscle-strengthening activity at least 2 d·wk −1 compared to those without (26.7% vs 35.5%). Enjoyment (incidence rate ratio (IRR) range: 1.9–3.8) and guilt (IRR range: 1.7–2.1) were significantly associated with meeting muscle-strengthening activity recommendations, regardless of age and cancer history. Concern over appearance was significantly associated with meeting muscle-strengthening activity recommendations among those aged ≥50 yr (IRR range: 1.2–1.6). Pressure from others was not associated with meeting the recommendations. Conclusion Less than half of US adults participate in muscle-strengthening activity, with significantly lower participation among older adults and adults with cancer histories. Motivating factors for exercise that are associated with meeting the muscle-strengthening activity recommendations differ in some respects from those associated with aerobic physical activity, highlighting the need for future research to understand motivation tailored to specific types of exercise modalities. Enjoyment is a strong motivating factor associated with meeting muscle-strengthening activity recommendations and should be targeted in exercise promotion efforts.