Associations Of Muscle Strength Activity And Aerobic Activity With Changes In Cardiorespiratory Fitness Levels Over Time.

PURPOSE: Studies have shown engaging in moderate to vigorous-intensity aerobic physical activity leads to maintenance of or increases in cardiorespiratory fitness (CRF). However, the contribution of strength training along with aerobic physical activity and CRF has rarely been explored in a large cohort of community-dwelling adults. PURPOSE: To investigate the associations between muscle strengthening, aerobic physical activity, and CRF at baseline and longitudinally among adults enrolled in the Cooper Center Longitudinal Study (CCLS). METHODS: Participants underwent cardiovascular fitness assessment, physical examination, and medical history including information regarding leisure-time aerobic and strength activities, after providing written informed consent that was approved by the Cooper Institute’s IRB. We included 3,579 apparently healthy men and women who had at least 4 visits to the Cooper Clinic (Dallas, TX). The association of the independent variables with CRF was examined using mixed effects regression while controlling for covariates (e.g., age, sex). RESULTS: Participants were primarily men (85.3%), their average age at baseline was 46.9 years (SD = 8.5), and the mean time between clinic visits was 2.1 years (SD = 1.8). At baseline, higher aerobic and muscle strengthening activities were each independently related to higher CRF levels. Specifically, an increase in aerobic physical activity of 1- metabolic equivalent of task (MET) hour per week was cross-sectionally related to a 0.029 (95% CI 0.026, 0.031) MET higher CRF. Similarly, 1-MET hour per week more muscle strengthening activity was associated with 0.046 (95%CI 0.035, 0.057) MET higher CRF at baseline. In longitudinal analysis controlling for baseline values and covariates, a 1-MET hour per week increase in aerobic activity was related to a 0.008 (95%CI 0.008, 0.009) MET increase in CRF during follow-up (median of 9.1 years). Additionally, a 1-MET hour per week increase in strength activities was associated with a 0.020 (95%CI 0.016, 0.023) increase in CRF during follow-up. CONCLUSIONS: Aerobic and muscle strengthening activities are each significantly associated with CRF levels among adults.