2-week Microcycles Of Aerobic And Resistance Exercise Elicit Different Health Improvements In Untrained Healthy Adults

Physical inactivity and low cardiorespiratory fitness (CRF) threaten public health, contributing to rising rates of chronic disease. Aerobic training (AT) and resistance training (RT) are effective exercise modalities for improving health, but intra-individual variation in exercise response affects the degree of health improvement and exercise adherence. Therefore, identifying which exercise modality provides the most initial health benefits may guide initial exercise recommendations for untrained individuals. PURPOSE: To investigate the effect of 2-week aerobic and resistance training microcycles on anthropometrics, resting cardiovascular (CV) function, muscle function, and CRF in healthy untrained adults. METHODS: In a randomized crossover design study, twelve healthy adults (n = 12, 28.1 ± 9.3 yrs) engaged in 7 sessions (40-minutes·session) of either AT or RT with a 14-day washout in-between. Anthropometrics, resting CV function, muscle performance, and CRF were assessed at baseline and after each microcycle. Paired sample t-tests were used to determine the effect of time and condition. RESULTS: Following AT, there was an increase in VO2peak (M diff = 2.9 mL·kg-1·min-1, p = 0.046, d = 0.65) and a decrease in central systolic blood pressure (M diff = -7.7 mmHG, p = 0.005, d = 0.996), central diastolic blood pressure (M diff = -5.5 mmHG, p = 0.032, d = 0.71), peripheral systolic blood pressure (M diff = -7.0 mmHG, p = 0.045, d = 0.65), peripheral diastolic blood pressure (M diff = -4.6 mmHG, p = 0.034, d = 0.70), and mean arterial pressure (M diff = -6.8 mmHG, p = 0.015, d = 0.84), compared to baseline. Following RT, there were increases in peak torque of knee flexion (M diff = 16.4 N·m, p = 0.039, d = 0.68) and estimated hamstring type 2 fiber proportion (M diff = 9.3%, p = 0.043, d = 0.66), compared to baseline. No other anthropometric, performance, or CV changes were observed following AT or RT (all, p > 0.05). Despite these time effects, there were no significant differences between conditions. CONCLUSIONS: A 2-week microcycle of AT improved CRF and resting CV function while a 2-week microcycle of RT improved muscle strength and estimated muscle fiber profile in untrained healthy individuals. Notably, a 2-week microcycle of RT was insufficient to improve resting CV function in untrained healthy individuals. MARC-ACSM Early Stage Investigator Award