Cumulative effects of training at different weekly energy expenditures on cardiorespiratory fitness and markers of metabolic syndrome in STRRIDE-Extension

Assess the cumulative effects of different weekly exercise energy expenditures, with similar total program volume and intensity, on cardiorespiratory fitness (CRF) and metabolic syndrome (MetS). Following the 9-mo Studies of a Targeted Risk Reduction Intervention through Defined Exercise (STRRIDE) trial, 22 participants continued exercise training for 6-24 mo in one of two groups: <i>1</i>) low-amount/vigorous-intensity (LAVI; <i>n</i> = 14): 14 kcal/kg/wk (KKW) at 65%-80% peak V̇o₂ and <i>2</i>) high-amount/vigorous-intensity (HAVI; <i>n</i> = 8): 23 KKW at 65%-80% peak V̇o₂. Outcomes included absolute (AV̇o₂) and relative peak oxygen consumption (RV̇o₂), body fat percentage, waist circumference, HDL-C, triglycerides, fasting glucose, insulin sensitivity index (S_I), and modified MetS <i>z</i> score. Group comparisons were made at equivalent and differential timepoints with similar total exercise volumes. S_I improvements were greater in HAVI compared with LAVI at the LAVI 21-mo/HAVI 15-mo contrast (mean difference ± SD: 2.13 ± 0.68 mU/L/min, <i>P</i> = 0.008). AV̇o₂ and RV̇o₂ improvements were greater in HAVI at both the LAVI 21-mo/HAVI 15-mo contrast (model estimate [95% CI]: 0.21 [0.01, 0.40] L/min, <i>P</i> = 0.038 and 3.05 [0.14, 5.96] mL/kg/min, <i>P</i> = 0.041), respectively, and the LAVI 33-mo/HAVI 21-mo contrast (0.25 [0.04, 0.45] L/min, <i>P</i> = 0.022 and 3.21 [0.10, 6.32] mL/kg/min, <i>P</i> = 0.044). These AV̇o₂ contrasts remained significant after adjusting for age and sex. Adherence declined over time. When cumulative exercise volumes were similar, body composition and MetS markers adapted similarly between groups. However, continued training at greater weekly volumes of vigorous exercise resulted in more substantial CRF and S_I improvements compared with lesser weekly volumes. Findings suggest factors beyond total energy expenditure-such as exercise frequency or duration-may modulate some longitudinal health improvements.<b>NEW & NOTEWORTHY</b> This exploratory analysis investigated longitudinal effects of accumulating similar total exercise program volumes at different weekly exercise energy expenditures on cardiorespiratory fitness and metabolic syndrome measures over months to years. In general, adaptations are similar; however, factors other than total energy cost-such as exercise frequency or duration-may modulate longitudinal improvements in cardiorespiratory fitness and skeletal muscle insulin sensitivity over 33 mo of training among sedentary adults with overweight or obesity and dyslipidemia.