Cumulative Effects of Training at Different Weekly Energy Expenditures on Cardiorespiratory Fitness and Markers of Metabolic Syndrome in STRRIDE-Extension.

PURPOSE: 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). METHODS: Following the 9-month STRRIDE trial, 22 participants continued exercise training for 6-24 months in one of two groups: 1) Low-Amount/Vigorous-Intensity (LAVI; n=14): 14 kcal/kg/week (KKW) at 65-80% peak V̇ O₂; 2) High-Amount/Vigorous-Intensity (HAVI; n=8): 23 KKW at 65-80% peak V̇ O₂. Outcomes included absolute (AV̇ O₂) and relative peak oxygen consumption (RV̇ O₂), body fat percentage, waist circumference, HDL-C, triglycerides, fasting glucose, insulin sensitivity index (SI), and modified MetS z-score. Group comparisons were made at equivalent and differential timepoints with similar total exercise volumes. RESULTS: SI improvements were greater in HAVI compared to LAVI at the LAVI 21- month/HAVI 15-month contrast (mean difference±SD: 2.13±0.68 mU/L/min, p=0.008). AV̇ O₂ and RV̇ O₂ improvements were greater in HAVI at both the LAVI 21-month/HAVI 15-month contrast (model estimate [95% CI]: 0.21 [0.01, 0.40] L/min, p=0.038 and 3.05 [0.14, 5.96] mL/kg/min, p=0.041) and the LAVI 33-month/HAVI 21-month contrast (0.25 [0.04, 0.45] L/min, p=0.022 and 3.21 [0.10, 6.32] mL/kg/min, p=0.044). These AV̇ O₂ contrasts remained significant after adjusting for age and sex. Adherence declined over time. CONCLUSION: When cumulative exercise volumes were similar, body composition and MetS markers adaptated similarly between groups. However, continued training at greater weekly volumes of vigorous exercise resulted in more substantial CRF and SI improvements compared to lesser weekly volumes. Findings suggest factors beyond total energy expenditure-such as exercise frequency or duration-may modulate some longitudinal health improvements.