Vo2max Improvement After High-intensity Interval Training Is Not High-intensity Dependent In Metabolic Syndrome Patients.

Abstract

It has been described that a linear dose-response between cardiorespiratory fitness (CRF) and exercise dose is not universal in metabolic syndrome (MetS) patients. Exercise prescription compliance analysis can provide insight into the study of the relationship between exercise dose (intensity and volume), with CRF improvements.PURPOSE: To analyze the influence of exercise prescription adherence on CRF improvement with a high-intensity interval training (HIIT) in patients with MetS. METHODS: Eighty middle-aged patients with MetS participated in a 16-week HIIT (3 days per week). Before and after training, VO2max was assessed using a graded exercise test to exhaustion (GXT). Training sessions consisted of 10 min warm-up at 70%HRmax followed by 4-min intervals at 90%HRmax interspersed with 3-min recovery at 70%HRmax and a 5-min cool-down. Exercise time and heart rate were recorded in every training session. From these records, at the end of the training, exercise mean heart rate (HRmean), total exercise time (Timetotal), and time spent at intensities above 70% HRmax (Time > 70%), 80% HRmax (Time > 80%), 90% HRmax (Time > 90%) were calculated for all attended sessions. VO2max change after HIIT was analyzed by paired T-test. Stepwise multiple linear regression was used to analyze the influence of exercise prescription compliance in VO2max gains. RESULTS: VO2max improved after training (11.9 ± 13.5%; P < 0.001). TimeTot, Time > 80%, and Time > 70%, but not HRmean, and Time > 90%, correlated with VO2max improvement. Stepwise linear regression equation revealed that the most predictive variable was training time at intensities above 70% HRmax to predict VO2max gains. CONCLUSIONS: In patients with MetS, there is no evident linear dose-response between exercise intensity and VO2max gains with HIIT. Time spent at moderate to high-intensities (i.e., >70% of HRmax) and not the time spent at higher intensities (i.e., >90% HRmax) predicted appropriately VO2max changes. Therefore, a strict exercise prescription compliance to the high-intensity intervals is not the main variable associated with the CRF improvement in patients with metabolic syndrome. Instead, exercise time spent above a threshold of exercise intensity in the moderate-intensity dominion seems to be the main predictor of VO2max improvement in this population.