Effect of combined thermal and electrical muscle stimulation on cardiorespiratory fitness and adipose tissue in obese individuals

Abstract

Background

To better understand how prolonged electrical muscle stimulation can improve cardiorespiratory risk markers in obese subjects, we investigated the effect of prolonged combined thermal and electrical muscle stimulation (cTEMS) on peak oxygen consumption (VO_2peak) and body composition with subsequent lipolytic and mitochondrial activity in adipocytes.

Methods and results

Eleven obese (BMI ≥ 30 kg/m²) individuals received cTEMS in three 60-minute sessions per week for 8 weeks. Activity levels and dietary habits were kept unchanged. Before and after the stimulation period, functional capacity was assessed by VO_2peak, and body composition was analysed. Lipolytic activity was determined in abdominal adipose tissue by 24 hours of microdialysis on a sedentary day, and adipose tissue biopsies were taken for the gene expression analysis. Eight weeks of cTEMS significantly increased VO_2peak from 28.9 ± 5.7 to 31.7 ± 6.2 ml/kg/min (p < 0.05), corresponding to an average increase of 1.2% per week. Oxygen uptake and work capacity also increased at the anaerobic threshold. Mean microdialytic glycerol concentration over 24 hours, an index of sedentary lipolytic activity, increased from 238 ± 60 to 306 ± 55 µM (p < 0,0001), but no significant changes in body composition were observed. In addition, PGC-1α and carnitine-palmitoyltransferase-2 mRNAs were significantly upregulated in subcutaneous abdominal adipose tissue.

Conclusions

In obese individuals with unchanged lifestyles, 8 weeks of cTEMS significantly improved functional capacity towards a higher fatigue resistance. This increase also gave rise to elevated lipolytic activity and increased mitochondrial activity in abdominal adipose tissue.