Adipose tissue lipolysis is increased during a repeated bout of aerobic exercise

The goal of the study was to examine whether Lipid mobilization from adipos e tissue undergoes changes during repeated bouts of prolonged aerobic exerc ise. Microdialysis of the subcutaneous adipose tissue was used for the asse ssment of lipolysis; glycerol concentration was measured in the dialysate l eaving the adipose tissue. Seven male subjects performed two repeated bouts of 60-min exercise at 50% of their maximal aerobic power, separated by a 6 0-min recovery period. The exercise-induced increases in extracellular glyc erol concentrations in adipose tissue and in plasma glycerol concentrations were significantly higher during the second exercise bout compared with th e first (P < 0.05). The responses of plasma nonesterified fatty acids and p lasma epinephrine were higher during the second exercise bout, whereas the response of norepinephrine was unchanged and that of growth hormone lower. Plasma insulin levels were lower during the second exercise bout. The resul ts suggest that adipose tissue lipolysis during aerobic exercise of moderat e intensity is enhanced when an exercise bout is preceded by exercise of th e same intensity and duration performed 1 h before. This response pattern i s associated with an increase in the exercise-induced rise of epinephrine a nd with lower plasma insulin values during the repeated exercise bout.