Resistance exercise reduces muscular substrates in women

The purpose of this investigation was to examine the influence of an acute bout of resistance exercise (RE) on intramuscular triglyceride (IMTG) and muscle glycogen concentrations and intracellular signaling in women with high body fat content. Six overweight women with a high percent body fat (age 29 +/- 3 yr; BMI 28 +/- 3 kg/m(2), body fat 38 +/- 4%) performed 6 sets of 10 repetitions of knee extension exercise at 70% 1RM. Muscle biopsies were obtained from the vastus lateralis before, 1 min after (POST1), and 2 h after (POST2) exercise. Acute RE reduced (p<0.05) IMTG content similar to 40% at POST1 and POST2 (75 +/- 5; 45 6; 50 10 mmol/kg/dry wt). Muscle glycogen was also reduced (p < 0.05) similar to 25% at POST1 and remained lower at POST2 (317 +/- 14; 241 +/- 30; 235 +/- 26 mmol/kg/dry wt). ERK1/2, SAPK/JNK, and p38 phosphorylation were increased (p<0.05) similar to 2-3-fold at POST1 and ERK1/2 remained elevated and POST2 whereas SAPK/JNK and p38 returned to basal levels. AMPK alpha phosphorylation was unchanged in response to RE. These results show that both IMTG and muscle glycogen stores serve as an important energy source during RE in overweight women and the MAP kinase signaling response to RE is not compromised by high levels of body fat.