RESISTANT TO EXERCISE RESISTANCE? NEXT DAY POSTPRANDIAL METABOLISM UNRESPONSIVE TO CHANGES IN PHYSICAL ACTIVITY OR NEUROMUSCULAR ELECTRICAL STIMULATION

Abstract

Following a meal, metabolism is increased. If the day prior to the meal entailed exercise and physical activity (>8500 steps), this increase is even greater. However, if the day prior to the meal entailed exercise and mostly sedentary behaviors (~5000 steps), the additional increase in metabolism is absent; this phenomenon is termed Exercise Resistance. Exercise resistance may attenuate some of the health benefits of exercise, thereby potentially increasing metabolic disease risk. Neuromuscular Electrical Stimulation (NMES) stimulates skeletal muscle contraction. Approximately 100 minutes of NMES evokes an energy expenditure equivalent to 3500 steps (i.e. the difference between 8500 and 5000 steps). Therefore, we aimed to demonstrate exercise resistance and assess the influence of NMES on the effects of exercise resistance. We hypothesized that 100 minutes of NMES would attenuate exercise resistance. Metabolism following a high-calorie, high-fat meal was studied in regularly exercising adults (n=12) on separate mornings after three randomly ordered intervention days, comprising one hour of moderate-intensity treadmill exercise and either 8500 (8.5K), 5000 (5K), or 5000 steps plus 100 minutes of NMES (5K + NMES). Unexpectedly, postprandial plasma triglyceride incremental area under the curve (iAUC), the key variable for determining exercise resistance, was not different between the 8.5K (5,834 mg/dL * 240 mins), 5K (6,090 mg/dL * 240 mins), and 5K + NMES (5,356 mg/dL * 240 mins) conditions (p=0.83). Further, there was no main effect of condition for the iAUC for any of the postprandial variables: energy expenditure (p=0.39), fat oxidation (p=0.65), insulin (p=0.34), or glucose (p=0.23). Contrary to previous research, exercise coupled with decreased physical activity, with or without NMES, does not alter next-day postprandial metabolism.