Interrupting prolonged sedentary behavior with periodic interval exercise : effects on postprandial lipemia and fat oxidation

High levels of postprandial lipemia are considered an independent risk factor for cardiovascular disease, one of the leading causes of death worldwide. An acute bout of exercise has been shown to attenuate the plasma triglycerides response the next morning following a meal high in fat. However, evidence suggests that this benefit of exercise is not always observed when time spent sitting is drastically increased. This phenomenon is being described as exercise resistance, where the metabolic benefits of exercise do not manifest. A previous study found that breaking up prolonged sitting with inertial load ergometer (ILE) (5 x 4second sprints with 45 seconds rest) sprints every hour for 8 hours attenuated postprandial lipemia in healthy adults. The purpose of this study is to determine if these benefits can still be gained with less frequent intervals of breaking up induced sedentary behavior (monitored by restricting step count to <4500 steps/day) using the same exercise protocol. In a repeated measure, crossover design, eight healthy, young adults (four men and four women) participated in three trials which lasted a total of four days each: two controlled activity days, one intervention day, and a high fat tolerance test (HFTT) on day 4. The controlled activity days required participants to take less than 4500 steps each day to induce exercise resistance. The interventions consisted of taking less than 4500 steps/d with no exercise (SIT), with 4 bouts of ILE sprints (SIT + 4), and with 2 bouts of ILE sprints (SIT + 2) spread throughout the day. The outcome measure was postprandial metabolism following a high fat meal. During the HFTT, plasma triglycerides and expired air were collected hourly for four hours after meal ingestion. Incremental and total area under the curve (AUC) for plasma triglycerides concentration were calculated and indirect calorimetry was performed to quantify fat oxidation. No differences (P>0.05) were found between interventions for plasma triglycerides total and incremental AUC or fat oxidation. These results suggest 2 or 4 bouts of ILE sprint exercise breaking up 8-hours of sitting are not enough to ameliorate the postprandial responses to a high fat meal the next day.