Chronic effects of high-intensity interval training on postprandial lipemia in healthy men

The aim of this study was to determine the chronic (>= 72 h post-xercise) effects of high-intensity interval training (HIIT) on postprandial lipemia and metabolic markers in healthy volunteers. Eight physically active young men (mean +/- SD: age 22 +/- 3 yr, height 1.77 +/- 0.07 m, body mass 67.7 +/- 6.2 kg) underwent two 6-h mixed-eal tolerance tests and resting vastus lateralis muscle biopsies before the first session and >= 72 h after the final session of 4 wk of HIIT [16 sessions in total; 10 x 60-s bouts of cycling at 90% maximal oxygen uptake ((v) over dot O-2max), interspersed with 60-s intervals at 45% (v) over dot O-2max]. Arterialized and deep venous blood samples from across the forearm, brachial artery blood flow measurements, and whole-body indirect calorimetry data were obtained before, and at regular intervals for 6 h after, consumption of a standardized mixed meal. The main findings revealed that, when assessed >= 72 h postexercise, postprandial free fatty acid (FFA) uptake across the forearm was increased in response to exercise training (P = 0.025). However, 4 wk of HIIT did not alter fasting or postprandial circulating triglyceride concentrations or their tissue uptake, despite a 10.2% +/- 7.7% improvement in (v)over dotO(2max) (P = 0.004). Protein content of adipose triglyceride lipase in the vastus lateralis at rest was reduced by 25% +/- 21% (P = 0.01). Collectively, these findings suggest that 4 wk of HIIT enhances postprandial clearance of FFA when assessed >= 72 h postexercise but does not confer persisting (training) adaptations in postprandial triglyceridemia. NEW & NOTEWORTHY When assessed >= 72 h after the last exercise session, 4 wk of high-intensity interval training (HIIT) did not improve triglyceridemia but enhanced free fatty acid uptake into muscle with a concurrent reduction in skeletal muscle adipose triglyceride lipase protein content. This suggests that previously reported acute reductions in postprandial triglyceridemia following a single bout of HIIT do not translate to sustained improvements after 4 wk of HIIT, supporting the concept of frequent exercise for the maintenance of lipemic control.