Physiological responses during intermittent running exercise differ between outdoor and treadmill running

{The aim of this study was to compare the physiological responses during 15 min of intermittent running consisting of 30 s of high-intensity running exercise at maximal aerobic velocity (MAV) interspersed with 30 s of passive recovery (30-30) performed outdoor versus on a motorized treadmill. Fifteen collegiate physically active males (age, 22 +/- 1 years old; body mass, 66 +/- 7 kg; stature, 176 +/- 06 cm; weekly training volume, 5 +/- 2 h.week(-1)), performed the Fitness Intermittent Test 45-15 to determine maximal oxygen uptake ((V)over dotO(2max)) and MAV and then completed in random order 3 different training sessions consisting of a 30-s run/30-s rest on an outdoor athletic track (30-30 Track) at MAV; a 30-s run/30-s rest on a treadmill (30-30 Treadmill) at MAV; a 30-s run/30-s rest at MAV+15% (30-30 + 15% MAV Treadmill). Oxygen uptake ((V)over dotO(2)), time above 90%(V)over dotO(2max) (t90%(V)over dotO(2max)), and rating of perceived exertion (RPE) were measured during each training session. We observed a statistical significant underestimation of (V)over dotO(2) (53.1 +/- 5.4 mL.kg(-1).min(-1) vs 49.8 +/- 6.7 mL.kg(-1).min(-1), -6.3%