Acute Physiological Response to Aerobic Short-Interval Training in Trained Runners

Purpose: To analyze the acute physiological response to aerobic short- interval training ( AESIT) at various high- intensity running speeds. A minor anaerobic glycolytic energy supply was aimed to mimic the characteristics of slow continuous runs. Methods: Eight trained male runners ( maximal oxygen uptake [ VO2max] 55.5 +/- 3.3 mL +/- kg- 1 +/- min- 1) performed an incremental treadmill exercise test ( increments: 0.75 km +/- h- 1 +/- min- 1). Two lactate turn points ( LTP1, LTP2) were determined. Subsequently, 3 randomly assigned AESIT sessions with high- intensity running- speed intervals were performed at speeds close to the speed ( v) at VO2max ( vVO2max) to create mean intensities of 50%, 55%, and 60% of vLTP1. AESIT sessions lasted 30 min and consisted of 10- s work phases, alternated by 20- s passive recovery phases. Results: To produce mean velocities of 50%, 55%, and 60% of vLTP1, running speeds were calculated as 18.6 +/- 0.7 km/ h ( 93.4% vVO2max), 20.2 +/- 0.6 km/ h ( 101.9% vVO2max), and 22.3 +/- 0.7 km/ h ( 111.0% vVO2max), which gave a mean blood lactate concentration ( La) of 1.09 +/- 0.31 mmol/ L, 1.57 +/- 0.52 mmol/ L, and 2.09 +/- 0.99 mmol/ L, respectively. La at 50% of vLTP1 was not significantly different from La at vLTP1 ( P =.8894). Mean VO2 was found at 54.0%, 58.5%, and 64.0% of VO2max, while at the end of the sessions VO2 rose to 71.1%, 80.4%, and 85.6% of VO2max, respectively. Conclusion: The results showed that AESIT with 10- s work phases alternating with 20 s of passive rest and a running speed close to vVO2max gave a systemic aerobic metabolic profile similar to slow continuous runs.