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 [VO(2max)] 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 VO(2max) (vVO(2max)) 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% vVO(2max)), 20.2 ± 0.6 km/h (101.9% vVO(2max)), and 22.3 ± 0.7 km/h (111.0% vVO(2max)), 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 VO(2) was found at 54.0%, 58.5%, and 64.0% of VO(2max), while at the end of the sessions VO(2) rose to 71.1%, 80.4%, and 85.6% of VO(2max), 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 vVO(2max) gave a systemic aerobic metabolic profile similar to slow continuous runs.