Wang, T. Y., Lee, M. M., & Chan, K. H.(2013). The adaptation of short-term high-intensity interval training on exercise-induced stresses. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 2146.

This study compared the responses of blood levels of thiobarbituric acid reactive substances (TBARS), creatine kinase, and cortisol between the first and last high-intensity interval training sessions over two weeks in healthy males (N = 8). Ss performed six sessions of high-intensity interval training (7 bouts of a 4-minute interval at 90% VO2max, 2-minute rest between intervals) on a treadmill three days per week for two weeks. Before and during the first and the sixth sessions, Ss' blood samples were collected to measure the concentrations or activities of TBARS, creatine kinase, and cortisol.

In the first high-intensity interval training session, TBARS at 0 hours and 1 hour, creatine kinase at 0 hours, 1 hour, and 2 hours, as well as cortisol at 0 hours were significantly higher than at rest In the sixth high-intensity interval training session, TBARS at 0 hours and 1 hour as well as creatine kinase at 0 hours, 1 hour, and 2 hours were still significantly higher than at rest. Cortisol did not change after the sixth high-intensity interval training session. There were no significant differences at the same time points between the first and sixth training session, indicating no exercise adaptation of these markers.

Implication. High-intensity interval-training induced oxidative, mechanical, and metabolic stresses within training sessions. Over two-weeks (short-term), no exercise-induced stress adaptations were evidenced.

[Editor's note: An interval duration of four minutes at less than VO2max is not a common high-intensity interval training format. Shortening the work interval and increasing the work intensity to at least greater than VO2max leads to quick and remarkable adaptations. In this study, the 90% VO2max work intensity over four minutes is at the very lowest threshold for any high-intensity interval training effects to occur in a brief time.]

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