Energy Metabolism in Continuous, High-Intensity, and Sprint Interval Training Protocols With Matched Mean Intensity

Eigendorf, J, Maassen, M, Apitius, D, and Maassen, N. Energy metabolism in continuous, high-intensity, and sprint interval training protocols with matched mean intensity. J Strength Cond Res 35(11): 3104-3110, 2021-To evaluate acute physiological reactions and energy metabolism with 3 different training regimes, 7 subjects performed a high-intensity interval training (HIT), a sprint interval training (SIT), and a continuous training (CT) in a cross-over design. All training sessions were matched for relative mean intensity (50% Pmax). Stress-to-pause-ratios were chosen as 6-24 seconds (SIT) and 30-30 seconds (HIT) for interval protocols. No significant differences (significance level p <= 0.05) were found for oxygen uptake (V?o(2)), respiratory exchange ratio (RER), slope of RER (RERslope), and heart rate between the different training regimes. Lactate concentrations ([Lac]) in CT were significantly lower (p < 0.01) compared with HIT and SIT. No significant differences were found for free fatty acids ([FFA], p = 0.41) and glycerol ([GLY], p = 0.26) levels during all 3 training protocols (CT 0.27 mmol center dot L-1, SIT 0.22 mmol center dot L-1, and HIT 0.22 mmol center dot L-1). Ammonia (NH3, p > 0.05) levels did not show significant differences between the 3 training protocols during exercise phase. The comparable physiological reactions of [FFA], [GLY], and RER show that the activation of fat metabolism is not different between training regimes with different stress-to-pause-ratios. Moreover, mean intensity and time of exercise influence activation of fat metabolism. Increases in [NH3] suggest similar sources between the 3 training protocols and the need for further research concerning amino acid deamination. The better understanding of the acute reactions and changing of the energy metabolism during training sessions will help athletes in planning and executing their training sessions more efficiently and more precisely in the context of periodization.

Automated summary

The study found no significant differences in oxygen uptake, respiratory exchange ratio, heart rate, and other physiological parameters between different training regimes, but lactate concentrations were significantly lower in continuous training compared to high-intensity interval training and sprint interval training. There were no significant differences in free fatty acids and glycerol levels among all training protocols, while ammonia levels showed no significant differences during the exercise phase.