Slow-Paced Breathing during Recovery from Sprint Interval Training: A Randomized Controlled Trial

Background: Breathing practices for athletes are gaining popularity due to their potential benefits for recovery, performance enhancement, and well-being. In particular, slow-paced breathing is believed to increase sympatho-vagal balance and relaxation, potentially supporting adaptive processes induced by training interventions. Sprint interval training, by contrast, elicits a strong stress response characterized by low heart rate variability, catecholamine release, and delayed performance recovery. This randomized controlled trial, therefore, examined the effects of slow-paced breathing during the recovery phase of sprint interval training. It was hypothesized that the breathing intervention would enhance recovery, as indicated by cardiac control and sleep metrics, ultimately leading to greater performance gains.Results: Thirty-four participants completed four weeks of sprint interval training. The supervised training led to significant improvements in maximal power decrements (-8.26%, 95% CI [-11.48, -5.04], p < 0.001) and overall work (8.84 kJ/kg, 95% CI [4.58, 13.1], p < 0.001), while no significant changes in heart rate variability or heart rate recovery were found (p > 0.05). Although the training was perceived as very strenuous, subjective exertion decreased over time. Slow-paced breathing had no significant effect on performance or recovery metrics. Unexpectedly, nocturnal heart rate showed a slight increase over time in the slow-paced breathing group (+3.1 bpm, 95% CI [0.47, 5.72], p < 0.05) compared to the control group.Conclusion: Over four weeks of daily practice, slow-paced breathing did not yield additional positive adaptations during an effective, highly demanding sprint interval training program. While previous studies have suggested potential benefits of breathing practices for athletes, the present study does not support these findings. It is one of the first randomized training interventions to examine slow-paced breathing in a well-controlled, supervised high-intensity interval training program based on relevant performance outcomes. Slow-paced breathing, as applied in the present study, cannot be recommended as an effective recovery strategy for sprint interval training; however, this does not preclude potential benefits under different conditions or protocols.