Similar Improvements in Cardiorespiratory Fitness after 12 weeks of Sprint Interval and Moderate-Intensity Continuous Training

Abstract

Sprint interval training (SIT) in the form of repeated Wingate Tests is effective for improving cardiorespiratory fitness similar to traditional moderate-intensity continuous training (MICT) despite a lower time commitment. The potential “time efficiency” of SIT is frequently touted, but Wingate-based protocols nonetheless require ∼25 min per session including warm-up, cool down and recovery intervals. A SIT protocol involving only 3 x 20 sec of all out exercise within a 10 min training session was recently shown to improve VO2peak in sedentary individuals when performed 3x/wk for 6 wk. No studies have directly compared this low-volume SIT protocol to MICT, and the potential changes induced over a longer period of training are unknown. PURPOSE: To compare changes in cardiorespiratory fitness after 6 and 12 wk of low-volume SIT and a MICT protocol requiring a five-fold greater time commitment. METHODS: Sedentary men (27 ± 9 y; BMI = 27 ± 6 kg/m2) performed either SIT or MICT (n=7 each) 3x/wk for 12 wk. SIT consisted of 3 x 20 sec all out cycle sprints against 5% body mass interspersed with 2 min rest, whereas MICT involved 45 min of continuous cycling at ∼70% maximal heart rate (HRmax). A 2 min warm-up and 3 min cool-down at 50 W were included for all sessions in both groups. Training loads were adjusted as appropriate to maintain the desired stimulus. RESULTS: Mean HR elicited during MICT and SIT was 73 ± 5% and 79 ± 3% of HRmax, respectively. VO2peak increased 11% after 6 wk of training in both groups (MICT: 31.9 ± 6.1 to 35.0 ± 6.2; SIT: 30.8 ± 7.2 to 34.2 ± 7.8 ml/kg/min, p<0.001, main effect for time). VO2peak increased further at 12 wk compared to 6 wk in both groups (to 38.0 ± 9.2 in MICT and to 36.6 ± 6.9 ml/kg/min in SIT, p<0.01, main effect for time), corresponding to a 19% improvement overall compared to pre-training in each group. CONCLUSION: A sprint interval training protocol involving 3 x 20 sec bursts of all out cycling within a 10 min training session, performed 3x/wk, improved VO2peak to the same extent as 150 min per week of moderate-intensity continuous exercise. These data attest to the potency of very intense but brief intermittent cycling exercise to improve cardiorespiratory fitness.