Twelve weeks of sprint interval training increases peak cardiac output in previously untrained individuals

Introduction Sprint interval training (SIT), characterized by brief bouts of 'supramaximal' exercise interspersed with recovery periods, increases peak oxygen uptake ((V) over dotO(2peak)) despite a low total exercise volume. Per the Fick principle, increased (V) over dotO(2peak) is attributable to increased peak cardiac output ((Q) over dot(peak)) and/or peak arterio-venous oxygen difference (a-vO(2diff)). There are limited and equivocal data regarding the physiological basis for SIT-induced increases in (V) over dotO(2peak), with most studies lasting <= 6 weeks. Purpose To determine the effect of 12 weeks of SIT on (Q) over dot(peak), measured using inert gas rebreathing, and the relationship between changes in (Q) over dot(peak) and (V) over dotO(2peak). Methods 15 healthy untrained adults [6 males, 9 females; 21 +/- 2 y (mean +/- SD)] performed 28 +/- 3 training sessions. Each session involved a 2-min warm-up at 50 W, 3 x 20-s 'all-out' cycling bouts (581 +/- 221 W) interspersed with 2-min of recovery, and a 3-min cool-down at 50 W. Results Measurements performed before and after training showed that 12 weeks of SIT increased (Q) over dot(peak) (17.0 +/- 3.7 vs 18.1 +/- 4.6 L/min, p = 0.01, partial eta(2) = 0.28) and (V) over dotO(2peak) (2.63 +/- 0.78 vs 3.18 +/- 1.1 L/min, p < 0.01, partial eta(2) = 0.58). The changes in these two variables were correlated (r(2) = 0.46, p < 0.01). Calculated peak a-vO(2diff) also increased after training (154 +/- 22 vs 174 +/- 23 ml O-2/L; p < 0.01) and was correlated with the change in (V) over dotO(2peak) (r(2) = 0.33, p = 0.03). Exploratory analyses revealed an interaction (p < 0.01) such that (Q) over dot(peak) increased in male (+ 10%, p < 0.01) but not female participants (+ 0.6%, p = 0.96), suggesting potential sex-specific differences. Conclusion Twelve weeks of SIT increased (Q) over dot(peak) by 6% in previously untrained participants and the change was correlated with the larger 21% increase in (V) over dotO(2peak).

Automated summary

The study found that 12 weeks of Sprint Interval Training (SIT) increased peak cardiac output ((Q)dot(peak)) by 6% in previously untrained participants, and the change was correlated with a 21% increase in peak oxygen uptake ((V)dotO(2peak)). Additionally, there was a significant increase in peak arterio-venous oxygen difference (a-vO2diff) after the training period.