Short-term high-intensity interval and continuous moderate-intensity training improve maximal aerobic power and diastolic filling during exercise

Purpose This study examined the effects of short-term high-intensity interval training (HIT) and continuous moderate-intensity training (CMT) on cardiac function in young, healthy men. Methods Sixteen previously untrained men (mean age of 25.1 +/- 4.1 years) were randomly assigned to HIT and CMT (n = 8 each) and assessed before and after six sessions over a 12-day training period. HIT consisted of 8-12 intervals of cycling for 60 s at 95-100 % of pre-training maximal aerobic power ((V) over dotO(2max)), interspersed by 75 s of cycling at 10 %(V) over dotO(2max). CMT involved 90-120 min of cycling at 65 % pre-training (V) over dotO(2max). Left ventricular (LV) function was determined at rest and during submaximal exercise (heart rate similar to 105 bpm) using two-dimensional and Doppler echocardiography. Results Training resulted in increased calculated plasma volume (PV) in both groups, accompanied by improved (V) over dotO(2max) in HIT (HIT: from 39.5 +/- 7.1 to 43.9 +/- 5.5 mL kg(-1) min(-1); CMT: from 39.9 +/- 5.9 to 41.7 +/- 5.3 mL kg(-1) min(-1); P < 0.001). Resting LV function was not altered. However, increased exercise stroke volume (P = 0.02) and cardiac output (P = 0.02) were observed, secondary to increases in end-diastolic volume (P < 0.001). Numerous Doppler and speckle tracking indices of diastolic function were similarly enhanced during exercise in both training groups and were related to changes in PV. Conclusion Short-term HIT and CMT elicit rapid improvements in (V) over dotO(2max) and LV filling without global changes in cardiac performance at rest.