A six week modified sprint interval training program incorporating extended exercise bouts does not increase maximal cardiac output

Alan R. Smith, The University of Western Ontario

Abstract

Sprint interval training (SIT) improves maximal oxygen uptake (V̇O_2max) and exercise performance but not maximal cardiac output (Q̇_max). The brevity of typical SIT bouts (30-seconds) might hinder improvements in Q̇_max. The purpose of this study was to determine whether extended duration SIT (up to 45 second bouts) improves Q̇_max. Pre-/Post-SIT (or control) V̇O_2max, Q̇_max, maximum stroke volume (SV_max), maximum heart rate, arterial-mixed venous oxygen difference, and 5-minute run distance were measured. SIT progressed from 4x30s to 7x45s “all-out” efforts (4 min recovery) over 6 wk (3x/wk) on a manually driven treadmill. Following SIT, V̇O_2max improved (pre-=3.6±0.8 vs post=3.8±0.8 L·min^-1; p=0.012). Increases in Q̇_max (pre-= 26.13±5.09 vs post=27.10±4.82 L·min^-1; p=0.166) and SV_max (pre-= 138±27 vs post=144±28 mL·beat^-1; p=0.095) were not significant. These data suggest 6 wk of extended SIT bouts (up to 45 s) does not increase Q̇_max significantly and the observed increase in V̇O_2max was due primarily to non-significant improvements in Q̇_max and SV_max.