PLoS ONE (Jan 2019)

Submaximal exercise cardiac output is increased by 4 weeks of sprint interval training in young healthy males with low initial Q̇-V̇O2: Importance of cardiac response phenotype.

  • Robert F Bentley,
  • Joshua H Jones,
  • Daniel M Hirai,
  • Joel T Zelt,
  • Matthew D Giles,
  • James P Raleigh,
  • Joe Quadrilatero,
  • Brendon J Gurd,
  • J Alberto Neder,
  • Michael E Tschakovsky

DOI
https://doi.org/10.1371/journal.pone.0195458
Journal volume & issue
Vol. 14, no. 1
p. e0195458

Abstract

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Cardiovascular adaptations to exercise, particularly at the individual level, remain poorly understood. Previous group level research suggests the relationship between cardiac output and oxygen consumption ([Formula: see text]-[Formula: see text]) is unaffected by training as submaximal [Formula: see text] is unchanged. We recently identified substantial inter-individual variation in the exercise [Formula: see text]-[Formula: see text] relationship that was correlated to stroke volume (SV) as opposed to arterial oxygen content. Therefore we explored the effects of sprint interval training (SIT) on modulating [Formula: see text]-[Formula: see text] given an individual's specific [Formula: see text]-[Formula: see text] relationship. 22 (21±2 yrs) healthy, recreationally active males participated in a 4-week SIT (8, 20 second sprints; 4x/week, 170% of the work rate at [Formula: see text] peak) study with progressive exercise tests (PET) until exhaustion. Cardiac output ([Formula: see text] L/min; inert gas rebreathe, Finometer Modelflow™), oxygen consumption ([Formula: see text] L/min; breath-by-breath pulmonary gas exchange), quadriceps oxygenation (near infrared spectroscopy) and exercise tolerance (6-20; Borg Scale RPE) were measured throughout PET both before and after training. Data are mean Δ from bsl±SD. Higher [Formula: see text] ([Formula: see text]) and lower [Formula: see text] ([Formula: see text]) responders were identified post hoc (n = 8/group). SIT increased the [Formula: see text]-[Formula: see text] post-training in [Formula: see text] (3.8±0.2 vs. 4.7±0.2; P = 0.02) while [Formula: see text] was unaffected (5.8±0.1 vs. 5.3±0.6; P = 0.5). [Formula: see text] was elevated beyond 80 watts in [Formula: see text] due to a greater increase in SV (all P0.1). In contrast to [Formula: see text], [Formula: see text] responders are capable of improving submaximal [Formula: see text]-[Formula: see text] in response to SIT via increased SV. However, the increased submaximal exercise [Formula: see text] does not benefit exercising muscle oxygenation.