Blood volume expansion does not explain the increase in peak oxygen uptake induced by 10 weeks of endurance training

Øyvind Skattebo; Anders Wold Bjerring; Marius Auensen; Sebastian Imre Sarvari; Kristoffer Toldnes Cumming; Carlo Capelli; Jostein Hallén

doi:10.1007/s00421-020-04336-2

Blood volume expansion does not explain the increase in peak oxygen uptake induced by 10 weeks of endurance training

Eur J Appl Physiol. 2020 May;120(5):985-999. doi: 10.1007/s00421-020-04336-2. Epub 2020 Mar 14.

Authors

Øyvind Skattebo¹, Anders Wold Bjerring^{2

3}, Marius Auensen⁴, Sebastian Imre Sarvari^{2

3}, Kristoffer Toldnes Cumming⁴, Carlo Capelli⁴, Jostein Hallén⁴

Affiliations

¹ Department of Physical Performance, Norwegian School of Sport Sciences, Post box 4014 Ullevål Stadion, 0806, Oslo, Norway. oyvind.skattebo@nih.no.
² Center for Cardiological Innovation, Oslo University Hospital, Oslo, Norway.
³ University of Oslo, Oslo, Norway.
⁴ Department of Physical Performance, Norwegian School of Sport Sciences, Post box 4014 Ullevål Stadion, 0806, Oslo, Norway.

Abstract

Purpose: The endurance training (ET)-induced increases in peak oxygen uptake ([Formula: see text]O_2peak) and cardiac output ([Formula: see text]_peak) during upright cycling are reversed to pre-ET levels after removing the training-induced increase in blood volume (BV). We hypothesised that ET-induced improvements in [Formula: see text]O_2peak and [Formula: see text]_peak are preserved following phlebotomy of the BV gained with ET during supine but not during upright cycling. Arteriovenous O₂ difference (a-[Formula: see text]O₂diff; [Formula: see text]O₂/[Formula: see text]), cardiac dimensions and muscle morphology were studied to assess their role for the [Formula: see text]O_2peak improvement.

Methods: Twelve untrained subjects ([Formula: see text]O_2peak: 44 ± 6 ml kg^-1 min^-1) completed 10 weeks of supervised ET (3 sessions/week). Echocardiography, muscle biopsies, haemoglobin mass (Hb_mass) and BV were assessed pre- and post-ET. [Formula: see text]O_2peak and [Formula: see text]_peak during upright and supine cycling were measured pre-ET, post-ET and immediately after Hb_mass was reversed to the individual pre-ET level by phlebotomy.

Results: ET increased the Hb_mass (3.3 ± 2.9%; P = 0.005), BV (3.7 ± 5.6%; P = 0.044) and [Formula: see text]O_2peak during upright and supine cycling (11 ± 6% and 10 ± 8%, respectively; P ≤ 0.003). After phlebotomy, improvements in [Formula: see text]O_2peak compared with pre-ET were preserved in both postures (11 ± 4% and 11 ± 9%; P ≤ 0.005), as was [Formula: see text]_peak (9 ± 14% and 9 ± 10%; P ≤ 0.081). The increased [Formula: see text]_peak and a-[Formula: see text]O₂diff accounted for 70% and 30% of the [Formula: see text]O_2peak improvements, respectively. Markers of mitochondrial density (CS and COX-IV; P ≤ 0.007) and left ventricular mass (P = 0.027) increased.

Conclusion: The ET-induced increase in [Formula: see text]O_2peak was preserved despite removing the increases in Hb_mass and BV by phlebotomy, independent of posture. [Formula: see text]O_2peak increased primarily through elevated [Formula: see text]_peak but also through a widened a-[Formula: see text]O₂diff, potentially mediated by cardiac remodelling and mitochondrial biogenesis.

Keywords: Blood volume; Cardiac output; Echocardiography; Haemoglobin mass; Maximal oxygen uptake; Peripheral adaptations; Supine cycling.

MeSH terms

Adaptation, Physiological*
Adult
Blood Volume*
Body Composition
Cardiac Output
Endurance Training*
Exercise / physiology*
Female
Humans
Male
Muscle, Skeletal / physiology*
Oxygen Consumption*
Time Factors