Prolonged constant load cycling exercise is associated with reduced gross efficiency and increased muscle oxygen uptake

Scand J Med Sci Sports. 2017 Apr;27(4):408-417. doi: 10.1111/sms.12673. Epub 2016 Mar 19.


This study investigated the effects of prolonged constant load cycling exercise on cycling efficiency and local muscle oxygen uptake responses. Fourteen well-trained cyclists each completed a 2-h steady-state cycling bout at 60% of their maximal minute power output to assess changes in gross cycling efficiency (GE) and muscle oxygen uptake (mVO2 ) at time points 5, 30, 60, 90, and 120 min. Near-infrared spatially resolved spectroscopy (NIRS) was used to continually monitor tissue oxygenation of the Vastus Lateralis muscle, with arterial occlusions (OCC) applied to assess mVO2 . The half-recovery time of oxygenated hemoglobin (HbO2 ) was also assessed pre and post the 2-h cycling exercise by measuring the hyperemic response following a 5-min OCC. GE significantly declined during the 2-h cycling bout (18.4 ± 1.6 to 17.4 ± 1.4%; P < 0.01). Conversely, mVO2 increased, being significantly higher after 90 and 120 min than at min 5 (+0.04 mlO2 /min/100 g; P = 0.03). The half-recovery time for HbO2 was increased comparing pre and post the 2-h cycling exercise (+7.1 ± 19s), albeit not significantly (d: 0.48; P = 0.27). This study demonstrates that GE decreases during prolonged constant load cycling exercise and provides evidence of an increased mVO2 , suggestive of progressive mitochondrial or contractile inefficiency.

Keywords: Cycling efficiency; endurance performance; lactate threshold; maximal oxygen uptake; muscle efficiency.

MeSH terms

  • Adolescent
  • Adult
  • Bicycling / physiology*
  • Exercise / physiology*
  • Humans
  • Male
  • Muscle, Skeletal / metabolism
  • Oxygen Consumption*
  • Quadriceps Muscle / metabolism*
  • Spectroscopy, Near-Infrared
  • Young Adult