Decrease in respiratory quotient during exercise following L-carnitine supplementation

Int J Sports Med. 1989 Jun;10(3):169-74. doi: 10.1055/s-2007-1024895.


This study was undertaken to determine the effects of L-carnitine addition to the diet during submaximal exercise in endurance-trained humans. Ten subjects (VO2max: 62 performed a control test (C) (45 min of cycling at 66% of VO2max) followed by 60 min of recovery in a sitting position. Each subject repeated this trial after 28 days of placebo (P) and L-carnitine (L-C) treatment (double-blinded cross-over design). The dose of each treatment was 2 g/day. There were no differences between the C and P tests. The respiratory quotient was lower (p less than 0.05) with treatment than with P or C during exercise. In addition, oxygen uptake, heart rate, blood glycerol, and resting plasma free fatty acid concentrations presented a nonsignificant trend toward higher values in L-C than in the C or P groups. These observations suggest an increased lipid utilization by muscle during exercise in the L-C-treated group. This effect has further possibilities for improving performance during submaximal exercise.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial
  • Review

MeSH terms

  • Adult
  • Carnitine / pharmacology*
  • Double-Blind Method
  • Exercise Test
  • Exercise*
  • Female
  • Humans
  • Male
  • Physical Education and Training
  • Physical Endurance
  • Respiration / drug effects*


  • Carnitine