title: Coenzyme Q10 supplementation and exercise-induced oxidative stress in humans.
abstract: OBJECTIVE
  The theoretically beneficial effects of coenzyme Q10 (Q10) on exercise-related oxidative stress and physical capacity have not been confirmed to our knowledge by interventional supplementation studies. Our aim was to investigate further whether Q10 supplementation at a dose recommended by manufacturers influences these factors.
  
  
  METHODS
  Using a randomized, double-blind, controlled design, we investigated the effect on physical capacity of 8 wk of treatment with a daily dose of 90 mg of Q10 (n = 12) compared with placebo (n = 11) in moderately trained healthy men 19 to 44 y old. Two days of individualized performance tests to physical exhaustion were performed before and after the intervention. Primary outcomes were maximal oxygen uptake, workload, and heart rate at the lactate threshold. Secondary outcomes were creatine kinase, hypoxanthine, and uric acid.
  
  
  RESULTS
  No significant differences between the groups were discerned after the intervention for maximal oxygen uptake (-0.11 L/min, 95% confidence interval -0.31 to 0.08, P = 0.44), workload at lactate threshold (6.3 W, -13.4 to 25.9, P = 0.36), or heart rate at lactate threshold (2.0 beats/min, -4.9 to 8.9, P = 0.41). No differences between the groups were detected for hypoxanthine or uric acid (serum markers of oxidative stress) or creatine kinase (a marker of skeletal muscle damage).
  
  
  CONCLUSIONS
  Although in theory Q10 could be beneficial for exercise capacity and in decreasing oxidative stress, the present study could not demonstrate that such effects exist after supplementation with a recommended dose.
authors.affiliation: Department of Orthopaedics, Østfold Hospital, Fredrikstad, Norway.
authors.forename: Bengt
authors.initials: B
authors.lastname: Ostman
authors.forename: Anders
authors.initials: A
authors.lastname: Sjödin
authors.forename: Karl
authors.initials: K
authors.lastname: Michaëlsson
authors.forename: Liisa
authors.initials: L
authors.lastname: Byberg
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold; D000975:Antioxidants / Q000494:pharmacology*; D003402:Creatine Kinase / Q000097:blood; D019587:Dietary Supplements; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D019271:Hypoxanthine / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal; D018384:Oxidative Stress / Q000502:physiology*; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000494:pharmacology; D014527:Uric Acid / Q000097:blood; D014937:Work; D055815:Young Adult
chemical_list: D000975:Antioxidants; D014451:Ubiquinone; D014527:Uric Acid; D019271:Hypoxanthine; D019344:Lactic Acid; D003402:Creatine Kinase; C024989:coenzyme Q10