Coenzyme Q10 is directly involved in energy production in the mitochondria, so the idea that taking it as a supplement will improve endurance seems obvious. However, biochemical logic does not always translate into a result in the stadium. The editorial team analyzed key studies over the past three decades and assessed which of the promises are confirmed and which are not.
Where the Idea Came From
Coenzyme Q10 transfers electrons in the respiratory chain of mitochondria and protects membranes from oxidation. During intense training, the need for ATP and the formation of free radicals rise sharply. Hence the hypothesis: if the supply of the coenzyme is increased, the muscles will be able to produce energy more efficiently and better withstand damage.
The hypothesis was reinforced by clinical observations. In patients with heart failure or mitochondrial diseases, in whom the coenzyme Q10 level is reduced, taking it improved functional indicators in some studies. It was logical to assume that in athletes too the «energy cofactor» would give a boost.
The problem is that a healthy trained person does not have a coenzyme Q10 deficiency. On the contrary, regular training increases the number of mitochondria, and along with them the content of the body's own coenzyme in the muscles. Therefore taking a supplement may not have a «bottleneck» that it could eliminate.
In addition, raising the concentration of the coenzyme in plasma after taking supplements is much easier to achieve than in muscle tissue. Data on the change in coenzyme content in the muscles of healthy people after taking supplements are contradictory, which is another factor that may limit the effect.
Aerobic Performance and Endurance
One of the early controlled studies was conducted by Laaksonen and colleagues (1995): trained young and older men received 120 mg of ubiquinone per day or a placebo for six weeks. No improvement in maximal oxygen uptake or endurance in the supplement group compared with placebo was observed.
An even more unexpected result was obtained by Malm and colleagues (1997). In their study, young men combined intense anaerobic training with taking 120 mg of coenzyme Q10 per day. In the placebo group, anaerobic performance increased more than in the coenzyme group, and the authors suggested a possible link between the supplement and greater muscle damage — this observation later did not receive unambiguous confirmation.
Cooke and colleagues (2008) studied a single and a 14-day intake of 200 mg of coenzyme Q10 in trained and untrained people. They recorded an increase in the concentration of the coenzyme in plasma and muscles and some favorable trends regarding endurance and oxidative stress, but the effects were moderate and not statistically significant on all indicators.
| Study | Participants | Dose and duration | Main result |
|---|---|---|---|
| Laaksonen et al., 1995 | Trained men of various ages | 120 mg/day, 6 weeks | No advantage over placebo regarding endurance |
| Malm et al., 1997 | Young men, anaerobic training | 120 mg/day, 22 days | Placebo improved anaerobic performance more |
| Cooke et al., 2008 | Trained and untrained | 200 mg once and for 14 days | Increase in CoQ10 level, moderate trends regarding endurance |
| Mizuno et al., 2008 | Healthy volunteers | 100 or 300 mg/day, 8 days | Less subjective fatigue at 300 mg |
| Kon et al., 2008 | Kendo athletes | 300 mg/day, 20 days | Lower markers of muscle damage |
Overall, in healthy trained people no convincing effect of coenzyme Q10 on aerobic indicators, such as VO₂max or time to exhaustion, has been shown. Isolated positive trends occur, but they are unstable between studies.
Fatigue and the Subjective Sense of Exertion
More interesting results were obtained regarding subjective fatigue. In the double-blind crossover study by Mizuno and colleagues (2008), participants received 100 or 300 mg of coenzyme Q10 or placebo for eight days, and then performed a fixed load on a cycle ergometer.
At a dose of 300 mg, participants reported less sense of fatigue and showed a better result in the final maximum-speed test compared with placebo. At a dose of 100 mg the effect was less pronounced. The authors interpreted this as a dose-dependent anti-fatigue effect.
Subjective fatigue is an important indicator for practice, since it is precisely what often limits training volume. However, it is also the parameter most vulnerable to the placebo effect. That is exactly why the double-blinding and crossover design in Mizuno's work are strengths, while the small sample and short period are weaknesses.
There are few other quality studies that would reproduce this effect in trained athletes during a real training process. Therefore the editorial team regards the anti-fatigue effect as plausible, but insufficiently confirmed.
Muscle Damage and Oxidative Stress
The most convincing «sports» study of coenzyme Q10 is often called the work of Kon and colleagues (2008). Japanese kendo athletes during an intensive training camp received 300 mg of coenzyme Q10 per day or placebo for 20 days. In the supplement group, the serum levels of creatine kinase and myoglobin — markers of muscle damage — were lower.
The authors linked this effect with the stabilization of muscle cell membranes and antioxidant action. This is consistent with the function of ubiquinol as a membrane antioxidant. However, a lower level of markers in the blood does not necessarily mean faster recovery or better results — this was not measured directly in the study.
Regarding oxidative stress, the systematic review by Östman and colleagues (2012) concluded that data on the effect of coenzyme Q10 on markers of oxidative stress during physical exertion are heterogeneous. Some studies show a reduction in individual markers, others — the absence of an effect, and the measurement methods differ substantially.
The systematic review by Sarmiento and colleagues (2016) also noted that coenzyme Q10 may affect markers of oxidative stress and muscle damage, but the effect on athletic performance remains inconsistent, and larger and higher-quality studies are needed for definitive conclusions.
Strengths and Weaknesses of the Evidence Base
Strengths: coenzyme Q10 has a clear biochemical mechanism, is well tolerated in the studied doses, and several randomized placebo-controlled studies have shown moderate favorable changes in fatigue and markers of muscle damage.
- Small samples — usually a few dozen participants or fewer.
- Short intake periods — from one day to a few weeks.
- Different forms, doses, and assessment methods, which complicates comparison.
- Mostly surrogate markers instead of real athletic results.
- Contradictory results regarding endurance, including a study in which placebo turned out to be better.
The review by the International Society of Sports Nutrition (Kerksick et al., 2018) does not classify coenzyme Q10 among supplements with convincing evidence of improving athletic performance. This is consistent with the picture the editorial team sees: there are interesting signals, but no reliable ergogenic effect has been proven.
In practice, this means that coenzyme Q10 should not be regarded as a priority sports supplement. It is wiser to direct funds and attention to agents with a strong evidence base, while coenzyme Q10 can be considered an additional option during periods of very intense loads — being aware of the limitations of the evidence.
A special case is older athletes or people taking statins. For them the rationale for taking it is different, related to a possible reduction in the coenzyme level, and such a decision should be made together with a doctor.
Editorial Conclusions
Coenzyme Q10 has not shown a stable improvement in endurance or aerobic indicators in healthy trained people, and one of the studies even recorded a worse increase in anaerobic performance compared with placebo.
Moderate favorable signals concern subjective fatigue and markers of muscle damage, mainly at doses of about 300 mg per day in short studies.
Overall, the evidence base is weak and heterogeneous, so coenzyme Q10 is not a primary sports supplement, but an option with a limited and unpredictable effect.
We also recommend our materials on what coenzyme Q10 is and how it works, on its side effects, and on proper intake.
References
- Laaksonen R, Fogelholm M, Himberg JJ, Laakso J, Salorinne Y. Ubiquinone supplementation and exercise capacity in trained young and older men. Eur J Appl Physiol Occup Physiol. 1995;72(1-2):95–100.
- Malm C, Svensson M, Ekblom B, Sjödin B. Effects of ubiquinone-10 supplementation and high intensity training on physical performance in humans. Acta Physiol Scand. 1997;161(3):379–384.
- Cooke M, Iosia M, Buford T, et al. Effects of acute and 14-day coenzyme Q10 supplementation on exercise performance in both trained and untrained individuals. J Int Soc Sports Nutr. 2008;5:8.
- Mizuno K, Tanaka M, Nozaki S, et al. Antifatigue effects of coenzyme Q10 during physical fatigue. Nutrition. 2008;24(4):293–299.
- Kon M, Tanabe K, Akimoto T, et al. Reducing exercise-induced muscular injury in kendo athletes with supplementation of coenzyme Q10. Br J Nutr. 2008;100(4):903–909.
- Östman B, Sjödin A, Michaëlsson K, Byberg L. Coenzyme Q10 supplementation and exercise-induced oxidative stress in humans. Nutrition. 2012;28(4):403–417.
- Sarmiento A, Diaz-Castro J, Pulido-Moran M, et al. Coenzyme Q10 supplementation and exercise in healthy humans: a systematic review. Curr Drug Metab. 2016;17(4):345–358.
- Kerksick CM, Wilborn CD, Roberts MD, et al. ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr. 2018;15(1):38.
Andriy Melnyk
A strength-sports coach and author of programs for beginner and intermediate levels. Writes about training planning.
