Does coenzyme Q10 boost exercise performance?

Short answer

No. Taking it doubles the Q10 in your blood, but the amount in muscle stayed the same, and in an analysis that pooled 24 studies the performance gain was small and fell apart once outlier studies were removed. Only blood markers of muscle damage went down.

Does coenzyme Q10 boost exercise performance?
'More Q10 → more cell energy → better performance' — does this formula hold?
Coenzyme Q10 (Q10) is a compound your cells use to make energy. That is why ads claim it boosts endurance and strength. We checked it step by step: blood, then muscle, then performance.
Taking it raises Q10 in the blood
It rose more than 2-fold in 28 days
18 people took Q10 matched to body weight (70 mg a day for a 70 kg person) for 28 days. Blood Q10 rose from 0.91 to 1.97, more than 2 times higher. In an analysis that pooled 24 studies, blood levels rose every time.
But Q10 in muscle stayed the same
Even 12 weeks did not raise it in muscle
40 older adults took 400 mg a day for 12 weeks, and small samples of muscle were taken to measure it. Blood Q10 went up, but Q10 in muscle and in mitochondria (the cell's power plants) did not change. Their VO2max (heart-lung fitness) stayed the same too.
Performance barely changed
The gain fell apart once outliers were removed
In the 24-study analysis, a single dose did nothing, and only regular use showed a small gain. Once outlier studies were removed, that gain fell apart too, and strength and short bursts of power barely changed. The 18-person study also found no consistent difference in oxygen use, lactate or heart rate.
Flip side: training gains were smaller
The placebo group improved its sprint scores more
18 people took Q10 or a placebo for 22 days, with 5 days of hard interval training in the middle. On a test of 10 all-out 10-second bike sprints, the placebo group improved more. Over 7 training sessions, the placebo group also increased the total work it did more.
What dropped was blood markers of muscle damage
Enzymes that leak from damaged muscle went down
In an analysis that pooled 28 trials with 830 people, Q10 lowered enzymes that leak into the blood when muscle is damaged (CK and LDH). Another analysis of 440 people also found lower CK, clearest at 300 mg a day or more. Blood markers dropped, but the effect on performance stayed small, as in card 3.
Bottom line: a supplement that only raises blood levels
The 'Q10 → muscle → performance' chain breaks at the blood
Q10 raised blood levels 2-fold, but the amount in muscle stayed the same and performance barely changed. In the 18 people doing hard training, the placebo group actually improved more. If the goal is better performance, the research gives no reason to spend money on Q10.