For performance, this damage limits factors like force output and the ability to generate power, which is no good for the athlete (8).
However, carnitine appears to limit the effect of damaging exercise.
For example, one study enrolled participants and provided them with carnitine or a placebo daily for three weeks. Then, each subject performed five high-rep squat sets with only two minutes of rest in between (5).
Afterward, for the following four days, the subjects underwent MRI scans to observe the amount of muscle damage incurred and their recovery.
Based on the findings, when the subjects used carnitine, they displayed approximately 43% less damage on average compared to participants consuming a placebo (5).
But, there were even more benefits.
Secondary to muscle damage, the researchers also measured each participant’s perceived soreness for the following four days as well. They found in addition to reduced damage, carnitine users were significantly less sore at all time points compared to placebo (5).
Best of all, these findings have been duplicated multiple times.
In similar study formats, researchers consistently show that carnitine use limits markers of muscle damage and soreness perception (4, 5, 9).
BUT ISN'T MUSCLE DAMAGE GOOD FOR MUSCLE GROWTH?
Muscle damage has long been thought necessary for building muscle. The idea is simple: you tear your muscles, and they rebuild stronger!
Unfortunately, muscle growth is a bit more complicated.
New research is beginning to show that muscle growth, or the increase in size and strength of your muscles, occurs after muscle damage is repaired instead of as a direct result of it (10).
Our bodies grow according to protein balance (11).
Each day some proteins degrade, and some grow. When growth exceeds breakdown, your muscles get bigger. In this case, you have a “net positive protein balance.”
When you damage your muscle, the amount of breakdown overcomes the amount of protein growth creating a “net negative protein balance.”
To get back to baseline, where no protein is being grown or degraded, that damage has to be repaired. Muscle damage makes building a net positive balance, and thus, muscle growth more difficult.
The benefit of carnitine here is that it appears to limit how much damage or breakdown is occurring. Essentially, you’ll get the stimulus from the workout but limit the damage that’s happening, potentially making your progression a bit easier (5).
CARNITINE SPARES ENERGY RESERVES DURING EXERCISE