After doing heavy leg workouts, the muscles of trained men show a big spike in two specific proteins (IGF-IEa and MGF) that help repair muscle damage, and this spike happens about two days later.

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Evidence from Studies

Supporting (1)

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Recovery after Heavy Resistance Exercise and Skeletal Muscle Androgen Receptor and Insulin-Like Growth Factor-I Isoform Expression in Strength Trained Men

Cohort Study

Human

2011 Mar

This study found that after doing heavy leg workouts, the muscles made more of two special proteins (IGF-IEa and MGF) that help repair damage — exactly what the claim says.

Contradicting (0)

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No contradicting evidence found

Source Study

Recovery after Heavy Resistance Exercise and Skeletal Muscle Androgen Receptor and Insulin-Like Growth Factor-I Isoform Expression in Strength Trained Men

Score: 30

DOI: 10.1519/jsc.0b013e318202e449

Similar Assertions

In trained men, when one muscle repair protein (IGF-IEa) goes up after a workout, the other one (MGF) tends to go up too — they seem to work together.

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The more the thigh swells after a workout, the more the MGF repair protein increases — suggesting MGF might be triggered by physical stretching or swelling in the muscle.

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Lifting heavy weights (70% of your max) makes your muscles turn up the volume on certain genes that help them grow and turn down a gene that holds them back, more than lifting light weights (16% of your max) does after a single workout.

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