Research

Mixed

Prior strength training history significantly alters the acute myogenic gene response (MyoD, myogenin) to endurance exercise compared to endurance-trained individuals.

If you are a strength athlete, your muscles react to cardio differently than an endurance athlete's. You may not see the same 'muscle-building' gene signals (MyoD/myogenin) during cardio that an endurance runner does. This doesn't mean cardio is bad for you, but your body is prioritizing different adaptations.

GoodQualifiesHIGH confidence
Cycling exercise produced diverse responses between ET and ST subjects for the myogenic regulatory factors MyoD and myogenin... There was an increase in both MyoD (~3-fold) and myogenin mRNA (~0.9-fold) in ET subjects after cycling. In contrast, cycling decreased MyoD (~0.4-fold) and myogenin (~0.4-fold) in ST subjects.
Vernon G. Coffey et al. · American Journal of Physiology-Endocrinology and Metabolism · 2005

Why this rating

Clear divergence in response between groups, but mechanism for ST suppression is described as 'elusive'.

Source

Interaction of contractile activity and training history on mRNA abundance in skeletal muscle from trained athletes

Vernon G. Coffey et al. · American Journal of Physiology-Endocrinology and Metabolism · 2005

DOI 10.1152/ajpendo.00299.2005

crossover · n=13Cited 146×
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DOI resolved against Crossref · corpus check 2026-06-10

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