How Popular Allergy Medicines Can Affect Your Muscle Gains

The same meds that staunch your allergy symptoms or heartburn might also diminish your gains at the gym: Over-the-counter antihistamines may hamper your muscle recovery after exercise, a new study from the University of Oregon suggests.

One hour before a 60-minute strength training workout, the participants took strong doses of two antihistamines, fexofenadine (Allegra, which treats hay fever symptoms) and ranitidine (Zantac, which treats heartburn).

After they completed their workout, the researchers tested their muscles to gauge their recovery.

Normally after vigorous exercise, 3,000 genes work to aid recovery by boosting the blood flow to the tiny tears in your muscle fibers that occur when you light weights. This increases muscle-protein synthesis, which repairs and reinforces the fibers so that they’re more resistant the next time you lift weights.