These shoes are BOSS! I have always worked out and NEVER had a burn in my calf. I have trunks for legs.... I have been running for years, yoga, strength training and I have never had a calf workout like running in these shoes. I can actually feel my posture correcting itself as I am running in Vibrams. I forgot my Vibs at a friends and had to wear my old new balance shoes on a run. They were terrible. Reg runnign shoes force you to run on your heal and Vibrams allow you to run on your toes and balls like we were meant to. I will never wear a different pair of shoes to work out again. I own 3 pairs. I am a vibram gal for life.