Completely depends on how you run. The trend I see is that everyone thinks running on hard surfaces incurs more impact, but that isn't necessarily the case. ht

Completely depends on how you run. The trend I see is that everyone thinks running on hard surfaces incurs more impact, but that isn't necessarily the case. http://www.barefootrunning.fas.harvard.edu/4BiomechanicsofFootStrike.html http://www.barefootrunning.fas.harvard.edu/4BiomechanicsofFo... Dredged that out of my memory from a couple years ago. Heel strike - Effective mass is approximately the foot plus the lower leg, which equals 6.8% of total body mass. Forefoot strike - Effective mass is the forefoot and some portion of the rearfoot and leg, which equals 1.7% of total body mass. "We have found that even on hard surfaces (a steel force plate) runners who forefoot strike have impact forces that are 7 times lower than shod runners who heel strike. Rates of loading are equal to or less than rates of loading for shod runners."