Is walking downhill a concentric or eccentric contraction of your quadriceps muscle?

Answer 1

Every step, whether going uphill, downhill, or on flat land, involves both an eccentric and concentric contraction.

The eccentric contraction occurs when the quadriceps muscles lengthen as they load. In order for your quadriceps to lengthen, the knee must bend. Thus, the eccentric contraction in the walking motion occurs just after you step. This is perhaps more obvious with running than walking. After the foot touches the ground, the quadriceps is loaded eccentrically by the weight of the body as the knee bends.

The concentric contraction of the quadriceps occurs then when the muscle shortens, as you push off from your foot. Again, this is probably more obvious with a running motion than walking motion. After the weight of your body has shifted onto the foot that is currently in contact with the ground (with your knee bent), your quadriceps contracts concentrically as the knee unbends and you lift your own body weight.

So walking, even downhill, still involves both eccentric and concentric contractions. Walking (and running) downhill can lead to fatigue in your quadriceps due to the greater eccentric loading that occurs when going downhill. The range of muscle motion can be greater and your body is coming from "higher" up (its previous elevation on the hill), which can increase the load as well. As compared with concentric contractions, eccentric contractions can cause more damage to the muscle.