The Invisible Impact

Every footstrike while running, the ground pushes back with 2-3 times your body weight. For a 75 kg runner, that is up to 225 kg of force through your leg — every single step. Over a marathon's roughly 40,000 steps, your body absorbs the equivalent of thousands of tons of cumulative impact.

Your skeleton and connective tissue handle this through elastic energy storage. The Achilles tendon alone stores and returns about 35 percent of the energy from each stride. Without this spring mechanism, running would cost roughly 50 percent more energy — humans would be walkers, not runners.