ALT Tissues are perpetually subjected to mechanical forces. We know for nearly a century that high mechanical load on polymer materials - be it a shoe sole or rubber band – causes the rupture of chemical bonds and generates mechanoradicals. We uncovered the very same mechanism in biology: radicals form by stretching collagen, a major protein material of our tissues, even under stresses far below tissue failure. Using experiments in conjunction with simulations and machine learning we reveal how collagen tames its radicals and converts them in a highly controlled fashion to oxidative stress, dominantly hydrogen peroxide. We currently explore how this new mechano-sensing mechanism is related to tissue inflammation and ageing.