A closer look
Your muscles don't tear every time you lift something heavy because your proteins act like microscopic bungee cords. Titin is the largest protein in the human body, physically anchoring muscle fibers together. When you apply severe mechanical stress, rather than snapping, titin’s tightly folded domains mechanically unravel one by one to absorb the kinetic energy. Once the tension is released, the protein obediently folds itself back into its original shape. This mechanochemical elasticity is the only reason your beating heart doesn't literally pull itself apart.
