... typically increase in density during aging, thus increasing passive muscle stiffness and potentially limiting the operating lengths of muscle during locomotion. Here, we compare in vivo and in situ muscle strain from the medial gastrocnemius in young (7 months old) and aged (30–32 months old) rats presumed...

..., the medial gastrocnemius muscle of young ( n= 9) and old ( n= 8) Fisher 344BN hybrid rats was chemically fixed at the optimal muscle length for force production; individual fascicles were dissected for length measurement, and laser diffraction was used to assess sarcomere length. Old rats had ∼14% shorter...