Undulatory locomotion, as seen in the nematode
, is a common swimming gait of organisms populating the world of low Reynolds number. While the nematode’s motility is expected to be a strong function of its material properties, measurements remain scarce. Here, we first reveal the robustness of
’ swimming gait with increasing mechanical load. By coupling kinematic data with a simple model, we measure non-invasively
’ material properties including Young’s modulus and tissue viscosity. By comparing wild-type nematodes with mutant strains carrying muscular dystrophy, we find that tissue properties are sensitive to changes in muscle functional properties. Altogether, our findings suggest that
is an attractive model to bridge small-scale motility research with biomechanical knowledge.