MUSCLE-CONTRACTION INCREASES THE STRUCTURAL CAPACITY OF THE LOWER LEG- AN INVIVO STUDY IN THE RAT

A model to study the contribution of muscle contraction to the structu ral capacity of the rat tibia was developed. The right lower leg was t ested to failure in three-point ventral bending during electrically st imulated muscle contraction. The left lower leg was tested without sti mulation, as a control. The mean ultimate bending moment for the stimu lated legs was 0.603 Nm, compared with 0.492 Nm for the unstimulated l egs (p < 0.001). The ultimate energy absorption was 0.313 and 0.188 J in the stimulated and unstimulated legs, respectively (p < 0.01). Frac ture strength has been studied nearly exclusively in dissected bone st ripped of all soft tissues. The present investigation suggests that st udies of dissected bone are incomplete compared with the in vivo situa tion, as contraction of the muscles substantially increased the fractu re strength of the lower leg in rats.