Fig. 1. In situ calibration of tendon strain to muscle force for the lateral gastrocnemius, LG, in one turkey. The sciatic nerve was electrically stimulated to generate a muscle contraction while tendon strain and muscle force were measured simultaneously. (A) Strain values for the deep (str1) and superficial (str2) aspects of the bony tendon were averaged (strLG) to account for bending. Muscle force was measured by attaching the free distal end of the tendon to a servomotor. (B) Tendon strain and muscle force during stimulation. The region where the muscle was developing force (indicated by the arrows) was the segment used for calibration. (C) Relationship of muscle force and tendon strain. The slope of the line was determined using linear regression analysis. (D) Pure bending of the bony tendon in the region where the strain gauges were glued. The deep (str1) and superficial (str2) tendon strains are averaged (strLG) to cancel most of the strain due to pure bending.