Tendon the Achilles tendon stretches as the ankle joint dorsiflexes. During the last portion of the stride, as the foot plantar-flexes (pointing the toes down), the stored elastic energy is released. Furthermore, because the tendon stretches, the muscle is able to function with less or even no change in length, allowing the muscle to generate greater force. The mechanical properties of the tendon are dependent on the collagen fiber diameter and orientation. The collagen fibrils are parallel to each other and closely packed, but show a wave-like appearance due to planar undulations, or crimps, on a scale of several micrometers. In
Tendon transfer or positional transfers. Power transfers are done to perform motion, and therefore requires relatively more powerful donor muscles. Positional transfers, on the other hand, do not require powerful donors. The strength of the antagonist muscle should be similar to the donor to avoid overcorrection and to maintain correct posture. Tendon excursion, or distance a tendon travels upon movement, should be similar to that of the recipient to adequately restore the function. Any transfer of a tendon for another function will generally lose one grade of power. For example, M4 muscle power grade will become M3. A single tendon should be