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- Discussion:
    - at heel off the resultant force passes in front of the knee and acts to extend the joint (hyper-extension moment);
    - as resultant forces passes in front of metatarsal heads, knee joint flexes & mechanical forces act in direction of flexion once again;
    - knee has extended to approx 178 deg;
    - is probably being initiated by the biarticular gastrocnemius which is also helping to prevent hyperextension of the knee from occuring;
    - peak electrical activity of gastrocnemius occurs shortly after heel off;
    - since mechanical forces are acting to extend knee at this time, and since hamstrings are inactive, it is reasonable to assume that gastrocnemius is helping to prevent knee hyperextension