if the knee is extend in stance phase, hamstrings muscles works as "knee extensors". But when in swing phase, that is, when the foot is flying, hamstrings works as "knee flexors". Thus, it depends if the foot is or not bearing the body mass. Good luck!
To my knowledge muscle work is considered as negative if it inhibits motion (breaks or stores energy).
In stance phase in of walking the quadriceps muscle stabilizes stance by inhibiting excessive knee motion (keep the leg straight), especially during stance phase flexion. As muscle force (and the corresponding moment) acts against the motion work is considered negative.
A good examle is walking down stairs or slopes: The quadriceps is active to break and prevent you from falling down although in general (potential) energy is dissipated. The muscle performs negative work and you can feel it after a while of walking down slopes...
At the end of the swing phase the quadricps is active when the heel is no the ground in an eccentric contraction , that amount of contraction stay at the stand phase almost equal till the mass of the body is over the foot than the relaxation comes.
Negative means therefore eccentric but very important in the weight bearing function and movement fluctutation
good luck.
I think that because quadriceps in this phase will start to be in eccentric mode to control knee flexion which is going to start as soon as leg complete knee extension, All ambulation sub-phases occurs in continuous way, and each sub-phase will prepare for next sub-phase.
thanks all , but . DO u mind @vinicius monteiro to provide me a reference about how hamstrings acts as extensors for knee jt at stance phase ?
find information about gait phase and hamstring function Article Biomechanics and muscle function during gait
but if you want more information about both kinetics and kinematics of gait as well, these articles maybe serves your goal:Article Análise biomecânica das articulações do quadril e joelho dur...
Article Muscular Coordination of Knee Motion During the Terminal Swi...
Article Reduced hip extension during walking: Healthy elderly and fa...
Article Angular momentum in human walking
regards
The hamstrings act as hip extensors and work with the quads
during loading and early stance but not at midstance. Perry hand Hoffman have articles on this.
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