Bipedal walking is an important characteristic of humans. Classification of the gait cycle involves two main phases: the stance phase and the swing phase. The stance phase occupies 60% of the gait cycle while the swing phase occupies only 40% of the cycle. The second phase of the Rancho Los Amigos gait classification system is called the ‘loading response’ (which is the same thing as ‘foot flat’ if the standard terminology for gait classification is used). [1]
During loading response, the body absorbs the impact of the foot by rolling in pronation. The hip moves slowly into extension, caused by a contraction of the adductor magnus and gluteus maximus muscles. The knee flexes to 15° to 20° of flexion. Ankle plantar flexion increases to 10-15°. [1]
Both the ankle plantarflexors and the knee extensors are active during the loading response phase of gait. The active muscle groups during the loading response phase of gait are the knee extensors (quadriceps), hip abductors (gluteus medius) and ankle plantarflexors (gastrocnemius, soleus). The mechanical goals desired by the activation of these muscle groups are to accept the body’s weight, stabilize the pelvis and to decelerate mass. [2]
The available literature supports the fact that both muscle groups are indeed active during the loading response phase of gait. Magee, for instance, lists both muscle groups as well as the hip abductors (gluteus medius) as being activated during this phase. However, I cannot state with certainty (as I have no reference to back this) which muscle group is ‘more’ active than the other. It is very likely that they all work in tandem to produce normal or purposeful gait.
Reference 1, Reference 2: Magee D J. Orthopedic Physical Assessment. 2014. 6th Edition. Elsevier Saunders Publishers. Chapter 14, Assessment of Gait. Table 14-4, Muscle Actions During Gait Cycle. Pg 993.
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