The integral of quadriceps activity, along with other
quadriceps magnitude and timing variables, were predicted
by hamstrings and soleus activation variables after
training. These relationships were not present prior to
training, which suggests these compensations are not a
result of the injury; rather the relationships were influenced
by the training program. Contraction of the hamstrings
has been shown to counter anterior tibial translation
[10], thus coupling between the quadriceps and
hamstrings is not surprising. The importance of coupling
between the quadriceps and soleus is less obvious, unless
one considers the role of the soleus in controlling tibial
progression during walking, and the overlap in soleus
and quadriceps activity (Fig. 6).