

·
Productive –
allows to accomplish task
·
Efficient –
decreased number of Kcals per unit of force produced
·
Loads
tissues in anatomically designed fashion
·
Decreases
ground reaction forces.
Breakdown any portion of the lower kinetic
chain can add to significant increases in ground reaction forces (GRF). Increase in GRF means the tissues are under
more stress and therefore more likely to sustain an injury. In a 2009 study by Winiarksi et al,
they found that GRFs are significantly higher in those who had minor variations
in gait and center of gravity during gait.
In this study, they looked at those who were post ACL reconstruction with
gait deviations and found that the GRF typically experienced with human gait
went from 1.1x body weight to 5-7x body weight with these altered gait patterns. In this example, one might assume the gait
deviation is the “root cause” when in fact a lack of range of motion of the
hip, knee or ankle, weakness in the kinetic chain or lack of proprioception is the
more likely contributing factor to the gait deviation. In this example, the gait deviation is the
symptom of the problem. So how do you
determine the problem?
First we have to know where to look. Until ~10 years ago, clinicians never looked
above the foot/ankle for the root cause of foot/ankle problems (like plantar
fasciitis). However, the work by Weist et al, in
2004 clearly showed that fatigue of the hip can lead to increased plantar and
metatarsal pressures. This not only
highlights the importance of these muscles during running gait but also what
happens when they are not functioning optimally. The increase in pressures (GRF) seen can
result in a plethora of foot/ankle problems.
This same study showed increase in pronation at the foot with fatigue of
the hip and gastrocnemius. Since hip
fatigue is contributing to this pronation, if we only looked at the foot/ankle
and put the patient in an orthotic, then we are only addressing a small part of
the “root cause”.
When looking at the
most common orthopedic injuries associated with running, we find that most are often
associated with the same mechanics we see with ACL injuries. In 2000, Fredericson et al
showed that hip weakness was commonly associated with IT band friction syndrome
in long distance runners. In 2003, Ireland et al showed
that lack of hip strength was commonly associated with patellofemoral pain in
active females (including runners). These
studies as well as others have identified the same movement patterns that are
associated with ACL injury risk also put runners at greater risk for orthopedic
injuries of the entire lower kinetic chain.
Knowing this and since there is such an abundance of ACL literature, we
can look at ACL fatigue studies to see how this may correlate to running. Why look at fatigue?

So what do the fatigue
studies tell us and how does that change the way we assess? We know from studies as far back as 1997 by Lattanzio et al that
fatigue impacts proprioception. This is important
for runners or athletes as most start to complain of pain later in the run or
game as fatigue starts to set in.
Fatigue in hip, knee and/or ankle proprioception results increased movement
at the joint during high load activities which can lead to injury. Burke et al in a
2000 study question whether this is due to fatigue at the muscle spindle level
or elsewhere. Although the answer is not
completely clear, the results by Miura et al in 2004
indicate that endurance training alone does not significantly improve mechanics
evident with fatigue.

So once we fatigue the
athlete, how do we assess? That will be
the focus of third and final article in this series.
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