The most logical reason is that it has not been proven in the
research. With most, if not all, of the
injury prevention programs and screens coming out of the scientific community,
then it would make sense that it has not been proven in the research. Or, has it?
Unfortunately, like most things in research, it typically takes 10-12
years to disseminate to the public or to become the standard of practice. The purpose of this article is to review the
most current literature on the impact of fatigue on injury rates and how we can
use this knowledge to access injury risk. In doing so, one might even suggest that this
also impacts performance or at least make the logical argument that improvement
in this area would also drive performance.
Risks for lower kinetic chain (what we will define as from
the mid-pecs to the foot) injuries are multi-factorial. Some of these factors are intrinsic (hormonal,
structural, or strength related) and some are extrinsic (playing conditions,
surface or shoe wear). Yet to be the
most impactful on injury rates and have the biggest impact on performance we
need to focus on the ones we can change and determine the “root cause” of
those. In athletes with high skill acquisition
and physical conditioning, determining those “root causes” can be more
difficult. Yet, these athletes are also
at risk for injury. If you question
that, just look at recent non-contact ACL injury rates amongst NFL
players. Why do athletes at this level
suffer non-contact ACL injuries when they are obviously very physically fit and
have high skill acquisition? One might
suggest because we are not screening them correctly or at least considering
what the research is telling us to consider when evaluating.- Studies dating back to
early 2000 show that fatigue impacts injury rates. Factors impacted by fatigue include, but
are not limited to:
- Increase pronation at
the foot – resulting in more foot/ankle injuries and knee injuries
- Decreased
co-contraction, magnitude and timing of contractions of the lower kinetic
chain – resulting in altered abnormal force attenuation along the chain
- Decrease in
proprioception – resulting in decreased balance and agility
Often, in this discussion comes the question about how does
that impact me in my sport. In my sport,
endurance is not as important.
Considering that, let’s look at 4 different studies and how this may
impact individual sports.
In 2004, in a study entitled, The Influence of Muscle fatigue on EMG and Plantar Pressure Patterns as
an Explanation for the Incidence of MT Stress Fractures, authors looked at plantar pressure patterns
with fatigue. What this study showed was
an increase in fatigue resulted in decreased gluteus maximus and medius maximal
contractions which resulted in increased pronation at the foot and increase in
MT pressures. This is critical not only
for track athletes, marathon runners and recreational runners, but also soccer
players, basketball players and football players. For this adds to not only stress fractures of
the metatarsal heads but also ankle injuries and plantar fasciitis.
In 2005 & 2008 in two separate studies entitled, Effect of
Fatigue on Knee Kinetics and Kinematics in Stop-Jump Tasks and Gender Differences in Lower Extremity Landing Mechanics Caused by
Neuromuscular Fatigue authors looked at the impact on fatigue on landing mechanics. These studies showed that with fatigue, there
was decreased maximal volitional contraction of the gluteus medius and
quads/hamstrings with fatigue. This resulted
in an increased shear stress at the knee and decreased force attenuation with
stop jump and with landing. This is
critical for basketball players and volleyball players. What this indicates is that with increase in
fatigue there is increased likelihood of ACL injuries, meniscal injuries as
well as patellafemoral pain.
In 2009, in
a study entitled Jogging Kinematics After
Lumbar Paraspinal Muscle Fatigue authors showed that fatigue of the paraspinals resulted in an increase
in spinal extension, facet pressures and increase in hip extension. This is critical for any athlete as fatigue
in the core results in not only increased incidence of low back pain, but other
studies have also shown that this also has an impact on performance.
So, what
does that mean for us? We know that
fatigue increases the potential for injury and performance. We know some key areas where this can impact
us and what the net result is. No matter
what the sport, the mechanics that result are the same. As such, testing should be designed to assess
the “mechanics” we know result in injury and should have some component of
fatigue. There are tools out there to
look at mechanics and specifically mechanics that result after fatigue. If we realize that the impact from improving
these not only has an impact on injury rates, but also performance, then may be
these will become a standard of practice.
References:
1. Chappell, J. D.,
Herman, D. C., Knight, B. S., Kirkendall, D. T., Garrett, W. E., and Yu, B.: Effect
of Fatigue on Knee Kinetics and Kinematics in Stop-Jump Tasks. American
Journal of Sports Medicine. 33:1022-1029, 2005.
2. Hewitt T, Myer
G, Ford K. Anterior Cruciate Ligament
Injuries in Female Athletes: Mechanisms and Risk Factors. AJSM.
34:299-311. 2006
3. Kernozek T,
Torry M, Iwaski M. Gender Differences
in Lower Extremity Landing Mechanics Caused by Neuromuscular Fatigue. Am J Sports Med. 36: 554-565.
2008.
4. Weist R, Eils E,
Rosenbaum D. “The Influence of Muscle
fatigue on EMG and Plantar Pressure Patterns as an Explanation for the
Incidence of MT Stress Fractures”.
Am J Sport Med. 32:1893-1898.
2004.
- Hart J, Keerigan C, Fritz J, Ingersol
C. “Jogging Kinematics After
Lumbar Paraspinal Muscle Fatigue”.
J Ath Train. 44:475-481.
2009
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