in Lower Extremity Biomechanics Due to a Short-Term Fatigue Protocol

Cortes N, Greska E, Kollock R,
Ambregaonkar J, & Onate JA. Journal
of Athletic Training
. 2013, E-pub ahead of print. doi:10.4085/1062-6050-48.2.03

Take Home Message:  As the body fatigues there may be apparent
compensatory strategies employed, however, lower
extremity biomechanics deteriorate as fatigue becomes greater. This may have
implications for injury prevention program implementation.

Lower extremity injuries (e.g.,
anterior cruciate ligament [ACL], ankle sprains) tend to occur later in games
or practices when athletes may be fatigued; hence, fatigue may increase
susceptibility to lower extremity injuries. 
However, there is only limited evidence that fatigue influences lower
extremity biomechanics. Therefore, the purpose of this study was to evaluate
lower extremity biomechanics among female soccer players at two different
fatigue severities during a functional task. Eighteen NCAA Division I female
soccer players participated in motion analysis of a sidestep-cutting task and
performed a functional agility fatigue protocol, which included vertical jumps,
step-ups and step downs, and other activities. The authors assessed
biomechanics pre-fatigue protocol as well as at 50% and 100% fatigue, which
was defined by the inability to reach 90% vertical jump height during multiple
sets or exertional heart rate plateau within 90% estimated maximum heart rate
for 3 consecutive fatigue sets.  At 50%
fatigue, the soccer players used more knee flexion during landing but at
initial contact they used less hip abduction, knee-adduction moment, and
hip-adduction moment. When the soccer players reached 100% fatigued they
continued to use less hip abduction at initial contact, less knee-adduction
moment at initial contact and less hip-adduction moment at initial contact;
but, now they were also using less hip flexion and knee-adduction moment during
landing. Interestingly, knee flexion decreased during initial contact and
during landing even though at 50% fatigue the athletes were using more knee
flexion during landing.

Clinicians should understand that
fatigue affects lower extremity biomechanics. Therefore, injury prevention and
rehabilitation programs should take this into consideration. Interestingly, the
female soccer players may have adopted compensatory
strategies at 50% fatigue (e.g., increased knee flexion angles during landing).
This may be due to the familiarity of the functional tasks. However, as fatigue
became more severe, these compensatory movements were abandoned for movements
that may increase the risk of injury (e.g., less hip and knee flexion, knee
adduction). This may point to a window of vulnerability.  Apparently these athletes can develop safe
coping strategies up to a certain point, but they eventually will fail as
fatigue gets worse.  This hypothesis may
suggest that injury prevention, strength and conditioning, and rehabilitation
programs could help train movement strategies; but, that we cannot ignore the
importance of endurance in delaying maximum fatigue. Furthermore, our programs could
include training during fatigued states. It will be interesting to see clinical
trials testing whether these programs delay maximum fatigue or influence lower
extremity movement strategies during fatigued states. In the meantime, we need
to be cognizant of the obvious influence fatigue may have on movement

Questions for Discussion: Do
you use injury prevention programs at the beginning or end of practice? Do you
think that there may be more appropriate times for these programs to be
implemented?  Has anyone had experience
cuing of biomechanics late in practices or games?
by: Nicole Cattano
by: Jeffrey Driban

Cortes, N., Greska, E., Kollock, R., Ambegaonkar, J., & Onate, J. (2013). Changes in Lower Extremity Biomechanics Due to a Short-Term Fatigue Protocol Journal of Athletic Training, 48 (3), 306-313 DOI: 10.4085/1062-6050-48.2.03