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The SCJ is the professional
journal for strength coaches, personal trainers, physical therapists, athletic
trainers, and other health professionals working in the strength and conditioning
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majority of propulsion in sport is unilateral in nature (e.g., running, jumping,
changing direction, etc.). As a result, the power that an athlete can produce
may differ substantially between legs. When there is a large difference between
limbs (asymmetry), the athlete may be at a greater risk for injury as one side
of the body is unable to produce/absorb the same magnitudes of force as the
It is thought by many strength and conditioning professionals and
clinicians that a magnitude of asymmetry greater than 10–15% should be
addressed in training in order to minimize the muscle imbalance and decrease
the athlete’s potential for injury (1,2,3,4).
important to note that this threshold of 10–15% is used loosely as a
quantitative value for increased risk and not an absolute predictor of injury.
For example, an athlete with an average asymmetry magnitude of 4% may still
become injured during the seasons due to the demands of the sport, while a
player with an average asymmetry magnitude of 21% may not become injured during
the competitive or training seasons.
The purpose of determining the average
magnitude of asymmetry in athletes is to identify those athletes that may be at
a greater risk for incurring an injury due to a larger than average muscle
imbalance between limbs.
also important to note that asymmetries between limbs may be a result of the
natural demands of the sport. For example, the throwing arm of a baseball
pitcher will typically be greater in size and power capabilities than the
contralateral arm. While the average asymmetry magnitude will likely be well
above the 10–15% threshold for this athlete, minimizing this asymmetry may
result in negative effects on the athlete’s performance in competition.
learn more about asymmetries in sport, read more here or refer to the following source articles:
Dr. Jennifer K. Hewit, PhD, CSCS, received her PhD in Biomechanics/Strength and Conditioning from AUT University where she developed a sport-specific agility assessment battery for Netball New Zealand. She now works for the NSCA as an Education Coordinator and continues her sport-specific agility research through various sporting organizations.