Updated: Oct 13, 2020
By Dr. Ashley O'Rourke PT, DPT, ATC, LAT
Eccentric strengthening is just as important as traditional concentric strengthening. Unsure what that is? Read below to find out.
What is Eccentric Strengthening?
Eccentric strength refers to tension being applied to a muscle as it lengthens. This is also
when the muscle's force-producing capacity is most optimal. Studies show that eccentric exercise results in less oxygen consumption, greater force production, and less energy
expenditure than concentric strengthening- or the active shortening of the muscle. The
force produced by a concentric contraction is always less than the muscles maximum force.
During a voluntary muscle contraction, the speed of the contraction and the ability to exert
tension are inversely related. Therefore, the faster a muscle contracts concentrically, the
lower the tension it is able to generate. An example of concentric strengthening would be a
classic bicep curl, whereas the eccentric component would occur as a person lowers the arm
into a straightened position (as the bicep muscle lengthens).
Eccentric Strengthening is Post-Op Rehab:
Eccentric quadricep and gastrocnemius (calf) strength in particular are important following
knee surgeries such as ACL reconstruction because of their importance in absorbing the
weight of your body as they lengthen in order to control your descent- this includes going
down stairs, sitting down in a chair or decelerating from a sprint. Without sufficient
eccentric control it would be difficult and, in some cases, unsafe to perform these activities.
In regards to running, the primary muscles involved in acceleration and deceleration are
quadriceps and gastrocnemius. However, acceleration involves the concentric contraction of
these muscles, while deceleration involves the eccentric use of these muscles. Therefore,
eccentric strength is important to safely slow down following a sprint or before initiating a
rapid change of direction. Research suggests that eccentric strengthening on the non-
involved lower extremity is also beneficial for improving both the quadriceps muscle
strength and the quadriceps accelerated reaction time in the surgical lower extremity.
Concerns with Eccentric Strengthening in Post-Op ACL:
Though the idea of early post-operative eccentric resistance exercise to the surgical limb
has traditionally been contraindicated, due to the potential for injury to the graft, articular
cartilage, or surrounding soft tissue structure, recent evidence has shown that the
application of early eccentrics to the ACL limb can be used to safely increase quadriceps
volume and strength.
While eccentric quadriceps to regain following ACL reconstruction, it does not come without caveats. As with any eccentric training program, careful progression of training volume and intensity in the post ACL
reconstruction patient is a necessity and should be performed under the direction of a licensed physical therapist as too much eccentric quadriceps strength could increase the chances of anterior tibial translation if not accompanied by sufficient hamstring strength.
Therefore, a comprehensive approach, including both concentric and eccentric training to both the anterior and posterior chains surrounding the knee joint should be considered.
Eccentric exercise has the ability to be an effective means to manage many common
orthopedic conditions such as tendinopathies, post-op recovery and muscle strain
prevention. This potential is based on muscle/tendon physiology as it relates to
performance. Eccentric exercise, or when the muscle is lengthened and an external force
exceeds the force produced by the muscle, has been shown to be more effective than
traditional concentric strengthening at minimizing muscle atrophy and improving muscle
force production. It results in less oxygen consumption, greater force production, and less
energy expenditure and should be incorporated into both a preventative strength training
program, as well as, an effective post-op rehabilitation protocol.