Cross-Education Strength and Activation
After Eccentric Exercise

LK, Palmieri-Smith RM. J Athl Train. 2014
Sep-Oct; 49(5):582-9. DOI: 10.4085/1062-6050-49.3.24.

Take Home Message:  Eccentric strength training
improves eccentric quadriceps muscle strength in the unexercised limb.

studies have reported on the phenomenon of cross-education,
where unilateral strength training induces strength gains not only in the trained
limb, but also in the corresponding muscles of the contralateral limb. It has
been suggested that neural adaptation is the driving force behind this, as no
significant structural changes within the muscles have been found in
association with this gain through dynamometer readings. To date, very few
studies have evaluated whether cross-education training could improve
quadriceps strength or activation. Hence, the authors aimed to place cross-education
into a rehabilitation setting by first testing it on healthy individuals. In
doing so, they sought to determine if eccentric exercises improved quadriceps
strength and activation in the unexercised limb of healthy individuals. Eighteen
healthy individuals were randomly placed into either an eccentric training
group or a control group. The authors followed participants for eight weeks. The
eccentric training group completed supervised training sessions (3 times per
week). During the sessions the participants completed a warm-up and 4 sets of
10 maximal eccentric isokinetic movements of their dominant limb with a
dynamometer at 60º/s. The training group increased eccentric strength in the
unexercised limb between pre- and mid-intervention as well as pre- to post-intervention,
but the control group had no changes. Additionally, there was some evidence
that the training group may had increased muscle activation in the unexercised
leg between the pre-intervention and post-intervention measurements. The
authors noted no concentric strength gains at any time point in either the
training or control groups.

this study, eccentric quadriceps training improved eccentric strength in the
unexercised limb of healthy individuals. The authors believe the gains found in
the unexercised limb of the training group may have occurred because of
heightened neural activity, as evidenced by the trend toward increased muscle
activation. For these reasons, cross-education via eccentric training could
become a useful tool in rehabilitation programs to improve quadriceps strength
following an injury or surgery. It will be helpful to see if these protocols
work as well, if not better, among individuals with a recent knee injury or
surgery. The researchers claimed that isotonic exercises would only result in a
small strength gain because isokinetic exercise maximally loads throughout the
entire range of motion. However, it would be interesting to see if using large resistance
with isotonic exercises could display close to the same results as isokinetic
exercises. Furthermore, it would be helpful to determine if isotonic exercises
are enough to elicit the cross-education effect among injured individuals. Clinically,
this is an important topic, because after an injury, especially in the lower
extremities, most clinicians do not want to start with eccentric exercises, as
mentioned. Therefore, exercising the uninjured (contralateral) limb to produce strength
gains in the injured limb could be critical to the rehabilitation process. While
more research may be warranted the potential benefits of trying these exercises
with our patients probably outweigh the small risks.

for Discussion: What types of contralateral exercises can help increase
strength in the injured limb? Do you think eccentric training the contralateral
limb has the potential to improve strength around an injured joint at other
regions of the body?
Written by: Blake Crosby &
Jennifer Payne
Reviewed by: Kim Pritchard

Related Posts:

Lepley, L., & Palmieri-Smith, R. (2014). Cross-Education Strength and Activation After Eccentric Exercise Journal of Athletic Training, 49 (5), 582-589 DOI: 10.4085/1062-6050-49.3.24