Posted: 09 Sep 2010 04:05 AM PDT
Exercises for ankle sprains often include strengthening of the peroneus longus muscle, usually with Thera-Band® elastic bands or ankle weights. Based on its origin and insertion, the peroneus longus muscle is thought to be responsible for ankle eversion and plantar flexion. However, in terms of its true function, the peroneus longus is an important stabilizer of the first ray during closed-chain weight bearing, creating a rigid lever for push-off (Subotnick, 1975).
Electromyographic (EMG) evidence shows that the peroneus longus peaks in activation during the latter half of the stance phase when the weight of the body is over the forefoot in a plantar-flexed position. Despite this evidence, peroneus longus exercises are often prescribed in an open-chain against resistance during eversion movements.
In the Journal of Strength and Conditioning Research, physical therapy researchers investigated the effectiveness of more functional closed-chain exercises on activation of the peroneus longus while measuring EMG activity. They evaluated closed-chain plantar flexion (heel raises) with a 5 pound laterally-directed resistance provided by a yellow Thera-Band resistance band placed around the middle of the foot. A yellow band stretched to 200% of its resting length will produce a force of 5 pounds (Page et al. 2000). According to the authors, “The pull of the band in the lateral direction and away from midline imparts a force to the foot that induces supination/inversion of the foot…The force of the band acts as a perturbation of the peroneus longus.”
The EMG activity of the peroneus longus during this exercise was compared to a heel raise without resistance and open-chain eversion against a 5 pound cuff weight placed around the mid foot. The researchers found that the Thera-Band-resisted heel raise produced 8% more muscle activation than the standard heel raise, and 40% more activation than conventional isotonic eversion. These findings support a more biomechanically-specific exercise using Thera-Band elastic bands for functional strengthening of the peroneus longus. The authors concluded that this exercise “may facilitate more effective training outcomes from programs targeting the peroneus longus,” although more research is needed to confirm this assumption.
REFERENCE: Bellew JW, et al. Facilitating activation of the peroneus longus: electromyographic analysis of exercises consistent with biomechanical function. J Strength Cond Res. 2010 Feb;24(2):442-6.