Just as a reminder, the drill selection is driven by at least three things: the nature of the injury (tissue or tissues involved), the severity and irritability or what we refer to as the "stage", and the mechanics of the involved structures. In Chuck's case, the tissue is the peroneus longus and brevis, the stage is unknown, and the mechanics are deceleration of the lower leg over the foot in a weight bearing position.
For someone who has symptoms either at rest or very quickly with activity, one of the drills we might choose would be a bilateral squat with a less than body weight load. We prefer to use a Total Gym to reduce the bodyweight force.
After testing to find out the appropriate level, the client would perform 3-5 minutes of squats with a focus on pressing the ball of the foot into the footplate. This puts the dosage close to 100 reps per set. The peroneus longus plantarflexes and everts the foot which you can create by simply applying force into the base of the first metatarsal (ball of the foot). Although the foot doesn't move, you'll increase the tension in those muscles from just trying. Near the end of the set, you should feel a mild degree of fatigue and pain or discomfort.
A progression would be to move to a sidelying position and place the foot on a foam pad to create an inverted position (or supinated). Now, as Mike squats, he tries to pronate the foot by pressing the ball of the foot into the foam pad. This increases the load on the peroneus longus and brevis.
For less irritable or severe cases, we might choose a split squat with a lat eral vector. The vector or line of force pulls the leg away from the midline of the body (which is why we call it a lateral vector). In the picture, you can see that at rest, Mike's leg has been pulled out and even rotated out a bit. His job during the drill was to press the great toe into the floor and keep the lower leg straight which he did. And, his comment was that he could feel the muscles on the outside of his leg working fairly hard.
The dosage for this drill is lower than the bilateral squat since the load is higher. It's still fairly high, from muscle training standards, at 20 to 30 repetitions per set. And, we want both a moderate degree of fatigue and pain at the end of the set(s).
The difficult part of this process is finding the right mix of load and reps and pain. We often have to coach clients that all pain is not bad. Some pain is actually good for you as in the case of tendonosis.
But, since all pain is emotional, you have to be careful in applying this concept to your self or someone else. It's just a lot easier to have a coach - not necessarily right there with you all the time - but someone who can help you interpret what you're doing and feeling.
Thanks to our physical therapy student intern, Mike Collier, from the University of Wisconsin, for helping me with this post by generously serving as a subject and asking some great questions.