1) Strengthening
As soon as it is comfortable to do so, you should start strengthening the Peroneal muscles. Strengthening helps the collagen fibres within the tendon to realign and also helps develop the strength needed for running.
Start with isometric exercises which are static contractions. An easy way of doing this is to sit on the ground with the legs out straight on the insides of a chair. Position the front two chair legs on the outsides of the feet. Push outwards with the feet, into the chair legs so there is no movement, but the muscles are contracting. Hold for 5 seconds, rest and repeat 5-10 times initially. This should only be performed if there is no pain. If it is painful, rest and try again in a few days.
The next step on is concentric strengthening which can be achieved using rehab (resistance) bands or ankle weights. With a band, tie it in a loop and place it around the balls of the feet. Turn both feet outwards at the same time, against the bands resistance. Always do band exercises slowly and under control, especially on the way back to the starting point. Again this should be done without pain and with low reps to start with, which can be built up every couple of days. For examples, start with 12-15 reps, build to 25.
Concentric Peroneal strengthening can be achieved with ankle weights which should be wrapped around the forefoot. Lay on your side with the foot to be worked on top and turn the foot out so the toes point towards the ceiling (keep the ankles and heels together).
The final stage of strengthening is eccentric which is the hardest type of contraction for a muscle and really important when running to slow the pronation force on the foot. This is harder to do yourself, but with a partner is pretty straightforward. Sit on the floor with both legs out straight. The partner pronates (inverts) the foot so the sole of the foot faces inwards. As they do this, you try to slow them down. Don’t resist the movement completely, but just aim to control it. The stronger you get, the harder they can push! This is really hard on the muscles and tendons so definitely start with low rep (around 8-10 initially).
2) Stretching
It’s quite difficult to stretch the Peroneal muscles so personally I don’t worry about this. If you are having massage treatment then this is going to be just as, if not more effective than stretching for this injury.
I would however, recommend stretching the calf muscles daily. This is especially important if you overpronate as tight calf muscles can contribute to this and place more strain on the Peroneal tendons.
3) Correcting Causes
Whilst the tendon is resting, this is the ideal time to look at what might have caused you to develop the condition and what you can do about it to stop it coming back.
If you haven’t had a gait analysis I would highly recommend this for Peroneal injuries as they are so closely involved with foot biomechanics. This will make sure you are wearing suitable running shoes and determine if you maybe need additional insoles or orthotics. Or, if you have been running for a long time and not had your gait reassessed in a couple of years, then it is worth getting it checked again as things can change.
If you have old trainers it may be time to replace them as the support and cushioning will have worn out. 500 kms is the rule of thumb for when to change your running shoes.
If this is all ok, take a look at your running program. Were you dramatically increasing mileage? Had you changed your route or added in more hill runs etc? Running on a road with a slant (so that one side is lower) could cause these problems.
If you’re struggling to find a reason for the injury, then I would recommend consulting a running coach to get them to look at your training plans and running technique. An experienced eye may be able to spot something you have missed.
4) Return to Running
Only return to running when completely pain free on a daily basis and once you are confident you have identified and addressed any causative factors.
Start with a very short jog (10 mins e.g.) and then have 2 days rest. Provided there is no recurrence of symptoms, then try another 10 minutes followed by another 2 days rest. If still ok, start to progress your running time, by 5 minutes at a time, running 2-3 times a week and only increasing every other run. Continue with this until you are back to your normal times / distances.