Achilles tendonitis is a common injury of a ‘chronic stress’ type. The damage to the tendon is caused by repeated excessive forces, where lots of little stresses accumulate to overload the tendon.
Studies have linked a whole variety of factors to Achilles tendonitis, including calf muscle flexibility, excessive rear foot pronation and ankle muscle strength. One well-designed study led by Jean McCrory at Wake Forest University(1), North Carolina, involved an in-depth examination of a group of runners suffering from chronic Achilles tendonitis compared to a group of symptom-free runners.
McCrory’s team compared anatomy, flexibility, strength and the degree of rear foot motion and contact forces during running. The two significant differences between the two groups were: the strength of ankle dorsiflexors and plantarflexors (as measured on an isokinetic dynamometer); and the amount of pronation. The runners suffering from Achilles problems were weaker and had greater pronation. All the other factors were not significantly different between the groups.
From these results, McCrory concluded that strengthening exercises and orthotics to control the degree of rear foot pronation would be the priority treatments for athletes suffering from Achilles tendonitis.
Lack of strength in the calf muscles (to which the Achilles tendon attaches) may mean insufficient control of the ankle when the foot makes contact with the ground. When you run, the calf muscles are most active during the first half of the contact phase, when they are absorbing the impact with the ground. At this point the calf muscles are working eccentrically to control the forward motion of the lower leg. When a muscle works eccentrically, both the muscle and its tendon are lengthening. The anterior tibialis muscle (responsible for dorsiflexion and inversion of the foot) is also active during the contact phase, working eccentrically to control the degree of pronation that occurs.
Pronation is the inwards movement of the rear foot as you contact the ground during walking or running and is necessary to absorb impact forces. A normal amount of pronation is a good thing. Too much will over-rotate the lower leg inwards, which means that when the runner extends the ankle to push off, the ankle muscles are not in a strong position and greater stress is placed upon the Achilles tendon.
While this kind of research does not establish a causal link between Achilles injury and excess pronation and/or lack of muscle strength, it does at least indicate differences between those who suffer problems and those who do not. It would be stupid to ignore these differences, as this is the best evidence we have that can help us determine how best to treat Achilles tendonitis.
In practical terms, strengthening exercises for the calf muscle, usually in the form of calf raises, have become the most recommended rehabilitation work for Achilles tendonitis patients. In my experience, this approach is relatively successful for many athletes.
The programme usually focuses on developing eccentric strength, as this is related to the function of the calf muscle during the running movement.
Harvey Wallmann, an assistant professor of physical therapy at the University of Nevada, recommended the following exercise plan for Achilles tendonitis(2). It is based on developing eccentric strength in the calf muscles to increase the tendon’s ability to cope with forces.
To be performed daily
Start with a 5 to 10 min warm-up of gentle CV exercise, preferably non-weight bearing, such as cycling.
The eccentric programme involves the simple calf raise exercise using only body weight on the floor. The workout is progressed by increasing the load and speed of the eccentric phase of the movement (the heel-lowering phase). The final set of repetitions should feel hard, but not painful. If the next day the workout feels the same or easier, then increase the level of difficulty on day 3. Progress in this manner until the patient can achieve the highest level, which may take any time from a few weeks to months, particularly if the patient has suffered with Achilles tendonitis for a long time.
Level 1: Perform a straight-legged heel raise with the uninjured leg (other leg should be lifted slightly off the ground). Place the ball of the injured leg down and lower slowly with both legs until heels reach the floor. The drop should last for four counts. Repeat for 10 repetitions. Perform three sets with 30 seconds rests between sets.
Progression: increase the speed of lowering to a count of two, and then to a fast drop of one count. Further progression: perform a bent-legged heel raise, which will place extra load on the soleus muscle. The knee should be bent 20-30 degrees. Again start with a slow lowering phase and gradually speed up.
At all subsequent levels the recommended programme is 3 sets x 10 reps with 30 sec rest between sets. Progress the speed of lowering and the bent-legged position as for level 1.
Level 2: Perform a heel raise with both legs for lowering and raising phases.
Level 3: Perform the heel raise with the uninjured leg alone during the raising phase and the injured leg alone during the lowering phase, thereby focusing the eccentric load on the injured side.
Level 4: Perform the heel raise with both legs during the raising phase and the injured leg alone during the lowering phase.
Level 5: Perform the heel raise lowering and raising with only the injured leg.
Wallmann’s strengthening programme is a good one, which moves the patient on conservatively. The bent-knee progression is effective in focusing the effort on to the soleus muscles and the increase in load from double to single-leg, uninjured to injured, is sound.
However, in the grand scheme of things, 3 sets x 10 reps of single-leg calf raises is not that demanding on the calf muscles. Most adults would be capable of this with a little training.
My criticism of Wallmann’s plan is that while the progression of speed may make the exercise more functional in terms of coordination, there is no conclusive evidence to show that faster eccentric loading is more demanding. What is more, the loading levels in this programme may not be great enough to significantly improve the strength of the calf.
Does this matter? It may well do. Stronger muscles can absorb greater stress during movement, which means the system is better able to cope without incurring injury. Research has shown that heavy strength training causes an adaptation effect in the muscle-tendon unit overall – in other words, both muscles and tendons benefit. A stronger tendon can absorb more strain and a stronger muscle can produce greater force more efficiently. But to produce this adaptation requires a significantly large load in training to create sufficient force in the muscle and strain through the tendon.
So a more effective approach to an Achilles rehabilitation programme could be to progressively add load to the calf raise exercise, which is the approach favoured by Alfredson et al, a team of sports medics based in Sweden(3).
Patients performed the exercises twice a day, seven days a week for 12 weeks.
Initial phase: The patient performs the calf raise exercise as described above (Wallmann’s workout) but with the ball of the foot placed upon a step. The patient pushes up on the non-injured leg and lowers down on the injured leg, slowly and in control. Perform 3 sets x 15 repetitions of straight-leg calf raise and then bent-leg calf raise.
Progressions: Once this becomes comfortable, increase the eccentric load by adding weights to a back-pack. Loading is continually added – transferring from back-pack to a calf-raise resistance machine if necessary – throughout the 12-week programme.
Alfredson’s programme starts at the equivalent of level 4 of Wellmann’s programme, and involves more repetitions, as the patient performs straight-leg and bent-leg exercises in a single session and undertakes two sessions a day.
I believe Alfredson’s emph-asis on progressing through increased loading rather than through speed will be more effective in strengthening the tendon. And Alfredson’s use of the step enables the patient to perform the eccentric lowering through a full range of movement, which is a superior strengthening method and may even increase the length of the muscle-tendon unit. I would strongly recommend using the step for this exercise.
In summary, Alfredson’s programme is more aggressive than Wellmann’s, as it assumes the patients are capable of single-leg loading immediately. Wellmann assumes that by the end of his programme the patient will have sufficient strength using body weight only, whereas Alfredson’s programme is designed to develop as much strength as possible during the 12 weeks.
Alfredson et al reported this programme in a paper which compared two groups of patients, both with similar levels of tendonitis symptoms, following different treatment plans. One group had corrective surgery, while the other undertook the 12-week programme. Both groups enjoyed the same level of pain relief and both were able to return to normal activity afterwards. This proves that an eccentric loading programme can be a very effective alternative to surgery in reducing Achilles tendonitis symptoms.