Achilles tendinopathy is a general term used to signify pain, tenderness, and chronic changes to the tendon. On a regular basis, I see a lot of new running clients who enter the Healthy Running Program that display lingering symptoms which have not been fully addressed to resolve the injury process. Symptoms are most commonly seen at the mid-portion of the tendon, although insertional tendinopathy where the tendon and calcaneus meet is also possible. Pathology is often caused by degeneration as opposed to inflammation, and can be developed even before the onset of symptoms. That’s why a progressive and structured strength training program for runners can be valuable to maintain the integrity of this tissue as an injury prevention strategy.

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Numerous studies have looked at exercise, therapeutic modalities, soft-tissue therapy, braces and splints, and injections as a way to resolve achilles tendinopathy. Exercise consisting of isometrics, eccentric, eccentric-concentric, and heavy slow resistance loading have been popular and continue to be highly regarded and debated as strategies to address overuse tendon injuries. The debate comes from mixed research showing people who respond favorably while others who may not respond quite as well. However, as a form of conservative management, loading the affected tissue should be a priority early within the rehabilitation process before considering other options.

Let’s define the four types of loading strategies…

1. Isometric loading is when the calf complex is contracting but the achilles is held in a position where it's length remains constant. This can vary from shortened, mid-length, or lengthened positions depending on your specific needs and presentation.

2. Eccentric loading consists of an isolated and slow lengthening of the tissue. Do not confuse this with static stretching, as the calf muscle and achilles tendon are shortened and then actively lengthened through their range of motion. Think of assisting yourself up to the top of a calf raise and then emphasizing a slow and controlled contraction on the way down.

3. Eccentric-concentric loading consists of actively shortening and lengthening of the tissue. During a calf raise, the achilles and calf are used to actively raise up and lower down. This requires equal parts eccentric and concentric contraction.

4. Heavy slow resistance (HSR) more replicates a strength training type exercise where a greater degree of load is placed on the tissue. Instead of performing a bodyweight only movement, HSR utilizes external resistance to load the calf raise with a barbell or dumbbells.

With each of these types of loading to directly address the achilles tendon, repetitions, sets, rest periods, duration of movement, duration of time held in the lengthened position, and external load are all factors which need to be considered for the best results. In addition, Alfredson et al recommends stressing the tendon to the point where pain is evoked. Therefore, an aggressive approach that takes into consideration the "24-Hour Rule” might be necessary in resolving overuse tendon injuries.

The “24-Hour Rule” is a general rule of thumb we use to determine the appropriate amount of stress to place on an injured tendon. Basically, you want to stress the achilles tendon in a way that evokes pain but does not exceed a 3/4 out of 10 on the pain scale. If pain continues after you finish the exercise, it should resolve completely within 24-hours. This is an important concept to understand with tendon pain. A certain degree of pain is acceptable and might be needed to elicit the desired response from the tendon. However, if your pain exceeds these parameters then modifying certain variables, such as the exercise, tempo, load, rest period, and position might be warranted.

With all of this talk about pathology of the achilles tendon, it’s important to also understand how running biomechanics can be linked with injury. In research articles by Azevedo et al and McCrory et al, the factors which were shown in runners suffering from achilles tendinopathy compared to a healthy control group were…

• Decreased range of knee flexion between the foot strike and midstance phases

• Decrease in pre-foot strike muscle activity of the transverse abdominis

• Decrease in post-foot strike muscle activity of the rectus femoris and gluteus medius

• Muscular weakness of the plantar flexors while eccentrically controlling dorsiflexion

• Larger inversion angle at foot strike and increased rate of pronation

• High and inflexible arches

Therefore, in addition to incorporating specific exercises to improve the tendon’s ability to tolerate load, modifying running biomechanics is often warranted. If pain is manageable while running and doesn’t last more than 24-hours after, I usually recommend continuing to run or implementing a run/walk interval so running mechanics can be addressed. Despite overloading the tendon being a main reason which contributed to the injury in the first place, resting often leads to less than desirable results unless compensation and disability result from activity.

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In the following section, let’s cover a progressive loading protocol that I often use when rehabilitating achilles tendinopathy. Of course, there are multiple ways to load the achilles as shown in the research. But, I often find starting with isometrics and progressing to eccentric-concentric and then heavy slow resistance or plyometrics is reliable since it provides multiple options depending on the response from the tendon. Use the “24-Hour Rule” as your guide to determine where to start and progress as tolerated from there.

Isometric Calf Raise

The Isometric Calf Raise is usually a safe starting point if you are suffering from a reactive achilles tendinopathy or hesitant to load the tendon. What this does is place the tendon under load for a given duration to begin stressing the area very conservatively. The variables that can be modified are duration, position of the ankle, and double leg vs. single leg. Complete this exercise for 2-3 sets of 20-60sec.

Calf Raise

The Calf Raise is the entry point into isotonic achilles loading. Isotonics is a term that refers to the muscle/tendon moving from a shortened to lengthened position. When incorporating this exercise, the variables to take into consideration are sets, repetitions, tempo, and range of motion. Complete this exercise for 2-3 sets of 10-20 repetitions.

2-to-1 Calf Raise

The 2-to-1 Calf Raise is used within this progression to segue from bilateral to unilateral loading. Since the achilles needs to withstand a great degree of stress during running and different sporting activities, it’s important to utilize single leg variations to replicate that and introduce a higher degree of load. Simply, raise up on both legs and then isolate the lengthening of the injured achilles tendon with a slow and controlled eccentric contraction. The variables to modify depending on how you respond to this exercise are sets, repetitions, tempo, and range of motion. Complete this exercise for 2-3 sets of 10-20 repetitions.

Single Leg Calf Raise

The Single Leg Calf Raise is essential to help resolve an achilles tendinopathy. One big problem I see is that runners stop with Calf Raises or 2-to-1 Calf Raises since pain begins to stabilize allowing them to return to activity. Unfortunately, the absence of pain does not equate to a fully healed tendon and, therefore, more loading with harder variations is recommended. The variables to modify depending on how you respond to this exercise are sets, repetitions, tempo, and range of motion. Complete this exercise for 2-3 sets of 10-20 repetitions.

Ankle Hops

With any tendon, the end goal needs to improve it’s ability to store and release energy. If you stop short of achieving this, you will have a situation where the capacity to be loaded has been improved but not with rapid and explosive movements. That’s a main reason why most runners suffer from recurrent tendon issues year after year. Ankle Hops is a very simple and important low level plyometric movement. Essentially, it is an explosive Calf Raise that improves the elasticity and shock absorption capability of the tendon and calf complex. Complete 2-3 sets of 5-10 repetitions while increasing intensity.

Now that you have a better understanding about achilles tendinopathy with different exercises to address the injury, it’s important to start simple and determine your starting point. Reflecting back on the “24-Hour Rule,” try to find the most challenging exercise above which creates a mild degree of pain but resolves within 24-hours. Continue to progress in terms of exercise, sets, repetitions, tempo, and range of motion, while being mindful of how you respond.

I hope this article has helped you better understand achilles tendinopathy, as well as recommended strategies to reduce pain and increase function. As always, it’s important to consult with a trained healthcare professional to be properly diagnosed and understand the underlying factors which may be contributing to your injury. Please take a second to click here so we can create a structured plan to resolve your achilles pain once and for all.

Sources:

• Etiologic Factors Associated with Achilles Tendinitis in Runners by McCrory et al

• A Treatment Algorithm for Managing Achilles Tendinopathy: New Treatment Options by Alfredson et al

• Achilles and Patellar Tendinopathy Loading Programmes : A Systematic Review Comparing Clinical Outcomes and Identifying Potential Mechanisms for Effectiveness by Malliaris et al

• Chronic Achilles Tendinopathy Treated with Eccentric Stretching Program by Verrall et al

• Biomechanical Variables Associated with Achilles Tendinopathy in Runners by Azevedo et al

• Achilles Pain, Stiffness, and Muscle Power Deficits: Mid-Portion Achilles Tendinopathy Revision 2018 by Martin et al

• Achilles Tendinopathy: Current Concepts about the Basic Science and Clinical Treatments by Li et al