Mid-substance Achilles Tendinopathy: What’s the Endgame?

Seattle Seahawks cornerback Richard Sherman (25) ruptured his Achilles tendon as he tackled Arizona Cardinals wide receiver John Brown (12) in 2017. 

It’s human nature to associate pain with a problem, and for the most part, the absence of pain with health and function. For this very reason, end-stage rehabilitation can often be accelerated or overlooked. While there is an ever-growing body of evidence around initial tendinopathy treatment – something we’ll touch on by discussing phase one and two progressions - the focus of this article will be based on the later phase three and four progressions.

These progressions are of particular importance, as during these stages, the tendon may often be only minimally painful, therefore reducing motivation levels to continue diligently following the program. While this article is based on exercise prescription for mid-substance Achilles tendinopathy (tendinopathy symptoms that occur around the central part of the tendon, as opposed to insertional tendinopathy that occurs at the insertion of the Achilles tendon), the concepts and philosophies covered within this article can be adapted and tailored for tendinopathies occurring in various sites.

Tendinopathy overview

Tendinopathy can be a frustrating condition, particularly for those who compete in sports with little opportunity for rest or recovery periods. Tendinopathies have previously been associated with repetitive and overuse activities⁽¹⁾, although the repetitive activity itself may not necessarily be the only underlying issue.

In the presence of movement dysfunction, this may be the case, but more recently tendinopathies have been linked to sudden spikes in loading that exceed the tendons tolerance⁽²⁾. Sudden increases in loading, regardless of the modality, can severely disrupt the tendon’s ability to heal⁽³⁾. For the most part, tendons are capable of maintaining equilibrium and adapting to increases in loads. However, if the rate of loading is greater than the tendons adaptive response, an acute episode of tendinopathy may occur.

Current Evidence-Based Treatments

A common misconception in treating tendinopathies is to cease all activities involving the tendon and unload the limb in an attempt to improve the condition. Unfortunately, this method does not aid in the repair of the tendon, nor does it help build tendon resilience. Cessation of all activity for an athlete often sets them up for future flare-ups and can decrease the load resilience of the tendon⁽⁴⁾.

Tendons are capable of tolerating loads, even in the acute phases of rehabilitation. Recent studies have shown isometric contractions for tendinopathies can have a positive effect on reducing pain^(1,2,5). Once the painful flare up has subsided, eccentric loading can be used to build tendon resilience providing pain levels do not exceed a score of 3 out of 10 on a visual analog scale (VAS)⁽⁶⁾.

The rating of three, usually refers to pain that is noticeable or distracting but can be managed and adapted throughout the session. It should not change movement mechanics. Therefore, center the management of tendinopathies around correct exercise prescription and loading principles rather than a complete cessation of activity.

Table 1: Four-phase progression of Achilles tendon loading

(Note: Time frame is only a guide; there is a large variation in this within each case)

Table 2: Definition of terminology

Loading Phases

Phase One – Acute/Protective

The length of an initial phase can vary in time because some athletes respond better, and their pain levels subside quickly, while others take longer to respond. The key focus in this phase is pain relief through the use of isometric exercises and the administration of Non-Steroidal Anti-inflammatory Drugs (NSAIDs) under the guidance of an appropriately qualified medical practitioner. Isometric exercises such as single leg holds off a step an effective way to reduce pain levels. This position provides a comfortable place to start adding and progressing load. Isometric holds are to be built up to 20 seconds for each leg initially, ensuring the discomfort doesn’t rise above a score of 3/10. The aim is to complete three sets, 3-4 times per day as tolerated, and slowly build the hold time up to 40 seconds using the same guideline of no more than a 3/10 pain score. As the set-rep times increase, the frequency of daily sessions can be reduced down to one or two.

Progression onto phase two is characterized by a marked reduction in pain with activity, and the ability to perform 10 calf raises per leg with no more than a 4/10 pain score. Performed correctly, phase one will reduce a large amount of acute pain in the tendon and build some low-level tendon resilience.

Phase Two – Load Introduction

Phase two focuses on building strength in the tendon while reducing pain levels. If tendons fail to tolerate a load well, it may take as long as 72 hours post-exercise to become painful – unlike the traditional delayed onset of muscle soreness (48 hours). Being mindful of this window, it is therefore important to avoid large loadings within three days of each other. Building strength while reducing pain levels can be achieved through isolated resilience exercises such as single-leg calf raises (see figure 1) and controlled eccentric training. Look to build single-leg calf raises up to 20 reps per set while keeping pain scores below 3/10. Once the client has built up to three sets of 20 reps on each side for calf raises, you can look to add loading, always monitoring any pain levels at the time and for subsequent days.

Figure 1: Single-leg calf raise

The introduction of controlled eccentrics within the same session is permitted once the client has achieved three sets of 10 unloaded calf raises. A good example of this is a double-leg calf raise up, then lowering for five seconds on one leg (see figure 2), gradually building up to 10 reps on each side. Load can also be added to the controlled eccentric reps once three sets of 10 reps have been achieved. Progression to phase three can be characterized by minimal to zero pain with activity and the ability to perform 10 loaded calf raises pain-free.

Figure 2: Eccentric heel lowers (two-legged calf raise up, one leg lowers down)

Phase Three – Strength Accumulation

Phase three is an important phase that is commonly overlooked or neglected as the tendon presents with minimal to no pain and, therefore, is often assumed to have returned to optimal function. With the tendon, relatively pain-free, higher-end strength capacity becomes the focus, along with introducing some reactive stiffness.

The Achilles tendon was designed to be used as a contributor to the stiffness of the ankle joint, allowing for elastic energy to be utilized. Strength resilience exercises are utilized to further increase the strength capacity of the tendon and allow loading of the tendon in a dynamic yet controlled environment. The use of a slow prowler push (see figure 3) is a great way to pre-stretch the Achilles tendon by dorsiflexing the foot prior to foot contact. This removes muscle slack in preparation for generating force into the ground. This allows the Achilles tendon to be utilized in a semi-isometric state while promoting force transfer prior to toe-off.

Figure 3: Slow prowler push

A double box step up (see figure 4) is another global exercise that allows the Achilles to aid in force transfer within the functioning system. Both of these exercises are great examples of integrating the Achilles tendon into global strength movements while still having the focus placed heavily on the Achilles tendon. Phase three requires key exercises to integrate the Achilles tendon back into the global system via its contribution via the soleus/gastrocnemius complex through stiffness. Maximal to near-maximal loads should be utilized in this phase to allow the tendon to experience a high amount of tension and force transfer.

Figure 4: BB step up – double box

Also beginning in phase three are some lower-level reactive stiffness exercises. These exercises allow the tendon to be introduced to a more dynamic environment while keeping forces low and controlled. Mini-tramp jogging (see figure 5) is perfect for this type of exposure. The trampoline has enough elasticity to allow the impact forces to be low, yet causes the tendon to act with stiffness to create a series of stretch-shortening cycles (SSC) with the soleus/gastroc complex.

Figure 5: Mini-tramp jog

The use of the SSC is not the only stimulus that needs to be addressed in Phase three of rehabilitation. While the knee drive hold on a BOSU (see figure 6) does not require the use of the SSC, it forces the tendon to respond to a changing environment under the foot. While the forces are low level, it makes for the perfect introduction to a reactive environment while integrating the entire posterior chain. A plate held in different positions is used to manipulate the environment and force the body to react to maintain posture and stiffness continually. Progression into phase 4 can be characterized by being pain-free on palpation, pain-free with activity, and specifically being able to jump a rope pain-free for approximately two minutes.

Figure 6: Knee drive hold on BOSU

Phase Four – Elastic Tolerance

Phase four is focused on introducing the SSC in a more dynamic environment. Plyometrics are introduced and form the foundation of this phase. A good starting point is the linear and lateral hop and stick (see figures 7 & 8). These exercises allow both a linear and lateral component to the initial program by adding an explosive component whilst not overloading the tendon with an aggressive SSC. These reactive stiffness exercises are essential prior to progressing into ballistic stiffness exercises. Ballistic stiffness exercises begin to add more of an SSC component, along with higher landing forces, which are usually continuous in nature. These higher landing forces build stiffness in the tendon and, therefore, contribute to more efficient and effective tolerance to explosive movements. Linear and lateral hurdle hops (see figures 9 & 10) are perfect to start this progression and to retrain the Achilles tendon to utilize elastic energy.

Figure 7: Linear hop and stick

Figure 8: Lateral hop and stick

Figure 9: Linear hurdle hop

Figure 10: Lateral hurdle hop

Key points

• Isometric exercises act as pain relief across all stages of rehabilitation 
• Three out of 10 pain on the tendon site is acceptable during training 
• Isometrics and isolated resilience exercises must be maintained on an ongoing basis during a weekly training program. Once in Phase three, they can be completed three times per week 
• Never remove all load from the tendon; simply regress if needed 
• Periodizing loading is key — avoid sudden spikes in load

Conclusion

End-stage tendinopathy rehabilitation is commonly overlooked or neglected. This article attempts to lay out some of the end-stage options available to help safeguard the Achilles tendon against higher-end load exposure. There are numerous exercise options and variations for each category; the exercises listed here are just the tip of the iceberg but act as a good starting point. When it comes to rehabilitation, Achilles tendinopathy is never a linear progression. It will flare up some days and feel great other days. The most important thing is to manage and periodize the tendon’s exposure to loads.