Achilles tendinopathy is a common overuse injury, especially among athletes involved in activities that include running and jumping.1,2,3,4
Primary treatment can be challenging, but the condition is also renowned for its propensity for recurrence. Thus, it is not unusual for patients with Achilles tendinopathy to have pain on and off for many years. When physical activity is discontinued, symptoms subside, only to recur as soon as physical activity is resumed.2
Rehabilitation theory suggests that muscular strength, power, muscular endurance, flexibility and motor control might be necessary for full recovery after tendon injuries.4,5,6
One of the main treatments for Achilles tendinopathy is exercise training, and the consensus today seems to be that all patients should be treated with an exercise programme for 3–6 months before any other kind of treatment, such as surgery, is considered.7,8,9,10,11,12,13,14,15
Even with other types of treatment such as surgery, sclerosing injections, modalities and medication, some type of exercise is recommended as a complement to the treatment.16,17,18,19,20,21
Despite the common use of exercise as treatment, it is not fully understood how Achilles tendinopathy affects lower leg muscle‐tendon functions.
To date, evaluation of the effect of treatment on Achilles tendinopathy has focused mainly on improving symptoms and not on the recovery of muscle‐tendon function. The main outcome measure in most treatment studies is evaluation of pain associated with physical activity.8,11,12,13,15,22
More recently, the Victorian Institute of Sports Assessment—Achilles (VISA‐A) questionnaire has been used to evaluate the clinical severity for patients with Achilles tendinopathy.23,24
The evaluations of muscle‐tendon function previously used in treatment studies of patients with Achilles tendinopathy were strength measurements using dynamometry and muscular endurance tests for the calf muscle.12,13,25,26
The operational definition of “muscle‐tendon function” is, however, vague and includes various aspects related to strength, muscular endurance and the ability to utilise the stretch‐shortening cycle. Therefore, it seems unrealistic to expect that one or two tests will be sufficient to detect possible muscle‐tendon function deficits as well as improvements correlated with treatment.
In a previous study, we developed a test battery for evaluation of lower leg muscle‐tendon function in patients with Achilles tendinopathy.27
The test battery was reliable and had a high ability to detect impairments in lower leg function when comparing an injured or “most” symptomatic leg with an uninjured or “least” symptomatic leg in patients with Achilles tendinopathy.27
The test battery had, furthermore, a higher demand on the patients' muscle‐tendon function compared with each individual test.27
Therefore, the conclusion was that Achilles tendinopathy causes pain and also impairs lower leg function. The test battery, evaluating several different aspects of lower leg muscle‐tendon function, was more sensitive—that is, it had a higher ability to detect side‐to‐side differences than—each individual test.27
It still remains to be evaluated whether the impairment in muscle‐tendon function is a true functional deficit or is only due to pain, or a combination of both.
has suggested that Achilles tendinopathy occurs when the body's reparative capability is exceeded by repetitive microtrauma. It is known that, during running and jumping, the Achilles tendon is subjected to loads as high as 6–12 times the weight of the body, and this high repetitive loading is thought to be one of the main pathological stimuli causing Achilles tendinopathy.14,29,30,31
It is suggested that there is a fine line between adequate and healthy loading and overloading of the Achilles tendon. The microtrauma of the tendon might occur before the patient experiences symptoms28
and resuming heavy physical activity too soon and too quickly has a major risk of re‐injury. If the injury process in Achilles tendinopathy starts before symptoms, the absence of symptoms might not mean full recovery of muscle–tendon function. The challenge in rehabilitation is to determine when an athlete is ready to return to full physical activity. Our clinical experience of patients with Achilles tendinopathy is that they are susceptible to re‐injury during the return to sports phase. Athletes who compete close to their limits need to know when they are able to fully load their Achilles tendon with minimal risk of re‐injury.
The primary purpose of this study was to assess the relationship between muscle‐tendon function and symptoms (as measured with the VISA‐A questionnaire) in patients with Achilles tendinopathy using a validated test battery.