This review found five randomised trials (n
161) that examined whether static stretching increased ankle dorsiflexion flexibility of the calf musculature. Although the search strategy allowed the inclusion of trials examining both normal subjects and people with disorders—for example, plantar fasciitis—the results of the review are only generalisable to normal subjects, as no trials were found that included people with disorders. Pooled data from included trials showed an increase of 2.1–3.0° after 5–60 minutes of stretching when compared with no stretching. The statistical heterogeneity was generally very low, indicating that there are no underlying differences in the trials—that is, all trials examined the same effect. The results of the sensitivity analyses were also generally similar to the meta‐analyses, providing confidence that the results of the meta‐analyses are robust. The only result that was not supported by the sensitivity analyses was the one for >30 minutes of stretching. As only one trial was included in the sensitivity analysis of this intervention, it may be that the sensitivity analysis sample was underpowered (n
45) to detect the effect that the primary analysis detected with greater sample power (n
What is already known on this topic
- Calf muscle tightness and reduced range of ankle joint dorsiflexion are associated with a number of lower limb disorders such as plantar fasciitis and Achilles tendonitis
- Calf muscle stretches are commonly prescribed to increase ankle dorsiflexion and reduce the symptoms of such disorders
What this study adds
- Calf muscle stretches provide a small but statistically significant increase in ankle dorsiflexion, particularly after 5–30 minutes of stretching
- It is unclear whether the change that occurs with calf muscle stretching is clinically important
There was a general trend that the longer the stretch, the greater the increase in ankle dorsiflexion:
15 minutes of stretching resulted in a 2.07° increase (95% confidence interval 0.86 to 3.27), whereas >15–30 minutes of stretching resulted in a 3.03° increase (95% confidence interval 0.31 to 5.75). Stretching for >30 minutes resulted in a 2.49° increase (95% confidence interval 0.16 to 4.82), which was still superior to
15 minutes of stretching, although provided less of a gain than >15–30 minutes of stretching. Overall it should be noted that the differences between stretching durations are small (clinically non‐significant), and the results of this systematic review indicate that stretching for a short duration produces a similar result to that of a longer duration. This may be due to the lack of a dose‐response relation or differences in the interventions of the individual trials. Further randomised trials are needed to resolve this.
The PEDro scores of the trials included in the review are relatively high (median 6) considering that blinding of participants and therapists is impossible. The PEDro scale was therefore a useful tool for assessing the quality of the trials except for the two items requiring blinding of participants and therapists, which are inherently difficult for such interventions. Future trial quality could be improved by ensuring that treatment allocation concealment and intention to treat analyses are performed and reported in accordance with the CONSORT statement.17
Although our review shows that static calf muscle stretching provides a small and statistically significant increase in ankle dorsiflexion, we do not know whether the result is of clinical importance from the patient's perspective or whether it may prevent further injury. Symptomatic pain improvement seen in a trial of stretching for plantar fasciitis may be explained by an increase in dorsiflexion18
; and in a recently completed placebo controlled trial of adhesive capsulitis, manual techniques and a directed exercise programme after arthrographic glenohumeral joint distension resulted in improved shoulder range of motion accompanied by greater participant perceived success.19
These findings suggest that improvement in range of motion may be of clinical importance. Future trials evaluating the effectiveness of static stretching should include patient centred outcome measures such as pain, function, and perceived success so that this can be explored further.