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What The Research Reveals About Stretching And Plantar Fasciitis

Stretching is a cornerstone of treatment protocols for plantar fasciitis. With this in mind, this author offers a thorough review of the literature to assess the methods and efficacy of flexibility exercises for heel pain as well as their role in combination with adjunctive treatments. 

Plantar fasciopathy affects approximately 10 percent of the U.S. population at some point during their lifetime and affects an estimated one to two million people per year in the United States.1-4 Despite the prevalence of this condition, there is ongoing debate on the cause, pathophysiology and the best treatment for plantar fasciitis/fasciosis. Historically, the prevailing thinking attributed plantar fasciopathy to a local inflammatory process but more recent data suggests a more degenerative process due to excessive cumulative strain, which adds to the debate regarding the most appropriate treatment.3,4 The most consistent causes of plantar fasciopathy in the literature include: increased BMI, abnormal biomechanical structure, decreased ankle dorsiflexion and occupations/recreational activities with daily prolonged weightbearing.1,2,5,6 

When evaluating the efficacy of proposed treatment options in the literature, there is quite a bit of variability. The most common proposed nonoperative treatment options include non-steroidal anti-inflammatory drugs (NSAIDs), taping, rest, orthotics, night splints, stretching, shoe gear changes, manual therapies, injection therapy and shockwave therapy, all of which have varying levels of evidence with conflicting data in studies both for and against.1,2,5 There is still no definitive answer regarding which treatment is superior.2,7 

That being said, multiple systematic reviews show the majority of patients, 80 to 95 percent, recover within 12 to 18 months with conservative treatments.5,6,8 Flexibility exercises are commonplace in most practitioners’ treatment protocols in both acute and chronic settings, but what is the evidence on these exercises? With this question in mind, let us take a closer look at the effectiveness of flexibility exercises from an evidence-based treatment standpoint for plantar fasciopathy. 

A Closer Look At The Pathomechanics Of Plantar Fasciopathy 

When evaluating the efficacy of flexibility exercises, one must first evaluate the pathogenesis of plantar fasciopathy. Decreased dorsiflexion range of motion (ROM) and isolated gastrocnemius shortening are underlying causative factors in many foot and ankle conditions with multiple studies showing a significant association with the development of plantar fasciopathy.5,9 

A 2003 matched case-control analysis determined that reduced ankle dorsiflexion appeared to be the most significant risk factor.10 A study by Patel and DiGiovanni showed that 83 percent of the patients with recalcitrant plantar fasciopathy had limited ankle dorsiflexion with additional studies citing gastrocnemius tightness as the most common cause of limited dorsiflexion ROM.5,11 Limitations in dorsiflexion are evident in multiple studies evaluating both the general population and athletic individuals with plantar fasciopathy.4 Evaluating running athletes with plantar fasciopathy, Kibler and colleagues found that 88 percent of symptomatic limbs had dynamic ankle ROM deficits and 86 percent had static ankle ROM deficits.12 

Pathomechanical studies show us that in the midstance phase just prior to heel off, decreased dorsiflexory ROM leads to an abnormal rearfoot plantarflexion moment and forefoot dorsiflexion moment that cause an increase in longitudinal tension to the plantar fascia as the tibia attempts to pass over the planted foot.5,13 A tight gastroc-soleus complex can cause increased pronation in midstance as well as early heel-off in gait, which leads to increased knee extension and increased stress through the forefoot and plantar fascia.4-6,14 

A tight gastroc-soleus can be both a cause and an effect of plantar fasciopathy. Studies show that patients with chronic plantar fasciopathy often walk with a slower cadence, shorter stride length and increased stride time.2 These antalgic gait changes can lead to further muscle imbalance, resulting in loss of strength and flexibility, thus highlighting the importance of continuing with flexibility exercises in conjunction with other treatment modalities.2 Correspondingly, in the American Journal of Sports Medicine, Kibler and colleagues describe a negative feedback loop in which injury-causing biomechanical deficits lead to alterations in kinetics that ultimately lead to more pain and biomechanical deficits.12 Additionally, Wheeler has shown a correlation between improvements in tightness and improvements in pain.9 

What Does The Evidence Tell Us About The Effectiveness Of Flexibility Exercises? 

Just evaluating the data from a pathomechanical perspective shows us the importance of improving dorsiflexion ROM. However, the next question to answer is whether the evidence shows flexibility exercises are effective at improving ROM. Multiple studies show that various flexibility exercises can increase joint ROM, passive torque, stretch tolerance, pain tolerance threshold and/or decrease muscle stiffness.15,16 In terms of stretch tolerance, pain reduction and pain threshold, studies imply that afferent nerve input during stretching may inhibit nociceptive fibers and reduce the transmission of nociception.15 

There is debate in the literature as to which type of stretching is best. This is especially true in the athletic community with multiple schools of thought around when to stretch and how to stretch with little definitive research-based consensus. The majority of the research studies in this review evaluate static stretching as opposed to ballistic, dynamic or proprioceptive neuromuscular facilitation stretches. It is important to note the difference between dynamic stretching and ballistic stretching since both involve stretching while the body is in motion. Ballistic stretching involves fast, uncontrolled, jerking motions that have a greater risk of muscle overload and injury if one does not do this properly. Typically, ballistic stretching is no longer recommended. Dynamic stretching is safer as it involves more controlled and coordinated repetitive motions within a defined range of motion. 

In comparison to static stretching, dynamic stretching can better increase local vascularity to musculature, leading to increases in power, and serves as a beneficial warmup before exercise.15,16 Proprioceptive neuromuscular facilitation stretching involves a combination of static and dynamic stretching with intermittent isometric contraction of the agonist in its elongated position.15 In arguments against static stretching, most people cite research which shows static stretching before exercise can decrease strength and power.14 However, it is key to distinguish that these studies look specifically at static stretching in relation to athletic performance and that the results may not necessarily extrapolate to rehabilitation and the treatment of pathology.14-16 

In a 2015 study, Nakamura and team compared the acute effects of proprioceptive neuromuscular facilitation versus static stretches on the gastrocnemius muscle tendon unit.15 The researchers found that immediately following both techniques, there were increases in ROM and passive torque, and a decrease in muscle stiffness. The authors also noted that the static stretching group had a greater percentage change in muscle stiffness whereas the proprioceptive neuromuscular facilitation group had a greater change in passive torque at end ROM. 

Blazevich and coworkers also showed that dynamic stretching in conjunction with static stretching can prevent stretch-induced performance deficits.14,17 Multiple studies show that one should consider a combination of both static and dynamic techniques in rehabilitation programs, but conceded that more studies are necessary to evaluate the long-term effects.14,15 

In a 2005 literature review for American Family Physician, Cole and coworkers gave direct plantar fascia stretching a “B” level evidence rating given multiple positive but limited level 1 studies on its effectiveness.1 Subsequent reviews and research studies show increasing evidence that one should include stretching in the treatment protocol for plantar fasciopathy. A clinical consensus statement published in the Journal of Orthopaedic and Sports Physical Therapy gave combined stretching of the gastroc-soleus and the plantar fascia a grade “A” recommendation due to multiple Level 1 through 3 studies showing its benefit.18 

In the 2017 American College of Foot and Ankle Surgeons (ACFAS) clinical consensus statement on heel pain, the authors stated that stretching is safe and effective, and “extremely important” in the treatment of plantar fasciitis.19 Cil and colleagues, in a 2019 article for Foot and Ankle International, stated that based on systematic reviews, there is a general consensus about the effectiveness of stretching exercises as a beneficial component of a treatment program for plantar fasciitis.20 

What You Should Know About Stretching Techniques And Parameters 

When developing stretching protocols, essential questions include: what structures do you stretch, how do you stretch them and for what duration/frequency? Unfortunately, there is a lack of a clear consensus for these three questions. There is quite a bit of variability in stretching technique between studies. Often, researchers utilize the standing gastrocnemius and soleus wall stretches, likely because they are both easy to perform and do not involve equipment, improving patient adherence. 

How long one holds these stretches and the daily frequency of these stretches vary between study protocols. In 2002, Porter and colleagues performed a randomized controlled trial evaluating static Achilles tendon stretching over a period of four months with one group performing the stretch for three minutes three times per day and the other group doing five sets of 20 seconds, two times per day.21 The study showed that both groups achieved a decrease in pain and improved ROM with no significant differences between groups. Alternatively, Nakamura and colleagues showed significant acute post-stretching effects after a total of two minutes of static stretching twice daily for three weeks.15 While evaluating the parameters in dynamic stretching, Mizuno showed that four sets of 15 repetitions led to a greater improvement of ROM acutely in comparison to one set of 15 repetitions, but noted the benefit plateaued after four sets.16 

Another key consideration is the duration of the rehabilitation program. One possible trend in the literature is an emerging link between prolonged rehabilitation programs (over eight weeks) and positive improvement in long-term results despite differences in the combination of treatment modalities.5,7,20,21 However, this has not been specifically studied with high-level evidence. Drawing comparisons to strength training programs, studies show that initial gains from strength training relate to neural adaptations and that actual structural muscle change requires longer training programs.22 This is why low-resistance circuit training often takes place before heavy weight, low repetition training.22 

In a 2017 systematic review evaluating the effects of chronic stretching on mechanical muscle tendon properties, Frietas and coworkers found a high level of heterogeneity for most of the variables evaluated across studies and concluded that more high quality studies are necessary.22 In their study, the duration of stretching ranged from three to eight weeks and they observed only small improvements in tolerated passive torque. In terms of actual muscle-tendon mechanical properties, Frietas and colleagues noted only trivial effects. They concluded that adaptations and benefits to stretching protocols of less than eight weeks (such as improved ROM and stretch tolerance) appear to occur mostly at the sensory theory level. In theory, stretching protocols greater than eight to 12 weeks may be more beneficial for structural adaptations but more studies are necessary. 

In evaluating which structure to stretch, DiGiovanni and colleagues in 2003 performed a prospective randomized controlled trial comparing the effectiveness of Achilles tendon-specific stretches versus plantar fascia-specific stretches.23 They found superior results with the plantar fascia-specific program at eight weeks. However, when reevaluating long-term effects on the same study participants in 2006, they found marked improvement in both groups with no significant difference between the two groups at a two-year follow-up.24 To perform the plantar fascia-specific stretch, the authors advocated using one hand to dorsiflex the toes while using the opposite hand to palpate the proximal portion of the medial band of the plantar fascia to ensure tautness.23 While some studies advocate holding this stretch for 30 seconds and performing it at least three times per day, others recommended 10 times per day for 10 seconds each.8,25 

In 2018, Engkananuwat and colleagues compared Achilles stretching alone to a combination of Achilles stretching plus plantar fascia stretching.26 While both treatment groups had positive results, the combination stretching group had more significant improvements in both pressure-pain threshold and patient-reported pain outcomes. The combination stretch group had double the number of patients reporting a complete relief of symptoms. This adds to the evidence that a combination of both gastroc-soleus and plantar fascia-specific stretching is beneficial. 

While there is no definitive evidence against stretching, Cole and colleagues in a 2005 review noted there is no evidence to strongly support the effectiveness of any one single treatment for plantar fasciopathy.1 As there are currently no definitive studies that compare stretching alone to a control with no treatment, how much of the long-term improvement in studies involving flexibility exercises directly relates to the treatment effect versus the natural course of symptom relief over time? Correspondingly, when looking for evidence in the research “against stretching,” studies often do not show explicit evidence against stretching yet acknowledge that stretching should not be the sole treatment. Multiple studies have found evidence that stretching in conjunction with and not opposed to other therapies improves outcomes.1,18,23-25, 29,30 

How Does Stretching Compare To Strengthening For Plantar Fasciopathy? 

Many studies compare stretching programs to other various treatment types. One such intervention is strengthening. Some postulate that both ankle and intrinsic foot muscle strengthening could be important components in treating plantar fasciopathy. 

Comparing strengthening versus plantar fascia stretching, Rathleff and coworkers found that the strengthening group had superior results at three months, but there was no significant difference at six and 12 months.25 The authors concluded that adding strengthening to stretching early on could lead to a quicker resolution of symptoms but not as a sole treatment. In blinded, randomized controlled trials, Thong-On and Kamonseki and their respective colleagues found similar results in terms of pain reduction and function in all groups at 12 weeks and eight weeks, respectively, concluding that neither treatment was superior.2,27 

There is no clear consensus over exactly which type of strengthening is best. However, multiple authors recommend intrinsic foot muscle strengthening and eccentric calf raises with MPJ dorsiflexion going into a negative heel position, given the evidence-based use with Achilles tendinopathy. Evidence shows both strength gains and ROM improvement with this technique due to the positioning of the exercise requiring repetitive dorsiflexion and positioning of the exercise.5,6,25,28 

Recognizing The Adjunctive Benefits Of Stretching And Manual Therapies 

When evaluating other treatment combinations, Rompe and team showed that radial shockwave treatment alone was less efficient in comparison to combining it with an eight-week plantar fascial stretching program.29 Also, multiple studies showing positive results with stretching programs included the use of some sort of heel pad or orthotic insert in addition to stretching.1,18,23-25 

One may also consider the use of manual therapies such as cross-friction massage and joint mobilization techniques. A 2018 systematic review of randomized controlled trials involving manual therapy recommended joint and soft tissue mobilizations in conjunction with stretching programs.3 One randomized controlled trial by Celik and colleagues showed that a combination of joint mobilization and stretching showed better results at 12 weeks and at one year than stretching alone.30 Subsequently, a comparative 2019 study showed that a combination of cross-friction massage of the plantar fascia and gastroc-soleus stretching showed greater improvements in reducing pain and improving dorsiflextion ROM in comparison to a combination of joint mobilization and massage alone, but the study authors noted that all groups showed improvement.9 

Manual therapy helps improve and facilitate flexibility as well as improves stretch tolerance and ROM when performed in conjunction with flexibility exercises.3,7,30 Furthermore, studies also show that it can be beneficial to combine self-massage such as foam rolling or therapy balls just prior to stretching to increase ROM gains. In a 2019 study, Capobianco and colleagues noted this finding when specifically looking at middle-aged adult patients as they tend to be less flexible than younger individuals.14 

Evaluating Stretching As Part Of An Individualized Treatment Plan 

Evidence does show that both modifiable and non-modifiable as well as intrinsic and extrinsic risk factors play key roles in the treatment outcomes for plantar fasciopathy.3 As I previously discussed, limited ankle dorsiflexion is an extremely important risk factor in most patients with plantar fasciitis but it is not the only risk factor. One can postulate that individual differences in pathomechanics likely account for the significant variability between study results. The 2018 ACFAS position statement recommends tailoring the treatment of plantar fasciopathy to a patient’s specific symptoms, activity level and lifestyle rather than taking a one-size-fits-all-type approach.6,19 

In a 2020 review, Sullivan and colleagues recommended that individual mechanical factors should guide management of the plantar heel.4 While high-quality study data is not robust regarding individualized programs, there are some limited studies and case series showing better outcomes with individualized multiple intervention programs.30,31 Cil and coworkers compared an outpatient generalized stretching and strengthening program versus a tailored outpatient supervised physical therapy program and found superior clinical results in those patients who had supervised physical therapy.20 

In Conclusion 

When evaluating the research regarding stretching for plantar fasciopathy, it is clear stretching does play an important evidence-based role in treatment. While there is not a complete consensus on parameters, duration or technique, it is becoming more clear that both the gastroc-soleus complex and the plantar fascia structures warrant attention, patients should perform stretching programs consistently over a longer treatment course (more than eight weeks) and they should include a combination of dynamic and static stretches for potentially better results. There is also growing evidence to support adding soft tissue and joint mobilization as well as self-massage in conjunction with flexibility exercises to improve outcomes. 

Additionally, there is some evidence that individualizing treatment plans for specific risk factors and addressing patient-specific pathomechanical and strength deficits in combination with flexibility exercises can yield better results. In the absence of a consensus for the best single treatment of plantar fasciitis, it is important to tailor the treatment approach with full consideration of individual factors and deficits.  

Dr. Canzanese is an Associate of the American College of Foot and Ankle Surgeons, a Diplomate of the American Board of Podiatric Medicine, and a Fellow of the American Academy of Podiatric Sports Medicine. She is a certified athletic trainer, a member of the American Association for Women Podiatrists and is in private practice in Glenside, Pa. 

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By Alicia Canzanese, DPM, ATC, FAAPSM
References

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