Strength training for plantar fasciitis and the intrinsic foot musculature: A systematic review
Introduction
Plantar fasciitis is one of the most common musculoskeletal disorders of the foot (McPoil et al., 2008, Young, 2012) treated in primary care (Thing, Maruthappu, & Rogers, 2012). It is thought to result from chronic overload either from lifestyle or exercise and affects both elderly and athletic populations (Schwartz, 2014).
The plantar fascia is an aponeurosis that originates from the medial tubercle of the calcaneus and extends distally to the phalanges (Bolgla, & Malone, 2004). The Windlass Mechanism is a term used to describe how the plantar aponeurosis acts like a pulley (Hicks, 1954), developing tension during dorsiflexion of the great toe. This shortens the distance between the calcaneus and the metatarsals, as the aponeurosis winds around the metatarsal head resulting in elevation the medial longitudinal arch (Bolgla, & Malone, 2004). Together with the intrinsic foot muscles the plantar aponeurosis stabilises the arch and provides dynamic sensory and motor control to the foot (McKeon & Fourchet, 2015).
In addition to sedentary middle aged patients (Radford, Landorf, Buchbinder, & Cook, 2006), plantar fasciitis is particularly prevalent in running and dancing activities that require maximal plantarflexion of the ankle and dorsiflexion of the metatarsophalangeal joint (Brukner & Khan, 2012). Symptoms are characterised by pain radiating the medial aspect of the heel into the arch of foot. Pain is often most intense with the first steps of the day or after rest or warming up with activity (Thing et.al., 2012). As the condition progresses these symptoms can become more debilitating reducing the patient's ability to weight bear. Recent literature proposes that the condition should be termed a fasciosis as the pathology more closely resembles that of tendinosis (Brukner and Khan, 2012, Schwartz, 2014).
Brukner and Khan (2012) state that despite plantar fasciitis being the most common cause of rear foot (inferior heel pain) differential diagnosis should not overlook other common conditions such as fat pad contusion, and less common conditions such as calcaneal stress and traumatic fractures, medial calcaneal nerve entrapment, lateral plantar nerve entrapment, tarsal tunnel syndrome, talar stress fracture, retrocalcaneal bursitis, along with not to be missed pathologies such as spondyloarthropathies, osteoid osteoma and post knee or ankle injury complex pain syndrome (CRPS Type 1). McPoil et al. (2008) include a similar list of differentials, but with the addition of Sever's disease (calcaneal apophysitis) a common cause of heel pain in pediatric patients typically aged 7–14 years old (Marchick, Young, & Ryan, 2015).
Treatments for plantar fasciitis have been varied, with conflicting evidence (McPoil et al., 2008). Until recently exercise therapy reviews have highlighted the effectiveness of plantar fascia-specific stretching and have indicated it may have limited benefits (Almubarak, 2012, Schwartz, 2014). However, a recent a systematic review found that there is a significant association between intrinsic foot muscle weakness and painful foot pathologies such as plantar fasciitis (Latey, Burns, Hiller, & Nightingale, 2014). Therefore, the aim of this review is to critically evaluate the literature investigating strength training interventions in the treatment of plantar fasciitis and improving intrinsic foot musculature strength.
Section snippets
Search strategy
The systematic review “Strength training for plantar fasciitis and the intrinsic foot musculature” was registered with PROSPERO (No. CRD42016036302). The following bibliographic databases were searched to identify potentially relevant articles: PubMed, CINHAL, Web of Science, SPORTSDiscus, EBSCO Academic Search Complete and PEDRO or all articles up until March 23, 2016.
The database search, literature screening and data extraction was completed by a single researcher (DH). The database search
Results
Combined searches literature searches produced a total of 226 articles, and once duplicates were removed (94 excluded) this was reduced to 132 eligible articles. Articles were then screened by title (92 excluded), abstract (11 excluded), and then 29 articles full text articles were obtained for review against the inclusion criteria “(i) specific isolated plantar/IFM strength intervention, and (ii) pre-test and post-test measures to assess the effectiveness of intervention” with a further 22
Discussion
A comparison of the interventions presented in the reviewed studies highlights significant differences in strength training approaches to treating plantar fasciitis and improving intrinsic foot musculature strength. Latey et al. (2014) documented a link between intrinsic foot muscle weakness and painful foot pathologies such as plantar fasciitis. However, Rathleff et al. (2014) was the only study that examined a symptomatic population. It was also of particular significance given that high-load
Summary
Based on the studies reviewed it was not possible to identify the extent to which strengthening interventions that improve intrinsic foot musculature may benefit symptomatic or at risk populations to plantar fasciitis/heel pain.
There is limited external validity that short foot exercises (Lynn et al., 2012, Mulligan and Cook, 2013) toe flexion of all interphalangeal and metatarsophalangeal joints against resistance (Hashimoto & Sakuraba, 2014) contribute to improved intrinsic foot musculature
Acknowledgements
None. No funding to declare.
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Contact address: Faculty of Health Sciences & Medicine, Bond University, QLD 4229, Australia.