Over recent years there have been a number of studies demonstrating a link between tight hamstrings and plantar fasciitis. However, hamstring stretches are not a commonly prescribed exercise by clinicians for plantar fasciitis treatment. So we need to ask the question - should the treatment plan also include hamstring stretches?
Let's take a look...
Study 1
A study published in the journal, Foot & Ankle Specialist (2011) found that participants (86 of 210 feet) with hamstring tightness were 8.7 times as likely to experience plantar fasciitis as participants without hamstring tightness. Their study also found that patients with a Body Mass Index (BMI) greater than 35 were 2.4 times as likely as those with a BMI less than 35 to have plantar fasciitis. This also highlights the importance of weight loss as part of a patient's treatment plan if overweight and suffering from plantar fasciitis (Labovitz et al 2011).
study 2
A study, published in Foot & Ankle International looked at hamstring flexibility and forefoot loading stress. The results indicate that an increase in hamstring tightness may induce prolonged forefoot loading and through the windlass mechanism (an important part of normal foot function) be a factor that increases repetitive injury to the plantar fascia (Harty et al 2005).
study 3
A more recent study also published in the journal Foot & Ankle International also found a significant relationship between tight hamstrings as well in tight calf muscles in plantar fasciitis sufferers in comparison to a control group of people who did not have plantar fasciitis and who had good hamstring a calf flexibility (Bolivar et al 2013).
Discussion
It is currently unclear as to how exactly the hamstrings play a role in plantar fasciitis. It has been suggested that an increase in hamstring tightness may induce prolonged forefoot loading and, through the windlass mechanism, may be a factor that increases repetitive plantar fascia injury.
Another possible cause may be the strong connection of the hamstrings to the calf muscles which then attach to the plantar fascia via the Achilles tendon. It is well known that an increase in tensile stress on the Achilles tendon transfers an increase in loading stress on the plantar fascia. Since the calf muscles are attached strongly to the hamstring via fascia (connective tissue) it is likely that any tightness in the hamstrings can transfer this tension down to the plantar fascia. This theory is supported by anatomical dissection studies completed by Thomas Myers published in his book 'Anatomy Trains' (2009) which demonstrate the strong connection running from the plantar fascia to knees and from the knees to the skull. This is known as the superficial back line.
Conclusion
It is well known that tight calf muscles are a causative factor in the development of plantar fasciitis. There have been a number of studies over the past 30 years to demonstrate this. Until recently, there has been a lack of studies looking at hamstring flexibility as another causative factor, however, these recent studies have now demonstrated a strong link. Therefore hamstring stretching exercises should play a crucial role in the treatment and prevention of plantar fasciitis. Below are three links to my exercise videos on stretching the superficial back line