Does Forefoot Strike During Running Increase Strain In The Plantar Fascia?

A recent study conducted in Hong Kong verifies a longstanding belief that runners using a forefoot strike have greater loads in the plantar fascia than those using a rearfoot strike pattern.¹ Chen and coworkers used a finite element computer model taken from magnetic resonance imaging (MRI) of a single runner and calculated loads in the plantar fascia during forefoot and rearfoot strike patterns during running. As expected, there was significant lowering of the medial longitudinal arch of the foot and increased strain in the plantar fascia when the runner switched from a rearfoot strike to a forefoot strike.

As with all scientific publications, one has to scrutinize the methodology carefully before accepting the findings and conclusions. A glaring error in my opinion was the failure of the researchers to measure the longitudinal arch angle properly.¹ The medial longitudinal arch angle is defined as the angle formed by two vectors, one passing through the midpoint of the medial malleolus to the navicular tuberosity and the other passing through the midpoint of the medial aspect of the first metatarsal head to the navicular tuberosity. The apex of the arch angle is the navicular tuberosity.² Chen and coworkers placed markers on the medial malleolus and on the first metatarsal head, but did not place a marker on the navicular, making it impossible to measure arch height or a true arch angle. Finally, the computer model neglected to introduce the influence of the plantar intrinsic muscles of the foot.

A relevant study conducted by Kelly and coworkers showed no change in arch angle and no lowering of the arch of the foot in runners using a forefoot strike versus a rearfoot strike.³ Chen did not cite Kelly’s research.¹ Kelly and coworkers appropriately placed markers on the medial malleolus, the navicular and the first metatarsal head to measure the longitudinal arch angle properly. They also used force platforms to calculate joint moments. In this study of 13 runners, there was no change in the longitudinal arch angle when comparing forefoot versus rearfoot strike pattern. The authors cited three other studies that had similar findings, showing no difference in arch deformation of the forefoot in comparison with rearfoot strike pattern during running.^4-6

Kelly and his research team, located in Queensland, Australia, have been the most prolific researchers in the world in studying the biomechanics of the medial arch of the foot.^7–9 They have demonstrated that the plantar intrinsic muscles play a key role in stabilizing the longitudinal arch of the foot during quiet standing and during locomotion. Their published studies have suggested that the central nervous system modulates the activity of the plantar intrinsic muscles to provide longitudinal arch stability.^7,9

In their recent study, Kelly and colleagues measured increased moment or torque across the midfoot joints when runners switched from a rearfoot strike to a forefoot strike.³ However, there was no change in arch height. This suggests that the plantar intrinsics were playing an important role to stabilize the arch, which should have lowered in response to the increase dorsiflexion moment measured across the midfoot. Indeed, the electromyography (EMG) portion of this study measured significant increased activity of the abductor hallucis and flexor digitorum brevis during forefoot strike running.

Kelly and coworkers appropriately conclude that increased strain of the plantar fascia can occur if activation or strength of the plantar intrinsics are compromised.³ Furthermore, the authors do not dispute the essential primary role of the plantar aponeurosis to support the medial longitudinal arch of the foot. However, forefoot strike in comparison to rearfoot strike during running does not lower the arch of the foot. Increased strain in the plantar fascia may result without lowering of the arch height but no published study has yet to measure direct measurement of strain during running with different strike patterns. Theoretically, strain will develop in the plantar fascia and this strain, at a certain point, can cause elongation of this structure with subsequent lowering of the arch of the foot. Thus far, we have not seen consistent arch lowering with a forefoot strike pattern, so the assumption that increased strain develops in the plantar fascia with forefoot strike during running cannot be verified.

In conclusion, clinicians need to be careful when making conclusions about potential harm done to certain structures in the lower extremity when evaluating foot strike patterns during running. Sound laboratory research often refutes intuitive thinking. This is why podiatric medical students and clinicians will need to stay abreast of research findings in the field of biomechanics just as they should be keeping current with new discoveries in the surgical arena.

References

1. Chen TLW, Wonga WDW, Wanga Y, Lin J, Zhang M. Foot arch deformation and plantar fascia loading during running with rearfoot strike and forefoot strike: A dynamic finite element analysis. J Biomech. 2019; 83:260–272.

2. Dahle LK, Mueller M, Delitto A, et al. Visual assessment of foot type and relationship of foot type to lower extremity injury. J Orthop Sports Phys Ther. 1991; 14(2):70–74.

3. Kelly LA, Farris DJ, LIchtwark GA, Cresswell AG. The influence of foot-strike technique on the neuromechanical function of the foot. Med Sci Sports Exerc. 2018; 50(1):98–108.

4. Perl DP, Daoud AI, Lieberman DE. Effects of footwear and strike type on running economy. Med Sci Sports Exerc. 2012; 44(7):1335–43.

5. Wager JC, Challis JH. Elastic energy within the human plantar aponeurosis contributes to arch shortening during the push-off phase of running. J Biomech. 2016;49(5):704–709.

6. McDonald KA, Stearne SM, Alderson JA, North I, Pires NJ, Rubenson J. The role of arch compression and metatarsophalangeal joint dynamics in modulating plantar fascia strain in running. PLoS One. 2016;11(4):e0152602.

7. Kelly LA, Lichtwark G, Cresswell AG. Active regulation of longitudinal arch compression and recoil during walking and running. J R Soc Interface. 2015;12(102):2014.

8. Kelly LA, Lichtwark GA, Farris DJ, Cresswell A. Shoes alter the spring-like function of the human foot during running. J R Soc Interface. 2016;13(119).

9. Kelly LA, Kuitunen S, Racinais S, Cresswell AG. Recruitment of the plantar intrinsic foot muscles with increasing postural demand. Clin Biomech (Bristol, Avon). 2012;27(1):46–51.