The Monday Shakeout: The Importance of Toe Box Width
By Andrea Myers
In this week's shakeout, Andrea aessess research to discuss why generous toe box widths are so valuable for many runners.
Toe box width is one of the most important features of a shoe for me. When I am testing a shoe, if it is too narrow or too low volume in the forefoot, I am likely to get pain at my 1st or 5th MTP joints or even plantar fasciitis-type pain. While I do not have a wide foot overall, I have short toes relative to my foot length, which means that the widest part of my forefoot sits further forward in a shoe as compared to those with more proportional toe length. This makes me particularly sensitive to shoes that taper significantly in the toe box. The shoes that work best for me are any shoe in the Topo line, the Brooks Hyperion Max, the New Balance Beacon v3 (RIP), and the Nike Vaporfly v3. I also find that shoes with a knit or mesh upper are more comfortable as compared to shoes with forefoot sidewalls or overlays.
Besides the obvious (your shoe should be shaped like your foot, not squeeze your toes together), what does the scientific literature say about the benefits of a wide toe box?
Researchers at Brigham Young University evaluated the effect of passive hallux adduction (pushing the big toe outwards, towards the other toes) on blood flow in the lateral plantar artery. They hypothesized that this positioning would result in decreased blood flow in the artery, which supplies the plantar fascia. They proposed that the abductor hallucis muscle may play a role in this arterial compression. The abductor hallucis runs along the medial aspect of the foot and moves the big toe away from the second toe. Putting the abductor hallucis in a lengthened position may compress the posterior tibial artery, which feeds the lateral plantar artery. Evidence is emerging that the persistent nature of plantar fasciitis may be a result of decreased blood flow to the plantar fascia, which slows healing. Poor fitting running shoes that are too narrow across the forefoot could cause passive hallux adduction and could be a contributing factor to the development and persistence of plantar fasciitis.
The researchers used ultrasound to quantify blood flow and vessel diameter in the lateral plantar artery with the foot in a resting position and with the big toe pushed towards the other toes (hallux adduction). They found a statistically significant decrease in blood flow and artery diameter during passive hallux adduction. They also found that the decrease in blood flow was greatest in subjects with pes planus (low arch), which they theorized was due to lengthening of the abductor hallucis muscle in flat footed individuals. The role of reduced blood flow in the development of plantar fasciitis needs further research, but the preliminary evidence suggests that narrow footwear could reduce blood flow in the lateral plantar artery.
The take home message here is that regardless of drop, shoes should be wide enough at the toe box to allow for normal toe splay. A simple way for runners to test if their shoes are too narrow is to remove the shoe insert and stand on them. If the foot is wider than the insert, the shoes may be too narrow.
A second consideration regarding toe box width is the potential link between hallux valgus (a condition in which the big toe points towards the second toe, which often results in a bunion) and patellofemoral pain. It is well-established that people who regularly wear shoes that are too narrow across the forefoot are at increased risk of developing hallux valgus (Ray et al 2019). Researchers at Northumbria University examined the relationship between hallux valgus and knee and foot motion during running (Stoneham et al 2020). They specifically looked at whether runners with an increased hallux valgus angle (big toe angled towards the second toe) demonstrated increased pronation and/or knee frontal plane motion (which is side to side motion of the knee, also known as varus or valgus). They assessed 15 runners (10 male, 5 female) as they ran barefoot over a 20 meter runway for gait analysis using 14 optoelectronic cameras. The authors stated they used barefoot running to allow proper visualization of the great toe during the running trial. Prior to the run trial, the subjects underwent full static anthropometric analysis, including lower limb structure and alignment. To habituate the subjects to barefoot running, each subject completed a 30 minute warmup run prior to the 20 meter runway trial.
The researchers found a strong association between hallux valgus angle and knee frontal plane motion during running. For every 1° increase in hallux valgus angle, there was a 0.24° increase in knee frontal plane motion. There was also a strong association between an increased hallux valgus angle and increased pronation. Research is mixed regarding the relationship between increased pronation during running and patellofemoral pain. Additionally, motion control shoes have not been found to reduce patellofemoral pain in runners (Cheung et al 2006). Previous studies have found a relationship between increased knee frontal plane motion and patellofemoral pain (Nakagawa et al 2012, Dierks et al 2008).
From a biomechanical perspective, hallux valgus reduces the amount of available extension at the 1st MTP joint. 1st MTP extension is essential for normal push off during running, and if it is not available, the body will steal motion from somewhere else (such as the increased knee frontal plane motion and increased foot pronation seen in the Stoneham study). While the results from the Stoneham paper are from barefoot runners, the results could be applied to shod runners as well. If a runner has hallux valgus, they will steal motion from another joint, regardless of whether they are barefoot or shod. A shod runner may be more likely to compensate at the knee, particularly if a shoe has a high amount of toe spring that exceeds that person’s available 1st MTP extension range of motion. The simplest thing a runner can do to reduce their risk of developing hallux valgus is to ensure they are wearing shoes (both running and casual) that are wide enough for their forefoot.
References
Jacobs, J. L., Ridge, S. T., Bruening, D. A., Brewerton, K. A., Gifford, J. R., Hoopes, D. M., & Johnson, A. W. (2019). Passive hallux adduction decreases lateral plantar artery blood flow: a preliminary study of the potential influence of narrow toe box shoes. Journal of foot and ankle research, 12, 50.
Ray, J. J., Friedmann, A. J., Hanselman, A. E., Vaida, J., Dayton, P. D., Hatch, D. J., Smith, B., & Santrock, R. D. (2019). Hallux Valgus. Foot & ankle orthopaedics, 4(2), 2473011419838500.
Stoneham, R., Barry, G., Saxby, L., & Wilkinson, M. (2020). The influence of great toe valgus on pronation and frontal plane knee motion during running. Foot and Ankle Online Journal, 13(1), 7.
Nakagawa, T. H., Moriya, É. T., Maciel, C. D., & Serrão, A. F. (2012). Frontal plane biomechanics in males and females with and without patellofemoral pain. Medicine and science in sports and exercise, 44(9), 1747–1755.
Dierks, T. A., Manal, K. T., Hamill, J., & Davis, I. S. (2008). Proximal and distal influences on hip and knee kinematics in runners with patellofemoral pain during a prolonged run. The Journal of orthopaedic and sports physical therapy, 38(8), 448–456.
Cheung, R. T., Ng, G. Y., & Chen, B. F. (2006). Association of footwear with patellofemoral pain syndrome in runners. Sports medicine (Auckland, N.Z.), 36(3), 199–205.
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