Page 42 - OHS, July/August 2024

PPE: FOOT PROTECTION
parameters up and down, called size grad- ing in the industry, it is a challenge to make the product conform to a wide variety of potential users. The typical safety toe design increases the volume of the forefoot and reduces the arch height to compensate. As women tend to have higher arches than men (with the same length foot), this proves prob- lematic. Recent evidence suggests footwear designed to wrap over the instep can improve fit, enhancing efficiency during rapid chang- es of direction and movement on uneven terrain5. Female consumers should explore brands, widths, and models to find products that provide sufficient heel hold, width to al- low toe splay, and a conforming fit that wraps around their arch and instep while approxi- mately matching the length of their foot.
Reducing Injury Risk with Proper Fit
Lateral ankle sprains are the most prevalent injury in physically active populations10, occurring when the foot inverts (sole of the foot turning inward) so quickly the mus- cular system cannot react to stop it. Some evidence demonstrating that women may have greater ankle laxity than men11, put- ting them at higher risk for sprains.
A popular solution to reduce ankle sprains is using hard and stiff materials to prevent the lateral inversion of the foot. However, stiff material can also decrease movement efficiency as users struggle to overcome the rigidity of the brace. If boots have overly stiff soles and shafts, workers move with excessive plantar pressures on the metatarsal heads12, putting them at increased risk for stress fractures and ankle sprains.
Moreover, there is a documented link be- tween occupational footwear and musculo- skeletal injuries, potentially from inadequate ankle stability or the overuse of compensa- tory muscles to make up for inadequate fit13. Boots with a stiff upper cuff can inadver- tently increase trip, slip, and fall risk due to challenging workers’ dynamic balance13.
In contrast, Honert and colleagues found benefits in footwear designed to conform and wrap over the midfoot, with ankle stability improving by up to 5 per- cent and heel hold increasing by up to 2 percent5. To provide the greatest benefit to workers, boots should balance an ap- propriately stiff cuff with flexibility for the lower limb, allowing workers to regain stability quickly and prevent ankle injury. Much like ski boots which have specific stiffness profiles based on the mass, flex-
ibility, and sex of the user, female consum- ers should find a boot that augments their body geometry and flexibility.
A majority of workers report musculo- skeletal pain because of their occupation. Female workers can reduce the likelihood of experiencing this pain by searching for optimally fitting and conforming footwear. Footwear brands also play an important role in improving safety and efficiency for female workers. They should take male and female average foot shapes into account when building lasts and improve foot-shoe coupling. Moreover, footwear designed to
REFERENCES
conform and wrap around the instep and lower limb, in contrast to highly stiff boots, can enhance ankle stability and efficiency. Workers and manufacturers must priori- tize fit alongside safety features to enhance performance and reduce injury risks.
Dan Feeney, Senior Director of Partner Prod- uct Innovation and Development for BOA Technology, holds a Ph.D. in Neuromechanics from the University of Colorado Boulder and is focused on driving the future of fit and per- formance in footwear through field and lab testing across work and sport.
1. Dobson JA, Riddiford-Harland DL, Bell AF, Steele JR. Work boot design affects the way workers walk: A systematic review of the literature. Appl Ergon. 2017 May;61:53-68. doi: 10.1016/j. apergo.2017.01.003. Epub 2017 Jan 19. PMID: 28237020.
2. Krauss I, Valiant G, Horstmann T, Grau S. Comparison of female foot morphology and last design in athletic footwear--are men’s lasts appropriate for women? Res Sports Med. 2010 Apr;18(2):140-56. doi: 10.1080/15438621003627216. PMID: 20397116.
3. Jurca A, Žabkar J, Džeroski S. Analysis of 1.2 million foot scans from North America, Europe and Asia. Sci Rep. 2019 Dec 16;9(1):19155. doi: 10.1038/s41598-019-55432-z. PMID: 31844106; PMCID: PMC6914786.
4. Mündermann A, Stefanyshyn DJ, Nigg BM. Relationship between footwear comfort of shoe inserts and anthropometric and sensory factors. Med Sci Sports Exerc. 2001 Nov;33(11):1939-45. doi: 10.1097/00005768-200111000-00021. PMID: 11689747.
5. Honert EC, Harrison K, Feeney D. Evaluating footwear “in the wild”: Examining wrap and lace trail shoe closures during trail running. Front Sports Act Living. 2023 Jan 6;4:1076609. doi: 10.3389/ fspor.2022.1076609. PMID: 36685056; PMCID: PMC9853429.
6. Dobson JA, Riddiford-Harland DL, Bell AF, Steele JR. Are underground coal miners satisfied with their work boots? Appl Ergon. 2018a Jan;66:98-104. doi: 10.1016/j.apergo.2017.08.009. Epub 2017 Aug 29. PMID: 28958436.
7. Dobson JA, Riddiford-Harland DL, Bell AF, Wegener C, Steele JR. Effect of work boot shaft stiffness and sole flexibility on lower limb muscle activity and ankle alignment at initial foot-ground contact when walking on simulated coal mining surfaces: Implications for reducing slip risk. Appl Ergon. 2019 Nov;81:102903. doi: 10.1016/j.apergo.2019.102903. Epub 2019 Aug 1. PMID: 31422260.
8. Dobson JA, Riddiford-Harland DL, Bell AF, Steele JR. The three-dimensional shapes of underground coal miners’ feet do not match the internal dimensions of their work boots. Ergonomics. 2018b Apr;61(4):588-602. doi: 10.1080/00140139.2017.1397201. Epub 2017 Nov 3. PMID: 29065793.
9. Wunderlich RE, Cavanagh PR. Gender differences in adult foot shape: implications for shoe design. Med Sci Sports Exerc. 2001 Apr;33(4):605-11. doi: 10.1097/00005768-200104000-00015. PMID: 11283437.
10. Gribble PA, Bleakley CM, Caulfield BM, Docherty CL, Fourchet F, Fong DT, Hertel J, Hiller CE, Kaminski TW, McKeon PO, Refshauge KM, Verhagen EA, Vicenzino BT, Wikstrom EA, Delahunt E. Evidence review for the 2016 International Ankle Consortium consensus statement on the prevalence, impact and long-term consequences of lateral ankle sprains. Br J Sports Med. 2016 Dec;50(24):1496-1505. doi: 10.1136/bjsports-2016-096189. Epub 2016 Jun 3. PMID: 27259753.
11. Wilkerson RD, Mason MA. Differences in men’s and women’s mean ankle ligamentous laxity. Iowa Orthop J. 2000;20:46-8. PMID: 10934624; PMCID: PMC1888743.
12. Dobson JA, Riddiford-Harland DL, Bell AF, Wegener C, Steele JR. Effect of shaft stiffness and sole flexibility on perceived comfort and the plantar pressures generated when walking on a simulated underground coal mining surface. Appl Ergon. 2020 Apr;84:103024. doi: 10.1016/j. apergo.2019.103024. Epub 2020 Jan 10. PMID: 31983394.
13. Orr R, Maupin D, Palmer R, Canetti EFD, Simas V, Schram B. The Impact of Footwear on Occupational Task Performance and Musculoskeletal Injury Risk: A Scoping Review to Inform Tactical Footwear. Int J Environ Res Public Health. 2022 Aug 27;19(17):10703. doi: 10.3390/ ijerph191710703. PMID: 36078419; PMCID: PMC9518076.
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