Race is used to group people based on physical features, social identity, and cultural background (National Human Genome Research Institute, 2022). It is important to note that race is very complex, and due to its social construction, its definition has evolved throughout history (Bhopal, 2004; National Academies of Sciences Engineering and Medicine et al., 2017). However, race is a salient factor when looking at health inequities that contribute to the health disparities by race (Bhopal, 2004). For example, diabetes ranks seventh in the leading causes of death for people in the United States (CDC, 2022a, Cdc, 2022). While the total number of individuals diagnosed with diabetes has doubled in the past two decades, data shows that diabetes is more likely to occur to racial/ethnic minority groups than White Americans (Price et al., 2013). So, when we want to solve these health inequities, it is important that we factor in race (Bhopal, 2004, Burchard et al., 2009).

One group that is detrimentally affected by diabetes is African Americans (AA). AA are more likely to die from diabetes than White Americans (WA) (Office of Minority Health Resource Center, 2021), along with having worse management of diabetes symptoms and higher rates of diabetic complications than WA (Marshall, 2005). An example of a serious complication of diabetes is foot ulcers, which occur due to poor circulation and neuropathy in the foot (Oliver and Mutluoglu, 2022). AA are more likely than WA to experience diabetic foot ulcers (Tan et al., 2020). Oftentimes, these ulcers become infected and do not heal, requiring foot amputation and at times even lead to death (Lefebvre and Lavery, 2011, Oliver and Mutluoglu, 2022). Diabetic foot ulceration is usually caused by high plantar pressure which can be exacerbated by diabetic foot neuropathy (Abri et al., 2019). The current literature suggests that individuals with diabetic foot ulcers have higher plantar pressure than those without diabetic foot neuropathy and no diabetes (Fernando et al., 2016). Those with diabetic peripheral neuropathy can also continue to have high plantar pressure after the ulcer has been resolved. Treatment for diabetic foot ulcers can include off-loading using shoes, casts, and/or orthotic devices (de Oliveira and Moore, 2015), as increased plantar pressure is believed to have caused the foot ulcers.

The current literature suggests that plantar loading is impacted by a variety of factors. One example is sex, given the known differences in foot characteristics, particularly arch height, rearfoot width, and hallux height, which can lead to differences in plantar pressure (Wunderlich and Cavanagh, 2001). Men were reported to have a significantly higher contact area than women, along with force-time integral being higher in the 1st, 3rd, and 4th metatarsal head (MTH) during walking. In addition, maximum force was reported to be higher in the rearfoot, 1st MTH and 3rd MTH in men (Putti et al., 2010). Differences in plantar loading have also been seen between foot types: pes planus (flat foot), pes rectus (normal arch), and pes cavus (high arch) (Buldt et al., 2018, Chuckpaiwong et al., 2008, Queen et al., 2009). For pes planus feet, higher maximum force, force-time integral, and contact area are displayed in the medical arch, central forefoot, and hallux, with lower maximum force, force-time integral, and contact area are reported in the rearfoot and lateral forefoot. Pes cavus feet display lower maximum force, force-time integral and contact area in the midfoot and hallux. Pes cavus feet display a more laterally deviated center of pressure while pes planus feet display a more medial center of pressure (Buldt et al., 2018).

Other variables that contribute to changes in plantar loading include gait speed, BMI, and age. Gait speed has also been identified as a variable that can affect plantar loading (Rosenbaum et al., 1994). Prior literature has reported that increased gait speed can contribute to higher peak plantar pressures in the hallux, 1st MTH, 2nd MTH, 3rd MTH, and the rearfoot. An increase in gait speed was also correlated with a decrease in peak plantar pressure beneath the 5th MTH (Rosenbaum et al., 1994). Higher BMI has also been seen as a risk factor for higher plantar pressure, with a higher BMI correlating to higher pressure in the lateral forefoot and midfoot, and lower pressure in the medial heel (Tománková et al., 2017). Lastly, there have been differences in plantar loading seen between young adults and older adults, with younger adults exhibiting statistically higher plantar pressure in the midfoot and statistically higher force-time integral in the midfoot and hallux region (Kernozek and LaMott, 1995).

Racial differences have been observed in diabetes neuropathy and foot type. AA are more likely to suffer from diabetic foot neuropathy than WA (Frykberg et al., 1998, Office of Minority Health Resource Center, 2021). Given that plantar loading is associated with diabetic foot ulcers, there is a need to know if there are racial differences in plantar loading in a younger, non-diabetic population. Additionally, it is important to consider other factors that could explain potential differences in plantar loading by race. In a study by Golightly et al., it was found that there are racial differences in foot types, particularly between AA and WA (Golightly et al., 2012). Research shows that AA are three times as likely to have pes planus feet than WA, and five times less likely to have pes cavus feet than WA (Golightly et al., 2012). It is also known that AA have a slower gait speed than WA (Hill et al., 2020; Kirkness and Ren, 2015) and that people with a family history of diabetes are more likely to develop diabetes or have prediabetes (CDC, 2022b). The risk for diabetes due to family history is compounded by obesity and if the person is AA (CDC, 2022b).

Previous research has indicated the importance of taking into consideration how variables such as sex, arch height, gait speed, family history of diabetes, BMI, and age can affect plantar loading. Thus, the purpose of this study was to determine whether race in combination with family history of diabetes, sex, arch height, BMI, gait speed, and age influences plantar loading. Based on the current literature, we hypothesized that race, arch height, and sex will be significant predictors of plantar loading parameters.