Rice farming is conducted in slippery and viscous muddy soil, which leads to a high prevalence of musculoskeletal disorders and malalignments. Over half of Thailand’s farm labor force is engaged in rice farming, making these occupational challenges a public health burden. Thai researchers from Khon Kaen University hypothesized that interventions originally designed for congenitally disabled individuals, such as corrective wedges to reduce foot eversion, might be applicable to rice farmers. In a study published in the journal Foot, these researchers sought to investigate the effects of corrective wedges on lower extremity muscle activity and alignment when study participants stood on flat rigid ground or muddy terrain, simulating the work conditions of rice farmers.
The study recruited 9 healthy farmers with pronated feet and custom-fabricated wedges for each farmer based on physical therapy assessment and use of rapid prototyping techniques. Participants then stood barefoot or with wedges on the two surface types.
Foot pronation and knee valgus improved (ranging, on average between 5.5 and 16.1 degrees) when participants were equipped with corrective wedges. The muscle activity of the peroneus longus and the tibialis anterior increased for muddy terrain, as compared with the rigid surface. In general, the wedges induced less tibialis anterior activity and greater peroneus longus activity, compared to when participants were standing barefoot. An elevation in evertor muscle activity may reflect stretching of the shortened muscle as a result of the reduced degree of foot pronation.
The researchers concluded that there are potential benefits of corrective insole usage for farmers with pronated feet, including improved lower extremity alignment and invertor muscle activity reduction for both rigid and muddy terrains.
Source: Kristanto A, Neubert MS, Gross MT, Puntumetakul R, Kaber DB, Sessomboon W. Effects of corrective insole on leg muscle activation and lower extremity alignment in rice farmers with pronated foot: a preliminary report. Foot (Edinb). 2020 Dec 25;46:101771. doi: 10.1016/j.foot.2020.101771.