Asymmetric Thermal Response of Human Feet to Hopping Detected by Digital Infrared Imaging

Aims: The purpose of this study was to evaluate the effect of asymmetric exercise, hopping, on skin temperature at the foot and ankle subregions by infrared thermography.
Study Design: Prospective volunteer study.
Place and Duration of Study: Department of Orthopaedic Surgery and Department of Radiology, Chung-Ang University Hospital, between June 2013 and March 2014.
Methodology: Ten healthy male volunteers hopped with their dominant limb 1,000 times or for 15 min. Thermography was taken by using an infrared imaging device at 24°C. Each volunteer had four thermographic images of the dorsum, plantar and calf views of both limbs before hopping, and at 5, 20 and 30 min after hopping. Temperatures were measured at the dorsum of the foot (subregion 1), lower tibialis anterior (subregion 2), medial plantar (subregion 3), lateral plantar (subregion 4), calf (subregion 5) and Achilles tendon (subregion 6).
Results: Hopping changed the temperature with different patterns depending on 12 subregions after hopping. At 5 min, except for subregion 3 and 4 of the hopping limb, the other ten subregions showed decreases in skin temperature. Temperatures of all subregions of the hopped limb were higher than that of non-hopped limb ranging from the lowest, 0.54°C atsubregion 1 at 5 min, to the highest, 1.18°C atsubregion 6 at 5 min. Each subregion of the hopped limb was 0.5°C or higher than that of non-hopped limb from 5 till 30 minutes after exercise (P < 0.05).
Conclusion: Heat changes in the foot and ankle by exercise can be imaged and evaluated. After asymmetric exercise, hopping, the subregions of the foot and ankle respond differently. For proper image interpretation, knowing whether asymmetric exercise occurred in the limb of interest is important before image acquisition.