Objective.—It is well established that a combination of factors, including ethnicity, may influence an individual's response to cold stress. Previous work from our laboratory has demonstrated that when faced with a cold challenge, there is a similar response in heat production between Caucasian (CAU) and African American (AA) individuals that is accompanied by a differential response in core temperature. The objective of this study was to evaluate the influence of ethnicity (CAU vs AA) on the thermoregulatory response after acute cold exposure (ACE-REC, 25°C air).

Methods.—Five AA males (20.8 ± 0.5 years) and 10 CAU males (25.6±4.9 years) underwent pre-experimental testing to determine Vo_2max (AA = 37.2 ± 0.1 mL·kg⁻¹·min⁻¹, CAU = 44.3 ± 8.7 mL·kg⁻¹·min⁻¹) and body composition (AA = 14.6 ± 5.4%, CAU = 19.2 ± 5.0%). Participants underwent acute cold exposure that consisted of 120 minutes of exposure to 10°C air (ACE) followed by 120 minutes of recovery in 25°C air (ACE-REC). Rectal temperature (T_re) was measured via a rectal thermistor. Mean skin temperature (T_sk) was assessed with thermistors. Oxygen consumption (Vo₂) was assessed via indirect open circuit spirometry. Rectal temperature and T_sk were measured continuously, and if T_re ≤ 35°C, testing was terminated.

Results.—Analysis of variance for ACE-REC revealed a significant main effect for T_sk across time (P < .001), T_re across time (P < .001), and Vo₂ across time (P < .001). In addition, a significant time × ethnicity interaction was revealed for T_re (P = .008), T_sk (P = .042), and Vo₂ (P = .019) during ACE-REC.

Conclusions.—Based on these data, there is a differential response between CAU and AA across time for Vo₂, T_re, and T_sk ACE-REC.