The Utility of Forearm to Fingertip Skin Temperature Gradients During Measurements of Resting Energy Expenditure

Abstract

The measurement of resting energy expenditure (REE) is important to both human physiology and nutrition. There are several pre-conditions for the proper measurement of REE, but a key criterion is that it takes place in the thermoneutral zone (TNZ). Deciding whether a person is in his or her TNZ is not an easy task, and a suggested way forward is the monitoring of forearm to fingertip skin temperature gradients (FFG). In this commentary, we highlight our recent findings that FFG varies between individuals even when measured at a temperature within TNZ. Interestingly, FFG showed a consistent direct relationship with adjusted REE, in both cross-sectional and longitudinal study designs. In addition, we provide new findings that FFG is sensitive to small ambient temperature variations within the TNZ, in comparison to visual analogue scale (VAS)-derived subjective measures of thermal comfort. While further research is needed in this area, our view is measurements of FFG should be included in REE protocols. This would inform investigators on how their participants are responding to the ambient room temperature and also allow appropriate statistical adjustments in REE for between-group comparisons.

Keywords: forearm to fingertip temperature gradient; resting energy expenditure; thermogenesis; thermoneutral zone; vasoconstriction.

Figure 1.

Relationship of adjusted RMR to FFG: cross sectional data. Blue line: linear regression line with r² = 0.065; P = .018; red line: cubic regression line with r² = 0.107; P = .025. RMR (resting metabolic rate equivalent to REE) was adjusted for age, fat mass, fat free mass, and insulin sensitivity. Reproduced with permission from Pathak et al.