Skin temperature thresholds: A novel non-invasive potential tool for estimating ventilatory thresholds

Background

Developing non-invasive, practical methods to identify exercise metabolic thresholds remains a key focus in exercise physiology. This study examined the variation patterns of average skin temperature (aT_sk) measured by infrared thermography during a ramp incremental exercise test (RIET) and determined skin temperature thresholds (TSKTs) to assess their agreement with ventilatory thresholds (VTs).

Methods

Twenty-three active college students performed a RIET. Physiological parameters including aT_sk, oxygen uptake ($\dot{V}{O}_2$), heart rate (HR), and power output (PO), were recorded. Paired-sample t-tests, Pearson correlation (r), Intraclass Correlation Coefficient (ICC) and Bland-Altman were used to assess the agreement between TSKTs and VTs. The TSKTs comprised the first (TSKT1) and second (TSKT2) skin temperature thresholds.

Results

1) aT_sk remained stable initially, then declined (TSKT1), and finally slowed or rebounded (TSKT2). 2) No significant differences were observed between VTs and TSKTs in $\dot{V}{O}_2$, HR, or PO (P > 0.05). 3) At the levels of absolute $\dot{V}{O}_2$ ($\dot{V}{O}_2\text{ab}$), relative $\dot{V}{O}_2$ ($\dot{V}{O}_2\text{re}$), HR and PO, TSKT1 exhibited moderate agreement with VT1, with ICC (0.587, 0.432, 0.430 and 0.525) and r > 0.40 (P < 0.05). TSKT2 showed moderate to high agreement with VT2 for $\dot{V}{O}_2\text{ab}$ (ICC: 0.774, r: 0.778) (P < 0.01), $\dot{V}{O}_2$ re (ICC: 0.433, r: 0.449) (P < 0.05), and PO (ICC: 0.770, r: 0.784) (P < 0.01), while no significant agreement and correlation was found for HR (P > 0.05).

Conclusion

TSKTs identified during RIET exhibited moderate to high reliability in estimating VTs and may serve as a potential tool for VTs assessment.