## 4 Conclusions  
The main goal of this study was to gain more physiological and mechanistic insights into the underlying processes of thermoregulatory localised CIVC/CIVD reactions using a data-based mechanistic modelling (DBM) approach. Two types of localised cooling were applied on the fingers of 33 healthy participants (test subjects), namely, continuous and intermittent cooling, during the course of the conducted experiments. During the first set of experiments. The results showed that 27 participants out of 33 showed clear evidence of the hunting reaction (i.e., cycles of CIVC/CIVD episodes) during continuous localised cooling. Two different, yet connected, thermoregulatory reactions representing the hunting reaction, namely, CIVC and CIVD were mathematically modelled and described as two separate processes or dynamic systems using the DBM approach. A second-order discrete-time transfer function (two poles and two zeros) was the best (\(R_{2}^{T}\) = 0.91 \(\pm\) 0.06 and \(YIC\) = \(-11.43\)\(\pm\) 2.65) for mathematically representing the dynamic responses of the finger skin temperature to step localised cooling and for describing both CIVC and CIVD reactions. For both reactions, it was possible to decompose the obtained second-order system into two first-order TF systems in parallel configurations. The calculated time constants from the two first-order systems suggested two underlying processes for both CIVC and CIVD reactions, one of which is almost 10 times faster. Mechanistic and physiological insights into the suggested underlying processes suggested that the slower (with average \(\tau\) = 7.36 min) process represents slow convective heat transfer from the capillaries and the conductive heat exchange between the skin and Peltier's elements. On the other hand, the faster process represents the closing/opening of the AVAs during the CIVC/CIVD reactions, which causes a fast change in the  
Figure 13: Flow chart explaining the suggested model of thermoregulatory localised CIVC/CIVD reactions.  
convective heat transfer from the superficial veins. During the intermittent localised cooling, no test subjects of Exp.2 (in total 12) showed any episodes of CIVD, although the skin temperature reached the same level (\(16.2\pm 0.7\)\({}^{\circ}\)C) as that under continuous cooling. A new term is suggested in this paper, namely, the latent heat of CIVD (LH-CIVD), which represents the amount of dissipated heat required to trigger the CIVD. It should be stated here that the identified models are limited to the presented methodology of localized cooling. Additionally, in future investigations, interpersonal variations (e.g., physiological and anthropometric variations) should be considered and studied. Moreover, the present work suggested a new model for the thermoregulatory localised CIVC/CIVD reactions. The new model suggested states that, with an initial vasodilation state, the initial localised CIVC is triggered not based on skin temperature threshold, but rather on a certain threshold in the rate of heat dissipation from the skin to the surrounding environment.  
Conceptualisation, A.Y. and J.-M.A.; methodology, A.Y. and A.V.; software, A.Y. and A.V.; validation, A.Y.; formal analysis, A.Y. and A.V.; investigation, A.Y. and A.V.; resources, G.D.B and J-N.A.; data curation, A.Y. and A.V.; writing--original draft preparation, A.Y. and A.V.; writing--review and editing, A.Y. and J.-M.A.; visualisation, A.Y.; supervision, J.-M.A. and A.Y.; project administration, J.-M.A.; funding acquisition, J.-M.A. This research received no external funding.  
The authors declare no conflict of interest.