Figure 4.

The dynamics of core temperature as a function of time and level of activity intensity. (a) For sunny outdoor environment of Singapore, (b) for cloudy outdoor conditions of Singapore, (c) for cloudy morning conditions with air velocity $V_{\mathit{air}}=3.9$m/s $=$ 14 km/h equivalent to air velocity around running person (vigorous physical activity). Contour lines indicate the regimes of activity intensity and its duration resulting in the same value of core temperature $T_{\mathit{core}}$. $T_{\mathit{core}}>38.0^{\circ }\text{C}$ is predicted by our model to have detrimental effects on the performance of immune response. Thus, intensity and duration of activity in a given environment, for which $T_{\mathit{core}}$ exceeds 38.0 ${}^{\circ }\text{C}$, should be avoided to minimise the risk of compromising the immune system.