Table 1.

Definition formulae of the 9 features.

Measurement Period	Feature	Formulae
3-min warm-up exercise	Resting heart rate (HRrest)	${\mathrm{HR}}_{\mathrm{rest}}=\frac{1}{3\ast 60}{\displaystyle \sum _{{\mathrm{t}=\mathrm{T}}_{\mathrm{start}}}^{{\mathrm{T}}_{\mathrm{start}+3\ast 60}}}{\mathrm{HR}}_{\mathrm{t}}$	(4)
Running	Heart rate increase rate (HRincrease)	${\mathrm{HR}}_{\mathrm{increase}}=\frac{{\mathrm{HR}}_{{\mathrm{T}}_{\mathrm{start}}+20}-{\mathrm{HR}}_{{\mathrm{T}}_{\mathrm{start}}}}{{\mathrm{EC}}_{{\mathrm{T}}_{\mathrm{start}+20}}-{\mathrm{EC}}_{{\mathrm{T}}_{\mathrm{start}}}}$	(5)
	Maximum heart rate (HRmax)	${\mathrm{HR}}_{\max }=\max \left({\mathrm{HR}}_{\mathrm{t}}\right),\mathrm{t}={\mathrm{T}}_{\mathrm{start}}\dots {\mathrm{T}}_{\mathrm{end}}$	(6)
	Heart rate reserve (HRreserve)	${\mathrm{HR}}_{\mathrm{reserve}}={\mathrm{HR}}_{\max }-{\mathrm{HR}}_{\mathrm{rest}}$	(7)
	Mean blood oxygen saturation (SpO2mean)	${\mathrm{SpO}}_{2\mathrm{mean}}=\frac{{{\displaystyle \sum }}_{{\mathrm{t}=\mathrm{T}}_{\mathrm{start}}}^{{\mathrm{T}}_{\mathrm{end}}}{\left({\mathrm{SpO}}_2\right)}_{\mathrm{t}}}{{\mathrm{T}}_{\mathrm{end}}-{\mathrm{T}}_{\mathrm{start}}}$	(8)
	Standard deviation of blood oxygen saturation (SpO2SD)	${\mathrm{SpO}}_{2\mathrm{SD}}=\sqrt{\frac{1}{{\mathrm{T}}_{\mathrm{end}}-{\mathrm{T}}_{\mathrm{start}}}{\displaystyle {\displaystyle \sum }_{\mathrm{t}={\mathrm{T}}_{\mathrm{start}}}^{{\mathrm{T}}_{\mathrm{end}}-{\mathrm{T}}_{\mathrm{start}}}}{\left({\mathrm{HR}}_{\mathrm{t}}-{\mathrm{SpO}}_{2\mathrm{mean}}\right)}^2}$	(9)
	Time duration (TD)	$\mathrm{TD}={\mathrm{T}}_{\mathrm{end}}-{\mathrm{T}}_{\mathrm{start}}$	(10)
Recovery	Heart rate descent rate (HRdecent)	${\mathrm{HR}}_{\mathrm{descent}}=\frac{{{\displaystyle \sum }}_{\mathrm{t}={\mathrm{T}}_{\mathrm{end}}}^{{\mathrm{T}}_{\mathrm{end}+10}}{\mathrm{HR}}_{\mathrm{t}}-{{\displaystyle \sum }}_{\mathrm{t}={\mathrm{T}}_{\mathrm{end}+110}}^{{\mathrm{T}}_{\mathrm{end}+120}}{\mathrm{HR}}_{\mathrm{t}}}{10}$	(11)
	Instant heart rate (HRinstant)	${\mathrm{HR}}_{\mathrm{instant}}={\mathrm{HR}}_{{\mathrm{T}}_{\mathrm{end}}}$	(12)