Barefoot bursts spread out over a morning walk is my default ‘training’ these days.
A cool autumn morning, hence the red toes, but I put in 8 short bursts ( sub 6m00s / km pace ) of about 30 strides a time.
Of those 8, only two breached my MAF* ceiling heartrate of ~ 124 bpm.
Best two were top paces of 5:19/km & 5:16/km at peak HR of 107 both times.
*MAF = Maximum Aerobic Function.
See my health / fitness dashboard demo linked at https://urbanlegend.co.nz/projects/