Long description

This figure shows two graphs, each with a vertical axis (labelled ‘Number of sessions’) and a horizontal axis (labelled ‘Zone 1’, ‘Zone 2’ and ‘Zone 3’). Graph E shows the threshold model of training with an inverted U-shape with few sessions in Zone 1 and Zone 3 and lots of sessions in Zone 2. Graph F shows the polarised model of training with many sessions in Zone 1 and few in Zones 2 and 3.