Table 1.

Phases, intensity, %HRmax (percentage maximal heart rate), and perceived exertion (RPE), adapted from Garber et al. 2011. ³¹

Phase	Intensity (Borg scale)	%HRmax	Perceived exertion (on 6–20 RPE scale)	Metabolic equivalents (MET)
1	Not strenuous at all to very light	until 50	6–8/20	<2.5
2	Very light to light	50–60	9–10/20	2.5–3.0
3	Fairly light to somewhat hard	60–75	11–13/20	3.0–5.0
4	Very hard	75–90	14–16/20	5.0–8.0