Table 1. Criterion Validity between ECG and the Polar Vantage watch throughout the Bruce Protocol.

Day 1		95% Confidence Interval		Day 2		95% Confidence Interval
Stages	ICC	Lower Bound	Upper Bound	Stages	ICC	Lower Bound	Upper Bound
0	0.826	0.627	0.919	0	0.735	0.370	0.883
1	0.778	0.518	0.897	1	0.880	0.740	0.945
2	0.878	0.729	0.944	2	0.800	0.396	0.921
3	0.561	0.036	0.779	3	0.250	−0.273	0.603
4	0.623	0.183	0.826	4	0.141	0.426	0.538
5	0.313	−0.332	0.696	5	0.364	−0.315	0.728