Heart rate recovery (HRR)

Heart rate recovery (HRR) is the drop in heart rate during the first minute (HRR1) or two minutes (HRR2) after stopping peak or symptom-limited exercise testing. Mechanistically it reflects parasympathetic (vagal) reactivation early after exercise, with sympathetic withdrawal contributing later. In the landmark Cleveland Clinic cohort of 2,428 patients undergoing treadmill testing (Cole et al., NEJM 1999), an HRR1 of 12 beats per minute or fewer (with a 2-minute cool-down) was associated in unadjusted analysis with a 4-fold higher all-cause mortality over 6 years (adjusted relative risk 2.0 after accounting for exercise capacity, beta-blockers, and standard cardiovascular risk factors). Normal HRR1 in healthy adults is typically greater than 18 bpm; values under 12 bpm are clinically abnormal. HRR is reproducible, cheap, and a useful adjunct to peak VO2.