Heart rate recovery and aerobic endurance capacity in cancer survivors: interdependence and exercise-induced improvements
Whilst evidence supports beneficial effects of exercise on heart rate variability in cancer patients, its impact on heart rate recovery (HRR) and possible associations of exercise capacity and HRR have not yet been investigated. We aimed to evaluate the effects of an exercise intervention on HRR in relation to the baseline aerobic capacity. Cancer patients (n = 309, 178 females) performed a cardiopulmonary exercise test at baseline and at a 4-month interval follow-up with home-based and supervised exercise programs in-between. VO2 and heart rate were assessed during and HRR at 60 and 120 s after test termination. Based on a median split of the VO2 peak baseline values, participants were dichotomized into two groups: below median (47 female; 57.5 ± 10 years) and above median (48 female; 54.3 ± 12 years). In the baseline sample (n = 309), VO2 peak correlated significantly with HRR60 (r = .327, p < .01) and HRR120 (r = .524, p < .01). For the compliers who completed intervention and assessments (n = 158), group comparisons demonstrated differences between below median versus above median group in absolute changes of HRR60 (3.1 ± 10.5 bpm (95 % CI +0.6; +5.4) vs −1.8 ± 8.7 bpm (95 % CI −3.7; +0.5)) and VO2 peak (2.9 ± 3.5 ml/kg/min (95 % CI +2.1; +3.7) vs 0.66 ± 4 ml/kg/min (95 % CI −0.6; +1.5)) (p < .01), but not in HRR120 (3.9 ± 11.8 bpm (95 % CI +1.2; +6.6) vs 0.8 ± 10.8 bpm (95 % CI −1.7; +3.5); p > .05). These findings point toward a positive linear relationship between aerobic capacity and vagal reactivation in cancer patients. Patients with initial VO2 peak values below median showed improved VO2 peak, HRR60 and HRR120 following the moderate aerobic exercise intervention and differences to patients above median in all outcomes compared.