Obese Patients Decrease Work Rate in Order to Keep a Constant Target Heart Rate

Purpose: Slow components of heart rate (HR) kinetics, occurring also during moderate-intensity constant work rate exercise, represent a problem for exercise prescription at fixed HR values. This problem, described in young healthy subjects, could be more pronounced in obese patients. Methods: Sixteen male obese patients (age, 22 +/- 7 yr; body mass, 127 +/- 19 kg; body mass index, 41.6 +/- 3.9 kg.m(-2)) were tested before (PRE) and after (POST) a 3-wk multidisciplinary body mass reduction program, entailing moderate-intensity exercise. They performed on a cycle ergometer an incremental exercise to voluntary exhaustion (to determine peak pulmonary oxygen uptake ((V) over barO(2peak)) and gas exchange threshold (GET)) and constant work rate exercises: moderate-intensity (MODERATE; 80% of GET determined in PRE), heavy-intensity (HEAVY; 120% of GET determined in PRE), and HRCLAMPED exercise, in which work rate was continuously adjusted to maintain a constant HR corresponding to that at 120% of GET. Breath-by-breathVO(2) and HR were determined. Results: (V) over barO(2peak) and GET (expressed as a percent of (V) over barO(2peak)) were not significantly different in PRE versus POST. In POST versus PRE, the HR slow component disappeared (MODERATE) or was reduced (HEAVY). In PRE, work rate had to decrease by similar to 20% over a 15-min task in order to keep HR constant; this decrease was significantly smaller (similar to 5%) in POST. Conclusions: In obese patients, a 3-wk multidisciplinary body mass reduction intervention i) increased exercise tolerance by eliminating (during MODERATE) or by reducing (during HEAVY) the slow component of HR kinetics, and ii) facilitated exercise prescription by allowing to translate a fixed submaximal HR value into a work rate slightly above GET.

Automated summary

In obese patients, a 3-week multidisciplinary body mass reduction intervention increased exercise tolerance by eliminating or reducing the slow component of heart rate kinetics, facilitating exercise prescription by translating a fixed submaximal heart rate value into a work rate slightly above gas exchange threshold.