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 (CWR) 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 years; body mass: 127±19 kg; body mass index: 41.6±3.9 kg·m) were tested before (PRE) and after (POST) 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 V[Combining Dot Above]O2peak and gas exchange threshold [GET]) and CWR exercises: moderate-intensity (MODERATE) (80% of GET determined in PRE); heavy-intensity (HEAVY) (120% of GET determined in PRE); "HRCLAMPED" exercise, in which work rate was continuously adjusted to maintain a constant HR corresponding to that at 120% of GET. Breath-by-breath V[Combining Dot Above]O2 and HR were determined. RESULTS V[Combining Dot Above]O2peak and GET (expressed as a % of V[Combining Dot Above]O2peak) were not significantly different in PRE vs. POST. In POST, vs. PRE, the HR slow component disappeared (MODERATE) or was reduced (HEAVY). In PRE work rate had to decrease by ~20% over a 15-min task in order to keep HR constant; this decrease was significantly smaller (~5%) in POST. CONCLUSION 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; ii) facilitated exercise prescription by allowing to translate a fixed submaximal HR value into a work rate slightly above GET.