Are aerobic interval training and continuous training isocaloric in coronary artery disease patients?

Background Aerobic interval training (IT) seems to be superior to continuous training (CT) in improving exercise capacity (peak oxygen uptake (VO2)) in coronary artery disease (CAD) patients in some, but not in all studies. Based on theoretical calculations, these comparative studies stated that the energy expenditure (EE) of both programmes is similar. To date, the caloricity of both programmes has never been objectively measured. Therefore, our aim was to objectively measure the EE of the IT and CT programmes described in the protocol of the SAINTEX-CAD study (based on Wisloff etal.; ITw and CTw), and the actually performed training intensities in the SAINTEX-CAD study by Conraads etal. (ITc and CTc). Methods Following a two-week run-in period with three IT and three CT training sessions, 18 male CAD patients (mean age 62.46.1 years) performed four training sessions in random order on the cycle ergometer: an ITw, CTw, ITc and CTc test session. The EE was assessed by indirect calorimetry using gas exchange measurements obtained with the Oxycon mobile. Results We found a higher EE for CTc compared to ITc (352 +/- 90.8kcal versus 269 +/- 70.7kcal; p=0.026), while CTw and ITw seemed to be isocaloric (317 +/- 85.2kcal versus 273 +/- 65.3kcal; p=0.42). Higher lactate levels were reached after IT sessions (ITw 5.42 +/- 1.42mmol/l, ITc 5.05 +/- 1.38mmol/l) compared to CT sessions (CTw 2.45 +/- 1.04mmol/l, CTc 3.41 +/- 1.44mmol/l) (p<0.01). Lactate levels increased above baseline levels (1.91 +/- 0.34mmol/l) except for the CTw session. Conclusion CTc expended significantly more energy compared to ITc, showing that the programmes used in the SAINTEX-CAD study were not isocaloric. In contrast, isocaloricity was met for CTw and ITw.