The higher the better? Interval training intensity in coronary heart disease.
OBJECTIVE
Peak oxygen uptake (VO2 peak) increases more after high intensity interval training compared to isocaloric moderate exercise in patients with coronary heart disease (CHD). We assessed the impact of exercise intensity during high intensity intervals on the increase in VO2 peak.


METHODS
We included 112 patients with coronary heart disease who had participated in randomized trials of interval training consisting of four times four minutes intervals at 85-95% of heart rate maximum (HRmax) for 12 weeks. Exercise intensity was calculated for each patient using HR during the two last minutes of each interval, expressed as percentage of HRmax. We used a univariate general linear model with VO2 peak increase as the dependent variable and percentage of HRmax, age, number of exercise sessions, and baseline VO2 peak as covariates. Exercise intensity was also divided into three categories; <88%, 88-92%, and >92% of HRmax, and these categories were used as a fixed factor in the model.


RESULTS
VO2 peak increased by 3.9 (SD 3.1) mL kg(-1)min(-1), equal to 11.9% after 23.4 exercise sessions. Percentage of HRmax had a significant effect on increase in VO2 peak, both as a continuous (p=0.019) and categorical variable (p=0.020). The estimated marginal means and 95% confidence intervals of the increase in VO2 peak for the three intensity categories were 3.1 (2.0, 4.2), 3.6 (2.8, 4.4), and 5.2 (4.1, 6.3) for the <88%, the 88-92%, and the >92% category, respectively.


CONCLUSIONS
Even within the high intensity training zone, exercise intensity was an important determinant for improving VO2 peak in patients with coronary heart disease.
K.G. Jebsen Center of Exercise in Medicine, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway; Department of Public Health and General Practice, Norwegian University of Science and Technology (NTNU), Trondheim, Norway. Electronic address: trine.moholdt@ntnu.no.
Trine
T
Moholdt
K.G. Jebsen Center of Exercise in Medicine, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway; Department of Cardiology, St. Olav's Hospital, Trondheim, Norway & Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
Erik
E
Madssen
K.G. Jebsen Center of Exercise in Medicine, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
Øivind
Ø
Rognmo
K.G. Jebsen Center of Exercise in Medicine, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway; Clinical Services, St. Olav University Hospital, Trondheim, Norway.
Inger Lise
IL
Aamot
D000368:Aged; D003327:Coronary Disease / Q000503:physiopathology* / Q000628:therapy*; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology
Aerobic exercise; Cardiac; Intensity; Physical fitness; Rehabilitation