Effect of Computational Method on Accumulated O Deficit.

The aim of this study was to examine how relationships between exercise intensity and the rate of energy release established in different ways, affect the calculated O deficit accumulated during strenuous exercise. Aerobic energy release is readily measured by the O uptake, while anaerobic energy release is by definition independent of O. The latter is not easily measured during strenuous exercise, but it can be estimated using the accumulated O deficit principle. We have calculated it using nine different approaches. Thirteen moderately trained persons (three women) volunteered to serve as subjects for cycle ergometry. Their maximal O uptake was 2.9 ± 0.6 mmol s ( ± ; 3.9 ± 0.8 L min). Our reference method (M0) is based on measuring the steady state O uptake at the end of at least ten bouts of 10 min of exercise at constant intensity, varying between 30 and 40% of that corresponding to the maximal O uptake and up to a power >90% of the maximal O uptake, which is a rather time-consuming method. The outcomes of eight different simpler approaches have been compared with those of the reference method. The main result is that the accumulated O deficit calculated depends a great deal on the relationship used to calculate it. A protocol of stepwise increases in exercise intensity every 4 min appeared to work well. A gross efficiency method showed the poorest performance. Another important result is that at constant power the O uptake continued to increase beyond 4 min of exercise at all powers examined, also at powers well-below those corresponding to the lactate threshold. Finally, the O uptake during loadless pedaling was considerably higher than resting O uptake, and it appeared to follow a cubic function of the pedaling frequency. In conclusion, to obtain reliable values of the anaerobic energy release using the accumulated O deficit principle, reliable relationships between exercise intensity and O demand must be established.