AEROBIC AND ANAEROBIC ENERGY-EXPENDITURE DURING EXHAUSTIVE RAMP EXERCISE

Ramp tests are often manipulated so that oxygen uptake is able to inte rpret energy expenditure in its entirety, We hypothesized that oxygen deficits during ramp exercise to exhaustion would be significant, prov iding a more complete description of the types of energy expenditure a vailable for this mode of testing. Oxygen deficits were obtained durin g a slow ramp (681 +/- 71 s) and a fast ramp (275 +/- 33 s) to exhaust ion. Twelve healthy men (age 35 +/- 3 yrs; VO(2m)max 51 +/- 10 ml x kg (-1) x min(-1)) performed several 10 min submaximal bike rides (at or below ventilatory threshold) to determine work rate -O-2 uptake demand s. Estimated O-2 demands were compared to measured O-2 uptake during e ach ramp test, the difference representing an oxygen deficit. Work lev els were controlled and measurements collected with a commercially ava ilable electrically braked bike ergometer and metabolic testing system (MedGraphics, Minn., MN). Data were collected and averaged in 30 s ti me periods, power in watts (W), energy expenditure in cumulative O-2 ( L). Using a paired t-test, cumulative O-2 uptakes were significantly l ower (p = 0.0001) when measured O-2 uptakes (26.0 L +/- 4.5 for slow r amp; 10.8 L +/- 2.8 for fast ramp) were compared to estimated O-2 dema nds (29.0 L +/- 3.7 for slow ramp; 14.1 L +/- 3.5 for fast ramp). Anae robic energy expenditures (oxygen deficits) represented 10.8% and 23.4 % of total energy expenditure for slow ramps and fast ramps, respectiv ely. Comparisons of the slopes for each test condition revealed signif icant differences (steady state > slow ramp > fast ramp; p = 0.0001,AN OVA). We conclude that the oxygen deficit during ramp testing represen ts a significant part of total energy expenditure.