Fuel utilization is reflected in exercise intensity, and maximal fat oxidation (FatOx) reflects intensity and caloric expenditure. FatOx was measured using indirect calorimetry (TrueOne® 2400 Metabolic Measurement System, ParvoMedic). Eight apparently healthy college-aged female participants completed the following 3 minute graded 7 stage protocol on a normal treadmill (NT) and the Alter G® treadmill (AGT) at 80% of normal body weight: standing, warm-up at 58.96 m·min-1, and exercise at 88.44 m·min-1 with a 3% grade increase per stage. Metabolic data were collected every 15 seconds. Steady state (SS) was considered the last minute of each stage. Participants completed all 7 stages or when the respiratory exchange ratio (RER) value reached 0.95. FatOx rate was calculated based on SS oxygen consumption (VO2) and carbon dioxide production (VCO2) values. Maximal average (±SD) FatOx rates on the normal treadmill was 0.51 ± 0.09 g·min-1 at stage 4 with a significant decrease from stages 6 to 7. Maximal average FatOx rates on the AGT was 0.36 ± 0.10 g·min-1 at stage 6. Fat oxidation was less on the AGT with no apparent maximal FatOx. The current exercise protocol may be too easy to achieve maximal fat oxidation on the AGT.
Fuel utilization, maximal fat oxidation (FatOx), indirect calorimetry, Transformations