A person's approximate caloric expenditure for each liter of oxygen used is ____

The approximate caloric expenditure for each liter of oxygen consumed is generally accepted to be around 5 kilocalories. This estimation comes from the understanding of how our bodies utilize oxygen during metabolic processes, particularly in aerobic activity. When we consume oxygen, it aids in the breakdown of carbohydrates and fats to produce energy, and on average, one liter of oxygen consumed corresponds to an energy expenditure of approximately 5 kilocalories. This is a useful metric for calculating energy expenditure during exercise, enabling trainers and fitness professionals to estimate the caloric burn based on oxygen uptake, which is often measured during various fitness assessments.

The other values, such as 20 kcal, 100 kcal, and 3,500 kcal, are not reflective of the widely accepted conversion factor between oxygen consumption and caloric expenditure during aerobic metabolism, making them less relevant in this context.