Final answer:
Oxygen consumption is the variable that can be measured in L/min or mL/kg/min and expressed in METs, reflecting a person's metabolic rate.
Step-by-step explanation:
The quantity that can be expressed in absolute terms (L/min) or relative terms (mL/kg/min), as well as in METs units is oxygen consumption. Oxygen consumption measures the amount of oxygen the body utilizes per minute and is an important indicator of a person's metabolic rate. During different activities or exercises, oxygen consumption increases and can be measured to assess the energy expenditure and athletic performance. It directly correlates with metabolic activities such as the heart pumping blood, where the resting adult heart pumps blood at a rate of about 5.00 liters per minute (L/min).
Oxygen consumption is also related to Basal Metabolic Rate (BMR), which reflects the energy the body needs at rest to maintain vital functions like heart rate and respiration. It is quantified in the Basal Metabolic Rate, which is essentially the energy expenditure at rest and can be expressed in terms of oxygen used or METs, which stands for Metabolic Equivalent of Task, a unit expressing the energy cost of physical activities as multiples of BMR.