Respiratory exchange ratio (RER) vs time.
This plot usually starts at approx. 0.8 and increases to values higher than 1.0 above AT. Inability or failure to produce an exercise lactic acidosis would mitigate an increase in R to values above 1.0, except when accompanied by acute hyperventilation (decreased PaCO2).

Question: Is there a defect in muscle utilization of O2 or substract? (panel 3,5,8)

Example of disorder: Muscle glycolytic or mitochondrial enzyme defect

Markers of abnormality: AT, R, VCO2, HR vs VO2, lactate, lactate/pyruvate ratio