A young woman distance runner has recently not been performing well and has complained of feeling lethargic and sluggish. You perform a graded exercise test to VO2max including blood samples to attempt to determine possible cause. a. VO2max is significantly lower than measured last year. b. R value never reached above 1.0 during the exercise test. c. The athletes self-reported diet is poor as far as nutrients and total kcals. d. Blood lactate profile showed an early onset of a lactate threshold. e. Anaerobic test (Wingatge cycle test) was not different that when this athlete was tested last year. d. You suspect the athlete may be anemic, yet you can only test blood hemoglobin levels and they are normal. Nevertheless, your team MD prescribes iron for this athlete. Her VO2max does improve a little, yet endurance time on the treadmill remains poor. Questions: What could be the possible physiological cause of the athlete's poor performance? If you would have unlimited budget and lab testing facilities, what additional tests would you wish to perform to find a possible cause.