What limits exercise during high-intensity aerobic exercise?

Excerpt

An important and unresolved issue is the mechanism(s) that lead to task failure during intense aerobic exercise. Marcora and Staiano (2010) have recently reinvestigated this problem using human subjects on a bicycle ergometer. Subjects were asked to exercise at 80% of their maximal aerobic power (242 W) and failed (unable to maintain the pedal frequency above 60 min⁻¹ despite encouragement) after 10.5 min. Under control conditions, their peak power output measured over 5 s and at a pedal frequency of 137 min⁻¹ was 1,075 W. When peak power was measured as soon as possible after the fatiguing event, it was 731 W. Because peak power (731 W) was so much greater than the power which the subjects failed to achieve at the end of the exercise period (242 W) Marcora and Staiano argue that muscle performance was not the main problem, instead the subjects stopped because their ‘perception of effort’ was greater than they were prepared to tolerate. …