Does a fixed % of VO2max put a heavy session in the right domain?

Meyler and colleagues (University of Hertfordshire) asked whether prescribing exercise from physiological thresholds gives a more uniform stimulus than prescribing it from VO2max.

Ten adults did three visits of testing, then bouts in random order of prescription method: moderate (30 min at 90% of gas exchange threshold, GET, vs 55% of VO2max), heavy (20 min at GET + 50% of the gap to critical power, CP, vs 75% of VO2max) and HIIT (5 × 3 min at 110% of CP vs 85% of VO2max). All completed both moderate bouts.

In the heavy bout, the %VO2max prescription averaged 113 ± 13% of CP and 3 of 10 finished; the threshold prescription averaged 83 ± 6% of CP and 10 of 10 finished. The three who finished at 75% of VO2max were at 96-100% of CP; the seven who did not were at 101-132%. Average lactate was 8.06 vs 4.12 mmol/L. HIIT completion was 2 of 10 vs 10 of 10.

Variability in peak and average lactate and in W′ depletion was lower with thresholds for HIIT. Our reading: the clearest acute demonstration in the base that a percentage of a maximum can put one person in the heavy domain and another in the severe domain on the same prescription, in line with REF-038 (B+) and REF-1230 (A-).

It is the mechanism behind treating any percentage target as a starting guess. But the percentage tested is of VO2max in low-fit adults; nothing here measures %FTP.