Interval training at vVO2max: effects on aerobic performance and overtraining markers
Participants
n=8 highly trained runners (VO2max 71.6±4.8 mL/kg/min at baseline).
Protocol
The same eight runners did two consecutive phases (not parallel groups):
Normal Training (NT), 4 weeks: 1 session/week at vVO2max — 5 reps at 50% of time limit (Tlim) at vVO2max, equal-duration recovery at 60% vVO2max.
Overload Training (OT), next 4 weeks: 3 such sessions/week.
Key Findings
After NT (1×/week): vVO2max 20.5 → 21.1 km/h (p=0.02), via better running economy (50.6 → 47.5 mL/kg/min at submaximal speed, p=0.02); VO2max, time to exhaustion at vVO2max, distance run at vVO2max and lactate threshold unchanged; HR at 14 km/h fell 162 → 155 bpm.
After OT (3×/week): neither performance nor its determinants changed. Submaximal HR at 14 km/h fell further (155 → 150 bpm); resting noradrenaline unchanged (2.6 vs 2.4 nmol/L), but noradrenaline at the end of the vVO2max test rose 11.1 → 26.0 nmol/L (p=0.002).
Critical Conclusion
Adding two more vVO2max sessions a week for four weeks, on top of the first phase, bought no further aerobic gain and raised exercise noradrenaline. One session a week produced a gain. The study says nothing about two a week, and because the phases were sequential, "3×/week" is also "the second month".
Practical Application
In 8 highly trained runners (VO2max ~72), four weeks of one vVO2max session a week raised vVO2max from 20.5 to 21.1 km/h through better economy; the following four weeks at three sessions a week changed no performance variable and raised end-of-test noradrenaline (11.1 → 26.0 nmol/L) — tripling vVO2max sessions gave nothing extra here; two a week was never tested.
Use it as ceiling evidence, which is what it is. Three quality VO2max sessions a week gave nothing extra in this cohort. A plan that caps at two is following coaching convention, and should say so (SYNTH-33).
Limitations
n=8, no control group, 1999, running only. The two frequencies were tested in sequence in the same people, so order and accumulated training are confounded with frequency; it never tested two sessions a week.
"Overtraining markers" means a rise in exercise noradrenaline; resting noradrenaline and maximal HR did not change, so this is not a demonstration of overtraining syndrome.
Outcomes are laboratory aerobic markers over weeks, not season-long performance or injury.
Running only: the mechanical cost of a vVO2max session is not comparable to the same physiological dose on a bike.
Widely over-cited as the source of a rule it does not contain. The base's own plan checker was rewritten to stop repeating a 'never more than two VO2max sessions a week' claim traced back here — read this entry for what was measured, not for that rule.
How this entry was checked and changed
Why this level
regraded 2026-09-26 from A: uncontrolled pre-post, n=8
Content correction 2026-09-27
"n=8 recreational runners" and Tier 2 -> highly trained runners (VO2max ~72), Tier 3.
Design implied two parallel arms -> the same eight runners did 1×/week then 3×/week in consecutive 4-week phases; no control group.
"3×/week: overtraining" -> no change in performance or its determinants; end-of-test noradrenaline rose 11.1 → 26.0 nmol/L while resting noradrenaline was unchanged. Economy, HR and noradrenaline numbers added from the abstract.