Connecting oxygen uptake to usable power—so you can race smarter, not just harder.
A tale of two 10Ks
Two runners line up with identical lab reports:
VO₂ Max = 70 ml/kg/min.
Gun goes. By 6 km, Runner A glides; Runner B is treading water.
Same ceiling… wildly different race.
What happened?
Because performance isn’t “VO₂ Max, therefore victory.” It’s Ceiling × Usable Fraction × Cost:
Ceiling = VO₂ Max (how much O₂ you can utilize)
Usable fraction = how close you can operate to that ceiling for long stretches (lactate/ventilatory threshold; what we call Redline Ratio)
Cost = how much O₂ it takes you to produce a given speed or power (economy/efficiency)
Multiply those three and you get your sustainable speed or power. Change any one, and the outcome changes—even when the ceiling is the same. That’s why Runner A pulls away. And it’s why the best coaches obsess over all three levers, not just VO₂ Max.
From oxygen to output (the 30‑second physiology)
VO₂ Max is the rate limit on the whole chain: lungs → heart → blood → mitochondria. The closer you race to that limit, the more ATP you churn per minute. But translating “big oxygen” into “big watts” depends on peripheral machinery (capillaries, mitochondrial enzymes) and how economically your muscles turn ATP into motion.
That’s why two identical VO₂ Max values can produce different finishing times—VO₂ Max is necessary, rarely sufficient.¹–³
Where experts agree (and argue)
Agreement: VO₂ Max, threshold (fractional utilization), and economy together explain most differences among trained endurance athletes.¹–³
Debate: Which matters most on race day? In marathons/half‑marathons and long time trials, threshold/economy often separate winners when ceilings are similar. In shorter events (1500 m, prologue TTs), a VO₂ Max edge can be decisive.¹,³–⁵
Working rule: the longer the event, the more threshold & economy decide; the shorter the event, the more raw ceiling shows.
Three levers, one race
1) Ceiling — VO₂ Max
Think of VO₂ Max as your oxygen “budget.” Bigger budget, bigger potential ATP throughput. Central factors (stroke volume, hemoglobin) and peripheral factors (mitochondrial oxidative capacity) set it. Long intervals (3–5 min), high‑volume aerobic work, and years of consistent training raise it.¹,²,⁴
2) Usable fraction — Redline Ratio (threshold)
This is how close to VO₂ Max you can sit without imploding. It reflects lactate/ventilatory thresholds (VT2). Elites may hold ~85–90% of VO₂ Max for long stretches; recreational athletes more like ~70–80%. Pushing VT2 higher—via tempo/threshold work and smart volume—lets you “live near the ceiling” longer.¹–³
DexaFit tie‑in: Your lab test quantifies the ceiling (VO₂ Max) and the breakpoints (VT1, VT2). From these we derive Redline Ratio = VO₂@VT2 ÷ VO₂ Max × 100—your practical “how much of the engine can I actually use?” map.
3) Cost — Economy/Efficiency
Economy is the oxygen cost of a given output (e.g., ml O₂·kg⁻¹·km⁻¹ for running, ml O₂·W⁻¹ for cycling). Two athletes at the same threshold and VO₂ Max can still differ if one spends less O₂ per unit speed/power. Economy emerges from biomechanics (stiffness, stride mechanics), recruitment patterns, and years of highly specific practice.³,⁵–⁷
We don’t hand you an “economy score” in a single DexaFit session. You infer it over time: if speed/power at a given fraction of VO₂ Max rises while VO₂ Max and Redline Ratio stay similar, your economy improved.
Case snapshots (where the win really came from)
Marathoners: Historical modeling shows world‑class results occur when a high VO₂ Max is paired with an exceptional threshold and economy; the latter often separate champions with similar ceilings.⁴,⁵
Cyclists: Among pros with alike VO₂ Max, sustainable power hinges on fractional utilization (functional threshold) and pedaling efficiency; maturation can improve efficiency without raising VO₂ Max.²,⁶
Rowers: Whole‑body demand makes VO₂ Max crucial, but boat speed is brutally sensitive to technical economy—blade work, timing, and posture.
Swimmers: Even with big engines, breathing constraints and technique (drag) make economy king; small mechanical gains trump small VO₂ gains.
Two athletes, one ceiling—different math
Both athletes: VO₂ Max 70.
Athlete A: Redline Ratio 90%; great economy → holds ~63 ml/kg/min equivalent for a long time at a lower O₂ cost → fast.
Athlete B: Redline Ratio 78%; mediocre economy → holds ~55 ml/kg/min equivalent and “spends” more O₂ per unit speed → fades.
Same ceiling, different throughput. The race was decided below VO₂ Max.
How to train the trio (without burning yourself down)
Raise the ceiling (VO₂ Max): 1–2 Zone‑4 sessions/week (3–5‑min reps, 1:1 rest), atop a robust Zone‑2 base.¹,²
Nudge the fraction (threshold): 1–2 Zone‑3 sessions/week (e.g., 2×20′, 3×12′) to push VT2 toward the ceiling.²,³
Lower the cost (economy): Frequent sport‑specific practice at race‑relevant speeds/powers; light drills that improve stiffness, timing, and technique; small, sustainable strength work to improve coordination—not bodybuilding mass.³,⁵–⁷
Guardrails: If VO₂ Max is low, build the base first. Chasing threshold/economy without oxygen supply is false economy.
When the ceiling decides vs. when the floor and cost decide
Ceiling matters most when…
The event is short (≤4–6 min), selections are brutal (national team time trials), or altitude reduces everyone’s absolute speed—raw O₂ delivery becomes the filter.¹–³
Threshold/economy matter most when…
The event is long (≥30–60 min) and steady; small improvements in usable fraction and cost compound into minutes on the clock.³–⁵
What your DexaFit test gives you (and what it doesn’t)
Gives: VO₂ Max (ceiling), VT1 & VT2 (to compute Redline Ratio), HR/RER/ventilation to target Zones 2–4 with precision.
Doesn’t (directly) give: A single “economy score.” You track economy by watching speed or power at a given fraction of your VO₂ Max climb over months of specific training.
Big picture: Lab numbers set the plan; field performance validates it. Top coaches marry both.
The mortality footnote (why this matters beyond medals)
Outside the arena, higher cardiorespiratory fitness independently predicts lower all‑cause mortality, with ~13–15% risk reduction per +1 MET and ~70–80% lower risk for the fittest vs. least fit cohorts.
Improving VO₂ Max raises the ceiling for life; improving threshold and economy raises how well you live near it.⁸–¹⁰
One line to remember
Ceiling sets potential. Fraction and cost determine reality. Train all three—intelligently, in your sport—and the math will start breaking your way.
References
Bassett DR Jr, Howley ET. Limiting factors for maximum oxygen uptake and determinants of endurance performance. Med Sci Sports Exerc. 2000;32(1):70–84.
Coyle EF. Integration of the physiological factors determining endurance performance ability. Exerc Sport Sci Rev. 1995;23:25–63.
Jones AM, Carter H. The effect of endurance training on parameters of aerobic fitness. Sports Med. 2000;29(6):373–86.
Joyner MJ. Modeling: A VO₂ max, lactate threshold, and running economy approach to the marathon. J Appl Physiol. 1991;70(2):683–687.
Joyner MJ, Coyle EF. Endurance exercise performance: the physiology of champions. J Physiol. 2008;586(1):35–44.
Coyle EF. Improved muscular efficiency displayed as Tour de France champion matures. J Appl Physiol. 2005;98:2191–2196.
Saunders PU, Pyne DB, Telford RD, Hawley JA. Factors affecting running economy in trained distance runners. Sports Med. 2004;34(7):465–485.
Kodama S, et al. Cardiorespiratory fitness as a quantitative predictor of all‑cause mortality and cardiovascular events. JAMA. 2009;301(19):2024–2035.
Kokkinos P, et al. Cardiorespiratory fitness and mortality risk across the spectra of age, race, and sex. J Am Coll Cardiol. 2022;80(6):598–609.
Mandsager K, et al. Association of cardiorespiratory fitness with long‑term mortality. JAMA Netw Open. 2018;1(6):e183605.
