Phily Bowden’s VO2 Max and Lactate Tests Reveal Exactly How Much Fitness She Lost

She was on the verge of the best race of her life — and then everything fell apart.

Elite marathon runner Phily Bowden recently stepped into a sports performance lab for a series of grueling physiological tests, nearly six months after a devastating injury derailed what could have been a career-defining run at the Chicago Marathon.

The results were equal parts surprising, encouraging, and brutally honest — and they paint a fascinating picture of just how resilient the human body can be.

Here’s everything that happened when the data finally caught up with her comeback.

From the Cusp of Greatness to Three Months of Nothing

Last September, Bowden was deep into one of the most productive training blocks of her career, building toward Chicago with mileage consistently hitting between 100 and 120 miles per week.

Then injury struck — and it took everything with it.

Three full months of zero training followed. No running. No cross-training. Just rehabilitation, frustration, and the slow crawl back to gym work before eventually returning to conservative running in late January.

Her coach believed she had been in 2:23 marathon shape before the setback. For context, Bowden had previously run a 2:25 in Berlin — so that projection wasn’t wishful thinking. It was entirely realistic.

There’s a very real feeling of having lost something in that performance and that fitness that we are never guaranteed to get back.

At the time of testing, she had rebuilt to around 60 to 70 miles per week — solid progress, but still well below her typical 80 to 90 mile baseline outside of a marathon block.

What the Tests Actually Measured — and Why It Matters

The lab session covered three distinct diagnostics, each measuring a different dimension of athletic performance.

• Lactate Threshold Testing (LT1 & LT2): Progressive treadmill running with blood samples taken at each stage to identify the points where the body begins struggling to clear lactate from the muscles.
• Running Economy: A measure of oxygen cost per kilometer — essentially how fuel-efficient the body is at various speeds.
• VO2 Max: The maximum rate at which the body can take in, transport, and use oxygen — the ceiling of the aerobic engine.

Sports scientist George, who administered the tests, described the session plainly.

The whole process today is just kind of giving us a few diagnostics as to what’s going on. We’re looking at her engine in the max test — miles per gallon in the economy test — and then working out what paces she starts to find things difficult.

The VO2 Max Result Nobody Saw Coming

Before revealing the number, some context: an average untrained woman typically scores between 35 and 40. Recreational runners sit around 45 to 55. Elite female distance runners generally land in the 60 to 70 range.

Bowden’s last recorded VO2 max — back in 2023 — was 68.

After three months of zero activity and a slow, cautious return to training? She came in at 65.2 ml/kg/min.

That still places her firmly in elite territory, despite research suggesting VO2 max can drop by 10 to 15% after just two months of inactivity. The drop was real — but far smaller than feared.

The fact that it is still in the elite range is genuinely very encouraging.

Running Economy: Years of Miles Don’t Just Disappear

Perhaps the most quietly impressive result of the day came from her economy scores.

Across every tested speed, Bowden’s oxygen cost remained remarkably consistent — hovering between 181 and 188 ml/kg/km, well below the 200 mark that signals high efficiency. Lower numbers mean less fuel burned to maintain any given pace.

Months away from structured training hadn’t stripped away the mechanical efficiency built across years of high mileage. It was largely intact.

Even after months off, the mechanical efficiency that I have built up over years of training is largely still there.

The fuel-source data added another useful layer. At easy paces, her body was burning roughly half fat and half carbohydrates. By the time she reached 19 km/h — approximately 5:05 per mile pace — she had switched almost entirely to carbohydrate burning. That crossover point matters enormously for marathon strategy, directly influencing how hard she can push before depleting glycogen reserves and risking the dreaded wall.

Where the Real Work Lies: The Threshold Gap

Here’s where the results get genuinely fascinating — and where Bowden’s path forward becomes crystal clear.

Her LT2 currently sits at 83% of her VO2 max. Her LT1 is at 72%. In well-trained endurance athletes, LT2 can be pushed all the way to 90% of VO2 max through targeted training.

That gap — from 83% to 88 or 90% — is where marathon performance lives.

If I can train my LT2 up from 83% to 88 or 90% of my VO2 max, the pace at which those thresholds sit gets faster without my VO2 max needing to change at all.

Pacemaker and sports physiologist Dan — the man who helped guide her through her 2:25 Berlin finish — confirmed the direction of travel. The engine is there. It’s about learning to run closer to its ceiling for longer.

The Takeaway That Changed Everything

Walking out of the lab, Bowden’s headline numbers told a story far more optimistic than she’d dared to expect.

VO2 max: Held up at 65.2 — still elite. Running economy: Essentially unchanged, with years of training preserved at the cellular level. Thresholds: The focus area, with clear room to build and meaningful gains on the horizon.

It didn’t just show me where I am. It showed me how I need to get to where I need to be — exactly what I need to work on. And there’s something really freeing about that.

The injury that threatened to erase a career-best performance didn’t take as much as she feared. And with a clear training roadmap now in hand — built entirely around pushing those lactate thresholds higher — the comeback isn’t just possible.

It might be setting her up for something even better than Chicago ever could have been.