An A-grade workout: 40 minutes, 16 hard

LONGEVITY LATEST ISSUE 35 · 4 NOVEMBER 2026

LONGEVITY LATEST

The Evidence-Based Edge on Living Longer and Better

Issue 35 · The Fitness Number · 4 November 2026

Welcome

Five times. In a Cleveland Clinic study of 122,007 adults who did a treadmill test, the least fit quarter were about five times as likely to die during follow-up as the fittest 2–3%, after adjusting for age and illness. The gap between below-average and above-average fitness was about as large as the gap between smokers and non-smokers. It’s an association, not proof. But the number behind it is one you can move.

That number is VO2 max: the most oxygen your body can take in and use at full effort. This week I graded six ways to raise it. The plan I’d build from them sits straight under the grades.

Mandsager et al. JAMA Netw Open (2018)

SPOTLIGHT

Six ways to raise VO2 max, graded

My reading: every top grade goes to a way of training. Neither product added anything to VO2 max beyond the training itself in the trials I found.

Helgerud et al. Med Sci Sports Exerc (2007) · Poon et al. J Sports Sci (2021) · Metcalfe et al. Eur J Appl Physiol (2012) · Cuddy et al. Int J Environ Res Public Health (2019) · Smart et al. Age Ageing (2022) · Porcari et al. J Sports Sci Med (2016) · Cardinale et al. Front Physiol (2019)

BIOHACKING CORNER · THE PLAN LIVES HERE

This is my adaptation, not a tested programme. It takes the session from the Norwegian interval trials and the weekly mix from the maintenance year of a two-year Dallas trial in sedentary 53-year-olds (the full story is in the companion). The Norwegian trial ran three interval sessions a week; one is a starting dose, so don’t expect its 7% from one.

Once a week: the 4×4. Warm up for 10 minutes, then four rounds of four minutes hard and three minutes easy. Aim to reach 90–95% of maximum heart rate by the end of each hard spell, the trial’s target. That’s 16 hard minutes inside roughly 40, including a short cool-down. Uphill walking, a bike or a rower all work. For a rough maximum, take 208 minus 0.7 × your age (about 173 at 50); yours may be 10 beats either side.

Two or three times a week: easy. 30–60 minutes at a pace you can talk through: Zone 2, if you like the name.

Twice a week: lift. Last week’s six-machine routine stays.

Measuring it. A lab test with gas analysis is the most accurate option. Two Dublin studies (2025, and the Series 10 in 2026) found the Apple Watch read about 6 ml/kg/min below lab values on average, with a typical error of about 13%. Whether repeated watch readings reliably pick up a real training gain hasn’t yet been tested independently.

If you have heart disease, chest pain, breathlessness out of proportion to effort or several risk factors, see your GP before the hard sessions.

Howden et al. Circulation (2018) · Tanaka et al. J Am Coll Cardiol (2001) · Lambe et al. PLOS ONE (2025) · Lambe et al. Mayo Clin Proc Digit Health (2026)

THIS WEEK’S ANALYSIS

Top 3 Interventions Under the Microscope

Fitness grades judge one thing: how consistently randomised trials show an option raising measured VO2 max. They are not verdicts on lifespan, convenience or value for money. A = consistent trials; B = positive but few, small, short or limited to certain groups; C = mixed; D = mostly lab data; F = claims far outrun the data.

1. Norwegian 4×4 intervals | Grade A

The benchmark. Sixteen hard minutes, in four blocks.

The result. Beyond the 7.2% in the table, Jan Helgerud’s 2007 trial found the 4×4 group had the biggest rise in stroke volume, the blood pumped per beat. A 2019 meta-analysis of 53 trials favoured the same shape: intervals of two minutes or more, with at least 15 minutes of hard work per session. In 2023 the same team found a 7.3% gain with the 4×4 in women.

The catch. Most trials ran for weeks, not years. Generation 100 ran intervals twice a week for five years in 1,567 Norwegians aged 70 to 77 and recorded fewer deaths than with moderate training (3.0% against 5.9%), but not significantly so.

Wen et al. J Sci Med Sport (2019) · Helgerud et al. Scand J Med Sci Sports (2023) · Stensvold et al. BMJ (2020)

2. Steady “Zone 2” cardio | Grade A

Good at its job. Not shown to be the best one.

The result. Steady training reliably raises VO2 max. In a 2023 meta-analysis in women, continuous training and intervals both added about 3.2 ml/kg/min. In middle-aged and older adults, a 2021 review of 14 trials (429 people) found intervals added 1.1 ml/kg/min more.

The catch. Whether it’s the optimal intensity is a separate question. In 2025, Kristi Storoschuk, Martin Gibala and colleagues found few trials that actually prescribed Zone 2, and no evidence that it beats other intensities for mitochondria or fitness in the general population. Much of the case is borrowed from elite endurance athletes. The A reflects the first finding; the second hasn’t been shown.

Lindner et al. Int J Sports Med (2023) · Storoschuk et al. Sports Med (2025)

3. Two 20-second sprints (REHIT) | Grade B

The minimum dose. Promising in the unfit; barely tested anywhere else.

The result. In 2012, Richard Metcalfe and Niels Vollaard put 29 sedentary young adults on 10-minute bike sessions three times a week for six weeks, each with two all-out sprints built up to 20 seconds. VO2 peak rose 15% in the men and 12% in the women. In a 2019 trial of 32 inactive adults, eight weeks of the protocol on a commercial sprint bike raised fitness on a graded bike test by 12.3%, against 6.9% for 30 minutes of moderate exercise five days a week. Sort of annoyingly good for 40 seconds of real effort.

The catch. Small, short trials, mostly in unfit volunteers; the 2019 study was funded by the American Council on Exercise. The nearest test in trained people, the 2023 Norwegian trial in women, used different formats (eight 20-second or ten 30-second runs) and found no VO2 max gain. Not REHIT, but a warning that results in the unfit may not carry over. I wanted to give this an A on efficiency. I can’t: these are pilot-sized trials.

THIS WEEK’S DEEP DIVE

The Shrinking Engine

A Dallas team took sedentary 53-year-olds and trained them for two years. Their VO2 max rose 18%, and catheter measurements showed their hearts had become less stiff.

The companion sets out what that trial shows, what it can’t, and what it means if you’re starting in middle age.

Read the companion: The Shrinking Engine →

HYPE CHECK

“Breathe pure oxygen, age slower”

The claim. Exercise with oxygen therapy, or EWOT: breathe concentrated oxygen from a reservoir bag while you cycle or walk for 10–15 minutes. It’s sold for energy, circulation and, increasingly, ageing. In 2023, 10X Health co-founder Gary Brecka promoted it on a podcast, saying Otto Warburg won two Nobel prizes for the method and cured 200 diseases with it. A fact check at the time found his company’s system listed at $4,995.

The evidence. Warburg won one Nobel, in 1931, for work on a respiratory enzyme. In a double-blind Swedish trial, 23 trained cyclists did six weeks of hard intervals breathing either 30% oxygen or ordinary air. VO2 max changed by 1.1% against 0.0%, not a significant difference. (One author co-founded a company making oxygen-delivery devices.) A 2017 meta-analysis found extra oxygen helps athletes work harder in the moment; one of its authors told fact-checkers it does little for the average person beyond the exercise itself.

I found no randomised trial of EWOT on any ageing outcome in healthy adults.

Why it misleads. It borrows from three real things: prescribed oxygen for lung disease, a small performance effect in athletes, and a famous name. None of them is evidence about ageing, and the one fitness trial suggests the exercise, not the oxygen, does the work.

Our verdict. Avoid for ageing. If you want to spend something, a chest-strap heart-rate monitor (about £60–95) will help you hit the 4×4 target.

Lead Stories. EWOT fact check (2023) · Cardinale et al. Front Physiol (2019) · Mallette et al. Sports Med (2017) · Decathlon UK. Polar H10 listing (2026)

IN BRIEF

Your fitness trend matters, not just your level. An August UK Biobank analysis followed 11,530 adults whose fitness was estimated twice, about four years apart, with a submaximal bike test. Over a median of 14 years, each improvement of 1 ml/kg/min per year between the two tests was linked to 15% lower risk of cardiovascular disease and 34% lower risk of dying from it; falling fitness tracked higher risk. Observational, with estimated fitness, but it’s about change, not a single snapshot.

López-Bueno et al. Eur J Prev Cardiol (2026)

CLOSING

Raise the ceiling

Your VO2 max will probably drift down with age whatever you do. Training raises the level it drifts from, and in the trials, hard intervals did that in the least time. Next week: creatine, the cheapest supplement with real trials behind it, and whether its brain claims hold up after 40.

Stay curious and stay healthy!
Christian Thomsen, Editor

Longevity Latest is published weekly by FrontWave Media Ltd. Educational content, not personal medical advice. Hard and all-out exercise load the heart: if you have heart disease, chest pain, unexplained breathlessness or dizziness, or several risk factors, see your GP first. Supplemental oxygen is a prescribed treatment.

Reading notes

Evidence checked through 31 October 2026. Cleveland Clinic hazard ratios: 5.04 for the lowest fitness quarter against the top 2.3%; 1.41 for below- against above-average, matching smoking. Generation 100’s interval-versus-moderate comparison was exploratory (HR 0.51, 95% CI 0.25–1.02). UK Biobank figures are annualised changes from submaximal tests; both Apple Watch studies were cross-sectional. The EWOT price is the 2023 listing cited by Lead Stories. Monitor prices: UK retail, October 2026.