Emergency Capacity
You’re unlikely to be thinking about your VO₂max when you’re fresh and everything’s calm (or if at all…).
You will however think about it when you’re late for a train at Cardiff Central, the stairs are three flights high, you’ve got a suitcase in one hand, a coffee in the other, end up sprinting to the top of the stairs, and are now seeing stars with only a second or two to spare.
That’s when your ceiling for fitness is honest. That’s your emergency capacity.
We tend to reference this type of demand through various different terms: fitness, conditioning, cardio, etc… However the technical term is VO₂max — your maximum rate of oxygen usage per minute. You don’t need to love physiology to appreciate it, and the intention is to not dig into the details in this insight.
However, you just need to know this: individuals with a higher cardiorespiratory fitness tend to live longer and face fewer cardiovascular events, even after you adjust for age and other risk factors (Kodama, 2009).
However, average VO₂max tends to lead to average health and fitness-related outcomes. Especially in a population in which the “average” is increasingly seeing a decline in these types of metrics. And Id like to belive that if you’ve chosen to read and subscribe to this page, it’s not average returns you’re after for putting this considered effort into your health, fitness, nutrition, and general wellbeing.
From the outset, our immediate goal therefore is to aim for each of us to be ≥75th percentile for your age and sex. Not elite. Just not average. That’s the emergency capacity that makes climbing the stairs with a suitcase and a few minutes to spare, something manageable rather than a cardiovascular event in the making.
Creating the Ceiling: Intervals You’ll Actually Do
There isn’t necessarily one sacred protocol to choose here. However, there are a few good doors to choose between. This will likely be dependent on your training experience, time availability, and modality choice.
However, here’s a few guidelines to consider:
Option A: 4x4 minutes Hard (commonly referred to as Norwegian 4x4)
Intensity: around 90-95% of HRMax by the END of each rep.
Recovery: 2-4 minutes easy between
Why: Repeatedly pushing up against your limit is a proven way to nudge VO₂max in an upward trajectory (Helgerud, 2007)
Feels like: You can’t chat. You’re honest-breathing. You need the full recovery time between rounds.
Option B: Tabata 8x20:10 (Advanced)
Eight rounds: 20 seconds max effort, 10 seconds easy.
Total: 4 minutes, that when done correctly, are soul-destroying…
Why: The classic Tabata protocol can improve both aerobic and anaerobic capacity in trained people (Tabata, 1996).
Caveat: It’s not for beginners. Mostly because the effort has to be so high with each interval. Warm-up properly beforehand. Pick a cyclical modality (eg., Bike, Rower, or Assault Bike)
Option C: Assault Bike - All Out Test (Use sparingly…)
An old-school 1-2 mile Challenge (1.6-3.2km) at best recorded effort. Warm-up before. Leave nothing in the tank.
Essentially a time-trial over either 1 or 2 miles depending on your finish time. Aiming to replicate the 3-4 minute max effort type approaches of Option A and B, but with a recordable time-metric we can use for reference.
Use sparingly — as a test, not a weekly plan. It sharpens intent, gives you a conditioning reality check, and shows you how your ceiling converts into real work with actual time/distance parameters.
Pick one primary option for your “ceiling session” most weeks. Also considering rotating between to stave off the boredom and psychological staleness that may arise.
The Base That Makes It Work: Zone 2 (Done Like A Grown-Up)
If we consider intervals as those that push up the ceiling, Zone 2 is the base that supports it. Our cardiorespiratory foundation.
For a quick definition in plain English: we can consider Zone 2 as a steady effort where you can nose-breathe and talk in full sentences. That ends up round 70-75% Max Heart Rate in untrained individuals, and likely closer to 78-80% MaxHR in trained individuals. Inside a lab environment, we’d see a lactate accumulation in the blood below 2 mmol·L⁻¹, but you don’t need a lab to get the idea.
The recommendation for Zone 2 training by individuals such as Inigo San Milan, Peter Attia and Andrew Huberman aims for upwards of 180mins per week. We will touch on why this is a bit later. But for many individuals, that’s going to be a very big ask. That’s also before factoring in any other training type we may want to include…
However, here’s the catch we apply when working with clients: we’re not asking you to jump straight up to ~180+ minutes per week. Most individuals won’t make that stick while working, parenting, and actually living “normal” lives. We go in stages:
60 minutes/week (2x30min ideally…)
90 minutes/week (2x45min or 3x30min)
120 minutes/week
150 minutes/week
180+ minutes/week
The aim being to hold each stage for a fortnight. Let your joints, schedule and patience in training this way, adapt.
You’ll get much further by progressing this way, than trying to be perfect for the first week then falling off a cliff edge. You’ll also naturally find a stage in which you may have to accept is the boundary to what you can allot to this type of training, at this moment in time (not to say this is static…).
And also remember to account for real life. If your daily step count is consistently high, for demonstration purposes let’s say >15,000 per day, because you walk to work, do the school run, move between meetings, and so on. That’s often going to contribute directly to your Zone 1/2 work when added up. It’s all acting as the base to the cardiovascular pyramid you’re aiming to build. Don’t dismiss it. Log it, value it, and build on it.
In terms of modality, the choice becomes the one your most likely to keep long-term:
Brisk outdoor walks (rucking, hills, parks, real life etc…)
Bike (Road, Turbo, Wattbike, Assault)
Rower or Ski Erg
Treadmill walk with an incline (for most individuals lower in cardiorespiratory fitness, or efficiency/economy, running is likely to push you beyond the Z2 threshold and into Z3/4/5).
Swim, if your joints prefer the water.
The theory as to which modality would work best means absolutely nothing if you hate it…
From a personal perspective, I’m very much a seasonal runner. However I can sit on an Assault Bike at 140-150bpm for 45-60mins. 3x per week. Podcast on. No problem…
That’s probably describing most individuals personal hell I’m sure, but the premise is, choose what you’d still be able to do on a drizzly Thursday in November.
Why “~180 minutes” of Zone 2?
Three reasons, none of which are overly glamorous but they’re important to consider:
It sits inside the evidence range that we have available. Both the UK Chief Medical Officers and the World Health Organisation (WHO) recommend 150-300 minutes/week of moderate-intensity aerobic activity for adults. Zone 2 is therefore simply the steady, conversation end of that range. ~180 minutes is going to be a practical midpoint that most working adults can build towards in time (eg., 3x60, 4x45, 6x30).
Does-response without (too much…) misery: You get meaningful cardio-metabolic gains (lower blood pressure, greater insulin sensitivity, higher recovery) at the moderate end, and it complements the high-intensity ceiling work instead of competing against it.
It’s programmable in real life: You can stage up incredibly simply (60 → 90 → 120 → 150 → 180 min/week), count brisk steps/commutes as part of your base, and choose a modality you’ll actually stick to. That’s how everyday individuals make it stick — not by leaping from 0 to 3 hours overnight.
“How on earth do I fit this in with… life?”
If you took all the recommendations made within the health, fitness, and longevity space regarding cardiovascular fitness, you’re probably thinking: “Three hours of Zone 2, “ceiling pushing” intervals, plus resistance training — and a job, a family, kids… are you taking the ****?”.
So let’s look at how this could work in reality for context.
A Working-Week Template (Example)
Mon - 30-40min Zone 2 (commute walk, treadmill incline, or bike)
Tue - Resistance Training (Full-Body, 45-60min)
Wed - Ceiling Session (4x4 or Tabata + 10min easy cool-down)
Thu - 30-40min Zone 2 (stack with errands/work calls/emails/TV/Podcasts)
Fri - Resistance Training (Full-Body, 45-60min)
Sat - 30-60min Zone 2 (Family walk, bike ride, Park Run at light jogging pace)
Sun - Off/Light Mobility/Yoga/Play
Whilst there is a big ask here in terms of 6-days per week of exercise activity, that’s three Zone 2 slots (building towards 180 min in stages), one “ceiling session”, and two strengths days. You’re covering most, if not all, of your bases here.
If you’re earlier in the process, do two Zone 2 slots, and hold at 90-120 min/week until it becomes “just what you do.” Then aim to build.
Micro-Stacking Ideas (Hidden Zone 1/2)
Walk the last two stops instead of the bus.
Take 15-min walking breaks between calls.
School run on foot if possible.
Incline Treadmill walk with computer-based errands.
Bike to the shops instead of driving
This type of training isn’t designed to be highlighted on Instagram. You’re building the capacity you’re going to need when life is inconvenient.
Testing Without Turning Life Into a Lab
You don’t need a Gas-Exchange Mask and a lab test every month. You just need simple checkpoints to see if you’re drifting up or down.
Consider one of the following:
Graded Ramp Test on your main modality every 8-12 weeks (record power/speed and HR at the last minute, RPE should reach 9-10)
12-min run test (distance achieved in metres) on a track or flat loop.
Bike/Row/Assault Bike: An all-out 3-4 minute attempt at max effort (pick your recordable metric — eg., distance, average power, calories burned)
Keep the test conditions similar. Note sleep, time of day, hydration status. You're looking to establish trends not heroics.
What does “75th Percentile VO₂max” actually mean?
For reference, and not to get overly bogged-down in the technical, use the link here to head towards Table 3, in which you’ll find treadmill CPET (lab) reference values from the FRIEND registry — sex- and age-specific ml·kg⁻¹·min⁻¹ cut-offs for the 75th(target) and 90th (top 10%) percentiles. It’s a robust dataset that clinicians use. Of course numbers are likely to vary by protocol used and the modality selected (cycle-ergometer numbers tend to track lower), but they provide a solid anchor as to what we’re aiming towards.
The Invisible Caps on Progress
It’s easy to get caught up in the excitement of a “new protocol”. Fewer people want to fix the boring stuff that decides whether a protocol does, or doesn’t, work.
Sleep efficient <85% or WASO >30min? Your intervals will feel like running uphill with a handbrake on. (No idea what these terms are? — check out our last insight here.)
Late Caffeine? Still in your system at 23:00, nudging you awake at 02:30.
Evening Alcohol? Fragmented sleep, blunts recovery, makes tomorrow feel heavy.
Sore joints? Your modality may not be sustainable long-term, try something more cyclical with lighter/no ground contact (eg., Bike/Rower/Swim).
Power Fades First - Keep a Sprinkle In
As we age, we tend to lose power (force x velocity) quicker than strength (force x area). That’s a hugely relevant factor in fall prevention, and feeling generally athletic. It’s also part of the reason why there are very few individuals who we DON’T do some type of jump, rebound, or medicine/slam-ball work with at IFT.
This type of work can take on many forms (including the interval-work mentioned above), but aim to keep those 6-10 second fast efforts in the week: a few short sprints, some stair drives, med-ball throws against a wall, or some slams into the ground. Quality over quantity, full recovery between efforts, 1-2 times per week.
It’s not about turning individuals into sprinters or shot-putters. It’s about keeping the reflexes alive that stop us from going down when our feet slide out from underneath us on a wet tile, or the that keeps a shoulder joint from dislocating when the dog pulls too hard on the lead.
Priority by Decade (To Keep Things Honest)
In your 30’s — Bank as much emergency capacity as you can whilst the going is good. Chase a higher ceiling while joints will forgive you more. Learn good mechanics (especially if your modality is running or swimming) to hold you in good stead for later years.
40’s to 50’s — Aim to maintain your ceiling for as long as you can, the goal is to preserve and offset the natural tendency for year-on-year decline. Protect joints and sleep to prevent you from spinning your wheels without positive outcomes.
Into your 60’s and beyond — Keep frequency as high as recovery will allow you. Tighten up intensity to enable greater recovery (eg., 4x4 becomes 6x2min hard/2 min easy). Spread Zone 2 across most days.
Longevity cares about what you can do and still do — not what you once did.
“What if I want to be more than the 75th Percentile?”
Great! — Just be deliberate…
Top 10% (90th Percentile) in your age band. Use the link provided to the CPET reference (here). This is likely to result in a big overall health “win” regardless of age, and aligns with the continuous, “more is better” gradient seen in mortality data (Mandsager, 2018) — in which they conclude that there is no observed upper limit of benefit to higher cardiorespiratory fitness.
“Top 10%, but a decade younger…” If you’re 50-59, that means chasing down the 40-49 90th percentile numbers (men 52.1, women 38.4). If you can get there, my full respect to you. To reach it, you’ll likely need a combination of the following:
An honest ceiling session most weeks (e.g., 4x4min near-max, or a true8x20:10 Tabata on a joint-friendly modality.
A staged Zone 2 base towards ~180 min/week or above.
Guardrails: sleep efficiency ≥85%, WASO <30 min, caffeine timing, alcohol consumption minimal to non-existent.
Quarterly like-for-like field test (possibly an annual lab-test too?) with the same decide, route, and conditions (both internal and environmental).
Reality and Safety Check: The higher the ambition, the likely slower the progress you’re going to make. This is beyond “beginner gains”. There is much more value to be gained from technique and recovery, and (if you’ve got known risk factors) a GP check-in before you start pushing the intensity/volume buttons.
Bringing It All Together
One weekly “Ceiling Pushing” session (4x4 or Tabata, rotating occasionally, occasional 1-2 mile (1.6-3.2km) all-out Bike/Row/Assault to benchmark).
Zone 2 that climbs 60 → 90 → 120 → 150 → 180 min/week over time, counting steps and daily movement as contributors to this base.
Resistance Train two days per week (minimum) to maintain muscle mass, strength, and joint integrity.
A sprinkle of 6-10 second speed-work for power/reflex maintenance.
If you’re still reading this and thinking “that’s a lot,” to some extent, good — our goal now becomes to prune it back to the minimum you will do this week. Then repeat. Then progress a notch. Then repeat. That’s the whole game.
This Week’s Challenge
Pick your protocol, and do it once.
Either 4x4min near-max (90-95% MaxHR by the end of the 4mins), with 3-4 min easy between, or Tabata 8x20:10 on a Bike/Rower/Assault. Warm-up for 6-10min first (gradually increasing effort), cool down 6-10 mins after (gradually decreasing effort).
Start your Zone 2 ladder.
Choose the run you’re most likely to be able to achieve THIS week: 60, 90, 120, 150, or 180 minutes total. Split into 2-4 sessions. Count steps/commutes. Log it.
Add two 6-10s fast efforts after your easy warm up
Stair drives, 20m sprints, series of med-ball throws. Full recovery between.
Write down one “committed-modality” sentence:
For example my own would be… “My main modality is going to be the Assault Bike. Because it’s home-based, weather-proof, cyclical, and I can easily, and safely, distract myself with Podcasts.”
Bigger Than Fitness
These types of topics aren’t about masochism, or training yourself into burnout. It’s about maintaining dignity and options across the lifespan. VO₂max is not a vanity metric. It’s the ceiling capabilities that decide how heavy normal life is going to feel now, and moving forward.
The goal is to be someone who trains with the intention of being independent and capable later. Not perfect. Not elite. Capable.
AK.