HYROX training is very good for your heart for most healthy adults, because it raises cardiorespiratory fitness, which is one of the strongest predictors of a long, healthy life that doctors have. The honest caveat: that evidence comes from research on fitness and exercise in general, not from studies of HYROX itself. This guide explains what VO2max is, how fitness links to lifespan, how hybrid training raises it, what it does for blood pressure and resting heart rate, how to measure your progress, and when to be careful.
This is general information, not medical advice. If you have a heart, lung or metabolic condition, high blood pressure, are pregnant, or get chest pain, unusual breathlessness, palpitations or dizziness during exercise, talk to your doctor before you start hard training.
What is VO2max, and why does it matter?
VO2max is the most oxygen your body can take in and use per minute during all-out exercise. It's usually written in milliliters of oxygen per kilogram of body weight per minute (ml/kg/min), and it's the standard lab measure of cardiorespiratory fitness, or "CRF."
Despite the "lung" image, VO2max is mostly about your heart. A classic review in Medicine and Science in Sports and Exercise (Bassett and Howley, 2000) concluded that the main limit is how much oxygen your heart and blood can deliver, and that training raises VO2max mainly by increasing how much blood your heart can pump per minute. Your muscles adapt too, growing more mitochondria, and that is what lets you hold a faster pace for longer.
Two related terms you'll see:
- METs. One MET is your resting energy use, about 3.5 ml/kg/min of oxygen. Doctors often report fitness from a treadmill test in METs. A VO2max of 42 ml/kg/min is 12 METs.
- Lactate threshold. The hardest pace you can hold for a long time. It matters more than VO2max for race day, but the two rise together.
VO2max also matters for your HYROX time. In the one lab study of a simulated HYROX race (Brandt and colleagues, 2025, 11 recreational athletes), VO2max was among the strongest predictors of finish time, alongside weekly endurance training.
Does fitness really predict how long you live?
Yes. This is one of the most consistent findings in health research, though it comes from observational studies, which show links rather than proof of cause.
- The American Heart Association published a scientific statement in 2016 arguing that fitness should be treated as a "clinical vital sign." It says low fitness may predict death more strongly than smoking, high blood pressure, high cholesterol or type 2 diabetes.
- A 2024 overview in the British Journal of Sports Medicine (Lang and colleagues) pooled meta-analyses covering 199 cohort studies and more than 20 million observations. People with high fitness had about half the risk of early death of people with low fitness. Each 1-MET step up was linked to an 11% to 17% lower risk of death, and an 18% lower risk of heart failure.
- A study of 750,000 US veterans (Kokkinos, JACC, 2022) found the least fit fifth had about four times the death risk of the fittest. The pattern held for men and women, for every racial group studied, and for people in their 70s and 80s. Being unfit carried more risk than any of the heart risk factors the authors examined.
- A Cleveland Clinic study of 122,000 treadmill tests (Mandsager, JAMA Network Open, 2018) found that being below average versus above average for your age carried about the same extra risk as smoking. It found no point where more fitness stopped helping.
What does "1 MET" look like in real life? A JAMA meta-analysis (Kodama, 2009) described it as roughly the difference of being able to run 1 km/h faster. That's a realistic gain for most beginners.
Does improving your fitness help, or is it just genetics?
Genes play a part, but improving matters. In a study of almost 10,000 men tested twice about five years apart (Blair, JAMA, 1995), those who went from unfit to fit had a 44% lower death rate than men who stayed unfit. Each extra minute they could last on the treadmill was linked to about 8% lower risk. It's still observational, but you're not stuck with the fitness you have.
Does HYROX training improve VO2max?
Almost certainly, though no study has yet measured VO2max before and after a HYROX training block. What we do know is that HYROX training is built from the two methods with the best evidence for raising VO2max: steady endurance running and hard intervals.
- Endurance and intervals both work. A 2015 meta-analysis of 28 studies (Milanović, Sports Medicine) found that continuous endurance training raised VO2max by about 4.9 ml/kg/min, and interval training by about 5.5 ml/kg/min, compared with no exercise. That's roughly 1.5 METs, the size of change linked to meaningfully lower risk in the studies above.
- Hard intervals have an edge. In a well-known trial (Helgerud, 2007), moderately trained men did four sets of 4 minutes at 90% to 95% of max heart rate, with 3 minutes of easy jogging between, three times a week for eight weeks. Their VO2max rose 7.2%, and the amount of blood their heart pumped per beat rose about 10%. Steady running at the same total workload didn't change VO2max significantly in that group.
- The race itself is a cardio test. In the Brandt study, racers spent about 80% of an 86-minute simulated race in the "very hard" heart-rate zone.
Hybrid training adds stations to the mix. Big-muscle stations such as the SkiErg, row and wall balls push your heart rate high, so a session that mixes runs and stations works as an interval session. Heavy sled work is closer to strength training: it's very hard, but it trains your legs more than your heart.
Lifting won't cancel out your cardio gains, either. A 2022 meta-analysis (Schumann) found that combining endurance and strength training didn't blunt strength or muscle growth, apart from a small effect on explosive power, so you can train both.
Is HYROX good for your heart in other ways?
Yes. Beyond VO2max, regular hard training tends to help your blood pressure, resting heart rate and long-term heart risk.
- Blood pressure. A meta-analysis of 93 trials (Cornelissen and Smart, Journal of the American Heart Association, 2013) found endurance training lowered blood pressure by about 3.5/2.5 mmHg on average. In people with high blood pressure, it fell by about 8/5 mmHg. In people whose blood pressure was already normal, the change was small. Strength training also lowered it slightly.
- Resting heart rate. As your heart pumps more blood per beat, it usually needs fewer beats at rest. A falling resting heart rate over months is a common, encouraging sign. Don't compare yours with friends', though, because normal values vary a lot.
- Lower risk of heart disease and stroke. The NHS says regular exercise lowers the risk of coronary heart disease and stroke, and lowers the risk of early death by up to 30%.
None of this is HYROX-specific; it's what this type of exercise does.
How much cardio do you need for the heart benefits?
Less than a race plan asks for. The World Health Organization recommends 150 to 300 minutes of moderate activity, or 75 to 150 minutes of vigorous activity a week, plus muscle-strengthening on at least two days. Three hour-long HYROX-style sessions with some easy running covers that.
To raise VO2max steadily, a balanced week looks something like this:
| Session | What it does | Example |
|---|---|---|
| Easy runs (1–3 a week) | Builds your aerobic base | 30–50 min at conversation pace |
| Intervals (1 a week) | Raises VO2max | 4 x 4 min hard, 3 min easy jog |
| Hybrid session (1 a week) | Race-specific fitness | 1 km run + one station, repeated 4–6 times |
| Strength (1–2 a week) | Muscle, bone and sled power | Squats, deadlifts, lunges, rows |
A few rules keep this working:
- Keep easy days easy. Most of your weekly time should be at a pace where you can talk in full sentences. Our training guide explains heart-rate zones.
- One or two hard sessions a week is plenty. More often leads to fatigue, not faster progress.
- Build gradually. Increase running a little at a time. Most HYROX injuries are overuse injuries in the knees and lower legs (see recovery and injuries).
- Expect progress over weeks. Most training studies run for 6 to 12 weeks and find clear VO2max gains in that time.
The beginner, intermediate and advanced training plans set this out week by week.
How can you measure your VO2max and track progress?
A lab test is the gold standard, but simple benchmarks work fine for tracking.
- Lab test. A sports clinic or university lab measures the gases you breathe while you run or cycle to exhaustion. It's accurate but costs money and needs medical screening if you have risk factors.
- Your watch. Many watches estimate VO2max. A 2022 meta-analysis of wearables (Molina-Garcia, Sports Medicine) found that devices using data from your workouts were accurate on average across groups, but individual readings could be off by up to about 10 ml/kg/min either way. Devices using resting data were less accurate and tended to read high. Use the trend over months, not the number on any one day.
- Field tests. Repeat the same test every 6 to 8 weeks: a 5 km time trial, a fixed 2,000 m row, or your average pace for a 1 km run plus station repeat.
- Heart rate at a fixed pace. If your heart rate on the same easy route at the same pace drifts lower over months, your fitness is improving.
One caution about heart rate: the "220 minus your age" formula for max heart rate is only a rough guide. A large analysis (Tanaka, JACC, 2001) found that 208 minus 0.7 times your age fits better and that the old formula underestimates max heart rate in older adults. Individuals still vary widely, so use the talk test and how hard it feels alongside any number.
Does fitness still matter as you get older?
More than ever. Fitness drops with age whether you train or not, but trained people decline from a higher starting point. In the Baltimore Longitudinal Study of Aging (Fleg, Circulation, 2005), peak oxygen uptake fell about 3% to 6% per decade in people's 20s and 30s, and by more than 20% per decade from their 70s. In the veterans study above, higher fitness was still linked to lower death risk in people in their 70s and 80s.
That's why many people race HYROX into their 50s, 60s and beyond. Our guide to HYROX over 40 and 50 covers age groups and how to adapt training.
Is HYROX safe for your heart?
For most people, yes, and regular exercise lowers overall heart risk. But a joint ACSM and AHA statement notes that vigorous exercise briefly raises the risk of a heart attack or cardiac arrest in people with existing heart disease, often undiagnosed. Those events happen mostly in people who are inactive and suddenly do hard, unaccustomed exercise.
So:
- Get checked first if you're currently inactive and have heart disease, symptoms or major risk factors. The ACSM's screening guidance says these people should get medical clearance before vigorous exercise.
- Build up over weeks. Don't jump straight into race simulations.
- Stop and get help if you have chest pain or pressure, unusual shortness of breath, fainting or near-fainting, or a racing or irregular heartbeat. Don't train through these symptoms.
- Don't race when you're ill, especially with a fever.
FAQ
Is HYROX good for your heart?
For most healthy adults, yes. HYROX training raises cardiorespiratory fitness, which the American Heart Association calls a strong predictor of heart disease and early death, and endurance training lowers blood pressure, especially in people whose blood pressure is high. The evidence comes from research on exercise in general rather than HYROX itself. Get medical advice first if you have a heart condition or symptoms.
Does HYROX improve VO2max?
Very likely. No study has yet measured VO2max before and after a HYROX training block, but HYROX training combines endurance running and hard intervals, the two methods with the best evidence for raising VO2max. Meta-analyses show gains of about 5 ml/kg/min with either method.
What is a good VO2max for HYROX?
There's no official target, and it depends on your age, sex and goals. In a small lab study, a higher VO2max went with faster simulated race times, along with more weekly endurance training. Focus on improving your own number and your field-test times rather than a fixed figure.
Why does cardiorespiratory fitness predict lifespan?
Large cohort studies consistently find that fitter people live longer. Each 1-MET step up in fitness is linked to about 11% to 17% lower risk of death. Fitness reflects how well your heart, blood vessels and muscles work together. These studies show a link rather than proof of cause, but people who improve their fitness also tend to see lower risk.
How long does it take to improve VO2max?
Most training studies last 6 to 12 weeks and find clear gains in that time with regular endurance and interval training. Beginners improve fastest. Progress slows as you get fitter.
Is my watch's VO2max accurate?
It's a reasonable estimate across groups of people but can be well off for any one person, by up to about 10 ml/kg/min in research. Track the trend over months and pair it with a repeatable field test, such as a 5 km run or a 2,000 m row.
Is HYROX safe for your heart?
For most people, yes, and regular exercise lowers overall heart risk. Vigorous exercise briefly raises the risk of a cardiac event in people with existing heart disease, especially if they're inactive and unaccustomed to hard exercise. Get checked if you have symptoms or risk factors, build up gradually, and stop if you get chest pain, fainting or palpitations.
How much cardio do I need for heart health?
The WHO recommends 75 to 150 minutes of vigorous activity, or 150 to 300 minutes of moderate activity, each week, plus two strength days. Three HYROX-style sessions with some easy running meets that. Training beyond that mostly improves your race time.
Next steps
See how heart health fits with the other benefits in the benefits of HYROX, read HYROX and weight loss if body composition is also a goal, build your week with how to train for HYROX, and choose a race to train for on the race calendar.