September 20, 2021

Exercise & Physical Health

#176 – AMA #27: The importance of muscle mass, strength, and cardiorespiratory fitness for longevity

"If you have the aspiration of kicking ass when you're 85, you can't afford to be average when you're 50." —Peter Attia

Read Time 24 minutes

In this “Ask Me Anything” (AMA) episode, Peter and Bob discuss the longevity benefits from greater cardiorespiratory fitness (CRF) and greater muscle mass and strength. Conversely, they dive deep into the literature showing a rapid increase in morbidity and mortality risk as fitness levels decline with age. They also try to tease out the relative contributions of CRF, muscle mass, and strength. Additionally, they discuss the impact of fasting on muscle mass, the potential tradeoffs to consider, and finish by discussing why it’s critical to maximize your fitness level.

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AMA #27 Sneak Peak

We discuss:

  • VO2 max and its association with cardiorespiratory fitness [2:45];
  • Changing mortality risk based on VO2 max and cardiorespiratory fitness [7:45];
  • The profound impact of improving cardiorespiratory fitness [15:15];
  • Muscle mass, function, and loss with aging: how it’s defined, measured, and the cutoff points for sarcopenia [25:00];
  • Increasing mortality risk associated with declining muscle mass and strength [40:00];
  • Muscle size vs. strength—which has the bigger impact on mortality risk? [58:00];
  • Evaluating the cumulative impact of cardiorespiratory fitness and muscular strength on mortality risk when put together [1:03:30];
  • Investigating the rising incidence in deaths from falls, and what role Alzheimer’s disease might play [1:09:00];
  • The impact of fasting on muscle mass and the potential tradeoffs to consider [1:14:30];
  • The critical importance of working to maintain muscle mass and strength as we age [1:20:30]; and
  • More.


VO2 max and its association with cardiorespiratory fitness [2:45]

Overview of question being asked today: Does better cardiorespiratory fitness lead to less mortality and does lower cardiorespiratory fitness lead to higher mortality? Or is it at least associated?

Common terms:

  • Most common thing in the literature is either METs, metabolic equivalents or VO2 max
  • For a VO2 max test…
    • You are hooked up to an indirect calorimeter—a device that provides complete occlusion around your mouth and your nose so you’re only breathing through your mouth
    • The device has two sensors on it
      • One sensor measures the concentration of oxygen that is being expelled
      • The other one is also measuring the concentration of carbon dioxide that’s expelled.
    • Because we know the concentration of oxygen and CO2 on the way in, by knowing what comes out and obviously oxygen will be lower, CO2 will be higher, we know how much carbon dioxide was produced and how much oxygen was consumed
    • Knowing those two things gives you a “flow rate” — VO2 and a VCO2
    • This can tell you how much energy you’re utilizing via something called the Fick principle
      • Total energy consumption is ~3.94 times VO2, and ~1.11 times VCO2 at any point in time
  • For instance, for this minute VO2 was X, VCO2 was Y, then you apply it to that equation and it will tell you that you were utilizing, say, 10 kilocalories per minute which would be 600 kilocalories per hour
  • During Peter’s zone 2 exercise, it tends to be about 780 kilocalories per hour
  • But now what we’re talking about is something different which is… what is the maximum utilization of oxygen?
  • If you make somebody work harder and harder and harder, at some point they will reach a maximum at which point, they can no longer utilize more oxygen

⇒ As to the “why” they can’t utilize more oxygen, see the Alex Hutchinson podcast

  • We talked about some of the alveolar limitations, how much of that is being limited at the gas exchange surface versus
  • How much of that is being limited in the muscle.
  • But regardless of which of those it is—and it’s possible it’s a combination or it’s possible that at low levels of fitness it’s more in the muscle, and at high levels of fitness, it might be more in the lung—but that number is the VO2 max

When you’re doing the test, it’s measured typically in liters per minute

  • then we normalize it by body weight to get milliliters per kilogram per minute
  • The fittest of the fit are going to be north of 80
  • But what does that mean?
    • It means they are north of 80 milliliters of oxygen per kilogram per minute
  • The highest ever recorded VO2 max was a cyclist named Oskar Svendsen who measured about 96
  • Any sort of elite cardiac type athlete, a runner, cyclist, rower, those sorts of athletes, they’re generally going to be above 70


Changing mortality risk based on VO2 max and cardiorespiratory fitness [7:45]

Figure 1. Patient survival by performance group. (Mandsager et al., 2018)

Overview of the experiment:

  • A group of people that were 53 years old on average
  • Ran them through a VO2 max test and then it ranked them
  • Low were people who scored in the bottom 25th percentile
  • Below average was the 25th to 50 percentile
  • 50 to 75th percentile was above average
  • High was 75th to maybe 95th
  • Elite was just that top 5%. 
  • NOTE: Each of these levels do NOT represents 20% of the population
  • A total of 122,000 patients
  • The low, below average, above average, and high have about 30,000 participants in each one of those groups
  • And then the elite group has a little over 3,500


  • Looking at all-cause mortality there’s a pretty clear trend
  • The two things that stand out are, 
    • i) there’s kind of a monotonic relationship between fitness and mortality
    • ii) By far the biggest gap is between the people in the bottom 25%. Which are categorized as low fitness, and basically everyone above them.

Figure 2. Risk-adjusted all-cause mortality. (Mandsager et al., 2018).

When sort of lumping everyone in together, male and female, if you have low fitness and then comparing it to everybody else, what’s the risk reduction?

If you go from low to below average, to above average, to high to elite, you can see what is the hazard ratio

Important stats

  • Going from just being low to being below average is a 50% reduction in mortality over a decade
  • If you then go from low to above average, it’s about a 60% or 70% reduction in mortality
  • Then it just continues monotonically to increase
  • The lowest improvement is going from high to elite—”That doesn’t buy you a whole heck of a lot. It is still statistically significant.
  • To see that you have to look at Table C
  • remember, the hazard ratio for mortality is the reciprocal of the hazard ratio of risk reduction
  • Tables A and C are basically showing you similar things in the group comparison

Here’s what’s interesting…

  • If you compare someone of low fitness to elite, it is a five fold difference in mortality over a decade
  • They put this in the context of other things that we commonly understand as being problematic for mortality… Namely, smoking, coronary artery disease, Type 2 diabetes, hypertension, and end-stage renal disease
    • That’s a 41% increase in mortality over the decade
    • Coronary artery disease, 29%. 
    • Diabetes, 40%. 
    • High blood pressure, 21%. 
    • End-stage renal disease, about 180% increase in mortality
  • But now when you compare that to the differences in these fitness levels, it gives you a greater appreciation for how much improvement in mortality comes from improving your fitness
  • If you look at the biggest driver of mortality, which would be end-stage renal disease in this cohort, it’s the same as going from low cardiorespiratory fitness to above average cardiorespiratory fitness
  • So going from the bottom 25th percentile to being in the 50th to 75th percentile… “which is a totally achievable feat

{end of show notes preview}

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  1. What’s the hazard ratio for the activity of the picture at the top of this post? 😆….. not to say I’m not guilty of doing the same with my nephews and my own son. Lol. All in all it would probably follow a similar monotonic trend for fitness too. Being 6’4″ there’s certainly a further fall though.

  2. Thanks for a very insightful conversation. I am 63 and took up serious weight training about 6 months ago. I have never felt so energised and so strong and am motivated to keep at it, especially given what I have learned today.

  3. OK, is Bob any relation to Bobby Orr? (The NHL’s Indisputable GOAT). Bob looks a lot like him (40 years ago). Particularly with all those Bruins banners behind him.

  4. OMG…. I recently let my subscription lapse and got the email with the 18 minutes auto clip of today’s AMA #176. This is the best work you guys have done in my 3 years of being a subscriber. Great investigative work, awesome analysis on studies and practical steps of how to take action to affect one’s healthy longevity.

  5. Peter – I was sort of surprised to hear the negative spin on fasting at the end. I guess you were implying more longer fasts like 2-3 days. I do a 16×8 intermittent and I’m pretty sure I won’t get muscle mass loss in those short time-frames right? I still believe (and hope) that a shorter feeding window is much better for long term health because it helps with autophagy and reduce insulin in blood. I usually lift in a fasted state before eating. Also, I REALLY look forward to guidance on strength programs for people in their 50’s. I like your instagram video spots but looking for more comprehensive guidance on workouts. Thanks, I love The Drive!

  6. With respect to Figure 5 from the AMA, Peter writes, “not too happy about that in the spirit of needing more muscle. I want to have my ALMI be as good as my cardiorespiratory fitness. I need to bulk up my arms and legs more.”
    It seems we really want to see ALMI adjusted for FMI—that should show your ALMI as a much higher percentile, perhaps as high as your cardiorespiratory fitness. Ofenheimer et al write, “Since LM and FM are related closely to each other, and weight changes affect both tissue components, obese people are supposed to have higher LM values than normal-weight subjects [17]. Hence, it is important to consider the amount of FM in the establishment of LM reference centiles.” See Figure 5 at the very end of their paper (page 1189), where they show age curves for LMI separated into FMI quartiles. It’d be nice to see similar graphs for ALMI.

  7. Brilliant talk. You’ve saved me a decade of research/reading.
    Peter, you often talk about your hatred of all evidence epidemiological. Is this all we’ve got in the exercise/body composition field?
    Likewise, you’ve reinforced to me association is not causation. Will getting bigger arms really improve your longevity? I struggle to imagine biological plausibility for that one.
    Thanks again.

  8. I have to comment that Peter’s delivery when stating, “We like to have our tables in a sans serif font” @15:30 is hysterical. It’s dry and I don’t think he meant to be funny, but that just makes it funnier.

  9. Sarcopenia, measured as cross sectional size of the psoas relative the the adjacent vertebral body, has been shown to be a predictor of mortality following hip fracture surgery

    and probably even a risk factor for falls and hip fracture themselves

    but can be ameliorated through exercise (walking) in the elderly.

  10. Peter the comedian. I can absolutely hear you saying “It’s a gap in our data, we need to address intentional falling and its impacts on the evidentiary landscape.”

  11. On Vo2 max training, I purchased an indoor bike called Carol because of a HIIT protocol it is designed around (3 rides a week, with each ride having two 20 second sprints). It monitors heart rate and watts, and adjusts resistance on its own. ACE did a study with it and the study results seemed very positive, so I took the plunge. Too early for me to tell if it works, but curious if the Peter Attia has evaluated this bike and the specific HIIT protocol it is designed around.

  12. “the eyeball analysis is you probably get more bang for your buck on cardiorespiratory fitness, but doing both [cardiorespiratory fitness and improving strength] is better than doing one or the other”
    How is cardiorespiratory fitness defined? If it’s the same as VO2max then I think there’s a huge chunk of the puzzle that’s missing, incomplete, or misleading. Aerobic fitness (<VT1) is far more important than VO2max, yes?

  13. Are the associations between cardiovascular fitness and mortality causal? i.e are there studies that have made the change in someones fitness and then looked to see if the have better outcomes?

  14. Great podcast, thanks!

    As a trainer of older adults, one issue to consider is that nearly everyone who starts doing some sort of cardio exercise increases the mileage/volume too quickly and are prone to getting some sort of tendon issue which reduces the consistency and ability to create the habit. Starting with some strength/movement training prepares the connective tissue in very much the same way and less prone to continuous overload.

  15. Hi Peter!

    Thanks to you and your team for all the great work you do!

    I have 2 questions for you:

    1. I have a better understanding now about the importance of cardiorespiratory fitness and strength for longevity, but I hardly ever hear anything about the importance of flexibility. Seems to me that people can be good at cardio and/or strength, but not necessarily flexible. It is even common to see very muscular people that cannot even touch their toes or that have a really stiff back or hip. I’ve done a little yoga during the past few years and lately joined a gym and practice HIIT twice a week, and now more than before I see how important it is to combine flexibility exercises with strength and cardio workouts as well, I feel my body appreciates it. Also, the other day I slipped in my bath tub, and I think that both, my strength and flexibility saved me from getting injured, because I was able to hold myself for a while in a very uncomfortable position. What can you guys say about the importance of being flexible for longevity?

    2. I’m a 38 year old women, 104 lbs, 5′ 2″, no children, and have noticed that my performance at the gym lowers significantly during my period. My muscles feel weaker, I get dizzy and nauseated easily, I feel low energy, I have cramps… The other day, just by coincidence, I had blood work done during my period and find out that I might be getting a little anemic during my periods (red blood cell count = 3.8 Million/uL, hemoglobin = 11.4 g/dL, hematocrit = 34.2%, MCV = 90 fL). Could this explain the low performance at the gym? My doctor told me I don’t have iron-deficiency anemia, but blood loss anemia, but I don’t think my periods are that heavy… is this normal? How can I prevent or recover quicker from this?

    Big thanks,


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