# A quick calculation on exercise

The question is—am I doing enough exercise?

I intend to provide a worked example for you to work alongside with your own calculations and decide if you should increase or decrease your exercise.

The benefits of physical activity are various and this calculation can be done for one or all of them; some of them include:

• longevity of life

• current physical health (ability to enrich your current life with physical activity)

• happiness (overall improved mood)

• weight loss

• feeling like you have more energy

• better sleep

• better sex

• fun while exercising

• reduce stress

• improve confidence

• prevent cognitive decline

• alleviate anxiety

• sharpen memory

• improves oxygen supply to all your cells

I am going to base this reasoning on “longevity of life” and “everything else”
expected life span:
I am a little lazy; and so I am happy to work with 100 years for now. For bonus points you can look up the life expectancy for someone born when you were born in the country that you were born in. If both of those numbers are not good enough make your own prediction of your life expectancy.
amount of exercise needed to produce optimum benefits:
I believe that any exercise above two hours per day will not do much more to improve my longevity that I could not get out of the first two hours. If the benefits of exercise are something like a power law; then the minimum amount required to get the most exercise can be calculated by taking a graph like this; and drawing your own lines on it as I have.

I think the most benefit can be gotten out of exercise between 30 mins and 2 hours per day.
Just how much longevity do I think I will get?
Oh its hard to say really… Some sources say:
• 3 years for the first 15 minutes a day and a further 4% reduction in mortality for every 15minutes after that

• every minute of exercise returns 8 minutes of life

• being normal weight and active conveys 7.2 years of extra life expectancy

• 75mins/​week of brisk activity = 1.8years of greater life expectancy with more activity giving upwards to 4.5years of longevity

on top of longevity there is all the other benefits I have not counted very well. For my 100 years; adding an extra 4-7 years is worthwhile to me...
And finally; the disadvantage: opportunity cost
there are 168 hours in a week. With most people spending 13 of that asleep (56hrs, 8hrs/​night), 20 hours on lesswrong per week, 40hours in an average work week, before we take two hours out of each day to spend exercising (14hours); what are we taking those hours away from? Can you do what you were doing before without the time spent exercising here?
I’m not going to tell you how to exercise or how to fit it into your life. I am telling you that its damn well important.
I was going to throw in some bayes and prediction but I have now realised I am pretty bad at it and took it out. Would love some help compiling that sort of calculation. (personal prediction that 30minutes of exercise will increase my life expectancy by 4 years)
• I’m not the sure the optimal point is going to fall in the same place depending on which factors you choose to weight. It would not surprise me at all to discover that the amount of exercise I get (typically, 6 days a week, for a total of around 7-8 hours of strenuous exercise, plus an hour or so of walking /​week, and I stand at my desk at work) is well above the optimum for long-term joint health or longevity, but it’s right where I want it for a) strong antidepressant effect (cardio) and increased confidence (weight training) and b) increased sexual attractiveness.

This isn’t hyperbolic discounting; it’s just accurate discounting. I’d rather have fewer years of life with higher quality of life than another couple years at the very end where I’m alive but too old to do much of anything.

• Exercise to stay healthy seems a pretty interesting meme of the last 50 years.

You make an assumption that more is always better with doesn’t seem to be the case. Recent studies suggest that exercising for 5 hours per week is actually worse than doing 3 hours.

We don’t really have a good theory of how exercise provides health benefits.

Ryan Holiday recently wrote:

A winner doesn’t “exercise,” they train in something (martial arts, running, swimming, biking, cross fit, boxing, weights, whatever).

Personally the more I think about the human body the more I get convinced that while the current frame is obviously better than engaging in no physical activity at all, it’s still the dark ages of knowledge.

I think it will be very interesting to see how people in 100 years will speak about how people today go jogging on concrete or go to a gym and lift weights in fixed positions and most of the people haven’t shown how to do the movement in an ergonomic way.

• We don’t really have a good theory of how exercise provides health benefits.

That depends on the exercise. The cardiovascular benefits to endurance exercise are very straightforward.

• How do you know?

Especially does your theory accurately predict how different people vary in how they benefit from endurance exercise?

• How do you know?

It is straightforward. Your cardiovascular system becomes capable of more throughput—your lungs can take in more air (higher VO2max), your heart can pump more blood, etc. What you get is called reserve capacity. People with high reserve capacity can survive illnesses which people with low reserve capacity do not.

• That’s no theory of why endurance exercise increases reserve capacity in most people. It’s jut an observation that this frequently happens. It not even good enough to tell you the optimum duration of your exercise.

I also don’t happen to be an believer in the idea that VO2max is the best possible value that one could come up with, when it comes to issues like surviving illnesses.

It took it quite a while to figure out that keeping medical ventilators at a static pressure level is a pretty bad idea. A static pressure level is really straightforward. With better research I think it’s likely we find a more complex variable that does a much better job than VO2max.

• (personal prediction that 30minutes of exercise will increase my life expectancy by 4 years)

If you assume that you have, oh, 3 hours a day free time, living an extra 4 years means that you have an extra 12 year of free time.

As exercise is taken from your free time, this is only a good deal if 30 minutes a day for the rest of your life totals to less than 12 year. 30 minutes is 148 of a day, so 30 minutes over a year is 148 of a year. This means that if you expect to live any longer than (1/​2) /​ (1/​48) = 24 years, you should not exercise.

Of course, other factors come into play (if your life expectancy increases, your extra years may be spent retired, on the other hand, you’re more likely to be ill in those extra years, etc.)

And the less free time you have, the less exercise helps, because you gain less (each year of additional lifespan provides you with less extra free time) but you lose just as much (since your exercise comes out of your free time).

• That assumes that you value time spent working or otherwise doing necessary things rather than freely chosen ones no more than time spent being dead. If your job is actually so bad that you are ambivalent between death and work, I suggest a rapid career change.

• This does not require being ambivalent between death and work, but death that is only during work hours and work.

I’m pretty sure that most people, if they could fall unconscious at the start of work, wake up at the end of work, and find their work done, would take it.

• If only 3 out of 24 hours of your time are better than unconsciousness in average (including weekends and holidays), and expect that to stay the case until just before you get senile, you’re doing something wrong. (There are plenty of exceptions, especially in the Third World, but few of them are hanging out on LW.)

What’s the point of earning all that money if you don’t have the time to spend it?

• I’m pretty sure that most people, if they could fall unconscious at the start of work, wake up at the end of work, and find their work done, would take it.

I filled that question in my evernote “census”-tag for whenever I will do a mass survey on beliefs.

• If you wake up from it afterward, it is not death in the most important respect.

• No, actually, it is. It shouldn’t matter whether the time is removed by

1. Dying by X length of time sooner.

2. Having an extra period of unconsciousness of length X stuck in the middle of the person’s life, and not dying any sooner.

Just because the person wakes up in case 2 and doesn’t wake up in case 1 doesn’t mean that the two aren’t equivalent; both involve the same duration of wakefulness, even if not the same number of wake-up moments.

• If you knew precisely when you would die, and precisely how long you would be unconscious, and the date of your death was immutable except by these two options and your quality of life while aging was totally immutable, then maybe they’d be equivalent. But living your life further in the future increases the expected length of your life and quality of life, as well as getting you massive novelty benefits from living further into the future and seeing what is there.

Death is the cessation of ‘you’. All things after you die, are inaccessible to you, regardless of how much you value them. This is why death is the Minimum Fun Location. It is not sleep; sleep is not horrible, just a mildly unpleasant need. You are claiming that having to sleep twice as much across a 100-year lifespan is the same thing as dying at 50, and that’s an utterly ridiculous claim.

• (if your life expectancy increases, your extra years may be spent retired, on the other hand, you’re more likely to be ill in those extra years, etc.)

I’d expect most of the life expectancy-increasing effects of exercise to also shift the age at which you’ll get ill by almost the same amount, while hardly affecting the age at which you’ll retire, so I’d guess most of the extra time would indeed be while you’re retired but still healty enough.

• If you assume that you have, oh, 3 hours a day free time, living an extra 4 years means that you have an extra 12 year of free time.

Only if you expect to never retire.

• There are opportunities to exercise at no cost in time. I usually bike to work and to go into town, which takes no longer than driving, and the harder I ride, the less time it takes. I walk up four stories to my office, which takes no longer than the lifts, and I’m usually up and down those stairs 2 or 3 times in a day. I play taiko, which is great fun, but is also pretty strenuous. So that’s 7 miles of biking and around 100 vertical feet of stair-climbing every working day, and a cardiac workout of a few hours a week, for free.

There are other things I do, but these are the ones that effectively take neither time nor money to do.

• I have a semi-recumbant exercise bike that allows me to work while exercising. It’s not terribly expensive to get something to put a laptop on while using a treadmill or bike.

• There is something that makes me skeptical about “exercise” considered as an abstract quantity. There are many different ways of doing “exercising”, and they have many different effects on the body. How much exercise you do (but then, counting in hours ? spent calories ?) do matter, but in which conditions also matters a lot : how regularly, what kind of exercise, …

Exercising usually is good for urban sedentary people who “naturally” don’t do much of it, but it can also have negative side-effects, in accelerated aging or articulation damage. Professional sport players have a very short average lifespan, and it’s not only because some of them use drugs.

There is surprisingly few literature on the topic (or I couldn’t find it), but from what I remember finding, something important is the regularity (doing 3 hours of exercise twice a week is not nearly as good as doing 12 hour each day, even if 12 hour each day is just 3.5 hours in total) and the kind of activity : constant medium/​low intensity, long duration activity (walking, long-distance running, bicycling or swimming at a moderate speed for a long while, …) is much better than variable intensity (like ball games, where you run and stop and run again and kick and …) or high-intensity short-duration (like sprinting).

As for opportunity cost, something to consider is doing exercise that fits a purpose, instead of just “wasting” hours doing it, for example, running/​walking/​bicycling instead of using a car means you do some exercise but also save on money and on accident risks, especially if your environment (public transport network, proximity of things, …) allows to not own a car at all (making the money gain very significant), or finding an activity that you actually enjoy so the time isn’t fully wasted.

• Professional sport players have a very short average lifespan, and it’s not only because some of them use drugs.

Olympic athletes, however, have a longer than average life expectancy. This held across endurance, team, and power sports, with individual variations; the consensus (note: this isn’t in the linked article) seems to be that sports with a lot of hard physical contact, like rugby or boxing, are bad enough for you to overcome the general benefits of exercise. There doesn’t seem to be consensus about longevity effects of endurance vs. power sports, or about variation vs. monotony in exercise; the linked paper finds higher longevity for endurance athletes than the other two categories, but I’ve read papers finding differences in the opposite direction.

(There was some buzz recently about a different paper finding that players of very-low-intensity sports like golf enjoyed the same longevity benefits as players of high-intensity sports, but I think that’s been overinterpreted in the press; to name one confounder, low-intensity athletes quite often cross-train in higher-intensity activities.)

• Olympic athletes, however, have a longer than average life expectancy.

We have to very careful with correlation/​causation here. Olympic athletes are a select group of people who won the genetic lottery by certain measures. It might well be that their apparent longevity is a pure selection bias.

• On genetic grounds, at least, I might actually expect a bias in the opposite direction. The “genetic lottery” as you put it works on specific traits; there’s no general qualityOfPerson attribute (though see below). We might expect a few of those traits (like those relating to cardiovascular resilience, say) to contribute both to athleticism and longevity, but I’d expect some to involve tradeoffs between the two: we could imagine a trait that improved metabolic efficiency at the cost of adding oxidative stress, for example, or one that made muscle cells respond quicker to injury (==faster strength gains) but increased the chance of cancer in those cells.

Mutational load might be an important confounder here, though, as something that I’d expect to affect fitness in a very general sense. And of course I’d expect Olympians to come from higher social classes on average, since those are the families that have the money to support intense early training. The linked paper controlled for “occupational group”, but I don’t know if that completely captured the latter.

• The “genetic lottery” as you put it works on specific traits;

Yes, but the selection works from two directions: to be an Olympic-class athlete you need to a have a major advantage in some particular trait and no noticeable fitness disadvantages. In a random selection from the population there will be somewhat-ill people (e.g. with chronic diseases, say, autoimmune), but these people will be absent from the Olympic athlete sample. That by itself is probably enough to generate a noticeable longevity advantage for the athletes.

• consensus (note: this isn’t in the linked article) seems to be that sports with a lot of hard physical contact, like rugby or boxing, are bad enough for you to overcome the general benefits of exercise.

This based on any evidence, or is this just fashion?

• Can’t be bothered to dig up a reference, but boxing and American football at the very least are pretty unambiguously unhealthy: repeated concussions do nasty dementia-like things to your brain, and the incidence rates are surprisingly high (I think the phrase to google is “chronic traumatic encephalopathy”). I also wouldn’t be surprised if the kind of joint problems that contact sports tend to give you led to mobility problems and attendant issues later in life, although that’s a little more speculative.

• Professional sport players have a very short average lifespan

No, they don’t.

• I personally find a certain about of exercise (1-2 weight-lifting sessions a week) worthwhile even without considering long-term effects. Short to medium- term benefits include improvement of mood, improvement of appearance, and elimination of back pain.

• I’ve started running more seriously a couple of months ago, and it’s just fantastic. Once I got to the point that 30 minutes became easy, it really started to be its own reward. I get to explore my town—Strava allows me to see the routes of other runners, and if you pick the more experienced ones, they tend to run in beautiful places I’d never see otherwise. I get to see the seasons change. I get out of my head and away from the keyboard. I lost 10kg since summer. Can’t recommend it enough.

• I have not done the research, but I suspect that this open-loop calculation is not really worthwhile. People are very different, and if you want to achieve certain benefits you ought to close the loop and measure these benefits directly, then adjust the amount and type of exercise accordingly.

• I largely agree, but a lot of the benefits may not be apparent for 10 years or more. A feedback loop that long is hard to use and not strongly motivating for most people.

• a lot of the benefits may not be apparent for 10 years or more

I struggle to think of any benefits which become apparent after 10 years. Longevity could be one, but it kinda never becomes apparent. And for specific long-term results (e.g. you don’t develop the metabolic syndrome in your middle age because you were a runner in your 20s and 30s) there’s little hard data.

• Longevity could be one, but it kinda never becomes apparent. [...]

That was rather my point. (Note that I said “10 years or more”.)

[EDITED to fix a trivial typo.]

• 2 hours per day seems like way too much. I work out 3x per week, 1 hour each time. (Though I did start 4x per week, 1 hour each, when I was initially losing weight). Just make sure to keep it high intensity. When I’m tempted to slack off I ask myself if I’m here to kill some time by moving around, or if I’m here to achieve a damn objective as efficiently as I can so I can get back to doing other things. If after an hour is up I’m physically capable of continuing for another hour, I obviously was just wasting my time.

• And finally; the disadvantage: opportunity cost

there are 168 hours in a week. With most people spending 13 of that asleep (56hrs, 8hrs/​night), 20 hours on lesswrong per week, 40hours in an average work week, before we take two hours out of each day to spend exercising (14hours); what are we taking those hours away from? Can you do what you were doing before without the time spent exercising here?

Note that exercising affects your need to sleep, so more minutes spent exercising don’t necessarily translate to fewer minutes available for other stuff on a one-to-one basis.

But there are two contrasting effects here—by exercising, you’ll need to sleep more, but you’ll also get more hours of actual sleep per hour spent in bed trying to sleep—and it’s not obvious which one will dominate. It probably depends on lots of things.

• But there are two contrasting effects here—by exercising, you’ll need to sleep more, but you’ll also get more hours of actual sleep per hour spent in bed trying to sleep

I’m not sure whether that’s true. Dancing well can in my experience mean sometimes mean that I get by with less sleep.

• That’s probably the second of the effects I mentioned, if you interpret “actual” narrowly enough.

I’d guess that with different types of exercise, e.g. weight training, the first effect might win instead.

• I’m not sure. Meditative trance states do have shown in some cases to be able to replace sleep. When I dance well I think it’s plausible to be in a trance state which cuts down on sleep.

• In general, it’s more important to exercise regularly than for massive periods of time. In fact, the massive periods of time required by athletes are often detrimental to health (performance not always equaling health, for example see serious injuries in elite athletes as a result of their sport) and should be avoided by those without significant performance goals.

A single workout per week involving both cardio and weight training is sufficient for many people provided diet is in check. 45 minutes or less is the ideal number—many people will do 15-20 minutes of cardio with the remainder being made up of high-intensity interval/​circuit weight training covering most major movements. However, ideally, short workouts daily are more useful than longer workouts less frequently.