Edit: Dangerously misleading on one crucial point.

This started out as a short reply to the Less Wrong post Minimum Viable Workout Routine. Unfortunately I was unable to summarise my points sufficiently, so this reply grew into a post of it's own. I realize that the following is a bit rude to the original poster, and I apologize. Minimum Viable Workout Routine seems to be backed solely by anecdotal personal experience. The majority of the post, which addresses strength training seems decent, and not obviously wrong. However, the following paragraph is dangerously wrong:

A note about cardio: Cardiovascular capacity (V02 max) has shown a high degree of correlation to all cause mortality. Why aren't I recommending cardio? Because the only way to increase V02 max is with high intensity exercise. Between high intensity weight lifting and high intensity cardio, high intensity weightlifting easily wins for a newbie. A newbie, especially a significantly out of shape one, will not be capable of a level of cardio exertion that results in a significant adaptation. This can result in a lot of effort with very little in the way of improvement. This is soul-destroyingly frustrating.

Leaving this uncontested could be dangerous to your health. As we shall see, cardiovascular capacity is indeed important to survival and longevity. It is also quite easily trainable, it needs not be soul crushingly frustrating, and it should not be overlooked.

A couple of cool findings from the physiology of exercise:

Instead of having me trying to convince you, we'll take a look at the science, and see what we find.

You can assume with reasonable confidence that the findings are valid, well-corroborated, and furthermore, the findings quoted in this post have been found to apply to the general population, to the untrained, the athlete, the elderly, and the ill, even though I'm only able to present here a selection of these results.

Human physiology, and its response to exercise is surprisingly stable across genders, race, age and physical fitness. What works for the well trained athlete will also work for the utter newbie, the obese, and patients with heart disease.

Strength training is also important to health, increases in maximal strength of the large muscle groups tends to cause large increases in endurance, as measured in time to exhaustion. Why? Because if your muscles have to work slightly less hard at each movement, relative to the one repetition maximum of the muscle, you can work at moderate to high intensities for much longer.

So, let's first see that a brief strength training intervention can dramatically increase endurance:

Maximal Strength Training Improves Running Economy in Distance Runners

Purpose: The present study investigated the effect of maximal strength training on running economy (RE) at 70% of maximal oxygen consumption (VO2max) and time to exhaustion at maximal aerobic speed (MAS). Responses in one repetition maximum (1RM) and rate of force development (RFD) in half-squats, maximal oxygen consumption, RE, and time to exhaustion at MAS were examined.

Methods: Seventeen well-trained (nine male and eight female) runners were randomly assigned into either an intervention or a control group. The intervention group (four males and four females) performed half-squats, four sets of four repetitions maximum, three times per week for 8 wk, as a supplement to their normal endurance training. The control group continued their normal endurance training during the same period.

Results: The intervention manifested significant improvements in 1RM (33.2%), RFD (26.0%), RE (5.0%), and time to exhaustion at MAS (21.3%). No changes were found in VO2max or body weight. The control group exhibited no changes from pre to post values in any of the parameters.

Conclusion: Maximal strength training for 8 wk improved RE and increased time to exhaustion at MAS among well trained, long-distance runners, without change in maximal oxygen uptake or body weight

So a maximal strength training exercise of maybe 10 minutes, 3 times per week, for eight weeks, resulted in an increase in time to exhaustion of ~20% in well trained runners. So increases in strength can lead to large gains in endurance.

Cool, because endurance training is important. Endurance training makes you die less often, on average:

Exercise Capactity And Mortality Among Men Referred For Exercise Testing

Background:
Exercise capacity is known to be an

important prognostic factor in patients with cardiovascular disease, but it is uncertain whether it predicts

mortality equally well among healthy persons. There

is also uncertainty regarding the predictive power of

exercise capacity relative to other clinical and exercise test variables.

Methods: We studied a total of 6213 consecutive

men referred for treadmill exercise testing for clinical

reasons during a mean (±SD) of 6.2±3.7 years of follow-up. Subjects were classified into two groups: 3679

had an abnormal exercise-test result or a history of

cardiovascular disease, or both, and 2534 had a normal exercise-test result and no history of cardiovascular disease. Overall mortality was the end point.

Results: There were a total of 1256 deaths during the

follow-up period, resulting in an average annual mortality of 2.6 percent. Men who died were older than

those who survived and had a lower maximal heart

rate, lower maximal systolic and diastolic blood pressure, and lower exercise capacity. After adjustment for

age, the peak exercise capacity measured in metabolic

equivalents (MET) was the strongest predictor of the

risk of death among both normal subjects and those

with cardiovascular disease. Absolute peak exercise capacity was a stronger predictor of the risk of death than

the percentage of the age-predicted value achieved,

and there was no interaction between the use or nonuse of beta-blockade and the predictive power of exercise capacity. Each 1-MET increase in exercise capacity

conferred a 12 percent improvement in survival.

Conclusions: Exercise capacity is a more powerful

predictor of mortality among men than other established risk factors for cardiovascular disease. (N Engl

J Med 2002;346:793-801.)

If you want to live long and prosper, you should train your body, most importantly your heart, to be able to work hard when you can. So that it can work hard for you when it must fight for your life. With that, let us have a look at endurance training in the elderly:

Effects of High-Intensity Endurance Training on Maximal Oxygen Consumption in Healthy Elderly People

Each 60-minute training session included four repetitions of exercise at approximately 85% to 95% of maximal heart rate separated by 4-minute rest periods. The control group was encouraged to perform no additive strength or endurance training during the study period. Maximal oxygen consumption increased significantly (p < .05) (13.2%) in the TG compared to the CG. Walking economy and maximal walking speed were unchanged after the training intervention. This training study demonstrates that high-intensity endurance training significantly improves VO2 max in older adults.

Why is this interesting? Well, it seems that old people respond the same to vigorous exercise, as do young people.

But! They tend to do less of it, and consequently they gradually suffer worse health. I'm oversimplifying, but there is a causal path from physical inactivity with old age, (not because of old age) which leads to deterioration of health which leads to death. If you are reaching retirement age, or you know people who are, try to get them to move their butts before it's too late. And don't stop moving. Don't stop moving even if you suffer heart failure. Let's have a look at the effects of vigorous training in patients with heart disease:

Interval and Strength Training in CAD Patients:

This study sought to study the effect of high intensity aerobic interval endurance training on peak stroke volume and maximal strength training on mechanical efficiency in coronary artery disease (CAD) patients. 8 CAD patients (age 61.4 ± 3.7 years) trained 30 interval training sessions with 4 × 4 min intervals at 85-95% of peak heart rate while 10 CAD patients (age 66.5 ± 5.5 years) trained 24 sessions of maximal horizontal leg press.

In the interval training group peak stroke volume increased significantly by 23% from 94.1 ± 23.0 mL · beat (-1) to 115.8 ± 22.4 mL · beat (-1) (p<0.05). Peak oxygen uptake increased significantly by 17% from 27.2 ± 4.5 mL · kg (-1) · min (-1) to 31.8 ± 5.0 mL · kg (-1) min (-1) (p<0.05) in the same group. In contrast, there was no such exercise training-induced change in peak stroke volume or peak oxygen uptake in the maximal strength training group, despite a 35% improvement in sub maximal walking performance.

So this is what heart patients get in return for sixteen minutes, three times a week for two and a half months. If you're still breathing, and able to move by your own power, you are capable of the level of cardio exertion that leads to significant adaptation. You don't necessarily have to run fast, you just need to be able to get your heart rate to 85-95% of your maximum heart rate, repeatedly. For a CAD patient or an overweight person, this could mean a brisk walk. If you're out of shape, you don't have to fly across the terrain at amazing speed for your heart to get all excited.

How, exactly, does endurance training keep people healthy and alive?

Repeated intervals of brief, but high intensity endurace training causes increased stroke volume of the heart, when working at peak capacity. This carries over into the resting state, and lowers your resting pulse, your blood pressure, increases your maximal oxygen uptake, increases your working capacity when healthy, makes you less likely to get ill. If you get ill, your heart will be better at keeping you alive.

Closing thoughts:

Should you trust my opinion? I've only taken a single university course in exercise physiology. You should not trust my opinion, and this is not professional advice. But my opinion is backed up with well-corroborated scientific findings, and you should probably trust those.

The course i took was excellent. The teaching professors were were former national team coaches, they have applied their research to great effect on healthy, untrained students, CAD patients, COPD patients, youth athletes, elite athletes and billion dollar soccer teams.

Pursuing a regime of maximal strength training and high intensity interval training, you should see evident and mutually reinforcing gains in strength and endurance, and you'll not stop seeing benefits, even at the level of 100 million dollar soccer players. (Endurance and Strength Training for Soccer Players)

An final anecdote of my own:

I used to find physical exercise dis-congruent with my geek identity, I found it boring, painful, useless. Learning the very basics of exercise physiology, along with some nerdy details makes working out seem important. It helps to know why I'm doing it, I know what the expected effects are, and the expected sizes of the effects, how to avoid training fatigue, track my heart rate, track my progress, and on the whole, see that I'm on track to results like those mentioned in the studies above. I find it fun to try and figure out what is happening, and approach working out as something of a puzzle to be solved. Exercise, or the lack of it, is an experiment in health.