Summary of Exercise Research

  1. Cardio
  2. Anaerobic Exercise
  3. Stretching
  4. Sitting
  5. Works Cited

Cardio

Summary

Exercise aids in longevity for the first several hundred calories each week. After this, it’s difficult to determine whether exercise is better than a calorie-equivalent dieting. So, assuming you want to minimize exercise without sacrificing longevity, it probably makes sense to do aerobic exercise for somewhere around 75 minutes a week – just as the federal government recommends.

Experts

The US government recommends adults complete at least 75 minutes of vigorous aerobic activity each week. The May clinic agrees and notes that even “brief bouts of activity offer benefits. For instance, if you can’t fit in one 30-minute walk, try three 10-minute walks instead. What’s most important is making regular physical activity part of your lifestyle.”

On the other hand, the government recommends 60 minutes or more physical activity each day for children and 150 minutes of moderate-intensity aerobic physical activity each week for adults. They also note that these activities should last at least 10 minutes each.

At first glance, this may appear contradictory, but the key is the difference between “vigorous” and “moderate” activities. The former tend to burn twice as many calories as the latter per hour, so this accounts for the time recommendation differences. They recommend the “talk test” to tell the difference. If you can talk while active, the activity is moderate; if you can only say a few words before catching your breath, it is vigorous.

Cohort Studies

A cohort study found that for a 175-pound man, we have the following correlation between calories-burned-per week and years added to his life expectancy. However, the evidence only supports this trend for “rigorous” exercise – “non-rigorous” exercise found no statistically significant trend [803].

A different cohort study of women also found a positive trends of similar magnitude [701].

Another cohort study of men [586] found a less dramatic but still positive curve after adjusting for age, smoking consumption, alcohol consumption, BMI, hypertension, diabetes, and whether one or both parents had died before the age of 65. In particular, they found similar benefit for the first several hundred calories of exercise per week, but found that the benefits quickly leveled off.

A cohort study of Harvard alumni found that walking, stair climbing, and sports play was negatively associated with mortality, “primarily due to cardiovascular or respiratory causes.” [3148]. In particular, they report that death “rates declined steadily as energy expended on such activity increased from less than 500 to 3500 kcal per week, beyond which rates increased slightly.” They controlled for hypertension, cigarette smoking, extreme body weight, gains in body weight, and early parental death. This throws into question the previous finding of high diminishing returns to exercise after accounting for BMI. Curiously, both this and the previous study were on Harvard Alumni, had a researcher in common, and seem to have looked at similar variables.

Rats

An experiment with rats also found that rats that ran a couple miles a day lived longer than sedentary rats with the same diet, but interestingly lived shorter than sedentary food-restricted rats who were fed to keep the same weight as the running rats [214]. This would suggest that exercise’s longevity benefits result from a loss in weight and can be accomplished as easily through dieting. These findings were replicated in another study [99].

This partially contradicts the cohort studies, which show a significant gain in life expectancy for a small amount of weekly exercise. This conclusion was supported by a different study found that exercise improves longevity in rats independent of “availability of energy for cell proliferation and growth,” while providing “evidence that an increase in food intake is not harmful when balanced by an increase in energy expenditure” [119].

Anaerobic Exercise

Longevity

A literature review found that while elite aerobic athletes survive longer than the general population, there are inconsistent results for anaerobic athletes [89]. Another study found that grip strength predicted longevity after controlling for BMI [417]. but that may just mean that healthy people have higher grip strengths. That isn’t to say anaerobic exercise doesn’t have other benefits, but there’s doesn’t appear to be strong evidence that it boosts longevity.

Other Health Benefits

First, anaerobic exercise builds muscle strength and mass (see below). Though less effective than aerobic exercise, it also burns calories by boosting your metabolism [239]. In particular, working out 3 times a week was found to boost daily metabolism by about 110 calories – about equivalent to running a mile per day. Even if you don't lose weight (because you're eating more), anaerobic exercise has been linked to a reduction in body fat by 0.1% per week [370]. It apparently also increases bone strength and density (reducing the chances of osteoporosis as you age), reduces the odds of joint injury, and lowers your blood sugar. Furthermore, resistance training significantly prevents mental decline (at least in senior women with memory complaints) [123].

In short, anaerobic exercise provides “a wealth of unique benefits over those of aerobic training” and that it “should be considered an integral component, along with aerobic and flexibility training, in any exercise programme designed to promote health in all populations.”

Experts

The US government recommends “muscle-strengthening activities on 2 or more days a week that work all major muscle groups (legs, hips, back, abdomen, chest, shoulders, and arms).” However, this is kind of vague, so let's get more specific.

Diet to Build Muscles

Summary

If you’re 150 pounds, eat between 90 and 110 grams of protein per day, with no more than 30 grams in any particular meal. If you way weigh more or less than this, increase or decrease that range proportionally. Make sure you consume essential amino acids, and take creatine supplements. Make sure you eat enough calories to prevent your protein from being used as fuel; this is particularly true if you’re using whey protein supplements.

How Much Protein

Protein is required to build muscles [237]. However, there’s really no need to consume more than 1.35 or 1.6 grams per kilogram of body weight each day (at least during the first month of training) [356] [92], though other studies provide recommendations with minimums ranging from 1.2 to 1.6 grams of protein per kilogram and maximums ranging from 1.7 to 2.2 grams of protein per kilogram [67], so if you want to play it super safe, 1.6 grams of protein per kilogram is probably where all benefits stop. It’s worth noting that in all these cases, the recommendations are substantially higher than the 0.8 grams of protein per kilogram recommended to the general population.

When to Eat

However, regardless of how much protein you’re consuming, there’s no reason to consume more than 30 grams of protein in a single meal [210], which means that reasonably large people may want to consider having more than three meals per day. It’s also crucial that you digest protein both immediately after exercise [636] [5] and in the 24-48 hours that follow [232]. There is also some evidence to suggest you should eat before exercise [67].

What Kinds of Protein

Moreover, not all protein is created equal. While it’s important to consume enough protein, it’s especially important to consume enough essential amino acids [480]. Also, whey protein supplements are better than no protein, but worse than caseine protein [163], unless you combine them with another energy source [67].

Other Factors

Now, protein isn’t everything. Two other things to keep in mind are (1) that a calorie-restricted diet will cause much of your protein to be burned for energy rather than used to build muscle, and (2) that you should take creatine supplements, especially if you’re a vegetarian [89] [438].

Exercise to Build Muscles

Summary

For each exercise, you should perform 2-3 sets of 6-8 reps per day in the gym. You should go to the gym 3 days per week, until you become more experienced upon which you can reduce it to 2. You should rest around 2 minutes between sets.

Workouts Per Week

If you are a beginner, you should train 3 days per week [520], but if you are experienced, you should reduce that to 2 [225]. However, among the elderly, exercising more than once a week yielded essentially no benefits in terms of muscle growth [343]. Moreover, exercising once per week is nearly as effective as exercising three times per week for back muscles [240] and upper-body muscles, but not for leg muscles [98].

Sets and Reps per Workout

First, what you’re training for matters: fewer reps leads to greater strength while more reps leads to greater endurance [770]. For the bench press, the optimal program for strength consists of 3 sets of 6 reps [367]. In general, your reps-per-set should be between 3 and 9 [232]. 2-3 sets results in greater gains than 1 set, but 4-6 sets see no such further benefits. In particular, multiple sets are associated with 40% greater gains than 1 set in both trained and untrained people [105]. Finally, you should generally perform more than one set per session for leg exercises [216].

Finally, conventional wisdom recommends doing 3-5 sets of 8 – 12 reps each, but with more sets for larger muscle groups. Some recommendations are given here.

Time Between Sets

Waiting 2 vs. 5 minutes between sets are equally effective in terms of muscle gains [235]. Alternatively, 3 to 5 minute rest periods between sets are optimal for muscle growth, but 1 or 2 minutes “might be sufficient.”

Stretching

Summary: Stretching’s benefits are not the best. If you want to be flexible, hold stretches for 30 seconds.

The obvious benefit of stretching is improved flexibility (see citations in next paragraph). The Mayo clinic says that research on the benefits of stretching are generally mixed. It doesn’t reduce soreness after exercise, and may temporarily decrease sprinting performance. It may improve performance and reduce the risk of activity-based injuries, though this is disputed [1]. It also increases blood flow to muscles. In short, the purpose of stretching is basically to be more flexible in its own right.

Stretching for 15 seconds yields roughly 60% more flexibility gains than stretching for 5 seconds [235]. Stretching for 30 seconds, significantly boosts this gain, but stretching for 60 seconds yields no further benefits [595] [39]. Finally, it looks like you don’t get much more flexible after 4 weeks of stretching [166]. Finally, the Mayo clinic has some advice on proper stretching:

  • Don’t stretch cold muscles
  • Don’t bounce
  • Expect to feel tension, but not pain.
  • Use gentle movements in your stretching (like tai chi or yoga)

Sitting

Summary: Avoid sitting for long periods of time. Also, regarding standing desks, the best estimate is probably that they burn 24 calories per hour - but more research is needed.

Non-exercise physical activity is positively associated with longevity [60]. In particular, a longitudinal study found a “high sedentary time” causes a 1.07 to 4.33 year reduction in life expectancy [244], though that this was mitigated somewhat by high levels of physical activity. It also caused a near doubling of type 2 diabetes. The average American spends 8.5 hours a day in “sedentary behaviors” with standard deviations of around 1.9 hours [1189]. If we assume that “high sedentary time” means, 1 standard deviation above average, this could imply that an hour of sitting reduces your life by (very roughly) about 26 minutes. If you assume 2 standard deviations, this gets cut to 13 minutes.

Three different studies have all attempted to estimate the calories burned by using a standing desk rather than a sitting one. Their estimates were 21 [33], 30 [276], and 50 [50] calories per hour. Unfortunately, the confidence intervals were quite wide on all of these estimates. Assuming normally distributed standard errors, we can combine the first and last studies to achieve a pooled estimate of about 24 calories per hour, but even this has a 90% confidence interval of between 2 and 45 calories per hour. So, long-story-short, standing desks definnitely burn calories, but we don't really know whether it's negligible or not.

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