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Exercise isn't necessarily good for people - Input Junkie
June 7th, 2013
11:04 am


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Exercise isn't necessarily good for people


My comments are in square brackets. Everything else is my notes on the Jamie Timmons lecture from the video.

Short version: 12% of people become less healthy from exercise. 20% of people get nothing from exercise. This is a matter of genetics, not doing exercise wrong.


Ask a hundred people about exercise, you'll get a wide range of answers about what exercise is and what good it might do for health, and the same for health professionals.

You need to focus on the evidence that exercise affects particular health outcomes.

Weight and health are not strongly correlated.

BMI is problematic.

There's a recommendation for 150 minutes of exercise/week, but this isn't sound.

People who *report* being active have better health.

People who are fitter have better health.

These are not evidence that having a person with low activity take up exercise will make them healthier. Nothing but a supervised intervention study is good enough.

Improved lifestyle is better than Metformin for preventing diabetes. (Studies)

Exercise + diet modification has a powerful effect of preventing and slowing the progression of Type II diabetes. People with Type II have more cardiovascular disease (heart attacks and strokes). However, it doesn't follow that the lifestyle changes which help with Type II will also help with CVD.

[I'm surprised] Diabetes doesn't kill, CVD does, and a major motivation for the NHS to care is that CVD is expensive.

[9:45] Two studies which find that lifestyle intervention has no effect on CVD in diabetics.

[11:00] One study which found that lifestyle intervention prevents Type II but doesn't affect microvascular disease (blindness and ulcers). [I'm not sure what this means. Maybe people can have the ill effects of Type II without the disease showing up in their blood sugar levels?]

There are no supervised exercise-only intervention studies which show that exercise prevents long term disease progression.

[13:00] The usual advice on exercise from the NHS (pretty similar in the US): Aerobic exerise must raise your heart rate and make you sweat to be benefiscial. The more exercise you do, the better. Do a minimum of 150 minutes/week of aerobic exercise + strength training. If you do more than 150 minutes/week, you'll gain even more health benefits. Using a skipping rope is an example of vigorous intensity exercise.

People aren't following this advice, and a major factor is the amount of time required.

The advice is based on best guesses.

[15:55] Exercise will increase aerobic capacity in 80% of people (lowers all-cause mortality), improve insulin action in 65% of people (lowers type II diabetes by 50%), reduce blood pressure in >55% of people (lowers strokes 25%), increase good cholesterol in 70% of people (less vascular disease), promote muscle and bone mass (? less fractures and 'aging')

[17:40] Exercise response graphs. The average person gets a 15% increase in aerobic capacity, but a few get less capacity if they exercise.

Insulin response-- average of 20% improvement. Some people get better, some get worse. A high proportion, maybe the majority, have little or no change. The people in this chart were doing 150 minutes/week of supervised exercise.

[20:00] High-intensity exercise is exercise which depends on stored energy, there's no way to take in enough oxygen to contribute. An athlete might be able to continue for 10 minutes. The average person can continue for more like 30 seconds to one minute.

[22:00] Experiments with high-intensity/rest intervals:

3 x 20 seconds of high intensity.

[25:00] Charts showing flattened glucose spike (there probably was a peak, but the test missed the moment) and less isulin in the blood after only two weeks of 6 x 30 seconds interval training (total 7 minutes).

[30:54] "Advice has been based on what epidemiology methods can detect, not what is actually important or required."

Health questionaires don't include things like 20 seconds of running for the bus.

[33:00] Ten days of bed rest will make healthy people insulin resistant.

[35:00] It looks as though modern hunter gatherers expend about as much energy/mass as Americans on the east coast do. [I found I could make sense out of the graphs by using full screen.] This evidence suggests that people are eating more rather than moving less.

The evidence for 7 minutes of HIIT three times a week isn't completely solid, but it's at least as good as the evidence for 150 minutes/week.

[38:36] ..... Epidemiology of a sort-- evidence that eating chocolate makes it more likely to get a Nobel prize. Beautiful corelation! The Swiss eat the most chocolate and get the most prizes. The Swedes are an outlier-- they don't eat as much chocolate as they should to get so many prizes. That the prize is given in Sweden might have something to do with this. Cocoa has flavenols which slow age-related cognitive decline, but the corelation is probably just a coincidence.

[40:00] 12% of healthy people make their blood pressure **higher** by exercising 150 minutes a week. 20% get little or no improvement.

[42:00] Graphs of low responders for aerobic capacity, muscle mass, and insulin sensitivity.

Exercise does slow progression of diabetes on the average, but that doesn't apply to all individuals.

[44:47] There's no obvious indicator to tell high responders from low responders in advance. You have to either check the genes or track the results of exercise.

[45:00] Finding non- or adverse responders: change in aerobic fitness is 60% genetic, insulin sensitivity is 40% genetic, strength is 50% genetic. These are estimates from family studies, including twin studies.

There are 10 million genes variants which might have at least a 5% effect.

[47:35] There's a group of 27 genes which together can 'predict' gains in VO2max.

It isn't necessary to understand how the genes work to create their effect as long as that effect is predictable, and it's possible that we will never understand something so complex.

There may be drug combinations which can make exercise safe and effective for non-adaptors. There's research happening.

It's possible to breed rats which are better at responding to training.

[53:52] A life-style program will *on average* reduce the risk of developing type II diabetes.
We *don't know* whether exercise-training on its own will reduce heart-disease, angina, etc. It does improve risk factors and symptoms.
If *you* have a risk-factor for ill-health, we *can not* be sure that exercise will help. (12% *adverse* responders, 20% no effect)

[57:00]Public health (what advice should the government give?):
1 minute a day of high-intensity sprint cycling reduces major risk factors. [For what proportion of people?]

People tend to like brief high intensity exercise better than longer low intensity exercise.

North American study: 150 minutes/week of exercise increase one's carbon footprint by 15% (food, laundry, showers).

Safety: 2 million marathoners have been studied. Very low fatalities. HIIT isn't likely to be more dangerous. [Ack! Ack! Ack! What happened to all the care about evidence? Marathoning isn't sprinting. Fatalities during the race aren't the only thing that can go wrong. People who do marathons aren't randomly selected.]

HIIT has be done safely by medically supervised diabetes and heart failure patients.

It would take a billion dollars to do a thorough supervised intervention study. Some pieces of it have been done. This is much less than big drug companies spend, without much results.

The current hope is finding the gene markers and then useful drugs for non and adverse responders.

There are no average people!



Summary of a TV show which has more details about High Intensity Interval Training.

This entry was posted at http://nancylebov.dreamwidth.org/1010433.html. Comments are welcome here or there. comment count unavailable comments so far on that entry.

(2 comments | Leave a comment)

[User Picture]
Date:October 21st, 2014 02:09 pm (UTC)
This makes complete sense to me.
[User Picture]
From:Jack Hourly
Date:January 23rd, 2016 06:26 am (UTC)

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