More than ten years after they were first published, the American College of Sports Medicine and the American Heart Association have updated their physical activity recommendations for adults.
Bill Haskell: Yeah, these guidelines try to make the core guideline reasonably simple and straight forward for the general adult population that's not in really good shape but at least does some walking. But if you are very unfit then for you maybe two to two and a half miles per hour will be moderate intensity. Ideally we would like to have people walking at a moderate intensity relative to their capacity. So Steve is correct that at lower levels of fitness or exercise capacity walking at a slower speed is going to be moderate for you but if you're a regular jogger then probably very fast walking or jogging is going to be moderate intensity.
Norman Swan: You also suggest that for two days a week you get vigorous.
Bill Haskell: That's an option, the guidelines prior to 1995 in most countries including Australia suggested that people get more vigorous activity and that typically was said that you should get vigorous activity for at least 20 minutes three days a week. And vigorous there was defined as jogging or an equivalent kind of sport or recreational activity. In the 1995 recommendations there was a statement that said the prior more vigorous recommendations still applied but that was never very clear. So here we say the core recommendation for most people to get started is this 30 minutes of moderate intensity activity five days a week. But also states that in place of that if one has been somewhat active that they could substitute the vigorous intensity sessions three times a week, about 20 minutes per session of vigorous activity, you don't do both together necessarily to meet the target or minimum requirements - one or the other is adequate......
Bill Haskell: Not in the sense of accumulating kind of at least 30 minutes for general health promotion. But there's one caveat and that is all of that activity counts if one of your primary goals is to lose weight. In these new guidelines we say for general health purposes you should target at least the 30 minutes of either continuous or bouts of at least 10 minutes duration during the day. And if you're not at what you want to be in terms of target weight you should add additional expenditure, energy expenditure to that, additional exercise as well as to try to restrict some calorie intake. That additional activity can be built in by doing all of these little activities during the day......Norman Swan: People think that exercise, I do it now and I benefit in 15 years time but my understanding is that the benefit of exercise is actually immediate and over the next 3 or 4 days then it declines, and then if you do it again you get the benefit again. In other words there's an almost immediate benefit from exercise.
Bill Haskell: Yeah, there's probably a combined benefit. One is delayed kind of training benefit but let's just take the area of helping to prevent diabetes. Every time you go out and let's say do a 30 minute brisk walk, there are enzyme changes that occur that allow insulin in your body to be more efficient so the body needs less insulin to process the glucose for it to go into various tissues. And that lasts for 24, 36 maybe 48 hours something in that range. So kind of into the exercise and then for this period afterwards actually the body is more efficient in terms of using its insulin. So you need less insulin and so the pancreas has to work less hard.
Norman Swan: Inflammation goes down as well.
Bill Haskell: Yeah, and I'm using insulin as just one example because we have so much data in different populations showing this to be a fact. So one way to look at a bout of exercise is simply like a pill - let's say we had a pill that made insulin more efficient so you had to use less insulin and each bout of exercise is a pill so the doctor prescribes that at least every two days you need to take this pill in order to keep your insulin sensitivity high. So yeah, there are things like immune function with moderate intensity exercise, there's a lowering of blood pressure so let's say your blood pressure is up just a little bit, you're not on medications or even if, let's say it's up high and your on medications and you go out and do a moderate intensity of exercise- 30 or 40 minutes. In some individuals their blood pressure after the exercise is going to be lower for 12, 24 hours even and those have been studies carefully done with ambulatory blood pressure monitors. So yeah, there's a lot of immediate effects so kind of our old idea when we were thinking about increasing your fitness which takes a period of time to see that, and so oh, well I don't see the benefits for you know 6 or 8 weeks or something, for many of these health benefits particularly those that are related to kind of metabolic function, those can occur with each bout of exercise.....
Bill Haskell: Well surely in terms of resistance exercise you know one can start by walking up stairs just to increase the strength of the thighs, some gardening where you're lifting, pulling, pushing, shoving, all of those activities have a sufficient resistant component that that's going to begin to you know increase strength. One can then begin to do you know callisthenics, push ups if you have the strength pull ups, all of those activities, you don't need to go to a gym or you don't even need to buy any special equipment. We continue to emphasise that for much of the general public while the more vigorous recommendation still applies that from a safety standpoint and a kind of a risk benefit perspective it really seems that this moderate intensity activity on a regular basis carries with it a lot of benefit and really minimal risk. It kind of moves it out of this clinical model of thinking you have to get approval from your physician or get some special examination in order to start.Norman Swan: And once you're feeling fitter, if you want to get even fitter and do the jogging five times a week rather than the moderate exercise and do a day or two or stair running, how much extra benefit do you get from that versus just getting off your bottom?
Bill Haskell: The big goal is to get everybody off their bottom but also in these guidelines we point out that there is this added benefit from doing more than this kind of initial recommendation. And as we state in the recommendation while we know there's added benefit it's hard to kind of quantitate that in a very precise measure to say OK general health, if you do 60 minutes versus 30 you're going to get twice as much. You're going to get substantially more but whether it's twice as much we really aren't sure, we just haven't done the research to know for sure.
