So now I want to get a little bit into some measurement issues. So let's just think, any problems that you see with the question of how many times per week do you exercise? >> I think like sometimes people may think about like two weeks ago. I exercise a lot so they might like over report it and then there's also the social desirability. Exercise is known to be like something like eating healthy. So they will probably say like, I exercise more than I actually did to make themselves look better especially in the case of self-report. >> Yeah, absolutely. >> And this is the way it's often asked and kind of larger scale surveys to or even for doctor's office, right and use anything also. Also it assumes that people are exercising. It's not like a yes or no question to begin with like do exercise? It's assuming that they do and then asking how frequently yeah, would definitely cause people to maybe over report. >> Mm-hm, mm-hm. And what about someone who does stretching every day. What if someone thinks of exercise as being like only boot camp or something and doesn't think about it as being taking a walk around the block. >> Definitely. >> Right? >> Yeah. >> Okay, so people in the class were asked to respond to a survey these data are actually not this classes survey. It's last year's, I didn't have time to get the data together. But everyone in the class answered a series of questions about their health and what what no one knew because I'm always kg doing things in the background. And said everybody was actually randomized at the outset of the survey. And one group of students were asked the question in one way and another group was asked it in another way. Kind of a different, subtle changes in the wording of the question. And so some people receive the question, how many times per week do you typically exercise or work out? There are some problems built into this question. First one being like people are, it's up to them to figure out what working out or exercise means or what I meant by it, okay. Other people were posed the question, over the past week, how many times did you workout? So then we're talking about typical versus over the past week, okay? And over the past week, also has some problems because as you said, people will, this past week might have been a little unusual. It might have been, they were moving, weather was bad. It was the beginning of the semester. It was cold. It was too hot, there are all these kinds of things that can affect the snapshot of behavior, okay. So ready for the results? >> Mm-hm. >> Okay, here we go. Again, this is last year, but people talking about how frequently they typically exercise. And this was why is PH students last year? No reason to think that they're a lot different from students this year and we see really more than half of the of the group typically exercising at least three or four times a week. That's actually, it's at the shows a nice normal curve distribution. All right, but now we ask, how many times people exercise in this past week? Seeing very different pattern of responding. Which this happens every year with every group of students with adults in the community. This is a phenomenon that we that we know there's back to measurement which one's more accurate and which one, what would be our preference for the one the in theory. All the noise over the past week should balance out but do we want to know typical, is typical more subject to social desirability bias? Yes, it is, yeah. Then only doing a one-week white retrospective is also subject to a lot of different kinds of error. So what do we do? I don't know. >> It's interesting because I actually thought this past week in might be like more of a U-shaped curve like. Because you have more it like try the extremities like maybe some people exercise a lot like, five to six times. And then some other people like didn't exercise at all because the weather like it definitely like is my left. >> Yeah, yeah. >> I need to, >> Absolutely, yeah. >> So could you ask both questions and particular the average? >> Yeah, or you could examine them independently or examine them simultaneously you could, absolutely. That would be one way to overcome this. I want to introduce it to you all so that you understand some of the measurement flaws inherent in the existing surveys. So each of the you know, the behavior of a spectre survey and others ask physical activity in different ways. So for example, this these are drawn from other larger scale surveys and my memory is failing me for exactly which ones. I believe it's the behavioral risk factors survey. But these are some that are taken to identify health recommendations as well. And so when we're asking about typical or past week, but I mean the point is we're going to get different results. And so we need to think about this as researchers and in those and as people consuming the research the way that we ask is going to come out with a very different pattern of results and potentially recommendations. And so I want you to always kind of have that in the back of your mind when you're analyzing and reading the research on physical activity. That it's important to actually see exactly what it is for talking about typical actual and so on. And to recognize there's going to be a significant amount of noise when you're relying upon self-report to understand these variables. This is the behavioral risk factor survey. So the behavioral risk factor survey also talks about non planned exercise. So now it gets a little bit more into the either active living or physical activity lifestyle physical activity. And considers that it should be distinct from profession because there are some professions that by very definition, requires a significant amount of physical activity. And then they also asked about strengthening as well which not all the surveys do. They only ask about exercise and leave that to the interpretation of the person. I also want to talk a little bit or to introduce people to the measurement and how its reduced to kilocalories which is more broadly known as the calorie. It's actually kilocalorie because different research provides the physical activity measure in different ways. And so they might either talk about minutes, kilocalorie, expenditure. And so this is all done based on what is considered to be an average or typical person. So it just sort of, for one person a block is going to be 56 calories expended. For another person is going to be a very different number. They just take, this is the rough guideline that we have to do for conversion of number of blocks walked or number of stairs climbed. It's a little bit frustrating for people who are more empirically minded. Who recognize automatically, there's no way that's accurate for everyone, but you just hope that the noise bounces out and this is the way it's done. And so this is another example of what is understood with respect to the average person or for beginners at a you know. This is roughly the range of calories that we would expect to be expended for walking a mile. So you can see a fairly significant range particularly when we get to the more intensive forms of physical activity. Okay, the golden is also a measure that you'll see a lot in physical activity research. And you can see here that this measure is also looking at identifying mild moderate and strenuous exercise. And also trying to quantify the number of times that one's engaging in any regular physical activity. So this is asking both a typical seven-day period with respect to either 15-minute increments at different levels. And then also trying to just get a never rarely or sometimes or never sometimes or often. And this is something that you see a lot but obviously looking even at this you can see where there would be a lot of measurement error potentially. But this is one that you will see a lot in the research. Confused yet, overwhelmed? >> The little funny exercises snowmobiling and horseshoes. >> Yeah. >> I don't know, the last time. >> Yeah shoes that's you know, I took out I had some some lovely memes about Badminton and stuff and then I decided you know, I'll lay off the memes for a minute but [LAUGH] not forever. Just okay better measurement with the, fortunately now we're getting into technology has afforded really in the past 15 years or so. A lot better measurement and much more efficiently. So earlier in two decades ago trying to equip someone with an accelerometer wasn't very expensive ordeal. Now, Fitbits and the technologies available to kind of continuously measure physical activity has afforded much more precision. So these are much more objective but they are also subject to error. I mean anybody who's had a Fitbit knows that it kind of like fritz out from time to time. But the correlations here are are pretty good, you know 0.7 is actually a relatively decent correlation. So and so they measure that they've got a good amount of precision in relation to more objective measures. And so objective measures of physical activity are considered like cardiovascular fitness measures actually like, you know oxygen expired in those kinds of things. Where we can take somebody in a lab and put them like in the metabolic chamber and actually get an idea of their physical fitness. Which can be more precisely quantified and just so you know and just likely obvious. The self-report questionnaires have much lower correlation coefficients in relation to the objective measures.