WEBVTT

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If you download the app on your phone, as of

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right now, it's still free to use. You just have

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to follow these instructions, place your phone

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in a stable stand, film your lift, and you get

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really accurate mean velocity measurements. If

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you want more advanced measurements, like peak

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velocity and stuff like that, really accurate

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advanced measurements, it's probably worth investing

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in some technology like a linear position transducer

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or whatever. but just as an entry point i think

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these apps are an excellent excellent option

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Hi, Alex. It's my pleasure to have you on Evidence

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Strong Show. If you could briefly introduce yourself.

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Yes, of course. My name is Alexander Renner.

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I'm a powerlifter and employee and student at

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the University of Vienna. I'm working in the

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field of velocity -based training, and that's

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also why I'm here today. Awesome. So we'll be

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talking about your recent study, Concurrent Validity

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of Novel Smartphone -Based Apps Monitoring Barber

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Velocity in Powerlifting Exercises. So I read

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the study. I included the study in the research

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news show I do every month. So I'm excited to

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learn more. We talked a little bit before the

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camera started rolling. So I'm excited to hear

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first why you did the study and then how you

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went about it and what you found. Well, the reason

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I did the study was I knew that there were multiple

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apps on the market for measuring bubble velocity.

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And I have to say, me personally, I was a critic.

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I didn't really believe that these apps would

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be really... accurate so we decided to take a

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look at how accurate these apps are able to measure

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the bubble velocity during lifting but one thing

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that was really important to me is not just look

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at the absolute accuracy like how big are the

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measurement errors but how accurate are they

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compared to established technology because with

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every measurement system there's always going

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to be some measurement error so the question

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is not is there a measurement error the question

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is how big is the measurement error so what we

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did is we tested three apps metric vbt quick

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vbt and my lift my lift is currently in the app

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my jump lab so depending on how you name it it's

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a different name but for just for reference i'm

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going to say my lift and we tested three these

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three apps and compared them to a linear transducer

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uh rep one so what we did is we had the bicon

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system so the 3d motion capture is the gold standard

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And we let athletes lift and then we looked,

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okay, how accurate are these apps? How accurate

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is the linear transducer? And how do they match

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up? So I think we should also mention that all

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the measurements were performed at the same time.

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So each rep was measured via Viacom, linear transducer

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Rep1 and three smartphone applications. Yes,

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we had 20 study participants and all of them

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performed increasing. load protocol where they

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started with they all did single repetition sets

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and they started with think it was around 50

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and they did 10 single repetition sets in the

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squat bench press and deadlift increasing in

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intensity so the bubble it's not always just

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the same velocity but the bubble also slows down

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i will talk about this later but it becomes very

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relevant because like sticking points and stuff

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where the bubble slows down are only is after

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a certain intensity and they did the squat bench

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press and a deadlift for each 10 sets with one

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repetition each so what was the highest intensity

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roughly the athletes when they didn't max out

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so they didn't know a hundred percent but how

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heavy did they go the highest intensity was defined

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as 90 percent of the recent competition maximum

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right so around 90 percent yes and what we measured

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was we measured the mean concentric barbell velocity

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we didn't did not look at the peak velocity because

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for the powerlifting exercises the mean velocity

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is the generator parameter of choice for olympic

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weightlifting might be different for olympic

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weightlifting it's usually peak velocity and

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what we found is that out of the three apps quick

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vvt performed exceptionally well metric vvt was

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i would say somewhere in the middle where depending

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on the exercise it was more accurate or less

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accurate but not as accurate as the linear transducer

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whereas quick was and my lift was out of the

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three apps the worst, because first of all, it

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wasn't that accurate, but also it had a lot of

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missed repetitions, especially in the bench press.

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And that's also what I would like to talk about

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next, because with every velocity measurement,

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there are two parts to the measurement, regardless

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of the technology. You have the first part of

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the measurement, which is just generating the

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raw positional data. So how far did the bar travel?

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In what... time and then from there you can calculate

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the velocity and you have to look at these two

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parts separately because with the first part

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that's a technology thing like which technology

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are you using to generate the raw positional

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data with a linear transducer it's a cable pulled

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out of a box so it's usually generally it depends

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on the exact device but generally it's quite

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good data it's quite accurate because you have

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something physical pulling it out with the apps

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it's I cannot say this for certain because all

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these apps are closed, not open sourced. So I

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cannot look into them, but I can say with pretty

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high confidence that all three of those apps

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are using the plate, a standardized plate, 450

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millimeters as a reference point. So then they

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take the video and they know how big the plate

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is. So by knowing how big the plate is, they

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can calculate how far the bar traveled and they

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have the time in the video. So then they can

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calculate. That is the velocity. And that's how

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you get the raw positional data. And there's

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also differences in how well these apps did that.

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But for example, the second point, the rep detection

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and the velocity calculation. There are basically

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two thresholds which you need to consider. The

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first threshold is in order for the app to detect

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the repetition. There need to be two thresholds.

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The first one is a certain... velocity threshold

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because in theory if the bubble would move at

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0 .01 meters per second for the whole repetition

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it would be so slow that no repetition would

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be counted if you depending on which threshold

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threshold you choose but if you if you set it

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really really low the repetition will be counted

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really fast but you might include some other

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movement which is not the repetition itself in

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the calculation skewing your measurements. But

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if you send the velocity threshold too high,

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you might have the problem that during sticking

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points or so, when you go under this velocity

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threshold for rep detection, the rep might be

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cut off and the second rep starts once you pass

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the sticking point or in general, once you, for

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example, in a deadlift, if the lockout is pretty

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slow, you might cut off the repetition before

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it actually ends, thereby altering the result.

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So the first threshold, which you have to be

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very careful when considering. is the velocity

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threshold for rep detection. The second threshold

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you need for rep detection is a certain distance

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threshold. Because if you have just, let's say,

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a one centimeter threshold for rep detection,

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you're going to have the problem that every minor

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movement just walking the bar out of the squat

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rack is going to detect like 20 repetitions.

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So you need threshold for also a distance threshold

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for rep detection. And this is... again i cannot

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say this with certainty i have looked at the

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data and that's just my guess my educated guess

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so but that's for example where i think that

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the many missed repetitions from the bench press

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for the bench press from my lift come from because

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we looked at it and i personally think that my

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lift has this threshold for repetition detection

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at 30 centimeters everything below 30 centimeters

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it doesn't detect a repetition and everything

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over it detects as a repetition and we as i said

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we had experienced powerlifters with quite a

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big bench arch with with trying to reduce the

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range of motion so they had a lot of them had

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a bar path below 30 centimeters for the bench

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press so my my lift didn't detect the repetitions

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but then on the that's like if you have a really

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high distance threshold then there is no rep

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detection for like small repetitions but on the

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other side if you have a really low threshold

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for the distance you run into problems with ghost

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repetitions because for example that's something

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we had with my lift my lift we had one study

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participant where with almost every bench press

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repetition with this lift off or just lifting

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it out of the rack he had none with all of them

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but with many of them he had a ghost repetition

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from the lift off with metric because metric

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on the other side on the other hand i don't have

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an estimate for where their threshold is but

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show it seems to be a quite lower so then you

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run into those problems so you have to look at

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the two things the raw positional data general

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like how you generate the raw positional data

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and then how what you do with this data at two

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separate tasks and with the velocity measurement

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via these apps have some limitations in how you

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generate the data but then what you do with this

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data It doesn't like it. There's no limitation

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because that's where all the technologies, even

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the linear transducers are working with the same

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thing. And I think just without even changing

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how they generate the positional data, these

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apps could optimize what they are measuring just

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by fine tuning their thresholds. Do you think

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that the quality of the camera with the application

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will influence how good the data is? Yes and

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no. So the biggest limitation. of the apps is

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the camera as you said because in theory with

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the with a perfect high resolution ultra high

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frames per second camera these measurements would

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be almost perfect because physically there is

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no disturbance but again in a real world scenario

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there are a lot of co -founders which which influence

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these measurements and the biggest limitation

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of these apps are frames per second which is

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for mean velocity it's not that big of a deal

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because you look at the whole repetition but

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for peak velocity it matters quite a lot so that's

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also why some of these apps don't even really

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offer peak velocity as a measurement and so for

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the smartphones if you take the default setting

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it's 30 frames per second but you can turn it

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up all the way to 60 frames per second and with

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30 frames per second peak velocity measurement

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is accurate to somewhere around 0 .7 to 0 .8

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meters per second. And with 60 frames per second,

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it's accurate to somewhere around 1 .2, 1 .3

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meters per second peak velocity. Again, this

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is not published data. This is just what we found

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through pre -study testing. And these are the

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limitations of the apps because you would have

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to develop an own camera for higher frames per

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second because this is all the iPhones offer.

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You cannot film with more than, actually, I think

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with the ultra slow -mo, but that's also what

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the developers told me, like for these apps,

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you're limited by like a maximum of 60 frames

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per second. And this only works to around 1 .3

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meters per second for peak velocity. After that,

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it just becomes very inaccurate. Thank you. That's

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very useful information. Yeah. So with the study

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and everything we just talked about with how

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these measurements work and what possible limitations

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are and how like the processing from I perform

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a repetition to I get the velocity measurement,

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like the two steps. First, you need the raw data

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and then you have like the rep detection and

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stuff work. The question is what now to do with

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this information. And I would say based on the

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study we did, I think that these apps, these

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applications can be great. Great, great entry

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point. Because especially for mean velocity,

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for powerlifting athletes, for weightlifting

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with peak velocity, maybe not that much. But

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especially, I mean, Quick performed as good,

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if not better, than the linear position transducer.

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So Quick for mean velocity is extremely accurate.

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So it just reduces the barrier of entry to velocity

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-based training. Because if you download the

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app on your phone, as of right now, it's still

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free to use. you just have to follow these instructions

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place your phone in a stable stand film your

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lift and you get really accurate mean velocity

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measurements if you want more advanced measurements

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like peak velocity and stuff like that really

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accurate advanced measurements it's probably

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worth investing in some technology like a linear

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position transducer or whatever but just as an

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entry point i think these apps are an excellent

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excellent option and especially quick really

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delivers accurate measurements for mean velocity

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in all those powerlifting exercises and there

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is basically zero barrier of entry because it's

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a free to use app that's awesome all right so

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the camera has to be on the tripod or somehow

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somewhat fixed on the side so the plate is visible

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from the side angle through the whole repetition

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some apps like quick will ask you to select the

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plate which seems to be improving the accuracy

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and the calculations and some of these apps will

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ask you to wait for the outcome so you because

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some coaches use bbt technology to cue the athletes

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so as they go through the rep they get the feedback

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of how fast they are moving but it seems from

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what you're saying that with these apps this

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is not the case so no it's not with quick it's

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not possible with metric and my live it is possible

00:14:45.580 --> 00:14:48.200
okay so they will so i would say just like the

00:14:48.200 --> 00:14:52.039
increased it seems like the increased speed of

00:14:52.039 --> 00:14:54.980
the measurement comes with less accurate accuracy

00:14:54.980 --> 00:14:57.240
of the measurement right good to know good to

00:14:57.240 --> 00:15:00.080
know yeah i i don't think it's going to stay

00:15:00.080 --> 00:15:03.379
like this i think because these apps are constantly

00:15:03.379 --> 00:15:06.159
improving because that's one thing you have to

00:15:06.159 --> 00:15:09.019
really give my lift credit for that my lift was

00:15:09.019 --> 00:15:12.700
the first app to do this and now out of these

00:15:12.700 --> 00:15:15.200
three apps i have to say that my lift probably

00:15:15.200 --> 00:15:17.899
performed the worst but it was the first app

00:15:17.899 --> 00:15:20.820
to do this and you just see like the improvements

00:15:20.820 --> 00:15:24.019
from app to app so i think because my lift was

00:15:24.019 --> 00:15:26.840
the first one then as the next big player there

00:15:26.840 --> 00:15:29.080
was metric then there was quick and you just

00:15:29.080 --> 00:15:32.019
see that these apps are constantly improving

00:15:32.019 --> 00:15:35.700
and that also the apps itself is improving so

00:15:35.700 --> 00:15:38.299
for example metric since we did the study as

00:15:38.299 --> 00:15:40.159
far as i know i think also metric released a

00:15:40.159 --> 00:15:43.120
new update and and so on so these apps are not

00:15:43.279 --> 00:15:45.519
that's also something i wrote in the study these

00:15:45.519 --> 00:15:48.700
apps are not like a like frozen in time like

00:15:48.700 --> 00:15:51.179
they are they are evolving they are getting better

00:15:51.179 --> 00:15:53.840
and stuff and i think like these limitations

00:15:53.840 --> 00:15:56.799
with the fast that the faster measurement comes

00:15:56.799 --> 00:15:59.940
with less accuracy maybe even in one year this

00:15:59.940 --> 00:16:02.200
might not be the case anymore because these apps

00:16:02.200 --> 00:16:05.500
are just evolving but the versions of the apps

00:16:05.500 --> 00:16:08.559
we looked at in this study there it seemed to

00:16:08.559 --> 00:16:11.059
be the case that the two apps which offer the

00:16:11.059 --> 00:16:13.850
real -time feedback are less accurate than the

00:16:13.850 --> 00:16:16.710
one app that did not offer the real -time feedback.

00:16:16.929 --> 00:16:19.830
But in a few years, it might look completely

00:16:19.830 --> 00:16:22.110
different. But look at us. We are talking of

00:16:22.110 --> 00:16:24.730
the technology that was 10 years ago, was only

00:16:24.730 --> 00:16:27.470
available in labs, in scientific laboratories.

00:16:27.870 --> 00:16:30.950
And now we are debating which app is better and

00:16:30.950 --> 00:16:33.149
for what. If you want quick feedback, Metric

00:16:33.149 --> 00:16:36.750
and MyLift are the way to go. If you want accuracy,

00:16:37.070 --> 00:16:39.470
it has to be quick. But as you said, it's a snapshot.

00:16:39.730 --> 00:16:42.649
This is what we know now. And we will have to

00:16:42.649 --> 00:16:45.750
revisit and the phones will get better. And people

00:16:45.750 --> 00:16:49.049
use tripods in the gym now to film lifts. It's

00:16:49.049 --> 00:16:52.549
not even weird anymore or, you know, rare. Which

00:16:52.549 --> 00:16:56.009
is also one advantage of the apps because many

00:16:56.009 --> 00:16:58.210
people, at least in the powerlifting community,

00:16:58.549 --> 00:17:02.289
already are filming their sets for like technical

00:17:02.289 --> 00:17:05.730
evaluation of the sets. Did I perform the exercise

00:17:05.730 --> 00:17:10.369
right? And so they already have the footage which

00:17:10.369 --> 00:17:13.359
they need. for looking at the velocity so you

00:17:13.359 --> 00:17:16.420
don't even need to look and like it's not even

00:17:16.420 --> 00:17:19.299
an extra step or an extra effort because they

00:17:19.299 --> 00:17:21.839
already have the footage they need i could also

00:17:21.839 --> 00:17:25.019
talk a little bit more about the bench press

00:17:25.019 --> 00:17:28.380
if you want because the bench press is different

00:17:28.380 --> 00:17:32.519
than the squat and the deadlift in the respect

00:17:32.519 --> 00:17:35.740
that for the bench press the linear position

00:17:35.740 --> 00:17:40.599
transducer was less accurate than the than for

00:17:40.599 --> 00:17:44.099
the squat and the deadlift. And again, to say

00:17:44.099 --> 00:17:46.660
this with certainty, there would be, there would

00:17:46.660 --> 00:17:49.579
need to be a second study, but I took a deeper

00:17:49.579 --> 00:17:52.779
look at the data beyond what was published in

00:17:52.779 --> 00:17:56.279
the study. And it seems like that for the squat

00:17:56.279 --> 00:17:59.900
and the deadlift, the center of mass needs to

00:17:59.900 --> 00:18:02.440
stay, not now as for those studies, but always,

00:18:02.539 --> 00:18:06.559
the center of mass needs to stay above the surface

00:18:06.559 --> 00:18:09.910
of support. So your center of mass. cannot move

00:18:09.910 --> 00:18:12.369
beyond your foot because then you will fall over.

00:18:12.509 --> 00:18:14.750
With the bench press, since you're laying down,

00:18:14.950 --> 00:18:17.130
this is not the case. The bench press, you can

00:18:17.130 --> 00:18:20.309
have a lot more horizontal movement than in the

00:18:20.309 --> 00:18:22.410
squat and the deadlift because you're laying

00:18:22.410 --> 00:18:24.990
down, your base of support is quite big. So you

00:18:24.990 --> 00:18:27.410
can have more horizontal barbell movement than

00:18:27.410 --> 00:18:30.589
compared to the deadlift and the squat. So you

00:18:30.589 --> 00:18:33.549
also have more horizontal barbell movement and

00:18:33.549 --> 00:18:36.630
linear position transducer since it's the cable

00:18:36.630 --> 00:18:39.289
attached to the barbell is not. in my theory

00:18:39.289 --> 00:18:43.190
is not able to perfectly differentiate between

00:18:43.190 --> 00:18:46.529
horizontal and vertical movement whereas the

00:18:46.529 --> 00:18:50.150
eps and also the bicon system is able to perfectly

00:18:50.150 --> 00:18:53.589
differentiate between the horizontal and vertical

00:18:53.589 --> 00:18:56.990
movement so that's also one thing because we

00:18:56.990 --> 00:19:00.750
had a slight overestimation bias with the linear

00:19:00.750 --> 00:19:02.710
position transducer in the study for the bench

00:19:02.710 --> 00:19:05.250
press that's also something to keep in mind that

00:19:05.250 --> 00:19:08.430
depending on which lift you perform how much

00:19:08.430 --> 00:19:11.789
horizontal movement there is are different technologies

00:19:11.789 --> 00:19:15.549
also have advantages or disadvantages your advice

00:19:15.549 --> 00:19:19.569
for coaches who are excited to use vbt to play

00:19:19.569 --> 00:19:22.589
with it what they should consider with when choosing

00:19:22.589 --> 00:19:25.930
setting up and then looking at the data and using

00:19:25.930 --> 00:19:30.900
it Well, my recommendation would be if you haven't

00:19:30.900 --> 00:19:36.039
used VBT yet to just try it out. See if it works

00:19:36.039 --> 00:19:38.259
for you, if you gain valuable insight for it.

00:19:38.380 --> 00:19:41.339
Because with these apps nowadays, the barrier

00:19:41.339 --> 00:19:45.180
of entry is so extremely low. As we discussed

00:19:45.180 --> 00:19:49.700
in length, QuickVBT is a really accurate app

00:19:49.700 --> 00:19:53.279
for measuring mean velocity. So just download

00:19:53.279 --> 00:19:56.980
it, try it out. Make sure you follow the... instructions,

00:19:57.140 --> 00:19:59.720
how the app is supposed to use, because if you

00:19:59.720 --> 00:20:02.279
follow these instructions or not, will greatly

00:20:02.279 --> 00:20:05.539
affect the accuracy of these apps. And if you

00:20:05.539 --> 00:20:09.039
find that VBT is something you really want to

00:20:09.039 --> 00:20:12.039
use in your training and to look at it more accurately,

00:20:12.259 --> 00:20:16.680
then maybe down the road, maybe buy some velocity

00:20:16.680 --> 00:20:19.519
-based technology like a linear position transducer.

00:20:19.579 --> 00:20:23.019
But just for starting out, an app like QuickVBT

00:20:23.019 --> 00:20:25.799
is more than enough. Sounds good. Awesome. Two

00:20:25.799 --> 00:20:27.880
short questions to finish. The first one is,

00:20:27.920 --> 00:20:30.099
what is your favorite lift? Well, my favorite

00:20:30.099 --> 00:20:31.940
lift, it always sounds stupid. It's the total.

00:20:32.059 --> 00:20:33.859
The power lift with me, the only thing that...

00:20:33.859 --> 00:20:37.039
Yeah, the total and the pacing. That's awesome.

00:20:37.319 --> 00:20:39.440
Okay, I will let you pass with it. That's very

00:20:39.440 --> 00:20:41.640
funny. Okay, where people can find you if they

00:20:41.640 --> 00:20:44.960
want to follow your work and your journey? Well,

00:20:45.079 --> 00:20:47.359
depending on what you're looking for. I think

00:20:47.359 --> 00:20:51.940
for just the research point of things, it's ResearchGate,

00:20:52.019 --> 00:20:54.859
Alexander Renner. And if you're also interested...

00:20:54.890 --> 00:20:59.109
in my personal lifting it's alex .renner .lifting

00:20:59.109 --> 00:21:01.849
on instagram because there on my on the instagram

00:21:01.849 --> 00:21:04.650
account it's quite a mixture of the research

00:21:04.650 --> 00:21:07.829
stuff and the lifting stuff itself so depending

00:21:07.829 --> 00:21:09.450
on what you're looking for these are the two

00:21:09.450 --> 00:21:11.609
places awesome thank you so much alex it was

00:21:11.609 --> 00:21:12.569
a pleasure thank you