If you download the app on your phone, as of
right now, it's still free to use. You just have
to follow these instructions, place your phone
in a stable stand, film your lift, and you get
really accurate mean velocity measurements. If
you want more advanced measurements, like peak
velocity and stuff like that, really accurate
advanced measurements, it's probably worth investing
in some technology like a linear position transducer
or whatever. but just as an entry point i think
these apps are an excellent excellent option
Hi, Alex. It's my pleasure to have you on Evidence
Strong Show. If you could briefly introduce yourself.
Yes, of course. My name is Alexander Renner.
I'm a powerlifter and employee and student at
the University of Vienna. I'm working in the
field of velocity -based training, and that's
also why I'm here today. Awesome. So we'll be
talking about your recent study, Concurrent Validity
of Novel Smartphone -Based Apps Monitoring Barber
Velocity in Powerlifting Exercises. So I read
the study. I included the study in the research
news show I do every month. So I'm excited to
learn more. We talked a little bit before the
camera started rolling. So I'm excited to hear
first why you did the study and then how you
went about it and what you found. Well, the reason
I did the study was I knew that there were multiple
apps on the market for measuring bubble velocity.
And I have to say, me personally, I was a critic.
I didn't really believe that these apps would
be really... accurate so we decided to take a
look at how accurate these apps are able to measure
the bubble velocity during lifting but one thing
that was really important to me is not just look
at the absolute accuracy like how big are the
measurement errors but how accurate are they
compared to established technology because with
every measurement system there's always going
to be some measurement error so the question
is not is there a measurement error the question
is how big is the measurement error so what we
did is we tested three apps metric vbt quick
vbt and my lift my lift is currently in the app
my jump lab so depending on how you name it it's
a different name but for just for reference i'm
going to say my lift and we tested three these
three apps and compared them to a linear transducer
uh rep one so what we did is we had the bicon
system so the 3d motion capture is the gold standard
And we let athletes lift and then we looked,
okay, how accurate are these apps? How accurate
is the linear transducer? And how do they match
up? So I think we should also mention that all
the measurements were performed at the same time.
So each rep was measured via Viacom, linear transducer
Rep1 and three smartphone applications. Yes,
we had 20 study participants and all of them
performed increasing. load protocol where they
started with they all did single repetition sets
and they started with think it was around 50
and they did 10 single repetition sets in the
squat bench press and deadlift increasing in
intensity so the bubble it's not always just
the same velocity but the bubble also slows down
i will talk about this later but it becomes very
relevant because like sticking points and stuff
where the bubble slows down are only is after
a certain intensity and they did the squat bench
press and a deadlift for each 10 sets with one
repetition each so what was the highest intensity
roughly the athletes when they didn't max out
so they didn't know a hundred percent but how
heavy did they go the highest intensity was defined
as 90 percent of the recent competition maximum
right so around 90 percent yes and what we measured
was we measured the mean concentric barbell velocity
we didn't did not look at the peak velocity because
for the powerlifting exercises the mean velocity
is the generator parameter of choice for olympic
weightlifting might be different for olympic
weightlifting it's usually peak velocity and
what we found is that out of the three apps quick
vvt performed exceptionally well metric vvt was
i would say somewhere in the middle where depending
on the exercise it was more accurate or less
accurate but not as accurate as the linear transducer
whereas quick was and my lift was out of the
three apps the worst, because first of all, it
wasn't that accurate, but also it had a lot of
missed repetitions, especially in the bench press.
And that's also what I would like to talk about
next, because with every velocity measurement,
there are two parts to the measurement, regardless
of the technology. You have the first part of
the measurement, which is just generating the
raw positional data. So how far did the bar travel?
In what... time and then from there you can calculate
the velocity and you have to look at these two
parts separately because with the first part
that's a technology thing like which technology
are you using to generate the raw positional
data with a linear transducer it's a cable pulled
out of a box so it's usually generally it depends
on the exact device but generally it's quite
good data it's quite accurate because you have
something physical pulling it out with the apps
it's I cannot say this for certain because all
these apps are closed, not open sourced. So I
cannot look into them, but I can say with pretty
high confidence that all three of those apps
are using the plate, a standardized plate, 450
millimeters as a reference point. So then they
take the video and they know how big the plate
is. So by knowing how big the plate is, they
can calculate how far the bar traveled and they
have the time in the video. So then they can
calculate. That is the velocity. And that's how
you get the raw positional data. And there's
also differences in how well these apps did that.
But for example, the second point, the rep detection
and the velocity calculation. There are basically
two thresholds which you need to consider. The
first threshold is in order for the app to detect
the repetition. There need to be two thresholds.
The first one is a certain... velocity threshold
because in theory if the bubble would move at
0 .01 meters per second for the whole repetition
it would be so slow that no repetition would
be counted if you depending on which threshold
threshold you choose but if you if you set it
really really low the repetition will be counted
really fast but you might include some other
movement which is not the repetition itself in
the calculation skewing your measurements. But
if you send the velocity threshold too high,
you might have the problem that during sticking
points or so, when you go under this velocity
threshold for rep detection, the rep might be
cut off and the second rep starts once you pass
the sticking point or in general, once you, for
example, in a deadlift, if the lockout is pretty
slow, you might cut off the repetition before
it actually ends, thereby altering the result.
So the first threshold, which you have to be
very careful when considering. is the velocity
threshold for rep detection. The second threshold
you need for rep detection is a certain distance
threshold. Because if you have just, let's say,
a one centimeter threshold for rep detection,
you're going to have the problem that every minor
movement just walking the bar out of the squat
rack is going to detect like 20 repetitions.
So you need threshold for also a distance threshold
for rep detection. And this is... again i cannot
say this with certainty i have looked at the
data and that's just my guess my educated guess
so but that's for example where i think that
the many missed repetitions from the bench press
for the bench press from my lift come from because
we looked at it and i personally think that my
lift has this threshold for repetition detection
at 30 centimeters everything below 30 centimeters
it doesn't detect a repetition and everything
over it detects as a repetition and we as i said
we had experienced powerlifters with quite a
big bench arch with with trying to reduce the
range of motion so they had a lot of them had
a bar path below 30 centimeters for the bench
press so my my lift didn't detect the repetitions
but then on the that's like if you have a really
high distance threshold then there is no rep
detection for like small repetitions but on the
other side if you have a really low threshold
for the distance you run into problems with ghost
repetitions because for example that's something
we had with my lift my lift we had one study
participant where with almost every bench press
repetition with this lift off or just lifting
it out of the rack he had none with all of them
but with many of them he had a ghost repetition
from the lift off with metric because metric
on the other side on the other hand i don't have
an estimate for where their threshold is but
show it seems to be a quite lower so then you
run into those problems so you have to look at
the two things the raw positional data general
like how you generate the raw positional data
and then how what you do with this data at two
separate tasks and with the velocity measurement
via these apps have some limitations in how you
generate the data but then what you do with this
data It doesn't like it. There's no limitation
because that's where all the technologies, even
the linear transducers are working with the same
thing. And I think just without even changing
how they generate the positional data, these
apps could optimize what they are measuring just
by fine tuning their thresholds. Do you think
that the quality of the camera with the application
will influence how good the data is? Yes and
no. So the biggest limitation. of the apps is
the camera as you said because in theory with
the with a perfect high resolution ultra high
frames per second camera these measurements would
be almost perfect because physically there is
no disturbance but again in a real world scenario
there are a lot of co -founders which which influence
these measurements and the biggest limitation
of these apps are frames per second which is
for mean velocity it's not that big of a deal
because you look at the whole repetition but
for peak velocity it matters quite a lot so that's
also why some of these apps don't even really
offer peak velocity as a measurement and so for
the smartphones if you take the default setting
it's 30 frames per second but you can turn it
up all the way to 60 frames per second and with
30 frames per second peak velocity measurement
is accurate to somewhere around 0 .7 to 0 .8
meters per second. And with 60 frames per second,
it's accurate to somewhere around 1 .2, 1 .3
meters per second peak velocity. Again, this
is not published data. This is just what we found
through pre -study testing. And these are the
limitations of the apps because you would have
to develop an own camera for higher frames per
second because this is all the iPhones offer.
You cannot film with more than, actually, I think
with the ultra slow -mo, but that's also what
the developers told me, like for these apps,
you're limited by like a maximum of 60 frames
per second. And this only works to around 1 .3
meters per second for peak velocity. After that,
it just becomes very inaccurate. Thank you. That's
very useful information. Yeah. So with the study
and everything we just talked about with how
these measurements work and what possible limitations
are and how like the processing from I perform
a repetition to I get the velocity measurement,
like the two steps. First, you need the raw data
and then you have like the rep detection and
stuff work. The question is what now to do with
this information. And I would say based on the
study we did, I think that these apps, these
applications can be great. Great, great entry
point. Because especially for mean velocity,
for powerlifting athletes, for weightlifting
with peak velocity, maybe not that much. But
especially, I mean, Quick performed as good,
if not better, than the linear position transducer.
So Quick for mean velocity is extremely accurate.
So it just reduces the barrier of entry to velocity
-based training. Because if you download the
app on your phone, as of right now, it's still
free to use. you just have to follow these instructions
place your phone in a stable stand film your
lift and you get really accurate mean velocity
measurements if you want more advanced measurements
like peak velocity and stuff like that really
accurate advanced measurements it's probably
worth investing in some technology like a linear
position transducer or whatever but just as an
entry point i think these apps are an excellent
excellent option and especially quick really
delivers accurate measurements for mean velocity
in all those powerlifting exercises and there
is basically zero barrier of entry because it's
a free to use app that's awesome all right so
the camera has to be on the tripod or somehow
somewhat fixed on the side so the plate is visible
from the side angle through the whole repetition
some apps like quick will ask you to select the
plate which seems to be improving the accuracy
and the calculations and some of these apps will
ask you to wait for the outcome so you because
some coaches use bbt technology to cue the athletes
so as they go through the rep they get the feedback
of how fast they are moving but it seems from
what you're saying that with these apps this
is not the case so no it's not with quick it's
not possible with metric and my live it is possible
okay so they will so i would say just like the
increased it seems like the increased speed of
the measurement comes with less accurate accuracy
of the measurement right good to know good to
know yeah i i don't think it's going to stay
like this i think because these apps are constantly
improving because that's one thing you have to
really give my lift credit for that my lift was
the first app to do this and now out of these
three apps i have to say that my lift probably
performed the worst but it was the first app
to do this and you just see like the improvements
from app to app so i think because my lift was
the first one then as the next big player there
was metric then there was quick and you just
see that these apps are constantly improving
and that also the apps itself is improving so
for example metric since we did the study as
far as i know i think also metric released a
new update and and so on so these apps are not
that's also something i wrote in the study these
apps are not like a like frozen in time like
they are they are evolving they are getting better
and stuff and i think like these limitations
with the fast that the faster measurement comes
with less accuracy maybe even in one year this
might not be the case anymore because these apps
are just evolving but the versions of the apps
we looked at in this study there it seemed to
be the case that the two apps which offer the
real -time feedback are less accurate than the
one app that did not offer the real -time feedback.
But in a few years, it might look completely
different. But look at us. We are talking of
the technology that was 10 years ago, was only
available in labs, in scientific laboratories.
And now we are debating which app is better and
for what. If you want quick feedback, Metric
and MyLift are the way to go. If you want accuracy,
it has to be quick. But as you said, it's a snapshot.
This is what we know now. And we will have to
revisit and the phones will get better. And people
use tripods in the gym now to film lifts. It's
not even weird anymore or, you know, rare. Which
is also one advantage of the apps because many
people, at least in the powerlifting community,
already are filming their sets for like technical
evaluation of the sets. Did I perform the exercise
right? And so they already have the footage which
they need. for looking at the velocity so you
don't even need to look and like it's not even
an extra step or an extra effort because they
already have the footage they need i could also
talk a little bit more about the bench press
if you want because the bench press is different
than the squat and the deadlift in the respect
that for the bench press the linear position
transducer was less accurate than the than for
the squat and the deadlift. And again, to say
this with certainty, there would be, there would
need to be a second study, but I took a deeper
look at the data beyond what was published in
the study. And it seems like that for the squat
and the deadlift, the center of mass needs to
stay, not now as for those studies, but always,
the center of mass needs to stay above the surface
of support. So your center of mass. cannot move
beyond your foot because then you will fall over.
With the bench press, since you're laying down,
this is not the case. The bench press, you can
have a lot more horizontal movement than in the
squat and the deadlift because you're laying
down, your base of support is quite big. So you
can have more horizontal barbell movement than
compared to the deadlift and the squat. So you
also have more horizontal barbell movement and
linear position transducer since it's the cable
attached to the barbell is not. in my theory
is not able to perfectly differentiate between
horizontal and vertical movement whereas the
eps and also the bicon system is able to perfectly
differentiate between the horizontal and vertical
movement so that's also one thing because we
had a slight overestimation bias with the linear
position transducer in the study for the bench
press that's also something to keep in mind that
depending on which lift you perform how much
horizontal movement there is are different technologies
also have advantages or disadvantages your advice
for coaches who are excited to use vbt to play
with it what they should consider with when choosing
setting up and then looking at the data and using
it Well, my recommendation would be if you haven't
used VBT yet to just try it out. See if it works
for you, if you gain valuable insight for it.
Because with these apps nowadays, the barrier
of entry is so extremely low. As we discussed
in length, QuickVBT is a really accurate app
for measuring mean velocity. So just download
it, try it out. Make sure you follow the... instructions,
how the app is supposed to use, because if you
follow these instructions or not, will greatly
affect the accuracy of these apps. And if you
find that VBT is something you really want to
use in your training and to look at it more accurately,
then maybe down the road, maybe buy some velocity
-based technology like a linear position transducer.
But just for starting out, an app like QuickVBT
is more than enough. Sounds good. Awesome. Two
short questions to finish. The first one is,
what is your favorite lift? Well, my favorite
lift, it always sounds stupid. It's the total.
The power lift with me, the only thing that...
Yeah, the total and the pacing. That's awesome.
Okay, I will let you pass with it. That's very
funny. Okay, where people can find you if they
want to follow your work and your journey? Well,
depending on what you're looking for. I think
for just the research point of things, it's ResearchGate,
Alexander Renner. And if you're also interested...
in my personal lifting it's alex .renner .lifting
on instagram because there on my on the instagram
account it's quite a mixture of the research
stuff and the lifting stuff itself so depending
on what you're looking for these are the two
places awesome thank you so much alex it was
a pleasure thank you