Test what you know. Don't test something unique.
If the athletes are going to be measured in something
make sure it's something they do regularly. Hi,
Marie -Claire. It's my pleasure to have you on
The Evidence Strong Show for the second time.
Please briefly introduce yourself for three people
who haven't seen the first interview. Thanks
for having me. My name is Marie -Claire Jeannot.
I typically go by MC in the sports space. And
I'm currently a postdoctoral researcher at the
University of Victoria in beautiful British Columbia,
Canada. And I just finished my PhD on the classification
of different strength qualities. And I'm also
a strength and conditioning coach. I work with
the Canadian Sport Institute here in Canada,
as well as the Professional Women's Hockey League
here in Vancouver. All right. So huge experience
working in strength and conditioning and doing
research. So I'm super excited to have you and
pick up your brain specifically on your newest
study on countermovement jump and back squat.
So let's start with some kind of definition of
strength and what we should know about strength
before we go dive. deep into the study. Yeah,
that's a great start. And that is actually the
definition of strength is what led us to doing
this study altogether, as well as many other
studies of my PhD. And so for the purpose of
today and what is kind of currently existing
in the literature is strength is an expression
of force on an object or environment. And since
that's a relatively broad term and can be expressed
in many different ways, we have different forms
or different domains or different types of maximal
strength. Do we want to go quickly into the types
so then we can align them with what you did in
your study? Yeah, great. So we can define strength.
And this is what currently kind of has come from
my research through my PhD is there are four
different main types of strength, reactive strength,
light dynamic strength, heavy dynamic strength,
and isometric strength. And within those four
domains, there are subdomains. So for instance,
within isometric strength, we have early isometric
strength. and maximal isometric strength. Within
the dynamic strengths, we have timing, a force,
and an outcome variable. And within reactive
strength, we have timing and outcome variables.
So those subdomains kind of shift depending on
the population that you're assessing, but that's
the general rule of thumb as we come from our
research. So your approach to strength is very
analytical, but also very, very rooted in practice.
So we want to get the athletes strong. But we
also want to test them in a way that doesn't
make them tired, sore and so on, does not pose
a risk of injury, but allows us to kind of guess
that they are getting better, getting stronger
or not. And from my area, which is Olympic weightlifting,
we know that both a counter movement jump and
back squat are correlated with weightlifting
performance and are often used to test whether
the athlete is progressing. the case when we
can't or don't want to test them on Olympic weightlifting
movements. So that's the broader context. Now,
why you study? What were you trying to do and
why? Yeah, I mean, you make some good points
here. One being that we don't always want to
devote an entire training session to testing,
and we don't necessarily want that to be a separate
entity. And we're kind of leaning towards informing
practices of monitoring training and different
tests and different exercises. we can use to
effectively measure those exercises and use that
to track progress. And so you make two really
good examples there of a one rep back squat and
a countermovement jump as proxy measures or measures
of different expressions of strength to understand.
progress and there's a recent trend right now
kind of in practice that we don't necessarily
need all of these tests we want to capture the
range of strength expressions that are available
but we want to do so in the fewest number of
tests that we can and tests that we can also
use for training purposes so if you don't have
a back squat in your you know a heavy heavy you
know one or three rep max back squat in your
program but you have a loaded counter movement
jump in your program Wouldn't it be nice if we
can just measure the loaded countermovement jump
instead of having to do the back squat, but it
would still measure a maximal quality of strength?
So those were the practical scenarios that led
us to this study in particular, as well as some
nuance around, you know, what if we perform that
countermovement jump, that loaded countermovement
jump, sorry, on force plates? Does that tell
us more information? Can we combine it with metrics
from an unloaded countermovement jump that we're
probably doing anyways, or is really low? barrier
exercise to include in a test battery. collectively
does that information tell us enough about the
performance of an athlete that we don't need
the one rep max bass squad? Or do we need it
in order to capture that range of strength? Awesome.
So how did you set up your study? Yeah, so we
had 19 resistance trained males. And what we
did for that recruitment process is tried to
get a nice range of athletes based on their 1RM
performance. They're all resistance trained,
but we essentially had a range of participants
with like 100 kilo bass. squat and those with
200 kilo back squat. So we had a range that helped
with our regression models. And what we did was
a standardized procedure of an unloaded counter
-ribbon jump and an incrementally loaded counter
-ribbon jump, starting at 20 % body mass on the
bar up to 100 % body mass on the bar. And then
after a nice long rest, they each performed a
one rep max back squat to a standard depth. And
so it was cross -sectional in nature. Now, all
of the jumps were performed on force platforms
where Whereas the back squat was not. It was
just performed on a regular setup. And we just
took the maximal values, the maximal kilos of
that water. And now in terms of the measurements,
what did you... Well, obviously, if you use force
plates, anyone who has tried, you can have, I
don't know, 200 to 400 measurements taken. Yeah.
with each jump. So what have you decided to actually
monitor and analyze? Yeah, no, it's a great question
and is important in the process of understanding
this study. So we use previous literature to
understand that there are probably three main
factors or types of strength or types of metrics
that we can use from the counter -movement jump
without over -analyzing or over -including those
metrics. And we took an impulse, so an impulse
from the counter -movement jump, which essentially,
like propulsive of impulse and it is very closely
related to jump height. So if someone was to
use the results from the study, they could probably
sub in jump height for that particular metric.
We also took timing. Yes, go ahead. Could we
just define the impulse? Yes. So it is the force
produced over time in the concentric or propulsive
phase of the countermovement. So if you actually
take the eccentric impulse, it actually cancels
itself out when you go through the unweighing
and the braking phase. So if you look at a total
impulse in a countermovement jump, it actually
equates to the propulsive aspect of that action.
So that's the pushing upwards from the braking
to when you leave the ground. over time that
you produce in that section of the jump is what
we measured. And that is directly proportional
to jump height as a lot of the jump height equations.
And consider the most appropriate equation used
to generate jump height from a force plate is
the impulse momentum method. So it uses that
impulse to calculate jump height. So they're
very closely related. Another metric that we
used was timing of the jumps. We used eccentric
duration as it was the more, had the most variance
across participants. And that was used as a time.
factor of the counter -moving jump. We also used
force. So some people call it kind of the driver
aspect of a counter -moving jump, but essentially
we used net propulsive force as another unique
factor for the counter -moving jump. So those
were the three main domains of strength that
we had Netrix represented from the counter -moving
jumps that we used in the regression models,
both in the unloaded and each of the loaded tasks.
And the kilograms for the back squat. And kilos
for the back squat, yes. A secondary aim was
looking... at the intact waveforms. Right. Okay,
great. So this one is a little bit more complicated,
but I'm hoping it'll make sense. So a secondary
aim of this study was to investigate the changes
in force patterning between the loaded jump conditions.
So with the practical scenario of, you know,
if we are faced with a situation where the metrics
from any of the loaded jumps contribute to the
same amount of explained variance, you know,
one rep backs basketball or kind of, you know,
we consider it to represent a similar expression
of strength. Therefore, maybe we can choose any
of the loaded jump conditions that are more suitable
for our athletes. We wanted to provide the practitioner
with some information on how different those
loaded jumps were so that we can start to decide
which one we want to use for training and end
testing that best matches our sport or training
demands. And so one approach to this question
was to look at the intact waveform. So that is
the non broken down force time curve, and seeing
if there are statistical differences between
the intact the whole jump over time. Now we did
something called time normalized the the curves.
So let's say there was a 20 % countermovement
jump and and then a 40 % body weight countermovement
jump. If the jump was just slowed down, so that
is the exact same force patterning everything
was just a little bit slower which is something
that we hypothesized, then the curves would look
exactly the same if they were time normalized.
What we found though, is that when we did time
normalize the curves, there were different strategies
involved with performing that jump. So those
who, even with the addition of 20 % of body mass,
there were changes in the way athletes were unloading
and loading onto the bar in order to jump as
high as they could. Now we did use non -standardized
jump depth, which I think in future... research
it would be beneficial to see if these changes
did exist with a standardized depth, but we did
this intentionally to see how people were able
to, you know, maximally express force in a countermovement
jump under different loads and how that changes
their force patterning. So moving backwards to
the actual analysis that we did, we took the
intact waveforms, we normalized them so they
all lasted in a total of one second. And then
we ran the curves through something called a
statistical parametric mapping. And it is essentially
a statistical... approach that looks for differences
in the absolute force production at each instance
along the curve. So if it's one second, that's
1 ,000 indices. It looked at every one of those
1 ,000 indices and looked for a statistical difference
between the different conditions. And in that
analysis, we noticed that there were specific
trends, particularly around tow -off, so the
takeoff portion of the jump, that was most impacted
by an increase in load. So when you look at the...
actual curves, you can see some dark red kind
of in the ANOVA that was run. And that is an
indication that there were significant differences
in the absolute force at the end time of that
curve. One of our main outcomes of this particular
portion of the study was that each curve was
different. And there were actually some weird
changes that happened around the heavier loads.
So between the 80 % and the 100 % body mass condition,
we found that strategy was changed quite a bit
in a sense where maybe the athletes that we had
in the study weren't super accustomed to maximally
expressing force under the condition of 100 %
body mass jump. So that led us to some understanding
of, okay, the athletes have to know how to perform
the task quite well in order for us to use it
as a performance measure. Just while listening,
what did it mean that the athletes adjust their
strategy and how they perform can the movement
jump right at the end? So everything at the beginning
that... The dip, let's say, go ahead, is pretty
similar. And then where they're supposed to go
up, that's where everything changes. At the beginning,
so with the small loading of weight, that seemed
to be the most impacted section was at the toe
off. But as a little bit more weight was added,
the breaking portion was also greatly affected.
And that wasn't super surprising because the
extra load of that weight in the breaking and
the... rate of force and total force that you
have to develop in that segment should theoretically
change unless you are really, really, really
strong in that position. But interestingly, yeah,
the toe -off was a little bit more affected by
smaller amounts than the eccentric loading in
this population. Right. What else? What else
have you found? So with the regression models,
so we took those three metrics from each of the
counter movement jumps and to understand the
shared variance essentially between the load.
counter -moving jumps and the one rep max, we
used multiple regression models. And what we
found were, first of all, both timing and force.
So timing and force in the countermovement had
very, very little influence on one rep max performance,
meaning that those who are good at each of those
aspects of the countermovement were not necessarily
good at one rep maxes. But the impulse, so as
I mentioned earlier, the impulse is greatly associated
with jump height. So that actually had a strong
correlation to one rep max backspin and contributed
most to the regression models. And we found that...
there was a range from about 30 % shared variance
to 66 % shared variance. So in the 80 % body
mass countermovement jump that the jump height
or the impulse measured from that condition explained
up to 66 % of variance in the one round ex -bass
squat. So that leaves a good chunk of variance
that's unexplained. And so that kind of led us
to the conclusion that, yeah, okay, there is
definitely some similarity here, but we can't
fully replace the... one rep max back squat if
that particular strength characteristics is important
to you we cannot fully replace it just by using
metrics from the loaded countermovement jump
we also found that combining both an unloaded
countermovement jump impulse and an impulse from
another loaded countermovement jump did not improve
the model performance at all and the reason we
did this was you're likely going to do an unloaded
countermovement jump anyways in a strength assessment
because it's super accessible most people can
do it it's almost included in warmup, so why
not include it in our models to see if it helps
the performance? It did not. So overall, we found
that the loaded counter movement jumps were pretty
similar to the unloaded. So you could kind of
pick and choose what you wanted there. Whereas
the one rep max back squat was a pretty unique
factor. And so overall, we suggest that you choose
either an unloaded counter movement or a loaded
counter movement if it's more specific to your
sport and a one rep max back squat in order to
capture the range of information available from.
the dynamic tasks from that range from unloaded
countermovement jump to a maximal dynamic load,
which we would consider to be a one rep max.
All right. I may have missed it. The heaviest
countermovement jump were the most similar to
back squat, but still not enough to replace it.
Oh yeah. This is actually a good point. We actually
found that the, so we did countermovement jumps
up to 100 % body mass, but we found that the
100 % body mass condition actually had lower
relation. or lower shared variance to when we're
at max back performance than the 80 % condition.
And we hypothesized or tried to explain that
as, you know, we don't think that the athletes
included in this study were super comfortable
with the 100 % body weight condition. And that
could have led to maximal expression of force
not to be optimized in that condition. So they
weren't super accustomed to it. And so performing
that task didn't necessarily allow that. to have
a maximal expression of force. It was more just
figuring out how to do the movement and move
under that load. And so that lends to our larger
discussions when we're selecting one test over
the other, which is make sure that your athletes
or your participants or whatnot know how to perform
the task prior to using it for monitoring or
testing purposes. It also lends us more to the
discussion around selecting a task that you would
do anyways in the weight room or as part of your
training, because chances are the athlete knows
how to perform that over some unique tasks that
you only use for monitoring or testing purposes.
So overall, that was one of the major conclusions
as well. You know, something that came from our
research is that it's almost not sports specific,
a lot of these things, but who your strength
and conditioning coach is, what kind of tests
and what kind of exercises you do with your strength
and conditioning coach might be more. more indicative
of how well you're trained for different exercises,
not necessarily your sport. With that said, though,
there are, you know, specific trends. You wouldn't
necessarily have a super heavy countermovement
jump in sports that don't involve moving other
mass, you know? So yeah, it would be sports specific.
And I think these results can still help decisions
in those cohorts where it is maybe only up to
50 % body. mass that you're doing a loaded counter
-driven jump, but you prefer doing that over
a one rep max back squat, you now know that you
can adequately predict or predict up to 60 %
of that variance using a slightly lighter load.
You don't necessarily need to go all the way
up to 100 % or the benefit of going from 40 %
to 80 % is only 3 % or whatever it is of more
explained variance. So you can maybe make better
decisions around there as well. Right, right.
That's very useful because you can consider safety.
specificity to your athlete day, training age,
what you're normally doing, you know, all these
factors you can factor in while you're making
decisions on training. Yeah, exactly. And that's
what we wanted to do with this paper and our
other papers is not say that, you know, this
weight is better than the other, but rather provide
the information of, you know, when you are selecting
this load based off of the laundry list of other
factors that you're making this decision off
of, this is what you're compromising, or this
is, you know, one of the factors in the equation.
and it helps us just make better decisions in
the training environment and in testing environment.
Right. Okay. Could we then bring it all together
and produce some kind of takeaways for... the
coaches on how to use the data from a study.
Yeah. So overall, I think we wanted to help coaches
decide how many different strength tests and
different strength metrics they needed for the
range of an unloaded countermovement all the
way up to a one rep max back squat. And what
we showed in this study is that the three main
metrics from a countermovement jump, so that
being a timing, an outcome, and a force metric
need to be measured through a counter -movement
jump variant and a one rep max back squat is
needed in order to count for the range. We can't
necessarily miss one or two of those in order
to count for the whole range. Additionally, we
might not need a loaded counter -movement jump.
The combination of an unloaded counter -movement
jump and one rep max back squat does a pretty
good job of collecting the range, at least in
recreational individuals, and further research
is needed to explore. or whether that's the case
in more trained individuals. Awesome. And usually
I finish with two short questions. And today
I will ask you to, maybe you are an expert in
strength. So what is one nugget of knowledge
you want all the coaches to know about strength?
The biggest thing I would say, and I'm going
to lean on the strength testing side, is test
what you know. Don't test something unique. If
the athletes are going to be measured in something,
make sure it's something they do right. regularly.
Awesome. And last question is where people can
find you online if they want to keep up with
your research or ask a question. Yeah. ResearchGate
is a great place for most of my research and
Google Scholar. And I've boycotted the Twitter
space. So I'm more on Instagram these days. And
that's where I'll post some papers and post some
summaries of research coming out. Thank you so
much, MC. A pleasure as usual. All the best for
all the next projects. Thank you very much. Thanks
for having me on