I think utilising clean pools is obviously very
easy to administer, especially in a competition
environment. You just have to stick the weights
on. And also it's biomechanical similarity to
what you're about to do on the platform is pretty
high, right? So I think its use is warranted.
However, you have to be aware it might have positive
effects on some individuals, but it can also
have some negative effects. All right. Welcome
to Evidence Strong Show, Sham. It's my pleasure
to have you for the third time. First person
ever to achieve that. And today we are talking
post -activation potentiation. But before we
start, could you please briefly introduce yourself?
Firstly, thank you very much for having me on
for the hat trick, Alex. Very much appreciated.
So my name is Sham Chavda. I'm the program lead
at Middlesex University London Sport Institute
for the Masters of Strength and Conditioning
Distance Education. I also work as the lead performance
scientist and coach at British Weightlifting.
Excellent. We will be talking about your latest
paper. So the title is Effect of Post -Activation
Potentiation on Weightlifting Performance and
Endocrinological Responses. So let's start with
what post -activation potentiation is in the
context of Olympic weightlifting. Yeah, sure.
So post -activation potentiation is essentially
using conditioning stimulus that helps elicit
greater neural drive and force output in a specific
muscle fiber and actually probably more recently
the terminology has changed and it is probably
a reflection i have on this paper is the term
of post -activation performance enhancement so
pape as opposed to pat so in the instance of
weightlifting we were looking at utilizing a
conditioning stimulants that may help us elicit
greater forces and power output during a weightlifting
movement so specifically we wanted to understand
And if a supramaximal clean pull at 120 % of
someone's 1RM clean would impact the force and
barbell mechanics of a clean performed at 90%.
And also whether that 120 % clean pull would
alter any endocrinological responses as heavy
loading has also been posited to acutely increase
things like serum testosterone, which may enhance
the force production of an individual. How did
you design the study? So this study was a collaborative
study with our biomedical team over at Middlesex
and primarily was conducted by two excellent
MSE students, you know, a little while ago now,
one of them being Dr. Angela Sorensen, of course,
who you've had on the podcast before, fantastic
coach and researcher. So essentially the way
we set this up, it was a randomized controlled
experiment involving eight ranked collegiate
weightlifters and they attended two separate.
testing days, of course, with the order session
randomized. So in both sessions, we standardized
the Walmart, which was essentially clean related
barbell Walmart, followed by working up to 80
% of 1RM clean performance, performing three
reps at each load. And these were clustered by
around 30 seconds between reps and two to three
minutes between sets. So very typical kind of
session type. warmup as you would expect in training.
So the two sessions we had, one of them was a
control and the other was the experimental session.
So in the control session, following the warmup,
the athletes performed three clean lifts at 90
% of one RM with one minute between each repetition.
And this session allowed us to establish like
a baseline. measurement for ground reaction forces
of the clean, as well as the barbell mechanic
measured by integrated force plates and motion
capture. And it also allowed us to obtain baseline
endocrinological status via saliva samples. On
the experimental session, they'd come in, they'd
do their normal warmup up to that 80%, but then
following that 80%, they performed clean pools.
So they performed the clean pools doing a single
repetition at 100 to 120 % of one RM. This was
followed by a three minute recovery period. So
the condition stimulus was 120 % at one hour
in clean pool. The timeframe following that was
three minutes. And then they conducted three
repetitions at 90 % on the force plates with
the motion capture. And in both cases, during
the control and the experimental, we took the
saliva samples before the warmup and 15 minutes
after the last clean performance. Who did you
invite to the study? It was a very... very small
sample that we used so arguably it was quite
underpowered to be very open and transparent
but the level were regional to national weightlifters
but when you look at the subject statistics you
can see the spread is quite large particularly
with relative strength and also half being male
half being female so i think the relative strength
spread was cleaning between one to one and a
half times body weight which relative to other
studies that i've published and other people
have published is probably on the the lower end
of the relative strength ratio right quickly
going back to only using eight participants it
becomes very difficult in our where where we're
based to get a higher sample size of people who
are familiar with Declean. But what it did allow
us to do, and I think this is really important,
it allowed us to take a step forward to try and
analyze individuals and discuss that a little
bit more. And I think that becomes even more
important, particularly when looking at responses
within weightlifting and weightlifters, because
it is an individual sport. And when you look
at some of the potentiating research, it also
suggests that there often is an individual response
that we need to look out for. So I think that
was a nice opportunity to try and discuss and
exploit. What did you measure? Our biomedical
team, they... obtain testosterone and cortisol
and the ratio between the two using saliva collective
via swabs and or the kinetic measures so the
ground reaction forces we used force plates where
we extracted vertical peak force as well as the
impulse of waiting one which is essentially the
first pool the unweighting phase which typically
refers to the transition and then waiting two
which typically refers to the second pool and
this is vertical ground reaction forces and along
that we had synchronized some motion capture
to it so we could get some barbell information
as well and from that we extracted vertical peak
barbell height and we looked at that as a ratio
to the height of the actual athlete so Did they
pull the bar higher, essentially? And we also
looked at peak power of the barbell as well.
So was there an ability to transfer all those
ground reaction forces into the barbell following
the conditioning stimulus? The strong points
are that you went with the clean quite high.
90 % cleans are hard, even for weightlifters
to execute. And you had force plates and motion
capture, which are state -of -the -art tools
to really look at what is going on in terms of
forces during the movement. So let's... That's
awesome. The minus would be low sample size.
Yeah, of course. And I also think maybe the strength,
the relative strengths within the group as well,
I think was probably too widespread. What have
you found? Yep. So ultimately the group findings
suggested there wasn't any difference between
the control and the experimental, which is a
shame because we always hope to find something.
But what we did notice is that there were definitely
subject specific responses, meaning some. Some
did see positive changes, i .e. there was an
increase in impulse and impede force, but also
some showed some negative changes, meaning that
impulse and force actually reduced. And I think
that goes back... to what i mentioned earlier
around the advantage of looking at individual
responses is it's quite important and quite nice
particularly within an individual sport but when
we try to understand why we had these results
i think it comes down to a number of multiple
factors which i think is important to try and
outline so the first one i think is to do with
the time frame following the conditioning activity
of 120 clean pool so we use three minute now
potentially that might might be too short to
create a meaningful change across the board but
there was a reason why we chose three minutes
which we cover in the paper and that tends to
be your last warm -up lift prior to going on
the platform in a competition, would probably
be around two to three minutes before you step
out for your first lift. There has been some
evidence that has suggested three minutes between
clean attempts is actually more beneficial for
enhancing force production. So we decided to
go with that shortest timeframe of three minutes.
But also if you think from a tactical perspective,
if you have a group of athletes clustered together
and there are changes occurring on the board...
pushing your athlete later and later down the
line in terms of getting on the platform, then
maybe three minutes is probably about right.
And of course, there's far more we can discuss
around timings and future research moving forward.
So we utilised three minutes and that could be
too short. And the influence this can have on
the outcome is that during a heavy conditioning
stimulus, the central nervous system recruits
high threshold motor units, primarily type 2
muscle fibres, for increasing rate coding. and
this is what allows us to develop that high amount
of force right but if the time after the conditioning
activity is too short then of course fatigue
is going to kick in which will then lead to a
reduction in rate coding reduce my unit recruitment
and ultimately a decrement in the athlete's ability
to produce force so getting the timing is critical
to utilize a heightened central nervous system
potentiation but of course it is and then you're
going to get a reduction in performance so it
could be that the time frame was too short and
future research may want to look at time frames
which are slightly longer and you know we see
that in some of our results where some people
did respond positively some people didn't but
as a group there wasn't any real significant
difference i wanted to ask whether you found
any differences between female and male athletes
yeah so i think so it wasn't something we looked
at directly but what i did look at in a little
bit more detail after the after the publication
and even during the process was actually whether
the strength level would affect the outcomes
and our that back into male and female as well
and the reason we didn't compare male and female
although we could have again it's you're comparing
four against four so the conclusion we get from
that probably isn't very generalizable right
but when we looked at stronger individuals they
tended to show us well stronger individuals overall
are able to exhibit higher contraction capabilities
and produce more force right and because of that
they're more likely to elicit central and peripheral
fatigue because of the absolute loading and the
absolute forces that they're producing so this
increased fatigue might mask any potentiation
especially if you're using a three minute time
frame so they might need longer to recover right
with a weaker individual they're not going to
be producing as much. as much force and the absolute
loads they're lifting is going to be less even
the relative loads going to be less as well of
course but they may also have lower type 2 fiber
type composition they'll have reduced neuromuscular
efficiency and lower motor unit recruitment so
they actually might need less time between the
conditioning activity and the the performance
measure so maybe three minutes would be okay
in this instance but i think if if we look at
this in a broader perspective our results show
that the strongest male so coming back around
to comparing men and female the strongest male
had the most positive effect as well as the strongest
female so when we looked at individuals and how
they responded because i wanted to use this to
implement with some of my lifters the strongest
male strongest relative male had the most positive
changes across all those measures strongest female
also had the most positive changes across the
measures and when we look when i kind of rank
how each in individual based on their relative
strength responded the females seemed to have
followed a pattern that I kind of expected so
the strongest one had the most response the next
one was the second strongest and then third and
fourth were just flipped over so the the fourth
strongest or the weakest female actually had
the third most positive responses compared to
the third strongest but when we look at the males
it was very random so the strongest male had
the most responses and then after that it was
no responses. Then after that, it was lots of
responses. And after that, it was no responses.
So it kind of explains why we had an overall
finding of no differences between the control
and the experiment. But when you take a bit of
a deeper dive into the information, it does give
us a little bit more of an idea around the potential
of the effect of strength and also potentially
how that distributes itself within males and
females. Would you have any comments about endocrinological
responses? Yeah. So the idea behind this was
that it's been positive that having increased
serum testosterone increases your force output,
but also doing high intensity activities. can
also alter your testosterone cortisol ratio so
if it's too intense then of course your cortisol
is going to start to kick up right and the thought
was well will this conditioning activity keep
our hormonal status either unchanged or will
it positively influence it and be a potential
factor as to why we might be able to produce
more force or not so that's the reason we kind
of went into it And unfortunately, nothing came
out of that. There wasn't anything we could really,
really discuss on the testosterone and cortisol
side other than we didn't, or the conditioning
activity didn't seem to alter it. All right,
so let's bring it all... together. So for the
coaches, what they should take out of the study?
So I think utilizing clean pools is obviously,
it's very easy to administer, especially in a
competition environment. You just have to stick
the weights on. And also it's biomechanical similarity
to what you're about to do on the platform is
pretty high, right? So I think it's use. is warranted
however you have to be aware it might have positive
effects on some individuals but it can also have
some negative effects so i think it's important
to understand what your athlete is used to or
what they prefer during times where tactically
the board starts to change so you need to make
a decision do they do a reduced load and do a
power variant which would also be incredibly
interesting to to study and look at a potential
whether that potentiates to go on the platform
um or do they like to do a pull instead which
in that case you can look at varying intensities
to see where an athlete is able to keep their
keep or maintain their performance or maybe even
optimize it so it is very individualized based
off our findings again that supports that narrative
of it is individualized if it works for some
but they don't like doing a heavy clean pool
and they prefer doing a lighter power clean you're
probably not going to sell to them do 120 clean
pool before you go out on the three minutes before
you go out on the platform it's probably not
a good sell right so i think it certainly depends
on what the athlete and coach kind of agree on
and whether it they find a utility in it or not
but i think The bigger thing to take into consideration
is regardless of the negative effects that the
clean pool had on some of the lifters, they still
all managed to clean the weight. So actually
the outcome was still the same. It's just that
they didn't produce as much force. So they actually
did it with less, less force production and in
more of a negative and more fatigued state. So
you do wonder if you were to go heavier than
90%, would that then, would that... impact the
actual outcome of the performance measure which
is making a successful lift and in the context
of weightlifting that's what matters so irrespective
of on my peak force went down of who cares you
made the lift and that That is quite important
from a scientific perspective. When we're trying
to find these nuances to optimize performance,
of course, this absolutely matters. And I think
maybe coaches might want to try and experiment
within their own environment, maybe using things
like measuring velocity, for example, if they
don't have access to force plates. Last two questions.
The first one is one piece of wisdom from you
as an expert to all the coaches. Oh, I definitely
wouldn't call myself an expert. but I will keep
striving towards that. So I think if I could
pass on one piece of wisdom. I think people should
stay curious and where possible, test your hunches
and your hypothesis because curiosity means,
you know, we're keen to develop and we want to
better understand our practices. And I think
that's really important to understand the why
behind what we do. And don't be afraid to be
challenged on your thoughts and practices as
well, as often or not, that's where kind of growth
occurs. And as coaches, practitioners, as scientists,
I believe that's where... we should be kind of
placing ourselves in a place of what do we need
to understand or what don't i understand and
how can i develop my understanding of that area
because then we grow as a scientific community
to then be able to share you know great information
and we can pick and choose what works in our
own environments because at the end of the day
we don't just do what we do because we enjoy
it but it's also because we want to get the best
out of our athletes so being challenged on our
practices and following up on our curiosities
means not only do we develop but also it means
as a proxy our athletes will benefit from it
as well. Awesome. Thank you. Last question is
where people can find you if they want to ask
a question or follow your work, where should
they go? Yeah, sure. So people can catch me on
socials or via email. My email is s .chavda at
mdx .ac .uk. And my socials are shy underscore
the number two. tweet uh that's for x um and
instagram is coach underscore chavda right sham
thank you so much for today and for for the last
three years oh yeah thank you very much for the
the hat trick opportunity very much appreciate
it and i think you're you're doing a great job
with uh disseminating some really useful information
out there with these great practitioners and
scientists that you've had on the podcast so
so thank you thank you sham cheers