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Jump height is a poor indicator of lower limb maximal power output: theoretical demonstration, experimental evidence and practical solutions

Authors:

Abstract

KEY POINTS 1. Despite a widespread use, we contended that jump height as measured during vertical jump tests is not a good indicator of lower limb power or maximal power output capability. 2. We showed this based on several confounding factors: body mass, push-off distance, individual force-velocity profile and optimal force-velocity profile. Some experimental data were also shown and discussed to further illustrate the not very-good correlation between jump height and power output. 3. Finally, in order to address this issue, we discussed the possible practical solutions, and advocate for the use of a simple, accurate computation method based on jump height as an input.
Morin&et&al.&Pre-Print&–&2018&–&Jump&height&is&a&poor&indicator&of&lower&limb&maximal&power&output&
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OPINION!PAPER!
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JUMP!HEIGHT!IS!A!POOR!INDICATOR!OF!LOWER!LIMB!MAXIMAL!POWER!OUTPUT:!!
THEORETICAL!DEMONSTRATION,!EXPERIMENTAL!EVIDENCE!AND!PRACTICAL!SOLUTIONS!
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Jean-Benoit!Morin1,3,!Pedro!Jiménez-Reyes2,!Matt!Brughelli3,!Pierre!Samozino4!
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1!Université!Côte!d’Azur,!LAMHESS,!Nice,!France!
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2!Faculty!of!Physical!Sciences!and!Sport,!Catholic!University!of!San!Antonio,!Murcia,!Spain!
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3!Sports!Performance!Research!Institute!New!Zealand,!Auckland!University!of!Technology,!
Auckland,!New!Zealand!
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4!Univ!Savoie!Mont!Blanc,!Laboratoire!Interuniversitaire!de!Biologie!de!la!Motricité,!EA!7424,!F-
73000!Chambéry,!France!
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Corresponding!author!
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Pr!Jean-Benoit!Morin!
Faculty!of!Sport!Science!
261!Boulevard!du!Mercantour!
06205!NICE,!France!
Tel:!0033489153956!
Email:!jean-benoit.morin@unice.fr!
Web:!jbmorin.net!
Twitter:!@jb_morin!
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All authors have approved this manuscript and agree with the fact that it is shared as a pre-print
DOI: 10.31236/osf.io/6nxyu
Cite as:
Morin, J., Jiménez-Reyes, P., Brughelli, M., & Samozino, P. (2018, September 4). Jump height is a
poor indicator of lower limb maximal power output: theoretical demonstration, experimental
evidence and practical solutions. https://doi.org/10.31236/osf.io/6nxyu
Morin&et&al.&Pre-Print&–&2018&–&Jump&height&is&a&poor&indicator&of&lower&limb&maximal&power&output&
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KEY$POINTS$
$
1. Despite!a!widespread! use,! we!contended!that! jump! height!as!measured! during! vertical!
jump! tests! is! not! a! good! indicator! of! lower! limb! power! or! maximal! power! output!
capability.!
!
2. We! showed! this! based! on! several! confounding! factors:! body! mass,! push-off! distance,!
individual! force-velocity! profile! and! optimal! force-velocity! profile.! Some! experimental!
data!were!also! shown!and!discussed! to! further!illustrate!the! not! very-good!correlation!
between!jump!height!and!power!output.!
!
!
3. Finally,!in!order!to!address!this!issue,!we!discussed!the!possible!practical!solutions,!and!
advocate!for!the!use!of!a!simple,!accurate!computation!method!based!on!jump!height!as!
an!input.!
!
$
$
ABSTRACT$
!
Lower!limb!maximal!power!output!(Pmax)!is!a!key!physical!component!of!performance!in!many!
sports.!During!squat!jump! (SJ)! and! countermovement!jump!(CMJ)!tests,!athletes!produce!high!
amounts!of!mechanical!work!over!a!short!duration!to!displace!their!body!mass!(i.e.!the!dimension!
of!mechanical! power).!Thus,! jump! height! has! been! frequently! used! by! the!sports! science!and!
medicine!communities!as!an!indicator!of!Pmax.!However,!in!this!article,!we!contended!that!SJ!and!
CMJ!height!are!in!fact!poor!indicators!of!Pmax!in!trained!populations.!!
To!support! our!opinion,!we!first!detailed!why,!theoretically,!jump!height!and!Pmax!are!not! fully!
related.!Specifically,!we!demonstrated!that!individual!body!mass,!distance!of!push-off,!optimal!
loading!and!force-velocity!characteristics!confound!the!jump!height-Pmax!relationship.!!
We!also!discussed!the!poor!relationship!between!SJ!or!CMJ!height!and!Pmax!measured!with!a!force!
plate!based!on!data!reported!in!the!literature,!which!added!to!our!own!experimental!evidence.!
Finally,!we!discussed!the!limitations!of!existing!practical!solutions!(regression-based!estimation!
equations!and!allometric!scaling),!and!advocated!using!a! valid,! reliable!and! simple! field-based!
procedure! to! compute! individual!Pmax!directly! from! jump! height,! body! mass! and! push-off!
distance.!The!latter!may!allow!researchers!and!practitioners!to!reduce!bias!in!their!assessment!
of!Pmax!by!using!jump!height!as!an!input!with!a!simple!yet!accurate!computation!method,!and!not!
as!the!first/only!variable!of!interest.!
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Morin&et&al.&Pre-Print&–&2018&–&Jump&height&is&a&poor&indicator&of&lower&limb&maximal&power&output&
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1. INTRODUCTION+
!
Vertical!jump!tests!such!as!the!squat!jump!(SJ)!and!countermovement!jump!(CMJ)!have!been!long!
and!widely!used!to!assess!an!athlete’s!lower!limb!ballistic!performance!and!indirectly!quantify!
their!mechanical!power!output!capability,!i.e.!the!ability!to!produce!mechanical!work!over!the!
duration! of! the! push-off![13].! Although! measuring! technologies! have! differed! over! the! past!
century,!vertical!jump!tests!are!still!very!popular!due!to!their!simple!and!easy!implementation,!
good! reproducibility! and! time-energy! saving! feature! [4].! The! main! metric! used! to! describe!
jumping!performance!is!maximal!height!after!the!athlete!leaves!the!ground.!For!these!reasons,!
vertical!jump!tests!have!been!popularized!with!classic!testing!batteries!and!procedures![13,5,6].!
Since!maximal!power!output!(Pmax)!is!a!key!physical!component!of!performance!in!many!sports,!
and!because!vertical!jumps!like!SJ!and!CMJ!require!athletes!to!produce!mechanical!(potential)!
work!over!a!short!duration!to!displace!their!body!mass!(i.e.!the!dimension!of!mechanical!power),!
jump!height!is!frequently!used!as!an!indicator!of!Pmax![3].!For!example,!in!a!recent!survey!about!
strength! and! conditioning! practice! in!elite! rugby! union! [4],! the! authors! report! that! the! most!
commonly!used!test!of!muscular!power!was!maximum!CMJ!height.!
In!this!article,!we!contend!that!maximum!SJ!and!CMJ!height!are!in!fact!poor!indicators!of!lower!
limb!Pmax!in!trained!populations.!To!support!our!opinion,!we!have!first!detailed!the!theoretical!
reasons! explaining! why! jump! height! and! Pmax!are! not! fully! related.! We! then! provided!
experimental!evidence!of!the!poor!to!very!poor!associations!between!SJ!or!CMJ!height!and!Pmax.!
Finally,!we!detailed!a! simple! and!field-based!procedure!to!accurately!compute! Pmax! from! SJ!or!
CMJ!height!measurements.!The!latter!may!allow!researchers!and!practitioners!to!improve!their!
assessment! of! Pmax,! using! SJ! or! CMJ! height!as! inputs! with! a! simple! yet! accurate! computation!
method![79],!of!which!calculation!spreadsheets!are!freely!available!online!!
(https://www.researchgate.net/publication/320146284_JUMP_FVP_profile_spreadsheet).!
!
!
2. THEORETICAL+DEMONSTRATION+
!
We!detailed!the!three!main!factors!that!account!for!the!discrepancy!between!jump! height! and!
lower! limb! Pmax!in! this! section:!individual! push-off! distance! (hPO),! optimal! loading! (Lopt)! and!
force-velocity!(Fv)!profile.!!
!
2.1. +Push-off+distance+
The!SJ!and!CMJ!motions!require!the!athlete!to!produce!(mainly!with!their!lower!limb!extensor!
muscles)!and!exert!force!onto!the!supporting!ground!during!the!push-off!phase.!This!phase!lasts!
from!the!starting!(SJ)!or!most!downward!(CMJ)!position!classically!set!at!~90°!knee!angle!to!the!
take-off!position!with!fully!extended!lower!limb.!The!distance!over!which!the!lower!limb!extends!
during!the! push-off!phase!(hPO)!thus!represents!the!distance!over!which!muscles!will!generate!
force! and! mechanical! work! [8].! Thus,! it! is! clear! that! two! athletes! with! different! lower! limb!
segment!lengths!(even!for!a!given!same!body!stature)!may!have!very!different!hPO!values!while!
pushing!from!the!90°!starting!position!to!their!extended!limb!take-off!position.!In!turn,!should!
they!have!the!same!maximal!SJ!or!CMJ!height,!they!would!present!different!push-off! distances!
and!times,!leading!to!very!different!levels! of! power! output.!The!athlete!with!a!greater!hPO!will!
also! show,! ceteris* paribus,! a! lower! mechanical! power! output,! and! vice* versa.! The! theoretical!
importance!of!hPO!in!the!SJ!height!performance!equation!has!been!demonstrated!by!Samozino!et!
al.![10]!and!is!not!negligible.!Furthermore,!Markovic!et!al.![11]!showed!that!body!mass!and!CMJ!
depth!(which!is!equivalent!to!hPO)!clearly!confounded!the!relationship! between! muscle! power!
output!and!jumping!performance.!These!authors!also!suggested!that!the!effect!of!hPO!should!be!
controlled!when!interpreting!the!inter-individual!results!of!SJ!or!CMJ!tests.!
Morin&et&al.&Pre-Print&–&2018&–&Jump&height&is&a&poor&indicator&of&lower&limb&maximal&power&output&
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This% crucial% importance% of% hPO%helps% to% explain% the% outstanding% jumping% capability% in% some%
animals%with%muscular%force%outputs%that%are%not%clearly%superior%to%human%athletes%[12].%In%the%
sports%performance%context,%not%taking%into%account%the%effect%of%hPO%on%SJ%or%CMJ%performance%
may%result%in%misleading%interpretations%of%jump%tests%as%predictors%of%power%output,%with%a%bias%
toward% underestimating% the% power% capability% of% an% athlete% with% a% small% hPO%and% conversely%
overestimating%that%of%an%athlete%with%a%great%hPO.%This%issue%may%be%of%particular%importance%in%
young% age% categories% (in% which% variable% hPO% may% be% observed% among% athletes% of% the% same%
chronological%age)% when%using%SJ%or%CMJ%height%as%a% screening-selection%test.%Finally,%hPO%is%not%
only%determined%by%individual%anthropometrical%factors,%but%also,%when%it%is%freely%chosen,%by%the%
self-selected%starting%position%(SJ)%or%countermovement%depth%(CMJ).%The%latter%are%associated%to%
muscle%force-length% properties,%training% history% or% sport% specificities,%which% supports%the% fact%
that%hPO%should%be%carefully%controlled.%
%
2.2. #Optimal#loading#
In%any% type%of% exercise%allowing% maximal%muscular% exertions%(e.g.% throwing,%jumping,% cycling,%
running),% the% loading% conditions% influence% movement%velocity% (following%the% laws%of% motion),%
which%in%turn%influences%power%output,%with%Pmax%achieved%only%in%an%optimal%loading%condition%
(Lopt)%[1315].%For%example,%should%the%external%loading%be%too%heavy%or%too%light,%the%conditions%
would%lead%the%athlete%to%produce%higher%levels%of%force%or%velocity,%respectively,%but%in%both%cases%
this%would%be%associated%with%sub-maximal%levels%of%power%output.%This%is%well%described%by%the%
second%degree%polynomial%relationship%observed%between%movement%velocity%output%and%power%
output%in%various%types%of%exercises%[1620].%%
In%the%specific%context%of%vertical%jumps,%external%loading%influences%the%power%output%[14,15,21]%
and%Pmax%is%only%produced%in%Lopt%conditions.%Thus,%Pmax%is%achieved%by%a%given%individual%in%a%SJ%or%
CMJ%only%if%their%individual%Lopt%is%equal%to%their%body%mass.%This%corresponds%to%the%“maximum%
dynamic% output% hypothesis”% [13,2224].% However,% due% to% individual% neuromuscular%
characteristics,%and%training%history,%some%athletes%have%a%Lopt%that%differs%from%their%own%body%
mass,% and% would% need% either% positive% (additional% load)% or% negative% (assistance,% unloaded%
conditions)%loading%to%jump%with%their%Lopt%[23,25].%%
As%a%conclusion%to%this%section,%it%is%important%to%distinguish%the%power%output%developed%during%
a%maximal%(i.e.%all-out)%single%effort%(e.g.%SJ%or%CMJ)%to%the%maximal%power%output.%Inferring%that%
SJ%or%CMJ%height%is%associated%with%optimal%loading%conditions%(and%thus%Pmax)%is%only%correct%if%
the%individual%athlete%tested%has%their%own%body%mass%as%Lopt,%which%is%a%substantial%assumption.%
#
2.3. #Force-velocity#profile#and#optimal#profile#
Samozino% et% al.% [9,21]%have% clearly% shown,% using% a% theoretical% approach% [10]% confirmed% by%
experimental% evidence% [19,26],% that% SJ% height% was% almost% entirely% explained% by% the% following%
variables:%Pmax,%hPO%and%the%slope%of%the%Fv%profile.%Thus,%added%to%the%previous%section%about%the%
influence% of% hPO,% it% is% clear% that% the% relationship% between% maximal% jump% height% and% Pmax%is%
confounded%by%the%balance%between%the%athletes’%force%and%velocity%capabilities,%as%described%by%
their%Fv% profile.%The%two%implications%shown%by%Samozino%et%al.’s%works%are%that%(i)%for%a% same%
hPO%and%Pmax,% different%levels% of%SJ% height%may% be% achieved% depending% on% the% Fv% profile% of% the%
athletes%and%(ii)%the%theoretical%maximal%SJ%height%for%a%given%individual%(given%their%hPO%and%Pmax)%
is%only%reached% if% the%actual%Fv%profile%is%equal%to%the%calculated%optimal%Fv%profile%(and%in%this%
case,%body%mass%is%the%Lopt)%[8,10,19,26].%In%other%words,%an%athlete%with%an%optimal%Fv%profile%for%
jump%height% will%have% his%own% body%mass% as%Lopt,% and%thus% produce%Pmax% during% vertical%jump%
without%additional%load.%
The% relative% influences% of% hPO,% Pmax% and% Fv% profile% on% SJ% performance% are% summarized% in% the%
following%equation,%that%has%been%validated%experimentally%[19,26]:%
!"#$ %&'()
*+
,-./01)
23*
&45
6 78
"#$9:;<=> 7? 3,-. /01
*
*
%%%%%Eq.1%
Morin&et&al.&Pre-Print&–&2018&–&Jump&height&is&a&poor&indicator&of&lower&limb&maximal&power&output&
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In#this#equation,#hmax#is#the#maximal#possible#SJ#height#reached#with#an#optimal#Fv#profile#SFvopt.#
Note#that#these#demonstrations#have#been#initially#published#using#SJ#as#the#jump#modality,#but#
subsequent#works#by#Jimenez-Reyes#et#al.#have#shown#that#similar#conclusions#could#be#drawn#
for#the#CMJ#modality#[7].##
A#practical#summary#of#the#above-mentioned#theoretical#points#is#that#the#relationship#between#
SJ#or#CMJ#height#is#clearly#confounded#by#individual#anthropometrical#and#physiological#factors#
inherent# to# each# athlete# tested.# Not# taking# these# factors# into# account# may# lead# to# bias# when#
quantifying# Pmax#via# single# jump# tests# without# additional# load,# as# will# be# evidenced# with# the#
following#simulations#(Table#1)#and#the#experimental#measurements#discussed#in#section#3.#
#
3. EXPERIMENTAL-EVIDENCE-
#
To#support#our#point#that#the#relationship#between#SJ#or#CMJ#height#and#lower#limb#Pmax#is#poor#
to#very#poor#with#experimental#evidence,#we#will#first#list#and#discuss#the#published#correlations#
between#these#variables.#Then,#we#will#present#some#experimental#data#we#have#collected.#
Table#2#shows#a#few#examples#limited#to#studies#reporting#jump#height#measurements#and#the#
magnitude# of# their# correlation# to# lower# limb# maximal# power# output# as# measured# with# the#
reference# force# plate# method,# and# expressed# in# Watts.# Independently# from# their# statistical#
significance,#these#correlations#are#of#rather#low#magnitude#to#accurately#estimate#power#output#
and#Pmax#from#jump#height,#on#an#individual#basis.##
-
Table&2.)Pearson’s)correlation)coefficients)and)linear)regression)coefficients)between)jump)height)
and)lower)limb)peak)instantaneous)power)measured)with)force)plates)and)expressed)in)Watts.)The)
population)age)is)displayed)as)an)average)value) or)range)of)values)for)the)group.)SJ:)Squat)Jump.)
CMJ:)Counter)Movement)Jump.))
Reference-
Number-and-Type-of-
subjects-
Type-
of-
Correlation-
Coefficient-and-
Magnitude-
Linear-
Regression-
Coefficient-
Bridgeman#
et# al.# 2016#
[27]#
12#
Males#(25.4#±#3.5#yrs),#
strength#trained#
CMJ#
0.62#-#Large#
0.38#
Young#et#al.#
2011#[28]#
23#
Males#(22.3#±#2.1#yrs),#
elite#Australian#
football#players#
CMJ#
0.41#-#Moderate#
0.17#
Amonette#
et# al.# 2012#
[29]#
415#
Males#(15.7#±#2.8#yrs),#
soccer,#American#
football,#kinesiology#
students#
CMJ#
0.65#-#Large#
0.42#
Markovic#
and# Jaric.#
2007#[30]#
159#
Males#(18-25#yrs),#
physical#education#
students#
SJ#
CMJ#
0.47#-#Moderate#
0.66#-#Large#
0.22#
0.44#
#
#
Although# the# magnitude# of# the# correlation# between# jump# height# and# Pmax# may# be# improved#
through# allometric# scaling# (see# 4.# Practical# solutions),# the# relationship# between# these# two#
variables#is#not#acceptable,#in#our#opinion,#to#accurately#infer#Pmax#from#SJ#or#CMJ#measurements,#
on#an#individual#athlete’s#basis.#Not#to#mention#the#use#of#this#estimation#in#the#context#of#sports#
performance#monitoring#or#athlete’s#screening/selection#process.##
Morin&et&al.&Pre-Print&–&2018&–&Jump&height&is&a&poor&indicator&of&lower&limb&maximal&power&output&
6
Table&1.!Theoretical!simulation!of!the!relative!error!induced!in!squat!jump!power!output!computations!when!not!taking!the!potential!effects!
of!body!mass,!push-off! distance,!force-velocity!profile,!optimal!profile! and!optimal!load!into!account.! Typical!values!for!a!male! athlete!are!
taken!as!reference!(athlete!1)!and!compared!to!other!athletes!showing!the!same!jump!height!in!standard!(no!additional!load)!conditions,!but!
different!values!for!other!mechanical!variables.!Note!that!the!analysis!would!be!similar!for!countermovement!jump.!Athletes!#2,!#3!and!#4!
only!show!one!different!variable!from!athlete!#1,!whereas!athlete!#5!shows!differences!in!all!variables.!In!the!real!world,!an!almost!infinite!
number! of! combinations! and! ranges! is! theoretically! possible! for! different! mechanical! variables! of! importance.! In! the! current! example,! a!
maximal!error!of!38%!has!been!computed!between!two!individuals!showing!the!same!jump!performance!of!27!cm.!Negative!additional!loading!
indicates!an!unloaded!jump!condition!(e.g.!with!assistance!provided!by!elastic!bands).!Note!that!only!one!type!of!change!(increase/decrease)!
has!been!shown!for!each!variable!(for!clarity!reasons),!but!errors!magnitudes!induced!by!opposite!changes!are!similar.!
The!equations!used!to!perform!these!computations!have!been!validated!and!discussed!by!Samozino!et!al.!
[
8,10,19,26
]
.!
Athlete&ID&
and&
comparisons&
Body&
mass&
(kg)&
Push-off&
distance&
hPO&(m)&
Standard&
jump&height&
(no&
additional&
load)&(m)&
Power&
output&
during&the&
standard&
jump&(m)&
Slope&of&the&
Fv&
relationship&
SFv&(in&%&of&
SFvopt)&
Optimal&
load&
(BW)&
Optimal&
additional&
load&(kg)&
Maximal&
power&
output&
Pmax&(W)&
Maximal&
power&
output&
Pmax&
(W/kg)&
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"%%#
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",%%#
"%%#
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",%%#
)%&%#
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!'#
$%#
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"&%%#
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!'#-./010#!"2#345#567839#5:.#"%#A@#;4<./#hGH#8354#6AA4135#;.6>0#54#6#"*&(B#>8CC./.3A.#83#@6I8@6;#D4<./#C4/#5:.#06@.#E1@D#:.89:5#
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!(#
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!(#-./010#!"2#-6/8410#A4@=83658430#4C#5:.#041/A.0#4C#=860#@6?#;.6>#54#6#'$B#>8CC./.3A.#K13>./.058@65843L#83#@6I8@6;#D4<./#415D15#C4/#5:.#06@.#E1@D#:.89:5#
Morin&et&al.&Pre-Print&–&2018&–&Jump&height&is&a&poor&indicator&of&lower&limb&maximal&power&output&
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By#adding#experimental#data#to#illustrate#our#point,#we#have#measured#SJ#or#CMJ#height#and#!max#
values#in#trained#populations#(sprint,# weightlifting#and# elite# rugby#league#competitors)#within#
various# published# and# in-review# research# protocols# [7,31].# Both# jump# height# and# !max#were#
assessed# using# a# force# plate# system,# and# !max# was# determined# as# the# apex# of# the# load-power#
relationship#for#several#loaded#jump#conditions#(see#[19,26]#for#details).#Note#that#most#studies#
cited#in#this#paper#did#not#use#this#approach#to#determine#!max,#but#rather#the#“peak”or#“maximal”#
value#of#instantaneous#power#output#measured#during#a#single#jump.##
It#is#clear#from# this# dataset# (Fig.#1#and#2)#of#trained#to#elite#athletes#(n=90#for#SJ#and#n=68#for#
CMJ)# that# the# correlations# between# !max# and# jump# height# were# not# systematically# very# large#
(r=0.493#to#0.877),# although# improved#(not#for#CMJ# in#sprinters#and#jumpers,# Figure# 2)#when#
normalizing#!max#to#body#mass.#
!
Fig.&1.&"#$$%&'()#*+,-!%'$+#*.+,$/,0%(1%%*,+23'(,4356,7%)87(,'*9,'0+#&3(%,-6'*%&,':/,#$,$%&'();%,(#,
0#9<,5'++, -6'*%&,0:/,5'=)5'&, 6#1%$,#3(63(, )*, 7)87&<>($')*%9, +6$)*(%$+?, 1%)87(&)@(%$+,'*9, $380<,
&%'83%,6&'<%$+,,
!
!
!
Fig.&2.&"#$$%&'()#*+,-!%'$+#*.+,$/,0%(1%%*,A#3*(%$5#;%5%*(,4356,7%)87(,'*9,'0+#&3(%,-6'*%&, ':/,
#$,$%&'();%,(#,0#9<,5'++,-6'*%&,0:/,5'=)5'&,6#1%$,#3(63(,)*,7)87&<>($')*%9,+6$)*(%$+,'*9,4356%$+:,,
!
!
Morin&et&al.&Pre-Print&–&2018&–&Jump&height&is&a&poor&indicator&of&lower&limb&maximal&power&output&
7
Furthermore,*the*corresponding*low*regression*coefficients*(overall*r2*<*0.56)*show*that*a*large*
part*of*the*variance*in*Pmax*is*not*directly*explained*by*the*variance*in*jump*height.*Jump*height*
and*Pmax*are*significantly*correlated,*but*the*magnitude*of*the*correlations*is*not*high*enough*to*
estimate*the*latter*accurately*from*the*former.*In*line*with*the*theoretical*points*listed*above,*
possible*explanations*for*the*relatively*low*correlations*observed*for*the*overall*group*(Fig.*1)*
include:*variable* hPO* values*among*athletes,* heterogeneous*individual*Fv*profiles* and* optimal*
profiles,*and*in*turn*optimal*load*that*differs*from*body*mass*for*some*athletes*(which*was*the*
case*for*most*rugby*players).*
Finally,*two*recent*studies*show*that*athlete’s*absolute*lower*limb*power*output*capability*could*
not*be*appropriately*categorized*or*estimated,*in*most*sports,*from*jump*height*measurements*
[32,33].*Among* the*practical* solutions*to* solve*this* issue,*the* current*authors*propose* to* use*
estimations*based*on*regressions,*and*allometric*scaling*of*raw,*absolute*power*values.*In*the*
next*section* we* will*discuss* these*possibilities* and* their*limitations,* and*support* the* use*of* a*
more*direct,*accurate*and*practical*method*we*recently*validated.*
*
4. PRACTICAL*SOLUTIONS*
*
4.1. Regression-based*estimation*equations**
One*solution*to*better*estimate*Pmax*from*SJ*or*CMJ*measurements*has*been*the*use*of*regression-
based*equations.*Briefly,* a* regression*(usually* linear)* equation*is* generated* from*actual*jump*
height*and*Pmax*measured*with*reference*methods*(e.g.*force*plate)*in*a*set*of*subjects.*Then,*the*
accuracy*of*the*Pmax*values*“predicted”*by*the*equation*(which*inputs*are*often*jump*height*and*
a*few*simple*variables*such*as*body*mass*or*height)*is*assessed*by*comparison*to*those*obtained*
with*the*reference*methods.* Numerous* regression*equations*have*been*published* to* estimate*
Pmax* (e.g.[3439]).* However,* although* practical,* this* estimation* method* has* several* major*
limitations.*The*first*limitation*is*the*lack*of* theoretical* rationale* supporting*the*link*between*
Pmax,* jump* height* and* body* mass,* notably* via* a* simple* weighted* addition*of* the* two* latter*
variables*(see*2.*Theoretical*demonstration).*Another*limitation*of*such*equations*is*that*they*
are* population-dependent,* which* may* lead* to* a* lower* accuracy* for* estimating* power* on* an*
individual*basis.*For*instance,*Quagliarella*et*al.*[40]*performed*a*detailed*comparative*study*of*
several*equations,*and*reported*very*high*error*values*(>50%)*and*concluded*that*the*use*of*Pmax*
estimates,*can* only* be*useful*to*compare*the*performance*of*groups*of*subjects.* Discrepancies*
and*equation-dependant*accuracy*of*prediction*were*also*observed*in*other*comparative*studies*
[8,36,41,42],* making* the* use* of* regression-based* estimates* irrelevant* for* an* individually*
accurate*determination*of*lower*limb*Pmax.*
*
4.2. Allometric*scaling*
Accounting*for*the*potential*influence*of*body*dimensions*(mostly*stature*and*mass)*on*Pmax*as*
estimated*through*SJ*or*CMJ*measurements*can*be*done*by*scaling*the*raw,*absolute*value*of*Pmax*
to*a*power*of*these*body*dimensions*[43,44].*For*instance,*scaling*Pmax*to*body*mass*(SJ)*or*body*
mass* and* countermovement* depth* (CMJ)* at* the* power* 1* resulted* in* markedly* increased*
correlation*coefficients*with*jump*height*[11].*This*led*to*researchers*recommending*the*use*of*
allometric*scaling*to*more*accurately*estimate*Pmax*from*jump*height*[30,32,33].*In*particular,*
Markovic*and*Jaric*[30]*proposed*that*the*most*justified*and*accurate*scaling*was*when*muscle*
power*was*proportional* to* body*mass*raised*to* the* power*of*0.67*(and* even* more*accurately*
0.75*as*discussed*by*these*authors)*to*account*for*the*theory*of*geometric*similarity,*that*states*
that*some*physiological*features*of* mammals* bodies*(e.g.*muscle*physiological*cross-sectional*
area)*are*not*directly*proportional*to*body*mass*[45].**
However,*allometric*scaling*is*a*correction*method*that*is*also*based*on*assumptions,*and*may*
not* apply* correctly* in* heterogeneous* populations,* and/or*in* the* case* of* very* specific* body*
composition*and*especially*skeletal*muscle*mass*as*developed*through*years*of*specific*training*
in*elite*athletes.*Kons*et*al.*recently*showed*that*the*improvement*of*correlations*between*jump*
Morin&et&al.&Pre-Print&–&2018&–&Jump&height&is&a&poor&indicator&of&lower&limb&maximal&power&output&
8
height& and& Pmax& through& allometric& scaling& was& highly& sport-specific&[33].& Interestingly,& Fig.&1&
shows& that& the& correlation& strongly& differs& between& elite& rugby& players& and& other& athletes&
compared&when&normalizing&Pmax&to&body&mass,&leading&to&an&overall&lower&correlation&when&all&
athletes& are& considered.& This& tends,& again,& to& show& that& indirect& methods& (regression-based&
estimates&or&allometric&scaling)&may&not&totally&solve&the&individual&accuracy&issue&discussed&in&
this&article.&To&this&aim,&an&alternative&method&has&been&proposed&10&years&ago&[8],&that&directly&
computes&jumping&power&output&and&Pmax,&based&on&a&biomechanical&model&and&simple&inputs,&
as&described&in&the&following&section.&&
&
4.3. Direct*computation*using*a*simple*field*method*
In&order&to&solve&most&of&the&previously&described&issues&and&provide&a&simple&and&practical&yet&
accurate&way&to&compute&force,&velocity&and&power&output&during&a&SJ&push-off,&Samozino&et&al.&
have& proposed& and& validated& a& computation& method& in& 2008& [8].& This& method,& based& on&
macroscopic&modelling&of&body&mass&displacement&and&the&associated&mechanical&external&work,&
requires&only&body&mass,&hPO&and&jump&height.&The&initial&reliability&and&concurrent&validity&was&
tested&against&reference&force&plate&measurements&[8],&and&was&confirmed&in&subsequent&studies&
from&other&authors,&including&additional&load&conditions&and&application&to&CMJ&[7,46,47].&
In&this&method,&the&mean&power&produced&during&a&jump&was&computed&as:&
! " #$ %
%&'
( ) *%
+&&&&&&&&&Eq.&2&
&
with&m&the&body&mass,&g&the&gravitational&acceleration,&hPO&the&vertical&push-off&distance,&and&h&
the& jump& height.& In& this& work,& jump& height& was& defined& as& the& aerial& distance& covered& by& the&
center&of&mass&between&the&take-off&and&vertical&apex&instants.&
It& has& also& been& confirmed& that& Pmax& can& be& accurately& computed& from& multiple-load& jump&
protocols&as:&
!
,-. "/
01
0
2&&&&&&&&&&&Eq.&3&
&
F0&and&V0&being&the&force&and&velocity-axes&intercepts&of&the&linear&Fv&relationship&obtained&from&
the&multiple-load& measurements&[19].&However,& since&many& human& subjects&(especially& those&
with&no&extensive&force-&or&velocity-oriented&training)&show&a&Pmax&that&is&close&to&their&SJ&power&
output,&Pmax&might&be&correctly&computed&by&using&the&SJ&power&value.&
Like& all& biomechanical& models,& this& method& has& assumptions& and& limitations& that& have& been&
discussed&extensively&elsewhere&[8,21,48].&In&addition,&these&computations&lead&to&mean&values&
during&the&push-off&phase,&as&opposed&to&peak&values&estimated&in& many& studies& (e.g.& [27,49]).&
That&said,&even&if&instantaneous&and&mean&values&may&reasonably&be&assumed&to&be&linked&during&
vertical& jumps,& mean& values& (i.e.& averaged& over& the& whole& movement)& appeared& to& be& more&
representative&of&the&muscular&effort&[9,50].&&
That&being&said,&given&the&reliability&and&external&validity&of&this&equation&to&compute&SJ&and&CMJ&
power& output& (and& also& easy& to& obtain& Pmax),& we& believe& these& limitations& do& not& induce&
meaningful& errors& and& bias,& and& are&largely&outweighed& by& the& possibility& to& simply& and&
practically&calculate&jump&power,&from&jump& height.& This& is&all&the&more&important&since&jump&
height& measurements/estimations& alone& show& some& clear& limitations,& as& discussed& in& the&
previous&sections.&Interestingly,&this&method&has&been&integrated&in&a&very&practical&and&reliable&
[5153]& smartphone& app& (MyJump2),& allowing& cheaper& yet& accurate& computations& of& jump&
height&and&power&output,&from&a&simple&high-speed&video&recording&of&the&jumps.&
&
&
&
&
&
Morin&et&al.&Pre-Print&–&2018&–&Jump&height&is&a&poor&indicator&of&lower&limb&maximal&power&output&
9
!
5. CONCLUSIONS*
Given! (i)! the! several! limitations! of! using! jump! height! measurements! to! accurately! infer! an!
athlete’s! lower! limb! power! output! capabilities,! and! (ii)! the! possibility! to! more! accurately!
calculate!mean!power!output!during!SJ!or!CMJ!based!on!body!mass,!lower!limb!length!and!jump!
height!using! Equation! 2,! we! strongly! recommend! that! sports! performance,! medicine,! and!
research!colleagues!use!the!method!proposed!by!Samozino!et!al.![8,26],!instead!of!the!standard!
measure!of!jump!height!alone.!This!may!lead!to!a!richer!level!of!information,!from!the!very!same!
input!measurements.!
*
ACKNOWLEDGEMENTS*
*
The! authors! wish! to! thank! Dr! Slobodan! Jaric,! who! has! influenced! some! of! the! concepts! and!
thinking! behind! this! work,! through! his! major! contributions! to! the! field,! and! his! friendly!
discussions!and!remarks.!We!were!very!sad!to!learn!that!Dr!Jaric!had!passed!away! during! the!
writing!process!of!this!paper.!
Authors!have!no!source!of!funding!or!conflict!of!interest!to!declare!regarding!this!paper.!
*
*
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Chapter
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Chapter
Training or rehabilitation programs have to induce changes in force(F)- velocity(v)-power(P) capabilities according to both mechanical demands of the targeted task and actual athlete’s muscle capabilities. To determine individual strengths and weaknesses and then individualize strength training modalities, it is essential to know which mechanical capabilities lower limb muscles have to present to maximize ballistic push-off performances. In this chapter, we explore the relationship between the different lower limb muscle mechanical capabilities and ballistic push-off performances. A biomechanical model is presented to bring new insights on the effect of F-v profile on ballistic performances, notably on the existence of an optimal F-v profile. The latter can be accurately determined for each athlete using equations given in this chapter and usual squat jump FvP profile evaluations, including testing using the simple field method presented in Chap. 4. This makes possible the determination of F-v imbalance (towards force or velocity capabilities) and the quantification of the magnitude of the associated force or velocity deficits. These indexes constitute interesting tools to individualize athlete’s training programs aiming to improve athletes’ ballistic performance. These individual programs should focus on increasing lower limb maximal power and/or decreasing force-velocity imbalance. The effectiveness of such an individualized “optimized” training was shown to be greater than a traditional strength training similar for all athletes. This supports the great interest for strength and conditioning coaches, who aim to improve athlete’s ballistic performance, to evaluate FvP profile on each of their athlete and to consider F-v imbalance to design individually training regimen.
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There is limited published research on strength and conditioning (S&C) practices in elite Rugby Union (RU). Information regarding testing batteries and programme design would provide valuable information to both applied practitioners and researchers investigating the influence of training interventions or pre performance strategies. The aim of this study was to detail the current practices of S&C coaches and Sport Scientists working in RU. A questionnaire was developed that comprised 7 sections; personal details, physical testing, strength and power development, concurrent training, flexibility development, unique aspects of the programme and any further relevant information regarding prescribed training programmes. Forty-three (41 male, 2 female; 33.1 +/- 5.3y) of 52 (83%) coaches responded to the questionnaire. The majority of practitioners worked with international level and/or professional RU athletes. All respondents believed strength training benefits RU performance and reported their athletes regularly performed strength training. The clean and back squat were rated the most important prescribed exercises. Forty-one (95%) respondents reported prescribing plyometric exercises and 38 (88%) indicated periodisation strategies were employed. Forty-two (98%) practitioners reported conducting physical testing, with body composition being the most commonly tested phenotype. Thirty-three (77%) practitioners indicated that the potential muted strength development associated with concurrent training was considered when programming and 27 (63%) believed strength prior to aerobic training was more favourable for strength development than vice versa. This research represents the only published survey to date of S&C practices in Northern and Southern hemisphere RU. Copyright (C) 2016 by the National Strength & Conditioning Association.