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An age-adap ed plyome ic exe cise p og am imp o es dynamic s eng h, jump
pe o mance and unc ional capaci y in olde men ei he simila ly o mo e han
adi ional esis ance aining
© 2020 Van Roie e al.
Published e sion
Van Roie, E elien; Walke , Simon; Van D iessche, S ijn; Delabas i a, Tijs;
Vanwanseele, Benedic e; Delecluse, Ch is ophe
Van Roie, E., Walke , S., Van D iessche, S., Delabas i a, T., Vanwanseele, B., & Delecluse, C.
(2020). An age-adap ed plyome ic exe cise p og am imp o es dynamic s eng h, jump
pe o mance and unc ional capaci y in olde men ei he simila ly o mo e han adi ional
esis ance aining. PLoS ONE, 15(8), A icle e0237921.
h ps://doi.o g/10.1371/jou nal.pone.0237921
2020
RESEARCH ARTICLE
An age-adap ed plyome ic exe cise p og am
imp o es dynamic s eng h, jump
pe o mance and unc ional capaci y in olde
men ei he simila ly o mo e han adi ional
esis ance aining
E elien Van RoieID
1
*, Simon Walke ID
2
, S ijn Van D iessche
1
, Tijs Delabas i a
3
,
Benedic e Vanwanseele
3
, Ch is ophe Delecluse
1
1Physical Ac i i y, Spo s and Heal h Resea ch G oup, Depa men o Mo emen Sciences, KU Leu en,
Leu en, Belgium, 2Neu omuscula Resea ch Cen e , Facul y o Spo and Heal h Sciences, Uni e si y o
Jy a
¨skyla
¨, Jy a
¨skyla
¨, Finland, 3Human Mo emen Biomechanics Resea ch G oup, Depa men o
Mo emen Sciences, KU Leu en, Leu en, Belgium
*e elien. an oie@kuleu en.be
Abs ac
Powe declines a a g ea e a e du ing ageing and is mo e ele an o unc ional de e io a-
ion han ei he loss o maximum s eng h o muscle mass. Human mo emen ypically con-
sis s o s e ch-sho ening cycle ac ion. The e o e, plyome ic exe cises, using an eccen ic
phase quickly ollowed by a concen ic phase o op imize powe p oduc ion, should esem-
ble daily unc ion mo e han adi ional esis ance aining, which p ima ily builds o ce p o-
duc ion capaci y in gene al. Howe e , i is unclea whe he olde adul s can sus ain such
high-impac aining. This s udy compa ed he e ec s o plyome ic exe cise (PLYO) on
powe , o ce p oduc ion, jump and unc ional pe o mance o adi ional esis ance aining
(RT) and walking (WALK) in olde men. Impo an ly, easibili y was in es iga ed. Fo y men
(69.5 ±3.9 yea s) we e andomized o 12-weeks o PLYO (N = 14), RT (N = 12) o WALK (N
= 14). Leg p ess one- epe i ion maximum (1-RM), leg-ex enso isome ic maximum olun-
a y con ac ion (MVC) and a e o o ce de elopmen (RFD), jump and unc ional pe o -
mance we e e alua ed p e- and pos -in e en ion. One subjec in RT (low back pain) and
h ee in PLYO (2 muscle s ains, 1 knee pain) d opped ou . Adhe ence o (91.2 ±4.4%) and
accep abili y o (�7/10) PLYO was high. 1-RM imp o ed mo e in RT (25.0 ±10.0%) and
PLYO (23.0 ±13.6%) han in WALK (2.9 ±13.7%) (p <0.001). PLYO imp o ed mo e on
jump heigh , jump powe , con ac ion ime o jumps and s ai climbing pe o mance com-
pa ed o WALK and/o RT (p <0.05). MVC imp o ed in RT only (p = 0.028) and RFD did no
imp o e (p >0.05). To conclude, PLYO is bene icial o e RT o imp o ing powe , jump and
s ai climbing pe o mance wi hou comp omising gains in s eng h. This o m o aining
seems easible, bu con ains an inhe en highe isk o inju ies, which should be aken in o
accoun when designing p og ams o olde adul s.
PLOS ONE
PLOS ONE | h ps://doi.o g/10.1371/jou nal.pone.0237921 Augus 25, 2020 1 / 22
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OPEN ACCESS
Ci a ion: Van Roie E, Walke S, Van D iessche S,
Delabas i a T, Vanwanseele B, Delecluse C (2020)
An age-adap ed plyome ic exe cise p og am
imp o es dynamic s eng h, jump pe o mance
and unc ional capaci y in olde men ei he simila ly
o mo e han adi ional esis ance aining. PLoS
ONE 15(8): e0237921. h ps://doi.o g/10.1371/
jou nal.pone.0237921
Edi o : Massimo Sacche i, Uni e si a degli S udi di
Roma ’Fo o I alico’, ITALY
Recei ed: Feb ua y 29, 2020
Accep ed: Augus 5, 2020
Published: Augus 25, 2020
Copy igh : ©2020 Van Roie e al. This is an open
access a icle dis ibu ed unde he e ms o he
C ea i e Commons A ibu ion License, which
pe mi s un es ic ed use, dis ibu ion, and
ep oduc ion in any medium, p o ided he o iginal
au ho and sou ce a e c edi ed.
Da a A ailabili y S a emen : All da a iles a e
a ailable a h ps://os .io/ qph4/.
Funding: E. Van Roie holds a senio pos doc o al
ellowship (12Z5720N) unded by he Resea ch
Founda ion Flande s. The unde s had no ole in
s udy design, da a collec ion and analysis, decision
o publish, o p epa a ion o he manusc ip .
Compe ing in e es s: The au ho s ha e decla ed
ha no compe ing in e es s exis .
In oduc ion
Du ing he ageing p ocess, muscle mass, muscle o ce and powe p oduc ion decline p og es-
si ely [1–3]. This decline is mo e p onounced in powe and apid o ce p oduc ion han in
maximal o ce o muscle mass [3,4]. In addi ion, he abili y o gene a e a high amoun o
powe enables indi iduals o pe o m be e on e e yday ac i i ies, such as ising om a chai
and climbing s ai s [5]. In eac i e mo o asks, such as balance eco e y ollowing sudden pe -
u ba ions, muscle o ce needs o be gene a ed in sho ime ames [6]. Consequen ly, educed
lowe -limb powe and slowing o o ce p oduc ion ha e been p oposed as impo an p edic-
o s o age- ela ed de e io a ion in unc ional pe o mance and should be a ge ed in exe cise
p og ams o olde adul s.
Resis ance exe cise has been widely ecognized as an e ec i e s a egy o imp o e muscle
mass, muscle s eng h and unc ional pe o mance in olde adul s. The majo i y o in e en-
ions p esc ibed slow-speed esis ance exe cise wi h 1–4 se s o abou 8–15 epe i ions a mod-
e a e o high loads o a leas 2x/week, in line wi h p e ious in e na ional ecommenda ions
[7]. Al hough he bene i s a e well documen ed, limi ed imp o emen s in powe and a e o
o ce p oduc ion ha e been epo ed when exe cises a e ypically pe o med a slow and con-
olled speeds [8]. As men ioned abo e and suppo ed by ecen insigh s and exe cise guide-
lines, he e a e impo an a gumen s o jus i y he inclusion o explosi e ype o esis ance
exe cise in olde adul s [9,10]. Machine-based esis ance exe cise pe o med wi h an explosi e
concen ic phase ollowed by a con olled, slowe eccen ic phase is easible, e en in ins i u-
ionalized elde ly [11]. This ype o explosi e esis ance exe cise has shown g ea e e ec s on
unc ional pe o mance han adi ional slow-speed esis ance exe cise [12,13].
Howe e , human locomo ion a ely in ol es pu e concen ic mo emen s, bu consis s o
apidly coupled eccen ic-concen ic mul i-join muscle ac ions, known as s e ch-sho ening
cycle (SSC) ac i i ies. Fas eccen ic-concen ic ansi ion in a SSC mo emen acili a es subse-
quen powe gene a ion h ough s o age and eu iliza ion o elas ic ene gy [14]. The e o e,
mul i-join SSC mo emen s ep esen a mechanism behind op imal powe p oduc ion. This is
an impo an a gumen o he use o plyome ic aining, which speci ically a ge s mul i-
join SSC, in olde adul s, especially conside ing ha he u iliza ion o elas ic ene gy becomes
g adually impai ed due o neu al and s uc u al changes in aged muscles [15,16].
Plyome ic aining elici s nume ous posi i e changes in neu al and musculoskele al sys-
ems, muscle unc ion and pe o mance o heal hy indi iduals ( o a e iew, see [17]). How-
e e , his aining modali y has p ima ily been used in a hle es and/o young adul s, while
limi ed esea ch exis s on plyome ic aining o olde adul s [18]. In addi ion, knowledge on
he po en ial ad e se e en s o such high-impac aining is lacking, as pape s o en ail o com-
men on easibili y and inju ies [19].
The e o e, we designed a 12-week mul i-join plyome ic exe cise p og am (PLYO) o
olde men. This p og am was age-adap ed o maximize easibili y by slowly p og essing om
slow speed exe cises o e submaximal o maximal jumps, using only low-in ensi y d ills,
allowing using wall ba s o suppo and in oducing sho b eaks be ween e e y jump. I s
e ec s on muscle s eng h, muscle powe , jump pe o mance and unc ional capaci y we e
compa ed o a adi ional esis ance aining p og am (RT) and a walking p og am (WALK).
The walking g oup was conside ed a con ol g oup, as he exe cise was no likely o imp o e
muscle s eng h o powe , bu did consis o low-load eccen ic-concen ic lowe -limb mo e-
men s ha migh al eady a ec unc ional pe o mance. As a seconda y ou come, he easibil-
i y o he plyome ic exe cise p og am was in es iga ed. We hypo hesized ha PLYO would
imp o e mo e on muscle powe , jump pe o mance and unc ional pe o mance han RT and
WALK and ha he p og am would be easible in heal hy communi y-dwelling olde men.
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Me hods
T ial design
This andomized ial was designed as a pa allel-g oup s udy, wi h h ee di e en exe cise
in e en ions. The in e en ion du a ion was 12 weeks. Ou come measu emen s we e
ob ained a baseline (p e-in e en ion, om Feb ua y o Ma ch 2018) and wi hin one week
a e he las exe cise session (pos -in e en ion, om May o June 2018). The s udy was
app o ed by he Human E hics Commi ee Resea ch UZ/KU Leu en in acco dance wi h he
decla a ion o Helsinki. All subjec s p o ided w i en in o med consen .
Subjec s
Communi y-dwelling olde men aged 65 o 80 yea s we e ec ui ed h ough ad e isemen s in
local newspape s. Exclusion c i e ia we e uns able ca dio ascula disease, neu ological diso -
de s, cogni i e mal unc ioning, se e e knee o hip p oblems, p e ious up u e o he Achilles
endon and sys ema ic engagemen in ( esis ance) exe cise in he 12 mon hs p io o pa icipa-
ion. In o al, 42 men (age: 69.4 ±3.8 yea s, body mass: 82.7 ±10.5 kg, body heigh : 174.8 ±6.4
cm, BMI: 27.1 ±3.2 kg/m
2
) we e ound eligible and ag eed o pa icipa e in he s udy (Fig 1).
Randomiza ion
Subjec s we e andomly assigned o one o h ee in e en ion condi ions by block andomiza-
ion (block size o 3): adi ional esis ance aining (RT, n = 14), plyome ic exe cise (PLYO,
n = 14) o walking (WALK, n = 14). Alloca ion a io was 1:1:1. In RT, wo subjec s we e no
able o pe o m baseline measu emen s because o ecu en headache o muscle inju y so
hey we e excluded om he s udy (Fig 1).
Exe cise p o ocols
Resis ance aining p o ocol. Subjec s exe cised h ee imes weekly on non-consecu i e
days o e a pe iod o 12 weeks ( o al o 36 sessions). Exe cise sessions we e pe o med in small
g oups o maximum ou subjec s and we e supe ised by a leas one expe . Session du a ion
was abou 35 minu es. A e a s anda d 15-minu e wa m-up on a cycle e gome e (Techno-
gym, Bike Exci e) a sel -selec ed esis ance and 70–80 e olu ions pe minu e, h ee exe cises
o he lowe -limb muscles we e pe o med: he bila e al leg p ess and s aigh -legged cal
aises (bo h on he pla e-loaded linea leg p ess, Li e Fi ness Signa u e Se ies) and leg ex ension
(Li e Fi ness Op ima Se ies). These exe cises we e chosen because hey ain he muscles
esponsible o iple ex ension in he lowe -limb (i.e. knee ex enso s, hip ex enso s and plan-
a lexo s), a mul i-join mo emen ha is c ucial in daily li e ac i i ies such as walking and
s ai climbing. T aining a iables and p og ession a e shown in Table 1. Subjec s we e
ins uc ed o pe o m he las se o concen ic ailu e. When hey we e able o pe o m mo e
epe i ions han he p esc ibed aining zone, he load was inc eased in he nex exe cise ses-
sion. The es pe iod be ween se s and exe cises was one minu e and a leas wo minu es,
espec i ely. A he end o he exe cise session, basic s a ic s e ching exe cises we e pe o med
o he ained muscle g oups.
Plyome ic exe cise p o ocol. Simila o RT, aining sessions (35-minu e du a ion) in
PLYO we e pe o med h ee imes weekly on non-consecu i e days o 12 weeks in small
g oups o maximum ou subjec s and supe ised by a leas one expe . The wa m-up con-
sis ed o 10-minu es o cycling, ollowed by plyome ic wa m-up exe cises: 4 x 10m high knee
skips, 4 x 10m sideways skips and 8 consecu i e hops wi h sho con ac imes. The co e p o-
g am simila ly consis ed o h ee exe cises, using he same muscle g oups ( iple ex ension) as
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in RT: wo unila e al exe cises, i.e. o wa d s ep-up (jump) and la e al s ep-up (jump), and one
bila e al exe cise, i.e. coun e mo emen jump. Exe cise in ensi y p og essi ely inc eased e e y
h ee weeks (see Table 1). The es pe iod be ween se s and exe cises was one minu e and a
leas wo minu es, espec i ely, in all aining phases. F om week 1–3, exe cises we e pe -
o med a egula speed wi hou jumping, i.e. ei he s epping up on a box (20-30-40 cm) in o -
wa d o la e al di ec ion o pe o ming a squa (body mass wi h o wi hou weigh es ) wi h
bouncing mo emen a he lowes poin . Weigh es s (5–10 kg) we e only used o he squa
exe cise p io o p og essing o jumping. F om week 4–6, all exe cises p og essed o submaxi-
mal jumping wi h a sho eccen ic phase be o e all jumps (i.e. SSC ac ion) (Fig 2) and weigh
es s we e no longe used as he squa exe cise p og essed o a coun e mo emen jump exe -
cise. Subjec s we e ins uc ed o ha e a sho 5s-b eak be ween he epe i ions o ensu e p ope
pe o mance and o a oid a igue. F om week 7–9, subjec s we e ins uc ed o jump as explo-
si ely and as high as possible in e e y jump, wi h 5s-b eaks be ween he epe i ions. F om
week 10–12, bo h s ep-up jumps we e pe o med consecu i ely (no b eaks be ween
Fig 1. Flowcha o he s udy. PLYO = plyome ic aining; RT = esis ance aining; WALK = walking.
h ps://doi.o g/10.1371/jou nal.pone.0237921.g001
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Table 1. T aining a iables o he esis ance aining (RT) and plyome ic (PLYO) aining p og am.
Se s Repe i ions Ex e nal load B eak be ween epe i ions In e -se es Pe o mance
RT (leg p ess, s aigh -legged cal aise, leg ex ension)
Week 1–4 2 12–15 12-15RM / 1 min. 3s ecc– 3 sec conc
Week 5–8 3 10–12 10-12RM / 1 min. 3s ecc– 3 sec conc
Week 9–12 4 8–10 8-10RM / 1 min. 3s ecc– 3 sec conc
PLYO ( o wa d s ep-up, la e al s ep-up, coun e mo emen jump)
Week 1–3 2 15–20 BM�/ 1 min. Regula speed, no jump
Week 4–6 3 8–12 BM 5s 1 min. Fas ecc–submax. jump
Week 7–9 4 6–8 BM 5s 1 min. Fas ecc–max. jump
Week 10–12 4 6–8 BM / 1 min. Fas ecc–max. jump
�P og ession o in ensi y du ing week 1–3 in PLYO was based on subjec s’ eelings o muscle a igue: o wa d and la e al s ep-up: inc ease in s ep heigh ( o maximum
40 cm); squa : adding weigh es o 5 o 10 kg.
BM = body mass; RM = epe i ion maximum (las se pe o med o concen ic ailu e in RT); ecc = eccen ic.
h ps://doi.o g/10.1371/jou nal.pone.0237921. 001
Fig 2. Visual ep esen a ion o he h ee plyome ic exe cises om week 4 o 6.
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epe i ions, sho con ac imes) and as high as possible. The coun e mo emen jumps we e
p eceded by a wo p e-hops, he second one wi h coun e mo emen o load bo h ankle and
hip/knee join s. In all exe cise phases, subjec s we e allowed o use wall ba s o suppo i
needed and we e ins uc ed o s op he exe cise when eeling unable o pe o m maximally. A
he end o he exe cise session, basic s a ic s e ching exe cises we e pe o med o he ained
muscle g oups.
Walking p o ocol
The walking p og am was adap ed om a 10-week p og essi e indi idualized walking p o-
g am, desc ibed in de ail in p e ious wo k [20], by adding wo addi ional weekly schedules o
comple e a 12-week p og am (see Table 2). B ie ly, subjec s we e assigned o a s a ing le el o
he walking p og am based on he esul s o a 6-minu e walk es a baseline. Each walking
schedule p esc ibed walks o a ce ain numbe o s eps on 3–7 days a week, depending on he
s a ing le el. T aining olume was p og essi ely inc eased weekly o a maximum o walks o
10000 s eps pe o med h ee imes weekly. Subjec s ecei ed hei pe sonalized walking sched-
ule and a pedome e . They we e ins uc ed o walk a a mode a e and com o able pace ha
inc eased b ea hing and hea a e wi hou es ic ing he abili y o alk. Subjec s we e allowed
o pe o m hei walks a home, bu we e encou aged o engage in g oup walks ha we e
Table 2. Walking p og am (p esc ibed numbe o s eps pe day).
le el N day 1 day 2 day 3 day 4 day 5 day 6 day 7 sessions pe week olume pe week
1 1000�� 1000�� 1000�� 1000�� 1000�� 1000�� 1000�� 7 7000
2 1000�1000�1000�1000�1000�1000�1000�7 7000
3 1000 1000 1000 1000 1000 1000 1000 7 7000
4 1500 1000 1500 1000 1500 1000 1500 7 9000
5 1500 1500 1500 1500 1500 1500 1500 7 10500
6 2000 1500 2000 1500 2000 1500 2000 7 12500
7 4 2000 2000 2000 2000 2000 2000 2000 7 14000
8 2500 2000 2500 2500 2000 2500 6 14000
9 1 3000 2000 3000 3000 2000 3000 6 16000
10 2 3000 3000 3000 3000 3000 3000 6 18000
11 2 4000 3000 4000 3000 4 14000
12 5 4000 4000 4000 4000 4 16000
13 4000 4000 4000 4000 4 16000
14 6000 4000 6000 4000 4 20000
15 6000 4000 6000 4000 4 20000
16 8000 4000 6000 4000 4 22000
17 8000 4000 8000 4000 4 24000
18 8000 8000 8000 3 24000
19 8000 6000 10000 3 24000
20 10000 5000 10000 3 25000
21 10000 7000 10000 3 27000
22 10000 10000 10000 3 30000
23 10000 10000 10000 3 30000
�1 es ing b eak allowed,
��2 es ing b eaks allowed.
N ep esen s he numbe o subjec s wi h he espec i e le el as s a ing le el o he p og am. E e y week, subjec s inc eased one le el un il he 12-week in e en ion was
inished.
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p o ided h ee imes weekly a he aining acili y. All subjec s we e asked o documen hei
walk sessions, including he amoun o s eps pe o med, in a dia y. Dia ies we e e iewed by
he esea ch eam when subjec s joined he on-si e g oup walks (on a e age once pe week) o
a leas once e e y wo weeks h ough con ac ia e-mail o elephone.
Ou come measu emen s
Feasibili y. Feasibili y o he exe cise p o ocols we e assessed by he ollowing c i e ia:
ec ui men a e, exe cise session adhe ence, numbe o d op-ou s, accep abili y and ad e se
e en s [21]. Rec ui men a e was calcula ed as he numbe o s udy subjec s di ided by he
o al numbe o indi iduals ha showed an ini ial in e es in s udy pa icipa ion. Adhe ence
a e was calcula ed as he numbe o aining sessions pe o med di ided by he ecommended
aining equency (3x/week o 12 weeks, 36 sessions o PLYO and RT; 3-6x/week o 12
weeks, 41–56 sessions o WALK). Gi en ha subjec s in WALK could po en ially pe o m
mo e sessions han ecommended, which was no he case o PLYO and RT, we addi ionally
co ec ed he adhe ence a e in WALK. Mo e speci ically, he co ec ed adhe ence a e in
WALK was calcula ed by excluding any exe cise sessions abo e he weekly p esc ibed numbe
o exe cise sessions. Fo example, i a subjec pe o med 5 exe cise sessions ins ead o 4 in a
ce ain week, adhe ence was co ec ed o 100% ins ead o 125% o ha week. The numbe o
d op-ou s was eco ded, including he ime o and he eason o d op-ou . All subjec s we e
asked o epo any ad e se e en s du ing he in e en ion.
Accep abili y was e alua ed h ough a sho ques ionnai e comple ed 2-weekly in RT and
PLYO only. The ques ionnai e consis ed o 5 ques ions answe ed on a 11-poin Like scale
( anging om 0 = ‘no a all. . .’ o 10 = ‘ e y. . .’): (1) How much did you enjoy he exe cises
while doing hem? (2) How p oud a e you ha you we e able o comple e hese exe cises? (3)
How con iden a e you ha you will be able o comple e hese exe cises in he nex aining
session? (4) How mo i a ed a e you o comple e hese exe cises in he nex aining session?
(5) How easible do you hink ha hese exe cises a e o people o you age? The i s ou
ques ions we e employed p e iously in simila popula ions [22,23], while ques ion 5 was
added. In week 12, a six h ques ion was added o he ques ionnai e: (6) How likely is i ha
you will engage in simila exe cise p og ams a e he end o he in e en ion? The ques ion-
nai e in week 12 was also p o ided o he subjec s o WALK. In e nal consis ency o he 5-i em
ques ionnai e was good, wi h a C onbach’s αcoe icien o 0.79. The e o e, we calcula ed he
mean o he 5 i ems in o one global scale ep esen ing accep abili y o he in e en ion
p og am.
Leg p ess one- epe i ion maximum. Leg p ess one- epe i ion maximum (1-RM) was
assessed on he pla e loaded linea leg p ess de ice (Li e Fi ness Signa u e Se ies). In acco -
dance wi h p e ious esea ch [22], he assessmen s a ed wi h a s anda dized wa m-up o 8
epe i ions a 50% o he es ima ed 1-RM, ollowed by 5 epe i ions a 70% o he es ima ed
1-RM. A e his wa m-up, single li s wi h p og essi ely hea ie loads we e pe o med un il
ailu e. To s anda dize, hese li s we e pe o med as concen ic li s only, s a ing in a knee
and hip join angle o 90˚ and 65˚ espec i ely ( ull ex ension = 180˚). Res pe iods be ween
wa m-up se s and be ween single a emp s we e 1 o 5 minu es. The hea ies success ul li (in
kg) was de e mined as 1-RM.
Fo ce p oduc ion and jump pe o mance. A sledge appa a us was used o assess leg-
ex enso o ce p oduc ion and jump pe o mance [24]. The inclina ion o he sledge was 20˚
o ho izon al and he sea was inclined backwa ds (130˚). A o ce pla o m was buil in pe pen-
dicula o he jumping di ec ion (Fig 3) and a eloci y senso was a ached o he sea o he
sledge. The o ce pla o m consis ed o ou S s yle load cells (YZC-516, capaci y o 300kg
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each) ha we e a ached o a cus om-buil pla o m. P io o a achmen o he pla o m, each
o he load cells was calib a ed wi h a weigh o 155kg. In addi ion, he pla o m was calib a ed
by measu ing he unloaded condi ion p io o each es . The eloci y senso consis s o a pe -
manen magne DC mo o iding along wi h he sea . A wheel unning on a ail nex o he
sea o he sledge d i es he mo o sha . Tha way he mo o ac s as a gene a o , p oducing a
cu en linea wi h he o a ional eloci y. Calib a ion was done by measu ing he cu en
while unning he wheel a di e en eloci ies. Ro a ional eloci y was measu ed wi h an elec-
onic pulse coun e (HP53131A) coun ing he pulses o a empo a ily added pulse gene a o
on he sha . The cu en was measu ed wi h a high p ecision mul ime e (HP34405A). Linea
eg ession analysis showed a R
2
o 0.9998 be ween cu en and eloci y. The shoulde s and
hips we e s abilized wi h a 4-poin sea bel . Subjec s wo e s anda d la non-cushioning shoes
o minimize he cushioning e ec du ing explosi e mo emen s.
The es p o ocol consis ed o explosi e isome ic olun a y con ac ions, squa jumps (SJ),
coun e mo emen jumps (CMJ), and d op jumps (DJ). P io o all es s, 2 o 4 p ac ice ials
we e allowed. All es s we e pe o med h ee imes. All da a we e elayed o a pc ia an AD
con e e (Mic o 1401, Camb idge Elec onic 180 Design, UK) and eco ded using Signal 4.03
so wa e (Camb idge Elec onic Design, UK). Da a ( ime, o ce and eloci y) we e sampled a
1000Hz and o ce da a we e il e ed using a ou h-o de low-pass Bu e wo h il e wi h a
70Hz cu -o equency. The bes ial (maximal o ce, maximal a e o o ce de elopmen o
highes jump) was used o u he analyses.
Explosi e isome ic mul i-join leg-ex enso con ac ions we e pe o med unila e ally wi h
he igh leg while he sledge was locked in posi ion. The knee join angle was se a 90˚ and
he hip angle a 70˚. The poin o o ce applica ion was aligned wi h he head o he i h me a-
a sal. Subjec s we e ins uc ed o push as as and as ha d as possible and main ain hei maxi-
mum o ce o app oxima ely 3s. The s a o he o ce- ime cu e was de ined as he i s
poin whe e he o ce exceeded body weigh by 3% and whe e he inc ease in o ce a e 50ms
was a leas 50N ( o ensu e he s a o a slope). Maximal o ce (N) was de ined as he highes
mean 500 ms epoch ( olling a e age) o e he o ce- ime cu e. The a e o o ce de elopmen
(N/s) was de ined as he linea slope o he o ce- ime cu e and was measu ed om he onse
o mo emen un il 100 ms (RFD0-100).
In he bila e al SJ, subjec s jumped wi h he sledge as high as possible om a squa ing posi-
ion (90˚ knee lexion and 70˚ hip angle, same posi ion as isome ic es s) wi hou coun e -
mo emen by pe o ming a as upwa d mo emen . I he es leade isually de ec ed a
coun e mo emen , he jump was epea ed. The s a o he jump was de ined as he i s poin
whe e he o ce exceeded body weigh by 3% and he inc ease in eloci y exceeded 0.02 m/s
Fig 3. Sledge appa a us wi h a o ce pla o m buil in pe pendicula o he jumping di ec ion and a speed senso a ached o he sea o he sledge.
Posi ion A ep esen s he lowes posi ion in he isome ic es s and in he squa jumps, posi ion B ep esen s he ligh phase du ing jumps.
h ps://doi.o g/10.1371/jou nal.pone.0237921.g003
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poo o he du a ion o he eccen ic phase in he coun e mo emen jump (0.48), e en hough
CV% was good (9.7%). Howe e , we should keep in mind ha ou eliabili y alues a e based
on a compa ison be ween amilia iza ion and baseline measu emen s. In subjec s ha a e new
o jump es s, we can expec an imp o emen in jump s a egy, i.e. a as e eccen ic ime and/
o as e ansi ion om eccen ic o concen ic mo emen , om amilia iza ion o baseline.
The ICC quan i ies he be ween-subjec a iance in ela ion o he o al a iance, which also
con ains he a iance wi hin subjec s [25]. As he a iance wi hin subjec s will inc ease in case
o a lea ning e ec om amilia iza ion o baseline, a lowe ICC alue will be ob ained, espe-
cially when be ween-subjec di e ences in means a e small. This esul should he e o e be
in e p e ed wi h cau ion and eplica ion in u u e s udies is wa an ed.
Al hough we can only specula e on he unde lying mechanisms behind imp o ed jumping
pe o mance, Ho en-Mikkola e al. [30] demons a ed ha imp o emen s in jumping pe o -
mance a e plyome ic exe cise we e achie ed wi h sho e ope a ing leng hs o he m. gas-
ocnemius and, he e o e, inc eased ascicle s i ness and imp o ed endon u iliza ion [30]. In
addi ion, Pii ainen e al. [24] epo ed no inc ease in muscle ac i i y o he iceps su ae du ing
explosi e isome ic es s a e plyome ic exe cise, sugges ing ha mechanisms o he han
imp o ed olun a y d i e, such as inc eased u iliza ion o elas ic ene gy and/o s e ch e lex
ac i i y, may be esponsible o enhanced jump pe o mance [24]. Wi h ega d o muscle
a chi ec u al changes, 6 weeks o plyome ic aining has been shown o esul in inc eased
muscle hickness, ascicle leng h and penna ion angle, which likely con ibu ed o he obse ed
changes in powe [32].
In he cu en s udy, we did no obse e a signi ican inc ease in leg-ex enso RFD a e
ei he plyome ic o esis ance exe cise. Such null indings should be se in con ex wi h
espec o he body posi ion speci ici y o he es and aining exe cises: a signi ican inc ease
in RFD may be mo e likely i he es is mo e body posi ion-speci ic o i aining is pe o med
wi h he in en o apidly con ac muscles [33]. Al hough RT included dynamic leg p ess
aining and a mul i-join isome ic leg p ess se -up was used o assess RFD, aining was pe -
o med bila e ally while es ing unila e ally. In con as , pa o he aining in PLYO was pe -
o med unila e ally, bu in di e en body posi ions ega ding knee-join angle. We should
howe e no e ha he pe cen change does seem o poin ou an exe cise-induced imp o e-
men in PLYO, bu his imp o emen was no signi ican because o a la ge a iabili y in ain-
ing esponses and small sample size. Coe icien o a ia ion (18.9%) was high, bu ha is qui e
ypical in ea ly phase RFD, e en in young adul s [34]. A longe ime in e al o 0–200 ms was
conside ed (CV o 9.9%), bu as i did no lead o any di e en conclusions, we decided no o
include his in o ma ion in he esul s sec ion o b e i y. In line wi h he esul s on RFD, no
ime-by-g oup in e ac ion e ec was ound o isome ic MVC, al hough RT was he only
g oup ha imp o ed.
To ou knowledge, limi ed epo s exis on changes in 1-RM a e plyome ic exe cise in
olde adul s. Bolam e al. (2016) epo ed no inc ease in leg p ess 1-RM a e 9 mon hs o plyo-
me ic exe cises pe o med a high (40–80 jumps) o mode a e (20–40 jumps) dose 4x/weekly
in middle-aged and olde men. Howe e , hese indings migh ha e been ela ed o he limi ed
adhe ence a es (i.e. 53–65%) [35]. On he con a y, Co ea e al. [36] epo ed simila gains in
knee-ex ension 1-RM a e 6 weeks o plyome ic compa ed o adi ional esis ance exe cise.
Bo h g oups ollowed he same 6-week p og am o gene alized s eng h aining p io o di i-
sion in wo exe cise g oups. Gains in 1-RM om week 6 o 12 we e simila (+20–21%)
be ween g oups [36]. This is in line wi h ou indings, showing ha sho - e m plyome ic
exe cise is able o induce simila gains in leg p ess 1-RM as adi ional esis ance exe cise. This
gain in 1-RM migh be linked o muscle a chi ec u al changes (i.e. inc eased muscle hickness
and penna ion angle) and imp o ed muscle ec ui men , as ound p e iously a e 6 weeks o
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plyome ic aining in olde men [32]. Al hough he long- e m e ec s should be in es iga ed,
hese esul s show ha PLYO is bene icial o e RT o imp o ing muscle powe and jump pe -
o mance wi hou comp omising gains in s eng h, a leas when olde indi iduals begin a
high-in ensi y ( esis ance o plyome ic) aining p og am.
Imp o ed ( apid) powe p oduc ion in PLYO was hypo hesized o esul in a g ea e gain
in unc ional capaci y compa ed o RT and WALK [12,13,36]. Howe e , his hypo hesis was
only pa ly con i med. Walking pe o mance (10m as walk and 6MWD) equally imp o ed in
RT, PLYO and WALK, and o a simila ex en (4.4–6.7%) as p e iously epo ed a e esis-
ance exe cise [22] o walking [20]. 5xSTS du a ion did no change signi ican ly in ei he o
he g oups. This es was p obably no challenging o aining-speci ic (i.e. no SSC) enough in
ou sample o olde men, as all subjec s we e classi ied as no mobili y-limi ed
(6MWD >400m). Al hough 5xSTS du a ion did no change, he highes mean powe ou pu
in a single si - o-s and ansi ion imp o ed in bo h RT and PLYO. This esul was no in lu-
enced by gains in body mass, as he e was no co ela ion be ween gains in powe and in body
mass no a signi ican gain in body mass pos -in e en ion. In e es ingly, PLYO showed a
g ea e imp o emen in s ai climbing pe o mance han RT. This esul was no su p ising,
gi en ha PLYO imp o ed powe p oduc ion in he leg-ex enso (i.e. knee- and hip-ex enso )
muscles, which play a dominan ole in de eloping he powe needed o p og ess om one
s ep o he nex du ing s ai ascen [37,38]. In addi ion, he o wa d s ep-up (jump) exe cises
in PLYO a e mechanically e y simila o s ai climbing, enhancing he po en ial o inducing
aining-speci ic adap a ions. As s ai climbing is one o he mos demanding unc ional asks
in olde adul s, imp o emen s a e c ucial in main aining independence.
I should be no ed ha some o ou key indings o be ween-g oup di e ences (i.e. esul s
on s ai ascen and squa jump) a e based on non-pa ame ic analyses. Howe e , in mos
cases, non-pa ame ic es s a e conside ed o ha e lesse s a is ical powe han pa ame ic
analyses, meaning ha he la e a e mo e likely o de ec an e ec when i ac ually exis s.
Pa ame ic analyses o ou non-no mally dis ibu ed pa ame e s esul ed in he same conclu-
sions, which indica es owa ds he obus ness o ou esul s.
A seconda y aim o his s udy was o assess he easibili y o plyome ic exe cise in heal hy
olde men. Rec ui men a e was 39.6%, which is accep able and in line wi h ec ui men a es
o ( esis ance) exe cise ials in simila popula ions [22,23,39]. Exe cise adhe ence was e y
high (>80%) in all indi iduals, excep in he ou d opou s, independen o aining g oup.
Subjec s in WALK appea ed o ha e highe adhe ence a es han he o he g oups, wi h some
indi iduals e en exceeding he ecommended amoun o aining sessions. This migh ha e
been caused by he sel - epo in ha g oup, wi h subjec s no ing down e e y daily li e walk
ins ead o solely he walks as pa o he aining p og am. When adhe ence a es in WALK
we e co ec ed by excluding any sessions abo e he p esc ibed aining equency, adhe ence
was simila in all g oups.
Accep abili y o he exe cise p og am was e y high in bo h PLYO and RT, demons a ing
ha plyome ic exe cise is a leas pe cei ed by heal hy olde men as being easible (and o a
simila ex en as esis ance exe cise). All subjec s in PLYO indica ed ha hey we e likely o
pa icipa e in simila exe cise p og ams in he u u e. Howe e , as shown p e iously, his
in en ion o pa icipa e in u u e p og ams appea s o ha e limi ed p edic i e alue o ac ual
long- e m exe cise beha io [40]. Also, ine i able in esea ch wi h olun ee s, a sel -selec ion
bias migh ha e occu ed, by only including highly mo i a ed subjec s in he in e en ion. In
addi ion, subjec s migh ha e ended o gi e socially desi able answe s o he ques ionnai es.
Accep abili y should he e o e be in es iga ed in la ge s udy samples o con i m hese
indings.
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Al hough ou subjec s seemed o enjoy he plyome ic exe cise p og am and conside ed i
o be easible, we canno igno e he ad e se e en s. Two in pa icula need u he a en ion:
knee pain and muscle s ain o he m. gas ocnemius. Fi e ou o 14 subjec s in PLYO epo ed
some kind o knee pain du ing he exe cise p og am. In one subjec , his was ela ed o a non-
ea ed knee inju y in he pas and no speci ically caused by he aining p og am. In h ee
subjec s, knee pain was only epo ed once in he beginning weeks o he exe cise p og am
and disappea ed la e on. This migh ha e been ela ed o he heigh o he box (up o 30–40
cm) du ing s ep-up exe cises, which may ha e caused an un a o able knee join angle (mo e
lexed), o poo echnique (e.g. in e sion a he knee, co ec ed when inspec ed by supe i-
so s). Heigh o he box was educed once subjec s p og essed o jumping (20–30 cm) and
knee pain was no longe epo ed. In only one subjec , knee pain was su icien ly se e e o
cause a d op-ou . I is no clea whe he his pain was caused by he s epping exe cises as such
o by he impac o he landing phase du ing jumping. A mo e se e e ad e se e en , causing
wo subjec s o d op ou , was a s ain in he m. gas ocnemius. In bo h cases, he inju y
occu ed in he second phase o he plyome ic p og am (week 5 o 6), in which sligh , sub-
maximal jumps we e pe o med o amilia ize wi h he exe cises. The inju ies did no seem o
be caused by insu icien wa m-up, no by excessi e a igue, as hey occu ed in se 3 o se 6
(ou o he o al exe cise olume o 9 p e-p og ammed se s). Impo an ly, he s ain occu ed
du ing he concen ic phase o ei he he o wa d o he sideways s ep-up jump. These a e
bo h unila e al exe cises in which he cal muscles a e pa o he p ime mo e s. Conside ing
ha bo h subjec s could be classi ied as obese (BMI o 30.5 and 33.45 kg/m
2
espec i ely), he
cal muscles had o comply wi h high absolu e loading o ces. Excessi e body weigh in combi-
na ion wi h a likely dec ease in gas ocnemius ascicle leng h [15] and Achilles endon s i ness
[15,41] wi h ageing ine i ably inc eases he isk o muscle inju ies du ing such exe cises.
Wi h his in mind, we should e lec on he p ope design and exe cises o be included in a
plyome ic exe cise p og am o olde adul s. To be able o compa e he e ec s o a plyome -
ic-only p o ocol o adi ional esis ance exe cise, we did no include a p epa a ion phase o
esis ance aining be o e in oducing jumps. I can be a gued ha a p ope pe iodiza ion
design is wa an ed, s a ing wi h adi ional esis ance exe cise aimed o induce hype ophy
and maximal s eng h gains, be o e p og essing o explosi e- ype o exe cises. Howe e , we
did p og ess slowly om slow-speed exe cises wi hou jumping o e submaximal jumps o
maximal jumps. The h ee plyome ic exe cises a e all conside ed o be low-in ensi y d ills
[42]. Coun e mo emen jumps ha e been used mul iple imes in exe cise p og ams o heal hy
olde adul s wi hou any ad e se e en s [43,44]. S ep-up exe cises we e chosen conside ing
hei bene icial e ec s on muscle s eng h and unc ional pe o mance [23] and hei esem-
blance o s ai climbing, i.e. one o he mos demanding unc ional asks o olde adul s. In
addi ion, he la e al s ep-up jumps we e al eady used in olde women wi hou any ad e se
e en s [36]. Subjec s in ou s udy we e ecommended o use wall ba s i necessa y (bo h o
educe in ensi y and he balance componen ), bu only one subjec chose o do so. T aining
olume pe session, in plyome ics ypically exp essed as o al numbe o oo con ac s, was
limi ed o ecommended guidelines o beginne s (i.e. 80 o 100) [42] and e en dec eased wi h
inc easing aining in ensi y o keep inju y isk o he minimum. Adequa e eco e y, i.e.
be ween epe i ions (5 s, consecu i e jumps only in las aining phase), be ween se s (1 min.),
be ween exe cises (a leas 2 min.) and be ween aining sessions (48 – 72h), was p o ided
[42]. Al hough we did no measu e ma ke s o muscle damage, subjec s in PLYO did no
epo excessi e muscle so eness a e aining. Howe e , gi en ha plyome ic exe cise in e -
en ions in olde adul s emain sca ce in li e a u e, mo e esea ch is u gen ly needed o se he
app op ia e aining dose ( olume, in ensi y, equency, du a ion) [18] and exe cises o op i-
mizing gains in powe and unc ional capaci y and o minimizing inju y isk. In addi ion, we
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should acknowledge ha i is challenging o quan i y exe cise in ensi y (i.e. bo h mechanical
load and neu omuscula demand) [45] and a igue du ing plyome ic exe cises, al hough i
would de ini ely be o added alue o op imize aining dose.
Based on he indings o he cu en s udy, people migh ques ion whe he i eally is wo h
doing mo e s ess ul plyome ic jump aining as opposed o egula walking. Aside om
aining-speci ic gains in s eng h, powe , jump and s ai climbing pe o mance, mo e ‘neu-
al’ unc ional pe o mance es s (i.e. walking and STS) do no seem o imp o e as obus ly.
Howe e , he ollowing aspec s need o be conside ed. Fi s ly, i should be no ed ha he ela-
ionship be ween muscle powe and unc ional pe o mance is cu ilinea [5]. Hence, o low
le els o muscle powe , he imp o emen in powe leads o a subs an ial imp o emen in unc-
ional pe o mance. Howe e , abo e a ce ain le el o baseline muscle powe , u he inc eases
in powe do no lead o u he inc eases in he pa ame e s usually assessed o egis e unc-
ional pe o mance (e.g. STS abili y). Ou subjec s we e well- unc ioning olde men wi h ela-
i ely high baseline le els o muscle powe , which migh explain he null indings wi h ega d
o STS abili y. No wi hs anding, any imp o emen in muscle powe in well- unc ioning olde
adul s should be ecognized as impo an , e en i i does no esul in u he imp o emen s in
unc ional pe o mance. Highe le els o muscle powe can a leas pos pone he d op below
he disabili y h eshold. Secondly, STS abili y is subjec o a ceiling e ec in well- unc ioning
adul s, as no ed p e iously [28]. Ins ead o ques ioning he bene icial e ec o plyome ic exe -
cise on unc ional pe o mance, i may be necessa y o ques ion whe he adi ional unc ional
pe o mance es s a e sensi i e enough o cap u e changes in well- unc ioning olde adul s.
Jumping is a mo e sensi i e measu e o powe pe o mance han chai ising [46]. E en
hough jumping is no an ac i i y ha olde adul s do on a egula basis, he inabili y o jump
is ela ed o poo e sel - epo ed heal h, mo e como bidi ies, wo se cogni i e unc ioning,
mo e limi a ions in daily li e ac i i ies and highe all incidence [47]. Thi dly, in ensi y is no
some hing o be ea ed, as discussed by Hun e e al. [48] and commen ed by Gen il e al. [49].
Ageing is associa ed wi h bo h a decline in ype II ibe size and in he abili y o ac i a e hese
ibe s [50,51], esul ing in dec eased s eng h and powe p oduc ion. To ain hese ype II
ibe s, high e o s a e needed, ei he h ough using ela i ely high loads (as in RT), pe o ming
exe cises a high eloci y (as in PLYO) o aining o momen a y ailu e [49]. Acco ding o
Henneman’s size p inciple, walking a com o able pace is no su icien o a ge he ype II
ibe s and is he e o e incapable o coun e ing his age- ela ed decline.
Conside ing he cos -bene i o ou plyome ic exe cise p og am, we canno claim ha
plyome ic aining is be e han concen ic-only machine-based powe aining, as p e i-
ously pe o med by se e al esea ch g oups [13,52]. While concen ic-only machine-based
powe aining o al e na i e plyome ic aining wi h machines designed o limi he impac
o he landing phase (e.g. [24,32]) migh be conside ed a sa e modali y o olde adul s,
ad e se e en s in he cu en s udy did no seem o be he esul o high impac du ing landing.
Because o di e ences in he design o he adi ional esis ance exe cise p o ocol as e e ence,
in he s udy popula ion and in measu emen ou comes, i is also di icul o compa e ou
esul s o p e ious indings in machine-based powe aining [13,52]. Wha we can say is
ha bo h plyome ic and machine-based powe aining will imp o e powe and unc ional
pe o mance in olde adul s p e iously unaccus omed o sys ema ic aining, al hough he
mechanisms behind hese imp o emen s a e e y likely aining-mode speci ic. While neu o-
muscula imp o emen s due o machine-based powe aining a e mainly a ibu able o
imp o ed olun a y neu al d i e, plyome ic aining seems o esul in a be e u iliza ion o
he ad an aged p o ided by he SCC [24]. Bo h aspec s a e ulne able o age- ela ed de e io a-
ion [15,16,51] and dese e a en ion in exe cise p og ams o olde adul s.
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To conclude, plyome ic exe cises a e bene icial o e adi ional esis ance aining o
imp o ing muscle powe , jump and s ai climbing pe o mance wi hou comp omising gains
in muscle s eng h. This o m o aining seems easible in olde men, al hough p ope supe i-
sion is wa an ed and cau ion is ad ised when applying unila e al exe cise d ills because o a
po en ial inc ease in he isk o cal muscle inju ies. Box heigh s o 20–30 cm a e easible o
s ep-up jumps in olde men, bu highe heigh s migh esul in mo e epo s o knee pain
because o un a o able knee-join angles. Gi en he bene icial pe o mance- ela ed e ec s o
plyome ic exe cise in olde adul s, u u e esea ch should ocus on op imizing he aining
dose, exe cise d ills and pe iodiza ion schemes.
Suppo ing in o ma ion
S1 Table. Reliabili y alues o jump pa ame e s by compa ing amilia iza ion and base-
line measu emen s.
(DOC)
S2 Table. Reliabili y alues o he explosi e isome ic leg-ex enso es by compa ing
amilia iza ion and baseline measu emen s.
(DOC)
S3 Table. Es ima ed means and SE a baseline (p e-) and pos -in e en ion and % change
(±SD) o squa jump in he h ee in e en ion g oups.
(DOC)
S4 Table. Es ima ed means and SE a baseline (p e-) and pos es and % change (±SD) o
coun e mo emen jump (CMJ) in he h ee in e en ion g oups.
(DOC)
S5 Table. Es ima ed means and SE a baseline (p e-) and pos es and % change (±SD) o
d op jump in he h ee in e en ion g oups.
(DOC)
Au ho Con ibu ions
Concep ualiza ion: E elien Van Roie, Simon Walke , Benedic e Vanwanseele, Ch is ophe
Delecluse.
Da a cu a ion: E elien Van Roie, S ijn Van D iessche, Tijs Delabas i a.
Fo mal analysis: E elien Van Roie.
Funding acquisi ion: E elien Van Roie, Ch is ophe Delecluse.
In es iga ion: E elien Van Roie, Tijs Delabas i a.
Me hodology: E elien Van Roie, Simon Walke , Ch is ophe Delecluse.
P ojec adminis a ion: E elien Van Roie.
Resou ces: Ch is ophe Delecluse.
Supe ision: Simon Walke , Benedic e Vanwanseele, Ch is ophe Delecluse.
W i ing – o iginal d a : E elien Van Roie.
W i ing – e iew & edi ing: Simon Walke , S ijn Van D iessche, Tijs Delabas i a, Benedic e
Vanwanseele, Ch is ophe Delecluse.
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An age-adap ed plyome ic exe cise p og am in olde men
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PLOS ONE | h ps://doi.o g/10.1371/jou nal.pone.0237921 Augus 25, 2020 22 / 22
