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ARTICLE
Exercise tolerance during muscle contractions below and
above the critical torque in different muscle groups
Leonardo Henrique Perinotto Abdalla, Benedito Sérgio Denadai, Natália Menezes Bassan,
and Camila Coelho Greco
Abstract: The objective of this study was to test the hypotheses that end-test torque (ET) (expressed as % maximal voluntary
contraction; MVC) is higher for plantar flexors (PF) than knee extensors (KE) muscles, whereas impulse above ET (IET) is higher
for KE than PF. Thus, we expected that exercise tolerance would be longer for KE than PF only during the exercise performed
above ET. After the determination of MVC, 40 men performed two 5-min all-out tests to determine ET and IET. Eleven partici-
pants performed a further 4 intermittent isometric tests, to exhaustion, at ET + 5% and ET – 5%, and 1 test for KE at the exercise
intensity (%MVC) corresponding to ET + 5% of PF. The IET (7243.2 ± 1942.9 vs. 3357.4 ± 1132.3 N·m·s) and ET (84.4 ± 24.8 vs. 73.9 ±
19.5 N·m) were significantly lower in PF compared with KE. The exercise tolerance was significantly longer for PF (300.7 ± 156.7 s)
than KE (156.7 ± 104.3 s) at similar %MVC (⬃60%), and significantly shorter for PF (300.7 ± 156.7 s) than KE (697.0 ± 243.7 s) at ET +
5% condition. However, no significant difference was observed for ET – 5% condition (KE = 1030.2 ± 495.4 s vs. PF = 1028.3 ± 514.4 s).
Thus, the limit of tolerance during submaximal isometric contractions is influenced by absolute MVC only during exercise
performed above ET, which seems to be explained by differences on both ET (expressed as %MVC) and IET values.
Key words: maximal voluntary contraction, exercise, isometric, muscle volume, fatigue, exercise intensity domain.
Résumé : Cette étude a pour objectif de vérifier les hypothèses selon lesquelles le moment de force a
`la fin du test (« ET », exprimé
en % de la contraction maximale volontaire, « MVC ») est plus élevé chez les fléchisseurs plantaires (« PF ») comparativement aux
extenseurs du genou (« KE ») alors que l’impulsion au-dessus d’ET (« IET ») est plus élevée chez les KE comparativement aux PF. En
conséquence, on s’attend a
`ce que la tolérance a
`l’effort des KE soit plus élevée que celle des PF au cours d’un exercice effectué
au-dessus d’ET. On demande a
`40 hommes dont on a évalué la MVC d’effectuer deux tests de 5 min a
`fond de train afin de
déterminer ET et IET. Onze participants effectuent en outre 4 tests isométriques intermittents a
`ET+5%etET–5%jusqu’a
`
épuisement et effectuent aussi un test des KE a
`l’intensité d’effort (% MVC) correspondant a
`ET+5%dePF.IET(7243,2 ± 1942,9
vs 3357,4 ± 1132,3 N·m·s) et ET (84,4 ± 24,8 vs 73,9 ± 19,5 N·m) sont significativement plus faibles chez PF comparativement aux
KE. La tolérance a
`l’effort est significativement plus grande chez PF (300,7 ± 156,7 s) comparativement a
`KE (156,7 ± 104,3 s) a
`un
même % MVC (⬃60 %) et significativement plus petite chez PF (300,7 ± 156,7 s) comparativement a
`KE (697,0 ± 243,7 s) dans la
condition ET+5%.Toutefois, on ne note pas de différence significative dans la condition ET–5%(KE=1030,2 ± 495,4 s vs PF =
1028,3 ± 514,4 s). Ainsi, la limite de la tolérance au cours de contractions isométriques sous-maximales est influencée par la MVC
absolue seulement au cours d’un exercice effectué au-dessus d’ET ; ce phénomène serait dû aux différences de valeurs d’ET
(exprimé en % MVC) et d’IET. [Traduit par la Rédaction]
Mots-clés : contraction maximale volontaire, exercice physique, isométrique, volume musculaire, fatigue, domaine de l’intensité
de l’effort.
Introduction
Exercise tolerance during different high-intensity exercise pro-
tocols (i.e., constant work rate, incremental, self-paced, and all-
out) can be predicted by a hyperbolic work rate/time function (i.e.,
critical power model) (Chidnok et al. 2013;Souza et al. 2015). Using
this function, it is possible to estimate both the critical power (the
asymptote of the power/time hyperbola) and the hyperbola’s cur-
vature constant (W=)(Dekerle et al. 2015). Critical power has been
considered the lower boundary of severe intensity domain and
corresponds to the highest sustainable rate of oxidative metabo-
lism. The W=represents the total amount of work that can be
performed above critical power before exhaustion occurs. Tradi-
tionally, critical power and W=and those equivalent for running
and swimming (critical velocity and D=, respectively), have been
estimated by 3–5 high-intensity constant work-rate exercises
(Jones et al. 2010). Aiming to reduce the number of bouts of ex-
haustive exercise, Vanhatalo et al. (2007) demonstrated that the
parameters of critical power model can be estimated by a single
3-min all-out exercise test. In this protocol, the end-test power (the
power output in the last 30 s of the test) and the work done above
end-test power were similar to the parameters (critical power and
W=, respectively) estimated during the conventional protocol (i.e.,
constant work-rate exercises).
Recently, some studies have utilized 5-min all-out intermittent
isometric single-leg knee-extensor exercise to characterize mus-
cle bioenergetics and fatigue (Burnley et al. 2012;Broxterman
et al. 2017). Moreover, this protocol has been utilized to estimate
the critical force/torque during exercise involving different mus-
Received 16 June 2017. Accepted 3 October 2017.
L.H.P. Abdalla, B.S. Denadai, N.M. Bassan, and C.C. Greco. Human Performance Laboratory, São Paulo State University (UNESP), Av. 24A, 1515,
Bela Vista, CEP - 13506-900, Rio Claro, SP., Brazil.
Corresponding author: Camila Coelho Greco (email: grecocc@rc.unesp.br).
Copyright remains with the author(s) or their institution(s). Permission for reuse (free in most cases) can be obtained from RightsLink.
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Appl. Physiol. Nutr. Metab. 43: 174–179 (2018) dx.doi.org/10.1139/apnm-2017-0381 Published at www.nrcresearchpress.com/apnm on 12 October 2017.