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The objective of this study was to test the hypothesis that neuromuscular fatigue influences the rate of torque development (RTD) in a similar manner to isometric torque. Nine men participated in this study and performed 5-min all-out isometric tests for knee extensors (KE) and plantar flexors (PF) muscles, to determine the end-test torque (ET) and the critical rate of torque development (critical RTD). Additionally, participants performed submaximal constant-torque tests to task failure for KE and PF muscles. Both maximal voluntary contraction and RTD exhibited hyperbolic behavior and reached an asymptote at the end of the 5-min all out isometric test with similar relative values (KE 29.5 ± 5.6% MVC and PF 50.9 ± 2.9% MVC and KE 25.1 ± 3.6 to 28.5 ± 4.4% RTD and PF 48.4 ± 6.5 to 52.4 ± 5.8% RTD). However, both % MVC and % RTD were statistically different between muscle groups (P < 0.05), even when normalized by muscle volume (P < 0.05). Torque and RTD after the constant-torque test were similar to the values of ET and critical RTD (P > 0.05), respectively. In this study, it was observed that neuromuscular fatigue affects RTD and torque similarly, with the magnitude of this effect varying according to the muscle size.
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Vol.:(0123456789)
European Journal of Applied Physiology
https://doi.org/10.1007/s00421-024-05647-4
ORIGINAL ARTICLE
Is there acritical rate oftorque development?
LeonardoHenriquePerinottoAbdalla1 · CamilaCoelhoGreco1· BeneditoSérgioDenadai1
Received: 10 July 2024 / Accepted: 20 October 2024
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024
Abstract
The objective of this study was to test the hypothesis that neuromuscular fatigue influences the rate of torque development
(RTD) in a similar manner to isometric torque. Nine men participated in this study and performed 5-min all-out isometric
tests for knee extensors (KE) and plantar flexors (PF) muscles, to determine the end-test torque (ET) and the critical rate of
torque development (critical RTD). Additionally, participants performed submaximal constant-torque tests to task failure for
KE and PF muscles. Both maximal voluntary contraction and RTD exhibited hyperbolic behavior and reached an asymptote
at the end of the 5-min all out isometric test with similar relative values (KE 29.5 ± 5.6% MVC and PF 50.9 ± 2.9% MVC
and KE 25.1 ± 3.6 to 28.5 ± 4.4% RTD and PF 48.4 ± 6.5 to 52.4 ± 5.8% RTD). However, both % MVC and % RTD were
statistically different between muscle groups (P < 0.05), even when normalized by muscle volume (P < 0.05). Torque and
RTD after the constant-torque test were similar to the values of ET and critical RTD (P > 0.05), respectively. In this study,
it was observed that neuromuscular fatigue affects RTD and torque similarly, with the magnitude of this effect varying
according to the muscle size.
Keywords Rate of torque development· Torque-time relationship· Neuromuscular fatigue· Muscle volume
Introduction
The rate of torque development (RTD, analogous to rate of
force development, RFD) is defined as the maximal human
capacity to rapidly develop muscle torque (Aagaard etal.
2002). RTD is obtained from the ascending part (slope)
of the torque-time curve (Δtorque/Δtime) of an explosive
isometric contraction. In addition to maximal voluntary
contraction (MVC), RTD has received increasing interest,
specifically in the assessment of explosive strength in many
situations of physical training and rehabilitation since it is
also considered an important parameter in detecting changes
in neuromuscular function (Maffiuletti etal. 2016). RTD
can be assessed at different time windows from the onset of
contraction (Aagaard etal. 2002). Generally, early phases of
RTD are influenced by neural activation, reflecting the effi-
ciency of motor neuron transmission to the muscles (Folland
etal. 2014; Maffiuletti etal. 2016; Del Vecchio etal. 2019).
In contrast, late phases are more closely related to factors
such as MVC, muscle thickness, cross-sectional area, mus-
cle architecture, and neuromuscular fatigue (Andersen and
Aagaard 2006; Andersen etal. 2010; Folland etal. 2014;
Cossich and Maffiuletti 2020; D'Emanuele etal. 2021). Con-
ceptually, RTD is better represented as a continuum rather
than as discrete data points (see Del Vecchio 2023).
Although the effect of neuromuscular fatigue on maxi-
mal strength was reported by Angelo Mosso in 1891, this
phenomenon has since been extensively investigated and
documented in the literature, with significant contributions
over the past 130years (see Gandevia 2001). However, the
impact of fatigue on the ascending part of the Δtorque/Δtime
curve has been described more recently. Zhou (1996) and
Zhou etal. (1998) reported a similar fatigue-related decline
in MVC (57 and 55%, respectively) versus peak RFD (56
and 53%, respectively), after 25 maximal isometric con-
tractions of the knee extensors (KE) muscles. Likewise,
Andersen etal. (2014) showed a hyperbolic and relatively
similar behavior between torque and RTD (66% MVC) dur-
ing 100 MVC of shoulder elevation. However, Viitasalo and
Komi (1981) demonstrated that 100 explosive isometric
contractions of the KE muscles decreased MVC and peak
Communicated by Toshio Moritani.
* Leonardo Henrique Perinotto Abdalla
leonardo.abdalla@unesp.br
1 Human Performance Laboratory, UNESP, Av. 24 A, 1515,
Bela Vista, RioClaro, SPCEP–13506-900, Brazil
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