J Physiol 596.6 (2018) pp 1091–1102
The Journal of Physiology
The metaboreﬂex does not contribute to the increase
in muscle sympathetic nerve activity to contracting
muscle during static exercise in humans
and Vaughan G. Maceﬁeld
School of Science and Health, Western Sydney University, Sydney, NSW, Australia
School of Medicine, Western Sydney University, Sydney, NSW, Australia
Neuroscience Research Australia, Sydney, NSW, Australia
Mohammed Bin Rashid University of Medicine & Health Sciences, Dubai, UAE
Edited by: Michael Hogan & Dario Farina
It is not clear how sympathetic activity to contracting muscle is controlled.
We recorded muscle sympathetic nerve activity (MSNA) to the ipsilateral tibialis anterior
muscle during 4 min of isometric dorsiﬂexion of the ankle and 6 min of post-exercise ischaemia,
which was repeated contralaterally.
MSNA to the contracting muscle increased within 1 min of static exercise and returned to
pre-contraction levels at the end.
Unlike the increase in MSNA seen in the non-contracting muscle, post-exercise ischaemia had
no effect on MSNA to the contracted muscle.
We conclude that central command is the primary mechanism responsible for increasing
MSNA to contracting muscle and also that the metaboreﬂex is not expressed in contracting
Abstract Both central command and metaboreﬂex inputs from contracting muscles increase
muscle sympathetic nerve activity (MSNA) to non-contracting muscle during sustained
isometric exercise. We recently showed that MSNA to contracting muscle also increases in an
intensity-dependent manner, although whether this can be sustained by the metaboreﬂex is
unknown. MSNA was recorded from the left common peroneal nerve and individual spikes of
MSNA extracted from the nerve signal. Eleven subjects performed a series of 4 min dorsiﬂexions
of the left ankle at 10% of maximum voluntary contraction under three conditions: without
ischaemia, with 6 min of post-exercise ischaemia, and with ischaemia during and after exercise;
these were repeated in the right leg. Compared with pre-contraction values, MSNA to the
contracting muscles increased and plateaued in the ﬁrst minute of contraction (50 ± 18 vs.
Danny Boulton undertook his PhD with Professor Vaughan Maceﬁeld, Associate Professor Simon Green and
Dr Chloe Taylor at Western Sydney University, studying the control of sympathetic nerve activity to contracting
muscle during static exercise; his PhD was conferred in August 2017. Prior to this, he undertook a Bachelor of
Applied Science (Sport and Exercise Science) at Western Sydney University, having been awarded a Distinction
and the Dean’s Medal in 2011, and was also awarded First Class Honours for his research work, as well as the
University Medal for academic excellence, in 2013.
2018 The Authors. The Journal of Physiology
2018 The Physiological Society DOI: 10.1113/JP275526