Voluntary activation and cortical activity during a sustained maximal contraction: An fMRI study

Post, Marijn; Steens, Anneke; Renken, Remco; Maurits, Natasha M.; Zijdewind, Inge

doi:10.1002/hbm.20562

Cited by 68 publications

(77 citation statements)

References 46 publications

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“…During the sustained contraction, the differences in associated activity across hand positions became very apparent. It was already known that the amount of associated activity increases during a sustained contraction (Zijdewind and Kernell, 2001), and this observation has recently been confirmed by fMRI data showing an increase in ipsilateral activation of the precentral and postcentral gyrus during a sustained maximal contraction (Post et al, 2009). In our opinion, this observation demonstrates that the increase in associated activity during sustained contractions is attributable to an increased central drive toward the target muscles accompanied by increased activity to the nontarget hemisphere resulting in increased associated activity.…”

Section: Discussionmentioning

confidence: 61%

Inadvertent Contralateral Activity during a Sustained Unilateral Contraction Reflects the Direction of Target Movement

Post¹,

Bakels²,

Zijdewind³

2009

J. Neurosci.

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Strong unilateral contractions are accompanied by excitatory effects to the ipsilateral cortex. This activity can even result in overt contractions of muscles in the contralateral limb. We used this inadvertent, associated activity to study whether the cortical presentation of movements is organized in a directional-related or a muscle-related reference frame. We assessed the contralateral activation for the left index finger during a sustained maximal abduction of the right index finger. In the first experiment, both hands were held vertically in a symmetrical orientation, and in the second experiment the hands were in an asymmetrical orientation (left hand, palm downward; right hand, vertical). In both experiments, the direction of the contralateral associated contraction was upward, i.e., in the symmetrical hand orientation the contralateral force increased mainly in abduction direction, whereas in the asymmetrical hand orientation the contralateral force increased in the extension direction. Thus, the contralateral contractions reflected the direction of the target movement rather than simply the activity of the muscles activated on the target side. These observations provide strong evidence that motor commands are organized in an extrinsic, direction-related reference frame, as opposed to an internal muscle-related reference frame.

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Section: Discussionmentioning

confidence: 61%

Inadvertent Contralateral Activity during a Sustained Unilateral Contraction Reflects the Direction of Target Movement

Post¹,

Bakels²,

Zijdewind³

2009

J. Neurosci.

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“…In contrast to previous observations demonstrating less of a difference in performance capabilities between the dominant and nondominant arms and hands of left-handed subjects compared with right-handed subjects (Adamo et al 2012;Klöppel et al 2007;Przybyla et al 2012), the current findings indicate greater relative variability in endurance time for lefthanded subjects when performing submaximal fatiguing contractions that required either force or position control. The greater variability exhibited by the left-handed subjects may be a consequence of the fatiguing contractions engaging extensive cortical networks (Korotkov et al 2005;Liu et al 2003;Post et al 2009) that involve previously reported cortical asymmetries in left-handed individuals (van den Berg et al 2011). Although the current study does not provide insight on the underlying mechanisms, one functional consequence of the greater variability exhibited by left-handed participants is that interventions capable of prolonging endurance time for these types of fatiguing contractions (Barry et al 2008;Mottram et al 2006;Riley et al 2008;Semmler et al 2000;Yue et al 1997) would more consistently transfer changes in performance across tasks in right-handed than in left-handed persons.…”

Section: Force and Position Tasksmentioning

confidence: 86%

Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions

Gordon

Rudroff

Enoka

et al. 2012

Journal of Neurophysiology

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Gordon NM, Rudroff T, Enoka JA, Enoka RM. Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions. J Neurophysiol 108: 1501-1510. First published June 13, 2012 doi:10.1152/jn.01144.2011The purpose of this study was to compare endurance time and accompanying neuromuscular adjustments when left-and right-handed subjects used the dominant and nondominant arms to sustain submaximal contractions that required either force or position control. Ten left-handed and 10 right-handed healthy adults (21 Ϯ 5 yr) participated in the study. Each subject exerted a similar net torque about the elbow joint during the force and position tasks to achieve a target force of 20% maximal voluntary contraction (MVC) force (56 Ϯ 18 N). MVC force declined to a similar level immediately after task failure for left-and righthanded subjects (27 Ϯ 13 vs. 25 Ϯ 15%, P ϭ 0.9). Endurance time for the position task was similar for the dominant and nondominant arms (task ϫ dominance interaction, P ϭ 0.17). Although the difference in endurance time between the two tasks was similar for left-handed (136 Ϯ 165 s) and right-handed individuals (92 Ϯ 73 s, task ϫ handedness interaction, P ϭ 0.38), there was greater variance in the ratio of the endurance times for the force and position tasks for left-handed (0.77) than right-handed subjects (0.13, P Ͻ 0.001; see Fig. 2). Furthermore, endurance time for the force and position tasks was significantly correlated for right-handed subjects (r 2 ϭ 0.62, P Ͻ 0.001), but not for left-handed subjects (r 2 ϭ 0.004, P ϭ 0.79). Multiple regression analyses identified sets of predictor variables for each endurance time, and these differed with handedness and task. Hand dominance, however, did not influence endurance time for either group of subjects. These findings indicate that endurance times for the elbow flexors when performing submaximal isometric contractions that required either force or position control were not influenced by hand dominance but did depend on handedness. electromyography; muscle fatigue; task failure THE PREFERENTIAL USE OF ONE ARM during motor tasks is known as hand dominance and defines the handedness of an individual. A right-handed individual, for example, tends to use the right hand to perform most activities of daily living, such as writing, throwing, using scissors, brushing teeth, cutting with a knife, eating with a spoon, striking a match, and opening a box. However, some actions are more commonly performed with the nondominant limb, which results in each arm developing a unique set of motor skills (Adamo and Martin 2009; Bernard et al.

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“…This plateau, in line with the NIRS reduction in cerebral oxygenation near-maximal exercise reported above (92), can be interpreted as an altered central motor command, i.e., the so-called central fatigue. Such an interpretation should take into account that modified BOLD signals can reflect changes in neuronal input and/or processing and changes in inhibitory and/or excitatory inputs (84). In some parts of the cortex involved in motor task performance in normoxia (supplementary motor areas, the supramarginal gyrus and parts of the motor cortex), BOLD changes during finger tapping are strongly attenuated by hypoxia, further suggesting that hypoxia may not uniformly affect all brain regions (110).…”

Section: Cerebral Oxygenationmentioning

confidence: 99%

Cerebral perturbations during exercise in hypoxia

Vergès

Rupp

Jubeau

et al. 2012

American Journal of Physiology-Regulatory, Integrative and Comp

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Reduction of aerobic exercise performance observed under hypoxic conditions is mainly attributed to altered muscle metabolism due to impaired O 2 delivery. It has been recently proposed that hypoxia-induced cerebral perturbations may also contribute to exercise performance limitation. A significant reduction in cerebral oxygenation during whole body exercise has been reported in hypoxia compared with normoxia, while changes in cerebral perfusion may depend on the brain region, the level of arterial oxygenation and hyperventilation induced alterations in arterial CO 2. With the use of transcranial magnetic stimulation, inconsistent changes in cortical excitability have been reported in hypoxia, whereas a greater impairment in maximal voluntary activation following a fatiguing exercise has been suggested when arterial O 2 content is reduced. Electromyographic recordings during exercise showed an accelerated rise in central motor drive in hypoxia, probably to compensate for greater muscle contractile fatigue. This accelerated development of muscle fatigue in moderate hypoxia may be responsible for increased inhibitory afferent signals to the central nervous system leading to impaired central drive. In severe hypoxia (arterial O 2 saturation Ͻ70 -75%), cerebral hypoxia per se may become an important contributor to impaired performance and reduced motor drive during prolonged exercise. This review examines the effects of acute and chronic reduction in arterial O 2 (and CO2) on cerebral blood flow and cerebral oxygenation, neuronal function, and central drive to the muscles. Direct and indirect influences of arterial deoxygenation on central command are separated. Methodological concerns as well as future research avenues are also considered. cerebral perfusion; cerebral oxygenation; cortex excitability; central motor command; endurance WITH THE EXCEPTION of very short or static exercises performed at a high percentage of maximal power (15,19,83), hypoxia deteriorates exercise performance (7, 82). In particular, the maximal aerobic workload (Ẇ max ) that can be sustained during exercise involving large muscle groups (e.g., cycling) is considerably lower in hypoxia compared with normoxia. The difference between these two environmental conditions increases progressively with the reduction in oxygen inspiratory pressure (PI O 2 ) (36) and is affected by subjects' fitness so that subjects with elevated maximal aerobic capacity are more affected by hypoxia (41).The origin of exercise performance limitation in hypoxia is still under debate, since the consequences of reduced blood O 2 affect the whole organism. This limitation has been attributed to a lowered O 2 partial pressure in arterial blood (Pa O 2 ) reducing arterial O 2 content and O 2 delivery to tissues with critical consequences on muscle metabolism and contraction (1, 46). Magnetic nerve stimulation has confirmed the effects of reduced arterial oxygenation on dynamic (12, 111) and static (54) exercise-induced alterations in muscle contractility. Reduced muscle O...

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Voluntary activation and cortical activity during a sustained maximal contraction: An fMRI study

Cited by 68 publications

References 46 publications

Inadvertent Contralateral Activity during a Sustained Unilateral Contraction Reflects the Direction of Target Movement

Inadvertent Contralateral Activity during a Sustained Unilateral Contraction Reflects the Direction of Target Movement

Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions

Cerebral perturbations during exercise in hypoxia

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