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No evidence of neural adaptations following chronic unilateral isometric training of the intrinsic muscles of the hand: a randomized controlled study

Manca, A; Ginatempo, F; Cabboi, MP; Mercante, B; Ortu, E; Dragone, D; De Natale, ER; ... Deriu, F; + view all (2016) No evidence of neural adaptations following chronic unilateral isometric training of the intrinsic muscles of the hand: a randomized controlled study. European Journal of Applied Physiology , 116 (10) pp. 1993-2005. 10.1007/s00421-016-3451-6. Green open access

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Abstract

Purpose: To test whether long-term cortical adaptations occur bilaterally following chronic unilateral training with a simple motor task. / Methods: Participants (n = 34) were randomly allocated to a training or control groups. Only the former completed a 4-week maximal-intensity isometric training of the right first dorsal interosseus muscle through key pinching. Maximal strength was assessed bilaterally in four different movements progressively less similar to the training task: key, tip and tripod pinches, and handgrip. Transcranial magnetic stimulation was used to probe, in the left and right primary hand motor cortices, a number of standard tests of cortical excitability, including thresholds, intra-cortical inhibition and facilitation, transcallosal inhibition, and sensory-motor integration. / Results: Training increased strength in the trained hand, but only for the tasks specifically involving the trained muscle (key +8.5 %; p < 0.0005; tip +7.2 %; p = 0.02). However, the effect size was small and below the cutoff for meaningful change. Handgrip and tripod pinch were instead unaffected. There was a similar improvement in strength in the untrained hand, i.e., a cross-education effect (key +6.4 %; p = 0.02; tip +4.7 %; p = 0.007). Despite these changes in strength, no significant variation was observed in any of the neurophysiological parameters describing cortico-spinal and intra-cortical excitability, inter-hemispheric inhibition, and cortical sensory-motor integration. / Conclusions: A 4-week maximal-intensity unilateral training induced bilaterally spatial- and task-specific strength gains, which were not associated to direct or crossed cortical adaptations. The observed long-term stability of neurophysiological parameters might result from homeostatic plasticity phenomena, aimed at restoring the physiological inter-hemispheric balance of neural activity levels perturbed by the exercise. / Trial registration number: ClinicalTrials.gov identifier NCT02010398.

Type: Article
Title: No evidence of neural adaptations following chronic unilateral isometric training of the intrinsic muscles of the hand: a randomized controlled study
Open access status: An open access version is available from UCL Discovery
DOI: 10.1007/s00421-016-3451-6
Publisher version: http://dx.doi.org/10.1007/s00421-016-3451-6
Language: English
Additional information: The final publication is available at Springer via http://dx.doi.org/10.1007/s00421-016-3451-6.
Keywords: Cross education, Hand, Homeostatic plasticity, Isometric strength training, Primary motor cortex, Transcranial magnetic stimulation
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Clinical and Movement Neurosciences
URI: https://discovery.ucl.ac.uk/id/eprint/1508955
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