In vivo 3D imaging of human motor units in upper and lower limb muscles

Heskamp, Linda; Miller, Alexis R.; Birkbeck, Matthew; Hall, Julie; Schofield, Ian; Blamire, Andrew M.; Whittaker, Roger

doi:10.1016/j.clinph.2022.05.018

Cited by 7 publications

(4 citation statements)

References 25 publications

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“…The approach presented in this paper will facilitate in-depth studies on muscle 3D strain heterogeneity in relation to muscle architecture, composition, and function, including properties such as fascicle lengths and curvature, (physiological) cross-sectional area, the extracellular matrix and fiber types within the muscle. 8,52,53 Furthermore, in combination with additional (imaging) techniques such as EMG, electrical stimulation, 16,54,55 and motor unit MRI, 56 more insights in motor unit activation and neural control in relation to muscle fiber strain and architecture can be obtained, which would help linking muscle contractile function to architecture and potentially to loss of function.…”

Section: Discussionmentioning

confidence: 99%

Muscle fiber strain rates in the lower leg during ankle dorsi‐/plantarflexion exercise

Hooijmans,

Veeger,

Mazzoli

et al. 2023

NMR in Biomedicine

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Static quantitative magnetic resonance imaging (MRI) provides readouts of structural changes in diseased muscle, but current approaches lack the ability to fully explain the loss of contractile function. Muscle contractile function can be assessed using various techniques including phase‐contrast MRI (PC‐MRI), where strain rates are quantified. However, current two‐dimensional implementations are limited in capturing the complex motion of contracting muscle in the context of its three‐dimensional (3D) fiber architecture. The MR acquisitions (chemical shift‐encoded water–fat separation scan, spin echo‐echoplanar imaging with diffusion weighting, and two time‐resolved 3D PC‐MRI) wereperformed at 3 T. PC‐MRI acquisitions and performed with and without load at 7.5% of the maximum voluntary dorsiflexion contraction force. Acquisitions (3 T, chemical shift‐encoded water–fat separation scan, spin echo‐echo planar imaging with diffusion weighting, and two time‐resolved 3D PC‐MRI) were performed with and without load at 7.5% of the maximum voluntary dorsiflexion contraction force. Strain rates and diffusion tensors were calculated and combined to obtain strain rates along and perpendicular to the muscle fibers in seven lower leg muscles during the dynamic dorsi‐/plantarflexion movement cycle. To evaluate strain rates along the proximodistal muscle axis, muscles were divided into five equal segments. t‐tests were used to test if cyclic strain rate patterns (amplitude > 0) were present along and perpendicular to the muscle fibers. The effects of proximal‐distal location and load were evaluated using repeated measures ANOVAs. Cyclic temporal strain rate patterns along and perpendicular to the fiber were found in all muscles involved in dorsi‐/plantarflexion movement (p < 0.0017). Strain rates along and perpendicular to the fiber were heterogeneously distributed over the length of most muscles (p < 0.003). Additional loading reduced strain rates of the extensor digitorum longus and gastrocnemius lateralis muscle (p < 0.001). In conclusion, the lower leg muscles involved in cyclic dorsi‐/plantarflexion exercise showed cyclic fiber strain rate patterns with amplitudes that varied between muscles and between the proximodistal segments within the majority of muscles.

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Section: Discussionmentioning

confidence: 99%

Muscle fiber strain rates in the lower leg during ankle dorsi‐/plantarflexion exercise

Hooijmans,

Veeger,

Mazzoli

et al. 2023

NMR in Biomedicine

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“…This number is termed the “innervation ratio”. Recent work has shown considerable complexity in the spatial arrangement and shape of MUs in individual muscles ( Heskamp et al, 2022 ).…”

Section: Generation Of the Cmapmentioning

confidence: 99%

Revisiting the compound muscle action potential (CMAP)

Barkhaus,

Nandedkar,

de Carvalho

et al. 2024

Clinical Neurophysiology Practice

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“…An approach using DW MRI has recently been combined with in-scanner electrical stimulation to image individual MUs [94,95], figure 3. Its potential for detecting muscle reinnervation is exciting, allowing simultaneous surveillance of multiple muscles for the presence of actively or passively stimulated MUs.…”

Section: Motor Unit Mri (Mumri)mentioning

confidence: 99%

“…3D MUMRI reveals a more complex human motor unit structure than previously thought, with several units splitting and re-forming along their length. Reproduced from Heskamp et al CC BY 4.0[95].…”

mentioning

confidence: 99%

A scoping review of current and emerging techniques for evaluation of peripheral nerve health, degeneration and regeneration: part 2, non-invasive imaging

et al. 2023

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Peripheral neuroregenerative research and therapeutic options are expanding exponentially. With this expansion comes an increasing need to reliably evaluate and quantify nerve health. Valid and responsive measures of the nerve status are essential for both clinical and research purposes for diagnosis, longitudinal follow-up, and monitoring the impact of any intervention. Furthermore, novel biomarkers can elucidate regenerative mechanisms and open new avenues for research. Without such measures, clinical decision-making is impaired, and research becomes more costly, time-consuming, and sometimes infeasible. Part 1 of this two-part scoping review focused on neurophysiology. In Part 2, we identify and critically examine many current and emerging non-invasive imaging techniques that have the potential to evaluate peripheral nerve health, particularly from the perspective of regenerative therapies and research.

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In vivo 3D imaging of human motor units in upper and lower limb muscles

Cited by 7 publications

References 25 publications

Muscle fiber strain rates in the lower leg during ankle dorsi‐/plantarflexion exercise

Muscle fiber strain rates in the lower leg during ankle dorsi‐/plantarflexion exercise

Revisiting the compound muscle action potential (CMAP)

A scoping review of current and emerging techniques for evaluation of peripheral nerve health, degeneration and regeneration: part 2, non-invasive imaging

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