Marking the differences in motoneurons

Abstract

A subgroup of the neurons that control muscles becomes less excitable shortly before the symptoms of ALS develop.

Head-down tilt bed rest with or without artificial gravity is not associated with motor unit remodeling

“…MUNIX has mostly been used to investigate the progressive changes in MU number and size during ALS and ageing, conditions that are characterized by loss of both upper and lower body motoneurons (Sharples and Whelan 2018 ; Larsson et al 2019 ). In general, these studies have observed a 30–42% loss of MUs in the same muscles as tested in our study (Drey et al 2013 ; Escorcio-Bezerra et al 2016 ), with concurrent increases in MU size (Larsson 2003 ), due to reinnervation of denervated muscle fibres via nerve sprouting (Gordon et al 2004 ; Roy et al 1996 ).…”

“…In our study, however, participants were tested only twice during the HDBR, and it is thus unlikely that the testing sessions prevented changes in MU number or size, particularly when one considers that others have seen that even on the 1st day of leg casting, evidence for reduced MU numbers has been observed (Fuglsang-Frederiksen and Scheel 1978). Moreover, there was no restriction to the degree of possible dorsiflexion, and hand muscles likely worked to a greater extent than in everyday life, due to activities being primarily restricted to upper limb movement, i.e., using a MUNIX has mostly been used to investigate the progressive changes in MU number and size during ALS and ageing, conditions that are characterized by loss of both upper and lower body motoneurons (Sharples and Whelan 2018;Larsson et al 2019). In general, these studies have observed a 30-42% loss of MUs in the same muscles as tested in our study (Drey et al 2013;Escorcio-Bezerra et al 2016), with concurrent increases in MU size (Larsson 2003), due to reinnervation of denervated muscle fibres via nerve sprouting (Gordon et al 2004;Roy et al 1996).…”