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Updated: Dec 29, 2025

Assessment of Neuromuscular Function Using Percutaneous Electrical Nerve Stimulation
Published on: September 13, 2015
Immobility and F-waves: Impact on lower motor neuron excitability
Mariana Pereira1, Michael Swash1,2, Mamede de Carvalho1,3
1Instituto de Fisiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Univeridade de Lisboa, Lisbon, Portugal.
Introduction:
Immobility of the upper limbs has been associated with reduction of F-wave frequency. However, there are no similar studies on lower limb (LL) F-waves. We investigated the impact of LL rest on F-wave and H-reflex parameters.
Methods:
The LLs of 14 healthy participants were studied after 90 minutes rest. F-waves (frequency, latencies, chronodispersion, and mean amplitude) and H-reflexes (latency and recruitment curve) were investigated bilaterally. In seven participants the protocol was repeated, but the temperature of one limb was reduced.
Results:
Immobility only changed F-wave latencies, which increased significantly (mean value of 2 ms, P < .01). Limb cooling did not influence results.
Discussion:
Contrary to what occurred in cervical lower motor neurons (LMN), LL LMNs did not show a reduced F-wave response to immobility, but their latency increased significantly. This could have been due to reduced Renshaw inhibition of small LMNs, thus facilitating their response to antidromic stimulation and causing delayed late responses.
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