Key result
Lower limb immobility for 90 minutes significantly increased F-wave latencies by a mean of 2 ms (P < 0.01) in healthy participants.
Why the study?
Upper limb immobility reduces F-wave frequency, but similar studies on lower limb F-waves were lacking.
Does lower limb immobility alter F-wave and H-reflex parameters in healthy participants?
Does lower limb immobility alter F-wave and H-reflex parameters in healthy participants?
Lower limb immobility increases F-wave latency without reducing F-wave response, suggesting a different lower motor neuron excitability response compared to upper limbs.
Answers are grounded in this paper and cite their sources.
May confound F-wave interpretation after brief immobility; hypothesis-generating for limb-specific excitability differences.
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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Pereira et al. (2020) studied Healthy (n=14). Lower limb rest (immobility) vs. Baseline was evaluated on F-wave latencies (mean increase of 2 ms, p=<.01). Lower limb immobility for 90 minutes significantly increased F-wave latencies by a mean of 2 ms (P < 0.01) in healthy participants.
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