Investigation of Fatigue, Delayed-Onset Muscle Soreness, and Spectral-Based Cepstral Measurements in Healthy Speakers after Neuromuscular Electrical Stimulation

Abstract

Objectives: We observed whether 30 minutes of neuromuscular electrical stimulation applied to the necks of healthy speakers would result in significant acoustic changes and perceptions of fatigue and/or delayed-onset muscle soreness (DOMS). Methods: Twelve participants were assigned to experimental (n = 6; 3 male and 3 female) and control groups (n = 6; 3 male and 3 female). Neuromuscular electrical stimulation was applied to the anterior neck in the experimental group only. All participants produced 3 trials of the vowel / a/ and the Rainbow Passage before and after completing a 30-minute phonation protocol. Recorded samples were analyzed for measures of the cepstral peak prominence, the ratio of low- to high-frequency spectral energy, and their respective standard deviations. Perceptions of fatigue and DOMS were rated on visual analog scales before, 5 minutes after, and 24 hours after completion of the phonation protocol. Results: Statistically significant acoustic findings reflecting reduced relative sound pressure level, increased high-frequency noise, and phonatory instability were observed in the experimental group. In addition, reports of fatigue and DOMS were also reported by some participants. Conclusions: A 30-minute dosage may be too high for some people experiencing neuromuscular electrical stimulation for the first time.