Measurement of blood lactate as a function of vocal loading and neuromuscular electrical stimulation: Proof of concept.

The goal of the current investigation was to establish proof of concept regarding measurement of blood lactate levels as an indicator of laryngeal muscle activity and fatigue, as well as to examine the relationship between blood lactate levels and NMES intensity. Fifteen participants completed a vocal loading exercise while blood lactate was measured prior to, during, and upon completion of the exercise. Acoustic measures of voice production and subjective reports of fatigue/soreness were obtained pre- and post-vocal loading task. The participants were divided into three groups: those who did not receive laryngeal neuromuscular electrical stimulation (NMES), those who received laryngeal NMES at a minimally perceivable level of intensity, and those who received laryngeal NMES at a maximum tolerable level of intensity. Changes in blood lactate levels were observed during the vocal loading task, thus indicating that blood lactate measurements are sensitive enough to reflect laryngeal muscle activity. No consistent pattern between blood lactate levels and NMES intensity or fatigue emerged. Several factors may account for these findings.