Blood oxygenation of masseter muscle during sustained elevated muscle activity in healthy participants

Abstract

Background

Myofascial pain associated with temporomandibular disorders has often been linked to pathological muscle hyperactivity. As a result, localized disturbances of intramuscular blood flow could lead to a lower level of oxygen distribution, hypoxia and microcirculatory changes.

Aim

To assess hemodynamic changes in the masseter muscle during sustained elevated muscle activity (SEMA).

Materials and Methods

Sixteen healthy participants performed thirty 1-minute bouts of SEMA with intervals of 1-minute "rest" periods between the bouts on a bite force transducer device. The participants completed three sessions with different percentage of their maximal voluntary occlusal bite force (MVOBF): 0% (no task), 10% or 40% MVOBF. The order of the sessions was randomized with 1-2 weeks intervals. Hemodynamic characteristics of the masseter muscle were estimated with use of a laser blood oxygenation monitor.

Results

Tissue blood oxygen saturation (StO₂) during SEMA was lower than during rest (P < 0.001). The relative changes of total hemoglobin (TotalHb) and StO₂ were influenced by condition (SEMA and rest) and with interactions between condition and session (0%, 10% and 40% MVOBF tasks).

Conclusions

These results suggest that SEMA may lead to hypoxia in the masseter muscle and that the hemodynamic characteristics and muscle symptoms depend on the magnitude of muscle contractions. Overall, the present findings may help to provide better insights into relationships between jaw muscle activity, hemodynamic changes and symptom developments with implications for clinical conditions such as bruxism characterized by different levels of tooth-grinding and tooth-clenching muscle activity.

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