Two different analyzing methods for inhibitory reflexes: Do they yield comparable outcomes?

BACKGROUND: For the analysis of inhibitory reflexes, no consensus exists regarding the methodology that should be used. The most commonly used methods are the cumulative sum (CUSUM) error box and the t-test. The aim of this study was to assess the interexaminer reliability of those two analyzing methods and to test whether both methods: yield similar results. METHODS: Inhibitory jaw reflexes were recorded from the right masseter muscle of 11 participants (6 males, 5 females). Electrical stimuli were applied at the hairy skin of the upper lip on the right side. In total, 16 stimuli were applied while the participants maintained their clenching level at 10% of their maximum voluntary EMG activity. Two different examiners analyzed the reflex data with two different methods: the CUSUM error box and the t-test. The outcome variables were the number of reflex parts, the reflex area size, and the reflex onset. Comparability between examiners and between the two analyzing methods: was assessed with the use of the intraclass correlation coefficient (ICC). RESULTS: The interexaminer reliability was fair-to-good to excellent for both the CUSUM error box and the t-test analyses and for all the variables tested. The comparability of the two analyzing methods: was fair-to-good. COMPARISON WITH EXISTING METHODS/CONCLUSION: When analyzing the inhibitory reflex data, both the CUSUM error box and the t-test can be used.

Reproducible effects of subjectively assessed muscle fatigue on an inhibitory jaw reflex in humans.

OBJECTIVE: To evaluate the effects of exercise-induced, subjectively assessed muscle fatigue on an inhibitory jaw reflex, evoked by electrical stimulation of the upper lip. In addition, the reproducibility of these effects was assessed. DESIGN: Eight subjects participated in two experimental sessions that were two weeks apart. During each session, a baseline recording, a post-conditioning recording, and two recovery recordings were obtained. The post-conditioning recording was obtained immediately after provocation of jaw muscle fatigue by intense chewing. The endpoint of provocation was reached 30s after a subject had crossed the value '6' on a 10 cm long visual analogue scale. RESULTS: Subjectively assessed jaw muscle fatigue caused a decrease of about 50% in the size of the late inhibition in the post-conditioning recording (ANOVA: p=0.001; Bonferroni contrasts: p<0.05). Full recovery to baseline values was already achieved at the first recovery recording. No significant differences were found between both sessions (ANOVA, p=0.677). CONCLUSION: Exercise-induced, subjectively assessed jaw muscle fatigue causes a reproducible, transient suppression in the size of the late inhibitory jaw reflex wave.