Comparison of corticomuscular coherence under different balance paradigms in individuals with and without forward head posture

Abstract

A prospective case control investigation was conducted to assess corticomuscular coherence (CMC) under different balance conditions in order to identify alterations that may arise due to forward head posture (FHP). Sixty-four participants (between the ages of 18-25) were recruited for this study. Participants were free from any musculoskeletal symptoms and matched for relevant demographic variables. Participants were assessed for FHP using the craniovertebral angle (CVA) and separated into either the normal head posture (NHP) group by CVA > 50° or the FHP group by CVA < 50°. Participants were evaluated using the Biodex balance system while both EEG and EMG signals which were acquired simultaneously to investigate CMC. Balance was investigated under four conditions increasing in challenge: (1) standing with eyes open, (2) standing with eyes closed, (3) unstable standing with eyes open with the Biodex set on level 8, and (4) unstable standing with eyes closed with the Biodex at level 8. In addition to recording delta, beta, theta, alpha, and gamma waves, we calculated both peak and average coherence values from the CMC analysis. Statistically significant differences were identified for the FHP group vs. the NHP group for both peak (p < .001) and average CMC values (p < .001) and for the interaction of balance difficulty (stage 1 vs. stage 4), p < .01. Similarly, all brain waves (delta, beta, theta, alpha, and gamma) demonstrated statistically significant differences between the NHP and FHP groups (p < .001) and for increasing balance difficulty across the four stages, p < .05. This study demonstrates that FHP is associated with a significant elevation of CMC, a unique compensatory burden on the brain, particularly during physically challenging balance tasks.

Keywords: Balance; Corticomuscular coherence; Forward head posture; Sagittal balance.

Fig. 1

Boxplots for the craniovertebral angle (CVA) for the normal head posture (NHP) group compared to the forward head posture (FHP) group.

Fig. 2

Interaction plot for peak CMC. FHP: forward head posture group. NHP: normal head posture group.

Fig. 3

Interaction plot for average CMC.

Fig. 4

Interaction plot for Gamma, Beta, Alpha, Theta, and Delta CMC.

Fig. 5

Brain activity heat maps for normal head posture (NHP) vs. forward head posture (FHP) across 5 frequency bands and 4 balance stages (1–4 is increasing task difficulty). These heat maps were obtained using the NeXus Q-32 device from two representative participants in our study: one from the NHP group and one from the FHP group.

Fig. 6

Violin plots illustrate inter-subject variability in peak and average CMC values across balance difficulty stages and head posture groups (FHP vs. NHP).

Fig. 7

Violin plots illustrate inter-subject variability in the 5 frequency band values across balance difficulty stages and head posture groups (FHP vs. NHP).

Fig. 8

Boxplot comparing stability index (sway values) between the FHP and NHP groups.

Fig. 9

(A) The patient stands barefoot in a relaxed position with arms by their side on the Biodex Balance System ^™ SD with the EEG cap fastened on their head and the 2 channels of EMG attached to the leg. (B) Two EMG channels were used each consisting of an active (red) and a reference (black) electrode. The electrodes were placed over the TA and GL based on SENIAM guidelines.

Fig. 10

Flow chart of the implemented methodology to estimate magnitude CMC between EEG and EMG signals during paradigms.