Older adults show elevated intermuscular coherence in eyes‐open standing but only young adults increase coherence in response to closing the eyes

Abstract

Understanding neural control of standing balance is important to identify age-related degeneration and design interventions to maintain function. Here, intermuscular coherence between antagonist muscle pairs around the ankle-joint during standing balance tasks was investigated before and after strength training. Ten young (18-31 years; YOUNG) and nine older adults (66-73 years; OLDER) stood on a force plate for 120 s with eyes open followed by 120 s with eyes closed before and after 14 weeks of strength training. Postural sway was quantified from centre-of-pressure displacement based on 3-D force moments. Electromyography (EMG) was recorded from the gastrocnemius medialis (GM), soleus (SOL) and tibilais anterior (TA) muscles of the right leg. Coherence between rectified EMG pairs (GM-TA, SOL-TA) was calculated for each 120 s epoch separately. Postural sway was lower in YOUNG compared to OLDER in eyes-open (6.8 ± 1.3 vs. 10.3 ± 4.7 mm s −1 , P = 0.028) and eyes-closed (10.9 ± 3.1 vs. 24.4 ± 18.3 mm s −1 , P = 0.032) tasks. For both muscle pairs, OLDER had more prominent common input over 4-14 Hzwith eyes open, but when the proprioceptive demand was enhanced in the eyes-closed task the YOUNG were able to further enhance their common input at 6-36 Hz (P < 0.05). Strength training reduced the instability from closing the eyes in OLDER but did not alter coherence.This may highlight a greater functional reserve in YOUNG than in OLDER and possible emerging proprioceptive degeneration in OLDER. However, the findings question the functional role of coherence for balance.

The effects of conscious movement processing on the neuromuscular control of posture

“…We observed a significant increase in IMC across all frequency ranges during the unstable compared to the stable condition. These effects are in line with previous studies that also observed increased IMC during tasks which challenge postural control e.g., standing position (e.g., tandem stance) or through inducing threats (e.g., standing at height; Boonstra et al, 2015;Danna-Dos-Santos et al, 2015;Walker et al, 2020). These findings indicate that IMC was reliably estimated in the current study.…”

EMG-EMG coherence during voluntary control of human standing tasks: a systematic scoping review

“…Furthermore, the difficulty in channeling the correct standing balance and the related neuromuscular activities varies depending on the available sensory inputs (Carver et al, 2006;Jeka et al, 2010). For example, more significant postural sway and specific neuromuscular activity while standing with eyes closed than with eyes open (Danna-Dos-Santos et al, 2015;Walker et al, 2020) has been reported. In addition, elderly adults (Nojima et al, 2018;Fujio and Takeuchi, 2021) and patients with stroke (de Haart et al, 2004) have a greater loss of standing balance in response to sensory disturbances than healthy young adults.…”

Age-Related Differences in Intermuscular Coherence EMG-EMG of Ankle Joint Antagonist Muscle Activity during Maximal Leaning

“…However, the neuromuscular system must significantly assist this process by actively modulating it to an appropriate level [ 2 ]. Successful integration of vestibular and somatosensory systems is required for optimal balance control, but age negatively affects the functioning of these systems [ 3 ]. An analysis that may help to explain this phenomenon is a simple calculation of the coherence of a pair of antagonistic muscles (tibialis anterior muscle and soleus muscle), which are relevant in investigating neuromuscular mechanisms controlling the ankle joint.…”

“…An analysis that may help to explain this phenomenon is a simple calculation of the coherence of a pair of antagonistic muscles (tibialis anterior muscle and soleus muscle), which are relevant in investigating neuromuscular mechanisms controlling the ankle joint. The relationships that exist between the muscles mentioned above have already been analyzed by a number of authors [ 2 , 3 , 4 ]. However, due to the complexity of the ankle joint stability problem, further exploration of this topic is still needed, if only due to the increase in life expectancy.…”

“…Beta band oscillations are clearly observed in EEG recordings from the cerebral motor cortex [ 29 ]. Previous scientific studies indicate significant beta band coherence between sensorimotor cortex and muscle contraction in both primates and human beings [ 3 ]. Other authors state that slow EEG oscillations delta band can contain neural information regarding the postural kinematics of the human body [ 30 ].…”