Tibialis anterior muscle fascicle dynamics adequately represent postural sway during standing balance

Abstract

To maintain a stable, upright posture, the central nervous system (CNS) must integrate sensory information from multiple sources and subsequently generate corrective torque about the ankle joint. Although proprioceptive information from the muscles that cross this joint has been shown to be vital in this process, the specific source of this information remains questionable. Recent research has been focused on the potential role of tibialis anterior (TA) muscle during standing, largely due to the lack of modulation of its activity throughout the sway cycle. Ten young, healthy subjects were asked to stand normally under varying conditions, for periods of 60 s. During these trials, intramuscular electromyographic (EMG) activity and the fascicle length of three distinct anatomical regions of TA were sampled synchronously with kinematic data regarding sway position. In the quiet standing conditions, TA muscle activity was unmodulated and fascicle length changes in each region were tightly coupled with changes in sway position. In the active sway condition, more EMG activity was observed in TA and the fascicle length changes were decoupled from sway position. No regional specific differences in correlation values were observed, contrasting previous observations. The ability of the fascicles to follow sway position builds upon the suggestion that TA is well placed to provide accurate, straightforward sensory information to the CNS. As previously suggested, through reciprocal inhibition, afferent information from TA could help to regulate plantar flexor torque at relevant phases of the sway cycle. The proprioceptive role of TA appears to become complicated during more challenging conditions.

Tibialis anterior tendinous tissue plays a key role in energy absorption during human walking

“…To the best of our knowledge, the variation in fascicle length changes between the superficial and deep regions of the TA during gait have not previously been reported. Previous studies quantifying fascicle length changes illustrate minimal differences between regions during isometric contractions (Maganaris and Baltzopoulos, 1999;Raiteri et al, 2016) and quiet standing (Day et al, 2013). Here, we show the overall pattern and timing of fascicle length changes between the two regions were similar; however, the normalised fascicle length change magnitude across the gait cycle was notably different, such that the fascicles of the deep region typically exhibited greater length changes.…”

A reduction in compliance or activation level reduces residual force depression in human tibialis anterior

“…We speculate that a ~1.5‐2 mm increase in fascicle shortening in the High‐Mod compared with the Mod condition would have resulted in a detectable level of rFD with our measurement system, since we found a 4% increase in steady‐state dorsiflexion force following a mean reduction in fascicle shortening of 1.7 mm. We also believe that sub‐millimeter fascicle length changes were detectable with our system based on previously reported length changes in the same muscle during postural sway and passive rotations …”

Comparison of the electromyographic activity of the tibialis anterior and gastrocnemius in stroke patients and healthy subjects during squat exercise

“…This may explain the overactivity in the paretic TA of the stroke patients during the downward and maintenance phases of the squats, because the TA may contribute to inversion of the foot accompanied by a heel lift. According to Day et al, in tasks of increasing postural demand, where greater TA activation is required 15 ) . Therefore, impairment of balance in hemiplegic patients may be influence TA muscle activity to maintain posture.…”