Comments on the Functional Asymmetries of the Lower Extremities

Abstract

Several tasks have been used to establish laterality in the lower extremities, but most of them are not satisfactory. The lower extremities are involved in various posturomotor, locomotor and operant activities, and several kinds of differentiated bilateralizations of the lower limbs can be identified. A distinction between leggedness and footedness seems warranted. The complexity of the functional asymmetries of the lower extremities requires new methods in both research and clinical testing, with elecctrophysiological procedures as a promising approach. Available evidence indicates that the functional asymmetries of the axial neuromotor mechanisms have to be considered in the study and the assessment of those of the lower extremities.

Limb dominance changes in walking evolution explored by asymmetric correlations in gait dynamics

“…These degrees of freedom are responsible for the plasticity seen in the human motor system, and allow the person to adapt to constantly changing environmental constraints. On the other hand, different studies have suggested that, similar to variability, left-right asymmetries may be also the norm for healthy conditions [4,5,12,13]. It seems that able-bodied gait is naturally asymmetrical and this asymmetrical behavior limbs could be associated with the different contributions of the lower limbs in carrying out propulsion and stabilization tasks [1].…”

“…An α < 0.5 signifies antipersistent correlations (a large stride interval is more likely to be followed by a small one and vice versa over different time scales). As made by Hausdorff et al [25,26], given the relatively small sampling period of about 5-6 min (about 270 gait cycles), the analyzed scales range was limited to s ∈ [5,25]. This region was chosen as it provides a statistically robust estimate of gait dynamics correlations that are mostly independent of finite size effects (length of data).…”

“…[1]. A common approach for gait asymmetry interpretation is based on the support and mobility associated with each limb [4,5]. An important advance was the evidence that one lower limb is mainly responsible for support and body weight transfer during walking while the contralateral limb contributes more to propulsion [6,7].…”

A test of the functional asymmetry hypothesis in walking

“…When considered together, the existing research considering the concept of functional asymmetry is inconclusive [2,3,[8][9][10][11]20,21], and conflicting opinions regarding this issue may stem from several different factors. First, variables that are not directly linked to support or propulsion (e.g., medial-lateral GRF) have been used to imply functional asymmetry during gait [20].…”

“…However, a close examination of several of the cited studies suggests that this conclusion may be premature. For example, some studies that have been cited in support of functional asymmetry in able-bodied gait did not involve walking [8][9][10]. Moreover, data in an oft-cited study [11] contradict an apparent typographical error in the abstract, giving the false impression that the results support the concept of functional asymmetry.…”