Forward and backward walking share the same motor modules and locomotor adaptation strategies

Abstract

Forward and backward walking are remarkably similar motor behaviors to the extent that backward walking has been described as a time-reversed version of forward walking. However, because they display different muscle activity patterns, it has been questioned if forward and backward walking share common control strategies. To investigate this point, we used a split-belt treadmill experimental paradigm designed to elicit healthy individuals’ motor adaptation by changing the speed of one of the treadmill belts, while keeping the speed of the other belt constant. We applied this experimental paradigm to both forward and backward walking. We analyzed several adaptation parameters including step symmetry, stability, and energy expenditure as well as the characteristics of the synergies of lower-limb muscles. We found that forward and backward walking share the same muscle synergy modules. We showed that these modules are marked by similar patterns of adaptation driven by stability and energy consumption minimization criteria, both relying on modulating the temporal activation of the muscle synergies. Our results provide evidence that forward and backward walking are governed by the same control and adaptation mechanisms.

Locomotor adaptations: paradigms, principles and perspectives

“…A recent study has replicated an adaptation behavior similar to the one observed during split-belt treadmill walking using motorized shoes [46]. As we will see in detail in the following sections, split-belt walking perturbs kinematic and kinetic symmetry [47] and hampers stability [48,49] and energy consumption [50]. Other environmental paradigms simulate walking environments that present expected or unexpected unevenness [51][52][53], compliancy [54,55] or sudden destabilizing changes [56,57].…”

“…Both components of adaptations, and the adaptation process in general, are affected by ageing, following the effect that ageing has on the underlying neural mechanisms controlling the reactive and predictive components of locomotion (for a comprehensive review on this topic see [87]). Exponential adaptive responses have been observed in the kinematics [42,72,88,89], the kinetics [90], the muscular activations [49,70] and the energy consumption [50,91].…”

Effect of Backward and Forward Walking on Lower Limb Strength, Balance, and Gait in Multiple Sclerosis: A Randomized Feasibility Trial

“…5 phase percentage 14 in these populations. Although motor learning theory requires repetition of the task that is being learned, FW and BW share the same central pattern generator, 17 muscle synergy modules, 18 and common control strategies, 18 allowing adaptations made from BW to translate to FW. Training in BW may address balance and gait impairments by improving postural stability, 19 increasing neural and muscular activity, 20,21 and increasing metabolic response 19,20 due to the novelty, increased complexity, and longer duration of muscle activity 21 during backward movement; however, limited studies have reviewed BW in persons with MS.…”

“…The current literature in other special populations (ie, Parkinson disease, stroke, cerebral palsy) suggests that BW is a useful intervention to improve spatiotemporal gait parameters and balance. Backward walking is a novel task that can challenge the body differently than FW while still training the same central pattern generator, 17 muscle synergy modules, 18 and common control strategies. 18 Weakness affects 70% of persons with MS, 26 which can lead to gait changes and balance deficits, so studying this intervention in persons with MS is vital, as these deficits can lead to an increased risk of falls, which can lead to many negative consequences (ie, injury, fear of falling, decreased physical activity, decreased activities of daily living).…”

“…Backward walking is a novel task that can challenge the body differently than FW while still training the same central pattern generator, 17 muscle synergy modules, 18 and common control strategies. 18 Weakness affects 70% of persons with MS, 26 which can lead to gait changes and balance deficits, so studying this intervention in persons with MS is vital, as these deficits can lead to an increased risk of falls, which can lead to many negative consequences (ie, injury, fear of falling, decreased physical activity, decreased activities of daily living). Although this study did not demonstrate greater improvement from BW compared with FW, positive changes were observed and the intervention was well tolerated with a high adherence rate, supporting investigation of the use of BW as another treatment for persons with MS.…”