Locomotor training with body weight support in SCI: EMG improvement is more optimally expressed at a low testing speed

Abstract

Study design: Case series. Objectives: To determine the optimal testing speed at which the recovery of the EMG (electromyographic) activity should be assessed during and after body weight supported (BWS) locomotor training. Setting: Tertiary hospital, Sint Maartenskliniek, Nijmegen, The Netherlands. Methods: Four participants with incomplete chronic SCI were included for BWS locomotor training; one AIS-C and three AIS-D (according to the ASIA (American Spinal Injury Association) Impairment Scale or AIS). All were at least 5 years after injury. The SCI participants were trained three times a week for a period of 6 weeks. They improved their locomotor function in terms of higher walking speed, less BWS and less assistance needed. To investigate which treadmill speed for EMG assessment reflects the functional improvement most adequately, all participants were assessed weekly using the same two speeds (0.5 and 1.5 km h − 1 , referred to as low and high speed, respectively) for 6 weeks. The change in root mean square EMG (RMS EMG) was assessed in four leg muscles; biceps femoris, rectus femoris, gastrocnemius medialis and tibialis anterior. Results: The changes in RMS EMG occurred at similar phases of the step cycle for both walking conditions, but these changes were larger when the treadmill was set at a low speed (0.5 km h − 1 ). Conclusion: Improvement in gait is feasible with BWS treadmill training even long after injury. The EMG changes after treadmill training are more optimally expressed using a low rather than a high testing treadmill speed. Initial BWS systems were based on counterweights, 2 while recent versions incorporate dynamic BWS, which accommodates the vertical displacement of the center of mass during gait. 3 Both types have been successful in the gait rehabilitation of patients with SCI. 2,3 Even though functional tests (such as walking speed) are able to demonstrate changes in behavior, they do not directly reflect the motor output of the locomotor circuitry. Therefore, electromyography (EMG) is more recently used to document the progress made during training to better understand the underlying mechanisms of improvement. There are different ways to measure EMG changes during training. One can measure EMG as the performance level of the SCI person improves. 4 This means that one measures EMG activity at higher walking speeds and lower BWS as training progresses. The disadvantage of this method is that one cannot clearly distinguish between the influence of the training effect and the changing walking speed 5 and BWS 6,7 on the EMG muscle activity. The other strategy

Rehabilitation Strategies after Spinal Cord Injury: Inquiry into the Mechanisms of Success and Failure

“…Amelioration in the locomotor patterns of incomplete SCI individuals following BWST includes an increase in EMG activity and a decrease in burst duration and cocontractions. 176,177 Gorassini and colleagues point out that the improvement in EMG activity is greater in muscles that receive more cortical projections (i.e., tibialis anterior [TA]and hamstrings), compared with muscles mainly under the influence of local spinal circuits (i.e., soleus). 176 It is argued that there may be a reinforcement of the remaining cortical and/or brainstem projections, a point that also is supported by the fact that the individuals more responsive to BWST were the ones with the highest remaining motor score for lower limb muscles.…”

Tapping into rhythm generation circuitry in humans during simulated weightlessness conditions

“…Body weight support systems coupled with robotic devices or pharmacologic treatments are now often used in the rehabilitation practice to assist locomotor recovery in individuals with neuromotor disorders (Dietz, 2009 ; Sale et al, 2012 ; Hubli and Dietz, 2013 ; Valentin-Gudiol et al, 2013 ; Meyns et al, 2014 ; Moraru and Onose, 2014 ). There is still limited evidence of the efficacy of treadmill interventions with body weight support in some injured populations due to the complex nature of the control of locomotion, compensatory strategies, and plasticity of neuronal networks (Grasso et al, 2004 ; Picelli et al, 2013 ; Valentin-Gudiol et al, 2013 ; Swinnen et al, 2014 ; Sylos-Labini et al, 2014b ).…”

Dose-Response Outcomes Associated with Different Forms of Locomotor Training in Persons with Chronic Motor-Incomplete Spinal Cord Injury

“…29,30 Subsequently, there is evidence that in persons with MISCI, muscle activity is more optimal at lower speeds resembling self-selected speed. 31 In contrast, a recent study demonstrated that muscle activity increased as training intensity (that is, speed) increased. 32 However, walking was tested only on the treadmill, and therefore it is not known whether this translates to improvements in real-world overground walking.…”