Effects of Concentric Unilateral Training Utilizing an Isokinetic Dynamometer on Functional Outcomes and Lower Limb Muscular Power in Subacute Hemiparetic Individuals: A Case Series

Abstract

Background. Stroke is a serious medical condition that is characterized by subsequent neurological deficits due to disruption in the brain vasculatures. Manifestation of neurological deficits varies between individuals and is highly dependent on the location, severity, and duration of the stroke. Neurological deficits and negative signs of upper motor neuron syndromes such as lower limb weakness, impaired inter-limb coordination, and greater fatigability may affect one’s rehabilitation outcome and ability to perform activities of daily living. Application of resistance training programs into post stroke (chronic and subacute) individuals’ exercise routine has been shown to increase functionality and improve both muscle function and mass. Unlike traditional resistance training exercises (e.g., free weights, weight stack machine), an isokinetic dynamometer is a safer and better option as it provides accommodating resistance that is equivalent to the force applied by the participant throughout a range of motion under a set angular velocity. Objective. The purpose of this study was to examine the effects of concentric lower limb isokinetic resistance training on tasks of functionality, muscular power, and neuromuscular activation and fatigue in individuals with sub-acute stroke (3-6 months). Method. Two participants were recruited through the Wascana Rehabilitation Centre and Regina General Hospital (Neuroscience Unit). Both participants completed four weeks of high intensity lower limb resistance training utilizing an isokinetic dynamometer. The program included hip flexion, knee flexion/extension, and ankle dorsiflexion/plantarflexion exercise at two different angular velocities (60°, 120°). Physiological and functional outcome testing was performed at baseline and again upon completion of the training program. Physiological testing was concurrently assessed using isokinetic dynamometry (muscular power) and surface electromyography (neuromuscular activation and fatigue) of the knee extensors and flexors. Functional outcome iii testing assessed gait velocity, gait endurance, balance, and transfer tasks. Results. After completion of the program, both participants demonstrated general improvements in paretic limb muscular power and time to peak power at both velocities in most of the tested muscles post-intervention. Although Participant 1 demonstrated higher neuromuscular activation in the knee flexors on his paretic side, both participants showed a general trend for decreased neuromuscular activation in most of the muscles tested post-intervention. Neuromuscular fatigability was decreased post-intervention in the paretic knee flexors for Participant 1 and in the paretic and non-paretic extensors for Participant 2; all other muscles showed either no change or an increase in neuromuscular fatigability post-intervention. Both participants improved their walking speed and endurance post-intervention, with the improvement in walking speed being deemed clinically important for Participant 2. No changes were found in dynamic balance ability, but the confidence in performing activities without losing balance improved in both participants. Stroke Impact Scale scores improved in almost all domains in both participants. Conclusion. Isokinetic-based, concentric-only resistance training of the paretic limb may have benefits in improving specific physiological and clinical outcomes in individuals with sub-acute stroke. Future studies are required to assess the influence of natural history on such improvements, compare the relative efficacy of concentric-only vs. eccentric-only isokinetic-based training programs, and determine whether a particular set of training parameters (e.g., duration, volume, intensity) leads to the best outcome for post stroke individuals.