Effect of Exercise on Gait Kinematics and Kinetics in Patients with Chronic Ischaemic Stroke

Introduction: In 2014, American Heart Association and American Stroke Association (AHA/ASA) issued exercise guidelines for stroke patients. Aim of the Study: To study the effects of an exercise programme based on AHA/ ASA guidelines, on gait kinematics and kinetics in patients with chronic ischemic stroke. Materials and Methods: Twelve stroke patients, 67.33 ± 9.14 years old, followed an 8-week exercise programme, with 3 hourly sessions per week, consisting of strength, endurance and flexibility training, as well as neuromuscular activities. Patients’ gait kinematics and kinetics were evaluated before and after the intervention using a 3-dimensional gait analysis system. Results: In most cases, patients in the intervention group showed significant increase or no change in gait kinematics, significant increase in joint moments at the anterior-posterior plane during support phase, and non-signi-ficant change in the frontal and transverse planes kinetics. Conclusions: Exercise prevented further deterioration and/or led to improved walking pattern.


Introduction
It is estimated that one in 5 women and one in 6 men will sustain a stroke up to the age of 75 years [1]. The main purpose of rehabilitation in such patients is to achieve the maximum possible personal performance, physical and psychologi-cal, with the ultimate goal of regaining a level of functional independence that will allow them to be re-integrated into social life as much as possible [2]. However, stroke patients often adopt a sedentary lifestyle [3] [4] [5] [6]. This may be attributed to 1) factors associated with patients themselves, such as depression, lack of interest or motivation, decreased perception, decreased confidence, ignorance that exercise is possible and desirability and fear of falls, of a new stroke or other undesirable effects; 2) practical factors, such as lack of support from family or other social actors, inability to access exercise sites, inadequate public transport, health professionals' ignorance of the availability of physical activity services; 3) financial cost [7] [8] [9] [10] [11]. Conversely, exercise in groups may improve patient motivation [12].
In 2014, the council of the American Heart Association and the American Stroke association (AHA/ASA) revised the exercise recommendations for stroke patients at all stages of their recovery [13]. Therefore, the aim of this study was to assess the effect of an exercise programme based on these recommendations on gait kinematics and kinetics of ischaemic stroke patients in the chronic phase of recovery.

Sample
Twelve patients, seven men and five women, aged 64.42 ± 8.59 years, who were hospitalised due to stroke in a General Hospital participated in the study. Nine of them had mild right paresis and three left paresis. Patients' characteristics are presented in Table 1. The study was approved by the institutional ethics committee and patient gave their informed consent.

Procedure
Patients were randomised into 2 groups: the intervention group and the control group. The initial assessment of kinematic and kinetic gait parameters was performed using a 3-dimensional gait analysis system. Patients of the intervention group also underwent medical exams (clinical examination by a cardiologist, chest x-ray, electrocardiogram, and echocardiogram).
Then, patients in the control group were instructed to continue their usual daily activities, while those in the intervention group followed an 8-week exercise programme. At the end of this period, patients were re-evaluated using the gait analysis system.

Assessment
A motion analysis system consisting of 6 infrared cameras (Vicon MX 0306012) was used. Cameras were arranged in a circular configuration 3 meters above the ground and had a shooting speed of 100 Hz. Ιmages were digitised with Nexus 1.3 106 and Polygon software packages, while kinematic data processing and analysis was carried out using MatLab software. The motion analysis system was synchronised with an acquisition and analysis system of ground reaction forces using Vicon's Nexus 1.3 106 software. The recording and analysis system of ground reaction forces consisted of 2 piezoelectric force plates (Kistler, type 9281Β11 and 9281CA, respectively), 2 load amplifiers and an analogue-to-digital converter. Digital signal acquisition, processing and analysis was carried out using Nexus 1.3 106 and Polygon software packages.
For the acquisition of temporal gait parameters, an electronic timing system was used, consisting of an electronic timer and 2 pairs of photocells (reflective markers). The reliability of the method in assessing the mechanical gait parameters in patients with stroke has been demonstrated [14]. Given that kinematic and kinetic gait parameters are related to gait speed [15], it was decided to maintain patients' gait speed constant between the initial and the final measurement. For this purpose, an electrically driven stick was used, moving steadily and at a speed equal to each patient's normal walking speed, which was calculated using six trial attempts before the initial assessment. Then, patients were instructed to move at a steady distance behind the stick.
Kinematic parameters studied were hip flexion-extension angle, hip abduction-adduction angle, hip internal-external rotation angle, knee flexion-extension angle and ankle dorsal-plantar flexion angle. Kinetic parameters studied were hip flexion-extension moment, hip abduction-adduction moment, hip internal-external rotation moment, knee flexion-extension moment and ankle dorsal-plantar flexion moment.

Intervention
Patients were divided into 2 groups depending on the level of gait recovery. Each

Statistical Analysis
Statistical analysis was performed using Statistical Package for Social Sciences 23 (SPSS Inc., Chicago, IL). We compared the initial and the final evaluation of each patient individually. Root mean squares (RMS) of each gait parameter were calculated for each 10% of the gait cycle. Differences between the RMS values between initial and final measurements were ascertained by repeated-measures Analysis of Variance (ANOVA), with one repeated factor, lower limb (paretic-non paretic) and time interval (initial and final measurement). Significance was defined as 5% (two-tailed p < 0.05).  Table 3 and Table 4 show the distribution of patients according to any changes in the RMS values of each parameter. Most patients in the control group exhibited significant reductions in gait kinematics, and non-significant changes in gait kinetics in both lower limbs. Conversely, most patients in the intervention group showed significant increase or no change in joints' angles. As far as joint moments are concerned, most patients showed significant increases in all joints at the anterior-posterior plane, and non-significant changes in the frontal and transverse planes. Figure 1 and Figure 2 show the mean waveforms of each gait parameter, both for the intervention and the control group, during the initial and final measurement. There was an obvious increase in the joints range of motion in the sagittal plane during the final measurement, both in the paretic and non-paretic lower limbs, throughout the movement path in the intervention group. Similarly, there was an increase in abduction and adduction hip movement as a result of the intervention. In the control group, however, there was a decrease in the range of motion of the above joints during the final measurement. As regards kinetic parameters, changes appear purely in the support phase, during the first 60% of the walking cycle.

Discussion
The main findings of this study include significant reductions of gait kinematics in the control group, as opposed to significant increases or no changes, excluding hip movement at the transverse plane (internal-external rotation), in the intervention group. In the ankle joint, intervention group patients showed increased dorsiflexion during the final measurement. This finding points to increased strength of ankle dorsiflexors, and it also suggests the inhibition of the simultaneous plantar flexors' activation (reduction in spasticity). Furthermore, it may be an indication of greater balance, because patients did not choose an abnormal flat landing of the foot during initial foot contact to achieve increased base of support [17]. In contrast to patients in the intervention group, those in the control group exhibited more limited ankle dorsiflexion during the support phase, which indicates worsening of the gait pattern over time.
In kinetic parameters, most control patients had no significant changes, both in the paretic and the non-paretic lower limb. On the contrary, in the intervention group, there was a significant increase in mean moment values, both in the paretic and the non-paretic lower limb during movements at the anteroposterior plane in all three joints. This change reflects patients strengthening.
On average waveforms of moments, it was not possible to reflect changes Open Journal of Therapy and Rehabilitation made at individual level due to the different walking patterns of each patient.
Each patient responded in his/her own special manner to the intervention programme. The different moment waveform patterns in stroke patients have been highlighted by Kim & Eng [18]. In their study, moment waveforms that followed the normal pattern of healthy adults were recorded, as well as many variations.
The different patterns of moments were correlated with gait speed. The same conclusion was drawn by Olney and Richards [17], who grouped these patterns with those based of patients' gait speed.
However, looking at the moment waveforms, it can be observed that for all joints in all the 3 planes in both groups, there were no significant changes between the initial and the final measurements in the swing phase, both in the paretic and non-paretic lower limb. However, small deviations were evident in the support phase. Therefore, the support phase was identified as the one that patients can utilise, through muscle strength increase, to alter their gait.
Our findings are concur with Teixeira-Salmela et al. In their study, the effect of a 10-week aerobic exercise and strengthening programme in patients with chronic stroke led to gait pattern improvement and an increase in selected kinematic and kinetic parameters [19].
The limitations include the small number of patients in each group, which in combination with the heterogeneous clinical feature of patients, did not allow group statistics to be performed. Therefore, to safely generalize the results it is advisable to consider a larger sample of patients. Another limitation was the lack of follow-up of patients beyond the two measurements, to record the extent to which the positive effect of exercise lasted over time. The final limitation relates to heterogeneity in the clinical features of stroke patients, which led to the absence of a common gait pattern to the whole patients. This, in combination to the small number of patients that met the inclusion criteria in the study, did not allow the use of group statistics and the direct comparison of patients in the intervention group with those in the control group.

Conclusion
In conclusion, gait kinematics was significantly increased in most patients in the intervention group. These changes were related with significant increases in gait kinetics during the support phase. It would now be useful to extend the observations to physical condition (spasticity, weakness, clinical characteristics of gait, etc.) in a larger patient sample.