BACKGROUND AND PURPOSE
Stroke is a leading cause of serious, long-term disability throughout the world.1 As many as two-thirds of individuals are unable to walk or require physical assistance to walk immediately after their stroke and a third of individuals still require assistance or are unable to walk 3 months poststroke.2 These chronic limitations in mobility can lead to a decrease in endurance and fitness reserve that can also negatively impact function.3 Since walking ability and endurance have been shown to be important predictors of independence and community mobility,4,5 it is essential that clinicians find effective and affordable interventions for improving walking ability and fitness in persons with stroke.
Recent studies have emphasized the use of intensive task-specific forms of activity such as treadmill-based locomotor training that can provide both gait and endurance training in a controlled and systematic fashion.6–12 However, one of the recognized limitations of treadmill training is the physical demands it can place on both the therapist and the participant during the intervention. This is especially true when training more severely impaired individuals who may require the use of body-weight support and additional staff to provide appropriate cueing and manual facilitation of the lower extremities and trunk. In such cases, treatment time and intensity may be limited by therapist/participant fatigue and may be cost prohibitive in cases where reimbursement rates (eg, Medicare and Medicaid) do not adequately account for the increased time and staffing associated with this type of training.13 Another limitation of treadmill-based locomotor training is that it may be difficult to perform safely and independently in home and community settings.
To address the limitations of using a treadmill for locomotor training, some researchers have investigated alternatives such as robotic-assisted locomotor training14,15 and electromechanical gait training6–18; the latter is a motorized elliptical machine that adjusts the amount of assistance based on the user's effort level. These interventions rely on the use of motorized equipment to move the lower extremities to reduce the work of both the therapist and the patient and allow for increased practice opportunities. To date, the few studies evaluating the effectiveness of these interventions have demonstrated mixed results.15–19 A recent larger, multicenter, randomized, controlled trial found that conventional locomotor training and manually assisted treadmill training were more effective than robotic-assisted treadmill training.14 The studies using the motorized elliptical machine have included only individuals with subacute stroke, and the feasibility of using a nonmotorized elliptical training in individuals with chronic stroke have not previously been investigated.16–18 As with many technologies, another significant limitation is the lack of availability and prohibitive cost of this type of equipment for most settings.
The primary purpose of this case series was to assess the feasibility of using a commercially available nonmotorized elliptical machine to improve functional walking capacity in individuals with chronic stroke. If this type of training is safe and effective, elliptical training could offer an alternative to treadmill or robotic-assisted gait training. More important, elliptical training might provide an affordable form of training that could be used safely in home and community settings on a long-term basis.
Participant Description and Selection
Three individuals with chronic stroke were recruited from the community by using contacts with local support groups as well as referrals from local physical therapists. Participants 1 and 2 walked regularly in the community, while participant 3 walked in the home, using a cane, but used a wheelchair for community mobility (see Supplemental Digital Content video 1, Participant 3 Overground Walking, which demonstrates typical walking function in participant 3, http://links.lww.com/JNPT/A4). Specific characteristics and demographics for each of the participants are given in Table 1. Inclusion criteria were a confirmed diagnosis of chronic (>6 months) first-time supratentorial stroke, impaired walking function (eg, decreased walking speed, use of an assistive device and/or orthotic) but able to walk at least 10 m with no more than contact guard assistance. All participants had a minimum score of 24/30 on the Modified Mini-Mental Status Exam20 and provided a signed medical release from their primary care physician indicating that it was safe to participate in a moderate-intensity aerobic training program. Participants were free of significant comorbidities such as recent myocardial infarction, acute inflammation, recent surgery, painful orthopedic conditions, and the presence of other neurological conditions. Before training, each signed an informed consent that had been approved by the University of Dayton institutional review board.
Training was performed using a commercially available elliptical machine (True TSXa, TRUE Fitness Technology, St Louis, MO) (see Figure). This device was chosen because it has a number of unique features that make it practical for training individuals with physical impairments: (1) A central drive mechanism improved the ease of mounting and dismounting from the back of the unit and permitted placement of a platform to reduce the step height or a chair for rest breaks; (2) an electronically controlled adjustable step length of 41 to 53 cm (17-26 in) allowed us to match the comfortable step length for each participant and to increase this length as tolerated during training; (3) the distance between the pedals is 5 cm, which approximates normal step width more closely than most elliptical machines (generally > 10 cm); (4) sturdy rails on each side of the unit allowed participants to use their upper extremities more effectively for support during training and when mounting/dismounting the unit; and (5) a wide range of workloads (10-300 W) and integrated telemetry for heart rate (HR) monitoring.
FIgure. Elliptical t...Image Tools
During training sessions, a harness apparatus (M.A.S.S. Rehab LLC, Clayton, OH) was used to minimize the risk of falling and to reduce anxiety. This harness system was mounted to the ceiling, using a single eye-bolt attachment. Body-weight support could be adjusted if needed using a simple rope-and-pulley system. This system provided a 3-to-1 mechanical advantage when lifting the participant and used a cam cleat to lock or release the rope so the amount of body-weight support could be easily adjusted during training.
All training and testing took place at the University of Dayton's Doctor of Physical Therapy Research Laboratory. On the initial visit, a maximum training HR value was determined for each participant based on the HR reserve (HRR; also known as the Karvonen method) method.21 The maximum training value was set at 75% of HRR method. Participants were instructed in the use of the 10-point Borg category-ratio scale22 and instructed not to exceed an exertion level of 5. These exercise intensity cutoff values were used so that participants would not exceed a “moderate to strong” level of exercise intensity as outlined by the American Heart Association and American College of Sports Medicine.23 Prior to each training session, the participants sat quietly for 5 minutes and resting blood pressure (BP) and HR were recorded. Participants were also fitted with an HR monitor and safety harness. Participants who wore ankle-foot orthoses for walking were asked to remove them during training.
The duration of the training sessions was progressively increased with the goal of achieving a target training duration of 20 minutes of uninterrupted elliptical training. An additional goal was to maintain a stepping cadence of 100 to 110 steps per minute (50-55 rpm) to simulate normal overground walking cadence. If a participant was unable to complete 20 minutes of training initially, attempts were made on each subsequent session to increase the total training time while giving as many rest breaks as needed. If a participant was able to achieve 20 minutes of uninterrupted training while maintaining the predetermined exercise parameters, then the resistance level of the elliptical machine was increased. All participants trained for 8 weeks; participants 1 and 2 trained 3 times per week, while participant 3 trained only 2 times per week because of scheduling difficulties (see Supplemental Digital Content video 2, which demonstrates typical performance on the elliptical machine for participant 3, http://links.lww.com/JNPT/A5). The training parameters and progression for each participant are displayed in Table 2.
At the start of each training session, participants adjusted the step length to comfort and performed a 1- to 3-minute warm-up at 30 to 40 rpm at the lowest level of resistance. Following the warm-up, participants attempted to achieve a cadence of 50 to 55 rpm while maintaining an HR 75% of HRR or less and a perceived exertion of 5 or less on the Borg scale. If they exceeded either the HR or perceived exertion threshold, then they were asked to reduce their effort or stop and rest in either a standing or sitting position until HR and perceived exertion returned to acceptable levels. To increase training time while maintaining the appropriate training parameters, the therapist could reduce the training workload by grasping the moving hand bars and providing physical assistance as needed. Blood pressure values were assessed immediately after each training session. During the first several sessions, BP was also assessed during the rest breaks to ensure a normal exercise response. To begin training after a rest break, participants were required to have systolic pressure less than 180 mm Hg, diastolic pressure less than 110 mm Hg, and HR less than 100 beats per minute. During and immediately following the training session, systolic pressure less than 200 mm Hg and diastolic pressure less than 110 mm Hg were considered the safe limits. If a participant were to exceed any of these values, he would be discontinued from the training program and his physician would be contacted.
Originally, we had planned to encourage the use of the moving hand bars of the elliptical machine. However, during training, none of the participants chose to use the moving hand bars initially. Instead, they preferred to hold on to the stationary handrails for support. All of our participants had sufficient function in the involved upper extremity to maintain a grip on the stationary rails without assistance. The authors decided not to encourage the use of the moving hand bars and instead to err on the side of caution and protection of involved upper extremity. During the initial phase of training, we found it helpful to secure the forefoot of the involved foot with a Velcro (Velcro USA Inc, Manchester, NH) strap. However, no participant required the strap by the end of the training intervention.
As mentioned previously, participants wore a harness during all training. Initially we intended only to use the harness for safety purposes. However, as training progressed, we found it beneficial to provide some body-weight support to maintain proper form and postural control especially as the participants fatigued during the course of a training session. While we did not have an accurate method for measuring the amount of body-weight support provided, on the basis of previous clinical experience, we estimate that the amount of support was less than 20% of body weight.
All outcome measures were assessed 1 week before initiating training and within 1 week of completing the training intervention. Walking speed was determined by measuring the time (in seconds) required for participants to traverse the middle 10 m of a 14-m walking course.6 Walking speed was calculated for both habitual and fast-paced walking; 2 trials at each pace were recorded and averaged. During the fast-paced walking, participants were given the instruction to “walk as fast as you possibly can while remaining safe.” Walking speed has been shown to have good test-retest reliability (ICC = 0.86, 95% CI = 0.68-0.94) in persons with stroke.24
Walking endurance was evaluated using the 6-minute walk test (6MWT). This was accomplished by having the participants walk an oblong course around 2 cones placed 18 m apart.6 The participants used their preferred assistive device and lower extremity orthosis if needed and were given standardized verbal cues and encouragement every minute. The total distance covered was recorded. Heart rate and BP were recorded before and after the test. The 6MWT has shown acceptable reliability in persons with stroke (ICC = 0.74).25
Balance and functional mobility were assessed using the Berg Balance Scale (BBS) and the Timed “Up & Go” test (TUG). The BBS is a task performance test consisting of 14 items of increasing difficulty, which are scored using a 5-point ordinal scale (0-4).26 The maximum possible score is 56, with lower scores indicating more impaired balance. The BBS has demonstrated excellent test-retest reliability (ICC = 0.98) and validity in persons with stroke.27 The TUG documents the time required for the participant to stand from a standard armchair, walk 3 m around a cone using their preferred assistive device, and return to sitting in the chair.28 This test has excellent reliability (ICC = 0.95, 95% CI = 0.84-0.99) and concurrent validity in individuals with chronic stroke.29
Pre- and posttraining values for each participant are reported in Table 3. Participants 1 and 2 were scheduled to train 3 times per week for 8 weeks (24 sessions); they completed 20 and 21 of their sessions, respectively. Participant 3 was scheduled to train 2 times per week for 8 weeks (16 sessions) and completed 11 training sessions. All missed visits were due to either weather or unexpected scheduling conflicts. No adverse events were encountered during testing or training.
There were only small variable changes in habitual (±6%) and fast (2%-5%) gait speeds for all participants (Table 2). None of the participants demonstrated changes that approached or exceeded 0.30 m/s, which is considered to be the minimal detectable change at the 90% confidence level (MDC90) for persons with stroke.24
Participants 1 and 2 showed minimal change in the 6MWT (1%-2%). Participant 3, who had the poorest initial 6MWT performance, demonstrated a 25% improvement (26 m) following training. However, none of the changes in the 6MWT exceeded the MDC90 (54 m) for individuals with stroke.30
Balance and Functional Mobility
Participant 1 demonstrated an 8-point improvement in BBS performance that exceeded the MDC90 (6 points) for the BBS when used with persons poststroke.31 Participants 2 and 3 also showed improvements in their BBS scores, 5 and 4 points, respectively, but did not exceed the MDC90. All participants demonstrated improvements in TUG performance (5%-15%).
Effects of Elliptical Training on Gait Speed
To date, no studies have evaluated the effects of a commercially available, nonmotorized elliptical machine on gait speed in persons with chronic stroke. Our results suggest that training on an elliptical machine does not appear to be associated with increased gait speed. Several studies have investigated the effects of training on a motorized elliptical machine in persons with acute and subacute stroke.16–18 Tong et al17 found significantly greater improvements (P < 0.001) in gait speed after 4 weeks of 5 days per week training by using the motorized elliptical machine (mean gain of 0.47 m/s) compared with conventional gait training (mean gain of 0.24 m/s) and these improvements were maintained at a 6-month follow-up.18 In a randomized crossover trial, Werner et al16 found significant improvements in walking speed that were similar to body-weight-supported treadmill training (mean gain of 0.20 m/s, P < 0.05) when using a motorized elliptical machine (mean gain of 0.24 m/s, P < 0.05). Our results may differ from those of studies using a motorized elliptical machine in several ways including the use of nonmotorized elliptical machine, and differences in training dose, baseline gait speed, and chronicity of stroke. The training dose in prior studies was 5 days per week, while our participants trained only 2 to 3 days. Our participants demonstrated higher baseline gait speeds (0.34-0.98 m/s) relative to participants in previous studies (mean of 0.19 m/s). Our participants had chronic stroke while the other studies involved participants with acute and subacute stroke. Given these differences, participants in the prior studies using a motorized elliptical machine may have had greater intensity of training and greater potential for improvement than did our participants.
The training target in our protocol focused on safely increasing exercise time and tolerance while maintaining predetermined physiologic parameters, as opposed to increasing training speed. This is another possible reason that our participants may not have demonstrated increases in walking speed. Prior studies have shown that to optimize the effectiveness of treadmill training for improving gait speed, it is important to provide the appropriate training stimulus. For example, both Sullivan7 and Pohl et al9 demonstrated that a systematic progression of treadmill training at higher speeds led to greater improvements in walking speed than training at lower or variable speeds. During the elliptical training, our participants maintained cadences ranging from 80 to 110 steps per minute and step lengths of 43 to 51 cm. This would correspond to overground walking speeds of approximately 0.57 to 0.94 m/s. Considering that our participants’ pretraining habitual walking speeds ranged from 0.34 to 0.98 m/s, our protocol has not provided a sufficient stimulus to improve habitual or fast walking speeds. If the primary goal was to improve walking speed, emphasis on progressive speed-dependent interval training would have been more likely to achieve that goal. To aid with this type of training when using an elliptical machine, a therapist could provide manual assistance by grasping the moving hand bars of the elliptical machine to help increase stepping cadence, as well as adjust step length to simulate walking speeds greater than the individual's current overground walking speed. Discouraging excessive use of the stationary handrails and using auditory cues such as a metronome or music to facilitate increased speed of movement might also be options worth considering.
Effects of Elliptical Training on Walking Endurance
Training had variable effects on walking endurance in the 3 participants in our study. Participants 1 and 2 showed no changes in 6MWT performance while participant 3 demonstrated a 25% improvement. These mixed results may be explained by the fact that on entry into the study participants 1 and 2 were community ambulators who regularly walked for periods longer than 6 minutes, while participant 3 was primarily a household ambulator. Therefore, at the start of the study, participants 1 and 2 had the fitness level to walk for 6 minutes without rest, and for this reason it is possible that little or no change in 6MWT performance may be expected despite improvements in cardiorespiratory endurance. In retrospect, the use of an alternative submaximal walking protocol (eg 1-mile walk test) or direct measurement of oxygen consumption may have been more appropriate for assessing changes in cardiorespiratory fitness or the energy cost of walking for participants 1 and 2. Since participant 3 was only a household ambulator with lower initial endurance, he required one standing rest break during his pretraining 6MWT. During his posttraining assessment, he was able to complete the 6MWT without rest. This may have been a result of improved fitness, which was associated with an increase in 6-minute walking distance without a change in gait speed.
When assessing the limited changes in 6MWT performance, another important factor to consider is training frequency. With missed visits, participants 1 and 2 averaged less than 3 sessions per week and participant 3 less than 2 times per week, which is below the minimum frequency (3 times per week) recommended by the American College of Sports Medicine for improving or maintaining cardiorespiratory fitness.23 On the basis of our own clinical experience, when we designed the training program, we chose to err on the lower end of training frequency to evaluate what might be more realistic for individuals to achieve in a home or community setting on a long-term basis.
Despite the variable changes in the 6MWT performance, all participants were able to show consistent and progressive increases in total training time on the elliptical machine. By the end of training, all participants were able to achieve 20 minutes of exercise with a decrease in the number of rest breaks required and a decrease in body-weight support provided while maintaining appropriate physiological and exertion levels (Table 2). These changes could indicate possible improvements in both cardiorespiratory and muscular endurance.
Effects of Elliptical Training on Balance and Functional Mobility
After training, all of the participants demonstrated improvement in measures of balance and functional mobility. The BBS task “unsupported alternate stepping onto a 6-inch stool” (Item 12) was the item for which both participants 2 and 3 demonstrated their largest improvement (2 points). This task requires alternate hip and knee flexion greater than typically used during walking. Elliptical training induces greater hip and knee flexion than walking over ground and may therefore underlie the improved performance on this task. However, and alternative explanation for the improved BBS scores was that participants had to step on and off a 6-in platform placed behind the elliptical machine, as well as on and off the elliptical machine pedals on several occasions each time they trained. Performing these activities, including managing the increased vertical movement of the body while training on the elliptical machine, may have led to greater confidence in the transitional, stepping, and turning movements involved in both the BBS and the TUG.
Feasibility of Use
One of the primary goals of this case series was to evaluate the feasibility of using a nonmotorized elliptical machine for individuals with chronic stroke. After completing this case series, we feel that elliptical training is a feasible option. However, based on our experience, there are several important factors to consider when selecting the equipment and the appropriate patients for elliptical training. We selected our device for the unique attributes described previously. We feel that 2 of these features, the central drive mechanism and large sturdy handrails, were most critical to the safe use of the elliptical machine in our participants. The central drive mechanism allowed for safe mounting/dismounting from the back of the unit; fortunately, the use of a central or front drive mechanism is becoming a more common feature of commercially available elliptical machines. The large handrails allowed the participants to use their upper extremities for support during training and while mounting/dismounting the machine.
Besides the standard features of the elliptical machine, we used a simple harness system to ensure participant safety and Velcro foot straps to maintain appropriate foot placement. During training, we found that offering some body-weight support allowed the participants to increase their training time more quickly while maintaining good posture and appropriate exertion levels. We chose to do this because it became apparent that muscular endurance in the lower extremities was a limiting factor initially for each of the participants. Participants complained specifically of fatigue in the knee extensors. Prior research involving individuals without disabilities has also reported increased lower extremity perceived exertion during elliptical training when compared with treadmill training.32 Although we found the harness helpful in this regard, we do not feel that it was essential for providing safe and effective elliptical training for our participants; however, we feel that without the harness initial training, time and progression would have been more limited. During the initial phase of training, we also added a Velcro strap to maintain foot position of the involved lower extremity on the pedal. This was done by loosening several bolts on the pedal and sliding the strap between the pedal and the plate that it was attached to and retightening the bolts. Therefore, choosing a unit that easily allows for the addition of a foot strap may be advantageous.
When deciding whether nonmotorized elliptical training is a good option for a patient, there are several important factors that should be considered. First, patients need sufficient balance and postural control to safely mount and dismount the unit, especially if harness support is not available. Second, patients should have adequate dorsiflexion range of motion (at least 0°-5°). Significant plantarflexion contracture would make it difficult to keep the foot on the pedal through the entire pedal stroke, even with the use of a foot strap. Patients should also have good scapular mobility, full elbow extension, and shoulder flexion to at least 90° to safely and effectively use the moving hand bars. Adequate grip strength and the absence of significant upper extremity spasticity might also be important requisites for using the moving hand bars. During our training, we chose not to encourage the use of the upper extremities because we observed significant glenohumeral and scapulothoracic biomechanical alterations that we felt put our participants at risk for injury. However, adaptations such as gripping the hand bars lower may help decrease abnormal movements and the range of motion required.
This investigation has several limitations. This was a case series that does not allow for generalization of findings and also limits the ability to compare the outcomes with other research. Two of our participants were able to walk in the community, and therefore the safety and feasibility of training individuals with greater impairment of walking function are not known. The choice to use the 6MWT for measuring endurance may not have been appropriate for the 2 higher-functioning participants. In addition, the decision to provide partial body-weight support that was not measurable made it difficult to assess the possible effects this support may have had on the training program and outcomes. Finally, the use of nonblinded assessors and the lack of repeated baseline testing to establish consistent baseline performance were also weaknesses. Despite these limitations, this case series does provide practical information for clinicians and researchers considering the use of elliptical training for gait and endurance training in ambulatory persons with chronic stroke.
The primary purpose of this case series was to evaluate the feasibility of using an elliptical machine in ambulatory adults with chronic stroke, and to measure changes in measures of functional walking capacity, including walking speed, endurance, and balance following an 8-week training program. We found that using the elliptical machine was feasible and well tolerated by our participants. While there were no improvements in gait speed, participants had variable improvements in other aspects of functional walking capacity (ie, endurance, balance, and functional mobility). Based on the findings of this case series, elliptical training may offer an affordable upright training option for ambulatory individuals with chronic stroke in both clinical and community settings. However, when using elliptical machines, clinicians and researchers should carefully consider equipment design, principles of exercise prescription, patient selection, and choice of outcome measures. Future research involving larger, randomized, controlled trials comparing elliptical training with conventional gait and treadmill training may be warranted.
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balance; elliptical; exercise; gait; stroke