A Cohort Study to Evaluate the Feasibility of Low Load/High Repetition Elastic Band Resistance Training for People with Chronic Obstructive Pulmonary Disease

Pulmonary rehabilitation is effective for people with Chronic Obstructive Pulmonary Disease (COPD) with regard to symptoms, function, participation, and health-care resource utilization [1]. One of the components of this evidence-based comprehensive intervention is resistance training that has been found to be beneficial in improving muscular strength, cycle endurance capacity [2-4] and upper extremity functional capacity [4]. In COPD, the predominant choice of exercise equipment in resistance training regimens has been weight machines. However, lack of access to this exercise equipment can be a barrier to maintenance of exercise capacity. This has highlighted the need to examine effects and safety of alternate exercise equipment [3]. Elastic resistance equipment such as elastic bands and tubing offers an alternative that has shown comparable results to weight machines regarding both upper and lower extremity exercises in healthy adults [5,6]. In people with COPD, O ́Shea et al. [7] found that a predominantly home-based resistance training regimen with elastic bands could be used to increase knee extensor strength. Nevertheless, they did not find any effect on upper extremity strength and walking ability. The authors argued that the high attrition rate, with more than 40% of participants unable to complete the exercise program, to some extent may have influenced the effectiveness of the exercise regimen. This is, to our knowledge the only published study that have used elastic bands as primary resistance in people with COPD. In addition the study did not report any information about feasibility of the exercise program such as adverse events and compliance. Therefore, knowledge concerning the feasibility of using resistance training with elastic bands as resistance is limited for this group of people.


Introduction
Pulmonary rehabilitation is effective for people with Chronic Obstructive Pulmonary Disease (COPD) with regard to symptoms, function, participation, and health-care resource utilization [1]. One of the components of this evidence-based comprehensive intervention is resistance training that has been found to be beneficial in improving muscular strength, cycle endurance capacity [2][3][4] and upper extremity functional capacity [4]. In COPD, the predominant choice of exercise equipment in resistance training regimens has been weight machines. However, lack of access to this exercise equipment can be a barrier to maintenance of exercise capacity. This has highlighted the need to examine effects and safety of alternate exercise equipment [3]. Elastic resistance equipment such as elastic bands and tubing offers an alternative that has shown comparable results to weight machines regarding both upper and lower extremity exercises in healthy adults [5,6]. In people with COPD, O´Shea et al. [7] found that a predominantly home-based resistance training regimen with elastic bands could be used to increase knee extensor strength. Nevertheless, they did not find any effect on upper extremity strength and walking ability. The authors argued that the high attrition rate, with more than 40% of participants unable to complete the exercise program, to some extent may have influenced the effectiveness of the exercise regimen. This is, to our knowledge the only published study that have used elastic bands as primary resistance in people with COPD. In addition the study did not report any information about feasibility of the exercise program such as adverse events and compliance. Therefore, knowledge concerning the feasibility of using resistance training with elastic bands as resistance is limited for this group of people.
A majority of previous resistance training studies in COPD have primarily focused on increasing muscular strength. Little is known regarding other trainable characteristics, such as peripheral muscular endurance which may be of importance since quadriceps muscular endurance has been shown to be reduced to a larger extent in comparison to quadriceps strength in people with COPD [8].
people with COPD. However the feasibility of this exercise regimen in people with COPD is still unknown.
Therefore, the aim of the present study was to investigate if: 1. A low load/high repetition elastic band Resistance Training (RT) regimen is feasible in people with COPD? 2. The RT regimen is considered feasible for the physiotherapists supervising and conducting the intervention in clinical settings?

Method Design
The study was performed on people with COPD who were randomly assigned to participate in an eight week RT regimen [9]. The present study was approved by the Regional Ethical Board, Umeå University, Umeå, Sweden (Dnr: 2010-344-31 M) and was registered at www.clinicaltrials.gov (NCT01354067). The study is reported in line with strengthening the reporting of observational studies in epidemiology guideline [10]. Recruitment, data collection and followup were performed from August 15, 2011 to May 3, 2012 [9].
Eligibility criteria for patients included having stable COPD stage II-IV according to the Global Initiative for Chronic Obstructive Lung Disease guidelines [11], ex-smoker, on stable medication and randomized to participate in the RT regimen. Eligibility criteria for physiotherapists included at least two years' experience of working as a physiotherapist, one year experience of working with cardiorespiratory patients, and at least one year experience of leading training groups [9]. Written informed consent was obtained from both patients and physiotherapists.

Interventions
The RT regimen is a standardized resistance training regimen which consists of eight upper and lower extremity exercises performed with one leg/arm at a time. Six exercises are performed with elastic bands (Thera-Bands ® , The Hygenic Corporation) and two with body weight (heel-raise and step-up) as primary resistance ( Figure 1).
The RT regimen was conducted in a group format and supervised by physiotherapists. Each group consisted of three to seven patients who attended three sessions per week during eight weeks. The sessions lasted approximately 60 minutes including warm-up, exercise and cooldown, each part designed in accordance to American College of Sports Medicine recommendations [12][13][14]. Volume, initial load, rest periods, frequency, repetition velocity, and progression in the RT regimen were standardized in accordance with recommendations for increasing peripheral muscular endurance [9,14]. The exercises within the RT regimen target muscles with decreased strength/endurance (compared to healthy individuals), muscles which are important for upper extremity activities of daily living, and muscles which are important for walking [15][16][17][18]. All exercises were executed using a single limb at a time, alternating left to right side in order to minimize the risk of a central constraint [19]. Execution of all exercise was standardized to optimize activation of targeted muscles, and included execution in the most clinically effective portion of elastic resistance [2,9,[20][21][22]. The length of each individual elastic band, patient position from elastic resistance insertion and, start and stop positions for each exercise, were also standardized [9,23]. All components were individually determined and progressed with use of Borg category ratio (CR10) scale [24], according to a specified protocol to optimize individual tailoring of the exercise regimen [9]. The physiotherapists were given a standardized education session in order to deliver a uniform intervention and the exercise protocol was given to both people with COPD and physiotherapists to enhance adherence and familiarization. Written commitments to follow to the assigned protocol were signed by all physiotherapists. Further description on the components and standardization of the exercise regimen are available [9].

Outcomes and follow-up
Feasibility of the RT regimen was assessed by the attendance rate, Warm-up (10 min) The warm-up focused on low intensity dynamic flexibility exercises to ensure adequate range-of-motion, familiarization of RT movements, and execution of motions at optimal velocity to rehearse desired motion patterns as recommended by American College of Sports Medicine. Step up with right foot on top of the board and place the whole foot on the surface. Then lift the left foot upwards and "touch" the stepup board's surface and then lower the left foot down, back to the starting position. Finally step down with right foot to the starting position at the same speed.

RT
All exercises were released in a controlled manner to the starting position at the same speed and then repeated for the accurate number of repetitions. Cooldown (10 min) The cool-down consisted of five stretching exercises based on involvement in the RT regimen, targeting musculus (m). pectoralis major, m. biceps brachii, mm. hamstrings, mm. quadriceps and mm. triceps surae in accordance to recommendations of American College of Sports Medicine .
Illustrations reproduced with permission. Copyright ©2014 Exercise Organizer AS Figure 1: Description of the exercise regimen. RT=low load/high repetition elastic band resistance training *the step-up exercise was performed using the patients self-paced speed.
exercise intensity, compliance and occurrence and severity of any adverse events. All outcome data was collected between the baseline tests and within three weeks after the end of the eight-week intervention.
Attendance was evaluated by calculating an attendance rate for each patient as the number of attended sessions divided by total number of sessions.
Exercise intensity was evaluated through assessment and progression of the intensity. Mean muscle fatigue rating on the Borg CR10 scale during the whole intervention period was divided by muscle fatigue rating at a baseline 25 repetition maximum test to determine exercise intensity. The ratings during exercise training were done independently by the patients by pointing to a Borg CR10 scale for dyspnea and muscle fatigue, noted by the physiotherapist. Progression of exercise intensity was evaluated by comparing exercise intensity between the first and last exercise session.
Information about adverse events was collected from exercise diaries and post training interviews with the physiotherapists who led the interventions. Two independent pulmonologists and one physiotherapist who were not involved in the study evaluated the adverse events. The severity of them was assessed and rated into four different categories: (1) minor and temporary, (2) serious symptoms (potential risk of severe injury or life threatening), (3) manifest injury or disease, and (4) death as previously used [25]. An adverse event rate was calculated for each patient as the total number of sessions in which any adverse events occurred divided by the total number of attended sessions.
Compliance was evaluated by a standardized questionnaire. The questions, ranging from 1 to 5, focused on the extent to which they could follow the instructions on the different components of the intervention. A rating of 1-3 was defined as a small extent and 4-5 large extent. The dichotomization was used to simplify the understanding of the interpretation of compliance to the exercise regimen.

Statistical analysis
Data analyses included all patients using intention-to-treat analysis. Data was missing on the compliance questionnaire from one participant with COPD due to an exacerbation after the end-ofintervention period. This missing data was considered Missing Not At Random (MNAR). Missing ratings was due to the physiotherapists forgetting to note the rating, which was considered Missing At Random (MAR) [26]. MNAR and MAR data was imputed using the overall mean [27]. A sensitivity analysis was performed comparing the results with imputed data to a complete case analysis [10]. Comparison between participants and physiotherapists regarding compliance were performed using the Chi-square test. Paired sample t-test and Wilcoxon signed rank test was used for exercise intensity and complete-case comparisons when appropriate. Data is presented in mean (95% confidence interval (95%CI)) or median (interquartile range (IQR)) depending on distribution of data unless otherwise stated. No additional analyses were made. A p value of <.05 was considered statistically significant. For data management and statistical analysis the IBM Statistical Package for Social Sciences (SPSS) version 20.0 was used. Additional details of the methods used are provided in study protocol [9].

Results
The RT regimen was implemented and administered according to trial protocol [9]. All participants completed the intervention ( Figure  2). All data was collected within three weeks after completing the intervention. Participant characteristics are presented in Table 1 and experience of the five physiotherapists is presented in Table 2.

Attendance
Twenty-four RT sessions were conducted during the eight-week intervention period. An additional exercise week was offered to enable everyone to reach the minimum goal of 20 exercise sessions. The mean attendance rate was 22.5 out of 24 sessions, i.e. 94% (91-97) [9,28]. The mean attendance rate without the additional week was 91% (87-94).

Exercise intensity
The mean exercise intensity measured as rated muscle fatigue during the intervention was 4.4 out of 5.6 obtained from the baseline 25 repetition maximum test [9], i.e. 79% (74-83) of the predicted maximum intensity. An increase in resistance, exemplified for the knee extension exercise, of mean 1.7 kg (0.9 to 2.6) (p<.001), i.e. a 28% increase in resistance, was seen between the first and last exercise session for all elastic exercises. All participants started at level one in the heel-raise and the step-up exercise. At week eight the median level was 2 (1-2.25) (p<.001) and 1 (1-2) (p=.003) for single leg heel raise and single leg step-up, respectively.

Adverse events
Eight participants reported a total number of 28 adverse events distributed over 18 (3.6%) of the attended exercise sessions. The median rate of sessions in which they experienced adverse event per attended session was 0% (0-9) for all participants. All adverse events were minor and temporary as judged by the independent pulmonologists as well as by the physiotherapist. There was no disagreement between assessors on any adverse event. The adverse events were musculoskeletal (such as pain or soreness: 64%), related to the elastic resistance bands (such as bruising, pain, laceration, swelling: 32%), and dizziness (4%). Seven out of the nine (78%) adverse events related to the elastic resistance bands was reported during the first seven sessions.

Compliance
All physiotherapists and all but one patient filled out a questionnaire about the RT regimen. The questions focused on the participants and physiotherapists ability to follow the instructions on the different components of the RT regimen. When rating their own ability to follow the instructions of the RT regimen (when looking at all components together) 96% (94-96) of participants and 100% (94-100) physiotherapists, could follow the instructions to a large extent. Regarding compliance to the individual components of the RT regimen, all physiotherapists felt that they could follow the instructions to a large extent with regard to the whole regimen, the eight exercises, the warm-up, the no of repetitions and the ratings of exertion. Fifty percent of the physiotherapists thought that they could follow the instructions to a large extent on the cool-down component of the RT regimen, 71% regarding the speed of movement component and 88% regarding the progression component of the RT regimen. There was no difference between the participants and physiotherapists' ratings on any of the different components of the RT regimen regarding the participants' ability to follow the instructions to a large extent (Table  3). In addition, compliance was 96% and ranged between 88%-100% for the participants and physiotherapists respectively on the components of the RT regimen related to the elastic bands. The results did not differ when compared to the complete case analysis on any of the components of the RT (p=.624-.744).

Smoking status
Years smoked 38 (12) Pack Years 30 (7) Occupation Retired 18 (82%)   With cardio-respiratory patients 7 (5.5-8.5) 6 (4-7) 7 Of group training 11 (10.5-11.5) 12 (6.5-17.5) 19 Of using elastic bands 2.5 (2.25-2.75) 3 (3-3) 3 No of treated patients in the study 6 12 4 Data is median (interquartile range) if applicable. RT=low load/high repetition elastic band resistance training  with moderate to severe COPD. There was a high attendance rate, high mean exercise intensity with a significant progression, and a high compliance with the RT regimen for both people with COPD and the physiotherapists performing the RT regimen. Furthermore, there were few adverse events and these were considered minor and temporary.
This study adds to the body of knowledge regarding feasibility of resistance training in general and of elastic band resistance training in specific in people with COPD. The results from this study indicate that an elastic band resistance training regimen is feasible in people with COPD, when performed as low load/high repetition resistance training supervised by physiotherapists in an outpatient setting.
The feasibility of elastic resistance equipment in resistance training for people COPD is of importance since it, in comparison to weight machines, offers a portable and inexpensive alternative that is easy to use and more accessible [29,30].
The attendance rate in the present study was much larger (94%) than in the elastic band study by O´Shea et al. (56%) [7]. However, the present RT regimen was performed in group and in an outpatient setting which previously has been shown to have higher completion rates than an individual exercise regimen performed in a home setting [31]. Nevertheless, also in comparison to other studies of resistance training performed in groups of people with COPD the attendance rate was high [3].
We identified a number of adverse events in this study, of which a third (9 out of 28) was related to the elastic bands. A pilot study on one individual with COPD was executed to test the RT regimen in general and the elastic bands in specific [22,23]. However, this may not have been sufficient. The majority of adverse events related to the elastic bands occurred within the first seven exercise sessions. All were considered minor and temporary and were related to how the elastic band was fastened on the exercising limb. Small alterations were made that minimized the rate of adverse events in upcoming sessions. A more comprehensive pilot testing before start of intervention could have identified the initial problems with the elastic bands which may have reduced the number of adverse events related to the equipment.
Compliance to the RT regimen was excellent for both the participants in the RT regimen and the physiotherapists conducting the intervention on the RT in general and on the components of the RT related to the elastic bands in specific. As far as we know this is the first study to evaluate compliance to the different components of a specific exercise regimen in COPD. The enrollment of the physiotherapists as a control on the questionnaire with regard to the participants' ability to follow the instructions of the RT regimen may be considered a bias on the study outcome. The reason for using the physiotherapists as a control was that we anticipated that the participants may have an excessively positive approach to the exercise regimen only for being selected to participate in the study. By comparing the participants opinions with the opinions from the physiotherapists regarding the participants' ability to follow the instructions of the RT regimen we believed that we would get a more balanced and correct result.
Strengths of the present study were the rating of severity of adverse events, the use of raters not involved in the study and the assessment of compliance to the different parts of the RT regimen in both participants and physiotherapists. Other strengths were the comprehensive and standardized description of the RT regimen which facilitates reproducibility and implementation of the intervention. Furthermore, the whole design of the RT regimen focused on clinical applicability.
One limitation in the present study was that no particular instructions were given to the physiotherapists at baseline to note adverse events which may imply a possible underestimation for the occurrence of adverse events. Nevertheless, adverse events were registered and collected from exercise diaries and post-intervention interviews with the physiotherapists and all adverse events that were reported were considered minor and temporary by the independent raters.
Other limitations were that the majority of patients included in the intervention were people with moderate disease and that no participant with very severe COPD was included, as originally intended. This precludes generalization to people with COPD with larger ventilator restraints and muscular dysfunctions. Nevertheless, the results are of importance since people with moderate disease are one of the larger groups in the COPD population [32]. However, it would be of interest to investigate the feasibility of the exercise regimen also in people with were severe disease as adherence to pulmonary rehabilitation has been shown to be lower in those with larger ventilator restraints [33,34]. Also, there were some missing data which may have led to bias [26]. However, no differences were seen in comparison with complete case data and there were generally only a few missing observations, which may be considered as a minor disruption [10,26].
The main clinical implication of this study is that this low load/ high repetition elastic band resistance training regimen is feasible for both people with moderate to severe COPD and physiotherapists conducting the intervention. This indicates that elastic bands could be an alternative to weight machines in resistance training for people with COPD. Further studies are needed to evaluate whether the results can be reproduced in a broader range of disease severity and different settings.