A pilot evaluation of a group exercise programme for people with Parkinson’s disease: A quantitative and qualitative approach

Abstract

BACKGROUND: This study investigated the clinical effectiveness of a newly developed primary care group exercise programme for people with Parkinson’s disease (PD) in terms of balance, functional mobility and self reported outcomes. A secondary aim was to explore participant’s perceptions of the programme and barriers to participation.

METHODS: A cohort study with measures pre/post/three month post intervention was carried out. Outcomes included the Six Minute Walk Test (6MWT), Timed Up and Go test (TUG), Lindop Scale, Functional Reach Test (FRT), Berg Balance Scale (BBS) and Parkinson Disease Questionnaire-39 (PDQ-39). The intervention was a once weekly, hour long circuit-based exercise class, with an educational component. Two focus groups were conducted.

ANALYSIS: Changes from pre to post and pre to three months were tested using paired sample ‘t’ tests, Wilcoxon signed ranks tests and chi square tests. Bonferroni corrected statistical significance was set at p < 0.025. Qualitative data were subject to thematic content analysis.

RESULTS: Fifteen participants, 11 male, 4 female of mean age 72 years and mean Hoehn and Yahr rating 2.5, were included. Clinically and statistically significant changes (p < 0.025) in BBS, FR and PDQ-39 were found after exercise participation and these were sustained after three months. There was a trend for declining proportion of patients falling at follow up (40% in 3 months prior to programme v 10%). Emerging qualitative themes included enjoyment and perceived functional improvements.

CONCLUSION: This research reveals the effectiveness of this programme in improving balance, functional mobility and QoL. Participants perceived numerous benefits and suggested areas for improvement. Developing similar programmes around Ireland could optimise future healthcare management for the PD population.

Keywords

Parkinson’s disease evaluation exercise falls focus group

1 Introduction

Idiopathic Parkinson’s disease (PD) is a progressive degenerative neurological condition that results in significant functional disability. More than one million people live with PD in Europe and this number is forecast to double by 2030 [1]. Currently, over 8,000 people are living with PD in Ireland.

A decline in motor function is the natural course of PD. People with the condition have shown to reduce level of physical activity more quickly than their healthy peers [2] and have lower levels of strength and functional ability [3]. Since the most common age of onset is 50–60 years and life expectancy is near normal, people with PD suffer the debilitating consequences of the disease over decades [4].

Most people with PD may develop reduced balance [5]; which worsens with disease progression [6, 7]. This is associated with falls, poor mobility, disability and reduced quality of life [8, 9]. Despite optimal medication management, advances in pharmacologic therapy and surgical procedures, people with PD living in the community, experience falls. Up to 68 percent of people with PD will fall and up to 46 percent will experience recurrent falls each year [10]. These falls may be accompanied by injuries [11], fear of falling [12], reduced mobility and a concomitant development of weakness [13, 14], loss of independence, increased risk of nursing home admission [15] and reduced survival [16].

A recent prospective study of fall risk factors in Parkinson’s patients identified that leg muscle weakness, poor balance, and freezing of gait are independent risk factors for falls [17]. Given the high risk of falls and near misses in the PD population, these three potentially remediable risk factors are logical targets for an exercise programme for people with PD. If therapeutic interventions can improve these areas, future fall occurrences may be minimised. Exercise has been shown to improve balance [18 –20] and strength [20, 21], while cueing training [22] has been shown to improve freezing of gait [19] in people with PD. However, the heterogeneous nature of interventions, highly structured intervention protocols limits their generalisability and creates difficulty when applying evidence in the clinical setting. To date, to our knowledge, no study has been carried out evaluating the effectiveness of a PD exercise programme targeting fall risk factors in a clinical setting in Ireland. It is important to know the outcomes of group exercises programs administered in community settings. These programs may provide an inexpensive and sustainable approach to exercise that can be replicated easily and be readily integrated into a previously inactive lifestyle.

In the current health system in Ireland, there is increasing prioritisation for the need to identify effective and resource efficient approaches to implementing strategies which improve fall risk factors for patients in their local communities. A physiotherapy led group exercise programme for people with Parkinson’s disease has recently been developed in a primary care setting in Cork. However to date its effectiveness has not been examined.

The European Core Standards of Physiotherapy Practice recommends that treatment interventions are evaluated in practice to ensure they are effective and that results are in line with those found in research literature [23]. In addition, the implementation of new interventions in the clinical setting requires an understanding of patient experiences to ensure patient satisfaction. Higher satisfaction with health care services has been associated with increased patient compliance and better outcomes [24]. The primary aim of this study was thus not to test the efficacy of an exercise programme for PD patients in a controlled trial, but to assess the clinical effectiveness through subjective and objective patient outcomes, while exploring the acceptability to patients and feasibility (barriers to participation) in practice of a locally implemented community based group exercise program for people with PD, the “Keeping Active with Parkinson’s Programme”.

1.1 Aims

To investigate the clinical effectiveness of a once weekly, eight week supervised group exercise programme on balance, functional mobility, quality of life and falls in community dwelling people with PD.

To explore people’s perceptions of the “Keeping Active with Parkinson’s Programme”, including their views on strengths and weaknesses of the programme and barriers to participation.

2 Methods

2.1 Study design

A prospective repeated measures design was used in a cohort of subjects with idiopathic Parkinson’s disease. A mixed methodological approach, utilising both quantitative and qualitative data collection methods was used.

The quantitative outcomes consisted of balance, functional mobility and quality of life (QoL) measures. A focus group was chosen as an efficient qualitative method for obtaining data from multiple participants [25] and since group interactions can elicit new responses and build discussion about issues that may not be questioned during alternative methods such as structured individual interviews [26]. Moreover, a focus group discussion can provide individual accounts and reflection as part of the group, adding to the richness and comprehensiveness of the data [27]. A grounded theory methodology was utilised for the qualitative aspect of the study as this approach identifies the major constructs or categories of a phenomenon, their relationships, contexts and process with the intention of generating a theory relating to a particular situation [28, 29] in this case a PD programme.

2.2 Study population

Participants fulfilling the following criteria were deemed eligible to participate in the programme: male/female aged 40 years or over; community-dwelling; idiopathic PD, independently mobile with or without an aid; Hoehn and Yahr scale II-IV, independent in transfers; willing and able to participate in a group, without change in their current anti-Parkinsonian medication schedule for at least 2 weeks.

Participants were excluded if they had mental or physical impairment leading to an inability to exercise safely; severe visual or cognitive impairment; hip surgery in the previous 3 months; uncontrolled cardiovascular conditions; severe breathlessness or dizziness; unmanaged pain or acute systemic illness or not living independently (e.g. residential care). Medical clearance was required from each participant’s general practitioner prior to acceptance into the study.

2.3 Recruitment strategy

Patient referrals to this programme were accepted from consultants, general practitioners, community physiotherapists and occupational therapists. Participants were first informed of the programme by these health professionals. Once the patient expressed willingness and fitted the inclusion criteria, they received an information leaflet and consent form and were contacted by the researchers. Clients were informed that participation in the study was entirely voluntary and that they could still take part in the exercise programme without enrolment in the study. Participants were requested to defer any additional treatment for their PD, unless deemed necessary by their Consultant or General Practitioner until the study was completed. If additional treatment was used i.e. change in medication, that participant’s results would be excluded from subsequent data analysis.

2.4 Ethical approval

This study was approved by the Cork Teaching Hospital Clinical Research Ethics Committee and UCD Human Subjects Ethics Committee. Written informed consent was obtained from all participants prior to the assessment and data protection guidelines were adhered to.

2.5 Setting

The programme was conducted by the principal investigator in the ‘Physiotherapy Department, Assessment and Treatment Unit’ in St. Finbarr’s Hospital, Cork under the guidance of two other chartered physiotherapists. Both therapists had over four years experience of working with neurology clients.

2.6 Quantitative assessment

Balance, function mobility and quality of life outcome measures (Table 1) were assessed at baseline (T1), post programme (T2) and again at three month follow up (T3). The assessors were the principal investigator (PI) and the two other physiotherapists. The outcome measures chosen were selected on the basis of the literature and clinical practicality. They have been specifically found to be valid and reliable for the PD population [30–32 , 62]. Measurements were conducted one hour after each participant’s last dose of L-dopa, thus each participant were tested in their “on” phase. In addition measurements were taken at the same time of day and in the same order during each data collection session to minimise the risk of bias. A 1 hour training session for the assessors was carried out prior to any participant assessments to ensure assessments were conducted according to their guidelines of administration as outlined in the research. To minimise possible observer bias, all secondary outcome assessments were undertaken without reference to previous assessment data.

The number of falls was assessed by comparing the number of falls and proportion of fallers three months before the programme to three months after. Consistent with the recommendations of the Prevention of Falls Network Europe (PrOFaNE) group, a fall was defined as “an unexpected event in which the participant comes to rest on the ground, floor or lower level” [39]. All participants received a falls diary each month via post with instructions on how to record events. Participants were asked to return the completed diaries monthly in pre-paid envelopes provided.

Adverse events (defined as a significant injury or medical event that causes the participant to seek attention from a health professional or limit their activities) [4] were monitored and recorded throughout the study.

2.7 Qualitative assessment

Two, one hour focus groups were carried out one week after completion of each programme and participation was optional. Their purpose was to capture attitudes and experiences of the subjects and to identify strengths and weaknesses of the programme and barriers that may impact participation. The PI undertook the moderator’s role and focus groups were audio recorded. A pre-planned schedule that served as a guide towards the topic areas for discussion was used, thereby facilitating a consistent and systematic method for data collection. Key questions were open ended so responses were in participants’ own words. Probing questions were used when needed, but every effort was made to maintain a natural discussion.

2.8 Intervention

Classes were held once weekly, over eight weeks and consisted of moderate strength, balance and co-ordination exercises. The group exercise programme included a 10 min warm up, 40 min of circuit based exercises and a 10 min cool down (Table 2). The menu of exercises was drawn from an effective falls prevention programme for people with PD [4, 45] with some modifications. The physiotherapists tailored and progressed the exercises to meet individual capabilities - for example, adjusting the level of resistance, number of repetitions or level of intensity of exercises. Participants were encouraged to move quickly from one exercise to the next so that a modest aerobic benefit could be achieved. A register of attendance and individual record of each subject’s participation in circuit activities was kept.

Participants were provided with a booklet containing an individually tailored home exercise programme including safety precautions, instructions and photographs of exercises for home session. Subjects were encouraged to carry out their exercise programme at least three times a week for approximately 15–20 minutes in accordance with the ACSM guidelines for neuromuscular exercise for the management of Parkinson’s disease [40].

Two 45 minute educational sessions were held throughout the programme. Presentations included education on PD, strategies for falls prevention and evidence-based cueing strategies to reduce freezing of gait [22]. A question and answers session was held after each presentation.

2.9 Data analysis

2.9.1 Quantitative data

Participants were evaluated one week before and one week after the programme. Data were analysed with PASW v 18.0 [41]. Descriptive statistics (mean, SD, count and percentage) were used to summarise demographic and outcome variables. The Kolmolgorov-Smirnov test was applied to determine whether data were normally distributed. Analysis tested for group differences from (i) baseline (T1) to post intervention (T2) and (ii) from baseline (T1) to follow up (T3). Paired t tests were used for normally distributed variables and the Wilcoxon sign rank test where normality did not apply due to the small number of participants. A Bonferroni adjusted p value of <0.025 was set for statistical significance, to account for risk of type I error with repeated testing. The magnitude of treatment effect was calculated with the Standardised Mean Difference, a measure of effect size (ES). This is interpreted in line with Cohen’s conventions where ES = 0.2 is considered small, 0.5 medium and 0.8 large [42]. Finally, chi square tests examined change in proportion of fallers in the period 3 months before and 3 months after the programme.

2.9.2 Qualitative data

A thematic content analysis was conducted. The tapes were transcribed assigning anonymous codes to each participant. The transcripts were examined line by line and coded by identifying significant sentences or concepts by an independent assessor. These concepts were then grouped into emerging themes by comparing concepts identified across the two focus groups [43]. An independent assessor experienced in qualitative research evaluated the data and emerging themes for accuracy and credibility.

3 Results

3.1 Quantitative

Fifteen participants (11 men and 4 women) of mean age 72 years (range 65–84) were recruited into the study. They had been diagnosed with Parkinson’s disease for a mean of 8.1 years and had a median Hoehn and Yahr score of 2.5 (range 2–3.5). All participants completed the programme. Attendance to the ‘Keeping Active with Parkinson’s Programme’ was 93 percent overall.

No injuries or other adverse events were reported by participants. Five individuals were lost to 3 month follow up, secondary to increased level of falls/ dizziness, change of medication or requiring surgery for c-spine dennervation, or unavailability. Complete case data are thus presented for all 15 participants post intervention and for 10 at 3 months (Table 3). It can be seen that significant (p < 0.001) improvements in BBS, FR and PDQ-39 accrued to the 15 participants after completion of the exercise programme, reflected in large treatment effects (ES 1.35 to 2.45). Post hoc power analysis demonstrated that these three analyses had sufficient power (>0.9) and at 3 month follow up the gains compared to baseline remained statistically significant. A statistically significant difference was found in the Berg Balance Scale, with a large effect size of 2.45 post programme and this improvement was maintained after 3 months with an effect size of 2.67. There was also a reduction, although not statistically significant in the percentage of falls from 46.6 percent in the 3 months prior compared 10 percent in the 3 months post programme. The average falls per person in the same time scale decreased from 0.6 pre to 0.4 post. The changes in 6MWT, TUG and Lindop Scale were not statistically significant. When the power of each of these analyses was checked, it emerged that these comparisons were in fact underpowered (<0.8), with a risk of concluding a non-significant result, when some real change has in fact occurred. This was borne out by the moderate effect sizes for the 6MWT (ES = 0.58) and Lindop Scale (0.55) immediately after participation, which demonstrated that there was a positive treatment effect.

3.2 Qualitative

A total of seven participants participated in the first focus group and five took part in the second.

Three main themes emerged relating to benefits gained from the programme and two main themes emerged in relation to areas of improvement. These are illustrated below by representative citations from the transcripts and referenced by group and respondent i.e. G1, R#1; Group 1, Respondent 2.

4 Benefits of programme

4.1 Increased functional ability

Respondents were in strong agreement that the main benefit gained from the programme was increased functional ability, especially in relation to bed mobility, transfers and walking.

“I learned in the class how to get in and out of bed, that was my biggest barrier” G2, R#1

“It (Bed mobility) improved massively, now I see the benefit of rolling onto my side and balancing your body, then up” G2, R#11

“Well I had great difficulty getting out of chairs; I never knew the method of how to do it, now I do” G1, R#3

“My walking came on greatly and I’m trying to maintain that” G2, R#15

4.2 Increased confidence/support

Participants revealed that they benefited from an increased level of confidence and support from the rehab team and peer support within the group.

“Increased confidence, I’ve got a few falls so I was becoming a bit nervous” G2, R#15

“Well you feel more secure when you meet people in the same boat as yourself” G2, R#1

“Yeah, I’d be looking forward now to going for a walk. Before I’d be happy to stay in the chair and watch tv” G1, R#4

“All I can say is the program was very beneficial. Overall we have learned from one another” G2, R#1

“I feel much better now. I think when I came in, I was feeling sorry for myself and having completed the program, I feel more secure” G1, R#3

5 Suggestions for improvement

5.1 Length of programme

Numerous participants recommend reducing the length of the programme from 8 weeks to 6 weeks mainly due to difficulty getting transport to the classes.

5.2 Multidisciplinary Input

There was a general consensus on having more multi-disciplinary input into the programme would make it more beneficial.

“It (More input from MDT) would be good” G 2, R#11

“Yes speech therapy, I’ve fierce complications with my speech, I would like that” G2, R#1

Additionally, participants in group 2 outlined that the program could benefit from psychological input as many reported altered mentality after their diagnosis. Symptoms of depression are common in persons with PD and these may affect exercise endurance and the motivation to exercise.

“It (PD) affects you physically and mentally. One of the things with Parkinson’s is depression. You get depressed” G2, R#1

“It can be very difficult to cope at times” G1, R#2

6 Discussion

This study confirmed the acceptability and effectiveness of a newly developed group exercise programme for people with Parkinson’s disease in improving balance, functional mobility and quality of life. While the sample size was small, there was sufficient statistical power for the Berg Balance Scale, Functional Reach and PDQ-39 analyses. There was an average change of 7.4 points in the Berg Balance Scale which was significant. This reflects previous research on Parkinson’s programmes which have shown statistically significant improvement in balance measures. The improvement in balance scores was consistent with the minimal detectable change of between 4 and 7 points [44]. Shumway-Cook et al. [45] reported a nonlinear relationship between fall risk and Berg score. Their predictions held through for our study, the improvement in Berg Scores was associated with a reduction in the percentage of falls pre and post programme which is a very promising finding. The 5.5 cm improvement in the FRT was also found to be statistically significant despite being lower than the minimally important difference of 9 cm [37].

It is well established in the literature that exercise has been found to improve health related QoL in people with PD [46]. Our study showed a statistically significant improvement in all domains of the PDQ39, a trend which was maintained even after 3 months post programme. These results however contrast with Allen et al. [45] who failed to show any improvement in. The success seen here might be attributed to greater therapist supervision. We observed only small non-significant differences in the TUG, despite the intervention including mobility training, practising rising from a chair and turning; all components of the TUG. Interestingly, among studies with people with PD that have evaluated movement and exercise interventions [19, 48], none have identified significant improvements in this test, despite its widely recommended use as an outcome measure for the PD population [49]. One possible explanation is that the speed component of the TUG movement may not be amenable to change with exercise in PD, thus limiting the overall responsiveness of the TUG. In contrast the large treatment gain in stability as evidenced by improvements in BBS and FR is clearly evident.

There was a lack of statistically significant improvement in the Lindop assessment tool which may be because of the small sample size, or a ceiling effect in the scale. Similar findings were found in a recent study by Lindop et al. [50]. It is hypothesised that this scale may have limited utility for assessing change in those with mild to moderate PD. No statistically significant changes were identified for the 6MWT. The average 6 minute walk distance (MWD) for our sample ranged from 293 to 318 m which is not in agreement with previous literature reporting a range of 6MWD values from 315 to 560 m [33 , 51]. We anticipated that the inconsistency in distances walked may be caused by the variability in age and disease severity of participants and also the presence/absence of freezing in participants. Some discrepancy in the findings could also be likely because of the testing protocols used. Schenkman et al. [33] instructed participants to “walk at comfortable pace for 6 minutes” over a track of unspecified distance, whereas Garber & Friendman [52] instructed participants to “walk as fast as possible” over a short 12 m track, necessitating a large number of turns. This lack of standardisation makes it difficult to compare results between studies.

Although our programme failed to identify significant improvements in functional mobility and gait endurance with this small sample size, nonetheless the treatment effect size was moderate for Lindop (0.55) and 6MWT (0.58) which is promising. The small sample size meant that it was underpowered to detect significant difference. A sample size of 65 and 70 respectively would have been required to demonstrate a significant difference based on effect size and p value of 0.025. Overall results from this study suggest that participants in the program had some improvement in most measures and benefits were maintained up to 3 months post programme. Given the degenerative nature of PD and the length of the study this is an important and encouraging finding.

The qualitative results of the focus groups revealed numerous subjective benefits that participants gained from the program. The keys themes were increased functional ability, improved confidence and self efficacy and social support. Participants reported that exercising under supervision was important to allay their fears, increase confidence and security. Respondents demonstrated enhanced self-perceived control over their disease, consistent with reports among individuals with PD that exercise confers a greater sense of control [53]. This study also revealed that the main benefit participants perceived was increased functional ability. Respondents reported that they gained increased knowledge of the correct techniques with transfers and of the importance of exercises which is an important factor to address the management of a progressive neurological condition like PD. Participants in the PD program derived benefit from the support developed from peers in the class and from the rehab team. The benefits of exercising in a group and the camaraderie developed through this form of exercise has been previously identified in the literature [54]. This study also helped to establish areas of improvement within the program in order to improve its efficacy and overall patient satisfaction. Several patients within the focus group reported that the program would benefit from other MDT input and from being reduced in duration secondary to transport issues. It is envisaged that an increased number of educational sessions from other MDT members will be provided including speech and language therapist, psychologist/counsellor, dietician, PD support group etc. To minimize transport issues and improve patient access, it is anticipated similar programmes will be set up in other primary care centres in the region.

The mixed methods approach of quantitative and qualitative research plays an important role in evaluating population-based results as well as individual experiences with health interventions [55]. It provides a depth of knowledge that would be difficult to achieve through either method in isolation [56] and is a legitimate and effective means of assessing clinical and community practice [57]. This type of methodology allowed us to utilise outcome measures and in addition determine subjective benefits and areas of improvement of the program to enhance the programs efficiency and improve patient satisfaction.

This study demonstrates how a study can evaluate a newly developed intervention to determine if it is effective and that results are in line with current evidence. The qualitative aspect allowed exploration of areas of improvement for the program in order to enhance service delivery.

6.1 Methodological considerations

Despite our promising findings, there are a number of limitations of this current trial that need to be acknowledged. Various elements of internal validity were lacking. This was a single cohort study and there was no comparative control group, thus potential for the effects to be due to the group interaction rather than the exercise programme. Neither participants nor assessors were blinded to the exercise or the testing, this may have contributed to detection bias and an exaggeration in effect size. The research was conducted in a relatively limited geographical area, and with a relatively small number of participants. This introduces potential bias to the study and limits the generalisability of findings. Participants were rated II-III on the Modified Hoehn & Yahr Scale and therefore results cannot be generalised to those rated 0 or those rated IV or V, who are more severely disabled. With regard to the exercise programme itself, this study did not attempt to determine which specific aspects of the exercise program were most beneficial, but rather allowed for a varied set of exercises that might be typical of other community-based programmes. At the time of data collection, we did not record body mass or height: therefore, we were unable to use available reference equations for healthy subjects [59], to compare actual versus predicted 6MWD for subjects. Additional research that addresses each of these limitations is needed; including long term randomized controlled trials comparing community-based group exercise to a control group

7 Conclusion

This study confirmed the effectiveness of a newly developed Parkinson’s programme in increasing balance, functional mobility and quality of life. The program also revealed areas of improvement in order to enhance the program’s efficacy for patients. No adverse effects were observed. The mixed methods approach was a feasible method in which this new service development could be evaluated and improved. It is now important to develop effective, sustainable programs that people with PD can participate in, in the community. The development of such programs may have widespread and ongoing impact on improving the quality of life of people with PD and their families as well as easing demands on health care systems.

Conflict of interest

The authors have no conflict of interest to report.

Footnotes

Acknowledgments

We would like to thank chartered physiotherapists Cara O’Riordan and Teresa Twohig. This study would not have been possible without their assistance.

References

Dorsey

, Constantinescu

, Thompson

, et al. Projected number of people with Parkinson’s disease in the most populous nations 2005 through 2030. Neurology 2006;68:384–6.

Fertl

, Doppelbauer

, Auff

. Physical activity and sports in patients suffering from Parkinson’s disease in comparison with healthy seniors. J Neural Transm Park Dis Dement Sect 1993;5(2):157–61.

Bridgewater

, Sharpe

. Aerobic exercise and early Parkinson’s disease. J Neuro Rehab 1996;10(4):233–41.

Canning

, Sherrington

, Lord

, et al. Exercise therapy for prevention of falls in people with Parkinson’s disease: A protocol for a randomised controlled trial and economic evaluation. BMC Neurol 2009;9:4.

Howe

, Rochester

, Jackson

, Banks

, Blair

. Exercise for improving balance in older people. Cochrane Database of Systematic Reviews Issue 4. Art. No.: CD004963. 2007.

Bloem

, Bhatia

. Basal ganglia disorders. In: Bronstein

, Woolacott

, Nutt

, eds. Clinival Disorders of Balance, Posture and Gait, 2nd ed. London: Arnold 2004. Pp. 173–206.

Beckley

, Bloem

, Van Dijk

, Roos

, Remler

. Electrophysiological correlates of postural instability in Parkinson’s disease. Electroencephalography and Clinical Neurophysiology 1991;81:263–8.

Bloem

, van Vugt

, Beckley

. Postural Instability and Falls in Parkinson’s Disease. In Ruzicka

, Hallett

, Jankovic

, editors. Advances in Neurology: Gait Disorders, vol 87. Philadelphia: Lippincott Williams and Wilkins, 2001. pp. 209–23.

Franchignoni

, Martignoni

, Ferriero

, Pasetti

. Balance and fear of falling in Parkinson’s disease. Parkinsonism and Related Disorders 2005;11:427–33.

10.

Wood

, Bilclough

, Walker

. Incidence and prediction of falls in Parkinson’s disease: A prospective multidisciplinary study. Journal of Neurology, Neurosurgery & Psychiatry 2002;72:721–25. Ref ID: 19857.

11.

Johnell

, Melton

, Athkison

, O Fallon

, Kurland

. Fracture risk in patients with parkinsonism: A population – based study in Olmstead County, Minnesota. Age Aging 1992;21:32–8.

12.

Adkin

, Frank

, Jog

. Fear of falling and postural control in Parkinson’s disease. Mov Disorder 2003;18:496–502.

13.

Sato

, Kikuyama

, Oizumi

. High prevalence of vitamin D deficiency and reduced bone mass in Parkinson’s disease. Neurology 1997;49:1273–8.

14.

Taggart

, Crawford

. Reduced bone density of the hip in elderly patients with Parkinson’s disease. Age Aging 1995;24:326–8.

15.

Hely

, Morris

JGL

, Traficante

, Reid

WGJ

, O Sullivan

, Williamson

. The Sydney multicentre study of Parkinson’s disease: Progression and mortality at 10 years. J Neurol Neurosurg Psychiatry 2001;67:300–7.

16.

Bloem

, Hausdorff

, Visser

, Giladi

. Falls and freezing of gait in Parkinson’s disease: A review of two interconnected, episodic phenomena. Movement Disorders 2004;19:871–84.

17.

Latt

, Lord

, Morris

, Fung

. Clinical and physiological assessments for elucidating falls risk in Parkinson’s disease. Movement Disorders 2009;24:1280–9.

18.

Ashburn

, Fazakarley

, Ballinger

, Pickering

, McLellan

, Fitton

. A randomised controlled trial of a home-based exercise programme to reduce the risk of falling among people with Parkinson’s disease. Journal of Neurology, Neurosurgery and Psychiatry 2007;78:678–84.

19.

Nieuwboer

, Kwakkel

, Rochester

, Jones

, Van Wegen

, Williams

, Chavret

, Hetherington

, Baker

, Lim

. Cueing training in the home improves gait-related mobility in Parkinson’s disease: The RESCUE trial. Journal of Neurology, Neurosurgery and Psychiatry 2007;78:134–40.

20.

Hirsch

, Toole

, Maitland

, Rider

. The effects of balance training and high-intensity resistance training on persons with idiopathic Parkinson’s disease. Archives of Physical Medicine and Rehabilitation 2003;84:1109–17.

21.

Dibble

, Hale

, Marcus

, Droge

, Gerber

, LaStayo

. High intensity resistance training amplifies muscle hypertrophy and functional gains in persons with Parkinson’s disease. Movement Disorders 2006;21:1444–52.

22.

RESCUE Consortium. Using cueing to improve mobility in Parkinson’s disease. A CD-Rom for therapists; 2006. Available from: http://hces.unn.ac.uk/rescue/pubs/cd-rom.htm

23.

Irish Society of Chartered Physiotherapists (ISCP). European Region of the World Confederation for Physical Therapy. European Care Standards of Physiotherapy Practice; 2002.

24.

Keith

. Patient satisfaction and rehabilitation service. Arch Phys Med Rehabil 1998;79:1122–8.

25.

Kreuger

, Casey

. Focus groups: A practical guide for applied research (3rd ed.) Thousand Oaks, CA: Sage 2000.

26.

Slade

, Molloy

, Keating

. People with non-specific chronic low back pain who have participated in exercise programs have preferences about exercise: A qualitative study. Australian Journal of Physiotherapy 2009;55:115–21.

27.

Murphy

, Dingwall

, Greatbatch

, Parker

, Watson

. Qualitative research methods in health technology assessment. A review of the literature. Health Technology Assessment 1998;2:182–5.

28.

Becker

. Common pitfalls in published grounded theory research. Qual Health Res 1993;3:254–60.

29.

Mellion

, Tovin

. Grounded theory: A qualitative research methodology for physical therapy. Physiother Theory Pract 2002;18:109–20.

30.

Qutubuddin

, Pegg

, Cifu

, Brown

, McNamee

, Carne

. Validating the Berg Balance Scale for patients with Parkinson’s disease: A key to rehabilitation evaluation. Arch Phys Med Rehabil 2005;86:789–92.

31.

Podsiadlo

, Richardson

. The Timed Up and Go test: A test of basic functional mobility for frail elderly persons. Journal of the American Geriatric Society 1991;39:142–8.

32.

Morris

, Morris

, Iansek

. Reliability of measurements obtained with the Timed Up and Go test in Parkinson’s disease. Physical Therapy 2001;81:810–18.

33.

Schenkman

, Cutson

, Kuchibhatla

, Chandler

, Pieper

. Reliability of impairment and physical performance measures for person’s with Parkinson’s disease. Phys Ther 1997;77:19–26.

34.

Duncan

, Studenski

, Chandler

, Prescott

. Functional reach: Predictive validity in a sample of elderly male veterans. Journal of Gerontology 1992;47:M93–M98.

35.

Hoehn

. The natural history of Parkinson’s disease in the pre-levodopa and post-levodopa eras. Neurol Clin 1992;10:331–9.

36.

Pearson

, Lindop

, Mockett

, Saunders

. Validity and inter-rater reliability of the Lindop Parkinson’s Disease Mobility Assessment: A preliminary study. Physiotherapy 2009;95(2):126–33.

37.

Steffen

, Seney

. Test-retest reliability and minimal detectable change on balance and ambulation tests, the 36-Item Short-Form Health Survey, and the Unified Parkinson Disease Rating Scale in people with Parkinsonism. Physical Therapy 2008;88(6):733.

38.

Peto

, Jenkinson

, Fitzpatrick

, Greenhall

. The development and validation of a short measure of functioning and well being for individuals with Parkinson’s disease. Quality of Life Research 1995;4:241–8.

39.

Lamb

, Jorstad-Stein

, Hauer

, Becker

. Development of a common outcome data set for full injury prevention trials: The prevention of falls network Europe consensus. J Am Geriatr Soc 2005;53:1618–22.

40.

American College of Sports Medicine (ACSM). ACSM’s Guideline for exercise testing and prescription. 7th ed. Philadelphia: Lippincott Williams and Wilkins, 2006.

41.

SPSS Inc. PASW Statistics 18. Chicago, IL: SPSS Inc.; 2009.

42.

Cohen

. Statistical power analysis for the behavioral sciences. 2nd ed. New Jersey: Lawrence Erlbaum; 1988.

43.

Krueger

. Focus Groups – A practical guide for applied research. 2nd ed. London: SAGE Publications; 1994.

44.

Donoghue

, Stokes

. How much change is true change? The minimal detectable change of the Berg balance scale in elderly people. J Rehabil Med 2010;41:343–6.

45.

Shumway-Cook

, Baldwin

, Polissar

, Gruber

. Predicting the probability for falls in community-dwelling older adults. Phys Ther 1997;77:812–9.

46.

Goodwin

, Richards

, Henley

, Ewings

, Taylor

, Campbell

. An exercise intervention to prevention falls in people with Parkinson’s disease: A pragmatic randomised controlled trial. J Neurol Neurosurg Psychiatry 2011;82:1232–8.

47.

Allen

, Canning

, Sherrington

, et al. The effects of an exercise program on fall risk factors in people with Parkinson’s disease: A randomised controlled trial. Mov Disorder 2010;25:1217–25.

48.

Morris

, Iansek

, Kirkwood

. A randomised controlled trial of movement strategies compared with exercise for people with Parkinson’s disease. Mov Disord 2009;24:64–71.

49.

Ramaswamy

, Jones

, Goodwin

, et al. Quick reference cards (UK) and guidance notes for physiotherapists working with Parkinson’s disease. London: Parkinson’s Disease Society, 2009.

50.

Lindop

, Skelly

, Smith

. Evaluation of an Otago-based exercise group for people with Parkinson’s disease. Movement Disorders 2012;27(Suppl 1):916.

51.

Dibble

, Lange

. Predicting falls in individuals with Parkinson disease: A reconsideration of clinical balance measures. J Neourol Phys Ther 2006;30(2):60–7.

52.

Garber

, Friedman

. Effects of fatigue on physical activity and function in patients with Parkinson’s Disease. Neurology 2003;60:1119–24.

53.

Ravenek

, Schneider

. Social support for physical activity and perceptions of control in early Parkinson’s disease. Disabil Rehabil 2009;31(23):1925–36.

54.

States

, Spierer

, Salem

. Long-term Group Exercise for People with Parkinson’s Disease: A Feasibility Study. Journal of Neurologic Physical Therapy 2011;35(3):122–8.

55.

Creswell

, Plano Clark

. Designing and conducting mixed methods research. Thousand Oaks CA: Sage; 2007.

56.

Johnstone

. Mixed methods, mixed methodology: Health services research in practice. Qualitative Health Research 2004;14:259–71.

57.

O’Cathain

, Murphy

, Nicholl

. Why, and how, mixed methods research is undertaken in health services research in England: A mixed methods study. BMC Health Services Research 2007;7:85.

58.

Tanner

, Hubble

, Chan

. Epidemiology and genetics of Parkinson’s disease. In: Watts

, Koller

, editors. Movement disorders. Neurologic principles and practice. New York: McGraw Hill 1996; 137–60.

59.

Enright

, Sherril

. Reference equations for the six-minute walk in healthy adults. Am J Resp Crit Care Med 1998;158(5 Pt 1):1384–7.

60.

Berg

, Maki

, et al. Clinical and laboratory measures of postural balance in an elderly population. Arch Phys Med Rehabil 1992;73(11):1073–80.

61.

Tanji

, Gruber-Baldini

, Anderson

, et al. A comparative study of physical performance measures in Parkinson’s disease. Mov Disord 2008;23:1897–905.

62.

Duncan

, Weiner

, et al. Functional reach: A new clinical measure of balance. J Gerontol 1990;45(6):M192–197.

63.

Sofuwa

, Nieuwboer

, Desloovere

, Willems

, Chavret

, Jonkers

: Quantitative gait analysis in Parkinson’s disease: Comparison with a healthy control group. Arch Phys Med Rehabil 2005;86(5):1007–13.

64.

Smithson

, Morris

, Iansek

. Performance on clinical tests of balance in Parkinson’s disease. Phys Ther 1998;78(6):577–92.

65.

ATS statement: Guidelines for the six-minute walk test. ATS Committee on Proficiency Standards for Clinical Pulmonary Function Laboratories. Am J Respir Crit Care Med 2002;166(1):111–7.