Both intervention groups will receive weekly exercise classes and a home program for twelve months. The home programs will be reviewed monthly by a physiotherapist and modified if necessary.
Lower limb group
The lower limb intervention group will receive an exercise intervention designed to prevent falls, enhance mobility and increase physical activity. This will involve a weekly circuit-style group exercise class, a home exercise program and a walking program. Interventions will be tailored to an individual's functional ability and the nature and difficulty of exercises will be progressed regularly.
The lower limb group will undertake exercises from the WEBB program. Participants will participate in a weekly exercise classes conducted by a physiotherapist and will be asked to perform a home exercise program at least 3 times a week. The home program and exercise classes include a 45–60 min program of progressive balance, lower limb strengthening exercises and walking. The exercise classes and home program will include 5 minutes warm-up exercises. The lower limb extensor muscle groups, which act to prevent collapse of the lower limb (hip and knee extensors and ankle plantarflexors) will be targeted with exercises designed to enhance balance and muscle strength. The balance exercises include standing with a decreased base of support, forwards and sideways stepping/walking, and graded reaching activities in standing. Strengthening exercises will include sit-to-stand, forward or lateral step-ups onto a small block, semi squats and heel raises in standing. Resistance for strengthening exercises will be applied using weighted vests in a similar protocol to one which has been successfully used by people with multiple sclerosis in a home-based program . Standard principles governing frequency, volume, duration, intensity and progression of exercise will be applied .
Upper limb/cognition group
The upper limb/cognition intervention group will receive a weekly exercise class aimed at management and improved function of the affected upper limb and cognition, carried out in the seated position. They will also be given a home exercise program. The upper limb component of the intervention was designed and developed by one of authors RB. We postulate that this intervention may lead to improvements in upper limb function and cognition but is unlikely to affect change in falls and mobility. This study design will, therefore, enable assessment of additional benefits of the lower limb intervention over and above likely benefits of social aspects of exercise classes.
Participants will be instructed how to perform exercises safely with a stable object (such as a table) located nearby for additional support if required. Participants will be provided with a booklet containing safety precautions, instructions and photographs of exercises for use in exercise sessions at home. In addition, they will be provided with a logbook for recording exercises completed, effects of exercise (e.g. muscle soreness). Where appropriate, family members and/or carers, will be encouraged to assist with supervision and performance of the exercise program.
The primary outcome measures will be falls and mobility. Falls will be defined as "events that resulted in a person coming to rest unintentionally on the ground or other lower level, not as the result of a major intrinsic event or an overwhelming hazard" . Falls will be assessed by comparing the number of falls in intervention and control groups. The proportion of fallers in each group will also be compared. Falls will be monitored for one year with monthly fall calendars. All participants will receive monthly calendars on entry to the study, with instructions to record the following events: number of falls, visits to or by nursing and allied health personnel, general practitioner or specialists appointments and hospitalisations. Participants will be asked to return the completed calendar monthly at their weekly exercise class. If calendars are not returned, further contact will be made by telephone. Details of any falls (including how and where the fall occurred, injuries suffered, medical intervention required and limitations to activity as a result of a fall) will be verified.
Two aspects of mobility, walking speed and capacity will be assessed. Walking speed will be measured using the 10 m walk test. Participants will be timed as they walk at their comfortable speed over the middle 10 m of a level 14 m walk track. Walking capacity will be measured by the distance covered in the 6 min walk test. The test will be conducted over a 25 – 30 m level corridor and standardised instructions will be given to each participant prior to the test and standardised encouragement at each minute in accordance with the American Thoracic Society guidelines for the 6 min walk test . For safety, while administering this test, the assessor will walk slightly behind, and not beside, the participant so as to avoid influencing the participant's self selected walking pace.
Secondary outcome measures listed below will be collected on entry and at the end of the 12-month study period. These outcome measures will be
i) Falls risk assessed using the Physiological Profile Assessment 
ii) Physical activity assessed via a 7-day pedometer count
iii) Community participation using the Adelaide activity profile 
iv) Quality of life and well-being using the SF 12™ Version 2
v) Health service utilisation using monthly calendars
vi) Upper limb function using Items 6,7,8 of Motor Assessment Scale for Stroke  and the nine hole peg test 
vii) Cognition using the Montreal Cognitive Assessment .
The number of falls per person-year will be analysed using negative binomial regression to estimate the difference in fall rates between the two groups, adjusted for previous multiple faller status . The proportion of fallers between groups will be compared using the relative risk statistic. Between-group comparisons of final test performance for the continuously-scored outcome measures will be made using General Linear Models (ANCOVA) controlled for pre-test performance. Ordinally-scored data will be analysed for between group differences using the non-parametric Mann Whitney U statistic. An intention-to-treat approach will be used for all analyses.
As fall rates will be compared between groups using incident rate ratios (IRR) from negative bionomial regression models  we conducted an analysis of statistical power using the nbpower command in the STATA software package. A total of 350 participants (175 per group) will be recruited. The study will have 80% power to detect as significant at the 5% level a 34% reduction in the rate of falling (i.e. an IRR of 0.66 using negative binomial regression analysis) in the 12 month follow-up period. This allows for a 15% loss to follow-up due to death or withdrawal from the study. Experience from our previous work indicates that, with this sample size, power will also be sufficient to detect meaningful between-group differences for all other outcome measures [9, 15, 16].