The effect of exercise and physical activity on physical fall risks

For older adults, accidental falling produces significant morbidity and mortality,being responsible for personal costs as well as cost to the community at large. The propensity to fall is dependent on a combination of factors that include intrinsic characteristics of each individual as well as environmental influences. Many intrinsic physical fall risk factors are modulated by changes in physical activity levels or exercise interventions. These physical performance fall risk factors include muscle strength, flexibility and balance. The studies that comprise this thesis examine several interventions designed to impact physical fall risk factors, as well as measuring natural seasonal changes in strength, balance and activity in communitydwelling older adults. The first study (Study I) investigated the benefits on balance of participating in a 16-week community-based resistance and flexibility program in an observer-blinded randomised crossover trial. Static and dynamic balance and lower limb strength were measured. Significant improvements in sway velocity, as well as Timed Up and Go, Ten Times Sit-to Stand and Step Test were observed with both interventions (all P<0.019), with no significant differences between the two groups. Resistance training also resulted in significant increases in strength (P<0.001), that were not evident in the flexibility intervention. A subsequent study (Study II) examined the longer term effects of this multicomponent exercise program (Study I) on balance, mobility and exercise behavior 12 months after completion. Differences between those participants who continued to exercise and those who discontinued were investigated. Significant improvements from baseline in Ten Times Sit-to-Stand (P<0.001), Timed Up and Go (P=0.001), and sway velocity (P<0.001) remained at follow up in the exercise intervention group, with a control group remaining unchanged. Participants from the intervention who continued exercising had significantly greater improvements in strength immediately after the intervention, compared to those who discontinued (P=0.004). Benefits to balance and mobility persisted one year after participation in the multicomponent exercise program, due in part to some continuing participation in resistance training. The third study (Study III) evaluated the effects of a Pilates intervention on balance and function in 32 participants in a randomised crossover study design lasting 16 weeks. Static and dynamic balance measures (medio-lateral sway range, Four Square Step Test, Timed Up and Go) and leg strength were recorded. There were no significant differences between Pilates and control groups for any of the measured variables (P>0.05), despite static and dynamic balance significantly improving over the duration of the study and from pre- to post-Pilates (P<0.05), and no significant changes occurring during the control phase. The absence of differences between conditions may be a result of our small sample size or the crossover study design, indicating that Pilates may produce neuromuscular adaptations of unknown duration. Studies IV and V investigated seasonal variation in lower limb strength and balance respectively in a longitudinal repeated-measures study design concurrently with serum vitamin D and physical activity. Fall incidence, cause and any adverse outcomes were recorded using a monthly prospective fall calendar. Mixed-methods Poisson regression was used to determine associations between the data. Eighty eight community-dwelling older adults were evaluated five times over a one-year period. Significant variation in vitamin D (±15%), physical activity (±13%), ankle dorsiflexion strength (±8%) and hours spent outside (±20%) (all P<0.001) was demonstrated over the year, with maximum levels of each measure occurring in January (mid-summer). Quadriceps strength did not change over time (±2%; P=0.53). Incidence of falls (P=0.01) and injurious falls (P=0.02) were lower in spring than in any other season. Postural sway did not vary over the year. Small but statistically significant (P<0.001) changes in dynamic balance (4%) were observed over the year. Reduced mean ankle strength was associated with increased incidence of falling (P=0.047). Increased ankle strength in summer may be influenced by increased levels of activity over summer months, especially time spent outside. Reduced ankle dorsiflexor strength in winter may predispose older people to increased risk of tripping related falls at this time of year. The engagement of older-adults in exercise programs and increased levels of physical activity (especially outdoors) have important consequences for addressing age-related decline in aspects of physical functioning related to fall risks. The studies described in this thesis have added to the type of exercise programs that have achieved positive outcomes with randomised-designed studies. This gives older people and health practitioners greater options for exercise, which can be important for uptake and sustained engagement in exercise programs. Additionally the seasonal variation in dynamic balance and ankle dorsiflexion strength are novel findings that practitioners and policy makers need to consider in making recommendations regarding outdoor activity and sunlight exposure for older adults.