Physiological and Cognitive Responses to Isometric Resistance Training in Individuals Experiencing Memory Difficulties or with Mild Cognitive Impairment

Abstract

Dementia is the second leading cause of death in Australia and the greatest cause of disability in people aged 65 years or older. On a global scale, it is estimated that there are more than 46.8 billion people living with dementia at an estimated cost of $815 billion USD. Alzheimer's disease (AD) is the most common form of dementia diagnosed amongst the elderly and Mild cognitive impairment (MCI) is a condition often indicative of the earliest symptomology of AD. Recent investigations report that individuals with a history of vascular risk factors (VRF) such as hypertension are high risk candidates for cognitive decline in later life, and that VRF promote progression from MCI to AD. Research suggests that isometric exercise training (IET) promotes anti-hypertensive effects and improved vascular endothelia functioning. It may be the case that IET has the potential to prevent, reduce, or attenuate the adverse effects that VRF have on cognitive performance outcomes and progression to AD. This thesis investigates cognitive and physiological responses to IET in elderly individuals experiencing memory impairment, MCI or AD. <b>Methods:</b> First, a meta-analysis was conducted to review the impact of exercise on cognitive performance outcomes. Second, in consideration of the frail and elderly who might struggle with IET at 30% maximal voluntary contraction (MVC), a randomised study was conducted in an attempt to determine the minimum anti-hypertensive threshold intensity for IET. Finally, we ran a small pilot-case-study to assess the impact of IET at 20% MVC on cognitive performance outcomes in elderly individuals experiencing memory impairment or diagnosed with AD. <b>Outcomes:</b> Physical activity provides significant improvements in some domains of neurocognitive functioning. The results of a randomised trial indicated that 6 weeks of low intensity (5% and 10% MVC) IET elicited reductions in systolic blood pressure (BP) similar to the antihypertensive effects observed in monotherapy of 5 – 7 mmHg. The results of four pilot case-studies reported that overall cognitive functioning remained stable for all but one participant; however, IET did not reduce resting BP after 3, 5 or 6 weeks of IET at 20% MVC. <b>Conclusions:</b> Physical activity improves neurocognitive function in people with cognitive impairments. In Individuals unable to complete isometric exercise at 30% MVC, our results suggest both 5% and 10% MVC may offer clinically relevant anti-hypertensive effects. Isometric exercise at 20% MVC does not reduce resting BP in elderly medicated hypertensives after 3, 5 or 6 weeks of training. Improvements in cognitive performance measures were not attributed to the anti-hypertensive effects of IET and may be attributed to increased social interaction or neurohormonal pathways not necessarily associated with BP reduction.