The influence of high impact exercise on musculoskeletal health in older men

There is little evidence as to whether exercise can improve the musculoskeletal health of older men, with no investigation of high impact exercise. This research compared the multiple joint muscle function of young (n=21) and older men (n=23) and then investigated the feasibility and influence of high impact, unilateral exercise on lower-extremity muscle function (in 3- and 6-month intervention trials) and proximal femur strength (in a 12-month intervention trial) in healthy community-dwelling older men (n=112). In study one, young and older men performed isometric (maximum and explosive) and dynamic contractions on a leg press dynamometer instrumented to record force and displacement, from which the force-velocity and power-velocity relationships were assessed. The results demonstrated that force (-20%) and velocity (-11%) were lower in older men, with the decrement in force being the major explanation for the attenuation of power during a functionally relevant multiple joint movement. During study two, in addition to the previous muscle function assessments, hop performance (net impulse) and static unilateral balance were measured before and after a 3-month high impact, unilateral exercise programme (home-based and supervised group sessions) in older men (n=20). The feasibility of this type of exercise in older men was also determined. The intervention appeared safe and feasible with no adverse effects, however there was no effect on muscle function. In study three, the influence of a longer-term (6-months) high impact, unilateral exercise intervention on muscle function was investigated in older men (exercise group n=39, control group n=18). The specific functional measurements included hop performance (net impulse), ankle plantar and dorsiflexion strength, leg press strength and static unilateral balance. Improvements in net hop impulse (12%), isometric leg press strength (4%), ankle plantarflexion strength (11%) and static unilateral balance (45%) were noted following the intervention. In studies four and five, the effect of a 12-month high impact, unilateral exercise programme on bone strength was investigated. Fifty, older men commenced the training which increased to 50 multidirectional hops, 7 days a week on one randomly allocated leg [exercise leg versus control leg]). Dual energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) scans were performed before and after the intervention. The results from study four revealed that femoral neck areal bone mineral density (aBMD) and bone mineral content (BMC) modestly increased in the exercise leg (n=35; +0.7 and +0.9%) compared to the control leg (n=35; -0.9 and -0.4%) following the intervention. In study five, a segmental QCT analysis of the mid-femoral neck was applied to explore regional changes in cortical thickness in response to the high impact training. The findings demonstrated that cortical thickness increased in the super region at the mid-femoral neck (15-52%), thus producing a greater localised thickening of the cortex. The research presented in this thesis provides a comprehensive evaluation of the influence of high impact exercise on musculoskeletal health and suggests that carefully targeted high impact exercises may be suitable for incorporation into exercise interventions aimed at preventing hip fracture in healthy community-dwelling older men.