Acute lower body exercise elicits adverse effects on balance performance and subsequent fall risk. However, little information exists for upper body exercise and postural sway. The series of experimental studies presented in this thesis investigated the effects of acute upper and lower body exercise on postural sway in healthy young and older adults and determined whether the acute negative effects of exercise can be removed by an improvement in training status. Chapter 4 examined the effects of maximal and submaximal (absolute and relative exercise intensities) arm crank ergometry (ACE) and cycle ergometry (CE) on postural sway in young healthy adults. Cycling elicited an immediate increase in post exercise postural sway whereas ACE did not. Chapter 5 compared the effects ACE, CE and treadmill walking (TM) on postural sway in healthy older adults. Based on the findings of Study 1, submaximal exercise was performed at the same relative intensity (50 % HRE). In agreement with Chapter 4, CE and TM elicited post exercise balance impairments lasting for ~ 10 min post exercise. ACE performed at the same relative intensity as the lower body did not elicit post exercise balance impairments in older adults. Collectively, these acute studies suggest that lower limb exercise may acutely increase fall and injury risk in the immediate period after exercise cessation. This is important because practitioners and clinicians should acknowledge that the prescription of conventional training modes might potentially elicit transient impairments in neuromuscular function. However, in this context it appears that seated exercise with the arms may not induce a significant enough stimulus to cause sensorimotor disturbance to postural stability and thus may be a safer alternative exercise mode for fall risk populations or individuals who are very sedentary. Chapter 6 examined differences in balance performance, as measured by quantitative posturography and functional balance tests, among different age groups. Measures of postural sway were able to distinguish between younger (< 60 years) and older (> 60 years) adults whereas functional performance tests suggested that balance impairments were observed earlier (> 50 years). This study enabled a range of tests to be determined for use with subsequent training interventions. Chapter 7 examined the effects of 6-weeks upper or lower body exercise training on postural sway. Upper and lower body training elicited similar improvements in specific (~ 25 %) and cross transfer (~ 12 %) exercise tolerance. Both modes of training elicited favourable balance adaptations. Specifically, upper body training improved mediolateral aspects of postural sway, while lower body training improved anteroposterior aspects of sway. It was proposed that an improvement in cross transfer exercise capacity after upper body exercise reduced the physiological strain experienced during CE, thus reducing post exercise balance impairments and that an increase in abdominal and trunk strength from upper body exercise training reduced sway following ACE. Importantly, ACE also elicited an improvement in functional reach distance and timed up and go test speed. Conversely, CE improved lower limb strength which elicited an improvement in lower body dynamic balance. It is likely that engaging in both upper and lower body exercise will be better that either mode of exercise alone for both health and fitness and balanced incorporated in everyday life. ACE elicits a number of significant benefits to cardiovascular fitness and balance which is important for a number of older subgroups who might have difficulty engaging in lower limb exercise, such as those who are very sedentary, those with lower limb injury/disease or undergoing surgery rehabilitation and individuals who are overweight. Specifically, ACE may offer a pathway from sedentary living to physical activity. Upper body endurance exercise can contribute to a multimodal training stimulus by eliciting favourable adaptations in fitness, functional performance and balance. Such responses are important because this type of exercise may serve a feasible and time-efficient training regime for older adults, which will likely result in improved attrition and adherence to physical activity.