28 Cardiorespiratory Regulation and Aerobic Fitness in Older People – A New Approach for Falls Interventions?

Guidelines for physical activity give recommendations for moderate to vigorous aerobic training 2-3 times per week. Aerobic exercise, like walking, shows mixed effects in regard to falls prevention. However, after high intensity exercise postural stability is decreased and better aerobic fitness might be relevant to minimize this fall risk in older individuals. So far, the association of aerobic fitness and falls has not been examined in older people. Feasible methodology is lacking. Aerobic fitness can be assessed measuring cardiorespiratory (heart rate [HR] and oxygen uptake [V’O2]) regulation in response to changing submaximal work rate (WR) intensities. For cycle ergometry (cycling) cardiorespiratory regulation correlated with aerobic fitness. Since treadmill walking (TMW) is closer to daily life activities, TMW is tested for feasibility in older people and compared to data during cycling. Methods 17 participants (65±6 years, 23.9±3.8 kg∙m-2) were tested for V’O2 and HR regulation during cycling (30W, 80W) and TMW (1.9 km·h-1, 5 km·h-1). Inclination during TMW was matched to WR during cycling. Additionally, WR was further increased until the first ventilatory threshold (VT1) was reached. Kinetics were assessed applying cross-correlation functions (CCF). Higher maxima in CCF (CCFmax () in a.u.) imply faster system responses. T-tests were applied to calculate differences between the exercise modes. Correlations were computed using Pearson tests. Results Significant differences for CCFmax (V’O2) were identified between cycling and TMW (0.51±0.10 vs. 0.45±0.08; p=0.032), but not for CCFmax (HR) (cycling: 0.62±0.13; TMW: 0.60±0.10; p=0.623). CCFmax (HR) during TMW correlated with V’O2 at VT1 during TMW (r=0.538, p=0.013). Discussion TMW is feasible to adequately determine cardiorespiratory regulation and correlated with aerobic fitness in older people and has a better applicability. Hence, cardiorespiratory regulation might be an important factor to assess in the context of falls.