Do different ways of applying limb pressure alter blood flow in older adults using blood flow restricted exercise training?

INTERVENTION: In this experimental study, each participant will experience four experimental conditions, randomised over two days (two conditions each day; two 90‐minute sessions separated by 48 hours each). In each experimental condition, participants will perform five minutes of low intensity cycling (9‐11 on the Borg Rating of Perceived Exertion Scale), using a portable cycling pedal (Dual Exercise Bike, Bodyworx, Australia) while seated in an upright chair. Prior to and during cycling, participants will have an inflatable cuff (Achedway, Australia) placed on the proximal portion of both thighs, which will be inflated to a pre‐specified pressure dependant on the experimental protocol. There will be a 10‐minute rest interval between each experimental condition conducted on the same day. Experimental conditions: Four different approaches to lower limb blood flow restriction will be used. For each of the four conditions, prescription of pressure in the inflatable cuffs (Achedway, Australia) placed on the proximal portion of both thighs will differ depending upon the experimental condition where: Approach 1 (Control) = 50% of limb occlusion pressure; Approach 2 = perception of cuff tightness (rating of 7 on a 0‐10 scale where 0 means ‘Not tight at all’ and 10 means ‘Unbearable tightness’); Approach 3 = pressure calculated as 1.3 x systolic blood pressure measured at rest on day one; and Approach 4 = standardised pressure of 160 mmHg. The intervention will be delivered face‐to‐face in a laboratory at the City East Campus of University of South Australia by a physiotherapist with four years of clinical experience with older individuals, and more than five years of experience with blood flow restricted exercise (BFRE) in the research setting. We will record adherence to i CONDITION: Cardiorespiratory function;Vascular function; ; Cardiorespiratory function ; Vascular function Cardiovascular ‐ Normal development and function of the cardiovascular system Physical Medicine / Rehabilitation ‐ Physiotherapy Respiratory ‐ Normal development and function of the respiratory system INCLUSION CRITERIA: Participants will be eligible for inclusion in this study if they are 50 years of age or greater. PRIMARY OUTCOME: Absolute values of peripheral blood flow (ml/min). To assess this outcome, peripheral blood flow as assessed via sonography of the anterior and posterior tibial arteries (IU22 ultrasound machine, linear array 12‐9 MHz transducer, Phillips Healthcare, Bothell, WA, USA).[The endpoints are peripheral blood flow absolute values Immediately before exercise (baseline), immediately following exercise with the cuffs inflated (primary endpoint) and immediately after cuff release.] Change scores in peripheral blood flow (%). To assess this outcome, peripheral blood flow as assessed via sonography of the anterior and posterior tibial arteries (IU22 ultrasound machine, linear array 12‐9 MHz transducer, Phillips Healthcare, Bothell, WA, USA).[The endpoints are peripheral blood flow change scores from baseline to immediately following exercise with inflated cuff (primary endpoint) and from baseline to immediately following cuff release.] SECONDARY OUTCOME: Breathing discomfort. To assess this outcome the A1 item of the Multidimensional Dyspnea Profile will be used.[Immediately before exercise, at the final minute of exercise (fourth minute), immediately following exercise with inflated cuff and immediately after cuff release.] Perceived tightness that will be assessed using a 0‐10 numeric scale (0 – ‘No tightness at all’ and 10 – ‘Unbearable tightness’).[Immediately before exercise, at the final minute of exercise (fourth minute), immediately following exercise with inflated cuff and immediately after cuff release.] Peripheral muscle discomfort that will be assessed using a 0‐10 numeric scale (0 – ‘No discomfort at all’ and 10 – ‘Unbearable discomfort’).[Immediately before exercise, at the final minute of exercise (fourth minute), immediately following exercise with inflated cuff and immediately after cuff release.]