The (i)mpact of (H)igh (I)ntensity intermittent (T)raining on health and mechanisms of insulin resistance in women with (P)oly(c)ystic (O)vary (S)yndrome: The iHIT-PCOS randomised control trial.

Women will be randomized into the control and 2 exercise intervention groups. Three weeks prior to the exercise intervention phase women in all groups will undertake a behavioural lifestyle intervention: an adapted, evidence based lifestyle behavioural intervention will be provided to all participants to i) ensure exercise is provided in context of combined behavioural and dietary intervention and ii) to optimise retention, engagement, motivation and sustainability of exercise. This program includes provision of healthy eating advice and health promotion behaviour change principles resulting in improved retention (~10% attrition rates in 3 large prior RCT’s compared to standard ~30% dropout rates). This involves 3 x 1 hour group sessions (1 session per week over 3 weeks) focused on diet information and behavioural modification techniques based on social cognitive theory including goal setting, self-monitoring, social support, coping strategies, problem solving and relapse prevention . Non-prescriptive and non-individualised dietary advice is provided consistent with the Australian Dietary and Healthy Eating Guidelines with a focus on healthy food choices, reducing intake of energy-dense and non-core foods and increasing intake of low energy-dense foods. These sessions encourage physical activity (low intensity exercise for 150 minutes/week) but do not include structured exercise. Lifestyle sessions will be provided by trained accredited exercise physiologists (AEPs). Exercise treatments: Exercise will be conducted in group setting on stationary bikes or treadmills according to the participant’s preference; and exercise intensities prescribed and monitored using heart rates. Sessions will be conducted at the university fitness centre/ exercise clinic under the supervision of AEPs, Volume matching and training progression: The supervised standard exercise recommendation (SSE) and High intensity intermittent training (HIIT) intervention arms will be matched for training volume (MET.min/week) and progressed weekly by manipulating session time and intensity. Both SSE and HIIT will progress from 312 MET.min/week in week 1 to 530 MET.min/week in weeks 8-12, meeting exercise guideline minimums. Exercise sessions include warm-up and cool down protocols, and are adjusted to individual capabilities and training adaptations. In addition to lifestyle intervention and wearable technology, details of the three exercise treatment arms are: i) Control Group: Exercise advice but without structured exercise as per standard care. ii) SSE Group: Supervised standard exercise recommendations at minimum exercise/ physical activity recommendations (150 min per week) in three supervised sessions/week of continuous low to moderate intensity exercise sessions (building up to 50 min sessions of cycling/walking at 3.3 METs or 50-60% HRR). iii) HIIT Group: Vigorous exercise at minimum exercise/physical activity recommendations (~75 min per week) in three supervised sessions/week of HIIT exercise (cycling/running). Based on existing literature and patient consultation, we will use a practical training program encompassing two successful HIIT protocols: * two sessions/week of short constant load cycling of 8–12 x 1 min at ~9METs (or 90-95% HRR) with 1 minute passive recovery * one session/week of cycling/jogging/running 4–8 x 4 min at 8 METS (or 70-85%HRR) with 1 minute passive recovery. These HIIT sessions have proven feasible, enjoyable, and are safe in populations with significant metabolic disease and in the pilot study in overweight PCOS women, and is best tolerated with progressive weekly increases, as per best-practice exercise prescription principles.