Intervention groups:
Remotely-supported exercise group:
The remotely-supported group will received a target for a total duration of exercise each week (outdoor walking) progressing in duration from 105 to 150-min and 55% to 70% of V̇O2max. By week 7, the exercise prescription will align with common physical activity recommendations. Participants will be advised how they can break down their target into manageable bouts (e.g., 3 × 35 min walks = 105-min in week 1) and will be instructed to accumulate exercise with a minimum bout-length of 10-min. Intensity will be checked by participants using heart-rate thresholds that corresponded to their V̇O2max. Participants will take part in a weekly 30-min telephone calls to discuss the exercise they have completed, as documented by an internet-based data visualisation platform with data input from a wrist worn fitness tracker that records accelerometry data and heart rate
Partly-supervised exercise group:
The partly-supervised exercise group will undertake 2 supervised (laboratory-based treadmill and cycle ergometer exercise) and 1 unsupervised session per week (e.g., outdoor walking) progressing from 35 to 50-min and 55% to 70% of V̇O2max. By week 7, the exercise prescription will align with common physical activity recommendations. During supervised laboratory sessions, intensity will be confirmed and adjusted using indirect calorimetry. The intensity of unsupervised exercise sessions will be recorded using a chest-worn heart rate monitor.
Participant characterisation:
Participants will attend a laboratory for characterisation before and after the intervention (within 7 days) following a 10 hour overnight fast and after refraining from exercise, alcohol, and caffeine in the prior 24 hours. Body mass and height will be measured with the participant wearing light clothing. Body composition monitor. Dual-energy X-ray absorptiometry will be used to quantify fat mass, lean mass, and bone mineral density parameters. Blood pressure will be measured using an automated sphygmomanometer following 15 minutes rest in the supine position.
Physical function will be assessed using three tests. First, the 6-minute walk test, whereby participants will walk as far as possible in 6-minutes between two cones placed 7 meters apart. Second, the sit to stand test, whereby participants will perform as many sit-to-stands as possible in 30 seconds (i.e., seated on a standardised chair, rising to reach full knee extension, returning to a seated position, arms folded across the chest). Third, the 8 foot up timed up and go test, whereby participants will rise from being in a seated position on a standardised chair, walk 8 feet, and return to a seated position as quickly as possible.
Cardiorespiratory fitness will be assessed using a treadmill-based maximal walking exercise test to exhaustion comprising 3-minute stages, beginning at 2.7 kph with a 1% gradient and increasing by 1.3 kph until 6.6 kph, with further intensity increments via increasing gradient by 2%. During the final minute of each stage, heart rate will be measured using telemetry and rating of perceived exertion will be recorded. Expired air samples will be collected using Douglas bags during the final minute of each stage. Oxygen and carbon dioxide within each bag will be analysed using a gas analyser and volume and temperature of the air will be assessed using a digital thermometer and dry gas meter.
