The Feasibility of an 8-Week High-Intensity Interval Training (HIIT) or Concurrent Training (CT) Programme in Overweight and Obese Adult Males

This study will incorporate a randomised controlled design, involving three distinct phases for two separate groups of participants. Participants will be randomly assigned into one of four groups via a computerised randomiser (Sealed Envelope Ltd., 2020), with a 1:1 allocation ratio using block sizes of two. These groups will consist of a HIIT group and concurrent training group. Three phases will be spread across 10 weeks for each participant:

• Phase 1: baseline testing for all groups (week 1)
• Phase 2: an 8-week exercise intervention for three experimental groups (weeks 2 - 9)
• Phase 3: post-intervention testing for all groups (week 10). Participants will be provided with all of the study information and given the opportunity to ask questions from the researchers before providing informed consent. Full pre-exercise screening in accordance with the American College of Sports Medicine (ACSM) guidelines for exercise testing will be conducted. All participants will be overweight or obese (BMI > 25 kg.m2) and sedentary but will be excluded if pre-exercise screening highlights any other cardiovascular disease risk factor.

Phase One: Baseline Testing Once included in the study, participants will be randomised into one of two groups (HIIT or Concurrent). Both groups will perform exactly the same baseline testing procedures over the course of two days during Week 1 of the study duration. On the first day participants will arrive at the University of Sunderland exercise testing laboratory having completed a 12 hr fast, having abstained from caffeine and alcohol consumption for 24 hr and not exercised in the previous 72 hrs, and asked to consume 500 ml of water 1 hour prior to arrival.

Fasted blood samples will then be collected. Plasma glucose, lipid profile and HbA1C concentrations will be assessed via a fingertip capillary blood sample. Each fingertip capillary sample will be performed using a safety lancet. Blood samples will be immediately analysed and disposed of in clinical waste. Samples will be analysed via a CardioChek PA portable lipid analyser, HemoCue Hb analyser and Biosen blood glucose analyser. Once sterilised with an alcohol wipe, skin perforations will only be made on the fingertips, and participants will be provided with adhesive dressings should they be requested. There will then be a short break (~30 minutes) in which participants will be provided with a light breakfast of toasted white bread (50 g) with strawberry jam (40 g), constituting a total of 75 g Carbohydrate. After consuming the breakfast participants will score their appetite via a visual analogue scale (Flint et al., 2000). The breakfast will standardise pre-exercise nutritional status both between- and within-participants.

Pre-exercise health screening will be completed in line with American college of sports medicine (ACSM) and University of Sunderland guidelines. Inclusive of this screening procedure will be anthropometric measures (height, mass, waist and hip circumference) as well as resting heart rate (determined via a Polar heart rate monitor and wristwatch) and resting blood pressure (via automatic sphygmomanometer). Participants will be excluded upon evidence of any contraindications to exercise (ACSM, 2020). In addition to this, body fat will be determined via the BodyStat 1500 bioelectrical impedance device. This will not occur if the participant has any form of pacemaker device. Hydration status will be determined prior to bioelectrical impedance via an Osmocheck portable analyser.