Breaking up prolonged sitting with walking and brief simple resistance activities for the management of Type 2 Diabetes: The REWARD Study.

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Sedentary behaviours have become a predominant feature of most adults waking hours. Specifically, prolonged sitting time is now understood to have adverse effects on glycaemic control and other health parameters, adversely impacting on those with Type 2 Diabetes (T2D). Physical activity, including structured resistance exercise, is recommended for the treatment and management of T2D. Resistance activities utilise the larger muscle groups, potentially providing a greater stimulus for glucose uptake; however, many people with T2D may be unable or insufficiently motivated to meet these recommendations. Encouraging recent evidence shows that walking breaks throughout the day are an effective strategy to offset the deleterious effects of prolonged uninterrupted sitting in older, overweight adults. However, these experimental findings are yet to be verified in those with T2D – who could derive the greatest benefit. This study will examine the acute effects of a single bout of prolonged sitting on postprandial blood glucose, insulin and lipids with and without intermittent bouts of light-intensity walking or simple resistance activities in adults with T2D. Twenty four inactive and injury free participants aged between 35-75 years with diagnosed T2D (longer than 3 months) who are either diet or Metformin controlled will be recruited. Participants will visit the lab on 5 separate occasions. First, they will attend a 120 minute screening and medical exam, then a 60 minute familiarisation session one week prior to the commencement of the experimental trial. During screening, participants will complete a standard Glycated Haemoglobin (HbA1c) test to verify diabetes status (>=6.5%, but <=9%) and will be assessed on their suitability and safety to participate in the study. Familiarisation will ensure they are comfortable with the equipment and exercises, and suitable technique and movement consistency are achieved. The energy expenditure of the two activity breaks will also be measured a this visit. Participants will then complete three experimental conditions in a random order (each 8 hours duration with an initial 1 hour steady-state period) separated by a minimum 6 day washout period. The experimental conditions are: (A) Uninterrupted sitting (control condition): Participants will sit quietly in a lounge chair for 8 hours, with breakfast and lunch provided during this period; (B) Sitting + light-intensity walking breaks: Following baseline measurements and after sitting quietly for 1 hour (steady state) and allowing for consumption of the breakfast meal (20 minutes), participants will complete a 3 min bout of light-intensity walking on the treadmill (level, firm surface, slow pace – 3.2 km.hr-1). They will then return to the seated position. This procedure will be repeated on a further 11 occasions every 30 min (except where a lunch meal is consumed) for a total of 36 min of light-intensity activity; (C) Sitting + simple resistance activities: Identical procedure to condition B, however, participants will complete a 3 min bout of simple resistance activities. The activities will be allocated into nine 20 second segments, alternating between body weight half-squats, calf raises and brief gluteal contractions in-between single leg knee raises. This interchange between movements will provide rest for the corresponding muscle groups between each activity segment. To ensure appropriate standardisation, participants will complete each activity in a controlled manner within their range of motion (knee/hip 45 to 90° for half-squats/knee raises). Exercise tempo and correct ‘form’ will be achieved by participants mimicking a pre-prepared video recording, with which they have been previously familiarised. Fasting and postprandial blood samples (glucose/lipids, insulin/C-peptide, incretins, catecholamines and full blood examination) will be measured half-hourly throughout each trial, while blood pressure will be collected at each hour time point. Perceived fatigue will be assessed every 2 hours. With high volumes of sitting becoming a growing concern, there are potentially important and practical benefits of breaking up sitting time with brief bouts of light intensity activities. This research will provide insights into whether breaking up sitting time with light intensity walking and simple resistance activities has the potential for health benefits in those with T2D. The results of this study have potential to provide more detailed, practical and potentially prescriptive information to help shape clinical and public health approaches in T2D.