Study overview
A detailed description of the protocol for this RCT has previously been published [
6]. Briefly, this study was a 24-week intervention in which participants were randomly allocated to either: (1) the
Lift for Life® community-based PRT program combined with additional whey-protein and vitamin D supplements, or (2) the
Lift for Life® PRT program alone. The primary outcomes were glycated haemoglobin (HbA
1c) and homeostasis model assessment 2 (HOMA-2) of insulin resistance and beta-cell function. Secondary outcome measures included changes in: body composition, muscle strength, blood pressure, blood lipids, adipokines and inflammatory markers, growth factors, health-related quality of life and cognitive function.
All participants enrolled in the trial were asked to complete the
Lift for Life® PRT program in local community health and fitness centres, which involved training twice a week for the first 8 weeks and three times a week thereafter. Training sessions were supervised by qualified trainers, and lasted approximately 45 to 60 minutes, and consisted of moderate to high intensity PRT (three sets of eight to ten repetitions) targeting all major muscle groups and with an emphasis on progressive overload (increments in weight of 2–10 % per week). All participants were charged a fee (AUD$3–$12) by their local health and fitness provider to undertake the program, but were eligible for reimbursement up to the value of AUD$240 at the completion of the study based on their level of compliance [
6].
Those randomised to the
Lift for Life® plus supplement group were also provided with a supply of a whey-protein-enriched powder and vitamin D supplements [
6]. Participants were instructed to prepare and consume the whey-protein drink (20 grams of whey protein concentrate 80 % with 150 ml of cold water) every morning prior to breakfast and consume a subsequent whey-protein drink within 2 hours of each
Lift for Life® training session. They were also required to consume two vitamin D capsules (1000 IU vitamin D
3) each day. The PRT alone group received no additional powder or supplements.
Throughout the trial, participants were required to attend Deakin University for approximately 2 hours on two occasions (baseline and 24 weeks). Research staff conducted on-site testing at each health and fitness centre after 12 weeks. A rested morning (8–10 am) venous blood sample was additionally collected at an accredited pathology laboratory following an overnight fast on three occasions over the 24-week period (baseline, 12 and 24 weeks).
Sample size calculations
As previously published [
6], it was estimated that a sample size of 168 participants would provide the study with 90 % power (
P < 0.05 two-tailed test) to detect a 0.5 % absolute difference for the change in HbA
1c levels between the groups, assuming a conservative standard deviation of 1.1 %. For insulin sensitivity, a sample size of 140 would be required to detect a 0.7 difference for the change in HOMA-2 insulin resistance between the groups at a power of 90 %, assuming a conservative standard deviation of 1.2. To compensate for an estimated 20 % drop-out rate, it was calculated that 202 participants would be recruited to the study and randomised 1:1 to either of the two groups (101 participants per group).
Ethics
This trial was managed by staff within the Institute for Physical Activity and Nutrition (IPAN) at Deakin University Burwood, Melbourne, VIC, Australia and funded by a National Health and Medical Research Council Project Grant (ID1046269). The study was approved by the Deakin University Human Research Ethics Committee (HREC 2013-050), and is registered with the Australian and New Zealand Clinical Trials Registry (ACTRN12613000592741). All participants provided written informed consent prior to their commencement in the study.
Screening and eligibility criteria
As reported previously [
6], eligibility for this study was assessed using a two-step screening process. Briefly, participants were screened via a telephone questionnaire and ineligibility was based on the following criteria: (1) aged <50 or >75 years of age; (2) HbA
1c >10 %; (3) current or prior participation in a structured resistance training program >1 week or moderate-intensity physical activity ≥150 min/week in the previous 3 months; (4) vitamin D or calcium supplement use >500 IU/day and >600 mg/day, respectively, in the previous 3 months; (5) severe orthopaedic, cardiovascular or respiratory conditions that would preclude participation in an exercise program, or those with absolute contraindications to exercise, according to American College of Sports Medicine (ACSM) guidelines [
7]; (6) renal impairment (estimated glomerular filtration rate (eGFR) <45 ml/(min 1.73 m
2)) or disease; (7) regular use of protein supplements; (8) conditions that may affect vitamin D or calcium metabolism; (9) current smoker, or (10) body mass index (BMI) >40 kg/m
2. Participants who passed the initial telephone screening were then required to obtain approval from their doctor to clear them of any medical conditions contraindicated to exercise, based on ACSM guidelines. Participants were also required to provide a fasted, morning blood sample to confirm that their HbA
1c level was <10 %.
Recruitment strategies
During the trial establishment period, the research team met to develop a recruitment plan. The initial strategies adopted were similar to those which had been used previously by the trial staff in other lifestyle-related interventions. These included local newspaper advertisements, distribution of flyers/posters to relevant health professionals and community groups and GP presentations. Within the first 2–3 months, expressions of interest (EOIs) and recruitment of participants was modest, at which point the research team consulted with the Deakin University public relations and communications team to discuss the trial advertisements and communications approaches and how they could be improved. A number of new recruitment strategies, in addition to those already in use, were then implemented to recruit participants from metropolitan Melbourne and within a 50 km radius of Deakin University in Burwood, VIC, Australia as well as surrounding regional areas including Geelong, VIC, Australia. Such strategies included state and local newspaper and radio advertisements, targeted mail-outs through the National Diabetes Support Scheme (NDSS) member database, GP and allied health professional referrals, community presentations, web-based media and word of mouth. A brief overview of each of the approaches is presented below. For each participant, specific information relating to the method of recruitment was obtained during the initial screening (telephone) session.
A total of six paid advertisements were placed in leading state-wide newspapers, with the advertisements ranging in size, colour and placement within each paper. The content of these advertisements included an eye-catching headline, a brief and simple description of the trial, including the potential health benefits to participants associated with participation, and relevant contact details. The cost for these advertisements ranged from AUD$1700 to AUD$3000 each.
Twelve paid advertisements, similar in format to the state-based advertisements, were also placed in a range of local municipality newspapers, which are delivered weekly to each household within a given area (municipality). In general, these advertisements were placed in the same paper fortnightly over a 6-week period, however, occasionally single advertisements were used to trial and target one locality to gauge the level of interest. The cost for the local paper advertisements ranged from AUD$400 to $500 each depending on the size and placement of the advertisement within the paper. A number of free advertisements were also placed in local newspapers in the community ‘What’s On’ section (limited to 40 words). These free advertisements were used as a buffer to continue the recruitment campaign between paid state and local media advertisements.
Radio advertising
The study was also advertised on a state-wide radio station. Forty-five, 15-second paid advertisements, which were drafted by study researchers and refined by the radio station, were played over a 5-day period (Monday to Friday). The radio station was selected based upon the demographics of the majority of their audience (e.g. middle-aged and older adults). The advertisements were initially played during the ‘Seniors Spotlight on Trials and Studies’ segment and thereafter were spread sporadically over the course of the day ranging from 6 am through to 10 pm. Advertising this trial on radio costs AUD$990 for the forty-five 15-second advertisements.
Targeted mail-outs
The research team gained approval from Diabetes Australia, a non-governmental organisation, to access the NDSS database, which is a federally funded register of Australians with diabetes that was initiated in 1987. Briefly, the aim of NDSS is to enhance the capacity of people with diabetes to understand and self-manage their condition, and to provide relevant information, support and access to essential products at subsidised prices. In Victoria, the NDSS register contains the contact detail of more than 85 % of all clinically confirmed cases of diabetes, which includes type 1, type 2 and gestational diabetes [
8]. Since 2001, individuals joining the NDSS have been asked whether they would be willing to be informed of any opportunities to participate in research. Only those who consented to be contacted were eligible to be invited to participate in this study. Because of the extensive nature of the database, the research staff first used the online Australian Diabetes Map (
http://www.diabetesmap.com.au/), which is an interactive national diabetes prevalence map established and regularly updated by NDSS and the Australian Bureau of Statistics (ABS), to identify local government areas and the postcodes within these areas with a reported high prevalence of individuals with type 2 diabetes. Thereafter, the research team contacted NDSS who were responsible for identifying the number of individuals within each of the identified postcodes that had type 2 diabetes, who were aged 50 to 75 years and reported that they were not currently taking insulin to manage their condition. A letter of invitation to participate in the study, that was prepared by the research staff but sent by NDSS, was then forwarded to all individuals that fulfilled the necessary inclusion criteria. Nine mail-outs were conducted and the number of letters sent per mail-out ranged from 80 to 5000 depending upon the number of registrants within a target area. The cost of a direct mail-out was approximately AUD$1.80 per letter. This cost increased or decreased marginally depending on the number of individuals contacted, e.g. the greater the number of letters sent the cheaper the cost. There were no additional costs associated with accessing the NDSS database.
Referrals from GPs and allied health professionals
General practitioners, endocrinologists and other relevant health professionals (e.g. diabetes educators, dietitians and pharmacists) identified from relevant directories (e.g. Yellow Pages), hospitals and profession-specific association websites who were based in a 50-km radius of Melbourne were sent information packs via the mail that provided details about the trial. Included in these packs was a one-page study summary, which outlined the aims, commitment required and the potential benefits to participants, and the key eligibility criteria. They also received trial flyers and posters and were asked to place these on notice boards and/or distribute them directly to relevant patients. Connections with several Medicare Local groups, which are regional organisations who co-ordinate improvements in healthcare for designated populations groups and oversee front-line primary healthcare services, were also made during the establishment of this trial. Specifically, the Diabetes Australia map was used to identify areas with a high prevalence of type 2 diabetes, and the respective Medicare Local groups were subsequently contacted to inform them of the trial and were provided with trial information and advertisements and requested to include these in any communications with GPs and allied health providers.
Flyers and presentations
Flyers and posters were placed in prominent public and relevant locations such as fitness clubs, libraries, senior citizen centres, pharmacies, community houses and retirement villages. In addition, three presentations were made to a range of audiences; one to a diabetes support group where the attendees were a mix of accredited Diabetes Educators, patients and carers, one to GPs at a Medicare Local meeting and another at a local Diabetes Educators annual general meeting.
Website advertisement
Information about the study was posted on the Lift for Life®, Diabetes Victoria, Diabetes Australia, Fitness Australia, Deakin University’s Institute for Physical Activity and Nutrition and the Australian Centre for Behavioural Research in Diabetes websites. These listings were placed on respective websites at the beginning of the recruitment campaign and requested to be removed from the website at the completion of recruitment. There was no cost associated with posting information on these websites.
A pay-per-click advertisement (AUD$0.03 per click at a capped limit of AUD$500) was placed on the social media domain Facebook. This advertisement was 20 words long and used key words to capture potential participant’s attention. The advertisements appeared on an individual’s Facebook page whose age fell into the eligible age range for the trial and a postcode pre-identified to be within a 15-km radius of Deakin University. An individual who clicked on an advertisement was directed to the Lift for Life® website for further information about the trial. The cap of AUD$500 was not reached during the recruitment period but did allow for approximately 16,600 clicks to the advertisement.
Word of mouth
Participants enrolled in the trial were actively encouraged to refer family, friends or colleagues with type 2 diabetes into the study. In addition, participants with type 2 diabetes who enquired but were ineligible for other research studies being conducted within IPAN and who had consented to be contacted for any other research studies, were contacted by research staff via telephone to determine their interest and eligibility in regards to participating in this trial.
Data collection and analysis
The number of expressions of interest (EOIs), participants screened and included in the trial, and how they first heard about the study was recorded by the research staff throughout the screening and recruitment process. Reasons for ineligibility or non-participation in the trial were also recorded. These were categorised into one of five categories: health-related, physical activity status, medication/supplement use, travel or age. Response rates were reported as the number and percentage of participants both interested in and recruited into the trial. Recruitment yield was calculated as the total number of participants recruited divided by the number of EOIs. The success of each recruitment strategy was determined from the number of participants recruited divided by the number of EOIs from each strategy expressed as a percentage. Recruitment rates were also calculated as the average number of participants recruited and randomised per month throughout the recruitment phase. Results were also split by gender. The cost of each recruitment method used was calculated by dividing the total amount spent on a given strategy by: (1) the number of EOIs generated for each strategy, and (2) the total number of eligible participants the strategy was responsible for recruiting (e.g. cost per participant recruited).