Type 2 diabetes mellitus (T2DM) is a serious and widespread disease and is recognized as a major public health challenge worldwide. According to the International Diabetes Federation (IDF), the current estimate of adults aged 20-79 years living with diabetes equals 9.3% (463 million) and is projected to increase to 10.9% (700 million) by 2045 [1]. As the prevalence of T2DM increases, effective prevention measures are increasingly important. Focusing on those who are at high risk of developing T2DM is a pivotal starting point.

A state of glucose metabolism is called prediabetes when diabetes mellitus is not yet present but elevated fasting plasma glucose levels or impaired glucose tolerance are known [2]. Hemoglobin A_1c (HbA_1c) levels between 5.7% and 6.4% are indicative of prediabetes. The prevalence of prediabetes in Germany is estimated to be 26% in people aged 45 to 64 years and 31% in people aged 65 to 69 years [3]. Similarly, in the United States, 21.7% of people have prediabetes according to the HbA_1c diagnostic criteria [4]. The clinical relevance of prediabetes is that there is a significantly increased risk of developing T2DM compared to the normoglycemic population, which in turn is associated with an increased risk of developing cardiovascular disease, kidney disease, cancer, depression, and dementia [2]. The results from the population-based Rotterdam Study suggest that up to 74% of 45-year-olds with prediabetes will develop T2DM during their lifetime [5].

The results from the KORA-F4 study (Cooperative Health Research in the Region of Augsburg) and the SHIP-TREND study (Study of Health in Pomerania) suggest that up to one-third of people with prediabetes can be classified as physically inactive [6]. Lifestyle changes, such as physical activity and weight management, are of critical importance in preventing the development and progression of T2DM [2,7].

Although, physical activity interventions have shown beneficial effects on oral glucose tolerance, fasting glucose, and HbA_1c levels in people with prediabetes [8], insufficient physical activity in people with T2DM and prediabetes remains an issue in these populations [9]. There are several barriers associated with participation and long-term adherence to exercise programs among physically inactive people with diabetes, including lack of time, lack of motivation, poorer (self-rated) health, risk of injury, and social and environmental barriers [10]. Therefore, physical activity programs with an attractive profile are needed to reduce sedentary behavior and increase adherence to physical activity. A potential approach to achieve this goal is an innovative training technology called whole-body electromyostimulation (WB-EMS). WB-EMS provides exercise-like effects by inducing muscle contractions using electrical currents from an external source. WB-EMS simultaneously stimulates up to 8-12 major muscle groups with up to 2800 cm² of electrode area. Electrodes are placed on the gluteus muscle, thighs, lower back, upper back, latissimus dorsi, abdomen, chest, and upper arms, and each body region is stimulated with an individualized pulse intensity while individuals perform low-intensity functional exercises in a standing position [11].

In recent years, WB-EMS has found its way not only into therapeutic training but also into rapid and widespread distribution, particularly in Europe, with more than 2000 commercial WB-EMS providers serving approximately 250,000 clients in Germany alone [12]. Due to its increasing popularity, time efficiency, ease of implementation, joint-friendliness, and personalized application, WB-EMS is increasingly the subject of scientific research. In fact, several studies have demonstrated positive effects of WB-EMS on muscle hypertrophy and body composition [13,14]. In addition, high adherence to the intervention and low dropout rates were reported previously [14]. Therefore, this training technology can be considered a promising approach when aiming to increase physical activity in a population of sedentary adults.

A nonrandomized study of WB-EMS showed benefits to HbA_1c levels and fasting glucose in middle-aged and older men with T2DM [15]. In addition, several small studies have shown that local EMS has beneficial effects on glycemic control [16]. In contrast, a recent randomized crossover study by Holzer et al [17] found no significant short-term difference in the acute postprandial glucose response between exercise with and without WB-EMS. However, due to the small sample size (6 patients with T2DM) and short intervention duration (three 20-min sessions), the results of this study cannot be generalized [17]. Some studies further investigated the effect of WB-EMS in a population of individuals with metabolic syndrome. While prediabetes and metabolic syndrome share some common characteristics, people with metabolic syndrome have heterogeneous cardiometabolic profiles, where prediabetes or elevated blood sugar levels might be present, but do not necessarily occur. A study showed that 12 weeks of regular WB-EMS in combination with nutritional counseling had a beneficial effect on body weight and composition, and positively affected blood cholesterol levels, but not HbA_1c levels [18].

A recent randomized controlled study investigated the effect of WB-EMS in comparison to resistance training on cardiometabolic risk factors. The study found that there was no significant effect on variables including HbA_1c [19].

We intend to use WB-EMS focusing on HbA_1c in people with prediabetes and then examine its preliminary efficacy. Therefore, an appropriate design is needed to compare the HbA_1c of the intervention group (IG) with that of the comparison groups.

Our main objective is to pilot the feasibility of a randomized trial testing WB-EMS for HbA_1c levels in people with prediabetes. The primary objective is to provide an estimation of the preliminary efficacy of the intervention on glycemic control in a sedentary group of adults with prediabetes compared with control groups (CGs).

The secondary objectives are to assess the preliminary efficacy of:

The trial is designed as a randomized controlled pilot trial in a parallel design with 3 arms. The trial will be conducted at the Department of Population-Based Medicine at the University Hospital of Tübingen, Germany.

The study population will be selected on the basis of the following inclusion and exclusion criteria (Textbox 1).

Figure 1 illustrates the study procedure. Screening of participants will take place in 2 stages (telephone prescreening and on-site screening). During the telephone pre-screening, the study staff will check key study eligibility criteria and inform participants about the study activities. If they are interested, they will be invited to the on-site screening. During the on-site screening, the study staff will perform the HbA_1c measurement. Furthermore, physical examination (eg, blood pressure) and detailed medical history will be collected to account for any possible contraindications and to ensure safe participation in the training program.

The final determination of eligibility to participate in the trial will take place after the screening. The participants will be randomized to 1 IG and 2 CGs. The duration of the intervention will be 16 weeks. At the end of the intervention period, individuals will return to the study site for a follow-up assessment. The participants of the IG will have a second follow-up assessment after 32 weeks.

The study population will consist of 60 individuals with 20 individuals in each study group. As this is a pilot study, no formal power analysis has been carried out. However, the target sample size was based on recruitment for 15 months at an estimated rate of 4 patients per month (ie, 60 patients), which was considered adequate to obtain reasonably reliable sample size estimates [20-22].

Participants will be recruited through newspaper and social media advertisements. Flyers and posters will also be distributed to local doctors’ offices, pharmacies, hospitals, community centers, and self-help groups.

Eligible participants will be allocated to the study groups by computerized block randomization. This will be performed by an independent trial statistician. Neither the participants nor the researchers will know their allocation in advance. The participants will be strictly separated after randomization. The study staff will prevent participants from different study groups from arriving at the study site at the same time by planning study visits accordingly.

The blinding strategy focuses on study assistants and outcome assessors who will be blinded to the participants’ group status. All data analysts will also be blinded to group allocation.

The main intervention will be WB-EMS using equipment that has EU (European Union) medical device approval (miha bodytec, Type II). This equipment allows the simultaneous stimulation of up to 12 muscle groups (eg, thigh and upper arm, gluteal region, abdomen, chest, lower back, and upper back) with a total stimulation area of approximately 2800 cm². The participants will receive the functional training underwear recommended by the manufacturer (water-absorbent cotton or elastane mix), over which a vest (upper body) and belts (upper arms, thigh, and gluteus muscle) are individually adjusted before each session. The system allows the intensity to be adjusted for each region (Figure 2). We will use an impulse protocol and exercise setting that has been evaluated in recent studies focusing on total and regional muscle mass [13], body fat [23], and physical function [13] in older cohorts. Furthermore, we designed low-intensity exercises to minimize the effect of voluntary movements themselves as low as possible.

A bipolar electric current with a frequency of 85 Hz and an impulse width of 350 microseconds is used in an interval approach with 6 seconds of EMS stimulation with a direct impulse boost and 4 seconds of rest. During the 6-second stimulation period, low-effort movements are performed in a standing position. The intensity of the EMS will be regulated on the basis of the individual’s reported Rating of Perceived Exertion (RPE) and the Borg Category Ratio Scale (Borg-CR10) [14]. We will use RPE to generate and maintain a sufficient but tolerable intensity of EMS application. After 4 weeks of conditioning at a lower pulse intensity, participants will be encouraged to increase the intensity. The impulse intensity will be adjusted individually for each body region in close interaction with the participant. During the session, the instructors will increase the intensity slightly every 3 minutes in close cooperation with the participants in order to maintain the target RPE (6-7) during the session. We will use a personal training setting with one certified and experienced instructor responsible for a maximum of 2 participants. The training will adhere to the requirements of the international EMS guidelines [24].

Table 1 describes the type of data and variables that are collected at various stages of the project. Furthermore, the following demographic and descriptive data are collected at the baseline assessment: gender, age, height (cm), medical history (diseases, surgery, and medicine consumption), physical activity (type, frequency, and duration), educational level, and employment status.

Trainers will monitor adverse events by asking participants if they have experienced any health problems (eg, physical injury and muscle soreness) since the last session. The research team will monitor any adverse events that may occur during participation in this study.

The data will be analyzed using the intention-to-treat principle, which includes all randomized participants. Descriptive statistics, such as mean and SD will be performed for continuous variables, and frequencies and percentages will be used for categorical variables. Diagnostic tests will be conducted for the normality of residuals, linearity, multicollinearity, functional relation, influence, and outliers in the dataset. Assuming data normality, 2-way repeated measures ANOVA and 95% CI will be used to assess outcomes at baseline and 4-month follow-up. The analysis plan will not include reporting of P values, in accordance with the CONSORT (Consolidated Standards of Reporting Trials) 2010 statement: extension to randomized pilot and feasibility trials that “any estimates of effect using participant outcomes as they are likely to be measured in the future definitive randomized controlled trial (RCT) would be reported as estimates with 95% CIs without P values—because pilot trials are not powered for testing hypotheses about effectiveness” [30].

Analysis of covariance will be used to calculate the effect estimate (study outcomes) of the intervention. Effect size calculation for between-group intervention effects and within-group effects will also be performed. All statistical analyses will be performed using SPSS Statistics (version 28, IBM Corp).

This trial protocol version 1 from August 2023 was approved by the local Ethics Committee at the Medical Faculty of the Eberhard Karls University and at the University Hospital of Tübingen (reference: 525/2023BO2) and registered on the ClinicalTrials.gov (ID NCT06188481). Following the approval of the ethics committee on November 6, 2023, preparations for the advertisement and implementation of the project, including the registration of the clinical trial on ClinicalTrials.gov (ID: NCT06188481), were conducted in early January 2024.

All participants will receive a written information letter and informed consent form for participation. All participants will be informed of the voluntary nature of the trial and that they may withdraw from the trial at any time without giving a reason. Only those who confirm their willingness to participate in the trial by signing the informed consent form will be enrolled.

The identities of all participants will be pseudonymized before starting the collection of study data to protect participant identities. The personal data of the participants will be treated confidentially and will only be accessible to the persons directly involved in the study. Further processing, analysis, and publication of the data for scientific purposes will be done anonymously so that no conclusions can be drawn about individual study participants.

Participants in both control groups will be compensated for their time with a coupon for a fitness class at the adult education center (Volkshochschule) valued at €80 (US $91.76). Additionally, all participants will receive feedback about their health parameters. The compensation will be communicated to the participants before enrollment to ensure transparency in the compensation process.