Light Intensity Physical Activity Trial

Total duration of the RCT is 12 months, with the first 6 month as the intervention period and the last 6 months as follow-up.

Community-dwelling individuals with type 2 diabetes are eligible for participation in the trial, taking into account the in- and exclusion criteria described below, 160 participants will be included, 80 in each study arm. Study measurements of all participants will take place at baseline (month 1 (t = 0)), month 3 (t = 3), month 6 (t = 6, and month 12 (t = 12) at the Maastricht UMC+.

Participants in the intervention group will be instructed to increase their LiPA by decreasing sedentary time. Participants will follow 4 workshops in group sessions on strategies to change their physical activity behaviour and will receive a feedback physical activity monitor that will be worn continuously on the wrist and provide e-feedback on activity behaviour.

Participants in the control group will receive 4 workshops in group sessions on healthy lifestyle including information and strategies to increase LiPA and reduce sedentary time similar to the intervention group, but will not receive a feedback-activity monitor.

Screening A preliminary screening will be carried out by telephone interview. If eligibility criteria are met the participant will attend the baseline visit which starts with the informed consent procedure. Afterwards, a standard physical examination will take place and an ultrasound scan will be performed to screen for large atherosclerotic plaques of the carotid arteries. If the participant is indeed eligible for inclusion, the investigational baseline measurements are performed after which randomization will take place. From then on participants will run through the protocol either being part of the intervention or control group.

Measurements at the four investigational visits (t = 0, 3, 6 and 12)

• sociodemographic data
• medical history \& medication use: by means of an interview
• lifestyle factors (alcohol use and smoking behaviour), quality of life, depressive symptoms - by means of questionnaires
• Sedentary and physical activity monitoring: by means of the activPAL® activity monitor for 7 days
• venous sampling (approx. 40 ml per person per visit; 8 collecting tubes of 5 ml) for fasting glucose, fasting insulin, HbA1c, lipid profile, creatinin, albumin and biomarkers of endothelial dysfunction (vWF, s-VCAM-1, sE-selectin, sTM, SICAM-1), low-grade inflammation(CRP, SAA, IL-6, TNF-alfa, IL-8) and immune cells. The remainder of the material will be stored in a biobank for future determination of any potentially interesting (bio)markers on the topic of physical activity. For any such future procedures further approval will be sought from the METC/MUMC+.
• Anthropometric data (height, weight, waist and hip circumference and bio-electrical impedance measurements)
• vascular measurement (arterial stiffness, microvascular function and blood pressure)
• physical function measurements (grip strength and timed chair test)
• Objective measurement of light-intensity physical activity through activPAL ® activity monitor that will be worn for 7 days continuously at baseline, month 3, month 6, and month 12. This device is blinded to the participant. Data from the activPAL provide detailed and accurate information on the participants' sedentary, standing, and stepping time for each day.

Sample size calculation In order to be able to detect a 10% difference in PWV and similarly a 10% difference in carotid distensibility (the primary objectives of the study) after the intervention between the intervention group and the control group, both groups should consist of at least 73 participants each if assuming a probability of a type 1 error at 0.05 (i.e., alfa) and an 80% (i.e., beta) ability to detect a true difference between the intervention group and the control group. These estimates are conservative taking into account only PWV values at entry and exit of the trial. The 10% difference is speculative and based upon a mean PWV estimates from 'The Maastricht Study' data as there is currently no data available on LiPA and arterial stiffness. In order to correct for potential drop out (roughly estimated at 10%) 80 participants will be included in each group.

Statistical analysis The significance levels used in the statistical analyses will be 0.05. The validity of the normality assumption will be check for all outcomes. Baseline characteristics will be compared between the intervention and the control group. For continuous variables (e.g. age, BMI) mean and standard deviations will be presented; numbers and percentages will be shown for categorical variables (e.g. smoking, medication use). T-tests will be used to compare differences in continuous baseline characteristics between the intervention and control group and chi-square test will be used for categorical variables. Assuming that the randomization was successful no differences are expected. Missing data will be imputed using multiple imputations techniques.

Primary study parameter(s) The effect of the intervention on the primary outcome PWV at month 6 will be analysed using intention-to-treat (ITT) approach according to randomization assignment. The ITT analyses will be used as primary method for our statistical analyses and any outcomes in our reports will be primarily based upon these ITT analyses. In addition, a per protocol analysis will be performed for those who attended the workshops. These analyses will be used to gain some insights into any potential non-response / drop out. These per protocol analyses will not be the primary source for reporting outcomes. General linear models will be used to analyse the effect of the intervention on PWV at month 6. Due to the COVID-19 crisis some month 6 measurement will take place at a later moment, depending on the duration of this delay we will have to adjust for this in our statistiscal anlayes. In addition, repeated measures will be taken into account, baseline, month 3, and month 6 using mixed models in SPSS. The 3-month visits might be missing for some particiapants due to COVID-19 crisis, we assume that the 6-month measurements for these particiaptns can take place as planned In these models, subject is entered as a random effect and intervention (categorical variable with 2 levels: 1: intervention; 2: control group) as a fixed effect .The baseline value of PVW and sex will be used as covariates in analyses.

Secondary study parameter(s) Sedentary time, as measured by the activPAL will be analysed as total sedentary minutes on an average day as well as the percentage of sedentary during wake time. Similarly, time standing and stepping, also derived from the activPAL data will be analysed. All metabolic health parameters and microcirculation measurements will also be analysed as continuous variables. Quality of life and mental functioning are also analysed as continuous variables. Finally, measures of body composition measures are also all continuous outcomes variables

Similar to the primary outcome analyses, general linear mixed models will be used the analyses the change the secondary outcome measures from baseline to month 6. Using mixed models, the repeated measures will be taken into account similar the analyses with the primary outcome.

All analyses, for the both primary and secondary outcomes will also be conducted for the follow-up (month 12 data) to examine the long-term effect of the intervention, taking into account all repeated measures (baseline, month 3, month 6) in a mixed model.