The Impact of Treadmills and Cooler Environments for Office Workplaces on Ergonomics, Heating Energy Requirements, Performance, as Well as Back and Cardiometabolic Health

This is a controlled intervention study with a crossover design. Participants are assigned to different conditions in which they perform both sedentary and walking desk activities at different room temperatures.

Intervention conditions:

I: Sedentary activity at standard room temperature (23°C) II: Walking activity at standard room temperature (23°C) III: Sedentary activity at lowered room temperature (19°C) IV: Walking activity at lowered room temperature (19°C)

Each condition is carried out over a defined period, with corresponding 24-hour washout periods between conditions to minimize carry-over effects.

Participants are expected to attend a total of five in-person appointments at the indoor climate laboratory of the Chair of Building Services Engineering at RWTH Aachen University. On Day 0, an introduction to the local conditions will take place before the actual study week begins, and the continuous glucose monitor is individually placed on the upper arm. In the following study week, four consecutive experimental study days are planned. Participants will go through two different scenarios: Six participants will first experience a warm exposure for two days, followed by a cold exposure for two days, while the other six will start with a cold exposure and end with the warm exposure. Allocation of participants to the two sequences of the four experimental conditions (Sequence 1: I-II-III-IV; Sequence 2: III-IV-I-II) is performed using stratified block randomization. A computer-generated randomization procedure is used to ensure that participants are evenly distributed between both sequences. Randomization is carried out before the first test session. To ensure a balanced gender distribution, ideally three men and three women will start with Sequence 1, and three men and three women with Sequence 2.

Participants meet at 8:30 a.m. at the indoor climate laboratory of the Chair of Building Services Engineering and begin preparations, during which the required sensors for data collection are attached. The clothing level of participants will be approximately 0.8 clo for all conditions (DIN EN ISO 9920, 2009-10: Ergonomics of the thermal environment - Estimation of the thermal insulation and evaporative resistance of a clothing ensemble). In practice, this results in the following clothing requirement, which will be communicated to participants on Day 0: underwear, socks, shoes, long trousers, T-shirt/undershirt, and a long-sleeved shirt.

Each of the four laboratory office days follows in principle the same time course. From 08:30AM onwards, a chest-worn heart rate monitor belt is started to be worn. At 9:00AM, a breakfast meal (standardized liquid meal) will be taken under controlled conditions. This is followed at 10:00AM by the first activity phase: participants in the walking conditions walk for one hour on the treadmill, while those in the sedentary conditions perform seated work and remain seated throughout. From 10 to 11:00AM, participants will perform an attention task on a computer. At 11:00AM, a recovery phase begins, during which participants complete a standardized questionnaires for subjective ratings. At 12:30, lunch is served (e.g., bread, fruit, and cereal bars). Starting at 1:00PM, four consecutive short activity periods take place every hour: for 15 minutes each, participants in the walking conditions walk on the treadmill, while those in the sedentary conditions continue to sit, interspersed with 45 min sitting for all conditions. At 4:15PM after the last walking activity, a final survey is conducted, during which a concluding questionnaire is completed to evaluate the overall experience and any changes in well-being. At regular intervals over each laboratory office day, participants will be asked to rate their thermal comfort on digital scales and blood pressure will be measured preceding and following walking periods. Each laboratory day officially ends at 4:30PM with the removal of sensors and the participants' departure. Only the continuous glucose monitor will only be removed on the fourth and last test day.

Inclusion criteria

• Physically active, healthy test subjects
• Participants who are able to understand the research project
• Adult test volunteers (aged >18 and <40)
• German language skills at B2-C2 level

Exclusion criteria

• An implanted pacemaker
• Participants who are unable to give consent/participants with a legal representative
• Age under 18 or over 40
• Pregnant participants
• Participants with a BMI >28
• Participants with underlying diseases with significant functional limitations (e.g., rheumatoid arthritis, diabetes mellitus, high blood pressure)
• Reading and/or spelling disorders or combined disorders of scholastic skills (ICD-10 F81.0 - F81.3)
• Participants with a possible SARS-CoV-2 infection will be excluded from the study for the duration of the infection