Health, Wellbeing and Performance in Law Enforcement Workers

Randomisation Participants will be stratified by shift pattern and by role, and will be randomised to one of three intervention arms using permuted blocks of 3 and 6.

Self-reported information After the consent forms and PAR-Q have been signed, an Operational Police Stress Questionnaire (PSQ-Op), Impact of Events Scale (IES-R), a Leeds Sleep Evaluation (LSE) and an overall health and injury questionnaire (Nordic scale) will be sent to the officers via email using Gorilla software in December 2019.

Participants will be interviewed on the quality of their dietary intake. Trained nutrition research students will collect responses to a Food Frequency Questionnaire (FFQ) in a face to face interview.

Wearables Participants will be given wearable devices to measure their levels of physical activity during an 8-day period (full on and off shift cycle) before the intervention: the heart rate of each participant will be monitored via a Polar heart rate monitor and movement will be measured via an accelerometer worn on the non-dominant wrist (Actigraph, Pensacola, USA). Levels of physical activity, quality of sleep and heart rate variability will be processed as anonymised data on a computer. Participants will be asked to log the quality of their sleep every time they wake up from a long sleep via a Pittsburgh Sleep Quality Index (PSQI). No individuals other than the researchers will have access to the data from the wearable devices. The data will be downloaded from the device and stored in a password-protected file, on an encrypted, password-protected UCL computer in a locked cabinet. After downloading the data to the computer, the wearable device will be formatted.

Oral tests Participant oral health will be assessed on site at the respective stations in January. Oral inflammation has been shown to affect systemic health with cross-sectional evidence suggesting a negative effect on physical activity in Brazilian police. Oral health will be assessed using validated outcome measures routinely employed in both NHS dental practice and research, including: the visual assessment of inflammation of the gum edge and measurement of the depth of the gum pocket (mm) following gentle probing with a calibrated blunt probe; and tooth decay screening assessed through standard clinical methods. Together, these assessments take approximately 15 minutes.

Saliva will be analysed to investigate the effect of the physical activity intervention on the health outcomes. The researchers will collect around 5ml of saliva using standard methods by asking participants to drool into collection pots. The samples will be frozen then analysed for biomarkers related to stress and inflammation. The samples will be collected at the first and last study visits.

Physical and Cognitive tests Participants will then attend a physical screening session at the Institute of Sport, Exercise and Health (ISEH) at UCL. The session will consist of a functional strength test (triple hop, jumps to fatigue on jump mat, successful press-ups one minute, successful inverted rows in one minute). Cardiorespiratory performance will be measured via a Cardio-Pulmonary Exercise Test (CPET) on a treadmill (h/p/cosmos) using the Bruce protocol. During the CPET, Heart Rate will be monitored via a Polar heart rate monitor, and breath-by-breath analysis will be performed with a Vyair gas analyser system to collect VO2 data.

Biomarkers (hsCRP, HbA1c) will be analysed by collecting one blood capillary sample with a finger prick. The capillary is then inserted in an Eppendorf tube and inserted into a Eurolyser Cube (Eurolyser, Salsburg, Austria) to measure markers of inflammation.

Cognitive tests will be performed before and after the CPET. Participants will undergo Source \& Context Memory, inhibition and SOSI tests on an encrypted computer, using the e-Prime software. The cognitive tasks will be standard-format computerised tasks that are used in e.g. studies of drug effects upon cognition, or in experiments looking at the effects of sleep deprivation, or the effects of exercise upon people's abilities to think and remember. Participants are shown pictures and words on a laptop and have to make responses using button boxes of the keyboard. The number of errors and reaction times are recorded. The tests are not stressful and no deception is involved. There are several thousands of publications in the literature that have used these or very similar procedures, and the investigators know of no case where these have caused harm to the participants.

In order to record brain activity during the cognitive tests, functional near-infrared spectroscopy (fNIRS) will be used (Shimadzu LightNIRS). An fNIRS cap placed on the participant's head records brain activity using infra-red light.

Intervention After all screening is complete, participants will be randomly allocated to one of three groups: face to face exercise program (F2F), online exercise program delivered via mobile app (APP) and control (C). The F2F group will receive three exercise training sessions, three times a week for 8 weeks, delivered in person by a strength and conditioning coach at the police station. The exercise intervention will take the format of circuit training using body weight and elastic resistance, focusing on strength endurance and core stability. The APP group will receive online instructions via an app (TeamBuilder) on how to perform the same exercise programme at home. The C group will not receive an intervention.

Behaviour change (to retain levels of physical activity during and after the intervention) will be facilitated by encouraging buddying during the exercise intervention, and by assigning points to the groups based on attendance. There will be two F2F groups and 2 APP groups (Heathrow vs Wood Green). A competitive element will be added between respective F2F and APP groups by assigning 1 point for each participant that attends the session, +2 extra points if all participants attend. Attendance will be kept by the coach for the F2F group. Participants on the APP group will be asked to take a picture of themselves after having completed each session as proof of completion. The coach will monitor compliance for both groups with at attendance spreadsheet.

Post testing After the 8-week training programme is complete, the participants will repeat the same questionnaires, wearables period, fitness tests and cognitive tests that were used in the pre-intervention testing.

Behaviour change will be assessed via a focus group after the intervention. The focus groups will be aimed at gathering feedback on the intervention and on attitudes towards exercise following the COM-B model, including participant experience and whether they felt that the intervention effectively improved their wellbeing.