Association between the number of steps performed during work and metabolic syndrome indicators in São Paulo city military police officers: The health promotion of Military Police (HPMP) study

We evaluated the working number steps (STEPS) of 25 military police officers (MPOs: day shift n = 14 and night shift n = 11) from the Military Police of São Paulo State (PMESP) while patrolling São Paulo city center and its association with metabolic syndrome (MetS) indicators. The participants' body composition and anthropometric parameters: body mass index (BMI), fat-free mass (FFM), skeletal muscle mass (SMM) and clinical and laboratory data: systolic (SBP) and diastolic (DBP) blood pressure, and fasting plasma levels of glucose, glycated hemoglobin A1c (HbA1c), insulin, HDL-cholesterol, triacylglycerol (TG), and C-reactive protein (CRP) were also measured. According to the number of steps taken during the daily 12 h working period, the MPOs were divided into three groups: 600-2,000, 2,001-8,000, and >8,000 steps. On average, each participant took 5169 ± 614 steps per 12 h shift. While MPOs from the night shift walked 25% more than the day shift (6188±1069 vs. 4367±664), this difference was not statistically significant. Notably, the BMI, FFM (13.4%), SMM (14.5%), plasma HDL-cholesterol levels (32.2%), and DBP (19.1%) were significantly higher in group 1 compared to the other two groups. Furthermore, reduced physical activity, age, BMI, and tenure at PMESP were associated with increased MetS indicators. Overall, MPOs performing less than 2,000 steps per shift presented marked changes in body composition and plasma measurements and a higher MetS prevalence (64%) than those who were more physically active.

In 2004, the American College of Sports Medicine (ACSM) established five physical activity classification levels depending on the number of steps taken per day: 1) <5,000 steps/day (sedentary); 2) 5,001-7,499 steps/day (little active); 3) 7,500-9,999 steps/day (slightly active); 4) 10,000-12,499 steps/day (active); and 5) ≥12,500 steps/day (highly active). Five years later, Tudor-Loke et al., (2009) introduced two additional graduations to the "sedentary" level: <2,500 steps/day (basal activity) and 2,501-4,999 steps/day (limited activity) (Tudor-Locke, et al., 2009). It has been recommended that adults  years) perform at least 7,000 steps per day (Tudor-Locke, et al., 2011). More recently, the ACSM established that each increment from 2,000 daily steps to 10,000 steps is associated with a 10% reduction in adverse cardiovascular events (Kraus, et al., 2019). In addition, walking 30 min a day, five days a week, reduces the risk of cardiovascular incidents by 19% (Murtagh, et al., 2010). Indeed, there is an inverse relationship between physical activity and chronic diseases, and a 20-30% reduction in premature death in physically active individuals (Paterson & Warburton, 2010;Warburton & Bredin, 2016) In recent years, chronic non-communicable diseases associated with morbidity and mortality have markedly increased, and physical inactivity is one of the critical factors (Lavie, et al., 2019;Myers, et al., 2019). Despite the widespread acceptance of physical exercise's beneficial effects (Penedo & Dahn, 2005), a third of the world's population is considered sedentary (JI, 2019). Merino (2010) investigated cardiovascular and metabolic changes and the leading causes of death in the Military Police of São Paulo State (PMESP) compared to the São Paulo city civilian population between 2002 and 2006. This author reported that military police officers (MPOs) aged between 20 and 54 had mortality rates that were 2.5 and 4 times higher due to CVD and liver disease, respectively, compared to the civil population in the same age range. Additionally, Merino found that during the first ten years of service (i.e., 20-29 years of age), MPOs have a lower CVD-related mortality rate than the civilian population with the same age range. On the other hand, in the last ten years of service, deaths due to CVD were 3.5 and 2.9 times higher for MPOs between 45-49 and 50-54 years old, respectively, compared to the civilian São Paulo city population (Merino, 2010).
The present study investigated the number of steps performed during a 12 h day or night shift patrolling São Paulo city center and MetS indicators. We also evaluated the association of age, PMESP service time, and BMI with MetS indicators in the same volunteers.

Recruitment of the participants
The present study was carried out at the Institute of Sport Sciences and Physical Activity (ICAFE) at Cruzeiro do Sul University (UNICSUL) in São Paulo, SP, Brazil, as previously described by Souza et al. (2021). The MPOs from Metropolitan Police Command Area 1 work in the radio patrol program in the São Paulo city center and participated in a previous study (Souza et al., 2021). Initially, 51 MPOs were recruited to monitor physical activity levels using a pedometer (YamaxDigi-Walker SW 700, Tokyo, Japan) during their patrols. The volunteers were separated according to day (n=29) or night (n=22) shift. In the São Paulo city radio patrol, officers work 12 h shifts [i.e., 6:00 am to 6:00 pm (day shift), or 6:00 pm to 6:0 0 am (night shift)] followed by 36 h of rest. Twenty-one volunteers did not correctly fill out the daily registration form (DRF) and were excluded. Thus, 25 participants completed the study (n=14 for the day shift and n=11 for the night shift). The Ethics Committee at Cruzeiro do Sul University (Protocol number 08905019.4.0000.8084) approved the study.

Experimental procedure
Questionnaire application, blood collection, and plasma measurements were performed at the ICAFE at UNICSUL.
All participants were instructed to fast for at least 8 h before all assessments. (Table 1) The height, measured using a stadiometer, and body mass (BM) of each volunteer were used to calculate the body mass index (BMI). Skeletal muscle mass (SMM; Kg), fat-free mass (FFM; Kg), absolute fat mass (AFM; Kg), and visceral adipose tissue (VAT; L) were determined using eight-point bioelectrical impedance analysis, with a SECA 515 medical Body Composition Analyzer (mBCA) (Hamburg, Germany), according to a previous study (Bosy-Westphal, et al., 2013). Hip circumference (HC; cm)and waist circumference (WC; cm) was measured following the method of Onis et al., (1996). The waist-to-hip ratio (WHR) was calculated using WC and HC data. The same protocol was used in our previous study (de Souza, et al., 2018). (Table 1) The average age (years) of the 25 volunteers was 33.5±1.36. The age (years) of MPOs working the day shift ranged from 27 to 44 (35.5±1.57). The age of MPOs working the night shift ranged from 24 to 47 (30.7 ± 2.17). Participant percentage distribution by age was 21.4% and 54.5% (≤30), 50% and 36.4% (31 to 40), and 28.6% and 9.1% (≥41) for the day and night shifts, respectively. PMESP service time ranged from 3 to 23 years (10.4 ± 2.15) for the MPOs working the day shift and from percentage distribution was 50% and 82% (≤5 years), 28.5% and 18% (10-20), and 21.5% and 0% (≥21) for the day and night shift groups, respectively. It should be pointed out that newcomer MPOs predominate the night shift. The individual and average values ± standard error of the means (SEM) are presented in Table 1  According to the WHO WHR classification (1998), six volunteers working the day shift were at moderate risk for developing CVD, three were at high risk, and six were at very high risk. Of the MPOs working the night shift, one was at low risk of developing CVD, six were at high risk, and four were at very high risk. When considering all 25 participants, 28% were at moderate risk for developing CVD, 32% were at high risk, and 40% were at very high risk.

Physical activity during the working period
Physical activity (i.e., number of steps) was monitored during the day and night patrol shifts. Briefly, participants were initially instructed to use the pedometer and complete the daily record form (DRF), indicating when the device was placed on and removed from the body. The MPOs used a pedometer for three 12 h working periods. The first period was dedicated to training the MPOs on using the pedometer. Each device was set up considering each police officers' body mass and step length (Schneider, et al., 2003). At the end of the patrol shift, the volunteers registered the number of steps performed in the DRF. Every day volunteers were reminded by text message via the WhatsApp application about using the device and recording data in the DRF at the beginning and end of the workday. The average number of steps was calculated using the data from two patrol shifts.

Working length at PMESP
The participants were also divided by the time they worked at the PMESP. Of the 25 participants, sixteen worked at 7 the PMESP for 1 to 10 years, six worked for 11 to 19 years, and three for >19 years.

Clinical and laboratory data
Participants fasted for eight hours before blood samples were collected for determining plasma glucose, insulin, TG, HDL-cholesterol, CRP, and HbA1c concentrations. The estimated insulin resistance index (HOMA) was determined using the blood glucose and insulin levels (Matthews, et al., 1985). Resting blood pressure was measured with a Premium brand analog sphygmomanometer, following the procedures recommended by the 7th Brazilian Guideline of Arterial Hypertension (Malachias, et al., 2016). The Diagnosis and Analysis Center (CDA, São Paulo, SP, Brazil) conducted the laboratory measurements. Our group used the exact measurements in a previous study (Souza et al., 2021).

Calculations performed using the results of the measurements mentioned above
The number of steps each study participant took during the day or night shifts was evaluated according to service time, age, BMI and the clinical and laboratory measurements.

Statistical analysis
The data were analyzed using the PRISM software, version 9.0 (Graph Pad, San Diego USA). The level of significance adopted was 95% (p<0.05). The Kolmogorov-Smirnov test was used for normal data distribution analysis. The Student's t-test (data with normal distribution) was used to compare two groups in the quantitative variables or the Mann-Whitney test (data without normality). One-way ANOVA with Tukey post-test was used to compare groups according to PMESP service time. For non-parametric data, the Kruskal-Wallis test was utilized. The Pearson's correlation test (data with normal distribution) or Spearman's test (data without normality) was used to check the relationship among measurements. The data are presented as percentages, and delta (Δ) values were calculated using the Excel program.

Results
The individual and average±SEM number of steps during the patrol shift, SBP and DBP (mmHg), fasting plasma levels of glucose (mg/dL), high glycated hemoglobin HbA1c (%), TG (mg/dL), HDL (mg/dL), and CRP (mg/dL), and HOMA are presented in Table 2. The average number of steps for all volunteers (n=25) was 5169±614 during each 12 h shift. On average, the MPOs working the day shift took 4368±664 steps, and those working the night shift took 6189 ± 1069 steps.
While the MPOs patrolling at night performed 29.4% more steps than those of the day shift, this result failed to reach a level of statistical significance. Research, Society and Development, v. 11, n. 2, e13511225376, 2022 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v11i2.25376 Plasma TG levels of all participants were 149±21.3 mg/dL, slightly below the normal value of <150 mg/dL (SPOSITO, et al., 2007). A total of eight MPOs (32% of the total sample), five from the day and three from the night shift, presented elevated values. The average plasma HDL value of all participants was 43.6±2.37 mg/dL. While the average plasma HDL value was >40 mg/dL, which is considered normal for adults (Xavier, et al., 2013), five of the day and four of the night shift MPOs had low values (i.e., 36% of the total). Finally, the plasma CRP levels of all participants ranged from 0.07 to 0.46, values within the normal range (<0.60 mg/dL) (Roberts et al., 2001).
Based on the collected data and analyses, it was determined that nine day (64.2%) and seven night (63.6%) shift MPOs exhibited MetS, which corresponds to 64% of the total sample.

Discussion
In the present study, we evaluated the number of steps taken by MPOs during their 12 h patrols. Twelve hours comprise most of the day, considering the hours of sleep and the commute to work. The study of Tudor-Locke (2011)  There was no statistical difference in BMI between group 1 (600-2,000 steps) and group 2 (2,001-8,000 steps). We also did not detect significant differences in FFM and SMM between these two groups. Krumm et al., (2006) examined the relationship between daily steps measured using a pedometer and body composition parameters in 93 menopausal women and reported a linear relationship between steps performed and BMI. Moreover, women who took 5,000 to 7,500 steps per day had lower BMI values than those who took less than 5,000 steps per day. Interestingly, there was no significant difference in BMI between women who took 7,500-9,999 steps per day and those who performed more than 10,000. Our data indicate that other factors, probably specific to radio patrol policing rather than physical activity, are involved in our findings.
We found higher BMI values in the group with >19 years of service than those with 1-10 years; however, the values were not significant (p<0.08). Additionally, BM (tendency, p <0.07) and AFM (p<0.01) were increased in the >19 years of service compared to the group with 1-10 years. These findings suggest that the MPOs who worked at the PMESP for a longer period display abnormal body composition, possibly contributing to the onset and progression of MetS.
Although we did not detect a statistical difference in the VAT, MPOs who performed a greater working number of steps (WNS) exhibited improved health parameters. On the other hand, the VAT increases with age and service length at the PMESP. The metabolic benefits that physical activity promotes are well known, and the consequences of low physical activity are associated with high VAT. Thus, the reduced number of steps taken by all MPOs probably contributed to the elevated VAT values. Notably, this condition is associated with peripheral insulin resistance and MetS prevalence (Lee & Kim, 2013), and frequent and intense physical activity significantly reduces VAT (Ismail, et al., 2012;Vissers, et al., 2013).
It is known that hypertriglyceridemia is a risk factor for acute myocardial infarction and stroke (Bays et al., 2013) and that there is a close association between hypertriglyceridemia and a sedentary lifestyle (Edwardson, et al., 2012). In the present study, eight (36%) of the 25 volunteers presented hypertriglyceridemia; however, we could not detect a relationship between the number of steps and high plasma TG levels. Thus, it is plausible that other factors, such as age, family history, gender, smoking, drinking, arterial hypertension, abdominal overweight, obesity, a diet rich in animal fats, and stress, contribute to this observation (Faludi, et al., 2017). The group with the longest service time in the PMESP had TG values above normal, suggesting that this factor contributed to the observed hypertriglyceridemia.
It has been reported that plasma HDL-cholesterol levels below 40 mg/dL are associated with physical inactivity and programs with a controlled diet to generate a daily caloric deficit of 500-600 calories for 24 weeks. One group had a long and continuous walking protocol, with at least 100 steps per min for 50 min, six times a week and the other group walked twice a day for 25 min, six times a week. Under these conditions, the physical activity volumes were equalized. Before starting the protocol, the first group performed 3,925±701 steps per day, while the second group took 3,990±651. After 24 weeks, both groups significantly increased the number of steps, with the first group exhibiting an increase of +2196 ± 789 steps per day and the second group increased the number of daily steps by +2965±795. While both groups presented increased plasma HDL levels and reduced BM, BMI, WC, and total cholesterol, HbA1c, glucose, and insulin blood levels, the second group displayed more expressive results that could contribute to cardiometabolic disease prevention. Vancini et al., (2018) described the relationship between symptoms of anxiety and depression and the level of habitual physical activity in male MPOs from the State of Espirito Santo, Brazil (who routinely deal with extraordinarily complex and hostile situations), according to the BMI. They observed that the overweight group had increased anxiety and depression associated with low physical activity levels. Additionally, the MPOs with the highest BMI had the most marked symptoms.
These changes may be related to the number of military service years.
There are some limitations to take into consideration in analyzing our results. For example, we only studied male MPOs. A paired control group would be desirable, but it is difficult to define appropriate professional work for comparison.
Moreover, we did not record the physical activity for 24 h. Lastly, despite providing proper teaching and support for the participants' to use and handle the pedometers and recording the number of steps during their patrol shift, the number of participants excluded from the study due to improper pedometer use was high.

Final Considerations
In conclusion, the occurrence of MetS increases in MPOs with more years of service at the PMESP. The number of daily steps taken by MPOs during their patrol indicates that the majority are not physically active. Additionally, these individuals presented unhealthy body compositions and plasma measurements associated with a high MetS prevalence (64%).
Notably, all MPOs working at the PMESP for more than 19 years performed the fewest number of steps during work (up to 2,000 steps) and presented MetS. Intervention strategies are needed to increase physical activity practice during work and to prevent and treat the occurrence of metabolic changes in MPOs.