Introduction
Police officers have greater mortality rates and risk for obesity and cardiovascular disease when compared with the general public (15). The occupation of a police officer is primarily sedentary, with occasional periods of maximal exertion such as restraining suspects and running in pursuit (4,20,21). Low levels of physical activity have been shown to promote increases in weight, body fat, and potential health issues (8). Weight gain can also account for declines in an officer's physical performance (4,20) and is associated with decreases in cardiopulmonary fitness (19). Therefore, the continued increase in weight gain and cardiovascular disease risk, combined with the difficulty in treating these conditions, suggests that innovative strategies in police officers for disease prevention need to be developed and evaluated (7,11,12,17,25).
Reports by many health organizations have recommended aerobic exercise (e.g., brisk walking) and strength training as an integral part of adult fitness programs (7,11,12,17,25). However, many officers have reported that exhaustion and lack of time are often barriers to adopting an exercising program (3,4,20,21). Therefore, developing exercise strategies that are more likely to be adopted by police officers would be important to reduce weight gain and cardiovascular risk in a group at high risk of weight gain and disease risk.
Despite the need for research involving police officers, there have been no long-term (e.g., 6 months) exercise intervention studies using job-specific exercises that include both men and women on changes in body composition and cardiovascular fitness in police officers. Therefore, the primary objective of this investigation was to evaluate the impact of a supervised, 6-month job-specific minimal exercise program (aerobic and strength training) and 12-month follow-up (18 months) in sedentary young police officers on body composition and cardiovascular fitness. We hypothesized that the minimal exercise program would result in a decrease in body weight (BW) and improvement in cardiovascular fitness at 6- and 12-month follow-up (18 months) compared with baseline.
Methods
Experimental Approach to the Problem
One-hundred sixty-five commissioned employees of the St. Louis Metropolitan Police Department were randomly selected to participate in the study. Aerobic exercise (brisk walking) progressed from 3 d·wk−1, 20 minutes per session at 60% of the heart rate reserve (HRR) (10) to 5 d·wk−1, 30 minutes per session at 75% of the HRR at 3 months, and this level was maintained until 6 months. After the completion of the aerobic exercise, 8 calisthenics exercises were performed to increase muscular strength related to job duties of a police officer. The muscular strength training progressed from 3 d·wk−1, 2 sets of 5 repetitions using the subject's own BW to 5 d·wk−1, 3 sets of 15 repetitions using the subject's own BW at 3 months, and this level was maintained until 6 months. After 6 months of the supervised exercise program, the participants were encouraged but not required to continue to perform the exercise program for an additional 12 months. At baseline, 6 months and 18 months, BW (intraclass correlation coefficient [ICC] = 0.98) and cardiovascular-muscular fitness were measured using a 0.25-mile obstacle course (Figure 1) based on the Human Resources Subcommittee of the Major City Chiefs Conference recommendation for police officers (2,16) incorporating various job-specific exercises. The obstacle course time was expressed as the physical abilities test (PAT) time (ICC = 0.96). All testing sessions were conducted at the same time of the day.
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Figure 1: Physical activity test. The participants completed the course at baseline, 6 months, and 18 months. The physical abilities test (PAT) required that officers complete the obstacle course in <4 minutes and 8 seconds by running the perimeter of the Police Academy Gymnasium 2 times (∼0.25 miles) and then negotiate the following obstacles in the following order: 1) jump over a 1-ft. hurdle, 2) jump over a 2-ft. hurdle, 3) negotiate around 2 cones, 4) jump a 4-ft. long jump, 5) negotiate around a cone, 6) walk down a 6-in.-wide beam 8 ft. long, 7) negotiate around 2 cones, 8) approach a mat, drop down, touch chest to floor, stand up, 9) drop down on back, touch shoulder blades to floor, stand up, 10) negotiate around a cone, 11) jump or climb over a 4-ft. wall, 12) negotiate around a cone, 13) go up 6 stairs then down 6 stairs, 14) repeat the stairs, 15) advance to power training machine, push 75 lb, walk in a semicircle, 16) pull 75 lb, walk in a semicircle, 17) drag 150-lb dummy 50 ft., 18) sprint 50 yd, and 19) dry fire a weapon 5 times with each hand.
Subjects
One-hundred sixty-five (n = 131 male, n = 34 female) young (26.4 ± 1.9 years), sedentary (no participation in regular aerobic or resistance training and <500 kcal·wk−1 in recreational physical activity assessed by the Minnesota Leisure Time Physical activity questionnaire [23]) commissioned employees of the St. Louis Metropolitan Police Department were randomly selected to complete 3 PATs within an 18-month period. The race of the population was 64% Caucasian, 30% African American, 4% Hispanic, and 2% other. Baseline data for the 165 participants who completed the study are shown in Table 1. Those who were considered eligible based on a phone interview were invited to attend an information session where the study requirements were explained and questions answered. The participants were included in the study if they met the following criteria: (a) were between the ages of 21–35 years, (b) passed the Department Physical Examination before acceptance into the St. Louis Metropolitan Police Academy, (c) completed a health history questionnaire (1), (d) completed a physical activities readiness questionnaire (24), and (e) received a physician's release. The participants were excluded if their duty status was limited duty and were hypertensive (>140/90 mm Hg) (6). All the subjects signed informed consent documents, and written approval was given by the Southern Illinois University Edwardsville Institutional Review Board and the St. Louis Police Department before the beginning of the study.
Table 1: Participant characteristics.*
Procedures
Supervised Exercise Protocol
All exercises were performed in the police department's fitness center. The exercise consisted primarily of walking on motor driven treadmills; however, alternate activities of stationary biking and swimming were allowed for 20% of the total exercise sessions (1 out of 5 days). The exercise progressed from 3 d·wk−1, 20 minutes per session at 60% of the HRR (11) to 5 d·wk−1, 30 minutes per session at 75% of HRR at 3 months, and this level was maintained until 6 months. The 150-min·wk−1 exercise was chosen as it meets the American College of Sports Medicine's (ACSM) exercise guidelines of accumulating at least 150 min·wk−1 of moderate intensity exercise (11), and this is in agreement with the recommendations for exercise programs designed for weight management and the recent position statement regarding appropriate strategies for weight loss and prevention of weight regain for adults (8). The resting heart rate value used for calculating HRR was obtained at the radial artery for 15 seconds after the participant rested in a supine position for 5 minutes. The 15-second value was then multiplied by 4 to obtain the heart rate per minute. Because exercise intensity may not be ascertained by observation, target heart rates were verified during each exercise session by use of a Polar Heart Rate Monitor (Accurex Plus). Detailed records regarding attendance, duration, and heart rate were maintained by the training supervisor.
To improve muscular strength and endurance specific to police officers, the participants performed 8 calisthenics exercises (push-ups, pull-ups, dips, sit ups, lunges, standing side leg lifts, squats, and back extensions) during each session after the completion of the aerobic exercise (2,16). The calisthenics were performed after the aerobic exercise to mimic the specific job duties for police officers because it is common for police officers to first run down perpetrators (aerobic) before securing them into custody using a particular submission hold (muscular strength) (2,16). The calisthenics progressed from 3 d·wk−1, 2 sets of 5 repetition using the subject's own BW to 5 d·wk−1, 3 sets of 15 repetitions of the subject's own BW (2,16) at 3 months, and this level was maintained until 6 months. The order of exercises (as listed previously) was the same for all training sessions. The participants would perform one set of each callisthenic exercise and then repeat the sequence until all the prescribed sets were completed. The participants rested 30 seconds between each callisthenic exercise. Each exercise session was preceded by a 5-minute light stretching period of the upper and lower body (26). To ensure compliance with the resistance training protocol, all the sessions were supervised on a one-on-one basis by experienced exercise physiologists. The completed training session was followed by a 5-minute cool-down and light stretching period. Detailed records regarding attendance and number of sets and repetitions performed were maintained by the training supervisor. If participants missed an exercise session, they were rescheduled to make up the missed session in the same week.
Follow-Up
After 6 months of the supervised exercise, the program participants were encouraged but not required to continue to perform the exercise program on their own. The participants were informed of the mandatory fitness testing that would occur at 12-month post–supervised exercise program (i.e., 18 months from baseline). At the 12-month follow-up, the participants were asked to record the number of minutes per week they engaged in aerobic and strength training exercise over the past 12 months using the Leisure Time Physical Activity Questionnaire (18).
Cardiovascular and Muscular Fitness Testing
The participants were required to complete the PATs before and after the 6-month supervised exercised program and 12 months follow-up (i.e., 18 months, Figure 1). The PAT is an original test based on the recommendation from the Human Resources Subcommittee of the Major City Chiefs Conference's and the Physical Fitness Testing in Law Enforcement (2,16). The PAT was developed to test an officer on job-specific qualifications. All the components of the PAT were designed to mimic what an officer may encounter and what would be expected of him or her to complete in the field.
The PAT required that the officers complete the obstacle course in <4 minutes 8 seconds by running the perimeter of the Police Academy Gymnasium 2 times (∼0.25 mile) and then negotiate the following obstacles in the following order (Figure 1): (1) Jump over a 1-ft. Hurdle; (2) jump >2-ft. hurdle; (3) negotiate around 2 cones; (4) jump a 4-ft.-long jump; (5) negotiate around a cone; (6) walk down a 6-in.-wide beam 8 ft. long; (7) negotiate around 2 cones; (8) approach a mat, drop down, touch chest to floor, stand up; (9) drop down on back, touch shoulder blades to floor, stand up; (10) negotiate around a cone; (11) jump or climb over a 4-ft. wall; (12) negotiate around a cone; (13) go up 6 stairs then down 6 stairs; (14) repeat the stairs; (15) advance to power training machine, push 75 lb, walk in a semicircle; (16) pull 75 lb, walk in a semicircle; (17) drag 150-lb dummy 50 ft.; (18) sprint 50 yd; and (19) dry fire a weapon 5 times with each hand. The participants were required to refrain from eating at least 2 hours before the test but were instructed to drink plenty of fluids (except caffeinated beverages) for the 24 hours before the test. If the participants did not pass after the initial attempt they were given 2 other attempts on 2 consecutive days to pass the PAT. The reason for not passing the PAT on the first attempt (n = 10) was because of illness. All the participants completed the PAT within the 3 allowable attempts.
Body Weight
Body weight was assessed at baseline, 6 and 18 months between 7:00 and 9:00 AM using a digital scale accurate to ±0.1 kg (Befour Inc., Model #PS6600, Saukville, WI, USA). The participants were weighed before breakfast and after attempting to void and wore a standard hospital gown at the time of weighing.
Height
Height was recorded at the beginning of each session using a Seca telescopic measuring rod (Seca, Hanover, MD, USA).
Body Mass Index
Body mass index (BMI) was calculated by using the calculation of height to weight: BMI (kilograms per meter squared) = (weight in pounds × 703)/height in inches2.
Physical Abilities Test Time
The PAT time was recorded by both video tape and Robic SC-505 Multi-Mode Chronograph 5-Lap Memory Stopwatch.
Statistical Analyses
A 1-factor repeated measures (time) analysis of variance (ANOVA) was used for main effects. If there was a significant interaction effect of group or time, we employed the Tukey post hoc test. All values are expressed as mean ± SEM. A sample size of 165 provided near 100% statistical power for measures of cardiovascular and muscular fitness (CMF) (using PAT time) and BW with an alpha level of 0.05. The intraclass correlation coefficients for PAT time (r = 0.96) and BW (r = 0.98) were excellent. Data were analyzed using SAS (9.2, Cary, NC, USA). Statistical significance was defined at p < 0.05 for all the tests.
Results
Adherence to Fitness Program
During the 6-month, supervised fitness program, both men and women participants completed >98% of the prescribed exercise. The reason for missing an exercise session was because of minor injury or illness. However, at 12-month follow-up, 51% of the participants (53% men and 50% women) reported engaging in the 150 min·wk−1 as recommended by the ACSM (11).
Body Weight
There was a significant reduction (p < 0.01) in BW from baseline to 6 months in both men (−1.8 ± 0.3 kg, p < 0.01) and women (−1.9 ± 0.3 kg, p < 0.05) with no between-sex differences (Figure 2). However, there was a significant increase in BW from 6 to 18 months in both men (4.0 ± 1.7 kg, p < 0.01) and women (4.1 ± 1.8 kg, p < 0.05) resulting in a significant difference from baseline to 18 months for both men and women (p < 0.01).
Figure 2: Change in body weight, body mass index, and physical abilities test time. Values are mean ± SEM. Value significantly different from baseline value: *p < 0.05, **p < 0.01. BW = body weight; BMI = body mass index; PAT = Physical Abilities Test.
Body Mass Index
There was a significant reduction in the BMI from baseline to 6 months in both men (−0.6 ± 0.1 kg·m−2, p < 0.01) and women (−0.8 ± 0.1 kg·m−2, p < 0.05) with no between-sex differences (Figure 2). However, there was a significant increase in the BMI from 6 to 18 months in both men (1.4 ± 0.2 kg·m−2, p < 0.01) and women (1.5 ± 0.3 kg·m−2, p < 0.05) resulting in a significant difference from baseline to 18 months for both men and women (p < 0.01).
Cardiovascular and Muscular Fitness
There was significant reduction in time to completion for PAT from baseline to 6 months in both men (−23 ± 4 seconds, p < 0.01) and women (−21 ± 3 seconds, p < 0.01) with no between-sex differences (Figure 2). However, there was a significant increase in the time to completion for PAT from 6 to 18 months in both men (21 ± 4 seconds, p < 0.01) and women (19 ± 3 seconds, p < 0.01) resulting in a significance difference from baseline to 18 months for both men and women (p < 0.01).
Discussion
To our knowledge, this is the first long-term study in police officers that indicates that a supervised, employee-based exercise program is effective at improving body composition and cardiovascular and muscular fitness in police officers. Additionally, there was no difference between men or women at 6 months, indicating that the exercise program is effective for both sexes. However, from 6 to 18 months, BW, BMI, and PAT time increased, indicating a decrease in the overall fitness. Therefore, to ensure that police officers are prepared to perform their on the job duties, it is recommended that police departments provide a regular supervised, employee-based exercise program year round.
The fact that the minimal employee-based exercise program following the ACSM recommendation for fitness (8,11) reduced BW and improved fitness in police officers is important for overall reductions in disease risk (15). In this study, the participants lost approximately 4% of their BW during the 6-month program, which may have beneficial improvements in chronic disease risk factors. Although blood lipids and blood pressure were not measured in this study, other studies using police officers have shown that modest weight loss (as little as 2–3%) has resulted in reduction of cardiovascular disease risk (9,14). To this end, a basic fitness program following the ACSM exercise guidelines lasting only 30 min·d−2 may be associated with increased employee health (22).
There are several possible reasons for the health improvements from baseline to 6 months that could be used by police stations to increase adherence to an exercise program. During the 6-month, supervised exercise program, individuals were given basic health information, a structured physical training sessions, free use of the department fitness center, accessible advice from on-staff exercise physiologists on proper form, weight, exercise progression, and any other fitness-related information needed. In several other studies involving police officers, it was found that structured physical training sessions and on-site staff increase adherence (3,4,20,21). However, because there was a significant reduction in cardiovascular and muscular fitness and an increase in BW and BMI from months 6–18, it suggests that the participants did not adhere to the program and that a regular supervised program may be necessary. In fact, only 51% of officers reported meeting the ACSM recommendation for physical activity (11). For those individuals who did not meet the ACSM recommendation, it is possible that after the 6-month supervised program, participants may have lacked motivation, time, and incentive to continue the training necessary to continue with the fitness program. Lack of time and motivation are often barriers to exercise that would need to be addressed by police agencies to increase adherence (10). For example, during the 6-month, supervised exercise program, police officers had paid, on-duty exercise time, which increased the likelihood that officers could find the time to exercise (5). Although paid, on-duty work-out time may not be feasible for all police agencies offering on-site facilities and may increase the likelihood of engaging in an exercise program (10).
It is important to note that at 18 months, 51% of the participants reported exercising at least 150 min·wk−1 which is above the national average of 42% (8,11). Although there were no significant differences in the BW and cardiovascular fitness between those who met the exercise standard at 18 months compared with those who did not, the participants who met the exercise guidelines regained less weight and did not lose as much of their cardiovascular fitness gains compared with those who did not (data not shown). These findings do suggest that exercising at least 150 min·wk−1 of exercise may slow BW regain and reductions in cardiovascular fitness. Although we were not able to assess the reasons as to why some officers engaged in regular physical activity whereas others did not, it is possible that certain demands of a police officer (e.g., apprehending suspects) requires officers to engage in some form of physical activity to perform their job. In other words, officers that are routinely in the field may be more inclined to engage in regular physical activity to perform their duties, whereas those who are not may lack the necessary motivation (3,4,20,21). Therefore, a challenge for police agencies will be to adopt methods (e.g., monthly education meetings or on-site facilities) to increase the likelihood that all officers, regardless of rank or job duties, will maintain their BW and cardiovascular fitness (5,10).
Differences in how men and women may respond an exercise program are often cited as a barrier to adopting any employee-based exercise fitness (3) for fear of gender inequality. However, in this study, both men and women improved their PAT times by approximately 15%. A possible reason for the similar improvement by both sexes was that the exercise program (walking and muscular strength) was designed to prepare the police officers for on the job duties, regardless of sex. These results are in contrast to other studies that showed that men improve more than women in their PAT times (3). However, a major difference between this study and others (3,4,20) is that unlike other studies where exercise programs are different between sexes, the current exercise program, following the ACSM guidelines (8,11), was the same between sexes. In other words, the job requirements (i.e., apprehending suspects) of the police officer are the same; therefore, the exercise program in this study was designed to be the same as well. It is important to note that the adherence (98%) was the same between men and women; therefore, the exercise program was well tolerated regardless of sex.
There were some limitations to the study. We were unable to perform any additional body composition measures (waist circumferences) because of restrictions by the police agency. However, the BMI is strongly linked to disease risk (4,16,20) in police officers. We also chose to use the PAT time instead of a walk or run test to measure cardiovascular and muscular fitness. Although a walk or run test is a good estimator of cardiovascular fitness used by many investigators for the general population, the unique demands of a police officer requires a fitness and strength test that mimics the job duties of an officer that are different from the general population. Therefore, the use of the PAT provided more relevance for police agencies in order for them to assess the effectiveness of the exercise program used in this study. Despite these limitations, this study provided important information regarding an exercise program for police officers. For example, unlike many studies using self-report, which has been shown to overestimate exercise performed by up to 45% (13), this study verified and supervised all exercise sessions ensuring that the subjects actually performed the prescribed exercise.
In conclusion, this is the first study examining the effects of a supervised exercise program on BW, BMI, and cardiovascular and muscular fitness in police officers. It appears that a supervised exercise program following the ACSM exercise guidelines (8,11) provides police officers with the necessary instruction to achieve improved health. However, further supervision such as monthly education may be necessary to increase the likelihood that officers will maintain the necessary fitness levels. To this end, a regularly supervised, employee exercise program for police officers may be effective in improving fitness but that supervision of the exercise program may be required for continued improvement or at the very minimum maintenance of health benefits.
Practical Applications
The practical application of this study is that a supervised job-specific exercise program for police officers improves fitness and body composition after 6 months, but continued supervision of exercise program is necessary for maintenance of health benefits. Therefore, it is suggested that to increase adherence to the exercise program, police departments provide daily, on-site facilities and staff that can design specific exercise programs for the officers. Additionally, the program should include job-specific exercises (calisthenics: push-ups, pull-ups, lunges, etc.) that focuses on the entire body and brisk walking or running of moderate intensity. For police stations that do not have the financial means to provide on-site training facilities or staff a monthly health education session would be advised.
Acknowledgments
The authors would like to thank the participants who volunteered their time and effort for this study. Additionally, we thank the staff of Southern Illinois University Edwardsville for their time and expertise. This project was supported by an internal Southern Illinois University Edwardsville Grant. The authors have no professional relationships with companies or manufacturers who will benefit from the results of this study. The results of this study do not constitute endorsement of the product by the authors or the National Strength and Conditioning Association.
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