Nelson Moreira Diniz Neto*

nnelsondiniz@hotmail.com

Kédson Yuri Lima de Sousa**

kedson2246@gmail.com

Morganna Alves Siqueira+

morgganaalves@gmail.com

Luiz Fernando Gouvêa-e-Silva++

lfgouvea@yahoo.com.br

*Graduado em Educação Física (Licenciatura)

pela Universidade do Estado do Pará, Santarém, Pará

Especialista em Preparação Física de Alto Desempenho

pela Faculdade Iguaçu

Especialista em Docência em Segurança Pública

pela Faculdade Iguaçu

Especialista em Docência do Ensino Superior

e Educação Física pela Faculdade Iguaçu

3° Sargento da Polícia Militar do Pará, lotado

no 2° Batalhão de Missões Especiais, Santarém, Pará

**Graduado em Educação Física (Licenciatura)

pela Universidade do Estado do Pará, Santarém, Pará

Graduado em Educação Física (Bacharelado)

pelo Centro Universitário Claretiano, Santarém, Pará

+Graduada em Fisioterapia

pela Universidade Federal de Jataí, Jataí, Goiás

Mestra em Ciências Aplicadas à Saúde

pela Universidade Federal de Jataí, Jataí, Goiás

Doutoranda em Educação Física

pela Universidade Federal do Triângulo Mineiro, Uberaba, Minas Gerais

Membra do Grupo de Estudo e Pesquisa Morfofuncional

na Saúde e Doença – GEPEMSAD

Vice-coordenadora do Laboratório Morfofuncional

na Saúde e Doença – LAMSAD

++Graduado em Educação Física

pela Universidade Federal de Uberlândia, Uberlândia, Minas Gerais

Mestre em Genérica e Bioquímica

pela Universidade Federal de Uberlândia, Uberlândia, Minas Gerais

Doutor em Doenças Tropicais pela Universidade Federal do Pará

Líder do Grupo de Estudo e Pesquisa Morfofuncional

na Saúde e Doença – GEPEMSAD

Coordenador do Laboratório Morfofuncional

na Saúde e Doença – LAMSAD

Professor da Universidade Federal de Jataí, Jataí, Goiás

(Brasil)

Reception: 03/17/2026 - Acceptance: 07/08/2026

1st Review: 03/23/2026 - 2nd Review: 05/22/2026

Accessible document. Law N° 26.653. WCAG 2.0

Suggested reference: Neto, N.M.D, Sousa, K.Y.L. de, Siqueira, M.A. e Gouvêa-e-Silva, L.F. (2026). Impact of 12 weeks of resistance training on body composition, pain, and physical capacities. Study of military police officers in the Amazon interior. Lecturas: Educación Física y Deportes, 31(339), 119-141. https://doi.org/10.46642/efd.v31i339.8813

 

Abstract

    Introduction: Military police officers (MPOs) often exhibit a sedentary lifestyle, characterized by unfavorable changes in body composition, reduced physical capacities, and increased pain perception. In contrast, resistance training (RT) has been shown to be an effective strategy for promoting health in this population. Objective: To analyze the effects of a resistance training program on body composition, physical capacities, pain occurrence, and pain intensity among military police officers working in administrative services in the municipality of Santarém, Pará, Brazil. Methods: This quasi-experimental study included 19 military police officers engaged in administrative duties in Santarém, Pará, Brazil, who participated in a 12-week RT program. Body composition, muscular strength, abdominal muscular endurance, flexibility, and pain were assessed before and after the intervention. Data were analyzed using both descriptive and inferential statistics, with a significance level set at p<0.05. Results: Female participants predominated (53 %), and the mean age was 34.89±7.02 years. RT reduced body adiposity (p<0.05) and significantly improved muscular strength (p<0.001), flexibility (p<0.001), and localized muscular endurance, as demonstrated by a higher number of repetitions in the abdominal endurance test (p<0.001). Regarding pain, a reduction in the occurrence of painful body regions (89.5 % vs. 57.9 %) and a decrease in self-reported pain intensity were observed (p<0.001). Conclusion: These findings reinforce the importance of RT as an effective strategy for promoting health, improving functional performance, and reducing pain complaints among military police officers.

    Keywords: Resistance training. Police. Body composition. Pain.

 

Resumo

    Introdução: Policiais militares (PM) apresentam um estilo de vida sedentário, marcado por alterações na composição corporal, nas capacidades físicas e na percepção da dor. Por outro lado, o treinamento resistido (TR) atua de forma eficaz para a promoção de saúde nessa população. Objetivo: Analisar o efeito de um programa de TR na composição corporal, nas capacidades físicas, na ocorrência e intensidade de dor de PM atuantes no serviço administrativo do município de Santarém-Pará. Métodos: Estudo quase-experimental, com 19 policiais militares atuantes do serviço administrativo, em Santarém, Pará, Brasil, submetidos a 12 semanas de TR. Foram avaliadas, pré e pós-intervenção a composição corporal, força muscular, resistência muscular abdominal, flexibilidade e a dor. Os dados foram analisados por estatística descritiva e inferencial, adotando-se p<0,05. Resultados: O sexo feminino predominou (53 %) e a idade média foi de 34,89±7,02 anos. O TR reduziu a adiposidade corporal (p<0,05), aumentou a força muscular (p<0,001), a flexibilidade (p<0,001) e a resistência muscular localizada, evidenciada pelo maior número de repetições no teste de abdominal (p<0,001). Em relação à dor, verificou-se redução na ocorrência de regiões dolorosas (89,5 % vs. 57,9 %) e diminuição da intensidade da dor relatada pelos participantes (p<0,001). Conclusão: Os achados reforçam a importância do TR como estratégia eficiente na promoção de saúde, desempenho funcional e redução de queixas dolorosas em PM.

    Unitermos: Treinamento resistido. Polícia. Composição corporal. Dor.

 

Resumen

    Introducción: Los policías militares (PM) presentan un estilo de vida sedentario, caracterizado por alteraciones en la composición corporal, las capacidades físicas y la percepción del dolor. Por otro lado, el entrenamiento de resistencia (ER) actúa eficazmente para promover la salud en esta población. Objetivo: Analizar el efecto de un programa de ER sobre la composición corporal, las capacidades físicas, la aparición e intensidad del dolor en policías militares que trabajan en el servicio administrativo del municipio de Santarém-Pará. Métodos: Estudio cuasiexperimental con 19 policías militares que trabajan en el servicio administrativo de Santarém, Pará, Brasil, sometidos a 12 semanas de ER. Se evaluaron la composición corporal, la fuerza muscular, la resistencia de la musculatura abdominal, la flexibilidad y el dolor antes y después de la intervención. Los datos se analizaron mediante estadística descriptiva e inferencial, adoptando p<0,05. Resultados: Predominaron las mujeres (53 %) y la edad media fue de 34,89±7,02 años. El entrenamiento de resistencia (ER) redujo la adiposidad corporal (p<0,05), aumentó la fuerza muscular (p<0,001), la flexibilidad (p<0,001) y la resistencia muscular localizada, evidenciada por un mayor número de repeticiones en la prueba abdominal (p<0,001). En cuanto al dolor, se observó una reducción en la frecuencia de las zonas dolorosas (89,5 % frente a 57,9 %) y una disminución en la intensidad del dolor reportado por los participantes (p<0,001). Conclusión: Los hallazgos refuerzan la importancia del ER como una estrategia eficaz para promover la salud, el rendimiento funcional y reducir las molestias dolorosas en los agentes de policía.

    Palabras clave: Entrenamiento de resistencia. Policía. Composición corporal. Dolor.

 

Lecturas: Educación Física y Deportes, Vol. 31, Núm. 339, Ago. (2026)

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Introduction 

 

    Physical inactivity is recognized as one of the main modifiable risk factors for the development of chronic noncommunicable diseases and is associated with adverse outcomes such as reduced quality of life and increased mortality (Alonzo et al., 2022; Ballin et al., 2021; Sheng et al., 2021; Stens et al., 2023). Despite recommendations for regular physical activity, a substantial proportion of the adult population remains insufficiently active, a condition associated with the worsening of clinical and functional outcomes over time. (Booth, Roberts, & Laye, 2012)

 

    In the occupational context, military police officers (MPOs) constitute a group particularly vulnerable to sedentary behaviors and their deleterious effects due to the specific characteristics of their profession, including irregular work schedules, occupational stress, and intermittent physical demands (Bernardo et al., 2016; Oliveira et al., 2015). Previous studies have reported a high prevalence of physical inactivity among this population, as well as its association with poorer physical performance and an increased risk of adverse health outcomes. (Moreira, & Frómeta, 2021)

 

    Among MPOs, those assigned to administrative duties are exposed to prolonged sedentary behavior, primarily characterized by excessive time spent sitting. This occupational pattern has been associated with an increased occurrence of musculoskeletal pain, particularly in the spine, as well as impairments in physical fitness. (Azeredo et al., 2021)

 

    In this context, resistance training (RT) has been widely recommended as an effective strategy for improving body composition, increasing muscular strength, and enhancing functionality and quality of life across different populations (Sharma et al., 2023). However, despite the well-documented benefits of RT in the general population, studies investigating its effects among MPOs remain scarce, particularly among those who predominantly perform administrative duties and exhibit high levels of sedentary behavior.

 

    Furthermore, few studies have simultaneously explored outcomes related to pain, body composition, and physical capacities in this specific population (Hoflinger et al., 2021; Oliveira et al., 2023). Therefore, the present study aimed to analyze the effects of an RT program on body composition, physical capacities, pain occurrence, and pain intensity among MPOs working in administrative services in the municipality of Santarém, Pará, Brazil.

 

Methods 

 

Study design and participants 

 

    This was a quasi-experimental, non-randomized study without a control group, conducted with MPOs assigned to administrative duties at the headquarters of the Regional Policing Command I and the 3rd Military Police Battalion in the municipality of Santarém, Pará, Brazil. Assessments were carried out at the facilities of the State University of Pará and at the gymnasium located within the 3rd Military Police Battalion headquarters, where the RT program was also implemented.

 

    Sample size was calculated using G*Power® software (version 3.1.9.7; Institute of Experimental Psychology, Düsseldorf, Germany). Type I and Type II error rates were set at α = 0.05 and β = 0.10, respectively, to achieve a statistical power of 90 % and detect an effect size of at least 0.80, resulting in a minimum required sample of 19 participants. However, due to the use of a non-probabilistic convenience sampling strategy, 32 MPOs assigned to administrative duties were initially recruited.

 

    MPOs of any rank, aged between 25 and 50 years, of both sexes, who were actively performing their professional duties, had not engaged in RT for at least three months, and worked 6 to 8 hours per day were eligible for inclusion. Participants were excluded if they reported any medical restrictions, injuries, or health conditions that could prevent them from completing the assessments or the proposed RT program. Officers who were on vacation, special leave, or traveling during the intervention period were also excluded, as were those who failed to achieve the minimum attendance rate of 75 % established for the study. As a result, 11 participants were excluded due to low attendance and two due to work-related injuries, resulting in a final sample of 19 MPOs and an attrition rate of 40.6 % (n = 13).

 

    The study was approved by the Human Research Ethics Committee of the State University of Pará, Campus XII – Santarém (CAAE: 65155817.3.0000.5168). All participants were informed about the study procedures and objectives and provided written informed consent prior to participation.

 

Procedures and data collection 

 

    Anamnesis and all assessments were performed before and after the RT program. The anamnesis questionnaire was administered to obtain sociodemographic and clinical information, including sex, age, medication use, presence of injuries or health conditions, workplace assignment, work schedule, physical activity practice, and planned leave or vacation periods.

 

    It should be noted that, with the exception of muscular strength assessment, all evaluations were conducted before the start of the RT program. Baseline muscular strength assessment was performed during the 13th training session, following a four-week familiarization period with the exercises. The four-week familiarization period was adopted to promote neuromuscular adaptation and technical learning of the exercises, particularly considering the participants’ low previous training experience. This approach aimed to minimize the risk of injury and increase the reliability of strength measurements. (Grgic et al., 2020)

 

    Height was measured using a portable stadiometer (Sanny®, Brazil), and body weight was assessed using a Welmy® analog scale. Body mass index (BMI) was calculated by dividing body weight (kg) by height squared (m²). BMI classifications were defined as underweight (<18.5 kg/m²), normal weight (18.5–24.9 kg/m²), overweight (25.0–29.9 kg/m²), and obesity (≥30.0 kg/m²), according to World Health Organization criteria. (WHO, 2000)

 

    Abdominal circumference was measured using an anthropometric tape measure (Sanny®, Brazil) positioned at the level of the umbilical scar. Skinfold thickness was assessed using a scientific skinfold caliper (Cescorf®, Brazil) with a precision of 0.1 mm. Biceps, triceps, subscapular, suprailiac, abdominal, thigh, and calf skinfolds were measured. Three measurements were obtained at each site, and the mean value was used for analysis. The sum of all skinfold measurements was adopted as the variable of interest. All measurement procedures and assessment guidelines followed the recommendations described by Fernandes Filho (2003).

 

    Body composition was assessed using tetrapolar bioelectrical impedance analysis with a Maltron® device (model BF 900). Participants were evaluated in the supine position. Initially, they were instructed to remove all metallic objects and remain at rest. Adhesive electrodes were then placed on the right hand and right foot according to the manufacturer’s recommendations, with two electrodes positioned on the hand and two on the foot. After connecting the cables to the device, body composition parameters were recorded, including body fat percentage, lean mass, and fat mass.

 

    Prior to the assessment, participants were instructed to avoid physical exercise for 12 hours, refrain from consuming alcoholic and caffeinated beverages for 24 hours, maintain a 2–3-hour interval after their last meal, void their bladder within 30 minutes before the test, and avoid excessive fluid intake immediately before the assessment. In addition, participants were advised on the importance of maintaining adequate hydration status. Female participants were instructed to undergo the assessment preferably outside periods of greater fluid retention during the menstrual cycle. (Kyle et al., 2004)

 

    Maximal strength (1RM) was assessed using three exercises: the bench press, hack machine, and lat pull down. The testing protocol consisted of a predicted one-repetition maximum (1RM) based on 2 to 10 repetition maximums, as proposed by Brzycki (1993). Participants were instructed to perform the exercises through a full range of motion and with proper technique within the target range of 2 to 10 repetitions. The test was terminated when the participant reached concentric failure, demonstrated improper exercise technique, or exceeded the prescribed repetition range. Maximal strength was then estimated using the following equation:

 

Predicted 1RM = lifted weight ÷ [1.0278 − (0.0278 × number of repetitions)] 

 

    Flexibility was assessed using the sit-and-reach test performed with a Wells bench. Participants completed three trials, and the greatest distance reached was considered for analysis (Pollock, & Wilmore, 1993). Localized muscular endurance was assessed using a one-minute abdominal curl-up test. The outcome measure was the maximum number of correctly performed repetitions completed within one minute. (Pollock, & Wilmore, 1993)

 

    Pain occurrence and intensity were assessed using the Corlett Diagram, developed and validated by Corlett, & Bishop (1976). The instrument is used to evaluate the presence, location, and intensity of pain according to body region. The diagram consists of a schematic representation of the human body divided into 28 regions associated with pain presence and intensity. Pain intensity is rated on a scale from 1 to 5, where 1 indicates no pain and 5 indicates intolerable pain/discomfort.

 

Resistance training protocol 

 

    The RT program lasted 12 weeks (36 sessions), with a frequency of three sessions per week and an approximate duration of 60 minutes per session. Each session consisted of a 5–10-minute warm-up on aerobic exercise equipment (stationary bicycle or treadmill), followed by RT and concluding with 3–5 minutes of stretching exercises targeting the muscle groups recruited during training.

 

    The first four weeks (sessions 1–12) were dedicated to familiarizing participants with the proposed exercises (Table 1). During sessions 1–4, participants performed one exercise per muscle group, completing two sets of 15 repetitions for each exercise (Table 2).

 

Muscle group	Exercises
Chest	Bench press, incline bench press, flat fly, incline fly, flat dumbbell fly, incline dumbbell fly, cable crossover, pec deck
Back	Lat pull down, close-grip lat pull down, seated row, bent-over row, one-arm dumbbell row
Deltoids	Lateral raise, front raise, reverse pec deck, reverse fly, cable reverse fly
Biceps	Preacher curl, barbell curl, simultaneous dumbbell curl, unilateral dumbbell curl, cable curl
Triceps	Triceps pushdown, lying triceps extension, French press, triceps kickback
Quadriceps	Leg press, hack machine, leg extension, smith machine squat
Hamstrings / gluteals	Leg curl, standing leg curl, smith machine lunge, stiff-leg deadlift, leg press, hack machine
Calves	Standing calf raise on leg press, seated calf raise
Abdominals and erector spinae	Back extension, cable side bend, abdominal crunch, side bend

Source: Authors

 

    Table 2 shows that from the 5th to the 12th session, training was divided into upper- and lower-body muscle groups. Accordingly, two exercises were performed for large muscle groups and one exercise for small muscle groups, with three sets of 12 maximum repetitions, completing the first mesocycle.

 

    In the 13th session, corresponding to the first day of the second mesocycle, the 1RM test was performed. From the 14th session onward, training included three exercises for large muscle groups and two exercises for small muscle groups. From the 14th to the 36th session, training was organized into alternating muscle-group splits as follows: Training A – chest, quadriceps, and abdominals; Training B – back, hamstrings, calves, and back extension; Training C – triceps, biceps, shoulders, and side flexion (Table 1; Table 2).

 

    During the second and third mesocycles, participants performed three sets of 3 to 15 maximum repetitions, according to the prescribed intensity, which varied across weeks: 70 % (week 1; 3 sessions), 80 % (week 2; 3 sessions), 90 % (week 3; 3 sessions), and 60 % (week 4; 3 sessions) of 1RM. Thus, a non-linear periodization model was adopted (Table 2). It is noteworthy that after the end of the 12th week (36th session), the 1RM test was reassessed.

 

Training variables	1st Mesocycle		2nd e 3rd Mesocycles
	Familiarization (sessions 1-4)	Sessions 5-12	1RM test (session 13)	Sessions 14-36
Sets x repetitions	2 x 15	3 x 12	1 x 2-10	3 x 3-15
Intensity	Light / subjective	70 % 1RM	Submaximal / maximal	60 %-90 % 1RM
Rest interval between sets / exercises	1 min / 2 min	1 min / 2 min	5 min / 5 min	1 min / 2 min
Exercises	One exercise per muscle group	2 exercises for chest, back, quadriceps, and hamstrings/ gluteals Other muscle groups: 1 exercise	Bench press Hack machine Lat pull down	Training A: Chest Quadriceps Abdominals Training B: Back Hamstrings/ gluteals Calves Erector spinae Training C: Triceps Biceps Shoulders Abdominals/ erector spinae

Legend: 1RM: one-repetition maximum. Source: Authors

 

Statistical analysis 

 

    Data were tabulated and analyzed using descriptive statistics, including mean, standard deviation, median, interquartile range, percentage change (delta), and absolute and relative frequencies. For inferential analysis, the Shapiro–Wilk test was first applied to assess data normality. BMI, fat mass, wide-grip lat pull down, bench press, pain occurrence, and pain intensity did not present a normal distribution.

Accordingly, paired t-tests were used for normally distributed variables, while the Wilcoxon signed-rank test was applied to non-normally distributed variables. McNemar’s test was used for the binary categorical variable “presence of pain” before and after the intervention.

Additionally, effect size was calculated using Cohen’s d, with 95 % confidence intervals (95 % CI), to estimate the magnitude of differences (0.2 = small; 0.5 = medium; 0.8 = large) (Cohen, 1988). To control for type I error due to multiple comparisons, the Bonferroni correction was applied. Statistical analyses were performed using BioEstat software (version 5.3), with a significance level set at p<0.05. Figure 1 was generated using GraphPad Prism (version 3.0).

 

Results 

 

    The sample consisted of 19 participants, 53 % (n=10) of whom were female, with a mean age of 34.89±7.02 years (range: 26–46 years). Table 3 presents the comparison of body composition variables before and after the intervention. Significant reductions were observed in abdominal circumference (p=0.002), body fat percentage (p=0.021), fat mass (p=0.038), and the sum of skinfolds (p=0.002). No significant differences were found in total body mass (p=0.138), body mass index (p=0.184), or lean mass (p=0.202). It is noteworthy that after Bonferroni correction, only abdominal circumference and the sum of skinfolds remained statistically significant (Table 3).

 

Variables	Resistance Training Program		p	d (CI95 %)
	Pre (mean±sd)	Post (mean±sd)
Body mass (kg)	73.19±13.18	72.45±13.11	0.138	-0.36 (-0.82 to 0.10)
Body mass index (kg/m2)*	25.8(24.1-29.0)	25.1(23.6-28.5)	0.184	-0.34 (-0.80 to 0.12)
Abdominal circumference (cm)	90.19±10.34	87.93±10.31	0.002†	-0.79 (-1.28 to -0.28)
Body fat percentage (%)	30.40±6.03	29.00±6.70	0.021	-0.58 (-1.05 to -0.09)
Lean mass (kg)	50.52±7.59	51.03±8.07	0.202	0.30 (-0.16 to 0.76)
Fat mass (kg)*	19.8(16.2-27.2)	19.8(15.8-24.3)	0.038	-0.53 (-0.99 to -0.05)
Sum of skinfolds (mm)	161.58±47.55	149.22±42.36	0.002†	-0.81 (-1.30 to -0.30)

Legend: sd – standard deviation; 95 %CI - 95 % confidence interval; *data presented as median (interquartile range); † significant after Bonferroni correction (adjusted p = 0.003); d – Cohen’s effect size (0.2 = small; 0.5 = moderate; 0.8 = large). Source: Study data

 

    Table 4 presents the distribution of pain presence and location. Pain prevalence decreased from 89.5 % (n=17) to 57.9 % (n=11), corresponding to a percentage change of −35.3 %. The total number of reported pain sites decreased from 101 to 33. The most frequent regions at baseline were pelvis (9.9 %), left knee (7.9 %), and mid-back (6.9 %). After the intervention, the most frequent regions were mid-back (12.2 %), left knee (12.2 %), and pelvis (9.1 %).

 

Variables	Pre		Post		Δ %
	n	%	n	%
Presence of pain
Yes	17	89.5	11	57.9	-35.3*
No	2	10.5	8	42.1	300.0
Pain location
Neck	5	5.0	3	9.1	-40.0
Cervical Spine	6	5.9	2	6.1	-66.7
Upper back	6	5.9	2	6.1	-66.7
Mid-back	7	6.9	4	12.0	-42.9
Lower back	6	5.9	3	9.1	-50.0
Pelvis	10	9.9	3	9.1	-70.0
Left shoulder	5	5.0	2	6.1	-60.0
Right shoulder	5	5.0	1	3.0	-80.0
Left knee	8	7.9	4	12.0	-50.0
Right knee	6	5.9	1	3.0	-83.3
Left leg	5	5.0	2	6.1	-60.0
Right leg	6	5.9	2	6.1	-66.7
Other	26	25.8	4	12.2	-84.6
Total	101	100	33	100	-67.3

Legend: n – absolute frequency; % - relative frequency; Δ % - percentage change (difference in absolute frequency from pre- to post-intervention); * McNemar test, p = 0,031; for comparison of pain presence between pre- and post-resistance training program. Source: Study data.

 

    Figure 1 presents comparisons of motor variables and pain. Increases were observed in flexibility (37.4 %), number of repetitions in the abdominal test (35.4 %), load in the hack machine (21.8 %), bench press (8.3 %), and lat pull down (8.4 %). Additionally, reductions were observed in pain occurrence (75 %) and pain intensity (23.1 %).

 

Note: A–C – values expressed as mean ± standard deviation. D–G – values expressed as median (interquartile

range – 25 %–75 %; lower and upper whiskers represent minimum and maximum values). Source: Study data

 

    Regarding the findings presented in Figure 1, effect sizes and their respective 95 % confidence intervals were as follows: flexibility (d=1.56; 95 % CI: 0.91 to 2.17), abdominal test (d=2.08; 95 % CI: 1.28 to 2.83), hack machine (d=1.62; 95 % CI: 0.96 to 2.23), bench press (d=1.18; 95 % CI: 0.57 to 1.75), lat pull down (d=1.25; 95 % CI: 0.63 to 1.82), pain occurrence (d= −1.18; 95 % CI: −1.75 to −0.57), and pain intensity (d= −0.97; 95 % CI: −1.52 to −0.42). It is noteworthy that all effect sizes were greater than 0.80 in absolute value and were classified as large according to Cohen’s criteria (Cohen, 1988).

 

Discussion 

 

    The present study aimed to analyze the effects of a RT program on body composition, physical capacities, and pain occurrence and intensity in military police officers working in the administrative sector of the municipality of Santarém, Pará, Brazil. The main findings indicated improvements in physical capacities, reductions in body fatness, and decreases in both pain occurrence and intensity.

 

    Among the observed outcomes, pain reduction showed the greatest clinical relevance, followed by gains in flexibility and abdominal muscular endurance, all with large effect sizes. Body composition variables that showed significant improvements presented small-to-large effect magnitudes.

 

    Regarding adiposity-related variables, a significant reduction in abdominal circumference (moderate effect size) and in the sum of skinfolds (large effect size) was observed, even in the absence of nutritional monitoring. These findings are particularly relevant considering that military police officers often present an unfavorable anthropometric profile, with a high prevalence of overweight and obesity associated with cardiometabolic risk factors. (Damasceno et al., 2016; Esteves et al., 2014)

 

    Abdominal obesity is associated with increased cardiovascular and inflammatory risk (Shangguan et al., 2025), absenteeism, work leave (Sato et al., 2025; Van Duijvenbode et al., 2009), and impairment of the physical fitness required for police duties (Barbosa et al., 2022). Thus, the observed improvements extend beyond aesthetic outcomes, representing meaningful clinical and occupational benefits (Lima-Dos-Santos et al., 2020), since increased habitual physical activity is associated with reductions in excess body weight, particularly in the abdominal region. (Ross et al., 2000)

 

    These results are consistent with previous evidence indicating that RT is associated with reductions in body fat (Cabral et al., 2013; Dias et al., 2015; Rocha et al., 2015). These changes may be explained by increased energy expenditure and improved insulin sensitivity induced by RT (Małkowska, 2024). However, it is noteworthy that body fat percentage and fat mass did not remain statistically significant after Bonferroni correction for multiple comparisons, indicating that these findings should be interpreted with caution.

 

    Although no increase in lean mass was observed, its maintenance alongside fat reduction represents a favorable adaptation. In contrast, strength gains were substantial, particularly in the hack machine and lat pull down exercises, both showing large effect sizes. These findings are consistent with the literature (Cassemiro et al., 2017; Fleck & Simão, 2008) and likely reflect neural adaptations, such as increased motor unit recruitment (Häkkinen, & Hakkinen, 1995) and reduced antagonist coactivation. (Häkkinen et al., 1998)

 

    In the present study, the RT program reached loads up to 90 % of 1RM in the final weeks, which may have contributed to the observed strength gains, as training at intensities closer to 1RM tends to produce greater strength adaptations. (Callou Filho et al., 2024)

 

    A significant improvement was also observed in the abdominal test, with a large effect size, indicating increased muscular endurance. This adaptation suggests improved trunk stability and the ability to sustain submaximal efforts for longer periods (Alecu, Onea, & Badau, 2025), which, from an occupational perspective, may enhance tolerance to job-related physical demands such as load carriage and repetitive lifting tasks. (Vaara et al., 2022)

 

    Regarding flexibility, which also showed a large effect size, although the program was not specifically designed to improve this capacity, resistance training exercises may promote adaptations in musculotendinous extensibility. (D'Onofrio et al., 2023)

 

    Considering that police officers often present inadequate flexibility levels (Marins, & Del Vecchio, 2017), RT may promote simultaneous improvements in flexibility and strength, particularly in hip extensors and the lumbar region, contributing to better musculoskeletal function. (D'Onofrio et al., 2023; Rosenfeldt et al., 2024)

 

    Pain reduction represents the most clinically relevant finding of this study. The high baseline prevalence corroborates previous studies reporting a high frequency of musculoskeletal complaints among police officers, especially in the spine (Anderson, Zutz, & Plecas, 2011; Azeredo et al., 2021; Tavares Neto et al., 2013) and knees (Azeredo et al., 2021), which are particularly vulnerable due to occupational demands. (Nygaard et al., 2022)

 

    Lopes et al. (2023) reported the presence of pain complaints in at least one body region, with a predominance in the spinal region among university students. These findings reinforce that musculoskeletal pain is not restricted to occupational demands specific to policing but is also associated with hypokinetic routines, highlighting the impact of physical inactivity and prolonged sedentary behavior on musculoskeletal health.

 

    The observed reductions in pain occurrence (large effect size) and intensity (large effect size) may be explained by neurophysiological mechanisms (endogenous opioid release) (Wang et al., 2022), vascular mechanisms (increased capillarization and clearance of algogenic substances) (Walling et al., 2000), and biomechanical mechanisms (improved joint stability and reduced passive overload) (Szewczyk, Świta, & Szuciak, 2024). In addition, psychological factors may have influenced the results, as the pain experience is multidimensional. (Silva, & Ribeiro-Filho, 2011)

 

    In this sense, the positive outcomes observed in pain reduction likely result from multiple morphophysiological adaptations induced by the RT program. The literature indicates that excess adipose tissue (Davydov et al., 2025), physical inactivity (De la Corte-Rodriguez et al., 2024), and low muscular strength are associated with hyperalgesia and increased pain sensitivity (D'Onofrio et al., 2023). In particular, increased abdominal adiposity, often associated with inadequate hydration status, may impair endogenous pain modulation mechanisms, thereby intensifying pain perception. (Davydov et al., 2025)

 

    Furthermore, the RT program appeared to act synergistically on these determinants by reducing body fat (abdominal circumference), improving flexibility, strength, and muscular endurance, thereby enhancing biomechanical stability, reducing joint overload, and improving endogenous pain modulation systems, ultimately leading to reductions in pain frequency and intensity. (D'Onofrio et al., 2023)

 

    Although the findings are promising, some limitations should be acknowledged. The quasi-experimental design without a control group limits causal inference. The small sample size, heterogeneity in sex and age, and lack of control over external variables (diet, alcohol consumption, smoking, sleep) may have influenced the magnitude of the observed adaptations.

 

    Sensitivity analysis indicated that the study was powered to detect only large effects (d ≥ 0.68), being insufficient to detect small or moderate effects. It should also be noted that men and women were analyzed together due to the corporate nature of the sample and the limited number of participants, which precluded subgroup analyses. Future studies should consider sex-stratified analyses to better understand adaptive responses. Despite these limitations, the study demonstrates beneficial associations of RT for the health and well-being of military police officers in the state of Pará, providing support for future investigations with more robust designs and larger, more representative samples.

 

Conclusion 

 

    The resistance training program was associated with reductions in body fat indicators, improvements in physical capacities, and decreases in both pain occurrence and intensity in military police officers working in the administrative sector. These results suggest that this approach can contribute to promoting the health, functionality, and quality of life of this population.

 

    The findings reinforce the importance of adopting a physically active lifestyle, particularly in occupational contexts in which maintaining physical fitness is essential for professional performance. In this regard, the implementation of structured exercise programs may represent a relevant approach for preventing musculoskeletal pain, unfavorable changes in body composition, and declines in physical capacities, thereby contributing to the maintenance of functional capacity in military police officers.

 

References 

 

Alecu, S., Onea, G.A., & Badau, D. (2025). Impact of a 12-Week Core Stability Training on Upper Trunk Stability, Trunk Mobility, and Postural Asymmetries in University Students. Life (Basel), 15(12), e1801. https://doi.org/10.3390/life15121801

 

Alonzo, R., Lalva, T., Couper, R.G., & Wilk, P. (2022). Association between physical activity and life satisfaction among adults with multimorbidity in Canada. Canadian Journal of Public Health, 113(4), 598-606. https://doi.org/10.17269/s41997-022-00635-7

 

Anderson, G.S., Zutz, A., & Plecas, D.B. (2011). Police officer back health. The Journal of Criminal Justice Research, 2(1), 1–17. https://www.researchgate.net/publication/281378222

 

Azeredo, P.O., Ribas, R.C.C., Sena, W.S., Oliveira, D.M., Fernandes, E.V., & Gouvêa-e-Silva, L.F. (2021). Atuação do policial militar: reflexo na qualidade de vida e dor. Saúde (Santa Maria), 47(1), e66213. https://doi.org/10.5902/2236583466213

 

Ballin, M., Nordström, P., Niklasson, J., & Nordström, A. (2021). Associations of objectively measured physical activity and sedentary time with the risk of stroke, myocardial infarction or all-cause mortality in 70-year-old men and women: A prospective cohort study. Sports Medicine, 51(2), 339–349. https://doi.org/10.1007/s40279-020-01356-y

 

Barbosa, WG, Saint Martin, DR, Soares, EMKVKS, Fontana, KE, Lan, FY, Kales, SN, Molina, GE, & Porto, LGG (2022). The effects of a 6-month mandatory military police academy training on recruits' physical fitness. Work, 73(4), 1297–1306. https://doi.org/10.3233/WOR-210031

 

Bernardo, V.M., Silva, F.C., Ferreira, E.G., Bento, G.G., Zilch, M.C., & Silva, R. (2016). Physical activity of police officers: A systematic review. Revista Cubana de Medicina Militar, 45(2), 206–214.

 

Booth, F.W., Roberts, C.K., & Laye, M.J. (2012). Lack of exercise is a major cause of chronic diseases. Compr Physiol. 2(2), 1143-211. https://doi.org/10.1002/cphy.c110025

 

Brzycki, M. (1993). Strength testing: Predicting a one-rep max from repetitions to fatigue. Journal of Physical Education, Recreation & Dance, 64(1), 88–90. https://doi.org/10.1080/07303084.1993.10606684

 

Cabral, CEAT, Guerra, FEF, Zugno, LM, Cabral, SAT, Leite, LD, Fernandes Filho, J., & Lima, KC (2013). Muscular strength training does not increase human adults arterial stiffness or improve body toning. Revista de Salud Pública, 15(4), 601–613. https://www.researchgate.net/publication/264829713

 

Callou Filho, CR, Fontenele, LL, Felipe, PHJ, Lima, VLS, Pereira, GS, Thomaz, AM, Campos, CGS, & Oliveira, TQ (2024). High load vs. low load in resistance training practitioners: Which is more beneficial for hypertrophy and strength gains? A systematic review. Lecturas: Educación Física y Deportes, 29(315), 194–210. https://doi.org/10.46642/efd.v29i315.7234

 

Cassemiro, B.M., Lemes, I.R., Figueiredo, M.P.F., Vanderlei, F.M., Pastre, C.M., & Netto, J.E. (2017). Effects of functional resistance training on muscle strength and musculoskeletal discomfort. Fisioterapia em Movimento, 30(2), 347–356. https://doi.org/10.1590/1980-5918.030.002.AO15

 

Cohen, J. (1988). Análise de poder estatístico para as ciências comportamentais. Routledge Academic.

 

Corlett, E.N., & Bishop, R.P. (1976). A technique for assessing postural discomfort. Ergonomics, 19(2), 175–182. https://doi.org/10.1080/00140137608931530

 

Damasceno, R.K.V., Benevides, A.C.S., Cunha, D.O., Lima, D.L.F., Gonzalez, R.H., & Mendonça, F.C.F. (2016). Body Composition and Anthropometric Data of Military Policies of the Shell Battalion of the State of Ceará. Saúde e Desenvolvimento Humano, 4(2), 109–119. https://doi.org/10.18316/2317-8582.16.35

 

Davydov, D.M., Garcia-Hernandez, A., Galvez-Sánchez, C.M., Andrade-Ortega, J.A., Reyes Del Paso, G.A. (2025). Opposing roles of body fat and hydration in pain: Insights from chronic pain, healthy, and general populations. Clin Nutr ESPEN. 70, 701-718. https://doi.org/10.1016/j.clnesp.2025.11.019

 

De la Corte-Rodriguez, H., Roman-Belmonte, J.M., Resino-Luis, C., Madrid-Gonzalez, J., & Rodriguez-Merchan, E.C. (2024). The Role of Physical Exercise in Chronic Musculoskeletal Pain: Best Medicine-A Narrative Review. Healthcare (Basel). 12(2). https://doi.org/10.3390/healthcare12020242

 

De Oliveira, RR, Aquino, JBDC, Reis, CHO, Oliveira, GS, Vieira, LA, Machado, AF, Rica, RL, Bullo, V., Bergamin, M., Gobbo, S., & Bocalini, DS (2023). Skeletal Muscle Discomfort and Lifestyle of Brazilian Military Police Officers of Administrative and Tactical Force. J Funct Morphol Kinesiol, 8(4). https://doi.org/10.3390/jfmk8040148

 

Dias, I., Farinatti, P., Souza, MGC, Manhanini, DP, Balthazar, E., Dantas, DLS, Pinto, EHA, Bouskela, E., & Kraemer-Aguiar, ALG (2015). Effects of resistance training on obese adolescents. Medicine & Science in Sports & Exercise, 47(12), 2636–2644. https://doi.org/10.1249/mss.0000000000000705

 

D'Onofrio, G., Kirschner, J., Prather, H., Goldman, D., & Rozanski, A. (2023) Musculoskeletal exercise: Its role in promoting health and longevity. Prog Cardiovasc Dis. 77, 25-36. https://doi.org/10.1016/j.pcad.2023.02.006

 

Esteves, J.V.D.C., Andrade, M.L., Gealh, L., Andreato, L.V., & Frazói de Moraes, S.M. (2014). Characterization of the physical condition and cardiovascular risk of highway police officers. Revista Andaluza de Medicina del Deporte, 7(2), 66–71. https://scielo.isciii.es/scielo.php?pid=S1888-75462014000200005&script=sci_abstract&tlng=en

 

Fernandes Filho, J. (2003). A prática da avaliação física (2nd ed.). Shape Editora.

 

Fleck, S., & Simão, R. (2008). Força: Princípios metodológicos para o treinamento. Phorte Editora.

 

Grgic, J., Lazinica, B., Schoenfeld, B.J., & Pedisic, Z. (2020). Test-Retest Reliability of the One-Repetition Maximum (1RM) Strength Assessment: a Systematic Review. Sports Med Open. 6(1). https://doi.org/10.1186/s40798-020-00260-z

 

Häkkinen, K., & Häkkinen, A. (1995). Neuromuscular adaptations during intensive strength training in middle-aged and elderly males and females. Electromyography and Clinical Neurophysiology, 35(3), 137–147. https://pubmed.ncbi.nlm.nih.gov/7649060/

 

Häkkinen, K., Newton, RU, Gordon, SE, McCormick, M., Volek, JS, Nindl, BC, Gotshalk, LA, Campbell, WW, Evans, WJ, Häkkinen, A., Humphries, BJ, & Kraemer, WJ (1998). Changes in muscle morphology, electromyographic activity and force production characteristics during progressive strength training in young and older men. Journals of Gerontology - Series A Biological Sciences and Medical Sciences, 53(6), B415–B423. https://doi.org/10.1093/gerona/53a.6.b415

 

Hoflinger, F., Rodacki, ALF, Tavares, JM, Fadel Neto, MI, Paulo, AC, Fowler, NE, & Rodacki, CLN (2021). A cross-sectional analysis of the muscle strength, spinal shrinkage, and recovery during a working day of military police officers. J Occup Health. 63(1). https://doi.org/10.1002/1348-9585

 

Kyle, UG, Bosaeus, I., De Lorenzo, AD, Deurenberg, P., Elia, M., Gómez, JM, Heitmann, BL, Kent-Smith, L., Melchior, JC, Pirlich, M., Scharfetter, H., Schols, AM, & Pichard, C. (2004). Bioelectrical impedance analysis--part I: review of principles and methods. O Clin Nutr. 23(5), 1226-43. https://doi.org/10.1016/j.clnu.2004.06.004

 

Lima-Dos-Santos, AL, Domingos-Gomes, JR, Andrade, OSD, Cirilo-Sousa, MDS, Freitas, EDS, Silva, JCG, Izidorio, PJG, & Aniceto, RR (2020). Health-related physical fitness of military police officers in Paraiba, Brazil. Revista Brasileira de Medicina do Trabalho, 16(4), 429–435. https://doi.org/10.5327/Z1679443520180304

 

Lopes, S.L., Silva, M.L., Fernandes, E.V., Cunha, K.C., & Gouvea-e-Silva, L.F. (2023). Dor, nível de atividade física e comportamento sedentário em estudantes de fisioterapia. Lecturas: Educación Física y Deportes, 27(298), 102–124. https://doi.org/10.46642/efd.v27i298.3866

 

Małkowska, P. (2024). Positive effects of physical activity on insulin signaling. Current Issues in Molecular Biology, 46(6), 5467–5487. https://doi.org/10.3390/cimb46060327

 

Marins, E.F., & Del Vecchio, F.B. (2017). Programa Patrulha da Saúde: indicadores de saúde em policiais rodoviários federais. Scientia Medica, 27(2), e25855. https://doi.org/10.15448/1980-6108.2017.2.25855

 

Moreira, E.P.F., & Frómeta, E.R. (2021). Insuficiente ejercicio, su incidencia en el rendimiento en las pruebas físicas de la policía nacional. Lecturas: Educación Física y Deportes, 25(274), 134–144. https://doi.org/10.46642/efd.v25i274.2817

 

Nygaard, N.B., Thomsen, G.F., Rasmussen, J., Skadhauge, L.R., & Gram, B. (2022). Ergonomic and individual risk factors for musculoskeletal pain in the ageing workforce. BMC Public Health, 22(1), 1975. https://doi.org/10.1186/s12889-022-14386-0

 

Oliveira, L.C.N., Trindade, A.P.N.T., Bezerra, M.I.S., Garcia Júnior, J.R., & Quemelo, P.R.V. (2015). Obesidade e volume de atividade física em policiais militares. Revista Científica da Federação Internacional de Educação Física, 85(1).

 

Pollock, M.L., & Wilmore, J.H. (1993). Exercícios na saúde e na doença (2nd ed.). Editorial Medsi.

 

Rocha, P.E.C.P., Silva, V.S.D., Camacho, L.A.B., & Vasconcelos, A.G.G. (2015). Effects of long-term resistance training on obesity indicators: A systematic review. Revista Brasileira de Cineantropometria e Desempenho Humano, 17(5), 621–634. https://doi.org/10.5007/1980-0037.2015v17n5p621

 

Rosenfeldt, M., Stien, N., Behm, D.G., Saeterbakken, A.H., & Andersen, V. (2024). Comparison of resistance training vs static stretching on flexibility and maximal strength in healthy physically active adults: A randomized controlled trial. BMC Sports Science, Medicine and Rehabilitation, 16(1), 142. https://doi.org/10.1186/s13102-024-00934-1

 

Ross, R., Dagnone, D., Jones, PJ, Smith, H., Paddags, A., Hudson, R., & Janssen, I. (2000). Reduction in obesity and related comorbid conditions after diet-induced weight loss or exercise-induced weight loss in men. A randomized, controlled trial. Ann Intern Med. 133(2), 92-103. https://doi.org/10.7326/0003-4819-133-2-200007180-00008

 

Sato, K., Arasaki, N., Agena, S., Shimabukuro, S., Sueyoshi, Y., Nakayama, Y., Tanaka, S., Koike, M., & Ogawa, T. (2025). Body composition and absenteeism risk among employees. Clinical Nutrition ESPEN, 69, 545–550. https://doi.org/10.1016/j.clnesp.2025.07.1119

 

Shangguan, Y., Yu, S., Sim, Y.J., Huang, K., Yuan, H., Wang, Y., Chen, C., Lin, Z., & Zhu, Z. (2025). Association between cardiometabolic index with muscle mass and strength in US adults: A cross-sectional study. Medicine, 104(47), e46128. https://doi.org/10.1097/MD.00000000046128

 

Sharma, N., Chahal, A., Balasubramanian, K., Sanjeevi, RR, Rai, RH, Bansal, N., Muthukrishnan, R., & Sharma, A. (2023). Effects of resistance training on muscular strength, endurance, body composition and functional performance among sarcopenic patients: a systematic review. J Diabetes Metab Disord. 22(2), 1053-1071. https://doi.org/10.1007/s40200-023-01283-5

 

Sheng, M., Yang, J., Bao, M., Chen, T., Cai, R., Zhang, N., Chen, H., Liu, M., Wu, X., Zhang, B., Liu, Y., & Chao, J. (2021). The relationships between step count and all-cause mortality and cardiovascular events: A dose-response meta-analysis. Journal of Sport and Health Science, 10(6), 620–628. https://doi.org/10.1016/j.jshs.2021.09.004

 

Silva, J.A., & Ribeiro-Filho, N.P. (2011). A dor como um problema psicofísico. Revista Dor, 12(2), 138–151. https://doi.org/10.1590/S1806-00132011000200011

 

Stens, NA, Bakker, EA, Mañas, A., Buffart, LM, Ortega, FB, Lee, DC, Thompson, PD, Thijssen, DHJ, & Eijsvogels, TMH (2023). Relationship of daily step counts to all-cause mortality and cardiovascular events. Journal of the American College of Cardiology, 82(15), 1483–1494. https://doi.org/10.1016/j.jacc.2023.07.029

 

Szewczyk, J., Świta, M., & Szuciak, A. (2024). The impact of strength training on the prevention of orthopedic injuries in sports: A literature review. Quality in Sport, 31, 55268. https://doi.org/10.12775/QS.2024.31.55268

 

Tavares Neto, A., Faleiro, T.B., Moreira, F.D., Jambeiro, J.S., & Schulz, R.S. (2013). Lombalgia na atividade policial militar: análise da prevalência, repercussões laborativas e custo indireto. Revista Baiana de Saúde Pública, 37(2), 365–374. https://doi.org/10.22278/2318-2660.2013.v37.n2.a336

 

Vaara, JP, Groeller, H., Drain, J., Kyröläinen, H., Pihlainen, K., Ojanen, T., Connaboy, C., Santtila, M., Agostinelli, P., & Nindl, BC (2022). Physical training considerations to optimize performance in essential military tasks. European Journal of Sport Science, 22(1), 43–57. https://doi.org/10.1080/17461391.2012.1.19303

 

Van Duijvenbode, D.C., Hoozemans, M.J., & Van Poppel, M.N. (2009). The relationship between overweight and obesity, and sick leave: A systematic review. International Journal of Obesity, 33(8), 807–816. https://doi.org/10.1038/ijo.2009.121

 

Walling, K., Sundelin, G., Ahlgren, C., & Järvholm, B. (2000). Perceived pain before and after three exercise programs: A controlled clinical trial of women with work-related trapezius myalgia. Pain, 85(1–2), 201–207. https://doi.org/10.1016/s0304-3959(99)00265-1

 

Wang, Y., Wu, Z., Wang, D., Huang, C., Xu, J., Liu, C., & Yang, C. (2022). Muscle-brain communication in pain: The key role of myokines. Brain Research Bulletin, 179, 25–35. https://doi.org/10.1016/j.brainresbull.2021.11.017

 

World Health Organization (2000). Obesity: preventing and managing the global epidemic: Report of a WHO consultation on obesity. WHO. https://apps.who.int/iris/handle/10665/42330