INTRODUCTION

Obesity unfavorably affects different organ systems, such as cardiovascular and osteomyoarticular¹, reducing the ability to work², increasing public spending³, and increasing the number of morbidity and mortality worldwide from noncommunicable chronic diseases⁴; therefore, the picture is difficult to reverse. Given this, public policies that work with health promotion in the physical and nutritional spheres (lifestyle changes), with the encouragement of regular and systematized physical activity (PA) and healthy nutrition, are substantial for longevity with health and quality of life.

Knee osteoarthritis is one of the osteomyoarticular dysfunctions related to obesity. This dysfunction is characterized by persistent joint pain and limitation of movement, causing a reduction in functional capacity and quality of life, which often culminates in the indication for knee arthroplasty⁵. The respective causes, as mentioned earlier, may be related to biomechanical (joint overload) and chemical (inflammatory marker) factors⁵. For the management of knee osteoarthritis and obesity, studies have pointed out that a multidisciplinary care plan may offer control of disease progression, weight reduction, and, consequently, improvement of health-related components¹.

According to the European League Against Rheumatism (EULAR), nutritional education and physical training are recommended for managing obesity and osteoarthritis to decrease body weight (BW) and improve clinical conditions such as pain, functional disability, stiffness, and joint mobility⁶. Recent scientific evidence shows that resistance training models, using apparatus in the weight room and training with the body’s resistance (commonly referred to as "body weight training"), improve health-related fitness in people with obesity^7,8. However, there is no consensus in the literature about which method or model of resistance training may be more effective in reducing algae and improving health-related fitness and quality of life in overweight or obese women.

Thus, considering that “BW” training is a cost-effective model since it uses only BW and accessories⁹, it is conjectured that this method may be incorporated into the routine for the recovery of health conditions and reduction of disability in overweight or obese people. Finally, it was observed that BW improved health-related physical fitness and reduced pain. In that case, cost-effective strategies can be incorporated on a large scale to improve the quality of life of this population, considering a model of low infrastructural investment.

Therefore, this study aimed to investigate the effects of two multidisciplinary intervention programs, distinguishing between the types of resistance training performed, that is, resistance training on machines or resistance training with BW. It is believed that both intervention models can improve health-related physical fitness and quality of life for obese women with knee pain symptoms.

METHODOLOGY

Experimental design

This is an experimental, longitudinal, randomized, parallel group, and repeated-measures study. The research was approved by the Local Ethics Committee at UniCesumar University, in southern of Brazil, according to the following opinion: 30976420.4.0000.5539. The project was advertised via printed media, the Internet, and television, inviting women between 40 and 59 years of age, within the inclusion criteria, to participate in the research project.

The inclusion criteria were as follows: (i) participants with body mass index (BMI) ≥ 30.00-34.9 kg/m²; (ii) female sex, aged 40-59 years; (iii) presenting three or more of the criteria, namely, morning stiffness lasting < 30 min, crepitus, bone lesion, and no palpable knee lesion, according to the EULAR; (iv) availability to participate in the interventions, three times a week, for 8 weeks; (v) be able to practice PA, via medical clearance; (vi) not participating in another project focused on weight loss; (vii) not performing any nutritional diet; and (viii) agreed and signed the informed consent form (ICF).

The exclusion criteria included the following: (i) participants who underwent knee arthroplasty in the affected joint or any other surgical procedure in the lower limbs in the last 6 months; (ii) who presented with rheumatologic conditions; (iii) who underwent medicated infiltrations in the knee in less than 3 months; (iv) who presented with thrombotic episodes; (v) with decompensated heart disease; (vi) using a pacemaker or similar device; (vii) with uncontrolled hypertension; (viii) with a confirmed diagnosis of cancer; (ix) with dermatological lesions; (x) unable to walk or use a walking aid; and (xi) unable to understand and complete the proposed instructions and evaluations.

Women who met the inclusion criteria were selected and instructed about the research procedures, signed the ICF, and were subsequently randomized (www.randomizer.org) into two experimental groups: strength training on machines or BW training. The sample calculation indicated that 10 people per group would be sufficient to present an α = 0.05 and β = 80%, whose variables were BMI and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). A flowchart of the present study is presented inFigure 1.

Figure 1: Flowchart of the present study 

RESULTS

This study verified the participation in the interventions of 59.0 ± 27.7% for the strength training on machines group and 66.2 ± 27.9% for the BW training group, over 8 weeks of intervention. The mean ages were 45.1 ± 5.0 and 45.7 ± 49.9 years for the strength training on machines group and the BW training group, respectively, with no significant difference between them (p>0.05). Moreover, 64% had higher education among the participants, 32% had completed high school, and 4% had incomplete elementary school education. The family income averages were 40% up to 3 minimum wages and 28%, 16%, 8%, and 4% up to 3, 9, 12, and 15 minimum wages, respectively. For all variables investigated, no significant differences were observed in the baseline values (p>0.05). no significant difference was detected among RPE, ITL, and RPR responses at the same points of comparison, suggesting that training intensity and recovery were similar between the groups (p>0.05). In addition, no significant difference was observed to food record data (p>0.05).Table 3presents the anthropometric and body composition responses of the participants in this study.

For MIHS-R, MIHS-L, flexibility, abdominal test, elbow flexion and extension, and VO2peak, no significant differences were observed after 8 weeks of intervention (p>0.05). However, there was a time effect, with a significant increase in MILTS after the intervention (p<0.05), as shown inTable 4

No significant differences were observed in pain, joint stiffness, and physical ability after completing the WOMAC questionnaire among the study participants (p>0.05).Table 5shows the responses to the SF-12 questionnaire for the two experimental groups. No significant differences were observed in the SF-12 questionnaire for physical and mental health domains over 8 weeks of intervention (p>0.05). The same occurred when filling out the IPAQ questionnaire; that is, no significant differences were observed in the level of PA during 8 weeks of intervention (p>0.05). The only difference was the increase in the PA level on the days of intervention, that is, on Mondays, Wednesdays, and Fridays, which was already expected since the participants performed resistance exercises on these days.

DISCUSSION

The present study aimed to analyze the different anthropometric variables and body composition in physical fitness in obese women with knee pain symptoms who underwent two modalities of resistance exercises. In this sense, the following responses were observed: (i) absence of significant differences in the variables of BW, height, BMI, SMM, FM, and BFP for both experimental groups; (ii) absence of significant differences in the tests of physical fitness for both experimental groups (MIHS-R, MIHS-L, abdominals in 60 s, elbow flexion and extension, and VO2peak); (iii) the only difference observed for the health-related fitness tests was for the MILTS, with significant improvement for both experimental groups; (iv) no differences in the responses of the WOMAC, SF-12, and IPAQ questionnaires; (v) no differences in the responses of the food record; and (vi) no differences in the responses of the RPE, ITL, and RPE between the two resistance training models.

The absence of differences in the anthropometric and body composition variables can be explained by the low energy expenditure promoted by the training sessions and moderate adherence to the interventional process. Energy expenditure is dependent on the following factors: thermal effect of food, resting metabolic rate (RMR), and PA level; the latter is dependent on the energy expenditure of structured and unstructured physical activities during the day²⁴.

However, weight loss is not linear since the body tends to self-regulate, even with adequate nutrition and regular PA practice, depending on physiological factors²⁵. According to MacKenzie-Shalders et al.²⁶, resistance training does not accelerate the metabolism to the point of obtaining high weight loss because a gain of 1 kg of muscle increases the caloric expenditure by 13 kcal, a factor that alone does not promote weight loss; therefore, the weight loss process is complex and multifactorial and involves lifestyle changes. Weight loss must constantly be associated with reduced caloric intake and increased levels of PA (structured and unstructured activities throughout the day). Therefore, in this situation, the literature points out that the reduction in body fat is still small in interventions of only 8 weeks’ duration²⁷. An aggravating factor for the absence of changes in the anthropometric and body composition variables can be justified by the moderate compliance of participants during the 8-week intervention (approximately 59%-66%). On the other hand, when considering that the interventions were performed in the most restricted period of the pandemic in the locality where the project was conducted, it is believed that the results were satisfactory since there was no adverse modification of the anthropometric and body composition variables, since, during the pandemic, an increase in BW was observed². Although no significant differences were observed for the anthropometric and body composition variables in this study, Swift et al.²⁸emphasized that a physical training program for treating obesity is essential for maintaining muscle mass in the long term.

It is essential to highlight that activities in home-office mode (to contain the pandemic) probably presented low energy expenditure, and consequently, the body in the medium and long term, with reduced energy expenditure and increased caloric intake, provided more significant accumulation of body fat. Although no differences were observed in the main variables investigated in this study, physical, nutritional, and behavioral changes are linked to long-term work; if maintained, the intention to change behavior will probably improve practitioners’ health and quality of life⁶. As a result, a reduction in sedentary time is pertinent, reducing sitting time with daily life activities at home and at work with slight changes, that is, choosing to use the stairs rather than the elevator, standing up every 30 or 60 min and then walking or stretching, walking further instead of using the car or public transport, and using the daily step counter and setting goals, in addition to reducing the salt, sugar, and fat intake. Therefore, tangible goals can be arranged to change a healthy lifestyle.

Another relevant point is the age factor: it is known that the aging process is natural, resulting in physiological changes, reduced physical and motor capacities, degenerative processes, increased body fat, and reduced muscle mass. Therefore, the components of physical fitness need to be stimulated to slow these reductions and improve physical and mental health⁸. Thus, although the participants missed an average of 35%-40% of the interventions, the MILTS increased significantly. The increase in the MILTS is a highly positive response since back pain considerably affects the Brazilian and global populations²⁹.

It is also worth mentioning that the reduction in muscle mass, fat accumulation, and poor posture cause lower back pain and pain in some joints, which, in turn, can modify the physiological curvature, leading to weakness and pain in the postural muscles, in addition to a muscular imbalance of the trunk and lower limbs²⁹. In obese individuals, reduced strength and increased fatigue are evident when exposed to complex tasks that require high intensity³⁰. In the present study, the significant improvement in the MILTS contributed to the muscles responsible for posture, reducing the risks of future muscle pain and fatigue. Moreover, some studies have shown that an active lifestyle is beneficial because participants develop a delay in the onset of functional, cardiorespiratory, postural, balance, and muscle endurance limitations to perform daily tasks with greater competence, preventing falls and fractures³¹. For Kocjan and Sarabon²⁹, the isometric strength of the trunk acts in the maintenance of strength in the core and stabilization and minimizes the overload of the spine, thus generating dynamic postural control and improving the hip angle; however, the pandemic and the changes from work to home-office form, exceeding the hours sitting in the same position, resulted in an increase in back pain complaints. This possibility is supported by Salve and Bankoff³¹, who state that hours in the sitting position reduce musculoskeletal fitness and increase nonspecific low back pain; therefore, people expend less energy and maintain poor posture. In this sense, the response of the study may be relevant for the reduction of work leaves due to increased pain, restricted movement, and especially muscle fiber atrophy³².

Other studies with comparative approaches between resistance training methods equalized by the main muscle groups, volume, and intensity of training sessions did not find significant differences between the types of intervention^33-35. In this sense, Branco et al.³⁴compared the effects of two resistance training methods (conventional weight training vs. BW and accessory training) on body composition, physical fitness, and biochemical measures. Given this, the previous study results showed similar improvements of health-related fitness components, with no significant difference observed between the intervention groups in the condition where training was equalized. To compare different training exercise methods, the equalization of intensity, volume, and primary muscle groups should be considered. In addition, despite the limitations of the psychometric scales, previous studies have reported consistent responses using these resources^33-35.

Thus, physical therapists or physical education professionals need to consider motor actions when the training is designed. If many people are being served simultaneously, we suggest using cost-effective resources to serve more people, with less expenditure on equipment and/or accessories. Finally, the three studies cited^33-35equalized the main health variables of interest in interventions to combat obesity. In summary, no significant differences were observed between BW and weight training on machines, order of exercises, aerobic or resistance training, and sports practice versus functional training. Although the three studies mentioned earlier presented adolescents as the sample, it is believed that the main factor for comparison and obtaining similar answers refers to the equalization process.

There were no differences in the answers to the WOMAC and SF-12 questionnaires during the intervention period. According to Hurley et al.³⁶, the participants had some beliefs and/or resistance regarding improving pain and physical function, support, adequate assistance, and confidence in performing the exercises. It is noted that the absence of differences in the responses to the SF-12 questionnaire may be associated with the period of social isolation, which may have affected the mental health of the participants (increased anxiety and insecurity and lowered self-esteem)³⁷. Thus, based on the results of this study, it is highlighted that the absence of significant differences cannot be analyzed only by statistical analysis to confirm or reject the eventual benefits of the program for the recovery of the participants’ health conditions. Considering that the process of behavioral changes for adherence to PA practice and the change in the eating pattern is a lifelong process, the first step was performed, referring to the encouragement of PA for groups in physical, nutritional, and psychosocial vulnerability.

CONCLUSION

No significant differences were observed for the anthropometric, body composition, physical fitness variables (except for MILTS), WOMAC, SF-12, IPAQ questionnaires, food record or women’s RPR, ILT, and RPE. The absence of significant differences may be justified by the moderate adherence of the participants to the study since the study was conducted during a period of more restricted social isolation. However, it is believed that the intervention models were positive in any decrease in health components analyzed in the present study.