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Volume 15, Issue 3 (Summer 2025)
PTJ 2025, 15(3): 205-216 |
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Haghighi A, Ebrahimi M, Askari R, Nouri G, khademosharie M. The Effects of Two Different Intensities of Concurrent Training on Pulmonary Function in Female Patients With Type II Diabetes. PTJ 2025; 15 (3) :205-216
URL: http://ptj.uswr.ac.ir/article-1-661-en.html
URL: http://ptj.uswr.ac.ir/article-1-661-en.html
Amirhossein Haghighi *1 
, Malihe Ebrahimi1 , Roya Askari1 , Gholamreza Nouri2 , Mitra Khademosharie3
, Malihe Ebrahimi1 , Roya Askari1 , Gholamreza Nouri2 , Mitra Khademosharie3
1- Department of Exercise Physiology, Faculty of Sport Sciences, Hakim Sabzevari University, Sabzevar, Iran.
2- Vasei Hospital, Sabzevari University of Medical Sicences, Sabzevar, Iran.
3- Department of Sport Sciences, Faculty of Humanities, Kosar University of Bojnord, Bojnord, Iran.
2- Vasei Hospital, Sabzevari University of Medical Sicences, Sabzevar, Iran.
3- Department of Sport Sciences, Faculty of Humanities, Kosar University of Bojnord, Bojnord, Iran.
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Introduction
Diabetes mellitus is a metabolic disorder that causes a lack of insulin production, a deficiency in its action, or both, resulting in hyperglycemia with impaired carbohydrate, lipid, and protein metabolism. The disease is chronic, serious, and progressive, with multiple damages to various organs. Major and long-term complications of diabetes include cardiovascular disease, diabetic nephropathy, diabetic retinopathy, and damage to other organs, such as the lungs. All of these result from macrovascular and microvascular damage [1].
The association between decreased lung function and diabetes has been described for many years, although the clinical significance of this association is unknown [2, 3]. Potential links between respiratory disorders and diabetes may be attributed to factors, such as elevated body mass index, reduced respiratory efficiency, neuropathy, weakened respiratory muscle strength, and other contributing variables [2]. Additionally, biochemical abnormalities, including inadequate glucose regulation, play a critical role in elevating the risk of pulmonary complications and related health conditions in individuals with diabetes [4, 5].
Pathological studies have shown that the causes of pulmonary dysfunction in patients with diabetes are the major changes in lung tissues, such as changes in the thickness of the alveolar wall, the thickness of the alveolar capillaries, and the lining thickness of the arterioles. Researchers have identified the main causes of these respiratory disorders as hyperglycemia and glycosylation of the chest wall muscles [6]. Some other studies have shown that increased respiratory infections, inflammation, and oxidative stress induced by diabetes reduce respiratory muscle function and limit pulmonary function [7-9]. The Women’s cardiovascular health research center of Britannia showed that insulin resistance and diabetes are associated with reductions in forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) [10].
Various studies have suggested that physical activities can be effective in the prevention, control, and treatment of diabetes. Regular moderate exercise is effective in preventing and delaying the onset of diabetes mellitus (DM), increases insulin sensitivity, and improves glucose metabolism [11, 12]. Moreover, exercise training has been considered a therapeutic intervention in the pulmonary rehabilitation program of patients with pulmonary dysfunction [13, 14]. However, the type, severity, and duration of these exercises need further investigation. The American College of Sports Medicine and the American Diabetes Association have confirmed that rehabilitation programs for patients with diabetes should combine aerobic and resistance exercises to maximize the beneficial effects of both types of exercise [15].
Combining aerobic exercise with resistance training offers greater benefits than either modality alone in reducing inflammatory markers, regulating blood sugar and insulin function, and improving cardiovascular disease risk factors [16-19]. Despite extensive research on cardiovascular complications and diabetic nephropathy, retinopathy, and neuropathy, reduced pulmonary function in diabetic patients has received comparatively less attention. Additionally, studies investigating the effects of concurrent exercises on pulmonary function are relatively scarce. For instance, Tunkamnerdthai et al. demonstrated that an 8-week push-up exercise program (three sessions per week) improved FEV1, FVC, and maximal voluntary ventilation (MVV) while reducing HbA1c levels, although the FEV1/FVC ratio remained unchanged [20]. Similarly, Osho et al. examined the effects of a 12-week aerobic-strength training program (with and without weights) on the pulmonary function of 60 patients with type 2 diabetes aged 40–75 years. Their findings revealed significant improvements in VO2 max, FEV1, and HbA1c levels, with FVC and FEV1 indices showing greater enhancement in concurrent training with weights compared to training without weights or the control group [21].
Kim et al. stated that exercise training intensity is one of the factors that affect the strength and resistance of respiratory muscles and pulmonary function [22]. Concurrent exercise programs can enhance respiratory muscle strength and endurance, combining aerobic and resistance training components. Aerobic exercises, such as cycling or walking improve oxygen exchange efficiency and lung capacity, while resistance training strengthens the muscles involved in breathing—beneficial for individuals with type 2 diabetes who may experience respiratory muscle weakness due to the disease or a sedentary lifestyle [23]. Additionally, regular exercise has been shown to improve glycemic control, reflected in lower HbA1c levels. Concurrent exercise programs are particularly effective as they combine the immediate blood sugar-lowering effects of aerobic exercise with the longer-term benefits of resistance training on insulin sensitivity [24]. However, the optimal intensity, frequency, and duration of such programs for individuals with type 2 diabetes remain under investigation. Tailoring these programs to an individual’s fitness level, comorbidities, and medication regimen is critical for safety and effectiveness. Further research is warranted to fully elucidate the effects of concurrent exercise programs on respiratory muscle function, body composition, glycemic control, and overall physical condition in this population. Such studies should also address unique considerations for this group, including hypoglycemia risk, medication interactions, and the influence of diet and other lifestyle factors.
However, the effect of intensity of a concurrent exercise program on respiratory muscles, improvement of body composition, HbA1c, and the physical condition of people with type 2 diabetes is not taken into account and needs further investigation. Therefore, this study was designed to investigate the effect of a concurrent exercise training (aerobic and resistance) program with different intensities (high and low) on the pulmonary function of women with type 2 diabetes.
Materials and Methods
Study sample
The research method was quasi-experimental with pre-test and post-test design. The statistical population included obese women with type 2 diabetes who attended the diabetes community in Sabzevar and had medical records in this medical center. Thirty-four individuals with a history of at least five years of diabetes were selected through availability sampling according to the inclusion criteria. The inclusion criteria were women aged 45-60 years (all subjects were evaluated by a specialist and confirmed to be menopausal); a body mass index (BMI) of 27 to 34 kg/m²; no other diseases (such as autoimmune disorders, respiratory diseases, liver disease, cardiac ischemia, kidney disease, chronic inflammatory diseases, thyroid diseases, stomach ulcers, and infection), a diagnosis of type 2 diabetes; fasting blood glucose levels of less than 180 mg/dl; a 2-hour glucose level of less than 250 mg/dl; no insulin injections; non-smokers; no participation in regular sports programs during the past six months; and the ability to attend the study for three months. Individuals who did not meet these conditions were excluded from the study. Subsequently, ten participants refused to continue their participation for personal reasons and due to disease progression. The remaining 24 subjects were randomly assigned to three groups: low-intensity exercise (8 individuals), high-intensity exercise (8 individuals), and a control group (8 individuals). Written informed consent was obtained from all participants.
Training program
The study began at the sports physiology laboratory at Hakim Sabzevari University for anthropometric and physiological measurements on December 5, 2021. Height, weight, body fat percentage, and waist-hip ratio were measured one week before the beginning of the training program. The following two to three sessions were held in the practice hall to familiarize participants with the training conditions. The training intervention consisted of 12 weeks of concurrent exercise, combining resistance and aerobic activities, performed at two intensity levels: High intensity (resistance at 75–85% of 1-RM and aerobic at 70–85% of maximum heart rate) and low intensity (resistance at 50–75% of 1-RM and aerobic at 50–70% of maximum heart rate). Participants completed three nonconsecutive sessions per week, with each session lasting between 55 and 70 minutes.
The training program of high-intensity concurrent exercises group
The program consisted of 10 minutes of warm-up (jogging, hand and foot movements combined with stretching), followed by 30 minutes of strength training and 10 minutes of cool-down. The stations included bench presses, dumbbell bicep curls, triceps pushdowns, seated leg extensions, leg curls, butterfly exercises, and underhand cable pull-downs. The exercises were performed in accordance with Table 1. The rest interval between each station was set at 120 seconds. After a 15-20 minute rest, 20 minutes of aerobic running training was conducted, featuring 10-12 repetitions for 1 minute at 70-85% of the maximum heart rate, with 30 seconds of active rest between sets at 30-40% of the maximum heart rate (Table 1).
The training program of low-intensity concurrent exercises group
This program included 10 minutes of warm-up, 30 minutes of strength training exercises, and 10 minutes of cool-down. The rest interval between stations was considered also set at 120 seconds. After 20 minutes, aerobic running training at low intensity was performed according to Table 2.
Measurements
Blood samples were collected at two stages: Before and 24 hours after the last session, following a 10-12 hour fasting period. Glycosylated hemoglobin (HbA1c) was measured through an enzymatic colorimetric method with the Nicoard kit (made in Norway, catalog number 1042184), which has a coefficient of variation (CV) of less than 5%. To calculate the body fat percentage, a baseline caliper was used to measure subcutaneous fat in three areas: The thigh, upper pelvic area, and arm triceps, along with the Jackson and Pollock formulas [25]. Maximum oxygen consumption was measured using the Rockport 1-mile (1609 m) Walk Test [21, 26]. Indices of respiratory and pulmonary function were measured with a spirometer (model: CHESTGRAPH HI-701, France). The upper body strength was calculated using the bench press movement and the Brzycki Equation 1
1. 1RM=Weight÷(1.0278–(0.0278×number of repetitions)
Provided that the number of repetitions fell between six and ten repetitions. Upper body muscular strength was computed by the press movement and maximum repetitions to fatigue with 60% of 1RM [27, 28].
To measure the specific strength of the respiratory muscles, a spirometer was used [29]. After a full exhale, the subject was asked to place the mouthpiece in their mouth and breathe in sharply. As the subject inhaled, the piston moved upward, and the highest number displayed was considered the specific strength of the respiratory muscles. This test was repeated three times and the maximum value was calculated. At the same time, in order to monitor the participant’s diet, a 24-hour dietary recall questionnaire, and the three-day dietary records from the beginning and end of the study were used. Food data were analyzed using Nutrition software, version 4.
Statistical methods
Data were described as Mean±SD. The normality of the samples’ distribution was assessed using the Shapiro-Wilk test with Lilliefors correction for small samples, demonstrating a normal distribution for all samples. Treatment effects were analyzed using a two-way ANOVA (IBM SPSS software, version 21, Armonk, VA, USA). A significant interaction effect (group×time) indicated a treatment-dependent difference in the development from pre-test to post-test among the group conditions. Significance was accepted for P≤0.05.
Results
This study showed that 12 weeks of concurrent training at different intensities had significant therapeutic effects on some pulmonary variables, HbA1c values, and body fat percentage in women with type 2 diabetes. Table 3 shows the characteristics of the patients. Table 4 provides an overview of all physiological and functional variables, while Table 5 presents an overview of all respiratory variables.
.PNG)
For several respiratory and physiological parameters, a significant interaction effect (group×time: P<0.05) was found, demonstrating a considerable influence of the respective treatments on the development from the pre-test to the post-test: FEF25, FEF50, FEF2575, FEV1/FVC, HbA1c, and fat percentage (Tables 4 and 5).
There were no significant group effects for other respiratory parameters (P>0.05). For some respiratory, physiological, and functional parameters, significant time effects were observed (P<0.05), indicating a significant change between the pre-test and post-test that was independent of the type of treatment: FVC, FEV, peak expiratory flow (PEF), FEF75, MVV, VO2max, upper body power, and upper body endurance (Tables 4 and 5).
Discussion
This study demonstrated that a 12-week concurrent training program with varying intensities had significant therapeutic effects on certain pulmonary variables, HbA1c levels, and body fat percentage in women with type 2 diabetes. These findings align with those of Silva-Reis et al. who reported that concurrent training enhances lung mechanics and reduces lung inflammation in overweight and obese women [30]. Similarly, Silva-Reis et al. found that concurrent exercise improved lung function, mechanics, and pulmonary immune responses in overweight and stage 1 obese women by elevating levels of the anti-fibrotic protein Klotho while reducing fibrotic IGF-1 [31]. These improvements were attributed to IGF-1, which is recognized as a primary growth factor overproduced in conditions, such as asthma and obesity. In asthma, IGF-1 plays a role in modulating airway inflammation, smooth muscle hyperresponsiveness, and hypertrophy, ultimately affecting lung mechanics [32]. Tunkamnerdthai et al. observed that an eight-week arm swing exercise program (three sessions per week) led to improvements in FEV1, FVC, and MVV while lowering HbA1c levels; however, the FEV1/FVC ratio remained unchanged in their study [20].
Osho et al. also documented significant enhancements in VO2max, FVC, FEV1, and HbA1c levels among 60 individuals with type 2 diabetes aged between 40 and 75 years [26]. Additionally, Chen et al. reported a notable increase in PEF following an eight-week kettlebell training program, indicating improved pulmonary function after exercise [33]. These findings suggest that the respiratory muscles of the participants in this study were effectively trained, resulting in significant improvements in PEF. While prior studies on resistance training in older adults have primarily examined its benefits for individuals with lung injuries or other specific conditions, fewer studies have focused on markers of lung function in this population [34].
Contrary to our findings, Jones and Nzekwu [35] reported no significant changes in lung volume. The results of our study can be explained by the acute enhancements in glucose metabolism that occur immediately after exercise, with these effects lasting for up to 48 hours, as noted by Davis et al. [36].
Poor glucose regulation is linked to microvascular complications and pulmonary respiratory distress [37]. Dyspnea is the leading cause of death in type 2 diabetes after adjusting for other known risk factors [38]. The reduction in mean HbA1c levels observed in this study, which aligns with findings from other research [37, 38] but contrasts with those reported by Sigal et al. [39], may contribute to significant improvements in FEV1/FVC values.
FVC is influenced by factors, such as age, physical activity level, body composition and health, respiratory muscle strength, and lung elasticity [40]. Additionally, the extent of lung volume reduction and airflow limitation correlates with glucose levels and body fat [41]. Hence, the increase in FVC observed in this study following concurrent training may be attributed to enhanced respiratory muscle strength and power, reduced body fat, and lower fasting blood glucose in patients with diabetes. However, the 12-week concurrent training program did not lead to a significant increase in FEV1 among women with type 2 diabetes in either training group. This outcome contrasts with findings from studies conducted by Osho et al. and Beckerman et al. [42]. FEV1, a specific measure of respiratory function, is affected by various factors. A decline in FEV1 indicates reduced lung capacity, airway obstruction, decreased lung reversibility, or, less commonly, insufficient respiratory muscle development. Thus, improving respiratory muscle strength can also enhance FEV1 [40]. As FEV1 serves as an indicator of respiratory muscle strength, it appears that exercises targeting the enhancement of respiratory muscle strength may contribute to increased FEV1 levels [43].
Many studies have reported reduced pulmonary function in diabetic patients, largely due to diminished strength and power of the respiratory muscles. In the present study, while upper and lower body muscle strength and power increased in both the low- and high-intensity training groups, these changes were not statistically significant. Although the strengthened muscles in this study primarily served as supporting muscles for pulmonary function rather than the primary muscles involved in respiration, their long-term strengthening appeared to contribute to improvements in respiratory system function. Additionally, aerobic training may enhance the diaphragm, intercostal, and abdominal muscles while reducing resistance in the respiratory tract. Notably, the specific strength of respiratory muscles, as measured by spirometry, improved in the low-intensity concurrent training group. This underscores the combined role of aerobic and resistance exercises in promoting pulmonary function. Prior research has also shown a positive and significant correlation between cardiovascular fitness (VO2max) and pulmonary function indices, such as FEV1 and FVC [44, 45].
The respiratory and cardiovascular systems collaborate closely to deliver oxygen to cells and regulate the internal environment of the body during both rest and activity. This partnership ensures a balance between ventilation and cardiac function in the gas exchange process that links skeletal muscles to atmospheric air. Any inefficiency in these systems can impair overall body function. When the ventilation-to-blood flow ratio or the ventilation-to-oxygen absorption and removal ratio declines relative to ventilation volume, respiratory muscles consume more energy, increasing the likelihood of premature fatigue [45]. Although the current study observed improvements in maximum oxygen consumption (VO2max) in both training groups, these changes were not statistically significant. Nevertheless, this factor may partially explain the observed enhancements in pulmonary function. This study demonstrated improvements across several key indicators, including respiratory muscle strength and power, body fat percentage, body weight, physical fitness, aerobic capacity, blood glucose levels, and HbA1c among the participants. The variability in results across studies may stem from differences in participant characteristics, such as gender, age, medical history, exercise program type, number and type of movements, intensity and duration of training, and other program-specific factors. It is important to note that respiratory function is influenced by multiple factors, including the nervous system, neuromuscular coordination, respiratory muscle strength, and lung size. Enhancing respiratory muscle strength and reducing airway resistance through exercise has been shown to improve lung function. Exercise-induced bronchial dilation reduces airway resistance, thereby improving ventilation. Additionally, exercises involving significant muscle engagement can increase breathing rate and depth, which, in turn, enhances FVC, oxygen uptake, and oxygen distribution [46].
Conclusion
The findings of this study indicate that concurrent exercise programs of varying intensities can lead to improvements in selected respiratory and physiological parameters, demonstrating potential benefits for women with type 2 diabetes. Both low- and high-intensity training programs showed some positive effects on specific indicators, suggesting their utility in managing the condition. Based on these results, healthcare professionals and specialists are encouraged to promote such exercise programs as part of a comprehensive management plan for patients with type 2 diabetes to enhance their chances of recovery. However, the study also revealed that a 12-week exercise intervention did not result in significant changes in certain respiratory and physical parameters. This suggests that longer training durations, combined with careful management of confounding factors, such as nutritional habits, may yield more pronounced and consistent improvements.
Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Sabzevar University of Medical Sciences, Sabzevar, Iran (Code: IR.MEDSAB.REC.1396.93). Written informed consent was obtained from the participants.
Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.
Authors' contributions
Conceptualization and supervision: Amirhossein Haghighi and Malihe Ebrahimi; Methodology: Malihe Ebrahimi and Amirhossein Haghighi; Investigation: Malihe Ebrahimi, Roya Askari, Amirhossein Haghighi, Mitra khademosharie; Data collection: Malihe Ebrahimi , Data analysis: Amirhossein Haghighi and Mitra khademosharie; Writing–review & editing: All authors.
Conflict of interest
The authors declared no conflict of interest.
Acknowledgments
The authors thank all their colleagues who helped them in carrying out this research project.
References
Diabetes mellitus is a metabolic disorder that causes a lack of insulin production, a deficiency in its action, or both, resulting in hyperglycemia with impaired carbohydrate, lipid, and protein metabolism. The disease is chronic, serious, and progressive, with multiple damages to various organs. Major and long-term complications of diabetes include cardiovascular disease, diabetic nephropathy, diabetic retinopathy, and damage to other organs, such as the lungs. All of these result from macrovascular and microvascular damage [1].
The association between decreased lung function and diabetes has been described for many years, although the clinical significance of this association is unknown [2, 3]. Potential links between respiratory disorders and diabetes may be attributed to factors, such as elevated body mass index, reduced respiratory efficiency, neuropathy, weakened respiratory muscle strength, and other contributing variables [2]. Additionally, biochemical abnormalities, including inadequate glucose regulation, play a critical role in elevating the risk of pulmonary complications and related health conditions in individuals with diabetes [4, 5].
Pathological studies have shown that the causes of pulmonary dysfunction in patients with diabetes are the major changes in lung tissues, such as changes in the thickness of the alveolar wall, the thickness of the alveolar capillaries, and the lining thickness of the arterioles. Researchers have identified the main causes of these respiratory disorders as hyperglycemia and glycosylation of the chest wall muscles [6]. Some other studies have shown that increased respiratory infections, inflammation, and oxidative stress induced by diabetes reduce respiratory muscle function and limit pulmonary function [7-9]. The Women’s cardiovascular health research center of Britannia showed that insulin resistance and diabetes are associated with reductions in forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) [10].
Various studies have suggested that physical activities can be effective in the prevention, control, and treatment of diabetes. Regular moderate exercise is effective in preventing and delaying the onset of diabetes mellitus (DM), increases insulin sensitivity, and improves glucose metabolism [11, 12]. Moreover, exercise training has been considered a therapeutic intervention in the pulmonary rehabilitation program of patients with pulmonary dysfunction [13, 14]. However, the type, severity, and duration of these exercises need further investigation. The American College of Sports Medicine and the American Diabetes Association have confirmed that rehabilitation programs for patients with diabetes should combine aerobic and resistance exercises to maximize the beneficial effects of both types of exercise [15].
Combining aerobic exercise with resistance training offers greater benefits than either modality alone in reducing inflammatory markers, regulating blood sugar and insulin function, and improving cardiovascular disease risk factors [16-19]. Despite extensive research on cardiovascular complications and diabetic nephropathy, retinopathy, and neuropathy, reduced pulmonary function in diabetic patients has received comparatively less attention. Additionally, studies investigating the effects of concurrent exercises on pulmonary function are relatively scarce. For instance, Tunkamnerdthai et al. demonstrated that an 8-week push-up exercise program (three sessions per week) improved FEV1, FVC, and maximal voluntary ventilation (MVV) while reducing HbA1c levels, although the FEV1/FVC ratio remained unchanged [20]. Similarly, Osho et al. examined the effects of a 12-week aerobic-strength training program (with and without weights) on the pulmonary function of 60 patients with type 2 diabetes aged 40–75 years. Their findings revealed significant improvements in VO2 max, FEV1, and HbA1c levels, with FVC and FEV1 indices showing greater enhancement in concurrent training with weights compared to training without weights or the control group [21].
Kim et al. stated that exercise training intensity is one of the factors that affect the strength and resistance of respiratory muscles and pulmonary function [22]. Concurrent exercise programs can enhance respiratory muscle strength and endurance, combining aerobic and resistance training components. Aerobic exercises, such as cycling or walking improve oxygen exchange efficiency and lung capacity, while resistance training strengthens the muscles involved in breathing—beneficial for individuals with type 2 diabetes who may experience respiratory muscle weakness due to the disease or a sedentary lifestyle [23]. Additionally, regular exercise has been shown to improve glycemic control, reflected in lower HbA1c levels. Concurrent exercise programs are particularly effective as they combine the immediate blood sugar-lowering effects of aerobic exercise with the longer-term benefits of resistance training on insulin sensitivity [24]. However, the optimal intensity, frequency, and duration of such programs for individuals with type 2 diabetes remain under investigation. Tailoring these programs to an individual’s fitness level, comorbidities, and medication regimen is critical for safety and effectiveness. Further research is warranted to fully elucidate the effects of concurrent exercise programs on respiratory muscle function, body composition, glycemic control, and overall physical condition in this population. Such studies should also address unique considerations for this group, including hypoglycemia risk, medication interactions, and the influence of diet and other lifestyle factors.
However, the effect of intensity of a concurrent exercise program on respiratory muscles, improvement of body composition, HbA1c, and the physical condition of people with type 2 diabetes is not taken into account and needs further investigation. Therefore, this study was designed to investigate the effect of a concurrent exercise training (aerobic and resistance) program with different intensities (high and low) on the pulmonary function of women with type 2 diabetes.
Materials and Methods
Study sample
The research method was quasi-experimental with pre-test and post-test design. The statistical population included obese women with type 2 diabetes who attended the diabetes community in Sabzevar and had medical records in this medical center. Thirty-four individuals with a history of at least five years of diabetes were selected through availability sampling according to the inclusion criteria. The inclusion criteria were women aged 45-60 years (all subjects were evaluated by a specialist and confirmed to be menopausal); a body mass index (BMI) of 27 to 34 kg/m²; no other diseases (such as autoimmune disorders, respiratory diseases, liver disease, cardiac ischemia, kidney disease, chronic inflammatory diseases, thyroid diseases, stomach ulcers, and infection), a diagnosis of type 2 diabetes; fasting blood glucose levels of less than 180 mg/dl; a 2-hour glucose level of less than 250 mg/dl; no insulin injections; non-smokers; no participation in regular sports programs during the past six months; and the ability to attend the study for three months. Individuals who did not meet these conditions were excluded from the study. Subsequently, ten participants refused to continue their participation for personal reasons and due to disease progression. The remaining 24 subjects were randomly assigned to three groups: low-intensity exercise (8 individuals), high-intensity exercise (8 individuals), and a control group (8 individuals). Written informed consent was obtained from all participants.
Training program
The study began at the sports physiology laboratory at Hakim Sabzevari University for anthropometric and physiological measurements on December 5, 2021. Height, weight, body fat percentage, and waist-hip ratio were measured one week before the beginning of the training program. The following two to three sessions were held in the practice hall to familiarize participants with the training conditions. The training intervention consisted of 12 weeks of concurrent exercise, combining resistance and aerobic activities, performed at two intensity levels: High intensity (resistance at 75–85% of 1-RM and aerobic at 70–85% of maximum heart rate) and low intensity (resistance at 50–75% of 1-RM and aerobic at 50–70% of maximum heart rate). Participants completed three nonconsecutive sessions per week, with each session lasting between 55 and 70 minutes.
The training program of high-intensity concurrent exercises group
The program consisted of 10 minutes of warm-up (jogging, hand and foot movements combined with stretching), followed by 30 minutes of strength training and 10 minutes of cool-down. The stations included bench presses, dumbbell bicep curls, triceps pushdowns, seated leg extensions, leg curls, butterfly exercises, and underhand cable pull-downs. The exercises were performed in accordance with Table 1. The rest interval between each station was set at 120 seconds. After a 15-20 minute rest, 20 minutes of aerobic running training was conducted, featuring 10-12 repetitions for 1 minute at 70-85% of the maximum heart rate, with 30 seconds of active rest between sets at 30-40% of the maximum heart rate (Table 1).
The training program of low-intensity concurrent exercises group
This program included 10 minutes of warm-up, 30 minutes of strength training exercises, and 10 minutes of cool-down. The rest interval between stations was considered also set at 120 seconds. After 20 minutes, aerobic running training at low intensity was performed according to Table 2.
Measurements
Blood samples were collected at two stages: Before and 24 hours after the last session, following a 10-12 hour fasting period. Glycosylated hemoglobin (HbA1c) was measured through an enzymatic colorimetric method with the Nicoard kit (made in Norway, catalog number 1042184), which has a coefficient of variation (CV) of less than 5%. To calculate the body fat percentage, a baseline caliper was used to measure subcutaneous fat in three areas: The thigh, upper pelvic area, and arm triceps, along with the Jackson and Pollock formulas [25]. Maximum oxygen consumption was measured using the Rockport 1-mile (1609 m) Walk Test [21, 26]. Indices of respiratory and pulmonary function were measured with a spirometer (model: CHESTGRAPH HI-701, France). The upper body strength was calculated using the bench press movement and the Brzycki Equation 1
1. 1RM=Weight÷(1.0278–(0.0278×number of repetitions)
Provided that the number of repetitions fell between six and ten repetitions. Upper body muscular strength was computed by the press movement and maximum repetitions to fatigue with 60% of 1RM [27, 28].
To measure the specific strength of the respiratory muscles, a spirometer was used [29]. After a full exhale, the subject was asked to place the mouthpiece in their mouth and breathe in sharply. As the subject inhaled, the piston moved upward, and the highest number displayed was considered the specific strength of the respiratory muscles. This test was repeated three times and the maximum value was calculated. At the same time, in order to monitor the participant’s diet, a 24-hour dietary recall questionnaire, and the three-day dietary records from the beginning and end of the study were used. Food data were analyzed using Nutrition software, version 4.
Statistical methods
Data were described as Mean±SD. The normality of the samples’ distribution was assessed using the Shapiro-Wilk test with Lilliefors correction for small samples, demonstrating a normal distribution for all samples. Treatment effects were analyzed using a two-way ANOVA (IBM SPSS software, version 21, Armonk, VA, USA). A significant interaction effect (group×time) indicated a treatment-dependent difference in the development from pre-test to post-test among the group conditions. Significance was accepted for P≤0.05.
Results
This study showed that 12 weeks of concurrent training at different intensities had significant therapeutic effects on some pulmonary variables, HbA1c values, and body fat percentage in women with type 2 diabetes. Table 3 shows the characteristics of the patients. Table 4 provides an overview of all physiological and functional variables, while Table 5 presents an overview of all respiratory variables.
For several respiratory and physiological parameters, a significant interaction effect (group×time: P<0.05) was found, demonstrating a considerable influence of the respective treatments on the development from the pre-test to the post-test: FEF25, FEF50, FEF2575, FEV1/FVC, HbA1c, and fat percentage (Tables 4 and 5).
There were no significant group effects for other respiratory parameters (P>0.05). For some respiratory, physiological, and functional parameters, significant time effects were observed (P<0.05), indicating a significant change between the pre-test and post-test that was independent of the type of treatment: FVC, FEV, peak expiratory flow (PEF), FEF75, MVV, VO2max, upper body power, and upper body endurance (Tables 4 and 5).
Discussion
This study demonstrated that a 12-week concurrent training program with varying intensities had significant therapeutic effects on certain pulmonary variables, HbA1c levels, and body fat percentage in women with type 2 diabetes. These findings align with those of Silva-Reis et al. who reported that concurrent training enhances lung mechanics and reduces lung inflammation in overweight and obese women [30]. Similarly, Silva-Reis et al. found that concurrent exercise improved lung function, mechanics, and pulmonary immune responses in overweight and stage 1 obese women by elevating levels of the anti-fibrotic protein Klotho while reducing fibrotic IGF-1 [31]. These improvements were attributed to IGF-1, which is recognized as a primary growth factor overproduced in conditions, such as asthma and obesity. In asthma, IGF-1 plays a role in modulating airway inflammation, smooth muscle hyperresponsiveness, and hypertrophy, ultimately affecting lung mechanics [32]. Tunkamnerdthai et al. observed that an eight-week arm swing exercise program (three sessions per week) led to improvements in FEV1, FVC, and MVV while lowering HbA1c levels; however, the FEV1/FVC ratio remained unchanged in their study [20].
Osho et al. also documented significant enhancements in VO2max, FVC, FEV1, and HbA1c levels among 60 individuals with type 2 diabetes aged between 40 and 75 years [26]. Additionally, Chen et al. reported a notable increase in PEF following an eight-week kettlebell training program, indicating improved pulmonary function after exercise [33]. These findings suggest that the respiratory muscles of the participants in this study were effectively trained, resulting in significant improvements in PEF. While prior studies on resistance training in older adults have primarily examined its benefits for individuals with lung injuries or other specific conditions, fewer studies have focused on markers of lung function in this population [34].
Contrary to our findings, Jones and Nzekwu [35] reported no significant changes in lung volume. The results of our study can be explained by the acute enhancements in glucose metabolism that occur immediately after exercise, with these effects lasting for up to 48 hours, as noted by Davis et al. [36].
Poor glucose regulation is linked to microvascular complications and pulmonary respiratory distress [37]. Dyspnea is the leading cause of death in type 2 diabetes after adjusting for other known risk factors [38]. The reduction in mean HbA1c levels observed in this study, which aligns with findings from other research [37, 38] but contrasts with those reported by Sigal et al. [39], may contribute to significant improvements in FEV1/FVC values.
FVC is influenced by factors, such as age, physical activity level, body composition and health, respiratory muscle strength, and lung elasticity [40]. Additionally, the extent of lung volume reduction and airflow limitation correlates with glucose levels and body fat [41]. Hence, the increase in FVC observed in this study following concurrent training may be attributed to enhanced respiratory muscle strength and power, reduced body fat, and lower fasting blood glucose in patients with diabetes. However, the 12-week concurrent training program did not lead to a significant increase in FEV1 among women with type 2 diabetes in either training group. This outcome contrasts with findings from studies conducted by Osho et al. and Beckerman et al. [42]. FEV1, a specific measure of respiratory function, is affected by various factors. A decline in FEV1 indicates reduced lung capacity, airway obstruction, decreased lung reversibility, or, less commonly, insufficient respiratory muscle development. Thus, improving respiratory muscle strength can also enhance FEV1 [40]. As FEV1 serves as an indicator of respiratory muscle strength, it appears that exercises targeting the enhancement of respiratory muscle strength may contribute to increased FEV1 levels [43].
Many studies have reported reduced pulmonary function in diabetic patients, largely due to diminished strength and power of the respiratory muscles. In the present study, while upper and lower body muscle strength and power increased in both the low- and high-intensity training groups, these changes were not statistically significant. Although the strengthened muscles in this study primarily served as supporting muscles for pulmonary function rather than the primary muscles involved in respiration, their long-term strengthening appeared to contribute to improvements in respiratory system function. Additionally, aerobic training may enhance the diaphragm, intercostal, and abdominal muscles while reducing resistance in the respiratory tract. Notably, the specific strength of respiratory muscles, as measured by spirometry, improved in the low-intensity concurrent training group. This underscores the combined role of aerobic and resistance exercises in promoting pulmonary function. Prior research has also shown a positive and significant correlation between cardiovascular fitness (VO2max) and pulmonary function indices, such as FEV1 and FVC [44, 45].
The respiratory and cardiovascular systems collaborate closely to deliver oxygen to cells and regulate the internal environment of the body during both rest and activity. This partnership ensures a balance between ventilation and cardiac function in the gas exchange process that links skeletal muscles to atmospheric air. Any inefficiency in these systems can impair overall body function. When the ventilation-to-blood flow ratio or the ventilation-to-oxygen absorption and removal ratio declines relative to ventilation volume, respiratory muscles consume more energy, increasing the likelihood of premature fatigue [45]. Although the current study observed improvements in maximum oxygen consumption (VO2max) in both training groups, these changes were not statistically significant. Nevertheless, this factor may partially explain the observed enhancements in pulmonary function. This study demonstrated improvements across several key indicators, including respiratory muscle strength and power, body fat percentage, body weight, physical fitness, aerobic capacity, blood glucose levels, and HbA1c among the participants. The variability in results across studies may stem from differences in participant characteristics, such as gender, age, medical history, exercise program type, number and type of movements, intensity and duration of training, and other program-specific factors. It is important to note that respiratory function is influenced by multiple factors, including the nervous system, neuromuscular coordination, respiratory muscle strength, and lung size. Enhancing respiratory muscle strength and reducing airway resistance through exercise has been shown to improve lung function. Exercise-induced bronchial dilation reduces airway resistance, thereby improving ventilation. Additionally, exercises involving significant muscle engagement can increase breathing rate and depth, which, in turn, enhances FVC, oxygen uptake, and oxygen distribution [46].
Conclusion
The findings of this study indicate that concurrent exercise programs of varying intensities can lead to improvements in selected respiratory and physiological parameters, demonstrating potential benefits for women with type 2 diabetes. Both low- and high-intensity training programs showed some positive effects on specific indicators, suggesting their utility in managing the condition. Based on these results, healthcare professionals and specialists are encouraged to promote such exercise programs as part of a comprehensive management plan for patients with type 2 diabetes to enhance their chances of recovery. However, the study also revealed that a 12-week exercise intervention did not result in significant changes in certain respiratory and physical parameters. This suggests that longer training durations, combined with careful management of confounding factors, such as nutritional habits, may yield more pronounced and consistent improvements.
Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Sabzevar University of Medical Sciences, Sabzevar, Iran (Code: IR.MEDSAB.REC.1396.93). Written informed consent was obtained from the participants.
Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.
Authors' contributions
Conceptualization and supervision: Amirhossein Haghighi and Malihe Ebrahimi; Methodology: Malihe Ebrahimi and Amirhossein Haghighi; Investigation: Malihe Ebrahimi, Roya Askari, Amirhossein Haghighi, Mitra khademosharie; Data collection: Malihe Ebrahimi , Data analysis: Amirhossein Haghighi and Mitra khademosharie; Writing–review & editing: All authors.
Conflict of interest
The authors declared no conflict of interest.
Acknowledgments
The authors thank all their colleagues who helped them in carrying out this research project.
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Received: 2024/07/23 | Accepted: 2025/01/4 | Published: 2025/07/13
Received: 2024/07/23 | Accepted: 2025/01/4 | Published: 2025/07/13
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