Comparison of resistance training combined with breathing retraining, or alone, on cardiovascular risk factors, pulmonary function, circulatory parameters, and aerobic capacity in overweight young women: randomized and controlled trial

doi:10.21203/rs.3.rs-4865237/v1

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Comparison of resistance training combined with breathing retraining, or alone, on cardiovascular risk factors, pulmonary function, circulatory parameters, and aerobic capacity in overweight young women: randomized and controlled trial

https://doi.org/10.21203/rs.3.rs-4865237/v1

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Background: To investigate the effects of resistance training with breathing retraining on body composition, pulmonary function, circulatory parameters, and aerobic capacity in overweight young women.

Methods: 24 overweight young females were randomly allocated into the resistance training group (RT) and the resistance training combined with breathing retraining group (RT+B), and performed exercise training for eight weeks, three sessions/week and 60 minutes/session. 12 age and BMI matched but not overweight young females were also recruited as the control group (C). The variables of anthropometric, body composition, pulmonary and circulatory function, aerobic capacity, blood glucose and lipid profile were measured before and after the intervention.

Results: Significant decreases in BMI, total body fat, TG and LDL-c were observed in the two exercise groups (p＜0.05). In both exercise groups, significant increases in VO2max were accompanied by noticeable increases in VC, FVC, MVV, FEV1, PEF and decreases in SBP, DBP, SBP2, cSBP, rAI (p＜0.05). The Group RT+B had significantly higher increases in VO2max, AT, and oxygen pulse level than those of the control and Group RT (p＜0.05).

Conclusions: The combined resistance exercise and breathing retraining appears to be more effective than resistance exercise alone in improving pulmonary function and aerobic capacity in overweight young women.

Resistance training

Breathing retraining

Combination therapy

Cardio-pulmonary fitness

Overweight and obesity has become a serious public health problem worldwide. According to the World Health Organization, by 2025, 1/5 of the world’s population will be obese [1]. Obesity prevalence increased among women, either adults or youth, because women are more prone to fat accumulation than men [2]. A decrease of respiratory strength and endurance has been reported in obese/overweight women, as the increased fat accumulation in chest wall and trunk leads to weakness of respiratory muscle and changes in breathing patterns, resulting in decreased lung ventilation and obesity correlated symptoms such as wheeze, dyspnoea, and orthopnoea [3]. In additional, women with overweight or obese have poor abdominal muscle strength, so they depend much more on thoracic breathing that hampers the effectiveness of ventilation [4].

Several studies have revealed that high body mass index (BMI), metabolic syndrome, and cardiovascular disease are related to lower lung function [5, 6]. European Community Respiratory Health survey of 1631 women aged 28–44 showed that there is a U-shaped associated of lung function with BMI, and obesity is associated with lower forced vital capacity (FVC) and more asthma symptoms [7]. Numerous studies have demonstrated that obese state is accompanied by metabolic dysfunction, hypertension, dyslipidaemias, which shown to increase the incidence of cardiovascular disease [8]. Poor cardiovascular system increases the work of breathing, so obese people always have more ventilatory demands [9]. Therefore, low levels of cardiorespiratory fitness are associated with high risk of cardiovascular risk in obese population.

2019 American College of Cardiology/American Heart Association guideline recommends that weight maintenance should be promoted to reduce cardiovascular risk factors in obese patients, and at least 150 min/wk of moderate-intensity or 75 min/wk of vigorous-intensity exercise should be adhere [10]. Maximal ability to utilize oxygen during graded exercise testing (VO2max) is the gold standard to predict cardiorespiratory fitness and it is determined by the capacity of oxygen delivery and oxygen utilization [11]]. Therefore, any intervention which influence the factors determining the capacity for oxygen delivery and utilization may exert protective effects on cardiorespiratory fitness. Resistance training (RT) can enhance muscle strength and influence resting energy expenditure, so RT is often recommended to obese population for weight loss [12]. It is well established that RT improves cardiovascular risk factors and blood lipid profiles [13]. Previous study with older [14] and overweight men [15] have found that RT plays an important role in reducing LDL-cholesterol, total triacylglycerol, and total cholesterol. However, the role of RT on aerobic capacity is still controversial, as it may improve cycling performance and economy, but not aerobic capacity [16] While other studies showed that RT can increase cardiopulmonary function as shown by improvement of submaximal exercise and increased peak oxygen uptake (VO2peak), resulting of its enhancement of muscle hypertrophy [17]. Whether RT is effective to enhance cardiorespiratory function on obese female need further explore.

Respiratory muscle training has recently become a hot topic in many clinical studies, such as non-specific low back pain and chronic obstructive pulmonary disease which includes inspiratory muscle training (IMT) on manometer and breathing retraining (BR)—diaphragmatic breathing, which focuses on expanding the abdomen in order to breathing deeply [18]. BR can be performed as the Buteyko breathing technique, yoga, and other exercise that manipulates the breathing pattern [19]. Combined of IMT with BR significantly improved respiratory muscle strength, chest wall mobility and respiratory pattern and endurance than single IMT [20]. It is also reported that BR increased the tidal volume and minute ventilation and ad significant improvement in respiratory patterns [21]. Compared to IMT, BR is simple and effective without purchasing of any training instruments, and is also easy for self-administration.

BR has been identified as beneficial to both physical and mental health [22]. BR significantly increased pain thresholds and decreased sympathetic activity, thus reduces negative feelings [23]. A systematic review revealed that BR has positive impacts on lower respiratory rate, heart rate and blood pressure; it also reduces cortisol levels and stress level that measured by Perceived Stress Scale and the Depression Anxiety Stress Scales [24]. Our team has revealed that obesity and depression have a bidirectional connection; obesity, as a psychological stress, can lead to the generation of depressive emotions, and the negative lifestyle habits caused by depressive emotions can also exacerbate the occurrence and development of obesity[25]. As BR is beneficial to regulate cardiovascular risk factors and mental stress, how will it influence obese state and cardiopulmonary fitness still needs further research.

In the literature, there are evidence to support the beneficial effects of RT on respiratory and cardiovascular function, but combined effects of RT and respiratory training in body weight control for women with overweight or obese have not been sufficiently explored. Therefore, with a multi-group experimental design, the purpose of this study was to investigate the effects of RT and RT plus BR on body weight control in overweight young women. We hypothesized that the RT plus BR would produce much significant effects on body composition, pulmonary function, circulatory parameters, and aerobic capacity, compared to those of the RT or non-exercise control groups, in overweight young women.

Participants

Sample size was calculated with a power of 0.8 at α = 0.05 by G*power, and the sample size was estimated to be 12 in each group. 24 overweight young females aged 18–22 volunteered to participate in this study, and they were randomly allocated into the resistance training (Group RT) and the resistance training combined with respiratory training (Group RT + B), 12 age and BMI matched healthy young females were also recruited as the control group (Group C). The study procedures were approved by the Tianjin Sport University Ethical Advisory Committee (TJUS2022-009) and adhered to the declaration of Helsinki. All participants provided written informed consent and answered a health questionnaire before the baseline tests.

All participants were recreationally active, be “overweight” as defined as the percentage of body fat over 30% measured by the Inbody 770 bioimpedance analyser and not participated in regularly exercise training within two weeks. Participants were excluded if they have a history of coagulation/ bleeding disorders, smoking, history of metabolic disease, serious allergy, history of heart disease and taking medicine known to affect glucose regulation or lipid metabolism.

Study design

The experimental protocol consisted of pre-and post-training measurement and an 8-week resistance training (RT) or RT combined with breathing retraining (RT + B). the participants in the Group C remained recreational active, while the participants in Group RT and Group RT + B undertook exercise training. At the baseline and after exercise training, cardiovascular risk biomarkers, pulmonary function, and aerobic capacity were measured in all groups (Fig. 1).

Exercise training protocol

Participants trained three times per week and 60 minutes per session for eight weeks. Training was performed under the supervision of qualified fitness instructors. Before the main training program, participants were familiarised with the training protocol. As seen in Fig. 2, all training is consisted of 5 minutes of warm up prior RT or RT + B, and 5 minutes of cool down post training. Participants in Group RT and Group RT + B undertook resistance training, the difference between two groups was the resting period among each session, participants in Group RT remained still and those in Group RT + B undertook breathing retraining during each interval. During the training, heart rate was monitored every 15 seconds by Polar remote ECG telemetry instrument (Polar, Kajaani, Finland). If dizziness, fatigue, shortness of breath and other symptoms occur during training, immediately reduce the exercise intensity, or stop the exercise in time.

Resistance training programme consists of 5 movements, each session remains 7 minutes and the interval between each session is 3 minutes, and the total training time takes approximately 50 minutes.

Elevated elastic band row: Stretch the shoulder and bend the elbow, pull the elastic band backward in the horizontal direction, straighten the chest and abdomen, shrink the shoulder blade back, and contract the back muscles.

Jackknife sit-up: Lie on the ground, take the waist as the axis, bend and lift the legs at the same time, and touch the feet with both hands.

Plate twist: Sit on the ground, put feet together and lift legs, hands grasp the barbell pieces in front of abdomen, turn left and right with the barbell pieces touch the ground.

Butt lift bridge: Lie on the back with knees bent, stretch hips, and straighten abdomen, stabilize for a moment, and slowly return to the start action.

Balance board: stand upright and put feet on the balance board, keep the body as balanced as possible.

Breath retraining is developed to increase participants’ consciousness of breathing, by shifting from thoracic movement to abdominal movement during the 3 minutes interval time. The training program transit from weightless abdominal breathing in the first week to 5kg weight-bearing abdominal breathing in the last week. The total time of respiratory muscle training lasted for approximately for 15 minutes. The participants lying still on the ground, fitness instructors put barbell pieces on the participant’s abdomen as resistance, and instruct the participants to concentrate on the anterior abdominal wall to exhale through the mouth.

Body composition assessment

Height was measured using a wall-mounted stadiometer (Seca, Hamburg, Germany) to the nearest 0.1 cm and body mass was measured by a beam balance scale (Avery, Birmingham, UK) to 0.01 kg. BMI was calculated as body mass (kg) divided by height squared (m2). Fat content was determined by the Inbody 770 bioimpedance analyser to verify the inclusion criteria of RT and RT + B groups and evaluate the effect of weight losing after the intervention.

Cardiovascular risk biomarkers

Blood samples were taken from the cubital veins at pre-and post-training following an overnight fast, participants were instructed to avoid strenuous exercise prior to the test for 24 hours. Plasma samples were analysed for glucose, total cholesterol (TC), total triacylglycerol (TG), high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), using the enzymatic and colorimetric methods (HORIBA ABX Diagnostics, Northampton, UK).

Pulmonary function

Pulmonary function was evaluated utilizing a spirometer (CHESTGRAPH, HI-101, Japan), the test was conducted during 9:00 am to 11:00 am to limit diurnal variety. All participants were tested by the same researcher. The vital capacity (VC), forced vital capacity (FVC), forced expiratory volume of the first second (FEV1), FEV1/FVC maximal voluntary ventilation (MVV) and peak rate of expiration flow (PEF) were recorded before and after eight weeks of intervention.

Circulatory system measurements

Resting systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), central aortic systolic blood pressure (cSBP), second peak systolic BP (SBP2) and radial augmentation index (rAI) were measured by a digital electronic tensiometer (OMRON-HEM-9000A1, Japan). The OMRON-HEM-9000A1 device is programmed to determine automatically the pressure against the radial artery to obtain the optimal radial arterial waveform, and rAI=(SBP2-DBP)/(SBP-DPB) *100%. The measure was also taken during 9:00 am to 11:00 am in a sitting position to limit diurnal variety. All participants were tested by the same researcher.

Aerobic capacity

VO2max test was carried on a computer-controlled ergometer (Monark 839E, Sweden) and a breath-by-breath analysis system (AEGER Oxygen Analyzer) both at baseline and after the 8-week intervention. The incremental maximal test protocol included a 3-minute warm up at 30W, graded exercise started at the initial workload of 50W and increased by 20W every 2 minute until exhaustion, and a 3-minute recovery time at 30W after the test. Participants were asked to keep a pedalling cycling of 60rpm during the test, when the pedalling cycle was not maintained, the test was stopped. The test stopped when participants reach any two of the following criteria: (1) VO2 reached a plateau; (2) heart rate above 180 beat/min; (3) respiratory exchange ratio (RER) above 1.10; (4) rating of perceived exertion (RPE) scale reached 18. VO2max (ml/kg/min), anaerobic threshold (AT, ml/kg/min), and peak oxygen pulse (ml/bet) were measured and calculated.

Statistical analysis

Data were analysed using the Statistical Package for Social Sciences (SPSS) software version 22.0 for Windows (IBM, New York, USA). Normality of the data was checked using Shapiro Wilk test, if necessary, data were logarithmically transformed before statistical analysis. One-way between group measures ANOVA with a post hoc Bonferroni test was used to judge the differences between groups pre-and post- intervention. The paired t-test was used to judge the differences within groups pre-and post-intervention. Significant was taken at p < 0.05. Results are presented as means ± standard deviation (SD).

Data were present for 31 participants; 5 participants were dropped out due to poor compliance. By the end of the study, 9 in Group C, 12 in Group RT and 10 in Group RT + B. There were no exercise-induced injuries during the intervention period for all participants.

Response to exercise

The mean heart rate during exercise intervention in Group RT + B is significantly lower than Group RT both in exercise session and interval time (p<0.05). When calculated with the maximal heart rate (estimated by 220-age), the total exercise intensity in Group RT and Group RT + B were 67.5% and 63.8%, respectively (Table 1).

Table 1

Heart rate response during exercise training (Mean ± SD)
	Exercise HRmean	Interval HRmean	%HRmax
Group RT	135.2 ± 12.1	109.3 ± 9.7	67.5%
Group RT + B	129.0 ± 12.9	99.7 ± 11.3	63.8%
P value	0.025	<0.01

Data were expressed as mean ± SD.

Body composition

The percentage of body fat was significantly higher in Group RT and Group RT + B compared to that of Group C at the baseline (p<0.05). Both Group RT and Group RT + B obtained significant decreases in BMI and body fat%, compared to baseline (p<0.05). No significant difference was found after exercise training between Group RT and Group RT + B (p>0.05) (Table 2).

Table 2

Body composition analysis among groups (Mean ± SD)
	Group C		Group RT		Group RT + B
	pre	post	pre	post	pre	post
Height (cm)	162.1 ± 5.3	162.1 ± 5.4	162.1 ± 4.9	162.2 ± 4.9	165.9 ± 5.3	165.8 ± 5.1
Body mass (kg)	60.7 ± 5.9	59.9 ± 7.3	60.9 ± 6.9	56.1 ± 6.9	63.7 ± 8.3	59.9 ± 7.7
BMI (kg/m2)	23.1 ± 2.7	22.8 ± 3.1	23.1 ± 1.9	21.3 ± 1.9Ɨ	23.8 ± 3.6	22.4 ± 3.3∆
Body fat %	25.1 ± 2.9	26.9 ± 4.5	31.1 ± 3.4*	28.5 ± 3.4Ɨ	31.6 ± 5.9*	27.2 ± 5.8∆

Data were expressed as mean ± SD. According to ANOVA, *p<0.05 as Group RT and Group RT + B vs. Group C; according to paired t-test, Ɨp<0.05 as pre vs. post in Group RT; ∆p<0.05 as pre vs. post in Group RT + B.

Cardiovascular risk biomarkers

As seen in Fig. 3 (A, D), there were no significant differences in blood glucose and HDL-c levels between pre-and post-training among 3 groups (p>0.05). Figure 3 (B) showed that Group RT and Group RT + B had significantly higher level of serum TC pre-and post-training compared with that of the Group C (p<0.05). Data from Fig. 3 (C, E) revealed that serum TG and LDL-c in Group RT and Group RT + B were significantly higher than that of Group C at the baseline (p<0.05) and no obvious differences after training (p>0.05). Exercise training significantly lower serum TG and LDL-c levels in both Group RT and Group RT + B (p<0.05), with no significant differences in serum TG and LDL-c levels between these two groups (p>0.05)

Pulmonary function

For the intergroup analysis, the only significant difference was that Group RT + B significantly improved MVV after training (p<0.05). Besides, there were no significant intergroup differences in other parameters among 3 groups (p>0.05). Regarding the differences pre-and post-training, there were significant improvements in Group RT (VC = 3.49%, FVC = 7.16%, MVV = 5.74%, FEV1 = 8.68%, PEF = 3.25%, p<0.05) and Group RT + B (VC = 8.38%, FVC = 9.53%, MVV = 13.46%, FEV1 = 12.11%, PEF = 14.69%, p<0.05) after training (Table 3).

Table 3

intra-and intergroup changes of pulmonary function (Mean ± SD)
	Group C		Group RT		Group RT + B
	pre	post	pre	post	pre	post
VC (L)	3.5 ± 0.3	3.5 ± 0.3	3.3 ± 0.6	3.5 ± 0.6ƗƗ	3.4 ± 0.6	3.7 ± 0.5∆∆
FVC(L)	3.4 ± 0.3	3.4 ± 0.3	2.9 ± 0.6	3.1 ± 0.6ƗƗ	2.9 ± 0.6	3.3 ± 0.5∆∆
MVV(L/m)	93.9 ± 7.7	92.9 ± 7.7	91.6 ± 4.8	96.8 ± 5.1ƗƗ	92.4 ± 13.0	104.8 ± 13.1#∆∆
FEV1(L)	3.2 ± 0.3	3.2 ± 0.3	2.7 ± 0.5	2.9 ± 0.6ƗƗ	2.7 ± 0.6	3.1 ± 0.5∆∆
FEV1/FVC	93.9 ± 3.3	93.9 ± 3.8	92.8 ± 3.9	93.5 ± 2.4	92.6 ± 6.8	94.5 ± 1.9
PEF(L/s)	3.7 ± 0.3	3.7 ± 0.4	3.7 ± 0.7	3.8 ± 0.7ƗƗ	3.8 ± 1.4	4.3 ± 1.7∆∆

Data were expressed as mean ± SD. According to ANOVA, #p<0.05 as group RT + B vs. group C post-training. According to paired t-test, ƗƗp<0.01 as pre vs. post in Group RT; ∆∆p<0.01 as pre vs. post in Group RT + B.

Circulation system

The value of SBP, DBP, SBP2, cSBP and AI were significantly elevated in Group RT and Group RT + B at the baseline (p<0.05), and there were no significant differences in the post-training data of the two exercise groups and those of the control group (p>0.05). Regarding the differences between pre-and post-training, there were significant decreases in Group RT (SBP = 6.44%, DBP = 5.67%, SBP2 = 6.11%, cSBP = 6.26%, AI = 17.68%, p<0.05) and Group RT + B (SBP = 11.31%, DBP = 12.27%, SBP2 = 18.78%, cSBP = 14.46%, AI = 24.25%, p<0.05 ) following training (Table 4).

Table 4

intra-and intergroup changes of pulmonary function (Mean ± SD)
	Group C		Group RT		Group RT + B
	pre	post	pre	post	pre	post
SBP (mmHg)	96.9 ± 4.3	97.1 ± 4.5	101.7 ± 5.4##	102.5 ± 6.2ƗƗ	112.3 ± 11.1##	99.6 ± 8.0∆∆
DBP (mmHg)	60.7 ± 6.0	59.7 ± 5.6	67.6 ± 6.9	63.8 ± 6.2ƗƗ	70.1 ± 10.2#	61.5 ± 5.1∆∆
PP (mmHg)	36.2 ± 4.0	37.4 ± 4.7	36.9 ± 4.5	38.8 ± 7.9	42.2 ± 9.5	38.1 ± 4.9
SBP2 (mmHg)	84.9 ± 7.9	79.9 ± 5.1	95.4 ± 6.6#	89.6 ± 5.6ƗƗ	104.9 ± 9.7##	85.2 ± 5.1∆∆
cSBP (mmHg)	94.9 ± 7.6	92.8 ± 10.1	106.5 ± 7.5#	99.8 ± 9.2ƗƗ	108.6 ± 9.5##	92.9 ± 9.8∆∆
rAI (%)	67.3 ± 11.7	70.9 ± 6.3	81.6 ± 6.9##	65.8 ± 11.9ƗƗ	82.6 ± 4.5##	62.6 ± 10.9∆∆

Data were expressed as mean ± SD. According to ANOVA, ##p<0.01 as group RT and group RT + B vs. group C post-training, #p<0.05 as group RT and group RT + B vs. group C post-training. According to paired t-test, ƗƗp<0.01 as pre vs. post in Group RT; ∆∆p<0.01 as pre vs. post in Group RT + B.

Aerobic capacity

As shown in Fig. 4 (A-C), Group RT and Group RT + B had significantly lower VO2max pre- and post-training, compared with those of the control group (P<0.05). However, VO2max was increased by 12.22% in Group RT and 26.61% in Group RT + B after training, while the post-training VO2max of Group RT + B was significantly higher than that of Group RT (P<0.05). There were no any significant differences in AT among the three groups pre-and post-training (p>0.05), excepting a significant improvement (32.67%) in Group RT + B after training (p<0.05). The pre- and post-peak oxygen pulse was significantly lower in the RT and RT + R groups, compared to those of the control group, the significant difference only seen between Group RT and the control group before or after intervention?? (p<0.05). There was a significant improvement (15.34%) in peak oxygen pulse of the Group RT + B after training (p<0.05).

To our knowledge, this is the first interval-based training mode that applied with repeated series of high loads of resistance training separated by recovery period with BR, as to maximize magnitude of training in abdominal muscle. This randomized control study was aimed at evaluating the impacts of this new training mode on respiratory function, circulation function, cardiovascular risk factors and aerobic capacity in overweight female. The main findings supported our hypothesis and showed that RT and RT combined with BR improved respiratory function, lowered peripheral and central blood pressure, regulated cardiovascular risk biomarkers. More importantly, the RT combined with BR program achieved better effects in improving aerobic capacity than RT alone.

Obesity is a chronic inflammation characterized by insulin and leptin resistance caused by fat accumulation in a positive energy balance, which can lead to metabolic complications or related disease [26]. Cardiovascular disease risks are positively correlated with increased BMI and influenced by blood glucose and lipid profile levels [27]. The results of our trail showed that female with higher fat percentage with higher levels of TC, TG, LDL-c, and lower level of HDL-c compared with lower fat percentage participants. Because of the beneficial effect of exercise on health parameters, American association of clinical endocrinologists and American college of endocrinology guidelines recommended physical exercise a non-pharmacological strategy for decreasing cardiovascular risk factors [28]. In our study, after eight weeks of RT or RT combined with BR significantly reduced fat percentage and improved serum lipid profiles in young female. These outcomes were supported by Costa’s study, they also found that exercise is sufficient and effective to beneficially lowered the lipid profiles of women with dyslipidaemia, regardless of their training status [29]. Besides, Moro et al revealed that RT was able to exert positive effect on parameters associated with cardiovascular as LDL-c and TC in older adults [14]. However, Moro’s other study pointed out that six weeks of RT and high intensity interval RT significantly regulated body composition, but they did not observe any change in lipid profiles in healthy participants because of their excellent state [12].

Obesity is independently associated with low pulmonary function, according to the CARDIA (The Coronary Artery Risk Development in Young Adults) study, lung function is negatively associated with BMI [30]. The normal breathing mode includes synchronous movement of the chest and abdominal cavity, to fully expand the lungs and allow maximum gas exchange, and the type of breathing depends on the percentage of work done by the ribs or diaphragm, which is called thoracic breathing and abdominal breathing [31]. The abdominal muscle help accelerate the expiratory flow rate and enhance the inspiratory phase of ventilation. Ma’s study explored the correlation between FEV1/FVC and peak expiratory rate with abdominal strength, and showed that good abdominal strength is positively correlation with respiratory function [32]. Bishop also illustrated that lung inflation evoked an increase in abdominal expiratory muscle activity and the relationship between core strength and pulmonary function [33]. Several studies also pointed out that, with weight loss, the tethering forces between the airway and parenchyma was restore and the long decompression, the respiratory function is improved [34, 35]. This is consistent to our study that overweight female has impaired pulmonary function compared with control group, and after exercise training, both modes significantly increase VC, FVC, MVV, FEV1, and PEF compared to pre-training. During our core strength RT, the intra-abdominal pressure was increased and push the diaphragm upward into the thoracic cage, so that increased the speed of the exhalation as seen elevated PEF and FEV1, and elevated volume of exhalation as seen higher VC, FVC and MVV. This is consistence with Kim’s study, they found there were positive correlation between abdominal muscle strength and peak expiratory flow rate, and help to fix the trunk and reduce the pressure to the spine [36]. Another study showed that a 12-week core strength training improved the effectiveness of pulmonary function [37]. In our study, RT combined with BR significantly improved MVV than control group, this maybe RT combined with BR can modify breathing patterns and activate the diaphragm to a greater extent, thereby enhancing the ability of the ventilator, the RT plus BR program produces better results than that of the RT alone.

Extensive literature revealed elevated blood pressure and hypertension is associated with target organ damage, and is one of the risk factors of cardiovascular disease [38]. Non-invasive central arterial pressure (CAP) monitoring was widespread in the diagnosis and evaluation of clinical hypertension. Aparicio Lucas et al found that compared to brachial artery blood pressure, CAP is more direct and accurate in reflecting blood pressure in heart, brain, and renal target organs, and is an important influencing factor for the occurrence and development of cardiovascular diseases and related complications [39]. Hypertension and obese leads to increase of the CAP because of the increased stiffness, which is reflected by elevated AI [40]. In our study, overweight female with higher percentage of fat had higher peripheral and central blood pressure, as well as higher rAI, than the control group. We used rAI to judge arterial is based on a study by Kohara et al that they proved rAI is a useful and easily obtainable parameter, as it is highly associated with AI (r = 0.822) [41]. Exercise is the first-line strategy for regulating hypertension and results of our study showed eight weeks of RT and RT combined with BR lowered peripheral and central blood pressure and reduced rAI in overweight young female. Izawa’s study also showed better cardiovascular physiological outcomes and health-related quality of life in coronary artery disease women after RT [42]. Even though there were no significant difference between these two-training mode in reducing blood pressure, RT combined with BR have greater magnitude in reducing SBP, DBP, SBP2, cSBP, and AI after training. Our results were consistent to Caminiti’s study that 12 weeks of aerobic plus resistance exercise is more effective in reducing blood pressure and blood pressure variability in hypertension patients than aerobic exercise alone [43].

Vo2max is used to assess cardiac function and peripheral adaptations during graded exercise test [44] Several studies revealed that obesity negatively affects exercise capacity through limited cardiopulmonary fitness [45] In our study, participants in Group RT and Group RT + B had higher level of body fat compared with control group, even they are in similar BMI level, so they had low values of VO2max, AT and oxygen pulse at baseline. Skrpnik’s study pointed out that three months of endurance strength training have positive effect on anthropometric parameters, body composition and aerobic capacity in abdominal obesity women [46]. RT may increase the citrate synthase enzyme and lactate dehydrogenase, so it improves both aerobic and anaerobic performance [47]. Feiereisen et al. observed 16% improvements in VO2max after RT [48] and Volaklis et al. showed 14.5% elevation of VO2max in heart failure patients [49], which is accordance with our study, a 12.22% increase in VO2max after RT. Although confounded by utilization of two exercise modes, comparative studies illustrated that combined RT and aerobic exercise have better effect in improving VO2max than single training alone [50]. Selig et al. showed a 21% of increment of VO2max after 3-month of RT combined with aerobic exercise [51], which is accordance with our study that 26.61% improvement after RT combined with BR. Peak oxygen pulse reflecting the product of stroke volume and arteriovenous oxygen difference; however, only a few studies have focused on the change in oxygen pulse following exercise training. Abernethy et al. compared oxygen pulse in exercise-to-muscle movements and found that circuit (13.07 ml/beat) and supine (8.41 ml/beat) had the highest and lowest oxygen pulse in professional dancer [52]. In our study, even though both modes of exercise beneficially increased VO2max, but only RT combined with BR increased AT and oxygen pulse. This might be related to improved pulmonary function. Choi et al. explored the relationship between VO2peak and respiratory muscle performance and found that FEV1 and other functional markers were significantly correlated with VO2peak [53]. Moawd’s study revealed that respiratory muscle training increased inspiratory and expiratory pressure as well as exercise capacity in obstructive sleep apnea patients [54]. Their results were consistent to our study that eight weeks of RT combined with BR significantly improved MVV in overweight female, as well as improved AT and peak oxygen pulse.

To explore why RT combined with BR have better effect on cardiopulmonary fitness, we monitored the heart rate of participants during exercise intervention. It was found that combination therapy has lower average heart rate than single RT intervention, especially in interval times. The recovery of heart rate after exercise is jointly influenced by the sympathetic and vague nerves (VN) of the heart, and post-exercise heart rate recovery slowly means a decrease in vague nerve activity [55]. Our study found that the rapid recovery of heart rate after exercise caused by BR may also be related to VN activation. Hollstien’s study found that afferent vagal modulate abdominal expiratory muscle activity through regulating pulmonary stretch receptors in airway smooth muscle [56]. When airway wall tensions the receptors discharge and formed a rhythmic discharge pattern which may regulate airway smooth muscle tone, systemic vascular tone, and heart rate. High intensity RT increased the sympathetic function and decreased VN efficiency, causing parasympathetic nerve withdrawal [57]. Moderate aerobic exercise increases the area of myelin sheath, unmyelinated exons, and myelinated fibres of somatic nerve, thereby increasing the tension of the VN [58]. As combined RT with BR might increase the activity of VN, therefore reduce the total intensity of exercise training.

Some limitations of the present study should be considered. The first limitation regards the way to quantify exercise intensity in resistance training and breath retraining period. We only use heart rate to monitor exercise intensity and ignore the exercise energy expenditure as it is thought to be a significant predictor of exercise-induced reduction of fat mass and lipid profiles. And we also not clear how adding breath retraining will affect the exercise and resting energy expenditure. The second limitation is that we did not control the dietary intake of our participants and only asked them to maintain their habitual intake. As diet during exercise intervention plays an important role in weight control. Thus, future research should quantify exercise intensity and energy expenditure in order to assess more precisely of the effects of different exercise modes, as well as make reliable control of participants diet to reduce the impact of diet on heath parameters.

In conclusion, the combined resistance exercise and breathing retraining appears to be more effective than resistance exercise alone in improving pulmonary function and aerobic capacity, and both exercise modalities reduce peripheral and central BP, regulated cardiovascular risk factors and weight losing to a same extent. Better effect might be related increased VN efficiency during breathing retraining in overweight young women.

Acknowledgments

Not applicable

Author contributions

H.C. wrote the manuscript., J.Q.L contributed to data analysis and discussion. Y.L.J, Y.H.Z, S.W, H.D.W and C.Y.D. conducted the experiments. Y.J. reviewed and edited the manuscript. All authors reviewed the manuscript.

Funding

The work presented in this article was supported by a grant from the Tianjin Sports Research Preparation Project of China (Grant No. 23BZ09) and National College Student Innovation and Entrepreneurship Project of China (Grant No. 202110071003).

Availability of data and material

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Ethics approval and consent to participate

The study procedures were approved by the Tianjin Sport University Ethical Advisory Committee (TJUS2022-009) and adhered to the declaration of Helsinki. All participants provided written informed consent and answered a health questionnaire before the baseline tests.

Consent for publication

Not applicable.

Competing Interest

The authors declare that there are no conflicts of interest.

Author details

¹College of Sport Science, Tianjin Normal University, Tianjin, 300387, China.

²Tianjin Key Laboratory of Exercise Physiology and Sports Medicine, Institute of Sport, Exercise & Health, Tianjin University of Sport, Tianjin, 301617, China.

³No.1 Hospital of Baoding, Department of Endocrinology, Baoding, Hebei Province, 071000, China.

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No competing interests reported.

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Comparison of resistance training combined with breathing retraining, or alone, on cardiovascular risk factors, pulmonary function, circulatory parameters, and aerobic capacity in overweight young women: randomized and controlled trial

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Abstract

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Introduction

Materials and methods

Participants

Study design

Exercise training protocol

Body composition assessment

Cardiovascular risk biomarkers

Pulmonary function

Circulatory system measurements

Aerobic capacity

Statistical analysis

Results

Response to exercise

Body composition

Cardiovascular risk biomarkers

Pulmonary function

Circulation system

Aerobic capacity

Discussion

Declarations

References

Additional Declarations

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Version 1