Abstract

Background: Regular physical exercise may improve a variety of physiological and psychological factors in depressive persons. However, there is little experimental evidence to support this assumption for adolescent populations. We conducted a randomized controlled trial to investigate the effect of physical exercise on depressive state, the excretions of stress hormones and physiological fitness variables in adolescent females with depressive symptoms. Methods: Forty-nine female volunteers (aged 18–20 years; mean 18.8 ± 0.7 years) with mild-to-moderate depressive symptoms, as measured by the Centre for Epidemiologic Studies Depression (CES-D) scale, were randomly assigned to either an exercise regimen or usual daily activities for 8 weeks. The subjects were then crossed over to the alternate regimen for an additional 8-week period. The exercise program consisted of five 50-min sessions per week of a group jogging training at a mild intensity. The variables measured were CES-D rating scale, urinary cortisol and epinephrine levels, and cardiorespiratory factors at rest and during exercise endurance test. Results: After the sessions of exercise the CES-D total depressive score showed a significant decrease, whereas no effect was observed after the period of usual daily activities (ANOVA). Twenty-four hour excretions of cortisol and epinephrine in urine were reduced due to the exercise regimen. The training group had a significantly reduced resting heart rate and increased peak oxygen uptake and lung capacity. Conclusions: The findings of this study suggest that a group jogging exercise may be effective in improving depressive state, hormonal response to stress and physiological fitness of adolescent females with depressive symptoms.

Depression is considered a disease that could create a greater worldwide burden than ischaemic heart disease, cerebrovascular disease or tuberculosis.1 In recent years, depression has become increasingly more prevalent among adolescent females on a worldwide scale.2,3 It appears likely that subclinical depression in adolescence is related to depressive episodes, substance abuse, higher levels of neuroticism, academic underachievement, unemployment and early parenthood.4,5 Although depression is a treatable condition, when associated with maladjustment in an emotionally unstable individual it is a likely cause of suicide.6 It is therefore suggested that preventive interventions should be targeted to this group to improve social consequences and reduce the risk of developing major depression.

Physical exercise has been proposed as a treatment for a variety of improved states of physiological and psychological health. A number of experimental and observational studies have been conducted using samples that included clinically depressive patients and members of the general population.7,8 However, most of these studies were limited by inadequacies, such as use of small or heterogeneous groups, poor application of exercise regimens and deficient assessments.8 There is little methodologically sound research that has specifically focused on an adolescent female population. In addition, the endocrinological measurements such as urinary cortisol and catecholamine secretions were widely utilized in the study of evaluating the levels of psychophysical stress and depression. Some previous studies have shown a reduction of these stress hormones in connection with an alleviation of the psychological state.9,10 Furthermore, in general, depressive persons are physically sedentary in their daily life and have reduced physical work capacity compared with healthy individuals.6 This indicates that depressive state is associated with physiological wellbeing and may predispose an individual to diseases related to physical inactivity and limited functional capacity.

Accordingly, we designed a randomized controlled trial to investigate effects of physical exercise on the depressive conditions, neuroendocrine stress hormones and physiological fitness variables in adolescent female volunteers with non-clinical, mild-to-moderate depressive symptoms.

Methods

Subjects

A total of 266 female volunteers, aged 18–20 years, were recruited from students in the university nursing program in Chonburi, Thailand. They participated in a screening examination for depressive symptoms by using the Centre for Epidemiologic Studies Depression (CES-D) rating scale.11 Out of all subjects, cases of depressive state, defined by commonly used cut-off score of 16, were found in 114 subjects. This subgroup returned 4 weeks later so that their symptoms and other health conditions could be re-evaluated and eventually confirmed. Subjects were excluded if they (i) had ever taken any antidepressant medication, (ii) had symptoms or illnesses that limited physical activity, and (iii) had engaged in regular, vigorous sports activity during the prior 6 months. After a strict assessment, 62 of 103 participants presented a mild-to-moderate level of depressive symptoms1214 and had none of the criteria for exclusion. Consequently, 59 subjects agreed to participate in a trial of physical exercise and signed a written informed consent. The protocol was approved by the institutional ethics committee.

Study design

After completion of the baseline assessment, subjects were randomly divided into two groups (group A, n = 28; group B, n = 31) and assigned to a 16-week two-way crossover trial. In the first phase, group A started an 8-week physical exercise program, and group B continued a usual daily routine and served as non-exercising controls. Subjects were then crossed over to the alternate condition for an additional 8-week period. The weekly attendance at the exercise regimen was recorded, and the total number of sessions over the period was calculated. Throughout the length of two experimental periods, subjects were instructed to maintain their usual level of physical activities (with the exception of the above-mentioned exercise period) and requested to keep records of the daily activities.

Outcome measurements

The main outcome measure was subject report of depressive symptoms from the CES-D scale. Subjects were required to complete the scale every 4 weeks during the experimental period. The CES-D is a self-reported measure of the frequency of 20 depressive symptoms during the past week.11 The scale has been shown to have valid and reliable psychometric properties when used for adolescents.2,5 The score of this 20-item self-reported scale ranges from 0 to 60, and the depressive level is considered to advance with increasing scores. A cut-off score of 16 has been used in adults to define cases of depressive state, yet use of this definition has yielded estimated prevalence of adolescent depression of more than 50%.1416 Roberts et al. suggested a cutoff of 24 for adolescent CES-D scores on the basis of improved ability to detect DSM-defined depression.12 Rushton et al. created three levels of provability of depression: minimum (0–15), mild (16–23) and moderate/severe (≥24).13 Further, Garrison et al. proposed a cut-off score of 30 in adolescents to indicate probable case of major depression.14 From these reports, we tentatively categorized a mild-to-moderate depressive symptom as score of 16–29 for the present analysis.

Twenty-four hour urinary secretions of cortisol and epinephrine were measured to assess psychophysical stress conditions. Cortisol secretion was collected from the total urine for 24 h. The calculations were performed using an automatic reagent dispenser and determined by radioimmunoassay (Cobra auto-gamma model; Packard Bio Science Co., France). Urine epinephrine was collected for a 24-h period in 10 ml of 6 N HCl, unless processed at once. The biochemical assays were performed with liquid chromatography, and the value was determined using a spectrofluorometer (model FP-777; Jasco Co., USA). The urine epinephrine and urine cortisol specimens of each subject were assayed separately in a laboratory. Pulmonary functional and exercise endurance testing were carried out to investigate training-induced improvements in physiological fitness factors. The lung capacity was measured with a spirometer. The endurance test was performed on a bicycle ergometer (MONARD 818E, DIN 32932; Klassea, Sweden) by the multistage YMCA submaximal exercise test protocol. The heart rates were measured when the subjects were seated at rest for 5 min and during the last minute of each incremental stage of exercise. Peak oxygen uptake was estimated on the basis of the heart rate increments to workloads.

The measurements were performed at the baseline and at the end of the representative exercise and usual activity periods of the trial. Exceptions were made for the premenstrual period and for 2 or 3 days after the initiation of menstruation.

Intervention

Group jogging was used as the major physical exercise. The subjects were encouraged to join the exercise class, which consisted of 50-min sessions for 5 days per week for 8 weeks. Each session began with a 5- to 10-min warm-up, continued with about 30 min of group-based jogging exercise, and ended with a 5- to 10-min cool-down. The exercise class was not strictly supervised, rather, each subject jogged at her own speed. However, each session was attended by physical fitness instructors who assisted the subjects and ensured that proper exercise intensity was maintained. The intensity was adjusted to maintain a constant heart rate of less than 50% of the maximal heart rate reserve, which was calculated by using Karvonen's formula.17

Statistical analyses

All statistical analyses were performed using the SPSS statistical package 12.0 for Windows (SPSS Software, Inc., Chicago, IL, USA). Repeated measures ANOVA followed by the Bonferroni correction for multiple comparisons was applied for normally distributed parameters, and the Wilcoxon test, for non-parametric parameters. An exploratory factor analysis for the items of the CES-D scale was conducted to investigate what common components of the scale more effectively respond to physical exercise treatment. Data are presented as mean ± SEM. The null hypothesis was rejected at P < 0.05 as the level of significance.

Results

Of the 59 subjects who joined the present trial, five did not complete the training regimen; three dropped out due to lack of motivation and two attended less than three sessions per week. In addition, five subjects who could not maintain the usual level of physical activity constant in their non-exercising period were also excluded. Consequently, data analyses were performed on the 49 subjects (group A, n = 21; group B, n = 28). The average ages of the group A and the group B were 18.7 ± 0.2 and 18.8 ± 0.1 years, respectively. Comparisons of the groups at baseline revealed no significant differences as for CES-D depressive score (group A, 20.1 ± 0.9; group B, 18.8 ± 0.7). In the course of the 40 sessions, the subjects in group A exercised an average of 31.3 ± 0.6 sessions, and those in group B, 29.5 ± 0.7 sessions.

For the CES-D scale, measuring psychological effects, among subjects in the group A (training first) the total score decreased as the results of training (P = 0.003) (figure 1). During the subsequent daily activity phase, it gradually increased but was still significantly lower than baseline value (P = 0.037). The same result after training was also observed in group B (P = 0.008). No significant changes were observed after the phase of usual daily routine. An itemized comparison of the 20 subscale items of CES-D scale between prior and after the training regimen was conducted (figure 2). A significant decrease in the score was found for eight items: item 3, ‘I could not shake off the blues’, item 6, ‘I felt depressed’, item 10, ‘I felt fearful’, item 11, ‘My sleep was restless’, item 14, ‘I felt lonely’, item 15, ‘People are unfriendly’, item 17, ‘I had a crying spell’ and item 18, ‘I felt sad’. Table 1 shows the factor pattern matrix when exploratory factor analysis was applied to the correlation matrix from the CES-D subscale items in the original 266 female volunteers. The four common factors of ‘depression affect (F1)’, ‘positive affect (F2)’, ‘relation with others (F3)’ and ‘somatic symptoms (F4)’ were interpreted. The eight items that had significantly decreased after training were components in the factor of depressive affect (six items) and of relation with others (two items).

Figure 1

Changes in the total scores of CES-D scale across the screening and 16 weeks of experimental periods by groups. Data are expressed as mean ± SEM. *P < 0.05, **P < 0.01 compared with baseline. †P < 0.05 compared with the end of the first phase of experiment

Figure 1

Changes in the total scores of CES-D scale across the screening and 16 weeks of experimental periods by groups. Data are expressed as mean ± SEM. *P < 0.05, **P < 0.01 compared with baseline. †P < 0.05 compared with the end of the first phase of experiment

Figure 2

An itemized comparison of the 20 subscale items of CES-D scale between baseline and after the exercise training in both groups of subjects. Data are expressed as mean ± SEM. *P < 0.05, **P < 0.01 compared with baseline

Figure 2

An itemized comparison of the 20 subscale items of CES-D scale between baseline and after the exercise training in both groups of subjects. Data are expressed as mean ± SEM. *P < 0.05, **P < 0.01 compared with baseline

Table 1

The result of exploratory factor analysis for 20 items CES-D scale in 266 adolescent female volunteers

No.
 
Contents
 
F1
 
F2
 
F3
 
F4
 
Communality
 
I had trouble keeping my mind on what I was doing 0.659 0.084 0.130 −0.197 0.497 
I felt depressed 0.544 0.389 0.240 0.245 0.565 
I felt that I could not shake off the blues 0.501 0.169 0.199 0.209 0.363 
20 I could not get going 0.491 0.397 0.272 0.165 0.500 
10 I felt fearful 0.489 0.331 0.139 0.173 0.398 
I felt that everything I did was an effort 0.442 0.121 0.274 0.171 0.315 
I thought my life had been a failure 0.442 0.406 0.258 0.028 0.428 
14 I felt lonely 0.415 0.336 0.367 0.258 0.486 
I was bothered by things that usually don't bother me 0.401 0.087 0.266 0.218 0.287 
11 My sleep was restless 0.363 0.126 0.045 0.276 0.226 
17 I had crying spells 0.341 0.107 0.115 0.267 0.212 
12 I was happy 0.282 0.645 0.104 0.169 0.535 
16 I enjoyed life 0.167 0.587 0.254 0.138 0.437 
I felt that I was just as good as other people 0.118 0.571 0.154 0.276 0.341 
I felt hopeful about the future 0.054 0.429 0.099 −0.088 0.205 
15 People were unfriendly 0.187 0.222 0.712 0.035 0.593 
19 I felt that people disliked me 0.273 0.096 0.659 0.097 0.527 
18 I felt sad 0.421 0.403 0.451 0.268 0.615 
I did not feel like eating; my appetite was poor 0.065 −0.138 0.012 0.535 0.310 
13 I talked less than usual 0.170 0.219 0.245 0.408 0.303 
No.
 
Contents
 
F1
 
F2
 
F3
 
F4
 
Communality
 
I had trouble keeping my mind on what I was doing 0.659 0.084 0.130 −0.197 0.497 
I felt depressed 0.544 0.389 0.240 0.245 0.565 
I felt that I could not shake off the blues 0.501 0.169 0.199 0.209 0.363 
20 I could not get going 0.491 0.397 0.272 0.165 0.500 
10 I felt fearful 0.489 0.331 0.139 0.173 0.398 
I felt that everything I did was an effort 0.442 0.121 0.274 0.171 0.315 
I thought my life had been a failure 0.442 0.406 0.258 0.028 0.428 
14 I felt lonely 0.415 0.336 0.367 0.258 0.486 
I was bothered by things that usually don't bother me 0.401 0.087 0.266 0.218 0.287 
11 My sleep was restless 0.363 0.126 0.045 0.276 0.226 
17 I had crying spells 0.341 0.107 0.115 0.267 0.212 
12 I was happy 0.282 0.645 0.104 0.169 0.535 
16 I enjoyed life 0.167 0.587 0.254 0.138 0.437 
I felt that I was just as good as other people 0.118 0.571 0.154 0.276 0.341 
I felt hopeful about the future 0.054 0.429 0.099 −0.088 0.205 
15 People were unfriendly 0.187 0.222 0.712 0.035 0.593 
19 I felt that people disliked me 0.273 0.096 0.659 0.097 0.527 
18 I felt sad 0.421 0.403 0.451 0.268 0.615 
I did not feel like eating; my appetite was poor 0.065 −0.138 0.012 0.535 0.310 
13 I talked less than usual 0.170 0.219 0.245 0.408 0.303 

Exploratory factor analysis based on principal factor analysis and varimax rotation was conducted

Table 2 shows measured endocrinological, cardiorespiratory and exercise testing data obtained at the baseline study and following the training and daily activity phases. Compared with the baseline, 24-h urinary cortisol (P = 0.003) and epinephrine excretions (P = 0.031) for the group A were significantly reduced as a result of training. These hormonal excretions for the group B did not change after the usual daily routine, but they were significantly lower after the training period (cortisol, P = 0.012; epinephrine, P = 0.040). Following the exercise training, both groups of subjects had a lower heart rate at rest when compared with values after the daily activity phase and at baseline. In addition, training-induced improvements in cardiorespiratory fitness were significant for both groups, as indicated by an increase of lung capacity and estimated peak oxygen uptake, and a higher level of workload during exercise test. After the daily activity phase, none of the data differed significantly from baseline values. Mean body weight did not alter significantly throughout the experimental period.

Table 2

Endocrinological, cardiorespiratory and exercise testing data for both groups during two experiment periods

Variable Group A (n = 21)   Group B (n = 28)   
 Training first
 
  Daily activity first
 
  

 
Baseline
 
Training
 
Daily activity
 
Baseline
 
Daily activity
 
Training
 
Endocrinogical measurements       
    Cortisol (µg/day) 93.6 (7.5) 61.8 (8.0)** 74.4 (6.9)* 84.6 (6.4) 82.3 (10.3) 57.0 (8.5)* 
    Epinephrine (µg/day) 5.92 (0.36) 4.32 (0.28)* 4.85 (0.43) 5.31 (0.34) 6.17 (0.39) 4.14 (0.27)* 
Physiological fitness factors       
    Body weight (kg) 51.6 (2.6) 51.2 (2.4) 50.9 (2.5) 50.4 (0.9) 50.3 (1.0) 49.6 (1.0) 
    Peak VO2 (ml/kg/min) 33.6 (1.4) 38.1 (1.2)** 34.3 (1.4) 36.7 (1.5) 34.3 (0.8)†† 38.9 (0.9)* 
    Workload (watts) 116.5 (8.7) 131.6 (5.8)** 117.7 (6.4) 120.9 (7.2) 116.3 (4.9)†† 136.1 (5.0)* 
    Lung capacity (l) 1.76 (0.09) 2.00 (0.09)** 1.97 (0.08) 1.81 (0.06) 1.80 (0.07) 2.02 (0.06)* 
    Heart rates (beats/min) 81.7 (2.1) 78.7 (2.6)** 82.1 (2.2) 80.1 (2.4) 81.2 (1.7)†† 77.5 (1.5)** 
Variable Group A (n = 21)   Group B (n = 28)   
 Training first
 
  Daily activity first
 
  

 
Baseline
 
Training
 
Daily activity
 
Baseline
 
Daily activity
 
Training
 
Endocrinogical measurements       
    Cortisol (µg/day) 93.6 (7.5) 61.8 (8.0)** 74.4 (6.9)* 84.6 (6.4) 82.3 (10.3) 57.0 (8.5)* 
    Epinephrine (µg/day) 5.92 (0.36) 4.32 (0.28)* 4.85 (0.43) 5.31 (0.34) 6.17 (0.39) 4.14 (0.27)* 
Physiological fitness factors       
    Body weight (kg) 51.6 (2.6) 51.2 (2.4) 50.9 (2.5) 50.4 (0.9) 50.3 (1.0) 49.6 (1.0) 
    Peak VO2 (ml/kg/min) 33.6 (1.4) 38.1 (1.2)** 34.3 (1.4) 36.7 (1.5) 34.3 (0.8)†† 38.9 (0.9)* 
    Workload (watts) 116.5 (8.7) 131.6 (5.8)** 117.7 (6.4) 120.9 (7.2) 116.3 (4.9)†† 136.1 (5.0)* 
    Lung capacity (l) 1.76 (0.09) 2.00 (0.09)** 1.97 (0.08) 1.81 (0.06) 1.80 (0.07) 2.02 (0.06)* 
    Heart rates (beats/min) 81.7 (2.1) 78.7 (2.6)** 82.1 (2.2) 80.1 (2.4) 81.2 (1.7)†† 77.5 (1.5)** 

Values are expressed as mean (SEM)

VO2 = oxygen uptake.

*

P < 0.05,

**

P < 0.01 compared with baseline;

P < 0.05,

††

P < 0.01 compared with the end of training period

Discussion

We designed a randomized controlled trial of physical exercise among adolescent female volunteers with mild-to-moderate depressive symptoms. The results have demonstrated that a mild level of group jogging exercise significantly alleviates the depressive state and reduces the volumes of urine cortisol and epinephrine excretions, as well as improving physiological fitness conditions. These findings would lend support to the assumption that regular physical exercise can promote a variety of psychological and physiological conditions and may be beneficial in the primary care of adolescent females with depressive symptoms.

It has been shown that most adults who experience recurrent depression have an initial depressive episode as teenagers,18,19 suggesting that adolescence is an important developmental period in which to intervene. Recent studies on the treatment of depression in youth provide evidence supporting the efficacy of medication20 and psychotherapy.21,22 The effect of exercise on depression has been the subject of research for several decades and the available literature is increasing. However, there is little experimental research that has specifically focused on a sample of adolescent female population. In addition, some critics have noted that use of well-controlled and reliable research methods is largely lacking.7 The present study used a randomized control group by manipulating of the screening examination and based on a crossover design. We applied a counterbalancing technique to ensure that the subjects in different groups were drawn into the same condition. This technique can help prevent possible errors that could potentially occur at any period of the randomized controlled trial and come from carryover effects. Therefore, with the process of counterbalancing and the design itself, the protocol employed in this study could be considered empirically a validated treatment that prevailed reliable and confident results.23

The present study demonstrated a significant decrease in the CES-D total depressive score after the sessions of physical exercise. In addition, the results from an exploratory factor analysis in the CES-D 20 items revealed that physical exercise contributed to lowering the scores in items from common components of ‘depression affect’ and ‘relation with others’ but not in ‘positive affect’ and ‘somatic symptoms’. The lack or loss of social relationships may be a distinctive feature of depression. Early studies emphasized that interpersonal problem plays a major role in the development of depression.24 Furthermore, the cognitive behavioural change that is experienced with exercise has been proposed as a psychological mechanism for its antidepressant effects.25 In this regard, a previous report has noted minimal changes in the psychological variables for individuals exercising alone rather than in a group format,26 suggesting the potential importance of the social aspects of exercise on psychological outcomes. For the current study, it is possible that a group-based exercise program could provide a social relationship that would provide support among the participants, enhancing the motivation and adherence to the program and possibly contributing to relatively high rates of participation. The psychological benefits from exercise are likely to be mediated not only by exercise itself but also by a variety of sources. Other factors such as increased self-efficacy, mastery and distraction associated with participating in physical activity, may be responsible for alleviating symptoms of depression.

Another important result of our study is the significant reduction in the 24-h urine cortisol and epinephrine secretions after the exercise regimen. The concentration of urine epinephrine has been used as an indicator of sympathetic nerve activity in the study of psychophysical stress and depression.27,28 It has been shown that increased depressive mood state is associated with stressful events, which influence the relationship between autonomic nervous system, endocrine system and immune system.8 Physical exercise appears to reduce urine epinephrine as a result of the attenuation of sympathetic nervous tension. In our results, this assumption might be supported by the reduction in the resting heart rate observed after training, indicating a decrease of the sympathetically mediated cardiovascular response to psychophysical stress. Such neuroendocrine action has been considered a plausible mechanism to explain the effects of exercise on mood and depression.28 Likewise, the urine cortisol concentration was lowered significantly from its level at baseline. This result is consistent with those of investigators who have demonstrated a reduction of cortisol secretion accompanying an alleviation of the psychological state.9,10,29 Hypothalamic-pituitary-adrenal (HPA) activation produces elevations of cortisol by the pituitary gland, which secretes the adrenocorticotropic hormone, which in turn, has an effect on the adrenal cortex, releasing corticosteroids. A previous report suggests that physical exercise may reduce cortisol concentrations as a tranquilizing effect of exercise.30 Although the mechanisms mediating the beneficial effects of exercise on a depressive status are still not clear, the reduction in the subject's neuromuscular hyperactivity in the HPA axis may play a role in some part of the antidepressant effects of regular exercise.

After exercise, the participants did increase their levels of physiological fitness, as indexed by an increase of peak oxygen uptake or improved performance on the cycle ergometer. It has been demonstrated that depressive persons have significantly lower physical work capacity than individuals from the general population and that the reduced fitness levels are mainly due to their poor physical activity in daily life.6 This evidence suggests that depressive state is associated with physiological wellbeing and may predispose an individual to diseases related to physical inactivity and limited functional capacity. In fact, most epidemiological studies addressing this issue have revealed that depression may lead to the development of cardiovascular disease through its association with the metabolic syndrome.31,32 Therefore, it is possible that physical exercise can be efficacious in reducing the risk of such diseases as well as in promoting psychological health by an increase of daily physical activity and improvements in cardiorespiratory function.

Some limitations of the present study should be taken into consideration. First, the study is limited by the inability to use a structured psychiatric interview to follow-up the adolescents that were identified by CES-D as having depressive symptoms. The CES-D self-reporting scale is a questionnaire widely used as a screening tool, especially in primary care and outpatient settings, but it represents symptoms during the past week and may include more transient or temporary symptoms than other measures. However, at least in this screening procedure, we assessed depressive state of subjects twice with an interval of 4 weeks so as to carefully identify a sample with depressive symptoms. Secondly, five subjects from the group that received exercise training first were allowed to participate in a physical exercise class again during the period when no exercise was scheduled. Because of the strict criteria applied to this study, these subjects were excluded from the data analysis despite their high level of adherence to the program. This might influence some of the results from this group obtained after the training. Thirdly, the study sample was adolescent females with non-clinical, mild-to-moderate levels of depression, and it is thus possible that the results obtained may not be transferable to other populations with differences in age, severity of depression, and social and cultural contexts.

In conclusion, depression is a condition that occurs throughout the general population, being especially prevalent among adolescent females, and may extend to a large range of outcomes with negative consequences for health. The present results have demonstrated that group-based physical exercise program, which can increase daily physical activity or social relationships in adolescent female, improve not only the physiological fitness levels but also the depressive state and the psychophysical stress condition. Therefore, regular physical exercise is concluded to have a variety of benefits that may help promote physiological and psychological wellbeing in adolescent females with depressive symptoms.

Key points

  • Does regular physical exercise improve physiological and psychological factors in adolescent females with depressive symptoms?

  • A group-based jogging program increased the daily physical activity or social relationships among the participants.

  • Physical exercise for 8 weeks reduced depressive state and urine cortisol and epinephrine excretions, and increased cardiorespiratory functions.

  • Regular physical exercise may have a variety of benefits of promoting physiological and psychological wellbeing in adolescent females.

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