TITLE: Effects of yoga exercise on maximum oxygen uptake, cortisol level, and
creatine kinase myocardial bond activity in female patients with skeletal muscle pain
syndrome

  ABSTRACT:
[Purpose] This study analyzed the effects of yoga exercise on maximum oxygen uptake,
cortisol level, and creatine kinase myocardial bond activity in female patients with
skeletal muscle pain syndrome. [Subjects] The subjects were 24 female patients with
skeletal muscle pain syndrome. [Methods] The subjects were divided into 2 groups: a yoga
exercise group (n = 12) and a non-exercise control group
(n = 12). Body composition, maximum oxygen uptake, cortisol level, and
creatine kinase myocardial bond activity were measured before and after a 12-week yoga
exercise program. [Results] After the 12-week yoga exercise program, the exercise group
exhibited slightly higher maximum oxygen uptake and creatine kinase myocardial bond
activity than the control group, but the differences were not statistically significant.
In addition, the exercise group exhibited a significant decrease in cortisol level.
[Conclusion] Regular and continuous aerobic exercise such as yoga improves body
composition, maximum oxygen uptake, cortisol level, and creatine kinase myocardial bond
activity in female patients with skeletal muscle pain syndrome.

BODY.INTRODUCTION:
Exercise is well known to facilitate metabolic functions in the human body and benefit
physical health by preventing disease, controlling weight, and maintaining homeostasis1). One important physical change caused by
regular exercise is an increase in red blood cells and consequently hemoglobin; this
regulates the balance between the oxygen transfer system and requirements in the peripheral
blood and improves homeostasis and the body's ability to remove wastes such as carbonic acid
gas from tissues2). The American Heart
Association3) reports that a lack of
exercise is one of the main factors of heart disease (along with high blood pressure,
hyperlipidemia, and smoking) and recommends regular exercise to treat and prevent
heart-related disease4). Despite this
emphasis on regular exercise for health promotion, contemporary society does not engage in
sufficient exercise; moreover, because of inappropriate exercise methods, they are
vulnerable to health deterioration and disease5).  In recent years, much attention has been given to preventing the reduction of women's
physiologic motor ability. Thus, campaigns for effective exercise have been widely promoted,
resulting in a clear trend of voluntary participation in exercise programs. In this regard,
many attempts have been made to develop appropriate exercise programs to improve women's
physiologic abilities1). Previous studies
on the effects of yoga have focused on social science research, targeting subjects such as
the elderly or patients with some diseases; meanwhile, few studies have been conducted on
its physiologic effects, i.e., functional improvement in women's physical bodies6,7,8,9).  Through the relaxation and contraction of various body parts, yoga helps correct the
positions of the skeleton and internal organs, reduce pain in patients with chronic back
pain, increase aerobic capacity10,11,12),
and relieve stress9, 13,14,15,16). In addition, it is
conducive to functional improvement in blood pressure and muscles and joints in the
elderly17, 18). In particular, Kang19) reports that continuous yoga exercise for more than one year is
effective for promoting health in women, improving heart disease, and managing obesity,
which can develop into other diseases. In addition, yoga can minimize reactive oxygen
species generation, because it improves aerobic capacity and positively influences stress
hormones and inflammatory markers10).  However, although yoga has been classified as an aerobic exercise that improves aerobic
capability, its intensity is physiologically lower than the lactate threshold; thus, it can
be classified as a low-intensity exercise. Accordingly, high-intensity exercise over the
lactate threshold should be conducted to improve maximum oxygen uptake (VO2max).
However, it is doubtful that yoga can improve aerobic capability, because it is considered a
low-intensity exercise.  In addition, as patients with musculoskeletal disease are characterized by a high reaction
rate with respect to muscle fatigue, inflammatory marker activity, and stress, they have
difficulties performing exercise as they experience more oxidative stress during
exercise20, 21). The main effects of yoga are thought to be pain reduction in
patients with musculoskeletal disease, functional improvement in muscles/joints, and stress
relief.  Accordingly, this study evaluated the effects of yoga exercise 3 times per week for 12
weeks on cardiovascular endurance capability, cortisol level, and inflammatory markers
(i.e., creatine kinase myocardial bond [CK-MB]) in women in their twenties with shoulder
pain.

BODY.SUBJECTS AND METHODS:
This study involved 24 women in their twenties with shoulder pain. The subjects were
divided into 2 equal groups to ensure biologic homogeneity: the exercise group
(n = 12) and non-exercise control group (n = 12). All
subjects provided written informed consent prior to participation, and ethical approval was
granted by our Institutional Human Research Committee.  Body composition was measured prior to the experiment by using Inbody 720 (Biospace,
Korea). The subjects subsequently engaged in preliminary exercise for one week to adapt to
the yoga program application. The exercise consisted of a 5-min warm-up, 40 min of exercise,
and a 5-min cool-down for a total of 50 min. The subjects engaged in this yoga program 3
times per week for 12 weeks. VO2max (Cpet-Cosmed, Italy), cortisol level (Kodak,
USA), and CK-MB (Kodak, USA) were measured 6 times prior to the experiment and throughout
the 12-week yoga program in all subjects.  The yoga exercise group was taught and practiced modified hatha yoga 40 minutes per session
3 times per week on nonconsecutive days for 12 weeks. The yoga exercise program offers the
greatest health benefits by enabling each subject to improve their strength, flexibility,
and balance. All sessions emphasized the proper use of aligned postures and breathing
techniques through the use of large muscle movements.  All data are presented as mean ± SD. All statistical analyses were completed using SPSS
version 21.0 for Windows (SPSS Inc., Chicago, IL, USA). All statistical tests used an α
level set at p < 0.05. This intervention trial was designed to compare pre- and
post-intervention variables. Changes from baseline to the end of the intervention within and
between groups were determined using paired t-tests and independent
t-tests, respectively.

BODY.RESULTS:
The demographic characteristics of the study subjects are shown Table 1Table 1.Demographic characteristics of the study subjectsAge (years)Height (cm)Weight (kg)% Body fat (%)Yoga exercise (n = 12)22.1 ± 2.9159.4 ± 14.650.9 ± 3.919.3 ± 1.2Control (n = 12)22.6 ± 0.9161.5 ± 4.349.2 ± 4.519.2 ± 1.1. Changes in VO2max in both groups after the 12-week yoga program
are shown in Table 2Table 2.Changes in maximum oxygen uptake after 12 weeksPre-testPost-testYoga exercise (n = 12)48.14 ± 7.0648.71 ± 6.47Control (n = 12)44.86 ± 7.1545.57 ± 6.60. Mean VO2max in the control group increased from
44.86 mL·kg−1·min−1 before the intervention to
45.57 mL·kg−1·min−1 after the intervention; this change was not
statistically significant. Mean VO2max in the exercise group increased from
48.14 mL·kg−1·min−1 before the intervention to
48.71 mL·kg−1·min−1 after the intervention; this change also was not
statistically significant.  The control group had higher cortisol levels at all stages (i.e., prior to exercise,
immediately after exercise, and after a 30-min rest), while the exercise group had lower
cortisol levels at all stages (Table
3Table 3.Changes in cortisol hormone after 12 weeksPre-testPost-testYoga exercise (n = 12)8.90 ± 0.698.11 ± 0.55*Control (n = 12)8.38 ± 1.029.17 ± 1.15**p < 0.05). The control group had higher CK-MB activity at all stages, while the
exercise group had lower CK-MB activity at all stages (Table 4Table 4.Changes in CK-MB after 12 weeksPre-interventionPost- interventionYoga exercise (n = 12)0.63 ± 0.140.71 ± 0.20Control (n = 12)0.57 ± 0.170.92 ± 0.41).

BODY.DISCUSSION:
In the present study, women in their twenties with musculoskeletal disease were divided
into an exercise group and a non-exercise control group in order to identify the effects of
yoga exercise on aerobic exercise capability, cortisol level, inflammatory markers (i.e.,
CK-MB).  The results show that the yoga program had no significant effect on subjects'
VO2max. Cardiac output (Q = stroke volume × heart rate) and arteriovenous
oxygen difference must be increased in order to improve VO2max. However, the
subjects had musculoskeletal disease and no prior experience with yoga, which made it
difficult for them to learn the yoga positions quickly. Therefore, they had limited ability
to increase their cardiac output at the beginning of the program. Moreover, the intensity
and period of the yoga program did not significantly impact subjects' arteriovenous oxygen
difference.  Cortisol, a stress hormone, can facilitate decomposition of free fatty acids from adipose
tissue to activate the use of fat, thereby helping the body cope with stress, such as
intense exercise; it is also used as a marker of immune function inhibition. The blood
concentration of cortisol increases when performing moderate-intensity exercise. The normal
blood concentration of cortisol can play a role in helping the body cope with stress.
However, high blood concentrations can damage tissue, negatively affecting nitrogen
equilibrium in the body and leading to diminished immunity22).  In this study, there was no significant difference in the blood concentration of cortisol
between groups. However, in the control group, the cortisol level increased significantly (p
< 0.05) after the program, whereas in the exercise group, it decreased significantly (p
< 0.05). Furthermore, the control group showed the highest concentration during rest
time, whereas the exercise group showed the highest concentration immediately after
exercise. This result is consistent with a previous study; it can be attributed to a
reaction mechanism against small-muscle damage caused by stress and an increase in stress
caused by exercise in patients with musculoskeletal disease22, 23).  It is important to note that cortisol concentration decreased after the yoga program in the
exercise group in this study; this was due to the subjects' adaptation to the program and is
concordant the results of a previous study in which the increase in cortisol in response to
stress in the training group was small22, 23).  CK-MB activity can increase as a result of damage to muscle fiber membranes, which is
useful for the early diagnosis and treatment of acute myocardial infarction. The increase in
CK-MB activity is characterized by sensitive reactions to even minimal damage to the
heart24).  There was no significant difference in CK-MB activity between groups. However, in the
control group, CK-MB activity was slightly higher in the control group than in the exercise
group after the intervention.  This result is consistent with that of a previous study in which adaptation to exercise was
shown to reduce the increase in CK-MB activity. This result indicates the yoga program
effectively decreased inflammatory markers. In particular, the yoga program effectively
lowered stress caused by exercise.  Therefore, although the yoga exercise did not significantly influence VO2max, it
improved flexibility and muscle/joint function, reduced pain, decreased stress hormone
level, and mitigated muscle damage.

Question: Compared to control group what was the result of exercise group on cortisol levels - after a 30-min rest?
Evidence: Mean VO2max in the control group increased from
44.86 mL·kg−1·min−1 before the intervention to
45.57 mL·kg−1·min−1 after the intervention; this change was not
statistically significant. 
Answer: significantly decreased