Effect of six weeks yoga training on weight loss following step test, respiratory pressures, handgrip strength and handgrip endurance in young healthy subjects

Abstract

The present study was designed to test whether yoga training of six weeks duration modulates sweating response to dynamic exercise and improves respiratory pressures, handgrip strength and handgrip endurance. Out of 46 healthy subjects (30 males and 16 females, aged 17-20 yr), 23 motivated subjects (15 male and 8 female) were given yoga training and the remaining 23 subjects served as controls. Weight loss following Harvard step test (an index of sweat loss), maximum inspiratory pressure, maximum expiratory pressure, 40 mm endurance, handgrip strength and handgrip endurance were determined before and after the six week study period. In the yoga group, weight loss in response to Harvard step test was 64 +/- 30 g after yoga training as compared to 161 +/- 133 g before the training and the difference was significant (n = 15 male subjects, P < 0.0001). In contrast, weight loss following step test was not significantly different in the control group at the end of the study period. Yoga training produced a marked increase in respiratory pressures and endurance in 40 mm Hg test in both male and female subjects (P < 0.05 for all comparisons). In conclusion, the present study demonstrates attenuation of the sweating response to step test by yoga training. Further, yoga training for a short period of six weeks can produce significant improvements in respiratory muscle strength and endurance.

Full text

164 Madanmohan et al Indian J Physiol Pharmacol 2008; 52(2)
Indian J Physiol Pharmacol 2008; 52 (2) : 164–170
EFFECT OF SIX WEEKS YOGA TRAINING ON WEIGHT LOSS
FOLLOWING STEP TEST, RESPIRATORY PRESSURES,
HANDGRIP STRENGTH AND HANDGRIP ENDURANCE
IN YOUNG HEALTHY SUBJECTS
MADANMOHAN*, SIVASUBRAMANIYAN K. MAHADEVAN,
SELVAKUMAR BALAKRISHNAN, MAYA GOPALAKRISHNAN
AND E. S. PRAKASH+
Department of Physiology,
Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER),
Pondicherry – 605 006
( Received on January 5, 2008 )
Abstract : The present study was designed to test whether yoga training
of six weeks duration modulates sweating response to dynamic exercise
and improves respiratory pressures, handgrip strength and handgrip
endurance. Out of 46 healthy subjects (30 males and 16 females, aged
17–20 yr), 23 motivated subjects (15 male and 8 female) were given yoga
training and the remaining 23 subjects served as controls. Weight loss
following Harvard step test (an index of sweat loss), maximum inspiratory
pressure, maximum expiratory pressure, 40 mm endurance, handgrip
strength and handgrip endurance were determined before and after the six
week study period. In the yoga group, weight loss in response to Harvard
step test was 64±30 g after yoga training as compared to 161±133 g before
the training and the difference was significant (n = 15 male subjects,
P<0.0001). In contrast, weight loss following step test was not significantly
different in the control group at the end of the study period. Yoga training
produced a marked increase in respiratory pressures and endurance in 40
mm Hg test in both male and female subjects (P<0.05 for all comparisons).
In conclusion, the present study demonstrates attenuation of the sweating
response to step test by yoga training. Further, yoga training for a short
period of six weeks can produce significant improvements in respiratory
muscle strength and endurance.
Key words : asans pranayams shavasan step test
*Correspondence and requests for reprints to :
Dr. Madanmohan, Director-Professor & Head, Department of Physiology, JIPMER, Pondicherry – 605 006.
E-mail: drmadanmohan123@rediffmail.com
+E.S.Prakash is currently affiliated with the School of Medicine, Faculty of Medical and Health Sciences,
Asian Institute of Medicine, Science, & Technology, 08100 Bedong, Kedah Darul Aman, Malaysia.
INTRODUCTION
The effect of yoga training on exercise
tolerance has been reported earlier (1, 2).
The beneficial effects of yoga training on
exercise tolerance might include decreased

Indian J Physiol Pharmacol 2008; 52(2) Yoga Training and Physiological Functions 165
sweating in response to exercise. There
is only one report on the effect of yoga
training on thermoregulation measured by
sweating response to exercise (3). The
present study was specifically an attempt
to determine whether yoga training of
short duration (six weeks) modifies the
sweating response to dynamic exercise in a
hot and humid environment. The effect of
training on sweating response to dynamic
exercise was studied using Harvard step
test (4).
The effects of yoga training on pulmonary
function have been previously studied (5, 6).
These studies have mainly investigated the
effects of yoga training on indices of airway
resistance such as peak expiratory flow rate
and forced vital capacity. However, it is likely
that some of the beneficial effects of yoga
training are mediated through improvements
in respiratory muscle strength, which can
be determined readily. Maximal inspiratory
pressure (MIP) and maximal expiratory
pressure (MEP) are useful and sensitive
indices of the strength of inspiratory and
expiratory muscles respectively (7, 8).
Indeed, in a previous study from our
laboratory, we have shown that yoga training
is associated with improvements in
respiratory muscle strength and 40 mm Hg
endurance but this study lacked a control
group (7). We planned to undertake the
present study with the objectives to
determine whether six weeks yoga training
produces improvements in handgrip strength,
handgrip endurance, and respiratory
pressures in young healthy subjects,
and alters weight loss response (an indicator
of the sweating response) to dynamic
exercise.
MATERIAL AND METHODS
Forty six (30 male and 16 female) healthy
subjects between 17-20 years consented to
participate in the present study. Of these,
23 (15 males and 8 females) motivated
subjects volunteered to receive yoga training
(yoga group) and the remaining 23 (15 males
and 8 females) served as controls (control
group). Written informed consent was
obtained from the participants after
explaining the purpose of the study,
testing procedures and yoga training
schedule. The Institute Research Council and
Ethics Committee approved the study
protocol.
Experimental protocol: Tests were done under
standard laboratory conditions after
familiarising the subjects with the testing
procedure and the study protocol. Height and
weight were measured and body mass index
(BMI) was calculated [weight (kg) divided by
square of height (m2)]. In both groups, the
parameters described below were recorded
before and at the end of six week study
period.
Resting heart rate (HR) and blood pressure
(BP) : Baseline HR and BP values were
obtained after five minutes rest in the sitting
position. BP was recorded using Colins
automated BP monitor (COLIN Press-
Mate, COLIN Corporation, Japan) which
measures BP by the oscillometric method.
Pulse pressure (PP) was calculated as the
difference between systolic pressure (SP) and
diastolic pressure (DP). Mean arterial
pressure (MAP) was calculated as DP + 1/3
PP.

166 Madanmohan et al Indian J Physiol Pharmacol 2008; 52(2)
Maximum inspiratory pressure (MIP),
maximum expiratory pressure (MEP) and 40
mm Hg endurance : MIP was obtained by
asking the subject to breathe out fully and
then inhale maximally from the mouthpiece
connected to a mercury manometer. MEP
was determined by asking the subject to take
in a full breath and blow forcefully into the
mouthpiece of the mercury manometer. The
maximum pressure that was maintained for
at least 3 seconds was noted in both the
cases. Respiratory pressures depend on lung
volumes; the highest MIP is obtained near
residual volume while the highest MEP is
obtained near total lung capacity (7, 8). For
determining 40 mm Hg endurance, the
subject was asked to take in a full breath
and blow into the mouthpiece of a mercury
manometer and raise the pressure to 40 mm
Hg. The maximum time for which the subject
could maintain this pressure was recorded
as 40 mm Hg endurance. It was ensured that
the subjects did not use oral muscles or
tongue to develop pressure or block the
tubings.
Handgrip strength (HGS) and handgrip
endurance (HGE) : HGS was determined
using a handgrip dynamometer (INCO,
Ambala, India) by asking the subject to
maintain a maximal voluntary contraction
(MVC) for at least 3 seconds with the
dominant arm outstretched in front and
parallel to the ground. HGE was determined
by noting the maximum time (seconds) for
which the subject could maintain 1/3 of MVC.
Step test : Female subjects opted out of the
step test. Male subjects (n = 15 in each
group) were familiarized with the procedure
2–3 days before the actual recording was
done. Weight prior to exercise was measured
using a weighing machine (TESTUT,
France), having a precision of 20 g. The study
was done at a laboratory temperature of 32
±1°C and humidity of 60–70%. The Harvard
step test was done by asking the subject to
step up and down a wooden platform of 45
cm height at the rate of 30 times per minute
for a duration of 2 mins. After the exercise,
the subject was wiped dry with a clean dry
towel and weighed again. The difference
between the weight before and immediately
after the step test was taken as weight loss
as a result of exercise-induced sweating.
Yoga training : Yoga training including asans,
pranayams and shavasan was imparted to the
yoga group by one of the authors
(Madanmohan), who is a trained yoga
instructor. Practice sessions were held
between 4.30 and 6.00 PM, Monday through
Saturday, for a duration of six weeks in a
pleasant lawn. Sessions began with a brief
prayer. The sequence and duration of the
yogic techniques practised by the yoga group
are summarized in Table I.
Statistical analysis : Data are expressed as
mean±SD. Intergroup comparisons were done
using Student’s unpaired t-test and within
group comparisons by Student’s paired t-test.
Where compared variances were unequal,
Welch’s correction was applied. Differences
in means were considered statistically
significant when the two-tailed P value <0.05.
RESULTS
The results are given in Tables II and
III. The height (m), weight (kg) and body
mass index in (kg/m2) in male yoga group
were 1.7±0.07, 64.4±11.4, and 22±3.14,
respectively. In the female yoga group, the

Indian J Physiol Pharmacol 2008; 52(2) Yoga Training and Physiological Functions 167
corresponding values were 1.59±0.06, 55.8±9,
and 22.4±4.5, respectively. In the male
control group the corresponding values
were 1.7±0.1, 63.6±10.9 and 21.9±2.7,
respectively. In the female control group
they were 1.58±0.04, 58.8±8.4 and 23.5±3.2,
respectively. The baseline parameters were
comparable between the yoga and the control
groups (P>0.05 for all). In each group,
cardiovascular, respiratory and handgrip
parameters were recorded in 20 (12 male
and 8 female) subjects. Weight loss response
to step test was recorded for male subjects
only (n=15 in each group).
HR and BP : There was no significant change
in HR or SP in any of the study groups.
However, six weeks of yoga training produced
a significant decrease in DP in males
(P=0.002) as well as females (P=0.03). Yoga
training increased the PP in males as well
as females (P=0.02 in each case). Yoga
training produced a decrease in MAP which
was significant (P=0.005) in males but not
in females (Tables II and III). In contrast,
TABLE I : The yogic techniques, their sequence,
duration and the number of repetitions
practiced by the yoga group.
S.No. Yogic technique Duration and number
of repetition
1. Prayer 5 min
2. Mukh-bhastrika 12 sec× 3
in vajrasan
3. Tribandh (mool+uddiyan 20 sec × 2
+jalandhar bandh)
4. Talasan (with breath 6: 6: 6 sec × 2
control)
5. Trikonasan (with 6: 6: 6 sec × 2
breath control)
6. Navasan 6: 6: 6 sec × 2
7. Naukasan 6: 6: 6 sec×2
8. Brahm mudra 48 sec × 2
(with Aum chant)
9. Ardh-matsyendrasan 6: 6: 6 sec × 2
10. Bhujangasan (with 6: 6: 6 sec× 2
breath control)
11. Bakasan 20 sec× 2
12. Viparitakarani 20 sec× 2
13. Dharmikasan (with 20 sec× 2
jyoti darshan)
14. Nadi shuddhi pranayam 24 sec × 5
15. Pranav pranayam with 12 sec × 5
mahat yoga breathing
16. Shavasan 10 min
TABLE II : Effect of yoga training on various parameters in males. Data are given as the mean±SD for
12 subjects except for the weight before step test and weight loss following step test (n=15).
Yoga group Controls
Before After P value Before After P value
Resting systolic pressure (mm Hg) 118±9 117±8 0.53 118±9 122±13 0.11
Resting diastolic pressure (mm Hg) 74±9 62±7 0.002 69±7 69±7 1
Resting pulse pressure (mm Hg) 44±10 54±10 0.02 49±9 52±10 0.11
Resting mean pressure (mm Hg) 89±8 80±5 0.005 86±6 87±8 0.55
Resting heart rate (beats per minute) 70±14 67±14 0.36 75±10 73±14 0.68
Maximum inspiratory pressure (mm Hg) 124±28 160±23 0.001 120±30 138±28 0.01
Maximum expiratory pressure (mm Hg) 88±16 107±20 <0.0001 85±15 94±29 0.23
Endurance in the 40 mm Hg test (s) 44±9 72±13 <0.0001 46±11 56±12 0.04
Handgrip strength (kg) 35±5 36±9 0.15 32±7 32±9 0.82
Handgrip endurance (s) 76±34 88±48 0.43 86±47 86±53 0.67
Weight before step test (kg) 64±11.7 64±11 0.64 63.1±11 63±11 0.51
Weight loss following step test (g) 161±133 64±30 0.0001 133±109 131±52 0.79
Note: P values for comparisons at baseline between yoga and control groups was > 0.05 for all parameters.

168 Madanmohan et al Indian J Physiol Pharmacol 2008; 52(2)
significantly reduced to 64±30 g (P=0.0001).
In contrast, there was no significant change
in the controls.
DISCUSSION
The physiologic responses to physical
training have been well studied by many
investigators (9). The effect of yoga training
on physiologic response to cold stress has
been reported (10). Exercise tolerance is an
index of physical fitness (11). An important
finding in the present study is that yoga
training is associated with a significant
decrease in exercise-induced sweating, an
index of heat generated during dynamic
exercise. Cutaneous vasodilation and
increase in blood flow are important
determinants of sweating when core body
temperature increases during exercise (12).
However, it is possible that yoga training
may have had a favorable effect on energy
metabolism in skeletal muscle; i.e., the same
workload would generate less heat with less
utilization of energy substrate and oxygen
thereby decreasing sweating.
the changes in the above parameters were
not significant in the control group.
Respiratory pressures, HGS and HGE : In male
as well as female subjects, yoga training
produced a marked and highly significant
increase in MIP as well as MEP in males as
well as females (P<0.001). However in the
control group, there were no significant
changes in the above parameters except in
MIP in males (Tables II and III). 40 mm Hg
endurance showed a highly significant
increase after yoga training (P<0.0001 in
males and 0.0002 in females). In contrast,
the increase in this parameter was less in
controls. There were no significant changes
in HGS in either group. Yoga training
produced an increase in HGE which was
statistically significant in females (P=0.03)
but not in males.
Sweating response to step test : In the male
subjects (n=15 in both groups), the weight
loss in response to 2 min Harvard step
test was 161±133 g before yoga training.
After yoga training, the weight loss was
TABLE III : Effect of yoga training on various parameters in females.
Data are given as the mean±SD for 8 subjects.
Yoga group Controls
Before After P value Before After P value
Resting systolic pressure (mm Hg) 99±13 103±13 0.30 102±10 109±8 0.11
Resting diastolic pressure (mm Hg) 69±9 62±6 0.03 67±8 67±10 0.90
Resting pulse pressure (mm Hg) 30±6 41±12 0.02 35±7 43±6 0.06
Resting mean pressure (mm Hg) 79±10 76±7 0.30 79±8 81±9 0.58
Resting heart rate (beats per minute) 79±8 77±6 0.35 79±8 79±8 0.87
Maximum inspiratory pressure (mm Hg) 96±17 123±14 <0.0001 109±18 110±19 0.74
Maximum expiratory pressure (mm Hg) 61±17 69±20 0.003 70±12 73±14 0.27
Endurance in 40 mm Hg test (s) 33±14 55±18 0.0002 38±14 50±16 0.03
Handgrip strength (kg) 18±4 20±4 0.46 18±3 18±4 0.90
Handgrip endurance (s) 36±10 55±36 0.03 49±23 49±30 0.96
Note: P values for comparisons at baseline between yoga and control groups was > 0.05 for all parameters.

Indian J Physiol Pharmacol 2008; 52(2) Yoga Training and Physiological Functions 169
Our results clearly indicate that yoga
training of six weeks is associated with a
decrease in DP in males as well as females.
This may be due to a decrease in baseline
sympathetic nerve activity. It is worth noting
that yoga training produced a significant
increase in PP, a parameter that is
influenced by stroke volume and compliance
of large arteries. Changes in arterial
compliance over the six week study period
might have been insignificant. Thus, the only
other explanation is that the hemodynamic
effect of yoga training was to increase the
stroke volume through the arterial
baroreflex mechanism. The decrease in MAP
was statistically significant in males but not
in females possibly because the baseline
MAP was lower in females. Indeed, it is well
established that women have lower tonic
sympathetic support of arterial blood
pressure (13).
Maximum respiratory pressures are
simple and accurate indices of strength of
respiratory muscles and their values are
altered even in early states of respiratory
diseases (8, 14). The increase in MIP and
MEP following yoga training of six weeks
duration suggests that yoga training has a
favorable effect on respiratory muscle
strength. This can be attributed to a
combination of deep breathing and yoga
postures of our training programme. In
earlier studies also, we have found that yoga
training of longer duration improves
respiratory pressures, HGS and HGE (7, 14).
Endurance in the 40 mm Hg test is
influenced by strength and endurance of
respiratory muscles. In addition, it is
influenced by breath holding time, a
parameter that is complexly affected by
several factors including mechanisms that
regulate respiration. It is clear from our data
that increases in endurance are far greater
and significant in the yoga group as compared
to the control group. This suggests that the
effect of yoga training might have increased
the strength and endurance of respiratory
muscles and may contribute to enhanced
voluntary control of breathing.
HGS is influenced by effort, integrity of
motor neuronal pathways, muscle bulk and
contractility. Yoga training-induced increase
in HGS was not significant in male as well
as female subjects suggesting that yoga
training given for a short period of six weeks
does not influence it. When effort is
maximal, HGE is influenced by the strength
and metabolic capacity of exercising skeletal
muscles. A significant increase in HGE in
female subjects may reflect the fact that, in
females the baseline endurance is less and
training readily enhances it. On the other
hand, in males, the increase in HGE brought
about by training was less possibly because
they were physically more active than
females at baseline. In light of our
observations, it can be inferred that yoga
training might be more beneficial in
physically less active individuals.
In the present study we could not
determine the effect of yoga on sweating
response to step test in female subjects as
they opted out of the step test. In conclusion,
the present study suggests that short-term
yoga training improves the thermoregulatory
efficiency as measured by the weight loss
response to muscular exercise. Further, six
weeks yoga training improves respiratory
muscle strength and endurance, a finding
previously reported by us to have occurred
with longer durations of training (7).

170 Madanmohan et al Indian J Physiol Pharmacol 2008; 52(2)
ACKNOWLEDGMENTS
This study was supported by the Defence
Research Development Organization (DRDO),
New Delhi. We are grateful to Dr. W.
Selwamurthy, Chief Controller, R&D, DRDO,
for his advice and encouragement. Thanks
are due to our subjects for their whole-
hearted cooperation. Sivasubramaniyan K.
Mahadevan, Selvakumar Balakrishnan and
Maya Gopalakrishnan were on ICMR
sponsored Short-Term Studentships during
the study period.
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