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R E S E A R C H A R T I C L E Open Access
Examining the effect of Withania somnifera
supplementation on muscle strength and
recovery: a randomized controlled trial
Sachin Wankhede
1
, Deepak Langade
2
, Kedar Joshi
3
, Shymal R. Sinha
4
and Sauvik Bhattacharyya
5*
Abstract
Background: Withania somnifera (ashwagandha) is a prominent herb in Ayurveda. This study was conducted to
examine the possible effects of ashwagandha root extract consumption on muscle mass and strength in healthy
young men engaged in resistance training.
Methods: In this 8-week, randomized, prospective, double-blind, placebo-controlled clinical study, 57 young male
subjects (18–50 years old) with little experience in resistance training were randomized into treatment (29 subjects)
and placebo (28 subjects) groups. Subjects in the treatment group consumed 300 mg of ashwagandha root extract
twice daily, while the control group consumed starch placebos. Following baseline measurements, both groups
of subjects underwent resistance training for 8 weeks and measurements were repeated at the end of week 8.
The primary efficacy measure was muscle strength. The secondary efficacy measures were muscle size, body
composition, serum testosterone levels and muscle recovery. Muscle strength was evaluated using the 1-RM load
for the bench press and leg extension exercises. Muscle recovery was evaluated by using serum creatine kinase
level as a marker of muscle injury from the effects of exercise.
Results: Compared to the placebo subjects, the group treated with ashwagandha had significantly greater
increases in muscle strength on the bench-press exercise (Placebo: 26.4 kg, 95 % CI, 19.5, 33.3 vs. Ashwagandha:
46.0 kg, 95 % CI 36.6, 55.5; p= 0.001) and the leg-extension exercise (Placebo: 9.8 kg, 95 % CI, 7.2,12.3 vs.
Ashwagandha: 14.5 kg, 95 % CI, 10.8,18.2; p= 0.04), and significantly greater muscle size increase at the arms
(Placebo: 5.3 cm
2
, 95 % CI, 3.3,7.2 vs. Ashwagandha: 8.6 cm
2
, 95 % CI, 6.9,10.8; p= 0.01) and chest (Placebo: 1.4 cm,
95 % CI, 0.8, 2.0 vs. Ashwagandha: 3.3 cm, 95 % CI, 2.6, 4.1; p< 0.001). Compared to the placebo subjects, the
subjects receiving ashwagandha also had significantly greater reduction of exercise-induced muscle damage as
indicated by the stabilization of serum creatine kinase (Placebo: 1307.5 U/L, 95 % CI, 1202.8, 1412.1, vs.
Ashwagandha: 1462.6 U/L, 95 % CI, 1366.2, 1559.1; p= 0.03), significantly greater increase in testosterone level
(Placebo: 18.0 ng/dL, 95 % CI, -15.8, 51.8 vs. Ashwagandha: 96.2 ng/dL, 95 % CI, 54.7, 137.5; p= 0.004), and a
significantly greater decrease in body fat percentage (Placebo: 1.5 %, 95 % CI, 0.4 %, 2.6 % vs. Ashwagandha: 3.5 %,
95 % CI, 2.0 %, 4.9 %; p= 0.03).
Conclusion: This study reports that ashwagandha supplementation is associated with significant increases in
muscle mass and strength and suggests that ashwagandha supplementation may be useful in conjunction with a
resistance training program.
Keywords: Ashwagandha, Adaptogen herbs, Muscle, Muscle strength, Muscle mass, Testosterone, Body fat,
Creatine kinase
* Correspondence: dr.sauvik.bhattacharyya@gmail.com
5
Department of Pharmaceutical Technology, NSHM Knowledge Campus, 124
B.L. Saha Road, Kolkata 700053, India
Full list of author information is available at the end of the article
© 2015 Wankhede et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Wankhede et al. Journal of the International Society of Sports Nutrition (2015) 12:43
DOI 10.1186/s12970-015-0104-9
Background
Both the modern medical literature and traditional
Ayurveda writings report many potential health benefits
of the Ashwagandha herb (Withania somnifera, also
known as Indian Ginseng or Winter Cherry) under the
rubrics of anti-stress effects, neuroprotective effects,
immunomodulatory effects, and rejuvenating effects, via
the herb's interplay with the nervous system, the endo-
crine system, the cardiopulmonary system, the energy
production system and the immune system including
analgesic, antimicrobial, anti-inflammatory, anti-tumor,
anti-stress, anti-diabetic, neuroprotective, immunopro-
tective and cardioprotective effects [1–7]. This paper fo-
cuses on ashwagandha as an ergogenic aid and is the
first to present the results of a randomized, double-
blind, placebo-controlled clinical study on ashwagand-
ha’s effects, as an adjuvant to a resistance training
program, multifariously on muscle strength, muscle
hypertrophy, muscle recovery and body composition.
We add to the broader literature on ashwagandha’s effect
on physical performance. This literature has only a small
set of published papers [8–10], which is surprising be-
cause traditional Ayurveda explicitly advocates the use
of ashwagandha toward “bala”, which means “strength”
in the Sanskrit language [11] .
Ashwagandha is a member of the family of herbs re-
ferred to as “adaptogens”. The term “adaptogen”is ap-
plied to a herb with phytonutrients that regulate
metabolism when a body is perturbed by physical or
mental stress, and help the body adapt by (a) normaliz-
ing system functions, (b) developing resistance to future
such stress, and (c) elevating the body’s functioning to a
higher level of performance [12]. The adaptogen family
of herbs has many members, noteworthy among them
being ashwagandha, rhodiola, ginseng, schisandra and
maca [12]. Adaptogens are used commonly for stress
relief, brain health, adrenal health and for ameliorating
HPA-axis dysfunction. More recently, adaptogens have
started to be used in sports supplements that aim to
enhance physical fitness. Recent research has found
adaptogens to be promising in this application domain
[13–15]. However, the results in this literature are mixed
and therefore more research is needed so that we have a
better understanding of adaptogens as ergogenic aids
[14]. This present study attempts to make a small step
towards such an understanding.
A resistance training program consists of exercises
that cause skeletal muscles to contract against external
resistance. The body often responds to such programs
with increased strength and correlated adaptations
[16–19]. The present research work was motivated by the
hypothesis that ashwagandha supplementation can in-
crease some of these adaptations and gains, thereby serv-
ing as a useful adjuvant to a resistance training program.
There are several rationales underlying this hypothesis:
Studies in healthy normal adults demonstrated that ashwa-
gandha improves muscular strength/coordination, and car-
diorespiratory endurance [8–10]. Ashwagandha’s roots are
classified as a “rasayana”(rejuvenator), and have been used
toward promoting health and longevity, slowing the aging
process, revitalizing the body and generally creating a sense
of well-being [4, 20]. Ashwagandha has a wide range of
pharmacological effects: it has anxiolytic, hypotensive,
sedative, central nervous system, immunomodulatory, an-
algesic, anti-inflammatory, anti-tumor, anabolic, cardiopul-
monary and antioxidant effects [4, 9, 21–27]. It also
stimulates respiratory function, causing smooth muscle
relaxation, and stimulates thyroid activity [3]. Studies in
humans show that ashwagandha is well tolerated and is
associated with decreases in cortisol [28], and increases in
testosterone [29]. Research suggests that ashwagandha may
reduce increases of blood urea nitrogen, lactic acid, cor-
ticosterone in response to stress [4], and also reduce the
tendency of dopamine receptors in the brain to activate
under stress [3, 5, 21]. Ashwagandha contains several ac-
tive components, which may account for the various
mechanisms of action by which it exerts its effects. These
include steroidal lactones (withanolides, withaferins), sapo-
nins and alkaloids like isopelletierine and anaferine [5, 30].
The adaptogenic properties of ashwagandha raise the
possibility of it being an effective ergogenic aid because
the strain from exercise can be viewed as a form of
stress, with enhanced human physical performance as
the corresponding stress response upon ashwagandha
supplementation. This study seeks to examine the hy-
pothesis that ashwagandha supplementation may moder-
ate the body’s adaptation in response to resistance
training. While this hypothesis is rooted in traditional
Ayurvedic medicine and previous studies, well designed
clinical trials are clearly needed to test and characterize
the effects. The present double-blind, randomized,
placebo-controlled study in healthy adults will, it is
hoped, help toward expanding scientific understanding
in this domain.
Methods
The study design, recruitment and methods were ap-
proved by all the authors’institutes’review boards on
human subjects’studies and followed the guidelines of
the Declaration of Helsinki and Tokyo for humans.
Subjects selection, incentives and participation
Healthy male subjects (18–50 years old) were recruited
by use of fliers circulated in the vicinity of the gymna-
sium which served as the site of the training program.
Subject enrollment, allocation, attrition, and analysis is
summarized in Fig. 1. The purpose and protocol for the
study was described to the subjects. The subjects had to
Wankhede et al. Journal of the International Society of Sports Nutrition (2015) 12:43 Page 2 of 11
sign a written consent for the study, agree to refrain
from alcohol and tobacco during the study, and had to
receive permission of their physician to participate. Sub-
jects were excluded from the study if they met any of
the following criteria: 1) taking any medication or
steroids to enhance physical performance, 2) weight loss
of >5 kg in the previous 3 months, 3) any history of drug
abuse, smoking 10+ cigarettes day or consuming more
than 14 grams of alcohol daily, 4) hypersensitivity to
ashwagandha, 5) history of any orthopedic injury or
surgery within the previous 6 months, 6) participation in
other clinical studies during the previous 3 months, 7)
any other conditions which the investigators judged
problematic for participation in the study. Subjects were
requested to refrain from using anti-inflammatory agents
during the study and to report any ill effects from con-
suming the ashwagandha/ placebo.
Because participation in the study would require a sig-
nificant amount of time allocation from the subjects, the
recruiters offered as compensation one year of paid
membership to the gym and three months of profes-
sional trainer support. As Fig. 1 indicates, 57 subjects
were initially recruited for the study and 50 completed
the study, including 25 in the ashwagandha group and
25 in the placebo group. For the ashwagandha treatment
group and for the placebo group, the mean age ± stand-
ard deviation were 28 ± 8 years and 29 ± 9 years,
respectively.
Study design
This study was a prospective, double-blind, placebo-con-
trolled parallel group study to measure the possible effects
of ashwagandha extract on muscle strength/size, muscle
recovery, testosterone level and body fat percentage in
Fig. 1 CONSORT schematic diagram
Wankhede et al. Journal of the International Society of Sports Nutrition (2015) 12:43 Page 3 of 11
young males undergoing weight training. Adverse events
were assessed by patient/ researcher reporting and the
PGATT (Physicians Global Assessment of Tolerability to
Therapy) form.
The resistance training program
The resistance training program consisted of sets of
exercises over major muscle groups in both the upper
body and the lower body. Directions for the resistance
training were obtained from publications of the National
Strength and Conditioning Association (NSCA) [31–33].
Each subject in both groups was asked to come to a
training session every other day, with one rest day per
week, for three days per week. Every session began with
a warm up consisting of five minutes of low-intensity
aerobic exercise.
The subjects were instructed to perform, for each set,
as many repetitions as they could until failure. The sub-
jects were asked to go through the full range of motion
and were demonstrated the proper technique for safe
and effective weight lifting.
Exercise selection
The specific exercises and the number of sets in each
session were as follows. For the first week, the subjects
were asked to perform the barbell squat (2 sets), the leg
extension (1 set), the seated leg curl (2 sets), the ma-
chine chest press (1 set), the barbell chest press (2 sets),
the seated machine row (1 set), the one-arm dumbbell
row (2 sets), the machine biceps curl (1 set), the dumbbell
biceps curl (2 sets), the cable triceps press-down (2 sets),
the dumbbell shoulder press (2 sets), and the straight-arm
pull-down (2 sets). For the second week, the subjects were
asked to perform the leg extension (1 set), the barbell
squat (2 sets), the barbell chest press (3 sets), the seated
leg curl (2 sets), the seated cable row (3 sets), dumbbell
biceps curl (3 sets), the cable triceps press-down (3 sets),
the dumbbell shoulder press (3 sets), and the straight-arm
pull-down or lat pull-down (3 sets). After this two-week
acclimatization phase, for the rest of the study, the
subjects were asked to perform the barbell squat (3 sets),
the leg extension (3 sets), the leg curl (2 sets), one chest
exercise (flat, incline or decline press or fly, cable cross-
over, 3 sets), one back exercise (rows, pull up, pull down
or seated cable row, 3 sets), another chest exercise (3 sets),
another back exercise (3 sets), one biceps exercise or one
triceps exercise (curls or extensions, 3 sets), and one
shoulder exercise (raises or presses, 3 sets).
How the target number of repetitions was chosen
The number of repetitions for the initial two weeks was
set to be 15, which is a moderately high number (implying
correspondingly lower weights), chosen to allow a sub-
ject’s body and neural system to get accustomed to
strength training [31, 33]. The subsequent 6 weeks had a
varying number of repetitions, akin to a rudimentary non-
linear periodization programs, because these have been
shown to induce greater adaptation and more gains in
muscle strength and size [33]. The number of repetitions
specified for each of the days in the training program is
given in Table 1.
How the load was chosen
The load was chosen to be such that the subject would
reach the failure-point upon performing approximately
the target number of repetitions (chosen as described in
the preceding paragraph) when lifting that load. The
corresponding load for an exercise was estimated on the
basis of the 1RM prediction equations of Epley, Wathan
and others [34].
Treatments and dosing
The researchers engaged a local laboratory to fill
cellulose-based vegetarian capsules with either 300 mg
of starch or 300 mg of a high-concentration ashwa-
gandha root extract, KSM-66, manufactured by Ixoreal
BioMed, Los Angeles, California, USA. This extract was
produced using a water-based process using no alcohol
or solvents and is standardized to a 5 % concentration of
withanolides as measured by HPLC. The two capsules
were identical in appearance, weight, and texture. Both
the control and ashwagandha groups received a bottle of
60 pills at start of study and at 4 weeks. The pill count
at 4 weeks allowed for a compliance check. The subjects
were instructed to store the capsules between 18 and
32 °C and to take the capsules twice a day, once shortly
after awakening and again shortly before bed, for the 8
weeks of the study.
Primary efficacy endpoint
The primary efficacy endpoint was muscle strength.
Muscle strength is often measured by 1RM, the “one-
repetition maximum”, which is specific to a certain per-
son and a certain exercise movement and refers to the
maximal load that a subject can lift for one movement
cycle of the exercise [31, 35]. Measurements were made at
the first day of training and again 2 days after the 8 week
training ended. The equipment used machine models
DPL0802 (bench press) and DSL0605 (leg extension),
Table 1 The targeted number of repetitions over the course of
the resistance training program
Weeks 1–2 Weeks 3–4 Weeks 5–6 Weeks 7–8
Day115135 9
Day 2 15 9 13 5
Day315135 9
Day 4 15 9 13 5
Wankhede et al. Journal of the International Society of Sports Nutrition (2015) 12:43 Page 4 of 11
manufactured by Precor (Woodinville, Washington, USA
The 1-RM measurement was done using a variant of the
widely used Baechle-Earle-Wathen protocol, employing
the multiple RM method [36–40]. To reduce measure-
ment error in strength assessment, we were careful to
ensure consistency in the range of motion and that each
movement on the chest press and the leg extension was
complete and in accordance with the guidelines of the
NSCA.
Secondary efficacy endpoints
The secondary efficacy endpoints related to serum testos-
terone level, muscle recovery and anthropometric factors
capturing muscle size and body fat percentage.
Anthropometry
Muscle size: Muscle size was measured at 3 sites: the
arm (flexed mid upper arm), chest (sternum at mid-tidal
volume) and upper thigh (just inferior to gluteal fold).
Measurements were done on the first day of the training
period and 2 days after the last day of training. For the
chest, we measured the girth, taken at the level of the
middle of the sternum, with the tape passing under the
arms and at the end of a normal expiration. For the
thigh and arm, we assessed the maximal cross-sectional
area (CSA) using the method of Moritani-DeVries,
which is based on girth and skin-fold measurements
[41–43]. The literature shows that the muscle CSA mea-
sures obtained by the Moritani-DeVries method are
highly correlated with measures obtained by computer
tomography or muscle biopsy, the gold standards for
muscle CSA measurement [41–43]. Because of this high
correlation, the across-time (Day 0 versus Day 56) or
across-group (treatment versus placebo) comparisons on
the basis of the Moritani-DeVries method are strongly
indicative of the directionality and strength of the corre-
sponding comparisons on the basis of the computer
tomography. We chose to use the Moritani-DeVries
method because it is less time-consuming and invasive
than computer tomography or biopsy, and therefore less
likely to discourage study participation.
Body fat percentage
Body fat percentage was calculated with a bioelectrical
impedance method using machine with electrodes
placed at the hand, wrist, foot, and ankle [44, 45]. Be-
cause bioelectrical impedance analysis based measure-
ment of fat composition is known to be affected by
extraneous factors like hydration level and temperature,
we tried to maintain consistency in these factors by
instructing the subjects to: 1) abstain from eating or
drinking for 4 h before measurements, 2) urinate 30 min
prior, 3) not engaged in exercise for 12 h prior and 4)
not consume alcohol of caffeinated products [35, 45].
Body composition was measured two days after the first
day of resistance training and again two days after the
last day of resistance training.
Testosterone
Total blood testosterone serum levels were measured
twice: once 2 days after the study commenced and again
2 days after the study ended. The blood draw was timed
to be between two hours and three hours of each sub-
ject’s regular waking time, and prior to any substantial
physical activity, in order to minimize the effects of the
natural diurnal variation in testosterone level. The 20 ml
blood draws were from an antecubital vein, punctured
with a 20-gauge disposable needle connected to a Vacu-
tainer tube. The blood serum samples were analyzed by
an ELISA (enzyme-linked immunosorbent assay).
Muscle recovery
Resistance training frequently damages skeletal muscle
tissue. Such damage can result in decreased muscle force
production and performance in subsequent training ses-
sions, thereby possibly reducing the extent of adaptation
and gains from resistance training [46]. Muscle recovery
refers to the reduction in exercise-induced muscle dam-
age over time. The level of creatine kinase, a protein, in
the blood is a commonly used measure of muscle dam-
age because this protein is specific to muscle tissue [47].
When muscles are overexerted, the muscle filaments are
damaged and become necrotic, thereby causing soluble
proteins like creatine kinase to migrate from muscle tis-
sue into the blood stream [48]. The body on its own re-
pairs such damage over 1 to 10 days and serum creatine
kinase returns to baseline levels [48]. A bout of exercise
tends to produce less damage in muscle tissue when re-
peated in subsequent training sessions after the body
gets accustomed to the exercise. This is because of adap-
tation and strengthening of the muscle tissue. Serum
creatine kinase was measured at 24 h and at 48 h after
the end of the first exercise session, and also at 24 h and
at 48 h after the end of the last exercise session approxi-
mately 8 weeks later, from 20 ml blood draws using a
20-gauge disposable needle and a Vacutainer setup. The
creatine kinase level was determined in a commercial la-
boratory using enzymatic analysis tracking nicotinamide
adenine diphesphopyridine (NADPH). The increase in
creatine kinase from the 24-h point to the 48-h point
can be taken as a biomarker of recovery in that a smaller
increase corresponds to faster stabilization of creatine
kinase level and hence faster recovery of muscle tissue
from exercise-induced damage.
Tolerability
The subjects were asked to report any adverse events ex-
perienced at any point in the study. We used the
Wankhede et al. Journal of the International Society of Sports Nutrition (2015) 12:43 Page 5 of 11
Physicians Global Assessment of Tolerability to Therapy
(PGATT) form [49–51]. Subjects used a five-point scale
to assess tolerability from “worst tolerability”(which cor-
responds to patients’not being able to tolerate the drug
at all) to “excellent tolerability”(which corresponds to
no adverse effects and the patient being able to tolerate
the drug excellently).
Statistical analysis
Assessment of statistical significance of continuous treat-
ment effects was done using ANOVA with group identity
(treatment versus placebo) as a factor. We used the
Mann-Whitney test if the data were found to be not
normally distributed. Frequencies of the tolerability
scale values were compared using the chi-square test
for contingency tables. The accepted level of signifi-
cance was α=0.05.
Results
Tables 2, 3, 4, 5 and 6 compare the treatment group and
the placebo group at baseline, at the start of the study
and at the end of the 8 week study for the following 5
factors: testosterone level (ng/dL), muscle strength on
the bench press 1-RM (Kg), muscle strength on the leg
extension 1-RM (Kg), muscle size at thighs (cm
2
),
muscle size at arms (cm
2
), muscle size at chest (cm),
body fat percentage, muscle recovery in terms of creat-
ine kinase levels change (U/L),
Primary efficacy measure: muscle strength
There was a significant increase in muscle strength and
muscle size in both the ashwagandha group and the pla-
cebo group, for both the upper and lower body. This is
unsurprising because both group engaged in resistance
training. The focal question is whether the adaptation is
greater under ashwagandha supplementation. Table 2
and Fig. 2 show that the increases in muscle strength
were statistically significantly greater in the ashwagandha
group than in the placebo group, for the upper body
(Placebo: 26.42 kg, 95 % CI, 19.52, 33.32 vs. Ashwa-
gandha: 46.05 kg, 95 % CI 36.56, 55.54; p= 0.001) and
the lower body (Placebo: 9.77 kg, 95 % CI, 7.18, 12.35 vs.
Ashwagandha: 14.50 kg, 95 % 10.76, 18.23; p= 0.04).
Secondary efficacy measures
Anthropometry
Muscle Size: For muscle size (Table 3; Fig. 2), the in-
creases are significantly greater in the ashwagandha
group than the placebo group in the arm (Placebo: 5.30
cm
2
, 95 % CI, 3.34,7.25 vs. Ashwagandha: 8.89 cm
2
,
95 % 6.95,10.84; p= 0.01) and chest (Placebo: 1.43 cm,
95 % CI, 0.83, 2.02 vs. Ashwagandha: 3.37 cm, 95 % CI,
2.59, 4.15; p< 0.001) but not in the thighs (Placebo: 6.22
cm
2
, 95 % CI, 2.61, 9.84 vs. Ashwagandha: 8.71 cm
2
,
95 % CI, 4.56, 12.87; p= 0.36).
Body composition: Table 4 shows that body fat percent-
ages declined in both groups over the 8 week study, with
the fat percentage decrease being significantly greater
among subjects in the ashwagandha group as compared
to the placebo group (Placebo: 1.52 %, 95 % CI, 0.46, 2.59,
vs. Ashwagandha: 3.47 %, 95 % CI, 1.99, 4.95; p=0.03).
Serum testosterone
Over the eight weeks, there was a significant increase in
testosterone level in the ashwagandha treatment group
relative to the placebo group (Table 5; Fig. 3). The in-
crease in testosterone level was significantly greater with
ashwagandha supplementation than with the placebo
(Placebo: 18.00 ng/dL, 95 % CI, -15.83, 51.82 vs. Ashwa-
gandha: 96.19 ng/dL, 95 % CI, 54.86, 137.53; p= 0.004).
While the mean post-intervention level was notably
higher in the ashwagandha group than in the placebo
group (726 versus 693), the numbers are not detectable
as statistically significantly different, very likely because
the across-subject variance is high.
Muscle recovery
Recall that the level of recovery from exercise-induced
muscle damage is assessed through the increase in level
of serum creatine kinase from Hour 24 to Hour 48 after
the end of the resistance training session. A smaller in-
crease in this muscle protein in the blood stream
Table 2 Muscle strength
Treatment group Placebo group Between group comparison
Mean (SD) Mean (SD) (p-values)
Sample size (n) n=25 n=25
Bench Press 1RM (Kg) Pre intervention 33.21 (8.50) 31.35 (7.97) 0.44
Post intervention 79.26 (25.90) 57.77 (16.48) 0.001
Change 46.05 (23.00); 95 % CI: 36.56, 55.54** 26.42 (16.72); 95 % CI: 19.52, 33.32** 0.001
Leg Extension 1RM (Kg) Pre intervention 27.89 (4.24) 25.22 (7.03) 0.11
Post intervention 42.38 (10.80)** 34.98 (10.54)** 0.02
Change 14.50 (9.04); 95 % CI: 10.76, 18.23** 9.77 (6.27); 95 % CI: 7.18, 12.35** 0.04
** = p< 0.001 within group compari son
Wankhede et al. Journal of the International Society of Sports Nutrition (2015) 12:43 Page 6 of 11
corresponds to faster muscle tissue repair, which in turn
corresponds to greater recovery. Table 6 and Fig. 3 show
how this metric varied across groups and over time. It is
important to keep in mind that smaller numbers are to
be interpreted as better recovery. What is striking is that
recovery was dramatically better after 8 weeks of resist-
ance training, in both the ashwagandha group and the
placebo group, likely because of muscle tissue getting ac-
customed to the training regimen and developing greater
integrity to resist any damage. Comparing the ashwa-
gandha group and the placebo group, the results showed
that recovery is substantially higher in the ashwagandha
group than in the placebo group (Placebo: 1307.48 U/L,
95 % CI, -1202.82, 1412.14 vs. Ashwagandha: 1462.68 U/
L, 95 % CI, 1366.27, 1559.09; p= 0.03).
Tolerability
No serious side effects were reported by subjects in ei-
ther group. All subjects rated tolerability as either “good”
or “excellent”on the PGATT form. There was no statis-
tically significant difference in PGATT scores between
the 2 groups.
Discussion
This is the first research paper that we know of that
studies ashwagandha as an adjuvant to resistance train-
ing programs. Because subjects in both the ashwagandha
group and the placebo group engaged in resistance
training, we would expect to see a substantial degree of
improvement in muscle-related parameters in both
groups, and indeed we did. These findings are consistent
with numerous studies which have measured adaptation
to strength training programs in the absence of any sup-
plementation [33]. The focal question that we sought to
examine in this research is related to whether ashwa-
gandha supplementation would magnify these adapta-
tions. The adaptations were found to be statistically
significantly greater, at a p-value threshold of 0.05, with
ashwagandha supplementation than under placebo for
all parameters (muscle strength, muscle size and body
fat percentage, testosterone, and muscle recovery) except
for thigh muscle size, though some effects were mar-
ginal. Increased recovery from muscle damage has the
practical implication that it allows one to resume resist-
ance training more quickly, thereby increase the volume
of training per unit time and thereby potentially achieve
Table 3 Muscle size
Treatment group mean (SD) Placebo group mean (SD) Between group comparison
(p-values)
Sample size (n) n=25 n=25
Thigh (cm
2
) Pre intervention 107.84 (24.61) 111.18 (17.15) 0.58
Post intervention 116.56 (26.04) 117.40 (19.96) 0.9
Change 8.71 (10.06); 95 % CI: 4.56, 12.87** 6.22 ( 8.76); 95 % CI: 2.61, 9.84* 0.36
Arm (cm
2
) Pre intervention 51.96 (10.88) 53.13 (14.84) 0.75
Post intervention 60.85 (13.23) 58.43 (17.66) 0.59
Change 8.89 (4.71); 95 % CI: 6.95, 10.84** 5.30 ( 4.74); 95 % CI: 3.34, 7.25** 0.01
Chest (cm) Pre intervention 101.40 (11.22) 101.16 (8.93) 0.93
Post intervention 104.77 (11.09) 102.58 (8.76) 0.44
Change 3.37 ( 1.89); 95 % CI: 2.59, 4.15** 1.43 (1.45); 95 % CI: 0.83, 2.02** 0.0002
*=p< 0.01; ** = p< 0.001 within group comparison
Table 4 Body fat percentage
Treatment group Placebo Between group
comparison
Mean (SD) Group mean (SD) (p-values)
Sample
size (n)
n=25 n=25
Pre intervention 21.60 (3.91) 22.01 (3.37) 0.7
Post intervention 18.13 (3.13)** 20.48 (1.85)* 0.003
Change −3.47 (3.58); 95 %
CI: -4.95, -1.99**
−1.52 (2.58); 95 %
CI: -2.59, -0.46*
0.03
*=p< 0.01; ** = p< 0.001 within group comparison
Table 5 Serum testosterone level (ng/dL)
Treatment
group
Placebo
group
Between
group
comparison
Mean (SD) Mean (SD) (p-values)
Sample
size (n)
n=25 n=25
Pre intervention 630.45 (231.88) 675.12 (157.02) 0.43
Post intervention 726.64 (171.55)** 693.12 (115.04) 0.42
Change 96.19 (100.14); 95 %
CI: 54.86, 137.53**
18.00 (81.94); 95 %
CI: -15.83, 51.82
0.004
** = p< 0.001 within group compari son
Wankhede et al. Journal of the International Society of Sports Nutrition (2015) 12:43 Page 7 of 11
greater gains per unit time. Our basic results are consist-
ent with the findings of previous human studies with ash-
wagandha [8, 9, 28, 29, 52] in demonstrating gains in
muscle strength, body composition and testosterone,
though these other studies do not follow these parameters
all in a single clinical trial or in conjunction with a resist-
ance training program. The ashwagandha extract was tol-
erated very well at the study dose with no side effects
reported. This good safety profile of ashwagandha is con-
sistent with reports from previous studies [8, 9, 28, 29,
52].
There are also studies considering the use of other
adaptogenic herbs like Rhodiola rosea,Eleutherococcus
senticosus,Schisandra chinensis and ginseng toward
physical performance. One study [53] gave evidence that
Rhodiola rosea supplementation can improve endurance
and reduce time to exhaustion. A review of Russian re-
search [15] identifies human studies that show improved
physical and mental performance from Schisandra supple-
mentation. It is suggested that [15] Schisandra supple-
mentation can help elite athletes adapt to high physical
intensities. More study of the use of adaptogen herbs in
the aid of muscle strength and recovery is needed.
There are several mechanisms of action that could
have contributed to the positive effects of ashwagandha
supplementation on resistance training and performance
improvements in this study. These can be viewed from two
perspectives: muscle development and muscle recovery.
Muscle development
The ability to lift weights is a function of (a) muscle size,
(b) energy production and (c) the nervous system’s
Table 6 Muscle recovery: increase of serum creatine kinase from hour 24 to hour 48 after end of exercising (U/L)
Treatment group Placebo group Between group comparison
Mean (SD) Mean (SD) (p-values)
Sample size (n) n=25 n=25
Pre intervention 1478.88 (239.60) 1406.52 (264.45) 0.31
Post intervention 16.20 (9.47)** 99.04 (16.77)** <0.0001
Change −1462.68 (233.57); 95 % CI: -1559.09,-1366.27** −1307.48 (253.54); 95 % CI: -1412.14, -1202.82** 0.03
** = p< 0.001 within group compari son
Fig. 2 The effect of Ashwagandha treatment in muscle strength [abench press 1 RM, bleg extension 1RM] and muscle size in cthigh, darm
and eChest
Wankhede et al. Journal of the International Society of Sports Nutrition (2015) 12:43 Page 8 of 11
ability to recruit muscles and coordinate them to gener-
ate the required force. Muscle size is a function of
muscle growth, which is affected by two of ashwagand-
ha’s effects: (i) increase in testosterone, which leads to
muscle growth and (ii) decrease in the levels of cortisol,
which as a catabolic agent detracts from muscle mass. In
terms of energy production, ashwagandha (i) can have
beneficial effects on mitochondrial energy levels and
functioning and reduce the activity of the Mg2
+ -dependent ATPase enzyme responsible for the break-
down of ATP [54], and (ii) can increase creatine levels
that can in turn lead to ATP generation [8]. Finally, the
effects of ashwagandha on the nervous system as anti-
anxiety agent and in promoting focus and concentration
[28] may translate to better coordination and recruit-
ment of muscles. The reason for the lack of an effect on
thigh size is not clear. Longer term studies are needed to
shed light on this, as are studies looking at markers in
the local environment of these muscles to rule out any
biochemical anomalies as contributing factors.
Muscle recovery
In the present study, more rapid recovery from muscle
damage under supplementation with ashwagandha was
demonstrated by monitoring creatine kinase. The faster
recovery could be due to a number of mechanisms, or
more likely their synergistic effects, as mediated by the
various extract components, such as antioxidant effects
to combat free radical damage both at the muscle and
central nervous system levels, anti-inflammatory and
analgesic effects and reduction in lactic acid and blood
urea nitrogen [4–6]. In that vein, muscle soreness is a
common occurrence following exercise for those less
accustomed to physical activity. Delayed onset muscle
soreness (DOMS) presents between 24 and 48 h after
exercise as tenderness to palpation, and/or movement
accompanied by decreases in flexibility and maximal vol-
untary force production. This soreness can inhibit full
and proper exercise. Thus, a reduction in DOMS as a
consequence of ashwagandha’s effect on reduced muscle
injury would counteract this negative consequence.
Conclusion
This study confirms previous data regarding the adapto-
genic properties of ashwagandha and suggests it might
be a useful adjunct to strength training. This study has
the following limitations which should lead us to inter-
pret the findings with some caution: the subjects are
untrained and moderately young, the sample size of 50
is not large and the study period is of duration only 8
weeks. Research studying the possible beneficial effects
of ashwagandha needs to be conducted for longer pe-
riods of time and for different populations including
females and older adults of both genders.
Competing interests
The authors declare that there is no conflict of interests regarding the
publication of this paper.
Authors’contributions
SW and DL developed the clinical trial design and the resisitance training
protocol. They carried out the data collection in collaboration with KJ and
SS. SW, DL, KJ and SS oversaw the data treatment and data analysis. SB
contributed to the writing, the presentation, the bibliography and managed
correspondence. All authors were involved in the writing and drafting, and
all read and approved the final manuscript.
Acknowledgments
The authors thank Shri Kartikeya Pharma and Ixoreal BioMed of Los Angeles,
California, USA for supplying the KSM-66 high-concentration root extract
used in the study treatment.
Author details
1
Sports Medicine, SrimatiKashibaiNavale Medical College, Pune, India.
2
Department of Pharmacology, BVDU Dental College & Hospital, Navi
Mumbai, India.
3
Department of Pharmacology, BharatiVidyapeeth Medical
College & Hospital, Sangli, India.
4
Department of Clinical Pharmacology,
Grant Government Medical College, SirJamshedjeeJeejeebhoy Group of
Hospitals, Mumbai, India.
5
Department of Pharmaceutical Technology, NSHM
Knowledge Campus, 124 B.L. Saha Road, Kolkata 700053, India.
Received: 13 July 2015 Accepted: 16 November 2015
Fig. 3 The effect of Ashwagandha treatment in aserum testosterone and bserum creatine kinase level
Wankhede et al. Journal of the International Society of Sports Nutrition (2015) 12:43 Page 9 of 11
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