Effects of Eurycoma Longifolia Jack Supplementation Combined with Resistance Training on Isokinetic Muscular Strength and Power, Anaerobic Power, and Urinary Testosterone: Epitestosterone Ratio in Young Males

Abstract

Introduction: This study investigated the effects of resistance training and Eurycoma longifoliaJack supplementation on isokinetic muscular strength and power, Wingate anaerobic power, and testosterone: epitestosterone (T/E) ratio in young males. Methods: Forty young males were weight‑matched and assigned into four groups: control (C), Eurycoma longifolia jack (ElJ), resistance training (RT), and Eurycoma longifolia Jack plus resistance training group (ElJ & RT). Participants in ElJ and ElJ & RT groups consumed 200 mg Eurycoma longifolia Jack daily, whereas participants in the C and RT groups consumed placebo capsules daily for 8 weeks. Resistance training program which consisted of 10 different exercises was conducted three times per week for 8 weeks. Participants’ isokinetic muscular strength and power, anaerobic power, and urinary TE ratio were measured before and after the intervention period. This is a randomized
placebo‑controlled intervention study. Paired t‑test and one‑way analysis of variance were used for statistical analysis. Results: The mean average power of knee flexion at 300°/s in the RT and ElJ & RT groups was significantly (P < 0.05) higher in the posttest compared with pretest. Wingate relative peak power in the RT group increased significantly (P < 0.05) compared with respective pretest value, whereas peak power in the combined ElJ & RT group was significantly (P < 0.05) higher in posttest compared with pretest. There was no significant difference in T/E ratio between pre‑ and posttests in all the groups.
Conclusions: The prescribed resistance training program, either with or without ElJ supplementation, improved isokinetic power of the lower limb. Resistance training alone improved relative anaerobic power, whereas combined Eurycoma longifolia Jack and
resistance training improved peak power output. ElJ consumption of 200 mg daily for 8 weeks did not affect the urinary T/E ratio.

Full text

1© 2019 International Journal of Preventive Medicine | Published by Wolters Kluwer ‑ Medknow
Introduction
Eurycoma longifolia Jack is a tall,
single‑stemmed, slender, shrubby,
slow‑growing tree, and can be found on
sandy soil in Malaysia.[1] It is locally
known as “Tongkat Ali” and has been
described as the “Malaysian ginseng” due
to its popularity among various ethnic
groups as a treatment for various diseases
and enhancing health.[2]
Eurycoma longifolia Jack contains mainly
quassinoids, and other active compounds
such as tirucallene‑type triterpenes,
squalene derivatives, biphenyl‑neo‑lignans,
anthraquinones, canthin‑6‑one alkaloids,
Address for correspondence:
Dr. Chee Keong Chen,
Exercise and Sports Science
Programme,
School of Health Sciences,
Universiti Sains
Malaysia, 16150 Kubang
Kerian, Kota Bharu, Kelantan,
Malaysia.
E‑mail: ckchen@usm.my
Abstract
Introduction: This study investigated the effects of resistance training and Eurycoma longifolia
Jack supplementation on isokinetic muscular strength and power, Wingate anaerobic power, and
testosterone: epitestosterone (T/E) ratio in young males. Methods: Forty young males were
weight‑matched and assigned into four groups: control (C), Eurycoma longifolia jack (ElJ),
resistance training (RT), and Eurycoma longifolia Jack plus resistance training group (ElJ & RT).
Participants in ElJ and ElJ & RT groups consumed 200 mg Eurycoma longifolia Jack daily,
whereas participants in the C and RT groups consumed placebo capsules daily for 8 weeks.
Resistance training program which consisted of 10 different exercises was conducted three times
per week for 8 weeks. Participants’ isokinetic muscular strength and power, anaerobic power, and
urinary TE ratio were measured before and after the intervention period. This is a randomized
placebo‑controlled intervention study. Paired t‑test and one‑way analysis of variance were used for
statistical analysis. Results: The mean average power of knee exion at 300°/s in the RT and ElJ
& RT groups was signicantly (P < 0.05) higher in the posttest compared with pretest. Wingate
relative peak power in the RT group increased signicantly (P < 0.05) compared with respective
pretest value, whereas peak power in the combined ElJ & RT group was signicantly (P < 0.05)
higher in posttest compared with pretest. There was no signicant difference in T/E ratio between
pre‑ and posttests in all the groups. Conclusions: The prescribed resistance training program, either
with or without ElJ supplementation, improved isokinetic power of the lower limb. Resistance
training alone improved relative anaerobic power, whereas combined Eurycoma longifolia Jack and
resistance training improved peak power output. ElJ consumption of 200 mg daily for 8 weeks did
not affect the urinary T/E ratio.
Keywords: Anaerobic power, Eurycoma longifolia Jack, isokinetic strength, resistance training,
testosterone:epitestosterone ratio
Effects of Eurycoma Longifolia Jack Supplementation Combined
with Resistance Training on Isokinetic Muscular Strength and Power,
Anaerobic Power, and Urinary Testosterone: Epitestosterone Ratio in
Young Males
Original Article
Chee Keong
Chen1,2,
Foong Kiew Ooi1,2,
Nurul Ain Abu Kasim1,
Mohd Asnizam
Asari3
1Sports Science Unit, School
of Medical Sciences, Kubang
Kerian, Kelantan, Malaysia,
2Exercise and Sports Science
Programme, School of
Health Sciences, Kubang
Kerian, Kelantan, Malaysia,
3Department of Anatomy, School
of Medical Sciences, Universiti
Sains Malaysia, Kubang Kerian,
Kelantan, Malaysia
How to cite this article: Chen CK, Ooi FK,
Abu Kasim NA, Asari MA. Effects of Eurycoma
longifolia Jack supplementation combined
with resistance training on isokinetic muscular
strength and power, anaerobic power and urinary
testosterone: Epitestosterone ratio in young males.
Int J Prev Med 2019;10:118.
This is an open access journal, and arcles are distributed
under the terms of the Creave Commons Aribuon-
NonCommercial-ShareAlike 4.0 License, which allows others
to remix, tweak, and build upon the work non-commercially,
as long as appropriate credit is given and the new creaons
are licensed under the idencal terms.
For reprints contact: reprints@medknow.com
β‑carboline alkaloids, and dimeric
dihydrobenzofuran.[3] Eurycoma longifolia
Jack possesses medicinal properties
such as antidiabetic and[4] antibacterial,[5]
increases sexual motivation in rats,[6]
anxiolytic,[7] antimalarial, cytotoxic,
antiulcer and antipyretic,[8] and
antitumor.[9] Eurycoma longifolia Jack has
also been shown to increase testosterone
levels[10] and possesses antioxidant
properties.[11‑13] In addition, it was reported
that supplementation of Eurycoma
longifolia Jack at a dosage of 400 mg/
day for 6 weeks did not affect the urinary
testosterone: epitestosterone (T/E) ratio in
male recreational athletes.[14]
Access this article online
Website:
www.ijpvmjournal.net/www.ijpm.ir
DOI:
10.4103/ijpvm.IJPVM_404_17
Quick Response Code:
[Downloaded free from http://www.ijpvmjournal.net on Wednesday, July 17, 2019, IP: 202.170.48.10]

Chen, et al.: Eurycoma longifolia Jack and resistance training on muscular tness and testosterone: epitestosterone ratio
International Journal of Preventive Medicine 2019, 10: 1182
Several studies have been carried out to investigate
the effects of Eurycoma longifolia Jack on sports
performance. Ooi et al. (2001) investigated the effects
of an herbal drink containing Eurycoma longifolia Jack
on cycling performance among young trained male
cyclists.[15] This study demonstrated that there was no
signicant improvement in endurance cycling performance
following supplementation of an herbal drink with a dosage
of 0.1 mg of Eurycoma longifolia Jack per 100 mL of
water. Thus, the authors speculated that this nding could
be attributed to inadequate concentration of Eurycoma
longifolia Jack that was consumed by the participants at
20 min intervals during the trials.[15] Muhamad et al. (2010)
investigated the effects of Eurycoma longifolia Jack on
endurance running performance with a higher dosage
of this herb and a longer supplementation period in
recreational athletes.[16] However, they also reported that
Eurycoma longifolia Jack at a dosage of 150 mg daily
for 7 days had no benecial effects on endurance running
performance. Nevertheless, it has been previously reported
that Eurycoma longifolia Jack supplemented at a dosage
of 150 mg for 5 weeks increases the muscular strength of
healthy male adults.[17]
Resistance training has been prescribed for improving
health, tness, and also in rehabilitation.[18,19] Resistance
training has been shown to increase muscular strength
in both children and adolescents, and this increase was
attributed to increased neuromuscular activation and
co‑ordination.[20] A couple of studies carried out in our
laboratory have also demonstrated that resistance training
using dumbbells and elastic bands elicited improvement
in isokinetic muscular power in healthy male adults[21] and
in adolescent athletes.[22] Ooi et al. (2015) investigated the
combined effects of Eurycoma longifolia Jack and a circuit
training program on muscular strength and power in older
adult men around 46 years of age. It was reported that the
combined circuit training program and Eurycoma longifolia
Jack supplementation at a daily dosage of 400 mg for
8 weeks elicited a higher muscular strength and power
compared with circuit training alone.[21]
Thus, the objective of this study was to investigate the
combined effects of a resistance training program and
Eurycoma longifolia Jack on isokinetic muscular strength
and power, anaerobic power, and urinary T/E ratio among
younger males.
Methods
In all, 44 physically healthy males, between 19 and 25 years
of age were recruited in this randomized placebo‑controlled
intervention study. CONSORT diagram showing the ow
of participants through each stage of this study is illustrated
in Figure 1. All participants were weight‑matched and then
randomly assigned into four groups, with 11 participants
per group. The participants were given a detailed
explanation about the objectives, procedures, benets,
risks, and possible discomforts experienced in this study
before signing the informed consent forms. This study
was approved by the Human Research Ethics Committee,
Universiti Sains Malaysia.
The participants were divided into four groups: (i) control
group supplemented with placebo (C), (ii) Eurycoma
longifolia Jack supplemented group (ElJ), (iii) resistance
training group supplemented with placebo (RT), and (iv)
resistance training group supplemented with Eurycoma
longifolia Jack (ElJ & RT). Participants in the ElJ group
consumed 200 mg of Eurycoma longifolia Jack daily for
a total of 8 weeks. An earlier study using a daily dosage
of 150 mg of Eurycoma longifolia Jack did not elicit any
signicant improvement in endurance running performance.
Thus, a higher dosage of 200 mg of Eurycoma longifolia
Jack and a longer duration of 8 weeks were used for this
study.[16] Participants in the RT group were required to
undergo a resistance training program for 8 weeks with
three sessions per week and 1 h per session. Participants
in the ElJ & RT group were also required to undergo the
same resistance training program and consumed 200 mg of
Eurycoma longifolia Jack daily for 8 weeks. Participants
in the C and RT groups were supplemented with placebo
capsules daily for 8 weeks. These capsules were similar in
color and texture but contained maltodextrin.
The resistance training program consisted of 10 stations of
different activities using either elastic bands or dumbbells.
The types of activity were heel raise with dumbbells, lateral
raise with elastic band, leg curls with elastic band, bicep
AllocationFollow up Enrollment
Analysis
Assessed for eligibility (n = 55)
Excluded (n = 11)
• Not meeting inclusion
criteria (n = 5)
• Refused to participate (n = 3)
• Other reasons (n = 3)
Randomized (n = 44)
Allocated to control group
(n = 11)
Received allocation (n = 11)
Did not receive allocation
(n = 0)
Allocated to 3 intervention
groups (n = 33)
Received allocation (n = 33)
Did not receive allocation (n = 0)
Lost to follow up (n = 1)
Discontinued intervention
(n = 0)
Lost to follow up (n = 1)
Discontinued intervention (n = 2)
(did not complete resistance
training program)
Analyzed (n = 10)
Excluded from analysis (n = 1)
Analyzed (n = 30)
Excluded from analysis (n = 3)
(personal reasons)
Figure1:CONSORTdiagramshowingtheowofparticipantsthrougheach
stage of the randomized trial in this study
[Downloaded free from http://www.ijpvmjournal.net on Wednesday, July 17, 2019, IP: 202.170.48.10]

Chen, et al.: Eurycoma longifolia Jack and resistance training on muscular tness and testosterone: epitestosterone ratio
International Journal of Preventive Medicine 2019, 10: 118 3
curls with dumbbells, leg abduction with elastic band,
front raise with dumbbells, knee extension with elastic
band, arm extension with dumbbells, half squat with elastic
band, and standing chest y with dumbbells. The number
of repetitions for exercises with dumbbells was 10, while
exercises with elastic band were 15. The weight of the
dumbbells was between 3 and 12 kg while the elastic bands
were color‑coded in terms of its elasticity. Participants were
given 1 min rest between stations before continuing with
the next station in the circuit. A 3‑min rest was given to
the participants before they perform a subsequent set. The
participants were required to complete three sets of this
circuit and this training program was conducted three times
a week for 8 weeks.
Prior to the supplementation regimen and following
8 weeks of experimental period, urine samples were
collected for the analysis of urinary level of T/E ratio.
Determination of T:E ratio was performed by the staff of
the Doping Control Centre, Universiti Sains Malaysia,
Penang. Quantication of T:E ratio was determined by
gas chromatography‑mass spectrometry (GC/MS). Free
and conjugated T and E were extracted by solid phase
extraction using the Nexus (Varian) column combined
with liquid–liquid extraction using tert‑butyl methyl ether,
followed by hydrolysis using enzyme β‑glucuronidase
from Escherichia coli K12 (Roche Diagnostics, Mannheim,
Germany); extracts were then derivatized with activated
N‑methyl‑N‑trimathylsilyl‑triuoroacetamide. Calibration
of T was performed using concentration levels of between
2 and 80 ng/mL while the values for E were between 2 and
20 ng/mL. Selected ion monitoring mode with electron
ionization on the GC/MS was used for both identication
and quantication of both T and E.
Anthropometric measurements were recorded at pre‑ and
postexperimental periods. Body weight, height, body mass
index and percent body fat measurements were measured
using an electronic weighing machine (Seca 220, Germany)
and body composition analyzer (Tanita® TBF‑410, Japan).
An isokinetic dynamometer (Biodex Medical System 3
Pro, NY, USA) was used to measure isokinetic muscular
strength and power of the participants. Two different
angular velocities (60°/s and 300°/s) were used to measure
isokinetic knee and shoulder exion and extension
muscular strength and power of the participants before and
after 8 weeks of experimental intervention.
Participants’ anaerobic tness was determined through
Wingate anaerobic test. Wingate anaerobic test is a 30‑s
all‑out exhaustive ergometer test where the participants
pedaled on a cycle ergometer (Lode Groningen, The
Netherlands) against a resistance. All participants
were required to maintain 1 min of cycling at 50 W at
60 rpm prior to the 30‑s actual test. During the 30‑s test,
participants were encouraged verbally by the researcher to
pedal as fast as they possibly could. Participants remained
seated for the entire duration of the test to avoid unfair
mechanical advantage due to involvement of other muscle
groups which might skew the results.
Statistical analysis was carried out using Statistical
Package for Social Sciences (SPSS) version 18.0 (SPSS
Inc., Chicago, Illinois, USA). Normality of all the data was
examined with Kolmogrov–Sminov test. Data of age, body
height, body weight, and body fat percentage were analyzed
by descriptive statistics. Paired t‑test and one‑way analysis
of variance were performed to determine the signicance
of the differences between and within groups, respectively.
The difference was considered statistically signicant at
P < 0.05. All values are presented as mean ± standard
deviation.
Results
Physical characteristics of the participants
One participant from each group withdrew from the study
due to personal reasons. Thus, data presented are based
on 40 participants who successfully completed the study.
Anthropometric data obtained from all participants (n = 40)
are summarized in Table 1. There were no signicant
differences in age, body weight, and height between
groups prior to experimental study. However, there was a
signicant difference in body fat percentage between ElJ
and ElJ & RT groups even though the participants were
weight‑matched [Table 1].
Isokinetic peak torque of shoulder extension and exion
at 60°/s
At pretest, there were no signicant differences in isokinetic
peak torque of shoulder extension and exion at 60°/s in
ElJ, RT, and ElJ & RT groups compared with C group. At
posttest also, there were no signicant differences in ElJ,
RT, and combined ElJ & RT groups compared with the C
group in peak torque of shoulder extension and exion at
60°/s [Figure 2].
Isokinetic average power of shoulder extension and
exion at 300°/s
At pretest, no signicant differences in isokinetic average
power of shoulder extension and exion at 300°/s were
found between ElJ, RT, and combined ElJ & RT groups
compared with C group. After 8 weeks of intervention,
there were no signicant changes in these parameters
in ElJ, RT, and combined ElJ & RT compared with C
group [Figure 2].
Isokinetic peak torque of knee extension and exion at
60°/s
There were also no signicant differences in isokinetic peak
torque of knee extension and exion at 60°/s at pre‑ and
posttest between all the groups: C, ElJ, RT, and combined
ElJ & RT [Figure 3].
[Downloaded free from http://www.ijpvmjournal.net on Wednesday, July 17, 2019, IP: 202.170.48.10]

Chen, et al.: Eurycoma longifolia Jack and resistance training on muscular tness and testosterone: epitestosterone ratio
International Journal of Preventive Medicine 2019, 10: 1184
Isokinetic average power of knee extension and exion
at 300°/s
There were no signicant differences in average power
of knee extension at 300°/s between groups ElJ, RT, and
combined ElJ & RT compared with C group at pre‑ and
postintervention [Figure 3]. There was no signicant
difference in isokinetic average power of knee exion at
300°/s between ElJ, RT, and combined ElJ & RT groups
when compared with C group. However, after 8 weeks
of intervention, the mean average power of knee exion
at 300°/s in RT and ElJ & RT groups was signicantly
higher (P < 0.05) in posttest compared with pretest values.
Wingate anaerobic power, Wingate anaerobic capacity,
and anaerobic peak power
Anaerobic power in ElJ, RT, and ElJ & RT groups was not
signicantly different compared with group C at pre‑ and
posttests. After 8 weeks of intervention, anaerobic power in
the RT group increased signicantly (P < 0.05) compared
with its pretest value [Figure 4]. Anaerobic capacity was
not signicantly different between ElJ, RT, and ElJ &
RT groups compared with the control group at pre‑ and
postintervention [Figure 4]. There was no signicant
difference in peak power between ElJ, RT, and ElJ & RT
groups compared with group C [Figure 4]. After 8 weeks
of intervention, anaerobic peak power in the combined ElJ
& RT group increased signicantly (P < 0.05) compared
with its pretest value.
Urinary level of T/E ratio
There were no signicant differences in ElJ, RT, and
combined ElJ & RT groups compared with C group in
urinary level of T/E at pre‑ and posttests [Figure 5].
Discussion
Following 8 weeks of intervention, we observed signicant
increases in isokinetic average power of knee exion at
300°/s in the resistance training and combined ElJ & RT
Table 1: Physical characteristics of the participants
Parameters Control (C) ElJ RT ElJ & RT ANOVA (P)
Age (years) 22.3±0.7 21.2±0.8 20.2±0.6 20.3±0.4 >0.05
Height (cm) 164.8±1.7 164.4±2.1 167.5±2.2 167.3±1.7 >0.05
Weight (kg) 66.4±4.0 67.4±4.5 64.7±3.6 64.3±3.0 >0.05
Body fat percentage (%) 22.6±2.6 25.3±2.6 20.9±2.0 18.2±1.7* <0.05
Body mass index (kg/m2)24.3±1.1 24.8±1.4 23.1±1.2 22.3±0.9 >0.05
*Signicantly different from ElJ group (P<0.05)
Figure2:Shoulderexion(a)andextension(b)peaktorqueat60°/sandshoulderexion(c)andextension(d)averagepowerat300°/satpre‑andposttests
ab
cd
[Downloaded free from http://www.ijpvmjournal.net on Wednesday, July 17, 2019, IP: 202.170.48.10]

Chen, et al.: Eurycoma longifolia Jack and resistance training on muscular tness and testosterone: epitestosterone ratio
International Journal of Preventive Medicine 2019, 10: 118 5
groups. For the control and ElJ supplemented groups, there
were no changes from pre‑ to postintervention in both
isokinetic muscular strength and average power. These
data demonstrated that both resistance training and when
combined with Eurycoma longifolia Jack supplementation
elicited increases in participants’ power of the lower limb.
It is postulated that improvement in muscular power
from resistance training in this study may be attributed
to exercise acting as a stimulus to initiate the relative
process of muscular growth. This in turn triggers protein
signaling to activate and stimulate synthesis of muscle
protein leading to increased muscle strength.[23] Resistance
training has been shown to increase the size and number of
myobrils, resulting in hypertrophy of muscle bers.[24]
The increase in isokinetic strength and power following
resistance training in this study also correlates with another
study which examined the effects of training with elastic
bands on different strength and power adaptations compared
with traditional weight training using free weights.[25] In that
study, 44 collegiate athletes were recruited and randomly
Figure3: Kneeexion(a) andextension (b)peaktorqueat60°/s andknee exion(c)and extension(d) averagepowerat300°/sat pre‑and posttests.
*Signicantlydifferentfromtherespectivepretestvalues(P<0.05)
ab
cd
Figure4:Wingaterelative anaerobicpower(a),Wingateanaerobic capacity(b),andWingate peakpoweroutput(c)atpre‑andposttests.*Signicantly
differentfromtherespectivepretestvalue(P<0.05)
abc
[Downloaded free from http://www.ijpvmjournal.net on Wednesday, July 17, 2019, IP: 202.170.48.10]

Chen, et al.: Eurycoma longifolia Jack and resistance training on muscular tness and testosterone: epitestosterone ratio
International Journal of Preventive Medicine 2019, 10: 1186
stratied into groups based on their respective sports.[25]
The participants were tested prior to and after 7 weeks of
resistance training on multiple dependent measures which
include 1RM back squat, 1RM bench press, average power,
and peak power output in the vertical jump. The results
of that study indicated that signicant differences were
observed between the experimental group (participants who
trained with elastic bands for 7 weeks) and control group,
suggesting that this type of training may offer an effective
means to enhance strength and functional performance.
Although this study failed to demonstrate statistically
signicant improvement in all the isokinetic muscular
strength and power measured, there was a trend of
increased strength and power in some of the parameters
in the RT and ElJ & RT groups. Thus, future studies
with supplementation of ElJ at higher dosage or in
different form of ElJ might be warranted. ElJ can be
obtained either in the form of raw crude powder where
the root is dried and grinded without involving any other
chemical processing procedures[26] or in capsules which
contain raw crude powder or standardized ElJ extract
which is prepared by separating the active ingredients
and subsequently concentrating it to a standard
level.[26] Eurycoma longifolia Jack is also available as
an additive brewed with coffee and canned as processed
drinks.[2] Therefore, it is possible that each form might
have different absorption rate which may affect the
bioavailability of its active ingredients. Ooi et al. (2010)
reported that combined Eurycoma longifolia Jack
supplementation and a circuit training program increases
knee strength and power, shoulder exion, and extension
power. However, this study used a higher daily dosage
of 400 mg Eurycoma longifolia Jack for 8 weeks, and
it was reported that there was a synergistic effect of the
combined Eurycoma longifolia Jack supplementation
and the circuit training program on isokinetic muscular
strength and power.[21] The synergistic effect of Eurycoma
longifolia Jack and resistance training was not observed
in this study, and this could be attributed to the different
dosage of Eurycoma longifolia Jack consumed by the
participants, differences in the types of exercises in the
training program, and the age of the participants.
For the Wingate test, our ndings indicated that relative
peak power in the RT group was signicantly higher
compared with the other experimental groups. However,
anaerobic capacity was not different in any of the groups.
As for the peak power, it was signicantly higher in
combined ElJ & RT group after 8 weeks of intervention
period compared with its baseline value. According
to Malina et al. (2004), anaerobic peak power reects
short‑term anaerobic performance, whereas mean anaerobic
capacity reects intermediate‑term performance.[27] In
determining the anaerobic performance, factors that play
crucial roles are morphological (muscle architecture and
ber type), physiological (efciency of metabolic pathway),
biochemical (substrate availability and accumulation
of reaction products), and neuromotor (motor skill and
motor unit recruitment). The amount of muscle mass,
especially the thigh muscle cross‑sectional area, has a
direct inuence on the absolute anaerobic power output
that can be generated. Chromiak et al. also showed that the
relative anaerobic power increased signicantly following a
4 days per week, 10 weeks of periodized strength training
program.[28] The resistance used in that study was such
that the participants found it very difcult to complete the
nal repetitions of the nal set (three to four sets, 3–10
repetitions).[28] Therefore, it was possible that heavier
resistance used in that study could possibly contribute to a
signicant increase in the relative anaerobic power.
Eurycoma longifolia Jack is popular due to its aphrodisiac
property as it stimulates the production or action of androgen
hormones, especially testosterone. In addition, human trials
have also demonstrated that ElJ supplementation increases
the level of testosterone.[10] The possible mechanism
on how extracts of Eurycoma longifolia Jack boost
testosterone levels was attributed to the active compounds
contained in Eurycoma longifolia Jack. A highly puried
extract of Eurycoma longifolia Jack has been shown to
have antiestrogenic effect compared with tamoxifen. This
antiestrogenic effect of Eurycoma longifolia Jack in turn
works by increasing testosterone levels as the same way
selective estrogen receptor modulators work. Inhibition of
the estrogen receptor in the hypothalamus or as aromatase
inhibitors works on changing the androgen: estrogen ratio
to favor androgen‑lowering estrogen. When circulating
estrogen is lowered, the body compensates by elevating
androgen output.
The result of this study demonstrated that there were no
signicant effects of intervention on urinary T/E ratio
in all the experimental groups. The urinary T: E ratios
of all the participants prior to and after engaging in the
resistance training and consuming Eurycoma longifolia
Jack supplements were below the threshold limit of 4:1 that
was set as the cut‑off ratio by IOC. The guidelines given
by World Anti‑Doping Agency stated that if an athlete has
a urinary level for T: E ratio more than 4:1, the sample
will be submitted for determination of 13C/12C ratio using
Figure5:Urinarytestosterone:epitestosteroneratio
[Downloaded free from http://www.ijpvmjournal.net on Wednesday, July 17, 2019, IP: 202.170.48.10]

Chen, et al.: Eurycoma longifolia Jack and resistance training on muscular tness and testosterone: epitestosterone ratio
International Journal of Preventive Medicine 2019, 10: 118 7
isotopic ratio mass spectrometry. This study nding was in
line with an earlier study carried out by Chen et al. (2014)
who reported that there was no signicant change in T:E
ratio following 6‑week supplementation of either ElJ or
placebo.[14]
Conclusions
The prescribed resistance training program for 8 weeks,
either with or without ElJ supplementation, seems to be
benecial in improving isokinetic muscular power of the
lower limb. In addition, resistance training alone may
elicit improvement in anaerobic relative power, whereas
combined Eurycoma longifolia Jack supplementation and
resistance training may have potential benet to improve
peak power output. Consuming 200 mg of Eurycoma
longifolia Jack daily for 8 weeks does not affect the
urinary T/E ratio. Hence, we conclude that the prescribed
resistance training program alone or in combination with
Eurycoma longifolia Jack can be recommended to athletes
who want to improve the power of their lower limb.
However, more studies with longer duration, different
dosages of Eurycoma longifolia Jack, and different types
of resistance training program are warranted to conrm its
efcacy.
Acknowledgments
The authors wish to express their sincere gratitude to all
the participants who have participated in this study for
their commitment and patience during the study period.
They also wish to extend their appreciation to the staff of
Sports Science Laboratory for their kind assistance and
help throughout the study. The authors sincerely thank
Biotropics Malaysia Berhad for supplying the supplements
and placebo for this study and the staff from Doping
Control Centre (USM), for analyzing urinary T/E ratio.
Ethical approval
This study was approved by the Human Research Ethics
Committee, School of Medical Sciences, Universiti Sains
Malaysia, Kelantan, Malaysia.
Declaration of authorship
All the authors were involved in this study. This research
project was proposed and designed by CKC and FKO. This
study was carried out by AKNA under the supervision of
CKC, FKO, and AMA. This article was initiated by AKNA
and subsequently corrected and revised by CKC, FKO, and
AMA. FKO performed statistical analysis and interpretation
of the results. Article preparation was undertaken by CKC,
FKO, AKNA, and AMA.
Financial support and sponsorship
Nil.
Conicts of interest
There are no conicts of interest.
Received: 19 Sep 18 Accepted: 11 Jan 19
Published: 05 Jul 19
References
1. Ang HH, Cheang HS, Yusof APM. Effects of Eurycoma
longifolia Jack (Tongkat Ali) on the initiation of sexual
performance of inexperienced castrated male rats. Exp Anim
2000;49:35‑8.
2. Jaganath IB, Ng LT. Herbs. The Green Pharmacy of Malaysia.
Kuala Lumpur: Vinpress and Malaysia Agricultural Research and
Development Institute; 2000. p. 95‑9.
3. Bhat R, Karim AA. Tongkat Ali (Eurycoma longifolia Jack):
A review on its ethnobotany and pharmacological importance.
Fitoterapia 2010;81:669‑79.
4. Husen R, Pihie AHL, Nallappan M. Screening for
antihyperglycaemic activity in several local herbs of Malaysia.
J Ethnopharmacol 2004;95:205‑8.
5. Farouk AE, Benafri A. Antibacterial activity of Eurycoma
longifolia Jack. A Malaysian medicinal plant. Saudi Med J
2007;28:1422‑4.
6. Ang HH, Sim MK. Eurycoma longifolia increases sexual
motivation in sexually naive male rats. Arch Pharm Res
1998;21:779‑81.
7. Ang HH, Sim MK. Eurycoma longifolia JACK and orientation
activities in sexually experienced male rats. Biol Pharm Bull
1998;21:153‑5.
8. Ang HH, Sim MK. Eurycoma longifolia Jack enhances libido in
sexually experienced male rats. Exp Anim 1997;46:287‑90.
9. Jiwajinda S, Santisopasri V, Murakami A, Kawanaka M,
Kawanaka H, Gasquet M, et al. In vitro anti‑tumor promoting
and anti‑parasitic activities of the quassinoids from Eurycoma
longifolia, a medicinal plant in Southeast Asia. J Ethnopharmacol
2002;82:55‑8.
10. Tambi MIBM, Imran MK, Henkel RR. Standardised water‑
soluble extract of Eurycoma longifolia, Tongkat ali, as
testosterone booster for managing men with late‑onset
hypogonadism? Andrologia 2012;44:226‑30.
11. Tambi MIBM. Standardised water soluble extract of Eurycomal
longifolia (Lj100) on Men’s Health. Int J Androl 2005;28 (Suppl.
1), 27:25‑44.
12. Tambi MIBM, Kadir AA. Eurycoma longifolia jack: A potent
adaptogen in the form of water‑soluble extract with the effects of
maintaining men’s health. Asian J Androl 2006;8(Suppl 1):49‑50.
13. Tambi MIBM. Standardized water soluble extract of Eurycoma
longifolia (LJ199) maintains healthy aging in man. Aging Male
2006;9:53.
14. Chen CK, Mohamad WMZW, Ooi FK, Ismail SB, Abdullah MR,
George A. Supplementation of Eurycoma longifolia jack extract
for 6 weeks does not affect urinary testosterone: Epitestosterone
ratio, liver and renal functions in male recreational athletes.
Open J Prev Med 2014;5:728.
15. Ooi FK, Singh R, Sirisinghe RG, Suen AB, Jamalullail SMS.
Effects of a herbal ergogenic drink on cycling performance in
young cyclists. Malays J Nutr 2001;7:33‑40.
16. Muhamad AS, Keong CC, Kiew OF, Abdullah MR, Lam CK.
Effects of Eurycoma longifolia Jack supplementation on
recreational athletes’ endurance running capacity and physiological
responses in the heat. Int J Appl Sports Sci 2010;22:1‑19.
17. Hamzah S, Yusof A. The ergogenic effects of eurycoma
longifolia jack: A pilot study. Br J Sports Med 2003;37:464‑70.
18. Pearson D, Faigenbaum A, Conley M, Kraemer WJ. The National
Strength and Conditioning Association’s basic guidelines for the
resistance training of athletes. Strength Cond J 2000;22:14.
[Downloaded free from http://www.ijpvmjournal.net on Wednesday, July 17, 2019, IP: 202.170.48.10]

Chen, et al.: Eurycoma longifolia Jack and resistance training on muscular tness and testosterone: epitestosterone ratio
International Journal of Preventive Medicine 2019, 10: 1188
19. American College of Sports Medicine. American College
of Sports Medicine position stand. Progression models in
resistance training for healthy adults. Med Sci Sports Exerc
2009;41:687.
20. Guy JA, Micheli LJ. Strength training for children and
adolescents. J Am Acad Orthop Surg 2001;9:29‑36.
21. Ooi FK, Afah MH, Chen CK, Asnizam AM. Combined effects
of Eurycoma longifolia Jack supplementation and a circuit
training programme on bone metabolism markers, muscular
strength and power and immune functions in adult men. IJERSS
2015;2:1‑10.
22. Teng W, Keong CC, Ghosh AK, Thimurayan V. Effects of a
resistance training programme on isokinetic peak torque and
anaerobic power of 13–16 years old Taekwondo athletes. Int J
Sports Sci Engineer 2008;2:111‑21.
23. McArdle WD, Katch FI, Katch VL. Exercise Physiology: Energy,
Nutrition, and Human Performance. 6th ed. USA: Lippincott
William & Wilkins; 2007.
24. Fahey TD, Insel PM, Roth WT. Fit and Well. Boston: McGraw
Hill; 2013.
25. Anderson CE, Sforzo GA, Sigg JA. The effects of combining
elastic and free weight resistance on strength and power in
athletes. J Strength Cond Res 2008;22:567‑74.
26. Mohd Effendy N, Mohamed N, Muhammad N, Mohamad IN,
Shuid AN. Eurycoma longifolia: Medicinal Plant in the
prevention and treatment of male osteoporosis due to androgen
deciency. Evid Based Complementy Alternat Med 2012. doi:
10.1155/2012/125761.
27. Malina RM, Bouchard C, Bar‑Or O. Growth, maturation, and
physical activity. Human Kinetics. 2nd ed. Champaign, IL, USA:
Human Kinetics; 2004.
28. Chromiak JA, Smedley B, Carpenter W, Brown R, Koh YS,
Lamberth JG, et al. Effect of a 10‑week strength training
program and recovery drink on body composition, muscular
strength and endurance, and anaerobic power and capacity.
Nutrition 2004;20:420‑7.
[Downloaded free from http://www.ijpvmjournal.net on Wednesday, July 17, 2019, IP: 202.170.48.10]