Comparison Between the Eects of Transfer
Energy Capacitive and Resistive Therapy and
Therapeutic Ultrasound on Hamstring Muscle
Shortness in Male Athletes: A Single-Blind
Randomized Controlled Trial
Haniyeh Choobsaz1, Nastaran Ghotbi1 , Pooria Mohamadi1
1 Department of Physiotherapy, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran
GMJ.2023;12:e2981
www.gmj.ir
Correspondence to:
Nastaran Ghotbi, School of Rehabilitation, Tehran Uni-
versity of Medical Sciences, Tehran, Iran.
Telephone Number: +98 21 77535132
Email Address: nghotbi@tums.ac.ir
Received 2023-03-19
Revised 2023-04-28
Accepted 2023-06-19
Abstract
Background: Transfer energy capacitive and resistive (TECAR) therapy (TT) is a newly devel-
oped deep heating therapy that can generate heat within tissues through high-frequency wave
stimulation. Compared to conventional physiotherapy methods, the application of TT especially
in sports rehabilitation is becoming more popular. This study aimed to investigate the compar-
ative eect of TT and therapeutic ultrasound (US) on hamstring muscle shortness. Addition-
ally, the eects of TT with static stretching (SS) were compared with US combined with SS.
Materials and Methods: Totally, 39 male athletes with hamstring shortness were randomly as-
signed into three groups: A, B, and C. Group A received 15 minutes of TT plus SS, while Group
B received 15 minutes of US with SS, and Group C only performed SS. Hamstring exibility
was measured by active knee extension (AKE), passive knee extension (PKE), and the sit and
Reach (SR) tests before the intervention, and following the rst, and third treatment sessions.
Results: The range of motion of the AKE and PKE, and displacement range in the SR test im-
proved signicantly after the rst and third sessions in all three groups (P<0.0001). The improve-
ment of the three exibility indices in the TT group was greater than in the other two groups.
Conclusion: The present study showed that TT could increase the exibility of hamstring mus-
cles more than US therapy. However, TT in combination with SS had a similar eect to SS alone.
[GMJ.2023;12:e2981] DOI:10.31661/gmj.v12i0.2981
Keywords: Hamstring Muscle; Physical Therapy Modalities; Static Stretching; Radiofrequen-
cy Therapy; Diathermy
Introduction
Muscle exibility is an important compo-
nent of normal biomechanical function-
ing in athletes [1]. Insucient muscle exi-
bility may cause musculoskeletal injuries [2].
According to studies, the reduced exibility
of hamstrings inuences athletic performance
and is a risk factor for developing hamstrings
strain [3]. Therefore, the maintenance of the
exibility of hamstrings in athletes is a major
issue in physiotherapy.
Various methods are used to improve the mus-
cle exibility of athletes, including stretching
and thermotherapy [4]. Static stretching (SS),
due to its low risk of inducing injury, is one
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Choobsaz H, et al. Comparison between TECAR Therapy and Ultrasound
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of the most eective techniques to improve
muscle exibility [5, 6]. Thermotherapy is an-
other means of enhancing muscle exibility,
increasing tissue temperature and blood ow
and reducing muscle activity [7, 8]. Deep
heating therapy can be applied through vari-
ous modalities including ultrasound (US) [9],
short-wave diathermy [10], and microwaves
[11] which have been shown to have dierent
clinical eectiveness.
It is believed that deep heating agents can in-
crease the extensibility of collagen bers by
increasing intramuscular temperature [12]. In
this way, more signicant muscle elongation
can be achieved even at lower stretch forces
[13]. Low-frequency continuous therapeutic
US can penetrate deep tissue layers contain-
ing thick muscles to improve muscle exibil-
ity [14, 15].
Recently, Transfer Energy Capacitive and
Resistive (TECAR) therapy (TT) has been
used for clinical purposes as almost a unique
physiotherapy modality [16-18]. It consists
of an electrical current, which induces deep
endogenous heating by a 448 kHz capacitive/
resistive monopolar radiofrequency [19, 20],
and can increase the extensibility of soft tis-
sues and muscle exibility [21, 22]. Ribeiro
et al. assessed the eectiveness of TT in mus-
culoskeletal disorders. They concluded that
this is one of the best modalities of physio-
therapy whether used alone or integrated into
conventional rehabilitation, with both short-
term and long-term benets. [21]. Recently,
TT has been introduced to improve hamstring
muscle exibility [23, 24]. However, it is un-
clear whether its eect on muscle elongation
is more than the other mentioned methods
Figure 1. Sit & Reach test to evaluate hamstring muscle exibility
Figure 2. Athlete's position for the measurement of Active Knee Extension
Comparison between TECAR Therapy and Ultrasound Choobsaz H, et al.
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3
(i.e., therapeutic US or SS). In our research,
no study was found comparing the eects
of TT with the therapeutic US on hamstring
muscle shortness. Thus, this study aimed to
compare the eects of TT and US on the ex-
ibility of hamstrings in healthy athletes with
short hamstrings. Furthermore, the eects of
US with SS, and TT with SS were compared
separately.
Materials and Methods
Study Subjects
A total of 39 non-professional male athletes
with hamstring muscle shortness partici-
pated in the study [2]. The knee extension
range of motion (ROM) of 70 degrees or less
in the passive knee extension (PKE) test of
the dominant leg was considered hamstring
shortness [24]. The exclusion criteria were
that the athlete had a history of orthopedic
or neurological disorders in the lower limbs
within the last six months. In addition, sub-
jects with contraindications to TECAR or US
were excluded from the study. The procedure
was explained to the participants before ob-
taining their informed consent. The study
was approved by the University’s Ethics
Committee (IR.TUMS.FNM.REC.1398.063
; (IRCT20190920044826N1)). The athletes
were randomly assigned into groups of A,
B, and C by a simple randomization method
(using dice-throwing). One physiotherapist
applied the interventions, and another phys-
iotherapist who was unaware of the type of
intervention performed the measurements.
Study Assessment
The Sit and Reach (SR) test (Figure-1) as well
as active knee extension (AKE) and PKE tests
Figure 3. Summary of groups intervention
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Choobsaz H, et al. Comparison between TECAR Therapy and Ultrasound
(Figure-2), were used to measure hamstring
muscle exibility [25, 26] using a Flex Tester
Box and an orthopedic goniometer (Maurice
E. Mueller Foundation, Bern, Switzerland),
respectively. All measurements were carried
out three times before the intervention and af-
ter the rst and third sessions.
Study Intervention
Interventions included TT, SS, and US thera-
py administered on a group basis. Participants
in each group received treatment three times
a week. All interventions were applied in the
following manner:
Group A: TT plus SS
The subjects received TECAR therapy (Exon
Medical company, TecaTen model IRAN-
Class B) in a prone position for 15 minutes
at a frequency of 0.5 (MHz). The active elec-
trode (5 cm2) had a continuous circular mo-
tion over the posterior surface of the thigh,
while the inactive electrode was placed sta-
tionary over the quadriceps muscles (170 mm
230 mm). Then, the hamstrings were stretched
four times for 30 seconds each. The time in-
terval between stretches was 10 seconds.
Group B: US plus SS
Continuous US (Nutek model Pro UT1041,
China) was applied to the hamstrings for 15
minutes while the subjects were in a prone
position. US therapy was administered with
a power of 2 W/cm2, a frequency of 1 MHz,
and a cross-sectional probe area of 5 cm2 with
a circular motion speed of 2 cm per second.
Subsequently, the hamstrings were stretched
four times for 30 seconds each. The period be-
tween stretches was 10 seconds.
Group C: SS
Passive stretching was applied in a supine
position. The hip was exed to 90° and the
knee was passively and slowly extended [27].
To x the pelvis, the therapist pushed down
against the opposite leg (to prevent posterior
Table 1. Demographic Data of Athletes in Three Groups
Variable
Group A
(n=13)
Mean (SD)
Group B
(n=13)
Mean (SD)
Group C
(n=13)
Mean (SD)
P-Value
Age (years) 22.9 (2.431) 24.38 (2.364) 24.54 (3.017) 0.23
Weight (kg) 69.62 (4.053) 68.58 (7.457) 72.38 (4.92) 0.15
Height (cm) 179.54 (4.648) 179.15 (4.259) 181.54 (2.847) 0.27
BMI (kg/m2)21.592 (0.982) 21.538 (1.077) 21.938 (0.9134) 0.54
Table 2. Main Group Interaction and Evaluation Time for Hamstring Muscle Flexibility
Variables Source Type III Sum of
Squares D.F Mean
Square F Sig. Partial Eta
Squared
SRT
Time 66.462 1.19 55.856 14.526 0.000*.287
Time *
Group 38.154 2.38 16.033 4.169 .017*.188
Group 14.923 2 7.462 .971 .388 .051
PKE
Time 238.308 1.633 145.936 86.995 0.000*.707
Time *
Group 74.41 3.266 22.784 13.582 0.000*.43
Group 143.744 2 71.872 5.882 .006*.246
AKE
Time 291.897 1.729 168.826 72.178 0.000*.667
Time *
Group 82.513 3.458 23.862 10.201 0.000*.362
Group 222.205 2111.103 9.088 .001*.336
*BMI: Body Mass Index
SRT: Sit and Reach Test; PKE: Passive Knee Extension; AKE: Active Knee Extension
*P<0.05 was signicant
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5
Comparison between TECAR Therapy and Ultrasound Choobsaz H, et al.
pelvic tilt and lumbar exion). Each stretch-
ing technique was performed for 30 seconds
and repeated four times. There was a 5-sec-
ond pause between each stretching technique
(Figure-3).
Statistical Analysis
The obtained data were analyzed using SPSS
version 21(SPSS Inc; Chicago, IL, USA). The
Kolmogorov-Smirnov test showed normal
distribution for all variables (P>0.05). A one-
way analysis of variance (ANOVA) was used
to examine demographic dierences between
groups, as well as, determine the dierences
in exibility indices (AKE & PKE ROM, and
SR displacement) among the groups before
treatment.
A two-way ANOVA was used to detect dif-
ferences between groups and time points. A
Tukey Honestly Signicant Dierence (HSD)
post hoc analysis was performed to interpret
the ndings. Also, Cohen’s d was used to de-
termine the eect size of the groups on ham-
string exibility indices. The level of signi-
cance for all tests was set at P<0.05.
Results
A total of 39 athletes participated in the study.
The baseline measurements of the participants
are presented in Table-1. One-way ANOVA
test revealed no signicant dierences be-
tween groups in age, weight, height, and body
mass index (BMI). Furthermore, no signi-
cant dierence was found between the PKE
and AKE ROM, and displacement range in
the SR test before treatment among the groups
(P>0.05). Two-way mixed model ANO-
VA revealed signicant dierences in AKE
(P=0.001) and PKE (P=0.006) ROM among
the three groups. However, the displacements
in the SR test were not statistically signicant
among the groups (P=0.38). The eect of as-
sessment time on hamstring muscle exibili-
ty indices was signicant in all three groups
(P<0.05). The mean of all test variables after
the third session was more than the rst and
the pre-treatment sessions (P<0.05). The ef-
fects of group interaction and assessment time
were signicant for all three indices (P<0.05)
(Table-2). Tukey’s HSD post hoc test showed
that in groups A and C, the mean ROM of the
AKE and PKE was statistically greater than
that of group B (P<0.05). However, there
was no dierence between groups A and C
(P>0.05).
Displacement range in the SR test did not show
a statistically signicant dierence among the
three treatment groups (P<0.05, Table-3). Co-
hen’s d was used to determine the extent of the
eect of the dierent interventions on ham-
string exibility indices in the three groups.
Values between 0.2 and 0.5 were interpreted
as weak, while values between 0.5 and 0.8,
Table 3. Indices of Hamstring Flexibility (Knee Extension ROM and the Sit and Reach Test) between the
Three Treatment Groups
Variables (I)
Group
(J)
Group
Mean
Dierence
(I-J)
Std.
Error
P-
Value
95% Condence Interval
Lower
Bound
Upper
Bound
SRT
Group A Group B .23 .628 1.00 -1.35 1.81
Group B Group C -.85 .628 .558 -2.42 .73
Group C Group A .62 .628 1.00 -.96 2.19
PKE Group A Group B 2.26*.792 .022* .27 4.24
Group B Group C -2.44*.792 .012* -4.42 -.45
Group C Group A .18 .792 1.000 -1.81 2.17
AKE
Group A Group B 2.95*.792 .002* .96 4.94
Group B Group C -2.9*.792 .002* -4.89 -.91
Group C Group A -.05 .792 1.00 -2.04 1.94
SRT: Sit and Reach Test; PKE: Passive Knee Extension; AKE: Active Knee Extension
Group A: TECAR Therapy; Group B: Ultrasound therapy; Group C: Passive stretching
*P<0.05 was signicant
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Choobsaz H, et al. Comparison between TECAR Therapy and Ultrasound
and above 0.80 were considered as medium
and strong eect sizes, respectively (Cohen
J. Statistical Power Analysis for the Behav-
ioral Sciences; Brydges, 2019 #72). The re-
sults showed that the eect size of Group A
on changes for the AKE and PKE ROM, and
displacement range for the SR test was strong.
Group B had a strong eect on ROM changes
for AKE and PKE, while it was moderate for
the SR test. Group C eect size on the AKE
and PKE ROM was strong, but the range of
displacement in the SR test showed a moder-
ate eect (Table-4).
Discussion
This study was primarily conducted to com-
pare the eects of TT and US therapy on
hamstring muscle exibility in male athletes
with hamstring muscle shortness. The results
showed that TT could improve hamstring
exibility more than US therapy in all mea-
sures. One possible explanation may be at-
tributed to the dierent nature of these modal-
ities. TECAR is a radiofrequency wave that
can increase the endogenous temperature in
biological structures [18, 22]. We used the ca-
pacitive energy transfer mode, which aects
the tissues that contain more electrolytes,
including muscles and soft tissues [28]. On
the other hand, the US mechanical acoustic
wave is also absorbed by the muscles as pro-
tein-rich tissues [29]. However, high-frequen-
cy diathermy waves like TECAR can aect a
much wider area than the US [30]. In other
words, although the cross-sectional area of the
TECAR active electrode and US probe were
similar, the actual tissue area between both
TECAR electrodes (with 17×23 cm inactive
electrode size) was greater than that of the US.
So, TECAR appears to give more energy to
the hamstring muscles [31].
In addition, although US therapy with a fre-
quency of 1 MHz and an intensity of 2 W/
cm2 may increase intramuscular temperature,
the heat generated under the probe dissipated
throughout the tissue because the probe was
moving during the treatment time. Therefore,
the US could be more ecient in heating
smaller areas of the body [14, 32]. Further-
more, we only had three treatment sessions,
and US treatment may not have been su-
cient to elicit as much eect as TT (moderate
eect size vs. strong eect size, respective-
ly). So, more research with a longer treatment
time for larger muscles like hamstrings with
more treatment sessions is required to clarify
this assumption.
In our study, SS alone improved the exibil-
ity of the hamstring more than the US com-
bined with SS. Nuri et al. [33] showed that
SS could increase ankle dorsiexion ROM
more than US therapy (24.18% vs. 4.54%). It
seems that stretching alone can increase the
extensibility of tissues [34] due to a decrease
in the stiness of the muscle-tendon unit [35,
36]. Although it was assumed that the com-
bined eects of US and SS could improve
exibility more than SS alone, this was not
the case. It could be due to the large surface
area of the treatment, which prevents the local
tissue temperature from rising. In addition, in
our study, SS was performed after US thera-
py, additional benets of US therapy may be
seen when used concurrently with US therapy.
Similar to our results, Mohammadi et al. did
not nd a signicant dierence between TT
plus SS and SS alone in terms of improving
hamstring exibility [24].
On the other hand, Kim et al. showed that 15
minutes of TT alone could immediately im-
prove hamstring exibility [23]. It has been
reported that deep heating modalities like the
US or short-wave diathermy combined with
stretching could have more immediate eects
on muscle exibility than stretching alone
[37]. Therefore, it is possible that if we had
performed SS simultaneously with either of
the two thermal modalities, we could nd a
greater improvement than SS alone.
The eect size of the AKE ROM was more
than PKE in both the TT and SS groups, which
could be due to the dierence in neurophysi-
Table 4. Eect Size Values in Muscle Flexibility
Indices
Test Group A Group B Group C
PKE 1.6 1.12 1.44
AKE 3.31 0.65 2.6
SR 1.24 0.53 0.55
SR: Sit and Reach; PKE: Passive Knee Exten-
sion; AKE: Active Knee Extension
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7
Comparison between TECAR Therapy and Ultrasound Choobsaz H, et al.
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We would like to thank the Research Deputy
at the Tehran University of Medical Sciences.
We are also grateful to the athletes who par-
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The authors declare no conict of interest.
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Comparison between TECAR Therapy and Ultrasound Choobsaz H, et al.
