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DESCRIPTIVE MODEL OF MECHANICAL CHARACTERISTICS OF LEG MUSCLES IN ELITE KARATE ATHLETES MEASURED BY TMG METHOD

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  • Faculty of Sport and Physical Education, University of Priština-Kosovska Mitrovica

Abstract and Figures

The aim of this study was to investigate the neuromuscular response of knee flexor and extensor muscles using the tensiomyography (TMG) method and to compare the TMG characteristics between the dominant and non-dominant lower extremity in male karate competitors. Muscle mechanical properties were recorded from the rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and semitendinosus (ST) muscles of both legs. Three TMG parameters were analysed: maximal displacement (Dm), contraction time (Tc), and delay time (Td). Dm and Td parameters of the measured muscles were not affected by the lower extremity dominance in karate athletes. The dominant leg demonstrated a higher Tc of the RF (p = 0.013) and lower Tc of the BF (p = 0.004) compared to the non-dominant leg. A higher Tc of the RF occurs because of the controlled nature of punches and kicks. A lower Tc of the BF is due to the specific requirements of the fighting stance and frequent external hip rotation in karate techniques.
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Jeknić et al.: Mechanical characteristics o f leg muscles in elite karate athlete s Serb J Spo rts Sci 11(2): 55-60
55
Serbian Journal of Sports Sciences
ISSN 1820-6301
Original article
2020, 11(2): 55-61
COBISS.SR-ID 19050505
Received: 02 July 2020
UDC 612.76:796.853.26.071.2 Accepted: 12 Aug 2020
796.853.26.012.1
DESCRIPTIVE MODEL OF MECHANICAL CHARACTERISTICS OF
LEG MUSCLES IN ELITE KARATE ATHLETES MEASURED BY
TMG METHOD
Velimir Jeknić
1
, Lazar Toskić
2
and Nenad Koropanovski
3
1
Serbian Institute of Sport and Sports Medicine, Belgrade, SERBIA.
2
Faculty of Sport and Physical Education, University of Priština – Kosovska Mitrovica, SERBIA.
3
University of Criminal Investigation and Police Studies, Belgrade, SERBIA.
Abstract The aim of this study was to investigate the neuromuscular response of knee flexor and extensor
muscles using the tensiomyography (TMG) method and to compare the TMG characteristics between the
dominant and non-dominant lower extremity in male karate competitors. Muscle mechanical properties were
recorded from the rectus femoris (RF), vastus medialis (VM), v astus lateralis (VL), biceps femoris (BF) and
semitendinosus (ST) muscles of both legs. Three TMG parameters were analysed: maximal displacement (Dm),
contraction time (Tc), and delay time (Td). Dm and Td parameters of the measured muscles were not affected
by the lower extremity dominance in karate athletes. The dominant leg demonstrated a higher Tc of the RF (p =
0.013) and lower Tc of the BF (p = 0.004) compared to the non-dominant leg. A higher Tc of the RF occurs
because of the controlled nature of punches and kicks. A lower Tc of the BF is due to the specific requirements
of the fighting stance and frequent external hip rotation in karate techniques.
Key words: skeletal muscle, contractile properties, tensiomyography, karate, bilateral asymmetry
INTRODUCTION
Karate, as one of the most popular martial arts in the world was the subject of research from both theoretical
and empirical approaches [3, 12, 13]. Known for its attractiveness, it is classified among those specialties
requiring high technical and motor skills, such as a fine control of movement, accompanied by a great ability
to perform the main technical elements as fast as possible (‘‘ballistic actions’’) [23]. In karate sparring and
combat, two athletes face each other within a 2 m distance approximately, making offensive attacks against
each other [17]. The training process leads the karateka to have a fine control of his punches and kicks by
combining high velocity with high accuracy [10]. The movement of the body parts seek the maximum speed
[27], whether the goal is to strike, block or avoid the opponent attack. In karate, speed is considered a key
factor in performance success [8], where during combat ~ 84% of actions lasts less than 2 s [2].
Karate punches, kicks, blocks and frequent movements require a joint action sequence with the
participation of the leg, pelvis, torso, and arm muscles. Leg muscles that connect caudal joints are the most
important link in this kinetic chain and have a major role in the start and control of all karate actions and
stances stability [19]. Hariri and Sadeghi highlighted the importance of leg muscle properties in two cases.
One is regarding kicks, where they pointed out that increasing the knee speed and minimizing the time
elapsed from the ground is effective in improving kicking techniques. The second claim considered
movement efficiency, where they emphasized that the ability to do rapid manoeuvres and changes of
direction while moving on the ground is of utmost importance in karate performance [8]. The authors also
consider that the primary contributor to punch execution is the lower part of the body because of the fact
that ground force reaction is generated by the legs and transferred to the upper body, allowing for a
powerful movement [14, 15].
Jeknić et al.: Mechanical characteristics o f leg muscles in elite karate athlete s Serb J Spo rts Sci 11(2): 55-60
56
Several studies have investigated electromyographic activity (EMG) of karate techniques. Jemili et al.
measured EMG activity of the biceps and triceps brachii during the gyaku tsuki punch and the biceps and
rectus femoris during the kizamawashi geri kick before and after 3 months of intense karate training. The
findings of the investigation suggested that karate training modifies motor control patterns by increasing the
muscle activation time, associated with reduction in contraction time during punches and kicks, after the
specific karate training period [10]. Rinaldi et al. [21] investigated various characteristics of karate punches
in professional karate athletes by synchronizing the acquisition of kinematic, kinetic, and surface
electromyographic data. The observed muscles were the biceps brachii, triceps brachii, rectus abdominis,
erector spinae, rectus femoris and semitendinosus. Significant positive correlations were found between the
punch force and both right and left knee flexion at the instant of impact and right and left leg force. They
concluded that lower limb position and the force generated in both lower limbs are crucial in determining the
final punch force.
The TMG could be used in this case as an instrument to gather information on the muscle contractile
properties. TMG is a non-invasive diagnostic method which does not demand any effort from the individual
to whom it is applied. It is used as an evaluation tool for the mechanical characteristics and contraction
capacity of the surface muscle structures analysed [26]. It is of great importance to know if both sides have
to be evaluated when using TMG to monitor the response to training or evaluate the risk of injury. This work
was designed to study the neuromuscular response of the knee flexor and extensor muscles of both legs.
The aim of this study was to compare the TMG neuromuscular characteristics between the dominant and
non-dominant rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and
semitendinosus (ST) in male karate athletes.
METHODS AND MATERIALS
Thirteen male participants (age 24.08 ± 4.5 years; height 180.21 ± 9.11 cm; weight 79.51 ± 8.07 kg) from
the Serbian national karate team (all black belts with international competitive experience) were
assessed. All participants were fully informed of the potential risks associated with the study and signed
written informed consent forms previously approved by the Research Ethics Committee of the Faculty of
Sport and Physical education, University of Belgrade (No. 484-2), in line with the criteria of the
Declaration of Helsinki for research involving human beings. The summed mean, standard deviation,
coefficient of variation, minimum, maximum and range values for anthropometric measures of karate
competitors are presented in Table 1.
Table 1. Demographic characteristics of karate athletes
Mean SD cV% Min Max Range
Age 24.08 4.50 18.69 18.00 32.00 14.00
BH (cm) 180.21 9.11 5.05 161.40 193.10 31.70
BM (kg) 79.51 8.07 10.14 63.00 92.20 29.20
BMI (kg/m
2
) 24.45 1.43 5.84 22.10 28.00 5.90
BH: Body height; BM: Body mass; BMI: Body mass index
M
EASURES
The sensor was set perpendicular to the skin overlying the muscle belly. The oscillations of the muscle belly
in response to an electrically-induced twitch were recorded on the skin surface using a sensitive
displacement sensor (TMG–BMC, Slovenia). The maximal displacement amplitude – displacement muscle
(Dm), delay time (Td) and contraction time (Tc) were recorded (Figure 1), on both sides (right and left lower
extremity), from the rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and
semitendinosus (ST) muscles, using TMG (Table 2). The delay time (Td) in ms was defined as the time
between the electrical stimulus and the displacement of the sensor to 10% of the maximal displacement
amplitude (Dm) – in mm; and Contraction Time (Tc) in ms, was obtained by determining the time lag from
10% to 90% of the Dm [24].
S
TATISTICAL
A
NALYSIS
Descriptive statistics were used to summarize all demographic characteristics and outcomes. A paired t test
was employed to compare the TMG characteristics between both lower extremities. All statistical analyses
were conducted using the SPSS v.20 (SPSS, Inc. Chicago, IL, USA). The alpha level was set at 0.05.
Jeknić et al.: Mechanical characteristics o f leg muscles in elite karate athlete s Serb J Spo rts Sci 11(2): 55-60
57
Figure 1. Sensor collecting displacement muscle (Dm), delay time (Td) and contraction time (Tc) values in
response to muscle belly movement. Adapted from the "Assessment of muscle fatigue after an ultra-endurance
triathlon using tensiomyography (TMG)" by García-Manso JM. et al., 2011, Journal of Sports Sciences, 29(6):
619-625 [6]
RESULTS
There were no statistically significant differences in any of the TMG parameters evaluated between the
dominant and non-dominant VM, VL and ST muscles. There were no statistically significant differences in
the majority of TMG parameters evaluated between the dominant and nondominant RF and BF muscles.
The dominant side demonstrated a higher Tc of the RF (p = 0.013), but lower Tc of the BF (p = 0.004)
compared to the nondominant side.
Table 2. TMG characteristics of the dominant and non-dominant lower extremity in male karate athletes
Dm - maximal displacement, in mm; Td - delay time, in ms; Tc: - contraction time, in ms; RF - rectus femoris; VM -
vastus medialis; VL - vastus lateralis BF - biceps femoris; ST - semitendinosus; SD - standard deviation; cV% -
coefficient of variation.
KARATE
Dominant leg Non-dominant leg
Mean
SD cV% Min Max
Range
Mean SD cV% Min Max
Range
RF
Dm 6.43 1.98 30.90
2.54 8.72 6.17 6.58 2.39 36.40
1.29 9.31 8.01
Td 22.24
1.82 8.18 18.74
25.46 6.72 22.27 2.17 9.75 18.94
28.02
9.08
Tc 29.06
5.48 18.86
21.02
40.18 19.15 25.14 5.08 20.24
16.52
38.05
21.53
VM
Dm 7.89 2.14 27.19
5.03 12.75 7.72 8.01 2.60 32.48
3.33 10.79
7.46
Td 21.15
1.18 5.58 19.72
23.24 3.51 21.03 1.59 7.58 17.21
23.51
6.29
Tc 23.81
2.88 12.10
19.27
31.16 11.89 23.65 2.62 11.10
19.87
29.44
9.57
VL
Dm 4.89 1.52 31.04
3.16 7.39 4.23 5.26 1.62 30.88
2.41 8.51 6.10
Td 21.26
1.03 4.86 18.90
23.25 4.34 20.85 1.78 8.55 17.86
25.40
7.53
Tc 23.27
1.86 8.00 21.03
27.57 6.54 22.73 2.69 11.85
17.63
27.63
9.99
BF
Dm 6.50 2.01 31.03
3.34 9.31 5.97 7.45 2.43 32.71
3.93 13.42
9.49
Td 22.79
2.02 8.86 20.35
27.51 7.15 23.37 2.02 8.66 20.53
26.67
6.14
Tc 31.95
11.57
36.23
19.45
57.74 38.29 41.84 14.58
34.85
22.07
62.97
40.90
ST
Dm 8.31 2.38 28.69
3.84 12.23 8.39 8.24 2.53 30.70
3.32 11.97
8.65
Td 23.91
1.94 8.14 21.36
26.63 5.26 23.19 2.53 10.91
18.22
27.51
9.28
Tc 40.14
12.66
31.56
20.78
56.32 35.54 39.52 13.37
33.83
15.94
59.03
43.09
Jeknić et al.: Mechanical characteristics o f leg muscles in elite karate athlete s Serb J Spo rts Sci 11(2): 55-60
58
Figure 2. Average Rectus femoris muscle response of
the dominant and non-dominant leg to an electric
stimulus by means of TMG
Figure 3. Average Vastus medialis muscle response of
the dominant and non-dominant leg to an electric
stimulus by means of TMG
Figure 4. Average Vastus lateralis muscle response of
the dominant and non-dominant leg to an electric
stimulus by means of TMG
Figure 5. Average Biceps femoris muscle response
of the dominant and non-dominant leg to an electric
stimulus by means of TMG
Figure 6. Average Semitendinosus muscle response of the dominant and
non-dominant leg to an electric stimulus by means of TMG
DISCUSION
The principal finding of this investigation was that, in general, TMG characteristics of the main muscles of
the lower extremity were not affected by dominance in male karate athletes. To the best of our knowledge,
this is the first study to compare the TMG characteristics of the RF, VM, VL, BF and ST between the
dominant and non-dominant side in this population.
No significant differences were observed between the dominant and non-dominant leg except in the
Tc of RF (29.06 ± 5.48 vs. 25.13 ± 5.09, p = 0.013) and Tc of BF (31.95 ± 11.57 vs. 41.84 ± 14.58 p = 0.004).
Due to the non-existence of karate reports, these results are compared with available literature from other
sports also tested with the TMG. Results from a study by Garcia-Garcia [18] are similar to ours in terms of the
size of the symmetry, but different in terms of the variables that stood out with the differences. The knee
extensor and flexor muscles (VM, VL, RF and BF) are assessed in elite amateur road cyclists through TMG.
Jeknić et al.: Mechanical characteristics o f leg muscles in elite karate athlete s Serb J Spo rts Sci 11(2): 55-60
59
The recorded parameters were the Dm, Tc, Td, Ts, Tr and Vc (the rate between the radial displacement
occurring during the time period of contraction time). No significant differences were observed between the
dominant and non-dominant leg except in the Dm and Vc of the RF (2 out of 24 possible differences). The
contractile properties (Td, Tc and Dm) of the RF and BF muscles were observed in two male futsal player
groups – elite and sub-elite [16]. In terms of asymmetries, when comparing the dominant and non-dominant
leg, elite players did not present bilateral asymmetries neither in RF nor in BF. On the contrary, sub-elite
players displayed a significantly greater Td in the RF of the non-dominant leg, but no other asymmetries
were found. In our study, the RF was also the muscle that made the difference, but in the Tc parameter.
Alvarez-Diaz et al. [1] investigated the differences between dominant and non-dominant lower extremity
muscle characteristics in soccer players. The examined muscles were VM, VL, RF, ST, BF, GM
(gastrocnemius medialis) and GL (gastrocnemius lateralis). As in our study, the vast majority of muscle
comparison (29 out of 35) did not show significant differences. Although the authors did report some
differences in certain parameters – a higher VM-Tc, RF-Ts, RF-Tr, BF-Ts and lower VL-Tc and Td compared
to the nondominant side, they concluded that TMG measurements of soccer players were not generally
influenced by leg dominance. An even greater symmetry was found in research where TMG was used to
measure the radial muscle belly displacement of the VM, VL and RF knee extensor muscles, and of the long
head of the BF flexor muscle of soccer players [4]. Each measurement involved recording the following
variables of involuntary isometric contraction produced by the electrical stimulus: Dm, Tc, Td, Ts, Tr and Vc
(contraction velocity). No differences were observed between the dominant and non-dominant leg of the
soccer players. Also, Rodriguez-Ruiz et al. [22] analysed differences in the muscle response and mechanical
characteristics of the VM, RF, VL and BF in elite volleyball players of both sexes using TMG. They found no
differences between the dominant and non-dominant leg.
The differences in TMG values between the present study and the existing literature may be explained
by different requirements of the sports. The RF, VL, VM and VI muscles are powerful extensors of the knee
joint. They are crucial in walking, running, jumping and squatting, but, because the RF attaches to the ilium,
this muscle is also a flexor of the hip. Since hip flexion movement is used in karate when preparing all kicks
(jap. Hiki ashi), the RF developed different contraction qualities than other muscles from the knee extensor
group. The existence of a lower Tc only in the dominant leg of the RF is due to the fact that it has a rapid
activation (Td) in the hip joint, followed by a braking phase in order to control the impact and amplitude of kick,
leg swings and punch (Tc) in controlled fashion, according to the rules of the World Karate Federation [11].
Same as the RF, the BF muscle acts on both the knee and hip joint. Acting simultaneously on these
joints, the BF has many important functions - flexion and external rotation at the knee; extension and external
rotation in the hip joint (unlike the other two muscles of the hamstring group – ST and SM). External rotation of
the BF muscle in the hip is of utmost importance in executing karate kicks because of the rotation of the feet of
the standing leg [18]. Also, the criteria for kumite performance judgement include awareness (jap. Zanshin) -
the state of continued commitment in which the contestant maintains total concentration, observation, and
awareness of the opponent's potentiality to counter-attack. As part of Zanshin, competitors especially
accentuate their punching techniques with fast external rotation (BF function) - hip opening and return of the
fist backward. Further, from the fighting stance (jap. Fudo dachi), the body moves fast forward and makes an
external rotation in the hips during front fist punches (jap. Kizami tsuki, Uraken uchi). The dominant leg is in
this situation the pushing leg and the BF demonstrates short Tc, while the leg in front (non-dominant) stops the
movement and controls the distance using the knee extensors and hip flexors as breaking power (slower Tc in
RF). Due to their important role in the muscles of the knee and hip joints, the BF and RF are the most
examined and often the only muscles analysed in studies focused on the leg muscles [7, 16, 20, 25].
This study demonstrates that lower extremity dominance should not be a deciding factor for all
muscles when investigating TMG in karate athletes, due to the described requirements of the sport (Figures
2-6). It contributes to the literature on the physiological profile of karate competitors, especially in regard to
the elite level of the respondents. A methodological limitation, however, was that subjects analysed came
from only one gender. A limitation of the present study could also be the size of the sample, as only 13
competitors were tested.
CONCLUSION
This study has provided an insight into the neuromuscular profile of high level karate competitors. In
summary, TMG characteristics Dm and Td of the RF, VM, VL, BF and ST were not affected by lower
extremity dominance. On the other hand, significant differences were found in the Tc of the RF and BF
muscles. A higher Tc in the RF of the dominant leg compared to the non-dominant leg most probably occurs
because of the activation of the brake mechanisms during karate punches and kicks. A lower Tc in the BF is
due to the fact that the dominant leg is in most of the cases the pushing leg that moves the fighter forward
and makes frequent external hip rotations.
Jeknić et al.: Mechanical characteristics o f leg muscles in elite karate athlete s Serb J Spo rts Sci 11(2): 55-60
60
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Address for correspondence:
Velimir Jeknić
Serbian Institute of Sport and Sport Medicine
Kneza Višeslava 72
11000 Belgrade
SERBIA
E-mail: velimirjeknic@yahoo.com
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... This style is considered to be one of the most difficult karate styles; it has a knockdown system [20], and athletes do not always use protective equipment and can suffer significant damage [23]. Karate distinguishes itself by fast legwork, sudden kicks of the lower limbs, different techniques, ad changes in distance [24]. The fight takes place between two fighters without any weapons but at maximum speed and strength [25], while the arm and leg strokes dominate to score points or win the fight [26]. ...
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BACKGROUND: Information regarding the relationship between methods for assessment of voluntary and involuntary muscle contractile properties is of importance in sport science and medicine. OBJECTIVE: To appraise the concurrent and predictive validity of isokinetic dynamometry and tensiomyography (TMG) in differently trained men and women. METHODS: Fifty men and 45 women were divided into three groups: physically inactive, physically active and athletes. Isokinetic testing was performed on knee muscles in concentric mode at 60 and 180°s while tensiomyographic measurements were obtained from the rectus and the biceps femoris muscles. RESULTS: A small, statistically significant correlation was detected between the peak moment and tensiomyography parameters relating to contraction time and maximal displacement (Adj. R=2 0.086, p= 0.028). CONCLUSION: In general, isokinetic dynamometry and tensiomyography are not related and represent different technologies that measure different contractile properties of muscles. A hierarchical structure of predictive validity at the level of individual variables was detected as a function of gender and training level.
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