Kondo Hiroshi, et al.. Japanese Acupuncture and Moxibustion; 2014; Vol.10(1): 8-13

Original ResearchElectro-acupuncture significantly delayed multifidus muscle reaction time inathletes with lower back pain
KONDO Hiroshi 1,2), MIYAMOTO Toshikazu 2), MIYAKAWA Shunpei 2)1) Faculty of Health Science, Tsukuba University of Technology
2) Doctoral Program in Sports Medicine Graduate School of Comprehensive Human Sciences Laboratory of
Advanced Research D University of Tsukuba
Abstract[Objective] The aim of the present study was to investigate the effect of electro-acupuncture of the lumbar region on
the reaction time of the trunk muscles during postural sway.
[Methods] This study is non-blind comparative study. The subjects comprised 7 young athletes with lower back painin the lower back pain (LBP) group and 8 healthy athletes in the control (CON) group. We measured the muscle reaction time of the trunk when the floor below the right leg suddenly tilted during standing at rest. Three measurements
were taken for the right multifidus muscle and the right internal oblique muscle and median values were used foranalysis. Acupuncture was performed as an intervention for the left–right lumbar erector spinae muscles (L4 and L5)
with an electrical stimulus of 1 Hz for 10 min.
[Results] The multifidus muscle reaction time was significantly delayed in the LBP group after electro-acupuncture
stimulation compared with that before stimulation (P<0.05). In the CON group, no significant difference was observed between the times before and after electro-acupuncture stimulation. No significant differences were noted in
the internal oblique muscle reaction times before and after electro-acupuncture stimulation in either the LBP or CON
group.
[Conclusion] While no differences were noted in healthy individuals, electro-acupuncture significantly delayed multifidus muscle reaction time during postural sway in athletes with lower back pain.
Key words: acupuncture, reaction time, EMG, multifidus muscle, lower back pain
I. Introduction
The incidence of sports injuries is expected to increaseas the number of people participating in sports increases.
Previous studies have reported that the incidence oflower back pain is high among those with experience incompetitive sports.1) Lower back pain follows a chronic
course and can be a major obstacle to sports activities
and competition.
Since the 1980s, the importance of the lumbar stability
in alleviating and preventing lower back pain has beenrecognized. It has been known that deep trunk muscles
stabilize the trunk by the activities prior to the movement of the limbs4,5). Therefore, in the field of sports,functional training program for the transversus abdominis and multifidus to improve the performance has
been attracting attention. Early studies on the role of thelumbar spine reported a distinctive activity of the trunk
muscles using electromyography (EMG). The flexion–
relaxation phenomenon, in which the activity of the backmuscle disappears when the trunk is bent forward to the
maximum, can be observed in healthy individuals but is
not observed in those with chronic lower back pain 2).
Moreover, the majority of individuals with chronic lower
back pain exhibit asymmetrical muscle activity in theerector spinae muscles when bending forward as well asa delayed reaction time of the transverse abdominal
muscle compared with healthy individuals, and this fea-

Corresponding author: Kondo Hiroshi, Faculty of Health Science, Tsukuba University of Technology, 4-12-7 Kasuga, Tsukuba
City, Ibaraki 305-8521 Japan9
Kondo Hiroshi, et al.. Japanese Acupuncture and Moxibustion; 2014; Vol.10(1): 8-13

ture is even present in those with only a history of lower
back pain3-5).
The first line of treatment for lower back pain is conservative therapy. One form of conservative therapy is
acupuncture, which is shown to be effective in alleviation of pain, adjustment of muscle tonus, and recovery
from dysfunctions after sports injuries6-8). Electroacupuncture for athletes with lower back pain has beenreported to be effective in improving training status9).
Acupuncture is therefore expected to be useful in the
expedited recovery of sports injuries secondary to pain
relief as well as prevention of sports injuries secondary
to muscle tone adjustment.
Acupuncture is known to improve muscle tonus; therefore, it may also affect the muscle reaction time. The
muscle reaction time is the duration between the stimulus and the muscle stretch reflex, which is controlled bymuscle tonus via γ motor neurons in a variable manner10).
To the best of our knowledge, no study till date has investigated the effect of acupuncture of the lumbar region
on the reaction time of the trunk muscles. If electroacupuncture affects the muscle reaction time and adjustsmuscle tonus, it would be useful in athlete conditioning.
The aim of the present study was to investigate the effect of electro-acupuncture of the lumbar region on thereaction time of the trunk muscles during postural sway
in athletes with low back pain and healthy athletes.
Ⅱ．Materials and Methods
1. Subjects
The subjects comprised 7 young athletes with lower
back pain in the lower back pain (LBP) group (age: 19.6
± 1.3 years; height: 174 ± 5.2 cm; weight: 67.3 ± 6.0 kg)
and 8 healthy athletes in the control (CON) group (age:21.5 ± 1.5 years; height: 172.6 ± 6.9 cm; weight: 65.3 ±7.1 kg).
All subjects were male university soccer players. In aprior interview, the subjects in the LBP group explained
whether their lower back pain appeared during or after
matches; however, this lower back pain was not enoughto stop matches. In addition, the subjects were not diagnosed with lower back pain by a doctor (Table1).

Fig.1 Trap door
A device that tilts by 25° very suddenly (“trap door”) was
placed on the floor in the contact area of the right leg in order
to induce postural sway. The subjects stood on the trap door
floor, with equal force applied to both feet. The subjects also
stood with their second toe and calcaneal protuberance positioned on a straight line marked on the floor. We measured
the muscle reaction time of the trunk when the floor below
the right leg suddenly tilted during standing at rest.

The purpose of the research was explained to the subjects who then gave their written consent to participate.
This study was conducted with the approval of the Ethical Review Board of Tsukuba University of Technology.
2. Measurement devices and methods
A device that tilts by 25° very suddenly (“trap door”)
was placed on the floor in the contact area of the rightleg in order to induce postural sway (Fig. 1). The subjects stood on the trap door floor, with equal force applied to both feet. The subjects also stood with theirsecond toe and calcaneal protuberance positioned on astraight line marked on the floor. We measured the muscle reaction time of the trunk when the floor below theright leg suddenly tilted during standing at rest. The trap

Table.1 Characteristic of low back pain subjects
Subject
Duration of
Diagnosis
Pain region
Trigger
RDQ(pt）
VAS(mm)No.
illness(years)
14
none
both sides
during the competition
3
61
2
2
none
right side
during practice
1
44
3
7
none
both sides
in the ADL
1
17
4
4
none
left side
during the competition
1
30
5
0.5
none
right sidein the ADL
1
24
6
0.5
none
left side
unknown
1
45
7
0.7
none
both sides
after the return of the injury
150This table shows Duration of illness, Diagnosis, Pain region, Trigger the onset, Roland-Morris Disability Questionnaire(RDQ) and lower back pain Visual Analog Scale (VAS) of low back pain subjects.

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Kondo Hiroshi, et al.. Japanese Acupuncture and Moxibustion; 2014; Vol.10(1): 8-13

door was operated at random from behind the subjects sothat they were unaware of the timing.
Surface electromyography (EMG; Biometrics Ltd.,
Newport, UK) was used to measure muscle activity.
EMG waveforms derived from surface EMG were amplified by an amplifier and recorded in synchronization
with the tilt timing of the trap door. Recorded EMG
waveforms underwent A/D conversion at a sampling
frequency of 1000 Hz and were input into a computer.
The TRAIS System (DHK, Tokyo, Japan) was used toanalyze EMG waveforms. Motion artifacts were removed from EMG waveforms with a band-pass filter.
The muscle reaction time was the time between the tiltof the trap door and the initiation of muscle activity as
indicated by a spike in the EMG waveform when therectified EMG waveform at rest reached its peak (Fig.
2).11,12)
Three measurements were taken for the right multifidus muscle and the right internal oblique muscle andmedian values were used for analysis. Placement of theelectrodes was in accordance with previous studies13,14).
The right multifidus placement site was 2 cm right andlateral to the fifth lumbar spinous process, and the rightinternal oblique muscle placement site was 2 cm below
and medial to the right anterior superior iliac spine (Fig.
3). Bipolar surface electrodes with an integrated electrode and amplifier were used. The distance between theelectrodes was 10 mm. The electrodes were placed parallel to the muscle fiber direction of each muscle. The
earth electrode was placed on the wrist of the right hand.
The electrode placement sites for the internal obliquemuscle were consistent with the reaction time of thetransverse abdominal muscles in a previous study14) thatused surface EMG and wire EMG, which was reported
to be highly reproducible. The present study demonstrates the reaction times of the internal oblique andtransverse abdominal muscles.
3. Electro-acupuncture stimulation method
There were 4 acupuncture sites in the muscle layer
corresponding to the multifidus muscle on the left andright straight sides of the spinous process (Jiaji; EX–B2)
at the height of the bilateral fourth and fifth lumbar
spinous processes. Disposable stainless steel acupuncture needles (Seirin Co., Ltd., Shizuoka, Japan; 60 mm
in length, 0.2 mm in diameter) were inserted into themuscle to a depth of 3 cm. Electrodes were then attachedto each of the acupuncture needles on the left and rightsides and a current was applied at a frequency of 1 Hz
using a low-frequency power supply unit (Zeniryoki,
Fukuoka, Japan; Ohm Pulser LFP-4500A). Stimulation
was performed for 10 min once twitch was confirmed.
Acupuncturists of one was the acupuncture.
4. Statistical analysis
The reaction times of the multifidus and internal
oblique muscles before and after electro-acupuncture
stimulation were compared between the LBP and CON
groups using the Mann–Whitney U test. Comparison of
the reaction times before and after electro-acupuncture
stimulation within the LBP and CON groups was performed using the Wilcoxon signed-rank test. SPSS Statistics ver.18 (IBM Corporation, Japan) was used forstatistical processing and the significance level was set at<5%. Measured values are shown as mean ± standard
deviation.

Fig.2 The muscle reaction time was the time between the tilt of the trap door and the initiation of muscle activity as indicated by a
spike in the EMG waveform when the rectified EMG waveform at rest reached its peak.

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Kondo Hiroshi, et al.. Japanese Acupuncture and Moxibustion; 2014; Vol.10(1): 8-13

Fig.3 This figure shows the Placement of the electrodes. The right multifidus placement site was 2 cm right and lateral to the fifth
lumbar spinous process, and the right internal oblique muscle placement site was 2 cm below and medial to the right anterior superior iliac spine(ASIS).

Fig.4 This figure shows the mean multifidus muscle reaction time of electro-acupuncture stimulation before and after. The mean
multifidus muscle reaction time was significantly delayed in the LBP group after electro-acupuncture stimulation compared withthat before stimulation (P<0.05).

Ⅲ．Results
1.

Multifidus muscle reaction time
The muscle reaction time prior to electro-acupuncture
stimulation was 101.2 ± 22.6 ms in the LBP group and
112.0 ± 24.2 ms in the CON group, indicating no significant difference. After stimulation, this time increased

to 129.2 ± 14.2 ms in the LBP group and 114.8 ± 18.4
ms in the CON group, indicating no significant difference. The reaction time was significantly delayed in the
LBP group after electro-acupuncture stimulation compared with that before stimulation (P=0.018). In the
CON group, no significant difference was observed be-12
Kondo Hiroshi, et al.. Japanese Acupuncture and Moxibustion; 2014; Vol.10(1): 8-13

tween the times before and after electro-acupuncture
stimulation (Fig. 4).
2. Internal oblique muscle reaction time
The muscle reaction time prior to electro-acupuncture
stimulation was 45.6 ± 24.3 ms in the LBP group and67.5 ± 27.4 ms in the CON group, indicating no significant difference. After stimulation, this time increased to59.1 ± 21.8 ms in the LBP group and 77.5 ± 23.1 ms in
the CON group, indicating no significant difference. No
significant differences were noted in the reaction times
before and after electro-acupuncture stimulation in either
the LBP or CON group (Fig. 5).
Ⅳ．Discussion
Our investigation of the effect of electro-acupunctureon the reaction times of the multifidus and internal
oblique muscles during postural sway demonstrated thatmultifidus muscle reaction time was delayed following
electro-acupuncture in participants with lower back pain
(LBP). When the body’s stability is unexpectedly threatened while playing sports, the nervous system reacts
immediately to control the posture, causing complex
interactions to occur. The stretch reflex is involved inthis reaction, generating afferent impulses by stretchingmuscle spindles and causing contraction by exciting theα motor neurons in these muscles. This latency of activity is called the muscle reaction time and is calculated
from the start of muscle activity when articular motion
occurs immediately in response to stimuli such as lightor sound15).
In studies to date, the reaction time of the trunk mus-cles has been confirmed as delayed in chronic lower
back pain patients compared with healthy individuals5).
In the present study, we observed no difference between
the groups with regard to the muscle reaction times prior
to intervention. However, following electro-acupuncture,
multifidus muscle reaction time was delayed in the LBP
group.
Yoshida et al. investigated the effect of acupuncture
stimulation on the muscle reaction time and reported thatelectro-acupuncture stimulation shortened the muscle
reaction time16). However, while the electro-acupuncture
method was similar, the study focused on participants
with ankle instability16). Therefore, it remains unclear
whether differences in muscle reaction time changes
caused by electro-acupuncture stimulation depend on theacupuncture site and attributes of the muscle in question.
A study using microneurography reported that electroacupuncture suppresses adrenergic sympathetic nerve
activity through somatic–autonomic reflexes and thus
decreases muscle tonus and improves muscle hemodynamics17). Ishii et al.10) reported that reaction time speeds
up when muscle tonus is enhanced by excitement of γ
motor neurons and slows down when muscle tonus issuppressed. This suggests that in athletes with lower
back pain, electro-acupuncture stimulation produces adelay in the muscle reaction time by suppressing α motor
neuron excitement at the spinal cord level, which suppresses γ motor neuron excitement and decreases muscle
tonus. In other words, electro-acupuncture to the multifidus muscle in athletes with lower back pain delayed
multifidus muscle reaction time by relieving muscle
tonus.
Deep muscles in the trunk, namely the transverse ab-

Fig.5 This figure shows the mean internal oblique muscle reaction time of electro-acupuncture stimulation before and after. No
significant differences were noted in the internal oblique muscle reaction times before and after electro-acupuncture stimulation ineither the LBP or CON group.

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Kondo Hiroshi, et al.. Japanese Acupuncture and Moxibustion; 2014; Vol.10(1): 8-13

dominal and multifidus muscles, play an important rolein achieving lumbar spine stability by interaction. Muscle reaction time of the transverse abdominal muscle isdelayed with chronic low back pain patients. Therefore,
the delay of muscle reaction time may be associated withinstability of the lumbar spine. After electro-acupuncture
stimulation, muscle reaction time of the multifidus muscles is delayed, but transverse abdominal muscle had noeffect on muscle reaction time of the internal obliquemuscle. Therefore, the delay of muscle reaction time ofmultifidus muscles by acupuncture stimulation cannot beclearly about the effects of the lumbar instability.
The present study found that electro-acupuncture delayed multifidus muscle reaction time, suggesting that
this technique is useful in improving muscle tonus inthose with lower back pain. However, the effect of delayed multifidus muscle reaction time on an athlete’s
performance has not been investigated. It is also unclear
how long this delay is sustained. To examine the relationship between performance and muscle reaction timeof the trunk muscles is necessary in order to demonstrate
the effectiveness of electro-acupuncture for athletes.
Furthermore, the present study did not examine motor
neuron activity involved in muscle tonus. Therefore,
further investigations are necessary to examine themechanism of action underlying nervous activity caused
by electro-acupuncture.

6)

7)

8)
9)

10)

11)

Ⅴ．Conclusion
The present study investigated the effects of electroacupuncture on the reaction times of the multifidus andinternal oblique muscles during postural sway. While nodifferences were noted in healthy individuals, electroacupuncture significantly delayed multifidus muscle
reaction time during postural sway in athletes with lower
back pain.

12)

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