Abstract
Cervical traction is a physical therapy procedure frequently used to treat cervical disk lesions, cervical spondylosis, and
cervical facet joint lesions. We have observed rare cases of side effects in elderly patients, but not in women younger than
30 years.
In this pilot study, 96 young women were randomly divided into 3 groups to study the effect of cervical traction with different
traction weights on blood pressure, heart rate, heart rate variability, and correlated autonomic adjustment. Cervical traction
weight used was 10% of the patient’s body weight in group A (n=32), 20% in group B (n=32), and 30% in group C (n=32). Assessments
of blood pressure, heart rate, heart rate variability, percentage of high- and low-frequency signals, and low-frequency/high-frequency
ratio were performed before, during, and 20 minutes after traction. We found that systolic blood pressure, diastolic blood
pressure, and heart rate variability elevated during cervical traction and returned nearly to original levels immediately
after traction in group C, but not in groups A or B. There were no significant changes in heart rate, percentage of high-
or low-frequency signals, and low-frequency/high-frequency ratio in all 3 groups during or after cervical traction.
Cervical traction with a traction weight approximately 10% to 20% of body weight can be safely provided without significant
compromise of cardiovascular function. However, heavy traction weight (30% of body weight) should be avoided, especially for
a patient with cardiovascular disease.
Dr Tsai and Mr Lai are from the Department of Rehabilitation Medicine, Da-Chien General Hospital, Dr Chang is from the Department
of Recreation Sports and Health Promotion, Asia-Pacific Institute of Creativity, Miao-Li, Dr Kao is from the Department of
Rehabilitation Medicine, Taipei City Hospital, Taipei, and Mr Wang is from the Department of Rehabilitation Science, Jen-Teh
Junior College of Medicine, Nursing and Management, Miao-Li, Taiwan.
Drs Tsai, Chang, and Kao and Messrs Wang and Lai have no relevant financial relationships to disclose.
Correspondence should be addressed to: Wen-Dien Chang, PhD, Department of Recreation Sports and Health Promotion, Asia-Pacific
Institute of Creativity, No. 110 Syuefu Rd, Toufen Township, Miaoli County 351, Taiwan (steven-mandy@yahoo.com.tw).
Cervical traction is a physical therapy procedure frequently used to treat cervical disk lesions, cervical spondylosis, and
cervical facet joint lesions.
1,2
The proposed mechanisms of therapeutic effectiveness include decreased spasms in the paraspinal muscles, increased opening
of intervertebral foramina, increased intervertebral disk space, improved vertebral alignment, and improved disk hydration.
1,2
However, it has been reported that adverse events related to increased blood pressure, such as headache, dizziness, and nausea,
could develop after cervical traction.
3
Traction weight may be an important factor in such side effects. Comparing different traction weights, Akinbo et al
4
demonstrated that cervical traction with a weight approximately 10% of body weight could provide good relief of neck pain
with no significant adverse effects. Heavy traction weights are usually applied in tongs traction for cervical instability
to reduce dislocations/subluxations.
5
It is likely that patients under tongs traction may have a higher incidence of adverse effects than regular cervical traction
with lower weight. However, to our knowledge, there have been no studies on the effects of cervical traction on cardiovascular
function.
It has been reported that heart rate variability could provide important information about cardiac function in patients with
myocardial infarction.
6,7
Heart rate variability refers to the complex beat-to-beat variation in heart rate produced by the interplay of sympathetic
and parasympathetic neural activity at the sinus node of the heart, and can provide important information about cardiovascular
function related to autonomic system activity.
8,9
In our clinical practice, we have observed rare cases of side effects in elderly patients, but not in women younger than 30
years. In this pilot study, we investigated 96 young women to study the effect of cervical traction with different traction
weights on blood pressure, heart rate, heart rate variability, and correlated autonomic adjustment.
Materials and Methods
Ninety-six women aged 18 to 23 years were recruited for this study. They were healthy with no significant cardiopulmonary
diseases, endocrine disorders, neurological disorders, musculoskeletal diseases, mental diseases, or any other significant
medical problems. Smokers, heavy drinkers, drug abusers, or heavy coffee drinkers were excluded. They were prohibited from
consuming any drug, alcoholic beverage, or coffee within 24 hours prior to the study. They signed the informed consent forms
approved by the Institutional Review Board of the university.
Patients were randomly divided into 3 groups. Cervical traction weight used was 10% of the patient’s body weight in group
A (n=32), 20% in group B (n=32), and 30% in group C (n=32). Patient demographic data are listed in Table . There were no significant differences in patient age, body weight, body height, and body mass index (BMI) among the 3 groups.
Blood pressure, heart rate, and heart rate variability with related autonomic nervous system function were assessed before,
during, and immediately after cervical traction with 3 different traction weights in the 3 groups. Prior to cervical traction,
each patient sat on a traction chair with the forearm resting on an arm support in a comfortable position. The traction belt
was fixed on the head, then the patient was advised to rest for 5 minutes before the initial assessment. The initial assessment
lasted for 6 minutes, including 1 minute of blood pressure and heart rate measurement followed by 5 minutes of heart rate
variability and related autonomic nervous system function. The second assessment was performed beginning 10 minutes after
traction for another 6 minutes. Cervical traction was continuously performed for a total of 20 minutes. Immediately after
traction, post-traction assessment was performed for another 6 minutes. The sequence of the procedure is shown in Figure .
Cervical traction was performed with an electrically controlled traction unit (Eltrac 471; Enraf-Nonius, Rotterdam, Netherlands).
As soon as the initial assessment was completed, the head belt was connected to the traction cable at a 20° to 30° flexion
angle (Figure ). The traction cable connected to the traction machine maintained a continuous cervical traction for 20 minutes in each experiment.
During traction, the patient maintained a comfortable sitting position on a traction chair reclined to 100° (Figure ). The traction procedure could be discontinued immediately if the patient felt any discomfort. Each traction procedure was
performed by the same investigator (W.D.C.). The patients were not informed about the traction weight they received.
Changes in blood pressure and heart rate were measured on the arm with an electronic sphygmomanometer (ET-SP302; Terumo, Tokyo,
Japan). Data on systolic blood pressure, diastolic blood pressure, and heart rate from 3 the assessments were recorded for
the calculation of mean and standard deviation for further analysis.
Heart rate variability, high-frequency (HF) signals (0.15-0.4 Hz), low-frequency (LF) signals (0.04–0.15 Hz), and low-frequency/high-frequency
ratios were analyzed according to the guidelines of the Task Force of the European Society of Cardiology and the North American
Society of Pacing and Electrophysiology
10,11
using electrocardiography (Check-My-Heart; Daily-Care Bio-Medical, Chungli, Taiwan) for 5 minutes and analyzed with heart
rate variability analysis software. Heart rate variability data were obtained by calculation of the standard deviation of
R-R intervals on electrocardiogram. Percentage of high-frequency signals was calculated as HF power/(HF power+LF power) and
percentage of low-frequency signals was calculated as LF power/(HF power+LF power). High-frequency percentage indicates cardiovagal
activity
8,9,12,13
and low-frequency percentage indicates cardiosympathetic activity.
8,9
Therefore, the low-frequency/high-frequency ratio represents autonomic balance.
14
Statistical analysis was performed using SPSS software (SPSS Inc, Chicago, Illinois). The differences in demographic information
among 3 groups, including age, body weight, body height, and BMI, were analyzed with the nonparametric Mann-Whitney
U test. Differences in blood pressure, heart rate, heart rate variability, high- and low-frequency signals, and low-frequency/high-frequency
ratios among the 3 measurements were analyzed with analysis of variance. A
P value <.05 was considered statistically significant.
Results
Changes in Blood Pressure
Changes in blood pressure during and after cervical traction in each group are shown in Figures and . There were no significant changes (
P>.05) in either systolic or diastolic blood pressure during or after traction in groups A and B. In group C, either systolic
or diastolic blood pressure was significantly higher (
P<.05) during traction than before traction, but was not significantly different immediately after traction compared to before
traction (Table ).
Changes in Heart Rate
Table and Figure show the changes in heart rate during and after cervical traction in each group. There were no significant changes (
P>.05) in heart rate during or after traction in all 3 groups.
Changes in Heart Rate Variability
There were no significant changes in heart rate variability during and after cervical traction in groups A and B. However,
in group C, heart rate variability was significantly larger (
P<.05) during traction than before traction, but was not significantly different than before traction (Table ; Figure ).
Changes in Autonomic Functions
Changes in autonomic nervous system function (including high- and low-frequency signals and low-frequency/high-frequency ratios)
were insignificant (
P>.05) during and after cervical traction in all 3 groups (Table ; Figures , ).
Discussion
In this pilot study on young healthy women, we found that cervical traction with a constant weight of approximately 30% of
body weight could cause significant increases in both systolic and diastolic blood pressure during cervical traction but return
to almost original levels immediately after traction. There was also a significantly larger heart rate variability during
cervical traction than before traction. These changes could not be observed during traction with a weight of either 20% or
10% of body weight. Changes in heart rate and related autonomic nervous system function were all insignificant during cervical
traction with all 3 weights.
Changes in Blood Pressure Related to Cervical Traction
In a previous study, Utti et al
3
found increases in both systolic blood pressure (from 114.6±10.4 to 123.5±9.8 mm Hg) and diastolic blood pressure (from 72.4±9.5
to 77.9±8.9 mm Hg) after cervical traction with 10% of body weight. In our study, no significant changes in blood pressure
were found when 10% or 20% of body weight was used for cervical traction (
P>.05). This is likely due to the mean body weight in our patients, which was much lower than that in Utti et al’s study.
3
The reversible changes in blood pressure due to cervical traction with heavy weight (30% of body weight) may be related to
various factors, including direct stretching to baroreceptors in the carotid sinus during traction to elicit a baroreflex
15
; direct stretching to muscles, tendons, and ligaments to cause a stress-related sympathetic reflex (physical stress); and
psychological irritability (mental stress). It appears that the high traction weight (30% of body weight) applied directly
on the chi could cause significant stress to cause pain and increase in sympathetic tone, so that the blood pressure was increased
during traction.
Changes in Heart Rate Related to Cervical Traction
Theoretically, an increase of blood pressure can cause baroreflex to reduce heart rate and to cause autonomic adjustment.
16
However, we observed no changes in heart rate in response to blood pressure changes. It may be due to a small sample size.
An increase of heart rate after cervical traction was found in a previous study.
3
Further study on a larger sample is required to clarify this discrepancy.
Changes in Autonomic Function Related to Cervical Traction
We observed an increase in heart rate variability during traction with a heavy weight (30% of body weight) in response to
the elevated blood pressure. However, regarding this increase in autonomic adjustment, we were unable to clearly distinguish
whether these changes were related to sympathetic adjustment or vagal adjustment. In our study, we found an increase in percentage
of high-frequency signals, a decrease in percentage of low-frequency signals, and a decrease in low-frequency/high-frequency
ratios during cervical traction with heavy weight, which might suggest a higher vagal activity during traction. However, these
changes were not statistically significant, probably due to the small sample size. Heart rate variability can be affected
by age, sex, ethnicity, and posture.
17–19
Previous studies have suggested that women have predominant vagal control on cardiac regulation
20
and weaker sympathetic control on blood pressure than men.
21
Conclusion
It appears to be safe, in terms of cardiovascular function, to apply the usually recommended traction weight (10% to 20% of
body weight) for cervical traction. The adverse symptoms related to cervical traction in clinical practice are probably not
directly related to the compromise of cardiovascular function and could be due to other causes, such as tension of cervical
paraspinal muscles or pressure to musculoskeletal structures in the chin region such as the jaw or temporomandibular joints
from traction belts. However, heavy traction weight (>30% of body weight) should be applied with caution since blood pressure
can be elevated during traction. It should be avoided in a patient with cardiovascular disease. Further study on a larger
sample of different age groups is required to confirm these findings.
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Demographic Data
|
Group A (n=32)
|
Group B (n=32)
|
Group C (n=32)
|
| Traction weight, kg |
4.8±0.7
a
|
9.9±1.0
b
|
14.4±2.0
c
|
| Mean age, y |
21.4±1.8 |
20.9±1.7 |
21.1±1.5 |
| Mean weight, kg |
48.0±6.5 |
9.5±5.2 |
48.1±6.5 |
| Mean height, cm |
155.0±4.3 |
156.0±5.2 |
154.0±6.2 |
| Mean BMI, kg/m
2
|
20.0±2.7 |
19.5±2.1 |
19.8±3.0 |
Blood Pressure Changes
|
Group A
|
Group B
|
Group C
|
| Mean systolic blood pressure, mm Hg |
|
|
|
| Before traction |
104.6±6.7 |
105.9±9.2 |
102.8±5.3 |
| During traction |
103.8±6.8 |
110.6±6.6 |
121.4±11.6 |
| After traction |
99.3±10.8 |
106.4±8.7 |
110.9±10.9 |
|
P value comparison
a
|
|
|
|
| Before vs during |
>.05 |
>.05 |
<.05 |
| Before vs after |
>.05 |
>.05 |
>.05 |
| During vs after |
>.05 |
>.05 |
>.05 |
| Mean diastolic blood pressure, mm Hg |
|
|
|
| Before traction |
64.0±3.8 |
66.4±2.4 |
66.4±3.9 |
| During traction |
63.9±5.0 |
69.5±6.9 |
78.5±7.6 |
| After traction |
65.4±2.6 |
66.1±6.9 |
69.4±5.8 |
|
P value comparison
a
|
|
|
|
| Before vs during |
>.05 |
>.05 |
<.05 |
| Before vs after |
>.05 |
>.05 |
>.05 |
| During vs after |
>.05 |
>.05 |
<.05 |
Heart Rate Changes
|
Group A
|
Group B
|
Group C
|
| Mean heart rate, beats/min |
|
|
|
| Before traction |
79.9±13.5 |
72.9±7.6 |
82.6±20.3 |
| During traction |
77.8±13.0 |
72.3±8.3 |
70.3±7.6 |
| After traction |
75.6±10.4 |
73.1±8.5 |
78.5±13.5 |
|
P value comparison
a
|
|
|
|
| Before vs during |
>.05 |
>.05 |
>.05 |
| Before vs after |
>.05 |
>.05 |
>.05 |
| During vs after |
>.05 |
>.05 |
>.05 |
Heart Rate Variability Changes
|
Group A
|
Group B
|
Group C
|
| Mean heart rate variability, ms |
|
|
|
| Before traction |
48.8±19.6 |
46.3±15.0 |
48.3±19.2 |
| During traction |
47.8±15.2 |
47.1±13.4 |
68.3±13.1 |
| After traction |
53.6±16.9 |
45.3±14.4 |
59.3±12.5 |
|
P value comparison
a
|
|
|
|
| Before vs during |
>.05 |
>.05 |
<.05 |
| Before vs after |
>.05 |
>.05 |
>.05 |
| During vs after |
>.05 |
>.05 |
>.05 |
High-Frequency Signal, Low-Frequency Signal, and Low-Frequency/High-Frequency Ratio Changes
|
Group A
|
Group B
|
Group C
|
| Mean high-frequency signal, % |
|
|
|
| Before traction |
40.5±19.2 |
47.9±22.9 |
45.6±15.6 |
| During traction |
40.4±22.7 |
45.6±19.2 |
56.6±12.9 |
| After traction |
51.5±24.5 |
41.4±22.0 |
42.8±23.2 |
|
P value comparison
a
|
|
|
|
| Before vs during |
>.05 |
>.05 |
>.05 |
| Before vs after |
>.05 |
>.05 |
>.05 |
| During vs after |
>.05 |
>.05 |
>.05 |
| Mean low-frequency signal, % |
|
|
|
| Before traction |
59.5±19.2 |
52.1±22.9 |
54.4±15.6 |
| During traction |
59.6±22.7 |
54.4±19.2 |
43.4±12.9 |
| After traction |
48.5±24.5 |
58.6±22.0 |
57.3±23.2 |
|
P value comparison
a
|
|
|
|
| Before vs during |
>.05 |
>.05 |
>.05 |
| Before vs after |
>.05 |
>.05 |
>.05 |
| During vs after |
>.05 |
>.05 |
>.05 |
| Low-frequency/high-frequency ratio |
|
|
|
| Before traction |
2.01±1.41 |
1.97±2.25 |
1.46±0.95 |
| During traction |
7.44±16.82 |
1.57±1.09 |
0.85±0.45 |
| After traction |
1.47±1.33 |
2.45±2.42 |
2.39±2.45 |
|
P value comparison
a
|
|
|
|
| Before vs during |
>.05 |
>.05 |
>.05 |
| Before vs after |
>.05 |
>.05 |
>.05 |
| During vs after |
>.05 |
>.05 |
>.05 |