Relationships between alexisomia and the presence of latent trigger points in the upper trapezius of healthy volunteers

Abstract

BACKGROUND:

Alexisomia is characterized by difficulties in the awareness and expression of somatic feelings. Trigger points are classified into two types, active and latent, according to the presence or absence of identifying spontaneous pain.

OBJECTIVE:

We aimed to examine the association between alexisomia and the presence of latent trigger points (LTrPs) in the upper trapezius of healthy volunteers.

METHODS:

This study was designed as a cross-sectional survey. A correlation analysis between the Shitsu-Taikan-Sho Scale (STSS) and LTrPs was performed on 154 healthy volunteers. The LTrP odds ratio for healthy volunteers with alexisomia was selected as the primary endpoint.

RESULTS:

LTrPs were seen in the upper trapezius of 82 healthy volunteers (53.2%). There was no significant difference between the LTrP and non-LTrP groups in STSS total score ( $p=$ 0.11). However, there was a significant difference between them in STSS difficulty of identifying bodily feelings (DIB) score ( $p=$ 0.03). In the alexisomic versus non-alexisomic groups, the LTrP odds ratio for STSS total score was 2.30 (95% confidence interval [CI] 1.03–5.10) and for STSS DIB score, 2.08 (95% CI 1.05–4.11).

CONCLUSIONS:

In STSS DIB in particular, alexisomia was associated with the presence of LTrP in the upper trapezius of healthy volunteers.

Keywords

Latent trigger point upper trapezius alexisomia difficulty in identifying bodily feelings over-adaptation

1. Introduction

Alexisomia is one of the characteristics of psychosomatic patients and is characterized by difficulties in the awareness and expression of somatic feelings [1]. The following senses are impaired in alexisomia, resulting in reduced awareness: (1) senses that are necessary to maintain homeostasis (such as hunger and somnolence); (2) senses associated with adaptive processes to changes in environment that subjects normally feel as warning signs (such as fatigue); and (3) senses that accompany physical diseases; i.e., subjective symptoms such as chill and pain. Alexisomia also tends to suppress behaviors based on bodily feelings in order to respond to social demands, even though the senses are identified [1].

In psychosomatic patients, a significant negative correlation exists between objective physiological indicators and subjective feelings of physical tension in stress loading [2]. When building up a strong sense of tension, psychosomatic patients no longer feel a sense of relaxation. One study indicates that if this phenomenon occurs, psychosomatic patients experience problems with identifying bodily feelings [2]; another study reports that gastric motility in healthy volunteers could potentially be reduced even though their pain would be bearable [3]. This result suggests that psychosomatic patients as well as healthy people with alexisomia may not recognize latent objective physiological observations during stress loading as a warning sign, which may lead to the development of serious functional diseases. Despite this background, to date no study has examined the relationship between alexisomia and the latent objective physiological observations in healthy volunteers.

A trigger point (TrP) represents objective physiological observations in the upper trapezius, highly frequent in patients with neck or shoulder pain (35%–80%) [4]. The presence of TrPs is an essential diagnostic criterion for myofascial pain syndrome (MPS) [5, 6, 7], a common psychosomatic disorder. The reference criteria for MPS include the items relevant to stress; furthermore, some studies report that MPS is associated with biopsychosocial factors such as depression and anger [7, 8, 9].

TrPs are classified into two types, active and latent, according to the presence or absence of spontaneous pain. In latent TrP (LTrP), hyperirritability is found in a taut muscle band, which is clinically associated with tenderness and/or referred pain that is distant from the TrP site following manual examination [10]. An LTrP that is activated by long-lasting unpleasant stimuli undergoes a transition to active TrP (ATrP) [10]. Because the standard of care for the treatment of ATrPs has not yet been determined, preventive care in the latent stage of TrPs is extremely important.

In healthy volunteers, alexithymia was reportedly associated with the presence of LTrPs [11]. Alexisomia, a condition involving difficulties in the awareness and expression of somatic feelings, has an inseparable relationship with alexithymia, which is a condition involving difficulties in the awareness and expression of mental feelings [12]. We hypothesized that healthy volunteers with alexisomia could not recognize a sense of myofascial hypertonicity as a warning sign owing to the condition of having difficulties in the awareness and expression of somatic feelings and suppressed behaviors based on bodily feelings, which tended to lead to the formation of LTrPs.

We aimed to examine the association between alexisomia and the presence of LTrPs in the upper trapezius of healthy volunteers. To the best of our knowledge, relationships among alexisomia and LTrP in healthy volunteers have not been reported. In addition, there has been no investigation on the relationship between these two factors and the pressure pain threshold (PPT). Clarification of any such relationships will contribute to preventive medicine in the fields of psychosomatic disease and chronic pain such as MPS.

2. Materials and methods

2.1 Design

This study was designed as a cross-sectional survey of healthy volunteers who work at university hospitals in Osaka, a metropolis in western Japan. Demographic information, including sex, age, and body mass index, as well as measures of self-reported questionnaires regarding alexisomia, were obtained from each participant. All participants underwent manual examination of their upper trapezius to identify LTrPs. Subsequently, they were measured by a digital algometer to evaluate the PPT.

2.2 Outcomes

The primary endpoint of the present study was the LTrP odds ratio for healthy volunteers with alexisomia. The secondary endpoints were the ratio of alexisomia and LTrP in healthy volunteers, and correlation coefficients between alexisomia and the LTrP and PPT.

2.3 Participants

A total of 154 healthy volunteers (75 males and 79 females; mean age 38.0 $\pm$ 11.7 years; age range 21–67 years) participated in the study between June and September 2019. All participants were either employees at the Kansai Medical University Hospital or Kindai University Hospital. Three exclusion criteria were applied for participants: those who (1) were taking medication or undergoing hospital treatment; (2) had a history of, or surgery for, neck, shoulder, or arm disorders; and (3) had neurological disorders such as cognitive dysfunction whereby they were unable to communicate.

2.4 Measures

2.4.1 Self-report questionnaire

Each participant was evaluated for potential alexisomic symptoms based on the Shitsu-Taikan-Sho Scale (STSS total), a self-report questionnaire consisting of 23 items rated on a scale of 1 to 5, which provides a total score ranging between 23 and 115 (Table 1). The STSS total includes the following three subcategories: difficulty in identifying bodily feelings (DIB), over adaptation (OA), and lack of health management on bodily feelings (LHM). The DIB subcategories consist of questions about the tendency to fail in identifying bodily feelings that act as warning signals that emerge from the body during adaptation to external environments and are necessary to maintain homeostasis of the body. The OA subcategories consist of questions on the tendency to ignore warning signals from the body that results from prioritization to meet social demands and adapt to external environments. The LHM subcategories consist of questions on habits related to daily management of health and bodily sensations that arise from physical conditions as a result of the relaxation response.

Table 1
Shitsu-Taikan-Sho Scale (STSS)

The following statements concern your physical condition and habits. For each statement, please circle the response that
best describes your usual condition.
	Definitely false	Mostly false	Don’t know	Mostly true	Definitely true
1. People tell me that I am overworking even if I don’t feel so.
	( )	( )	( )	( )	( )
2. I am careful about my physical condition.
	( )	( )	( )	( )	( )
3. I prioritize work (including housework and schoolwork) even if I know that rests are necessary.
	( )	( )	( )	( )	( )
4. I try to do something for a change of pace.
	( )	( )	( )	( )	( )
5. People tell me that I should relax even if I feel that I am.
	( )	( )	( )	( )	( )
6. I don’t want to rest even if I am tired.
	( )	( )	( )	( )	( )
7. I work (including housework and schoolwork) even if I have a fever.
	( )	( )	( )	( )	( )
8. I notice that my physical condition is bad before I get sick.
	( )	( )	( )	( )	( )
9. I am careful about my diet.
	( )	( )	( )	( )	( )
10. I don’t think I am tired, but people ask me if I am.
	( )	( )	( )	( )	( )
11. I feel relaxed when I take a bath.
	( )	( )	( )	( )	( )
12. I don’t feel full when I eat.
	( )	( )	( )	( )	( )
13. I don’t rest even if my physical condition is bad.
	( )	( )	( )	( )	( )
14. People tell me that I look tense even if I don’t think I am.
	( )	( )	( )	( )	( )
15. I don’t feel tired.
	( )	( )	( )	( )	( )
16. I try to exercise moderately.
	( )	( )	( )	( )	( )
17. I don’t care about my physical condition when I work (including housework and schoolwork).
	( )	( )	( )	( )	( )
18. People tell me that I will ruin my health even if I feel fine.
	( )	( )	( )	( )	( )
19. I cannot tell if I am tense or not.
	( )	( )	( )	( )	( )
20. I prioritize my work (including housework and schoolwork) over sleep.
	( )	( )	( )	( )	( )
21. I feel calm when I take deep breaths.
	( )	( )	( )	( )	( )
22. I don’t rest even if I want to.
	( )	( )	( )	( )	( )
23. I don’t know how to manage my physical condition.
	( )	( )	( )	( )	( )

The mean score of STSS total among Japanese undergraduate students was 56.3 $\pm$ 10.2 points. The DIB is made up of nine questions: 1, 5, 6, 10, 12, 14, 15, 18, and 19. Participants scored 18.1 $\pm$ 5.6 points. OA is made up of six questions, 3, 7, 13, 17, 20, and 22, and scored 14.2 $\pm$ 4.5 points. LHM is made up of eight questions, 2, 4, 8, 9, 11, 16, 21, and 23, of which only 23 is a regular score, all the others being reversely scored items. The average LHM score was 21.4 $\pm$ 3.8 points. Adequate validity and reliability of the STSS has been reported in healthy volunteers in previous studies, with a Cronbach’s $\alpha$ of 0.83 (DIB, 0.84; OA, 0.83; LHM, 0.70) [13, 14]. “The mean $+$ one standard deviation” was defined as the cutoff value. Based on this definition, the participants were classified into one of two groups: non-alexisomic (score $\leqslant$ 66) and alexisomic (score $\geqslant$ 67).

2.4.2 LTrP palpation procedure

In the present study, TrPs were diagnosed when the participants met all of the following four criteria: (1) the presence of a tender spot in a taut band; (2) self-recognition of pain on a tender spot following palpation; (3) the presence of a predicted pain referral pattern (the pain distribution expected from a trigger point in the muscle); and (4) the existence of a local twitch response (transient local contraction of skeletal muscle fibers in response to palpation). These criteria, also known as Simons’ criteria, are essential for a proper TrP diagnosis [5, 6]. As previously stated, TrPs are divided into latent and active forms, with spontaneous pain deriving from ATrPs, the primary difference between the two forms. Based on a previous report, LTrPs were defined in the present study as the focus of hyperirritability in taut muscle bands, which is clinically associated with tenderness and/or referred pain distant from the LTrP site following manual examination [15].

Each participant was individually evaluated for LTrPs by palpation with the thumb. The diagnosis of TrPs requires careful manual examination, which is considered a highly reliable procedure [16]. The palpation target area was limited to both sides of the upper trapezius and did not include other scapular muscle groups such as the lower trapezius, supraspinatus, serratus anterior, and rhomboideus. The most commonly tested muscle is the upper trapezius because of the high prevalence of TrP in that muscle and easy access to the taut band [17, 18]. Palpation was performed with each participant in a relaxed sitting position. The palpation area was approximately 3 cm wide (horizontal) and 2 cm in height (vertical). Once a taut band was identified, further palpation along the taut band was performed to search for local twitch responses. After the palpation search had been completed, we asked each participant whether they felt any local or referred pain during manual compression. All palpation examinations were performed by one of five expert clinicians who had more than 5 years of experience in the diagnosis and treatment of MPS and specifically TrPs.

2.4.3 Assessment of the PPT

The PPT is defined as the minimum level of pressure at which the pressure sensation begins to transition to pain. A digital algometer (Digital Force Gauge, model RZ-20; Aikoh Engineering, Osaka, Japan) was used to measure the PPT. The pressure algometer has a linear response to force application between 0 and 1,300 kPa. We measured this by applying a 1-cm ${}^{2}$ diameter attachment of the digital algometer to the skin of participants in a relaxed sitting position. The PPT was assessed bilaterally at the intertransverse space at C5–C6 [18, 19].

2.5 Statistical analysis

All results are reported as means with standard deviation, 95% confidence intervals (95% CI), ranges, or frequency distribution (%), as appropriate. Participants were classified into LTrP and non-LTrP groups based on the aforementioned cutoff score. We used the Wilcoxon rank-sum and chi-square tests to analyze demographics, STSS scores, and PPT scores because these data were not normally distributed. We analyzed associations between LTrP incidence and demographics, STSS scores, and PPT scores using the Mann-Whitney U test. The LTrP odds ratio for alexisomia was determined. In addition, Spearman’s rank correlation coefficients between the STSS total score, STSS DIB score, STSS OA score, STSS LHM score, and PPT score and age, sex, body mass index, and presence of LTrP were calculated.

Table 2
Latent trigger points incidence and sociodemographic information

	LTrP incidence		$p$ -value
	LTrP	No LTrP
Number of subjects	82	72
Sex, male	35	40	0.11
Age, years, mean (SD)	38.6 (11.0)	38.4 (10.5)	0.98
BMI, mean (SD)	22.3 (3.6)	22.5 (4.0)	0.72

SD: Standard deviation; LTrPs: Latent trigger points; BMI: Body mass index.

Table 3

Relationship between the presence of latent trigger points and mean scores of the Shitsu-Taikan-Sho Scale score and pressure pain threshold

	LTrP incidence								$p$ -value
	LTrP ( $n=$ 82)				No LTrP ( $n=$ 72)
	Mean	SD	Median	IQR	Mean	SD	Median	IQR
STSS total score	59.6	11.3	61	50–67	56.8	10.3	56	51–62	0.11
DIB score	21.3	5.8	22	17–26	19.5	5.3	18	16–23.5	0.03 ${}^{*}$
OA score	18	5.1	18	14–22	17.8	4.4	17	14–21.5	0.78
LHM score	20.2	4	20	17–24	19.6	4.5	19	17–22	0.4
PPT score	39.9	17.5	37.4	28.2–45.7	38.9	17.3	34.4	27.1–47.2	0.59

SD: Standard deviation; IQR: Interquartile range; LTrPs: Latent trigger points; STSS: Shitsu-Taikan-Sho Scale; DIB: Difficulty of identifying bodily feelings; OA: Over-adaptation; LHM: Lack of health management based on bodily feelings; PPT: Pressure pain threshold.

A $p$ value of less than 0.05 was considered statistically significant. Statistical procedures were conducted using IBM SPSS Statistics version 25 (SPSS, Chicago, IL, USA).

3. Results

The incidence of LTrPs and sociodemographic information for all participants are shown in Table 2. LTrPs were observed in the upper trapezius of 82 participants (53.2%). There was no statistically significant difference in sex, age, or body mass index between the LTrP groups. Group means for the STSS total, STSS DIB, STSS OA, STSS LHM, and PPT for both the LTrP and non-LTrP groups are shown in Table 3.

A test of independence between the presence of LTrPs and the STSS total score resulted in a chi-square of 4.27 ( $p=$ 0.04), indicating that both factors correlate with one another. The analysis of the DIB score showed a similar result of a chi-square of 4.47 ( $p=$ 0.03). Numbers of participants for the presence or absence of LTrPs for both the alexisomic and non-alexisomic groups are shown in Table 4. Alexisomia was found in 35 participants (22.7%). In the alexisomic versus non-alexisomic groups odds ratio was 2.30 (95% CI 1.03–5.10) for LTrPs and 2.08 (95% CI 1.05–4.11) for STSS DIB scores. There was no correlation between the presence of LTrPs and the PPT, or between the STSS total score and PPT, age, sex, body mass index, or presence of LTrPs (Table 5).

4. Discussion

To the best of our knowledge, this is the first report suggesting the association between alexisomia and the presence of LTrPs in the upper trapezius of healthy volunteers. In comparison with previous studies of healthy undergraduate students, the present study showed that the mean score of STSS total was higher, while in subscales only the mean score of STSS LHM was lower [13, 14], perhaps because our participants are healthy volunteers who work at university hospitals and have potentially been involved in their own health management. Furthermore, previous studies showed that the proportion of LTrPs in the upper trapezius was in a range of 30.0%–47.5% [3, 8], compared with 53.2% in the present study, possibly because we evaluated a group of healthy volunteers who experienced hypertonicity in the upper trapezius resulting from mechanical or psychological factors.

Table 4
The number of participants for the presence or absence of LTrPs for both the alexisomic and non-alexisomic groups

	LTrPs		Total
	Present	Not present
Alexisomic group (STSS total	24	11	35
score $\geqq$ 67)
Non-alexisomic group (STSS	58	61	119
total score $<$ 67)
Total	82	72	154

SD: Standard deviation; LTrPs: Latent trigger points; STSS: Shitsu-Taikan-Sho Scale.

Table 5

Correlation coefficient between the Shitsu-Taikan-Sho Scale, pressure pain threshold, sociodemographic variables and presense of latent trigger point. n.s not significant, ${}^{*}p<$ 0.05, ${}^{**}p<$ 0.01

	STSS Total	STSS DIB	STSS OA	STSS LHM	PPT		Age		Sex, male		BMI		Presence of LrTP
STSS Total		0.85 ${}^{**}$	0.76 ${}^{**}$	0.59 ${}^{**}$		0.07 ${}^{\text{ns}}$		0.07 ${}^{\text{ns}}$	$-$	0.01 ${}^{\text{ns}}$	$-$	0.04 ${}^{\text{ns}}$		0.13 ${}^{\text{ns}}$
STSS DIB			0.50 ${}^{**}$	0.29 ${}^{**}$		0.15 ${}^{\text{ns}}$		0.13 ${}^{\text{ns}}$		0.06 ${}^{\text{ns}}$	$-$	0.01 ${}^{\text{ns}}$		0.16 ${}^{*}$
STSS OA				0.14 ${}^{\text{ns}}$	$-$	0.03 ${}^{\text{ns}}$		0.20 ${}^{**}$		0.02 ${}^{\text{ns}}$		0.06 ${}^{\text{ns}}$		0.03 ${}^{\text{ns}}$
STSS LHM						0.02 ${}^{\text{ns}}$	$-$	0.21 ${}^{**}$	$-$	0.10 ${}^{\text{ns}}$	$-$	0.04 ${}^{\text{ns}}$		0.07 ${}^{\text{ns}}$
PPT								0.10 ${}^{\text{ns}}$		0.32 ${}^{**}$		0.08 ${}^{\text{ns}}$		0.03 ${}^{\text{ns}}$
Age										0.05 ${}^{\text{ns}}$		0.05 ${}^{\text{ns}}$		0.01 ${}^{\text{ns}}$
Sex,male												0.40 ${}^{**}$	$-$	0.13 ${}^{\text{ns}}$
BMI													$-$	0.03 ${}^{\text{ns}}$

SD: Standard deviation; STSS: Shitsu-Taikan-Sho Scale; DIB: Difficulty of identifying bodily feelings; OA: Over-aduptation; LHM: Lack of health management based on bodily feelings; PPT: Pressure pain threshold; LTrPs: Latent trigger points; BMI: Body mass index.

One of the important points arising from the present study is the possible relationship between alexisomia and the presence of LTrPs in the upper trapezius of healthy volunteers. In the subscales of STSS, only STSS DIB was significantly correlated with the presence of LTrPs. This result supports a part of our hypothesis, namely, “healthy volunteers with alexisomia could not recognize a sense of myofascial hypertonicity as a warning sign owing to the condition of having difficulty in the awareness and expression of identifying somatic feelings, which tended to lead to the formation of LTrPs.” In our cross-sectional survey, it is difficult to assess the causality among these factors. The practical implications of our study is limited to the appeal of the existence of alexisomia in the field of LTrPs. Further clarification of such relationships will contribute to the development of preventive medicine for psychosomatic diseases and chronic pain conditions, such as MPS.

There was no difference between the means and SDs of the STSS total scores between the LTrP group and the non-LTrP group. Nevertheless, the LTrP group involved a higher proportion of participants with high alexisomia tendency than the non-LTrP group. This indicates that the LTrP group had a certain number of participants with severe difficulty in identifying bodily feelings.

In the non-alexisomic group, half of the participants had LTrPs, perhaps because an LTrP harbors many risk factors other than alexisomia. Regarding biopsychosocial factors, some studies reported that LTrPs are related to depression and alexithymia [8, 11]. ATrPs, however, are related to ergonomic factors (e.g., repetitive movement) and structural factors (e.g., scoliosis) [20].

Another important point worthy of mention is that subscales of STSS other than DIB were not correlated with the presence of LTrPs in the upper trapezius of healthy volunteers. OA, in particular, was significantly correlated with DIB but was not correlated with LTrP. A study focusing on healthy volunteers reported that OA affects the autonomic nervous function but has no effect on somatic symptoms [21]. The participants in the present study were healthy volunteers working at university hospitals. If the participants were healthy volunteers of occupations that were more susceptible to cervical physical factors, OA might be correlated with LTrP.

In the present study, PPT showed no correlation with both the presence of LTrPs and alexisomia. These results do not support the following hypothesis: “the pain threshold appeared to be a mediating factor associated with alexisomia and LTrPs because the condition whereby a sense of myofascial hypertonicity becomes unrecognizable as a warning sign led to an increase in pain threshold.” In our cross-sectional survey, it is difficult to assess the causality among these factors. One possible reason for this is that when PPT increases, a sense of myofascial hypertonicity becomes unrecognizable, resulting in failure to respond, and this failure may lead to the formation of an LTrP. Diagnostic criteria for LTrPs include “self-recognition of pain on a tender spot following palpation” [5, 6]. When PPT increases, palpation-induced oppressive pain becomes unrecognizable, which may produce a false-negative result.

This study is not without limitations. First, it was cross-sectional so causation cannot be implied. Second, the STSS has good reliability and validity and is positively correlated with alexithymia; however, its cutoff values have not been standardized [13, 14]. In the present study, the proportion of healthy volunteers with alexisomia was 22.7%. In our previous study conducted in the same facility, the proportion of healthy volunteers with alexithymia was 23.8%. Finally, PPT values in the non-LTrP group were used to measure pain thresholds at cervical levels of the spine. Given that the validity of algometry in measuring PPT has been confirmed [22], if we had measured PPT in the LTrP group, a relationship with alexisomia could have been possible even though the number of participants had been reduced by half.

5. Conclusions

Particularly in STSS DIB, alexisomia was associated with the presence of LTrP in the upper trapezius of healthy volunteers. Further clarification of such relationships will contribute to the development of preventive medicine for psychosomatic diseases and chronic pain conditions, such as MPS.

Footnotes

Acknowledgments

We thank Hugh McGonigle from Edanz Group (www.edanzediting.com/ac) for editing a draft of the manuscript.

Conflict of interest

The authors declare that they have no competing interests.

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Relationships between alexisomia and the presence of latent trigger points in the upper trapezius of healthy volunteers

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1. Introduction

2. Materials and methods

2.1 Design

2.2 Outcomes

2.3 Participants

2.4 Measures

2.4.1 Self-report questionnaire

Table 1 Shitsu-Taikan-Sho Scale (STSS)

2.4.3 Assessment of the PPT

2.5 Statistical analysis

Table 2 Latent trigger points incidence and sociodemographic information

4. Discussion

Table 4 The number of participants for the presence or absence of LTrPs for both the alexisomic and non-alexisomic groups

Footnotes

Acknowledgments

Conflict of interest

References

Table 1
Shitsu-Taikan-Sho Scale (STSS)

Table 2
Latent trigger points incidence and sociodemographic information

Table 4
The number of participants for the presence or absence of LTrPs for both the alexisomic and non-alexisomic groups