The relationship between lower extremity muscle tightness and pain and disability in individuals with non-specific chronic low back pain

Abstract

BACKGROUND:

Low back pain is a common health issue, and such pains are often associated with muscle tightness. Understanding the link between lower back pain and tight lower extremity muscles is essential for effective pain management and enhanced quality of life.

OBJECTIVE:

The objective of this study was to investigate the relationship between lower extremity muscle tightness and pain and disability in individuals with non-specific low back pain (NSLBP).

METHODS:

A total of 52 individuals with NSLBP were enrolled in this cross-sectional study. Lower extremity muscle tightness was assessed using various clinical tests, including the Active Knee Extension Test, Active Straight Leg Raise, Ober Test, and Modified Thomas Test. Pain intensity and disability were evaluated using the Visual Analog Scale and the Oswestry Disability Index, respectively. Statistical analyses were conducted to assess the correlation between muscle tightness, pain, and disability.

RESULTS:

The study found weak to moderate negative correlations between lower extremity muscle tightness and both pain intensity and disability in individuals with NSLBP (r: –0.287 to –0.526, p < 0.05). Dominant and non-dominant extremities exhibited differences in muscle flexibility, with the dominant extremity showing greater flexibility (p < 0.05).

CONCLUSIONS:

In individuals with NSLBP, lower extremity muscle tightness is closely related to pain severity and disability. These findings suggest that lower extremity muscle tightness plays a significant role in the severity of low back pain and disabilities. Additionally, the observed flexibility difference between dominant and non-dominant extremities warrants further investigation for more personalized treatment approaches.

Keywords

Chronic pain disability evaluation hamstring muscles low back pain lower extremity muscle tightness

1 Introduction

Low back pain (LBP) is a prevalent health concern impacting more than 80% of individuals during their lifetime. Approximately 10% of individuals with LBP have specific identifiable causes, such as lumbar spinal stenosis, spondylolisthesis, spinal fractures, inflammatory diseases, or nerve root compression. However, the remaining 90% of individuals with LBP are diagnosed with non-specific low back pain (NSLBP), where a clear cause cannot be identified [1, 2]. In individuals with NSLBP, certain muscles (hamstrings, iliopsoas, piriformis, and tensor fasciae latae) can become overly active due to the weakness of other muscle groups [2, 3].

The hamstrings are a group of muscles located at the back of the leg, responsible for hip extension and knee flexion. Hip extension plays a vital role in lower back stability and movement. Tightness in the hamstring muscles can lead to lower back pain and worsen LBP symptoms [4, 5].

The iliotibial band (ITB) muscle is a structure that runs along the outer side of the leg, connecting the hip to the knee. The ITB is associated with a group of muscles called the hip muscles, which affect movements starting from the lower back. Therefore, tightness in the ITB can exacerbate LBP symptoms and impact stability in the lower back region [6, 7].

The iliopsoas muscles originate from the front of the spine and extend to the inner side of the pelvic region, enabling hip flexion. Hip flexion can affect movements in the lower back region, and tightness in the iliopsoas muscles can contribute to LBP symptoms in individuals with this condition [3, 8].

The current study aims to clarify the impact of specific muscle groups—hamstrings, ITB, iliopsoas—tightness on NSLBP symptoms, addressing gaps in knowledge within this field. Existing literature suggests that, in most cases, a distinct cause underlying LBP cannot be identified [9]. The significance of the current study lies in its potential to contribute to the development of more effective and personalized treatment strategies for managing LBP. Understanding the correlation between lower extremity muscle tightness and back pain could markedly improve individual assessments and facilitate the development of tailored treatment strategies in clinical practice. In light of this information, the current study aims to examine the relationship between muscle tightness in these areas and the severity of chronic back pain and functional capacity. The current study assumes that there is a relationship between the tightness of lower extremity muscles and the severity of chronic back pain and functional capacity.

2 Methods

2.1 Protocol

This was a cross-sectional prospective study. The study received approval from the KTO Karatay Faculty of Medicine Drug and Non-Medical Device Research Ethics Committee (decision no. 2022/052). The study was conducted on 52 individuals with NSLBP at a private hospital between July and December 2022. Participants were required to provide informed consent before participating in the study. The study adhered to the principles outlined in the Declaration of Helsinki throughout all stages. The current study was reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement to ensure high-quality reporting.

2.2 Participants

The current study included 52 participants aged between 29 and 63 years (Fig. 1). The inclusion criteria for participants were as follows: being between 18 and 65 years of age, voluntary participation in the study, and experiencing low back pain with a pain intensity rating of > 3 on the Visual Analog Scale (VAS) for at least 3 months.

Fig. 1

Flow diagram.

Exclusion criteria included acute arthritis (inflammation, effusion), infectious arthritis, osteomyelitis, malignancies such as multiple myeloma, primary bone tumors, and metastases, severe osteoporosis, joint ankylosis, hypermobile joints, spinal cord compression, myelopathy, and cauda equina syndrome, advanced degenerative changes, radicular root compression causing progressive neurological deficits, acute disc herniations with radiculopathy, rheumatoid arthritis, and other progressive rheumatologic diseases [2, 10].

All procedures were performed in accordance with the Declaration of Helsinki. All participants provided informed consent prior to enrolling in the current study. Each measurement was performed by different experienced physiotherapists blinded to the other assessors.

2.3 Sample size

A total of 10 individuals with NSLBP were included in the pilot study. The G*Power software package (Version 3.0.10, Franz Faul, University of Kiel, Germany) was used to calculate the necessary sample size for the current study. It was determined that a minimum of 47 individuals with NSLBP would be required to achieve 80% statistical power for the study, considering an effect size of r = 0.38, a type I error rate of α= 0.05, and a type II error rate of β= 0.20. To account for potential data loss or attrition, it was decided to include an additional 10 percent of participants in the study.

2.4 Outcome measures

2.4.1 Sociodemographic information

Information about the participants’ age, gender and body mass index was collected.

2.4.2 Pain

Participants’ pain levels were assessed using the VAS. Participants were provided with an explanation of the numerical scale, which ranged from zero to ten on a ten-centimeter line. On this scale, ‘0’ represents the absence of pain, while ‘10’ indicates the most severe pain experienced. Participants were instructed to mark their pain levels both at rest and during physical activity on this 10 cm line [11, 12].

2.4.3 Disability

The Oswestry Disability Index (ODI) was utilized to evaluate the participants’ level of disability associated with their LBP. This scale comprises ten questions, each of which is assigned a score ranging from zero to five. These questions inquire about various aspects, including pain intensity, self-care, lifting, walking, sitting, standing, sleeping, social activities, pain experienced during travel, and the extent to which pain affects daily life. Participants were instructed to select the option that best described their situation. If a person responded to every question, the maximum achievable score would be 50. The final score is calculated using the formula participant’s score / maximum possible score X 100’. The scale has been validated and demonstrated reliability in the Turkish context [13, 14].

2.4.4 Hamstring muscle tightness

The Active Knee Extension (AKE) test was employed to assess hamstring muscle tightness. Participants were positioned in the supine posture in alignment with the AKE test protocol. The non-evaluated leg was extended straight, and the pelvis was secured on the bed using a strap passing over the anterior superior iliac spine. A horizontal bar was positioned above the participant’s hip joint, set at a 90° angle, with the distal thigh making contact with the bar. The researcher then instructed the participant to actively extend the knee while keeping the ankle in a neutral position. Measurement was performed using a smartphone inclinometer, which was placed at the midpoint of the tibia. Participants were guided to extend the knee until they experienced discomfort while maintaining a 90-degree angle of hip flexion. The most stable measurement was recorded as the range of motion in both pre-test and post-test assessments. In this context, the knee joint was considered to have a range of 180° in the vertical plane when the hip was flexed at 90° [15, 16].

Another test employed to evaluate hamstring muscle tightness is the Active Straight Leg Raise (ASLR) test. The ASLR test was conducted on both legs. In this test, the participants were instructed to lie in the supine position and perform hip flexion while keeping the knee fully extended. They were asked to raise their leg until they reached the point where discomfort began. The angle of hip flexion was measured using a smartphone inclinometer application positioned at the midpoint of the femur [17, 18].

2.4.5 Iliotibial band tightness

The Ober Test, a valid and reliable method for assessing iliotibial band tightness, was employed. Individuals with NSLBP were positioned in a side-lying posture with the lower hip and knee flexed, aligning their shoulders, hips, and ankles. The leg to be evaluated was placed on top, while the upper leg was flexed at a 90-degree angle using one hand, and pelvic stabilization was achieved with the other hand. By allowing the evaluated leg to naturally drop into adduction due to the force of gravity, the hip adduction angle was measured. This measurement was taken using a smartphone inclinometer positioned at the midpoint of the lateral surface of the femur [19, 20].

2.4.6 Iliopsoas muscle tightness

The Modified Thomas Test was utilized to assess the flexibility of the hip flexor muscles, specifically the iliopsoas. For the measurement of iliopsoas muscle flexibility, the participant was instructed to lie supine at the edge of the bed and bring both knees towards the chest. This action straightened the lumbar vertebrae and induced posterior pelvic rotation. While ensuring maximal flexion of the contralateral hip using their arms, the participant lowered the tested limb toward the floor. A smartphone was positioned at the midpoint of the femur to capture the angle [19 , 22].

2.5 Statistics

The Statistical Package for the Social Sciences software, version 29 (IBM Corp., Armonk, NY, USA), was used for data analysis. The conformity of the data to a normal distribution was assessed using the Kolmogorov-Smirnov test and the histogram method. Differences in data that conformed to a normal distribution were assessed using the t-test. Results are presented as means, standard deviations, and percentages (%). The relationship between ASLR, AKE, OBER, Modified Thomas, ODI scores, and pain was analyzed using the Pearson correlation test. All statistical analyses were conducted with a significance level set at p < 0.05. For the absolute values of Pearson’s r, the correlations are denoted as follows: 0–0.19 is considered very weak, 0.2–0.39 is considered weak, 0.40–0.59 is considered moderate, 0.6–0.79 is considered strong, and 0.8–1 is considered a very strong correlation [23].

3 Results

Fifty-two participants, ranging in age from 29 to 63 years, were included in the study. Sociodemographic information for the participants is presented in Table 1.

Table 1
Participant’s sociodemographic information

X±SD / n (%)

Age (year) 45.77±8.23

BMI (kg/m²) 27.56±0.78

Gender

Male 15 (28.8)

Female 37 (71.2)

ODI 25.23±3.86

VAS 5.19±0.81

	X±SD / n (%)
Age (year)	45.77±8.23
BMI (kg/m²)	27.56±0.78
Gender
Male	15 (28.8)
Female	37 (71.2)
ODI	25.23±3.86
VAS	5.19±0.81

X: mean, SD: standard deviation, n: number, % : percentange, BMI: body mass index, ODI: oswestry disability index, VAS: visual analog scale.

The values for the dominant limb in the ASLR Test (p < 0.001), AKE Test (p < 0.001), OBER test (p = 0.047), and Modified Thomas Test (p = 0.010) were higher than those for the non-dominant limb (Fig. 2).

Fig. 2

Participants’ degrees of range of motion.

There was a weak negative correlation between dominant ASLR values and ODI scores (r = –0.347, p = 0.012), as well as a moderate negative correlation with pain (r = –0.418, p = 0.002). Similarly, there was a moderate negative correlation between dominant AKE values and ODI scores (r = –0.425, p = 0.002), along with a moderate negative correlation with pain (r = –0.428, p = 0.002). In addition, there was a weak negative correlation between dominant OBER values and ODI scores (r = –0.343, p = 0.013), and a weak negative correlation with pain (r = –0.351, p = 0.011). Lastly, a moderate negative correlation was observed between dominant Modified Thomas values and ODI scores (r = –0.498, p < 0.001), accompanied by a weak negative correlation with pain (r = –0.296, p = 0.033) (Table 2).

Table 2

The relationship between pain, disability and muscle tightness in the dominant extremities of the participants

	ASLR	AKE	OBER	Modified Thomas	ODI	VAS
ASLR	1
AKE	0.719^**	1
OBER	0.123	0.428^**	1
Modified Thomas	0.320^*	0.368^**	0.244	1
ODI	–0.347^*	–0.425^**	–0.343^*	–0.498^**	1
VAS	–0.418^**	–0.428^**	–0.351^*	–0.296^*	0.718^**	1

ASLR: active straight leg raise, AKE: active knee extension test, ODI: oswestry disability index, VAS: visual analog scale, pearson corellation, ^*: p < 0.05, ^**: p < 0.01.

There was a weak negative correlation between non-dominant ASLR values and ODI scores (r = –0.287, p = 0.039), as well as a weak negative correlation with pain (r = –0.349, p = 0.011). Similarly, there was a moderate negative correlation between non-dominant AKE values and ODI scores (r = –0.419, p = 0.002), along with a moderate negative correlation with pain (r = –0.441, p = 0.001). In addition, a weak negative correlation was observed between non-dominant OBER values and ODI scores (r = –0.298, p = 0.032), accompanied by a weak negative correlation with pain (r = –0.345, p = 0.012). Lastly, a moderate negative correlation was found between non-dominant Modified Thomas values and ODI scores (r = –0.526, p < 0.001), along with a weak negative correlation with pain (r = –0.341, p = 0.013) (Table 3).

Table 3

The relationship between pain, disability and muscle tightness in the non-dominant extremities of the participants

	ASLR	AKE	OBER	Modified Thomas	ODI	VAS
ASLR	1
AKE	0.650^**	1
OBER	0.127	0.414^**	1
Modified Thomas	0.252	0.395^**	0.220	1
ODI	–0.287^*	–0.419^**	–0.298^*	–0.526^**	1
VAS	–0.349^*	–0.441^**	–0.345^*	–0.341^*	0.718^**	1

ASLR: active straight leg raise, AKE: active knee extension test, ODI: oswestry disability index, VAS: visual analog scale, pearson corellation, ^*: p < 0.05, ^**: p < 0.01.

4 Discussion

The current study aimed to investigate the relationship between lower extremity muscle tightness and the severity of LBP and disability in individuals with NSLBP. The findings suggest that lower extremity muscle tightness may be associated with both LBP and functional limitations.

An important finding of the current study is the existence of flexibility differences between the non-dominant and dominant extremities. The findings of the current study indicate that the dominant extremity is more flexible than the non-dominant extremity. While the results of the current study align with some studies in the literature [24], some studies suggest the opposite [25, 26]. The result observed in the current study may be attributed to the increased activity of the individuals’ dominant legs. It is essential to note that this flexibility difference allows us to assess lower extremity muscle tightness in individuals with LBP. Understanding the flexibility difference between the non-dominant and dominant extremities may help us better comprehend the impact of lower extremity muscles on LBP. This finding suggests that rehabilitation strategies focusing on improving flexibility in the non-dominant extremity could potentially be more effective for individuals with LBP. It can be hypothesized that flexibility-enhancing exercises and treatment methods targeting the non-dominant extremity may contribute to alleviating pain symptoms and promoting functional improvement. However, the precise causes of this flexibility difference and its impact on LBP require further investigation. Additionally, more research is needed to determine how the flexibility difference between the non-dominant and dominant extremities can be applied in clinical practice.

The results of the current study confirm that lower extremity muscle tightness is a prevalent finding in individuals with NSLBP. The tightness of hamstring muscles, the ITB, and iliopsoas muscles shows a positive correlation with the severity of pain. These findings suggest that the flexibility and tightness of lower extremity muscles may play a significant role in the management of LBP.

Prior research has established a relationship between the AKE and the ASLR tests [27], which aligns with current findings. The current study corroborates the significance of these tests as crucial tools for evaluating the condition of lower extremity muscles in individuals with LBP. While some studies in the literature support the association between hamstring muscle tightness and LBP [28, 29] others have not found such a connection [30, 31]. For individuals experiencing LBP during the AKE Test, reduced joint mobility is observed, particularly an increase in hamstring muscle tightness, which can exacerbate back pain symptoms [5, 25]. Similarly, the results of the ASLR Test have been associated with lower extremity muscle tightness in individuals with LBP [32]. These clinical tests can assist in evaluating individuals with LBP and determining treatment strategies. Understanding the anatomy of the biarticular hamstring muscles contributes to a better comprehension of the results of these tests. Furthermore, it can provide more guidance on how rehabilitation and flexibility-enhancing exercises targeting hamstring muscles may alleviate pain symptoms. Furthermore, the correlation observed between ASLR outcomes and tightness in the lower extremity muscles among individuals experiencing low back pain may not solely stem from muscular tightness. Neural tension along the sciatic nerve could significantly contribute to the reported challenges in lifting the leg and the perceived increase in muscle tightness during the test [33]. Therefore, the results of the ASLR test in individuals with low back pain should be interpreted taking into account the potential effect of neurodynamics.

In current study, the Ober test, used to assess ITB tightness, has also been linked to LBP and disability. There are studies in the literature that associate ITB tightness with back pain [25 , 35]. The ITB receives fascial contributions from the deep fascia of the thigh, as well as muscles like the gluteus maximus and tensor fasciae latae at its proximal thigh region. Due to these anatomical connections, ITB tightness can lead to increased back pain symptoms and functional limitations. The results of the Ober test further strengthen the relationship between ITB tightness and back pain. Therefore, evaluating ITB tightness may be necessary as part of back pain treatment plans. Rehabilitation and flexibility-enhancing exercises targeting these structures can assist in alleviating back pain symptoms.

According to the findings of current study, the assessment of iliopsoas muscle tightness through the Modified Thomas test has also been associated with back pain and functional capacity. Iliopsoas muscles are significant muscles that originate from the front of the spine and extend to the inner region of the pelvis. These muscles play a crucial role in hip flexion and spinal stabilization. Studies have indicated that tightness in the iliopsoas muscle can exacerbate pain symptoms and lead to functional limitations [25, 36]. The results of the Modified Thomas test highlight the importance of considering iliopsoas muscle tightness in the management of LBP and suggest that rehabilitation strategies aimed at improving the flexibility of these muscles may be valuable for individuals with NSLBP.

However, consideration of certain limitations in the current study is essential. Since this is an observational study, establishing definitive cause-and-effect relationships is challenging. Additionally, there are limitations associated with the tests and measurement methods used in the current study. Further research, including more randomized controlled trials and larger sample sizes, will contribute to a more detailed understanding of these relationships.

5 Conclusion

The current study has shed light on the relationship between lower extremity muscle tightness and the severity of pain and disability in individuals with NSLBP. The current findings emphasize the importance of evaluating the flexibility and tightness of lower extremity muscles in LBP treatment plans. Exercises aimed at reducing or managing lower extremity muscle tightness, manual therapy, or other rehabilitation strategies may assist in alleviating pain symptoms and promoting functional recovery. Additionally, the observed flexibility difference between the non-dominant and dominant extremities should be regarded as an intriguing finding and may provide guidance for future research. This finding could contribute to the development of more tailored and individualized approaches to LBP management. Moreover, further exploration into the relationship between lower extremity muscle tightness, pain, and disability is necessary for a comprehensive understanding.. Such research has the potential to facilitate the development of more effective and personalized treatment strategies for LBP, ultimately enhancing the quality of life for individuals with LBP.

Ethical approval

This study was approved by KTO Karatay University Faculty of Medicine Drug and Non-Medical Device Research Ethics Committee with decision number 2022/052.

Informed consent

Informed consent was obtained from all participants for being included in the study.

Conflict of interest

The authors have no conflict of interest to declare related to the present manuscript.

Footnotes

Acknowledgments

Thank you to all participants.

Funding

The authors report no funding.

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