Effects of hamstring stretching using pressure bio feedback unit in patients with low back pain

Abstract

Background: Hamstring tightness can alter lumbar posture, impact pelvic alignment, and exacerbate low back pain. It's important to research whether hamstring stretches with a pressure biofeedback unit work for those with low back pain.

Objectives: To determine the effects of hamstring stretching using a pressure biofeedback unit in patients with low back pain.

Methodology: A total of n=38 Male and female subjects between the ages of 25-40 years, with >3 months history of low back pain having bilateral hamstring shortening less than 70O, and (ODI) score between 20% to 40% were enrolled in the study. The data was collected from Railway General Hospital and randomly assigned into 2 groups. Group A (n=18) received Active Hamstring stretch with a pressure biofeedback unit (PBU). Group B (n=19) received only Active Hamstring stretch without PBU Outcome measures such as pain, hamstring length, and ODI score were measured at baseline, after the second and fourth weeks. The data was entered and evaluated by using SPSS-25.

Results: The results of this study showed no significant difference between group A and group B for ODI individual items as well as ODI overall score p≥0.05. Moreover, no significant difference in NPRS score p≥0.05. however, it showed a significant difference (p<0.05) in hamstring muscle length on both legs p<0.01.

Conclusion: It is concluded that hamstring stretching using a PBU causes a greater improvement in the flexibility of hamstring muscles as compared to the flexibility of hamstrings when stretched without PBU.

Keywords: flexibility; hamstring muscle; low back pain; pressure bio feedback

ClinicalTrials.gov Identifier: NCT05059496

INTRODUCTION

Low back ache remains a particularly common physical structure illness that takes place in 80% of individuals at a certain point in their lifespans [1, 2]. Low back pain causes limited compliance and several physical structure disorders resulting from muscle stiffness and postural instabilities. For the proper functioning of the musculoskeletal system, flexibility is a vigorous part of maintaining fitness and maximizing physical activity performance. Dysfunction in flexibility is a common issue encountered by sportsmen as well as normal individuals, particularly of hamstring muscles. Decreased flexibility causes the beginning of a vicious cycle which results in a decreased range along with increased postural complications [3].

 Research showed that hamstring muscle flexibility is significantly decreased in people with nonspecific low back pain, which affects anterior pelvic rotation and forward bending range. Low back pain may be exacerbated by increased lumbar flexion brought on by decreased hamstring flexibility. While people experiencing low back pain have shorter hamstring muscles [4,5,6].

Studies conducted by Shrivastava et. al, and Han et. al. on the effect of hamstring stretches while maintaining pelvic control on low back pain, find that hamstring stretching exercises while maintaining pelvic control are more useful in alleviating lower back discomfort [7, 8]. Patients with back pain can benefit from proprioceptive neuromuscular facilitation (PNF), ballistic, static, and other stretching treatments to increase the flexibility of their hamstrings.  a study suggested using a PBU to keep the pelvic anterior tilting position when performing the AKE test or AKE stretching for length test and hamstring muscle stretching [9].

Previous studies demonstrate that stretching with an anterior pelvic tilt may be more effective for hamstring length than a posterior pelvic tilt. While maintaining pelvic tilt during stretching sessions can be facilitated using devices such as pressure biofeedback units (PBUs), their efficacy in this regard is still unknown. So, this study aims to find out whether hamstring stretching while maintaining anterior pelvic tilt using pressure biofeedback is more effective than hamstring stretching without using pressure biofeedback on pain, muscle length, and functional status of patients with low back pain.

METHODOLOGY

The single-blinded randomized controlled trial (NCT05059496) study was conducted at Railway General Hospital from February to November 2021. The study was conducted at the physical therapy department of Pakistan Railway Hospital. The ethical approval was obtained from the Research and Ethical Committee (RIPHAH/RCRS/REC/Letter-00854) of Riphah International University, Islamabad Pakistan.

Male and female subjects between the ages of 25-40 years, with >3 months history of mild to moderate low back pain having bilateral hamstring shortening less than 70^O, and (ODI) score between 20% to 40% were enrolled in the study. Patients with osteoarthritis or spondylolisthesis, systemic disease, disc herniation or leg length discrepancy, pregnant females, and participants with severe back pain or excessive lumber lordosis were excluded.

 The G Power software was used to determine the sample size. The effect size (Cohen's d=0.92) obtained from a prior study was used to calculate the sample size of n=38. During the calculation, the power (1-β) was 85% and the alpha level was kept at 0.05 to achieve the sample size [8].

The nonprobability convenience sampling technique was used for sample selection. A total of n=90 subjects were evaluated for eligibility criteria. Out of which n=52 patients were excluded due to not meeting the selection criteria (n=45) and declining to participate (n=7) in the study. From n=38 participants equally allocated to Group A (n=19) receiving Active Hamstring stretch with pressure biofeedback unit (PBU) and Group B (n=19) receiving stretching exercise without pressure biofeedback unit There were n=2 loss of follow up from both groups due to lack of adherence with research protocols. A total of n=34 participants completed the study and were included in the data analysis. (Figure 1)

Figure 1: CONSORT

The randomization was done through the flip-coin method. In this method, a coin was tossed in the air. If it lands on one side (head), it represents Group A, and if it lands on the other side (tail), it represents Group B. This method was used repeatedly to assign participants to their respective groups. The patients were blinded in the study and unaware of the group being allocated.

Both groups received a hot pack for 15 min before the stretching protocol and TENS for 15 min after the stretching protocol over the lumber area in prone lying. Group A received an Active Hamstring stretch with PBU maintained at 40mmHg pressure performed 3 times for each leg with a 30-sec hold and 15-sec rest between each stretch 3 days a week. Group B performed Active Hamstring stretch without PBU performed 3 times for each leg with a 30-second hold and 15-second rest between each stretch 3 days a week. The total treatment session was 35 minutes. Numeric Pain Rating Scale (NPRS) was used to measure pain scores. The Oswestry Disability Index was used to measure pain-related disability in persons with low back discomfort It contains a total of 10 items, and each item is scored from 0 to 5. The overall score is calculated by multiplying the sum of the scores by 2, giving a scale of 0 to 100[10].

An active knee extension test (AKE) was used to measure hamstring elasticity. To perform this test patient is positioned in a supine lying and a pillow is placed under the patient's head and neck. The non-tested lower extremity is stabilized with the help of straps along the table. The goniometer axis is placed on the knee axis with the stationary arm aligned with the greater trochanter and the moving arm aligned with the lateral malleolus. Using a horizontal bar with the two wooden legs, the intended hip joint is maintained at 90 degrees of flexion and the patient is asked to perform active knee extension with the ankle in the neutral position. This angle is measured by goniometer [11].

Outcome measures such as pain, hamstring length, and ODI score were measured at baseline, at the end of the second and fourth weeks. The data was entered and evaluated by using SPSS-25 software and expressed in a structure of tables and figures. All the individuals were analyzed at baseline and then at the end of 2nd week and 4th week. The Shapiro-Wilk test revealed that the data was non-normally distributed (p<0.05). So, the non-parametric tests were applied including the Mann-Whitney U-test for the group comparison. Friedman’s Test along with Wilcoxon sign Rank test for within-group changes from baseline to end of 4^th week. The level of significance was set at p<0.05.

RESULTS

The mean age of study participants was 33.18±4.380 years. The mean body mass index was 24.650 ± 3.141. Out of n=34 participants, there was only 1(2.9%) participant who was underweight and only n=1(2.9%) participant who was obese=19 (55.9%) participants had normal weight and n=13(38.2%) was overweight. Out of total participants= 8(23.5%) were males and n= 26(76.5%) were females.

Overall Oswestry Disability Index (ODI) scores, Hamstring muscle length (right & left), and pain were significantly improved in both Group A and B from baseline to the fourth week, with large effect sizes (p<0.05) on each assessment. Regarding the ODI domains, in group A sleeping did not significantly improve (p=0.315) from 2^nd week to 4^th week. While in group B sleeping was not significantly improved throughout the intervention. Sitting was not also improve significantly from the 2^nd week to the 4^th week in group B. (Table 1).

Table 1: Within Group  Changes (ODI, Hamstring Muscle Length (Rt & Lt) and Pain (NPRS)

When comparing group A with the group B significant improvement was seen in the hamstring length of the right and left leg as well at the 2nd week and 4th week respectively. When comparing pain and ODI scores between group A and group B no significant difference (p=0.120) was seen from baseline to the fourth week. (Table 2)

Table 2: Between Groups comparison  (ODI, Hamstring Muscle Length (Rt & Lt) and Pain (NPRS)

DISCUSSION

This study aims to find out whether hamstring stretching while maintaining anterior pelvic tilt using pressure biofeedback is more effective than hamstring stretching without using pressure biofeedback on pain, muscle length, and functional status of patients with low back pain. The results of this study showed no significant difference among group A and group B for ODI individual items as well as ODI overall score, it also showed no significant difference in NPRS score from baseline to second week however it showed a significant difference in hamstring muscle length.

Static stretching causes a greater improvement in the flexibility of hamstring muscles than active exercise methods [12]. Static stretching of hamstring muscles improves the viscoelasticity of a muscle which in return promotes increased tolerance to stretching and thus causes an improved flexibility of hamstring muscles [13]. Furthermore, stretching usually decreases the tension in a muscle by improving the length of the musculotendinous unit and there exists an inverse relation between muscle length and muscle tension, the greater the muscle tension lower the muscle length and vice versa so stretching aims to decrease the tension in the muscle and improves the flexibility of muscle [14].

Static stretching in the form of active knee extension position which this study also used as a position for hamstring stretching showed significant improvement in the length of hamstring muscles after using it because evidence has shown that static stretching as compared to other types of stretching may be additional or likewise effective for improving the length of hamstring muscles [15].

The current study showed that there is also an improvement in the NPRS scores with hamstring stretching without using a pressure biofeedback unit in patients with low back pain.  A study suggested that hamstring stretching helps to alleviate low back pain because stretching helps to reduce muscle spasms and improves the flexibility and coordination of muscles and reduction in muscle spasms is one of the contributing factors in the alleviation of lower back pain [13]. Furthermore, the hamstring muscles are the ones that function as a connection between the lower back region and the posterior aspect of the thigh and stretching plays an important role in improving hamstring flexibility and reducing tightness, which in return helps to lower the tension on lower back area and contribute in the alleviation of lower back pain [16, 17].

In the current study,  there is also improvement in the overall Oswestry disability index score as well as individual items including pain intensity, personal care, lifting, walking, sitting, standing, social life, and traveling this might be due to the reason that stretching helps to decrease pain in muscles, enhance flexibility, boost bodily performance as well as avoids injury chances[2, 17, 18]. No improvement in sleeping was noted which may be since sleep might not be affected at baseline, so no improvement was seen after the intervention in patients with chronic low back pain.

The results of this study showed that hamstring stretching using a pressure biofeedback unit in patients with low back pain causes an improvement in the flexibility of the hamstring muscles.  An active knee extension test position for hamstring stretching using a pressure biofeedback unit is more effective for stretching as compared to using the same position without using a pressure bio feedback unit because a pressure biofeedback unit aims to put the pelvis in the anteriorly tilted position[9,18] and evidence has shown that hamstring stretching is more effective in the anterior pelvic tilt position as compared to posterior pelvic tilt position[19]. The focus of this study to use the anterior pelvic tilt position is because hamstring tightness might exist as a potential causative element of low back pain and anterior pelvic rotation might get limited when there is a decrease in the hamstring elasticity [6]. Further evidence has shown that posterior pelvic tilt as well as reduced lumbar lordosis which results from hamstring stiffness is a major cause of low back pain [9, 20]. So, this study uses a pressure biofeedback unit to maintain the anterior pelvic tilt position and restore lumber lordosis. Furthermore, the importance of reestablishing the normal lumber lordosis appears to be helpful in patients with low back pain because the loss of a normal lordotic curve causes an alteration in the mechanical properties of the nervous system [21]. Thus, the use of a pressure biofeedback unit helps to maintain the normal lordotic curve.

This study's results also showed that there is an improvement in the NPRS scores with hamstring stretching using a pressure biofeedback unit in patients with low back pain. The current findings were supported by a study on dentists who had mechanical low back pain. In this study hamstring stretching was performed in the anterior pelvic tilted and significant improvement was observed in pain and disability scores [8].

In the current study, the statistically significant difference implies that pressure biofeedback during stretching improved muscular elongation and relaxation, which may improve results for low back pain patients. Thus, while comprehensive treatment approaches are necessary to manage low back pain, biofeedback integration into hamstring stretching exercises may provide extra advantages by enhancing the length and functionality of the muscular fibers [9].

The Oswestry Disability Index (ODI) individual item and overall score did not significantly change between the groups, indicating that there may have been differences in the study populations, intervention strategies, or outcome measures used. Comparable decreases in pain intensity for both groups throughout the trial are suggested by the lack of a significant difference in Numeric Pain Rating Scale (NPRS) ratings from baseline to the fourth week. In the current study sample size was small, so the results of the non-parametric test may be distorted by their low power as compared to the parametric test.

CONCLUSION

It is concluded that hamstring stretching either by using a pressure biofeedback unit or alone may reduce pain levels and functional ability of patients with low back pain equally. However, using a pressure biofeedback unit in the anterior pelvic tilt position along with hamstring stretching causes a greater improvement in the flexibility of the hamstring muscles. 

DECLARATIONS & STATEMENTS

Author’s Contribution

MR: substantial contributions to the conception and design of the study.

MR and SK: acquisition of data for the study.

MR: analysis of the data for the study.

ZS and KK: interpretation of data for the study.

MR and SK: drafted the work.

MR, SK, ZS and KK: revised it critically for important intellectual content.

MR, SK, ZS and KK: final approval of the version to be published and agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All authors contributed to the article and approved the submitted version.

Ethical Statement

The study was conducted at the physical therapy department of Pakistan Railway Hospital. The ethical approval was obtained from the Research and Ethical Committee (RIPHAH/RCRS/REC/Letter-00854) of Riphah International University, Islamabad Pakistan.

Consent Statement

The written informed consent was obtained from participants as well as from the care givers to participate in the study. 

Data Availability Statement 

The data that support the findings of this study are available on request from the corresponding author. The data is not publicly available due to privacy or ethical restrictions.

Acknowledgments 

None to declare

Conflicts of Interest 

The authors declare no conflict of interest.

Funding

The authors declare that no funds, grants, or other support were received during the conduction of research and preparation of this manuscript.

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