Effect of Hamstring Stretching on Pain at Masseter Muscle and Mouth Opening: A Systematic Review

ABSTRACT

Background

Hamstring flexibility can potentially affect the mobility and function of remote musculoskeletal areas, including the cervical spine and temporomandibular joint (TMJ), thereby increasing tension along the myofascial chain and potentially reducing mouth opening, contributing to orofacial discomfort. This review aims to inform clinical practice by exploring the integrated impact of these interventions within the framework of neuro‐myofascial connectivity.

Methods

A comprehensive search was performed across PubMed, Scopus, Web of Science, and PEDro databases spanning the period from the year 2006–2025, restricted to studies published in the English language. Keywords and MeSH terms corresponding to hamstring stretching, mouth opening and Temporomandibular Joint (TMJ) mobility were used incorporating Boolean operators. Randomized control trials and experimental studies investigating acute or short term effects of hamstring stretching on Temporomandibular Joint (TMJ) pain and mouth opening were included.

Results

The preliminary results indicate that hamstring stretching can result in temporary improvements in pressure pain threshold and mouth opening; however, the results should be interpreted with caution and the number of the RCTs is small and heterogeneous.

Conclusion

The findings support the possibility of myofascial and neural interconnections between the posterior chain and masticatory system; however, the current evidence is insufficient to establish definitive mechanistic conclusions.

Trial Registration

PROSPERO number: CRD420251173297

1. Introduction

Hamstring muscle flexibility is associated with the muscle's ability to lengthen and promote normal joint range of motion, which is essential for efficient movement during both daily and athletic activities. As the hamstrings are susceptible to tightness due to prolonged sitting or muscular imbalance, reduced extensibility is a recurring issue that can cause altered posture and movement patterns (Soylu et al. 2024).

The human body works as a continuous myofascial network where limitations in one region can influence motion and tension in other areas. Fascia, the connective tissue that surrounds and incorporates muscles, plays a vital role in conducting mechanical forces and maintaining structural balance across the body (Jeong et al. 2022).

Temporomandibular disorders (TMD) are a collection of painful conditions influencing the orofacial region, involving the masticatory muscles and temporomandibular Joint (TMJ), usually seen with tinnitus, headache, and neck pain. They affect 25%–40% of people over a lifetime, with muscle disorders being most widely occurring (Akinoğlu et al. 2025). Temporomandibular joint (TMJ) dysfunction commonly coexists with neck pain because of the anatomical and functional connections common to the jaw, neck, and surrounding musculature. Trigger points in the masseter and upper trapezius muscles can limit jaw movement and cervical range of motion while increasing pain and muscle tension (Espejo‐Antúnez et al. 2016; Navarro‐Santana et al. 2020; Kwon et al. 2021). Previous research has indicated that manual therapy and stretching techniques targeting the cervical and shoulder regions can effectively reduce pain and enhance neck mobility (Kosova and Pala 2025; Hyong In and Kang 2013; Bretischwerdt et al. 2010). Earlier studies have interpreted the relationship regarding the temporomandibular joint (TMJ) and the cervical spine. Symptoms in the sternocleidomastoid and masseter muscles were connected to body posture in individuals with myogenic cranio‐cervical mandibular dysfunction (Espejo‐Antúnez et al. 2016).

The myofascial system is functionally and structurally linked; hamstring stretching may affect the cervical and temporomandibular Joint (TMJ) mobility and pain (Akinoğlu et al. 2025). Based on the interdependent nature of the myofascial system, analyzing the influence of hamstring stretching on temporomandibular Joint (TMJ) range of motion and pain may provide valuable insight for integrated rehabilitation strategies. This review, therefore, targets to analyze the effects of hamstring stretching on mouth opening and pain at the masseter muscle, highlighting its clinical implications and identifying potential areas for further research.

2. Methodology

2.1. Protocol

This systematic review was performed according to the PRISMA guidelines. The study was registered under PROSPERO (CRD420251173297).

2.2. Eligibility Criteria

Research Studies were included on the basis of specific inclusion and exclusion criteria. The inclusion criteria include randomized controlled trials published in the English language. Studies having participants of any age and gender diagnosed with tight hamstring and temporomandibular Joint (TMJ) pain and limited mouth opening were regarded as eligible. The exclusion criteria included duplicate studies evaluated from the selection process, unpublished articles, and research designs other than randomized controlled trials. In addition, articles from conference proceedings and PhD theses were excluded from the review. The study was incorporated with PICO study design, P: Participants with tight hamstring, I:Hamstring stretching, C: Either no intervention and self stretching, O: Mouth opening and masseter pain.

2.3. Information Sources

The articles were searched from different search engines, which included PubMed, Scopus, Web of Science, and PEDro.

2.4. Searches

A comprehensive literature search was conducted in accordance with the PRISMA 2020 guidelines across multiple electronic databases to ascertain randomized controlled trial and experimental studies investigating the effects of hamstring stretching on temporomandibular joint (TMJ) range of motion and pain. The electronic databases searched were PubMed, Scopus, Web of Science and PEDro. The database searched retrieved studies published in English between 2006 and 2025. The search strategy incorporated a combination of keywords and Medical Subject Headings (MeSH), using Boolean operators (AND, OR) to obtain a broad and inclusive range of relevant studies. The primary search terms included “hamstring stretching,” “hamstring flexibility,” “hamstring tightness,” “proprioceptive neuromuscular facilitation,” “PNF stretching,” “temporomandibular joint,” “TMJ pain,” “TMJ mobility,” “myofascial connections,” “kinetic chain,” “postural interactions,” and “jaw opening.” A complete reproducible search strategy for each database is provided in the Supporting Information S1.

2.5. Study Selection

Two reviewers independently screened the titles and abstracts to identify potentially eligible articles. Complete manuscripts were then independently reviewed to identify studies that met all the inclusion criteria. Disagreements were resolved by discussion and consensus of all authors.

2.6. Quality Assessment and Risk of Bias

All data were extracted by three individual researchers and entered into a standard data extraction sheet for analysis. Quality assessment of each included trial was done via the PEDro Scale. The PEDro scale scores ranged from 0 to 10, calculated from the total number of criteria met for items, higher scores indicating better methodological quality. RoB2 was also used to assess risk of bias by two individual researchers.

A quantitative synthesis was not feasible due to significant heterogeneity among the included studies in terms of study design, intervention protocols, participant characteristics, outcome measures, and follow‐up duration. Therefore, a systematic approach was considered more appropriate.

3. Result

3.1. Study Selection

The selections of studies are shown in the flowchart (Figure 1). A total of 259 records were initially identified through database searching. After first screening, 109 articles were removed due to duplication. Out of 150, 61 articles were removed on the basis of abstract and title analysis. Among the 89 full‐text articles assessed for eligibility from which 83 studies were excluded for the following reasons: not related to hamstring stretching (n = 25), non‐randomized study design (n = 8), absence of masseter pain outcomes (n = 40), and absence of mouth opening assessment (n = 10). Consequently, six randomized controlled trials met the eligibility criteria and were included in the review.

FIGURE 1.

PRISMA flowchart.

3.2. Study Characteristics

Study characteristics including population, age intervention, treatment procedure, outcome measure and results are discussed in Table 1.

TABLE 1.

Study characteristics.

Study/year	Study design	Participants	Follow‐up period	Outcome measures	Intervention	Control/comparator	Result
1. Fernández‐de‐las‐Peñas et al. (2006)	Randomized controlled trial	N = 50 (31 men and 19 women)	Immediate	Pressure pain threshold (PPT) at the trigger point (TrP)	Hamstring was stretched to its resistance point and held in with an isometric contraction for 5–10 seconds, and then passively stretched further until new resistance is felt, sequence was repeated 3 times	Did not receive any intervention	The treatment group showed significant improvement in PPT and mouth opening, with trigger points improving more than controlled group
				Maximum mouth opening (MMO)
2. Bretischwerdt et al. (2010)	Randomized controlled trial	N = 70 (males), N = 50 (females)	Immediate	Pressure pain threshold (PPT)of masseter and upper trapezius, maximum active mouth opening	Group 1: Unilateral hamstring muscle stretching was applied for 40 s hold, one time	Group 2: Did not receive any intervention	Hamstring stretching increase in PPTs over both masseter and upper trapezius muscles
					Group 3: Bilateral stretching was applied for 40 s hold, one time
3. Rodriguez‐Blanco et al. (2015)	RCT	N = 60	Immediate	—VMO —Masseter muscles pain pressure threshold —Suboccipital range of motion —Lumbar spine mobility	Neuromuscular technique over the masseter muscles (longitudinal myofascial strokes, of about 5–8 cm length, each of 4–6‐s duration) Passive hamstring muscle stretching once with 40 secs hold. Suboccipital muscle inhibition technique	Neuromuscular technique over the masseter muscles (longitudinal myofascial strokes, of about 5–8 cm length, each of 4–6‐s duration) Passive hamstring muscle stretching once with 40 secs hold	In the intragroup comparison, the EG observed an increase in suboccipital flexion and the SAR test. No significant differences were found in the between‐group comparison
4. Espejo‐Antúnez et al. (2016)	Randomized controlled trial	n = 21 (group 1), n = 21 (group 2)	Immediate	Hamstring extensibility, active mouth opening, pressure pain threshold, pain intensity	Group 1‐HR‐PNF stretching: 8 sec isometric contraction + 8 s rest × 3, followed by passive stretch (48 s/leg)	Group 2 ‐HR‐PNF stretching: 8 sec isometric contraction + 8 s rest × 3, followed by passive stretch (48 s/leg). Ischemic compression followed by passive stretch (48 s/leg) along with pressure on masseter trigger point for 90 s post‐stretch	Bilateral hamstring stretching significantly improved extensibility, mouth opening, and PPT, while reducing pain intensity. Adding ischemic compression did not provide extra benefit
				Pressure pain threshold
5. Soylu et al. (2024)	Randomized controlled trial	N = 30	Immediate	Pressure pain threshold hamstring flexibility maximum mouth opening forward head posture	Static stretching: Supine position, hip flexion with extended knee until resistance, 40 s × 3/leg, 15 s rest	Foam rolling: Long sitting position, rolling from ischial tuberosity to knee for 4 min	There were significant improvements in hamstring flexibility and masseter EMG activity, with slight gains in PPT. Mouth opening and posture showed no significant changes, and both interventions were equally effective
6. Irusappan et al. (2025)	RCT	N = 56	1 week	Temporomandibular joint (TMJ) pain	Hamstring stretching: Supine; passive hip flexion held 40 sec × 3 reps, pain‐free stretch. Pressure pain threshold: Applied to central masseter trigger point for 90 seconds, Ultrasound therapy: Frequency: 1 MHz Intensity: 0.8–1 W/cm2 Duration: 5 minutes per session	Control group: Received only pressure pain threshold and ultrasound therapy	Both groups showed significant pain reduction and MVMO improvement, but the experimental group demonstrated greater changes, with significant between‐group differences
				MVMO
				VAS

3.3. Quality Assessment of Included Studies

Quality assessment was done by using the PEDro scoring. A detailed scoring is mentioned in Table 2.

TABLE 2.

PEDro scoring.

Author (year)	Total score	Methodological quality
1. Fernández‐de‐las‐Peñas et al. (2006)	5	Fair
2. Bretischwerdt et al. (2010)	7	Good
3. Rodriguez‐Blanco et al. (2015)	9	Excellent
4. Espejo‐Antúnez et al. (2016)	7	Good
5. Soylu et al. (2024)	8	Good
6. Irusappan et al. (2025)	5	Fair

3.4. Risk of Bias

The risk of bias assessment demonstrated that the majority of the included studies exhibited a low risk of bias across most domains, indicating generally good methodological quality. Studies by Soylu et al., Rodriguez‐Blanco et al., Espejo‐Antúnez et al., and Irusappan et al. showed low risk in all assessed domains. However, Bretischwerdt et al. and Fernández‐de‐las‐Peñas et al. demonstrated some concerns, primarily related to the randomization process and selective reporting. Overall, the findings suggest that the included evidence is methodologically reliable, although a few studies require cautious interpretation due to minor potential sources of bias. Risk of bias was done by using the RoB2. A detailed pictograph is illustrated in Figure 2.

FIGURE 2.

RoB2.

3.5. Summary of Included Studies

A total of six randomized controlled trials (RCTs) analyzing the effects of hamstring stretching on TMJ pain and mouth opening were included in the review. The methodological quality of the studies included was assessed using the PEDro scale. The included studies demonstrated moderate to high methodological quality, with PEDro scores ranging from 5 to 9 (mean = 6.83). Studies with higher PEDro scores and lower risk of bias generally reported more consistent improvements in pressure pain threshold and mouth‐opening outcomes. However, the lack of participant and therapist blinding across several studies may have introduced performance bias, particularly in exercise‐based interventions. Therefore, although the overall findings support the potential benefits of hamstring stretching on temporomandibular Joint (TMJ)‐related outcomes, the strength of evidence should be interpreted cautiously due to methodological limitations and heterogeneity among intervention protocols.

4. Discussion

Overall, the RCTs included in this review showed similarly positive short‐term effects of hamstring stretching on pressure pain threshold and mouth opening. The overall level of evidence has been limited, however, due to methodological differences, relatively small sample sizes, mostly immediate outcome assessments, and differences in intervention protocols.

The principle of myofascial continuity, particularly the superficial back line theory, has been proposed as a possible explanation for the remote effects observed in the included studies. Nevertheless, these mechanisms remain theoretical, and the current clinical evidence does not conclusively establish direct biomechanical or fascial causation between hamstring stretching and temporomandibular Joint (TMJ) improvements. When tension is delivered to one segment (hamstrings), it can be transmitted through the entire chain to distant areas, indicating a credible mechanism for the clinical effects documented in cervical and temporomandibular Joint (TMJ) function following hamstring interventions (Myers 2009; Rodriguez‐Blanco et al. 2015). Nevertheless, these mechanisms remain largely theoretical, and current evidence does not conclusively establish direct causality between hamstring interventions and temporomandibular Joint (TMJ) improvements.

Hamstring stretching substantially increases pressure pain thresholds (PPTs) over the masseter and upper trapezius muscles, indicating an extensive analgesic effect through neural and myofascial connections (Mason et al. 2016). A study reported immediate PPT improvement at both sites following unilateral and bilateral hamstring stretching, suggesting activation of central pain‐modulating mechanisms. The observed effect sizes were moderate to large (0.5–0.7), reflecting clinically significant effects uniform with the hypothesis that lower‐limb flexibility interventions can influence distant pain sensitivity across the musculoskeletal system (Bretischwerdt et al. 2010). While these findings support the concept of remote therapeutic effects, the exact physiological mechanisms remain speculative and require further investigation.

Hamstring stretching, whether static or proprioceptive neuromuscular facilitation (PNF), has been illustrated to produce immediate and consistent improvements in maximum active mouth opening, reflecting enhanced jaw function. Collectively, the included studies demonstrated short‐term improvements in mouth opening, pressure pain threshold, and hamstring extensibility following stretching interventions, although intervention protocols and participant characteristics varied substantially (Cerezo‐Téllez et al. 2016). Together, these outcomes underscore the effect of distal interventions, such as hamstring stretching, on proximal structures like the temporomandibular joint (TMJ), likely influenced by postural and biomechanical interconnections across the myofascial system (Irusappan et al. 2025). These findings suggest that distal interventions may influence proximal structures such as the temporomandibular Joint (TMJ) through biomechanical and postural interconnections; however, stronger evidence is needed before definitive mechanistic conclusions can be drawn.

Physiotherapists should take a comprehensive assessment approach when assessing patients with temporomandibular joint (TMJ) dysfunction (Gallego‐Sendarrubias et al. 2020; Guzmán‐Pavón and Torres‐Costoso 2024). Evaluating hamstring flexibility can provide valuable insights, as limitations in the posterior myofascial chain may contribute to symptoms in these proximal regions through biomechanical and neuromyofascial continuity (Panahi et al. 2014). This reflects a shift from traditional region‐specific evaluations toward a more integrated, system‐based assessment approach (Webb and Rajendran 2016; Merkle et al. 2020). However, based on the current evidence, hamstring stretching should be considered an adjunctive rather than a primary treatment strategy for temporomandibular Joint (TMJ) dysfunction. Clinicians should integrate these interventions within a broader evidence‐based rehabilitation program tailored to individual patient presentations.

The findings should be interpreted taking into account the high degree of heterogeneity of the included studies. There was variation in intervention technique (stretching), length of time, frequency, adjunctive therapy (foam rolling, ischemic compression, ultrasound therapy, and combined manual therapy) and comparator groups (no intervention, foam rolling, ischemic compression, ultrasound therapy, and combined manual therapy). There was also a great variation in outcome measures and follow‐up times, with the majority of studies reporting only short‐term effects. No direct comparison could be made between studies and no meta analysis carried out because of these methodological differences.

The outcomes coincide with prior studies; representing generalized postural re‐education and static stretching to improve pain, mobility, and quality of life in temporomandibular disorders (TMD) cases. Some studies showed no relevant changes, probably related to differences in intervention duration, frequency, or methodological design. Overall, hamstring stretching seems to be a valuable, non‐invasive adjunct therapy for temporomandibular disorders (TMD), promoting pain relief, improved jaw function, and better postural balance. Future studies should use standardized methods and larger sample sizes to assure the long‐term effectiveness and mechanisms of this intervention.

4.1. Limitations

The methodological quality varying from moderate to high of incorporated studies (PEDro scores 5–9, mean 6.83) enhances the credibility of findings. However, various limitations should be taken into account, such as the small number of included RCTs (n = 6) that limits the generalizability of the findings. Only English‐language studies were selected, which may have brought in language bias. Additionally, the short‐term pattern of most interventions limits conclusions about long‐term results. Studies included assorted populations ranging from healthy individuals to those with particular conditions (neck pain, headaches, temporomandibular Joint (TMJ) dysfunction). Though this diversity enhances generalizability, it may also introduce variability in measured outcomes.

4.2. Future Research Directions

Future research should investigate the long term effects of hamstring interventions on cervical and temporomandibular Joint (TMJ) function, determine the most productive stretching factors, investigate underlying fascial mechanisms through advanced imaging, and examine responses across diverse patient populations. In clinical practice, stretching of the hamstrings can be included as an additional rehabilitation measure in a multi‐modal approach to the rehabilitation of people with temporomandibular disorders (TMD). It should not be viewed as the sole management option, and the selection of physiotherapy options for hamstring flexibility should be based on established evidence based physiotherapy options and the hamstring flexibility should be considered as one aspect of the overall assessment and management.

5. Conclusion

The outcomes from this systematic review indicate that hamstring stretching may effectively influence the pressure pain threshold of the masseter muscle and enhance mouth opening. These findings support the possibility of myofascial and neural interconnections between the posterior chain and masticatory system; however, the current evidence is insufficient to establish definitive mechanistic conclusions.

6. Implication to Physiotherapy Practice

Physiotherapists may consider adopting a regional interdependence approach while managing temporomandibular dysfunction. Hamstring flexibility assessment could be incorporated as part of a broader musculoskeletal evaluation because posterior chain tightness may contribute to altered postural and neuromuscular relationships. However, based on the currently available evidence, hamstring stretching should be considered as an adjunctive intervention rather than a standalone treatment for TMJ dysfunction.

Funding

The authors have nothing to report.

Ethics Statement

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Supporting Information S1

Data Availability Statement

The authors have nothing to report.