Immediate Effects of Dry Needling as a Novel Strategy for Hamstring Flexibility: A Single-Blinded Clinical Pilot Study

in Journal of Sport Rehabilitation

Context: There are numerous studies on the benefits of dry needling (DN) for pain relief. No studies exist examining the effects of DN on hamstring flexibility. Objective: To determine the immediate effects of DN on hamstring flexibility in healthy subjects with shortened hamstrings. Design: A single-blinded, pretest–posttest clinical pilot study. Setting: A university physiotherapy clinic. Subjects: A total of 15 healthy subjects (female = 11; age = 23.26 [4.3] y) with shortened hamstrings participated in this study. Intervention: Subjects received a single session of DN. Three locations on the hamstring muscle group were needled, each for 1 minute. Main Outcome Measures: The active knee extension test, muscle compliance, passive peak torque, and stretch tolerance were measured at baseline, immediately, and 15 minutes after DN. Results: There were statistically significant improvements in all outcome measures immediately after DN and at the 15-minute follow-up. The effect sizes for all outcome measures were large (Cohen’s d ≥ 0.8). No serious adverse events were observed with DN. Conclusions: This is the first study that demonstrates the beneficial effects of DN on hamstring flexibility, muscle compliance, and stretch tolerance without added stretching. The beneficial effects of DN should encourage clinicians to use DN as a novel strategy for increasing muscle flexibility.

Flexibility has been defined as the muscle extensibility reflected in the amount of joint range of motion (ROM).1 The maximal muscle length that contributes to the maximal ROM of a joint is essential for activities of daily living and sports performances. Flexibility of the hamstring muscle plays an important role in walking and running.2,3 Hamstring muscles have a high tendency to shorten,4 and limitations in hamstring muscle length are common in general and athletic populations.2 Deficits of hamstring extensibility create muscle imbalances around the knee joint, impair the postural alignment, and can lead to muscle injury.5 A recent study found that decreases in hamstring muscle length are associated with developing low back pain.6 It follows that a priority of physiotherapy or conditioning programs must be improving hamstring muscle length and reducing the risk of injury.

Routinely, physiotherapists use stretching techniques to prevent contractures and increase muscle flexibility.7,8 Although hamstring stretching is regularly included in exercise programs and as an appropriate strategy for the prevention and the treatment of hamstring length deficits, there are contradictory reports on the beneficial effects of stretching in sports9 and limited evidence for hamstring stretching exercises to increase the rate of recovery.10 A Cochrane review concluded that no specific intervention can be recommended for the prevention of hamstring injuries.11 Although various stretching techniques have been shown to increase maximal joint ROM,7,12,13 a recent review suggested that increases in muscle extensibility observed after stretching may not be from changes in the passive mechanical properties of the muscle but from changes in the individuals’ tolerance to stretch or pain.14 A more recent Cochrane Systematic Review of meta-analyses of randomized stretching trials concluded that high-quality evidence does not support the short-term effectiveness of stretching for muscle flexibility and joint mobility in subjects with neurological and nonneurological conditions irrespective of the stretching techniques.15

Dry needling (DN) is a common intervention used by physiotherapists for the treatment of various conditions.1618 DN is a quick, easy to learn, and minimally invasive treatment method targeting soft tissues that involves a thin filiform needle without any injectate into soft tissues for the management of trigger points (TrPs), neuromusculoskeletal pain, fascial adhesions, scar tissue, and movement disorders.19,20 DN has been shown to be effective in the short term for pain alleviation related to TrPs, increase in ROM, and improvement of quality of life.16,21,22 The results of a randomized clinical trial demonstrated that 1 single session of DN significantly decreased the pain intensity and increased active neck ROM in patients with mechanical neck pain.23 Koppenhaver et al24 showed that DN improved functioning of lumbar multifidi and decreased pain, whereas Gerber et al25 observed that DN reduced pain levels for at least 6 weeks following DN in patients with chronic myofascial pain.

Although there are numerous studies demonstrating the benefits of DN in particular for pain relief,19,20,26 no studies exist examining the effects of DN on hamstring flexibility without adding specific stretches. Recently, Mason et al27 conducted a study to explore whether adding DN to a standard stretching program would be more beneficial compared with stretching alone. In their study, 2 sessions of DN did not improve knee ROM in patients with atraumatic knee pain.27 The purpose of this preliminary study was to determine if a single session of DN would improve hamstring flexibility in healthy subjects with shortened hamstrings.

Methods

Study Design

This pilot study, conducted in the physiotherapy clinic of Tehran University of Medical Sciences (TUMS), used a pretest–posttest, and single-blinded design. Three measurements were performed at baseline, immediately after DN, and 15 minutes after the end of the DN. The 15-minute retest was selected to assess the short-term effects of DN required for an athlete’s performance in a single match. The study protocol was approved by the review board of the School of Rehabilitation and the ethical committee of Tehran University of Medical Sciences. All participants gave their written informed consent prior to participation in the study.

Participants

Subjects were students recruited from the School of Rehabilitation, Tehran University of Medical Sciences, in Tehran, Iran. Inclusion criteria were hamstring shortness ≥20° using the active knee extension test (AKET), aged between 18 and 40 years, no history of orthopedic/neurologic disorders in the lower-extremity, no history of low back pain for the last year, no contraindication for using DN (eg, pregnancy, diabetes mellitus), and no joint limitation in the lower-extremities. Exclusion criteria included fear of needling and not consenting to participate in this study.

Sample Size

The software program G*Power 3.1.3 (Universitat Dusseldorf, Germany) was used to perform the power analysis for 1 group with 3 measurements. Considering the statistical test of repeated measures, within factors, an analysis of variance (ANOVA) approach, an alpha of .05, a power of 0.95, and a medium effect size of 0.5, a total sample size of 12 subjects was calculated to detect a significant effect on flexibility as the main outcome measure. Assuming a 10% dropout rate, 15 subjects were recruited for this study.

Outcome Measures

The primary outcome measures in this study were hamstring flexibility measured by the AKET and passive compliance of hamstring muscles. Secondary outcome measures included stretch tolerance and passive peak torque (PPT).

Procedures

The demographic characteristics were recorded including age, weight, and height. An experienced physiotherapist, who was blinded to the treatment given to the subjects, examined the subjects before (T0), immediately after (T1), and 15 minutes after the conclusion of DN (T2). Another experienced physiotherapist qualified in DN performed the DN, being blinded to the results of the baseline measurements.

Measurements

Hamstring Flexibility

The AKET is a reliable and valid tool to measure hamstring muscle length.2830 The dominant leg was assessed in all subjects. Before data collection, the subjects were familiarized with the experimental setup and the test procedure. Subjects were positioned in supine on an examination table with their contralateral lower-extremity secured in extension using a Velcro strap applied across the midthigh. Another Velcro strap was applied over the anterior superior iliac spines to stabilize the pelvis. A custom-made wooden box (width: 38 cm, height: 35 cm, and depth: 30 cm) secured to the examination table with Velcro straps was used to maintain the hip at 90° flexion (Figure 1). A standard goniometer (EZ Read Jamar Goniometer; Performance Health, Warrenville, IL) was used to measure the knee-flexion angle with the stationary arm placed along the lateral thigh from the lateral femoral condyle to the greater trochanter, and the movable arm along the lateral fibula in line with the fibula head and the lateral malleolus. The subject was asked to extend the knee until the first stretch sensation was felt in the back of the thigh area and hold the position to read the goniometric knee-flexion angle (180° indicated full knee extension). Three measurements were taken with a 1-minute rest period between trials, and the average was calculated for data analysis.31

Figure 1
Figure 1

—Active knee extension test with subject in a supine position with the hip maintained at 90° flexion to measure the degrees of active knee extension with a handheld goniometer.

Citation: Journal of Sport Rehabilitation 29, 2; 10.1123/jsr.2018-0013

Stretch Tolerance

The procedure used for the AKET was followed to determine the subjects’ stretch tolerance with the exception that the knee was passively extended to the point of subjects experiencing a strong stretch sensation and pain in the back of the thigh. Subjects stated when the maximal stretch position was reached. The knee-flexion angle at this point was measured with a goniometer as the stretch tolerance angle. An average of 3 measurements with 1-minute rest periods between trials was used for data analysis.

Passive Compliance and PPT

Passive compliance is defined as the ratio of change in angle to the change in passive force.32 A handheld dynamometer (HHD; Micro Manual Muscle Tester; North Coast Medical Inc.) was used to measure the passive torque. To measure the passive compliance, the torques were recorded at 2 angles corresponding to the first stretch sensation and the maximal stretch during passive knee extension following the method used for measuring the subjects’ stretch tolerance. One physiotherapist measured the torque and a second physiotherapist measured the angle using a goniometer. With the subjects in the supine position and the hip flexed at 90°, the physiotherapist placed the HHD against the subjects’ calcaneus bone and passively extended their knee slowly to the first stretch sensation and the maximal stretch, while recording the corresponding torques (in kilogram) and angles.

Passive compliance (Δ angle/Δ torque) was computed taking into account the effect of gravity on the tested leg (W = 6.1% of body weight, L = 28.5% of body height)33 [torque (Nm) = HHD reading (kg) × 9.81 × L (m); gravity force in each angle = HHD reading (kg) × 9.81 × cos α. Again, 3 measurements with 1-minute rest periods between trials were taken, and the average was used for calculating the passive compliance.

Passive Peak Torque

Following the procedure used for measuring hamstring compliance, the maximal resistance to further passive stretch beyond the subjects’ maximal stretch was calculated as the PPT. Again, 3 measurements with 1-minute rest periods between trials were taken, and the average was used for calculating the PPT.

Intrarater Reliability

An intrarater reliability evaluation was conducted in advance for all outcome measures used in this study with 10 healthy participants with shortened hamstring muscles (age = 25.6 [4.6] y). An intraclass correlation coefficient agreement (2-way random effects model, absolute measure, and single rater) was obtained ranging in between .98 and .99.

Dry Needling

An experienced and qualified physiotherapist delivered the non-TrP DN procedure using disposable sterilized stainless steel needles (0.3 × 60 mm; DongBang AcuPrime Ltd, Seoul, Korea). Subjects were positioned prone on a treatment table with their feet over the edge of the table. Hamstring muscles were needled in 3 locations, each for 1 minute, with a fast in–out cone-shaped technique.17,18 Subjects received DN for 1 single session. To standardize the approach and to optimize the application of DN, the points approximately close to the motor point locations for hamstring muscles were needled. Two of the locations were in the long and short head of the biceps femoris at a point at 30% and 60% of a straight line from the ischial tuberosity to the fibular head. For the semitendinosus and semimembranosus muscles, the DN location was selected at a point at 60% of a straight line from the ischial tuberosity to the medial femoral epicondyle (Figure 2).

Figure 2
Figure 2

—Locations along the reference lines for needling of the hamstring muscles. (A) Long head of biceps femoris, (B) Short head of biceps femoris, (C) Semitendinosus and semimembranosus.

Citation: Journal of Sport Rehabilitation 29, 2; 10.1123/jsr.2018-0013

Statistical Analyses

All analyses were performed with SPSS statistical software, (version 18.0; SPSS Inc, Chicago, IL). Descriptive statistics were calculated for participants’ demographic characteristics and all outcome variables as means (SD). The Kolmogorov–Smirnov test showed that all outcome measures were normally distributed. One-way repeated-measures ANOVA was used to investigate the differences in mean values over 3 time points of before, immediately after, and 15 minutes after DN. The Bonferroni test was used for paired comparisons. The sphericity condition was analyzed using the Mauchly’s test statistic to determine the equivalence of variance of differences. If the sphericity condition was not met, the Greenhouse–Geisser test was used to correct the degrees of freedom. The Cohen’s d was used to calculate the effect sizes with values <0.20 as negligible, <0.50 small, <0.80 moderate, and ≥0.80 large. A probability level of P < .05 was considered significant.

Results

Participants

Fifteen healthy subjects (female = 11; age = 23.3 [4.3] y, weight =60.0 [9.2] kg, body height = 166 [8] cm) participated in this study. Participants experienced no serious discomfort and adverse events attributed to the DN except mild pain and muscle soreness.

Table 1 displays the mean values for the pre- and post-DN outcome variables. After DN at T1 and T2, values for all outcome measures increased compared with pre-DN at T0. Values at T2 follow-up were greater than those at T0 and T1. The Mauchly’s test of sphericity showed that the sphericity assumption was met for all outcome measures (P > .05).

Table 1

Mean (SD) (Range) for AKET, Compliance, Peak Torque, and Stretch Tolerance (n = 15)

T0T1T2
AKET, deg136.4 (8.4) (120.7–153.3)148.4 (6.6) (136.7–158.0)151.3 (7.0) (137.7–160.7)
Compliance1.2 (0.5) (0.3–2.5)1.5 (0.5) (0.7–2.5)1.6 (0.5) (0.6–2.6)
Peak torque19.5 (4.0) (13.8–24.2)24.1 (4.6) (15.9–33.6)25.5 (6.9) (17.3–43.3)
Stretch tolerance155.8 (6.4) (143.3–165.0)168.4 (5.7) (156.0–176.0)171.5 (5.3) (160.7–178.0)

Abbreviations: AKET, active knee extension test; DN, dry needling; T0, before DN; T1, immediately after DN; T2, 15 minutes after the end of DN.

AKET

Repeated-measures ANOVA showed significant increases in active knee extension (F2,28 = 130.2, P < .001). Pairwise comparisons using the Bonferroni test indicated significant increases at T1 (8.8%, d = 1.58) and T2 (∼11%, d = 1.93) compared with baseline T0 (P < .001). Active knee extension at T2 follow-up was significantly increased compared with that at T1 after DN (P = .01).

Passive Compliance

Repeated-measures ANOVA showed significant increases in the passive compliance after DN (F2,28 = 11.1, P < .001). Pairwise comparisons using the Bonferroni test indicated no significant increases immediately after DN at T1 (25.0%, d = 0.6) compared with baseline at T0 (P = .06). The passive compliance increased significantly 15 minutes after DN at T2 (33.3%, d = 0.8) compared with baseline at T0 (P < .001). There was no difference of the passive compliance immediately after DN at T1 and 15 minutes after DN at T2 (P = .24).

Passive Peak Torque

Repeated-measures ANOVA showed significant increases in the PPT after DN (F2,28 = 21.1, P < .001). Pairwise comparisons using the Bonferroni test indicated significant increases immediately after DN at T1 (23.6%, P < .001, d = 1.07) and 15 minutes after DN at T2 (30.8%, P = .001, d = 1.06) compared with baseline at T0. There was no significant difference between the peak torque at T1 and T2 (P = .58).

Stretch Tolerance

Repeated-measures ANOVA showed significant increases in the stretch tolerance after DN (F2,28 = 284.92, P < .001). Pairwise comparisons using the Bonferroni test indicated significant increases immediately after DN at T1(∼8%, d = 2.08) and 15 minutes after DN at T2 (∼10%, d = 2.67) compared with baseline at T0 (P < .001). There was a significant difference between the stretch tolerance at T1 and T2 (P = .01).

Discussion

This study demonstrates that hamstrings flexibility improved significantly immediately after 1 session of DN and at a 15-minute follow-up in healthy subjects with shortened hamstrings. No serious adverse events occurred with DN, which supports that DN is a safe option for improving hamstring flexibility. To the authors’ knowledge, this is the first study demonstrating that DN is effective in improving hamstring flexibility. Brady et al34 confirmed earlier that DN of trigger points is a safe procedure.

Active Knee Extension

The AKET was used to assess active knee extension as a measure of hamstrings flexibility. Full knee ROM is required in many sports activities, such as running, football, and kicking, and hamstring flexibility is important for overall athletic performance and injury prevention.35,36 Flexibility exercises are routinely incorporated into physiotherapy protocols. With respect to the AKET, the mean improvement was about 9% directly after DN (↑12°) and 11% at the 15-minute follow-up (↑∼15°). These findings indicate the clinical relevance of improvements in active knee extension achieved with DN considering that a 10% difference is the minimally important difference.37 DN restored the normal range for hamstring muscle length.38,39

Dry needling using a fast in–out technique in a cone shape fashion may target various connective and muscle tissues. One possible explanation for the immediate increases in the range of active knee extension after DN might be that DN increases blood flow and oxygenation,40 which may counteract sustained contractures of muscle shortening. Furthermore, DN may activate the extracellular signal-related kinase and focal adhesion kinase mechanotransduction signaling pathways and involve nicotinamide adenine dinucleotide phosphate oxidase 2, which would also improve the energy metabolism in the muscle and allow the muscle to restore normal length.41

Passive Compliance

Our findings also demonstrated that the hamstring passive compliance significantly increased after DN. The increase in hamstring muscle compliance after a single session of DN of only 3 minutes is interesting and clinically relevant. The changes occurred without any stretching of the muscles and without holding the muscles in a lengthened position for a prolonged period of time.42 Remarkably, we found a 25% increase in muscle compliance directly after the DN intervention, which can be considered a medium effect size. At the 15-minute follow-up point, the muscle compliance had increased to 33%, which would be a large effect size. These findings suggest that DN is effective in improving passive viscoelastic properties of hamstring muscles. The immediate improvement of hamstring compliance after DN was not statistically significant, although it approached the significance level of .06. We speculate that this could be due to the pain and soreness the subjects experienced from the DN. It is also conceivable that the small sample could be a factor. The improvement in hamstring compliance reached statistical significance at the 15-minute follow-up, which may indicate that the effect of DN on hamstring compliance may require some time, possibly because the pain and muscle soreness from the DN had diminished.

The improvement in hamstring compliance may have contributed to the improvements in active knee extension. In other words, the mechanism for improved hamstring flexibility and increases in active knee extension might involve an improved mechanical tissue adaptation rather than a stretch tolerance. It follows that the increases in active knee extension may indicate a change in length of the hamstrings muscle group. In this study, a single session of 3 minutes of DN in total was used with a 15-minute follow-up. Future studies need to determine whether multiple sessions of DN and a longer follow-up period may promote further changes in the flexibility and compliance of the hamstring muscles and whether these changes will remain for a longer period of time.

Limited active knee extension may involve various structures and mechanisms.32 The increases in hamstring compliance might be explained by the improvements in the resting filamentary tension through mechanical manipulation of muscle fibers and connective tissues by DN and a disruption of stable cross-links of myofilaments.32 The immediate improvements in hamstring compliance may suggest a myogenic or fascial mechanism for length adaptation observed in healthy subjects without pathology. Of interest is that Mason et al27 did not find any additional benefit of adding DN to a standard stretching program for young patients with atraumatic anterior knee pain. There were no differences between the DN and sham DN groups, although significant improvements were seen in hamstrings ROM regardless of group allocation.27 Mason et al27 focused on DN of trigger points, while subjects in the sham DN group were “treated” without puncturing the skin.

Passive Peak Torque

Passive peak torque increased after DN and remained for 15 minutes following the DN intervention. We expected a decrease in PPT with improvements in muscle compliance. The observed increases in PPT seemingly contradict the increases in compliance. Subjects participated in this study reported pain and soreness with DN. The pain and soreness, though mild and transient, are common adverse events with DN.43 Consequently, the increase in PPT may be explained by the resistance offered by the subjects due to the DN-related pain and muscle soreness that resulted in the greater torque applied by the assessor. Koppenhaver et al24 found that the pressure pain threshold increased immediately following DN, but decreased after 1 week.

Stretch Tolerance

The stretch tolerance significantly increased after DN. Interestingly, the stretch tolerance not only improved directly after DN, but also improved further at 15-minute follow-up. The greater stretch tolerance is accompanied with reduced stiffness and increased ROM,44 and persons with greater stiffness demonstrated a decrease in PPT.45 In this study, the hamstring flexibility and compliance showed improvements after DN. Thus, it is thought that the enhanced stretch tolerance is due to an increase in range of knee extension with concurrent changes in hamstring muscles compliance observed in this study. These findings indicate that DN increased a person’s tolerance to stretch accompanied with effects on the muscle compliance and flexibility.

Limitations

Some limitations of this study must be acknowledged. First, the sample size was small despite the power analysis. To generalize the findings of this study, a larger cohort of subjects is needed. Second, this study lacked a control or comparison group. Since there are no previous studies on the effects of DN on hamstring flexibility and compliance, this pilot study was conducted to observe whether DN would work. Future studies must include a sham DN group or a group undergoing muscle stretching for comparison. The subjects were not blinded to the type of treatment. Hence, a study with a larger sample of subjects and a control group with a double-blinded design is suggested. Third, the hamstring muscle group flexibility was investigated among a small sample of healthy subjects without pathology. Repeating the study among a cohort of different athletes with shortened hamstrings after an injury involved in different sports may be of interest. Fourth, another limitation of this study is that we investigated the immediate effects of DN with a short follow-up period. Further research is needed to evaluate whether the several treatment with DN enhances the positive outcomes and effects remain for longer time duration.

Conclusions

This study showed for the first time that a single session of DN increased the flexibility of the hamstrings muscles, passive compliance, PPT, and stretch tolerance in healthy subjects with shortened hamstrings. The results are promising and should encourage clinicians to consider DN as a novel strategy for improving muscle flexibility in subjects with muscle shortness.

Acknowledgments

The authors would like to thank the subjects who participated in this study, and the research deputy, Tehran University of Medical Sciences for supporting this research project. All authors declare that they do not have any conflict of interest.

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    Gerber LH, Sikdar S, Aredo JV, et al. Beneficial effects of dry needling for treatment of chronic myofascial pain persist for 6 weeks after treatment completion. PM R. 2017;9(2):105112. PubMed ID: 27297448 doi:10.1016/j.pmrj.2016.06.006

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 26.

    Furlan A, Tulder M, Cherkin D, et al. Acupuncture and dry-needling for low back pain: an updated systematic review within the framework of the Cochrane collaboration. Spine. 2005;30(8): 944963. PubMed ID: 15834340 doi:10.1097/01.brs.0000158941.21571.01

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 27.

    Mason JS, Crowell M, Dolbeer J, et al. The effectiveness of dry needling and stretching vs. stretching alone on hamstring flexibility in patients with knee pain: a randomized controlled trial. Int J Sports Phys Ther. 2016;11(5):672683. PubMed ID: 27757280

    • Search Google Scholar
    • Export Citation
  • 28.

    Neto T, Jacobsohn L, Carita AI, Oliveira R. Reliability of the active-knee extension and straight-leg-raise tests in subjects with flexibility deficits. J Sport Rehabil. 2015;24. PubMed ID: 25364856 doi:10.1123/jsr.2014-0220

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 29.

    Hamid MS, Ali MR, Yusof A. Interrater and intrarater reliability of the active knee extension (AKE) test among healthy adults. J Phys Ther Sci. 2013;25(8):957961. PubMed ID: 24259893 doi:10.1589/jpts.25.957

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 30.

    Cameron DM, Bohannon RW. Relationship between active knee extension and active straight leg raise test measurements. J Orthop Sports Phys Ther. 1993;17(5):257260. PubMed ID: 8343784 doi:10.2519/jospt.1993.17.5.257

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 31.

    Kuilart KE, Woollam M, Barling E, Lucas NP. The active knee extension test and slump test in subjects with perceived hamstring tightness. Int J Osteopathic Med. 2005;8(3):8997. doi:10.1016/j.ijosm.2005.07.004

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 32.

    Gajdosik RL. Passive extensibility of skeletal muscle: review of the literature with clinical implications. Clin Biomech. 2001;16(2):87101. PubMed ID: 11222927 doi:10.1016/S0268-0033(00)00061-9

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 33.

    Guex K, Fourchet F, Loepelt H, Millet GP. Passive knee-extension test to measure hamstring tightness: influence of gravity correction. J Sport Rehabil. 2012;21(3):231234. PubMed ID: 22100435 doi:10.1123/jsr.21.3.231

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 34.

    Brady S, McEvoy J, Dommerholt J, Doody C. Adverse events following dry needling: a prospective survey of chartered physiotherapists. J Man Manip Ther. 2014;22(3):134140. PubMed ID: 25125935 doi:10.1179/2042618613Y.0000000044

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 35.

    Askling CM, Tengvar M, Saartok T, Thorstensson A. Proximal hamstring strains of stretching type in different sports: injury situations, clinical and magnetic resonance imaging characteristics, and return to sport. Am J Sports Med. 2008;36(9):17991804. PubMed ID: 18448581 doi:10.1177/0363546508315892

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 36.

    Croisier JL. Factors associated with recurrent hamstring injuries. Sports Med. 2004;34(10):681695. PubMed ID: 15335244 doi:10.2165/00007256-200434100-00005

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 37.

    de Weijer VC, Gorniak GC, Shamus E. The effect of static stretch and warm-up exercise on hamstring length over the course of 24 hours. J Orthop Sports Phys Ther. 2003;33(12):727733. PubMed ID: 14743986 doi:10.2519/jospt.2003.33.12.727

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 38.

    Youdas JW, Krause DA, Hollman JH, Harmsen WS, Laskowski E. The influence of gender and age on hamstring muscle length in healthy adults. J Orthop Sports Phys Ther. 2005;35(4):246252. PubMed ID: 15901126 doi:10.2519/jospt.2005.35.4.246

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 39.

    Corkery M, Briscoe H, Ciccone N, et al. Establishing normal values for lower extremity muscle length in college-age students. Phys Ther Sport. 2007;8(2):6674. doi:10.1016/j.ptsp.2006.11.004

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 40.

    Cagnie B, Barbe T, De Ridder E, Van Oosterwijck J, Cools A, Danneels L. The influence of dry needling of the trapezius muscle on muscle blood flow and oxygenation. J Manipulative Physiol Ther. 2012;35(9):685691. PubMed ID: 23206963 doi:10.1016/j.jmpt.2012.10.005

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 41.

    Jafri MS. Mechanisms of myofascial pain. Int Sch Res Notices. 2014;2014 . PubMed ID: 25574501

  • 42.

    Magnusson SP, Simonsen EB, Aagaard P, Sørensen H, Kjaer M. A mechanism for altered flexibility in human skeletal muscle. J Physiol. 1996;497(pt 1):291298. PubMed ID: 8951730 doi:10.1113/jphysiol.1996.sp021768

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 43.

    Canadian Agency for Drugs and Technologies in Health. Dry Needling and Injection for Musculoskeletal and Joint Disorders: A Review of the Clinical Effectiveness, Cost-Effectiveness, and Guidelines. Ottawa, Canada: Canadian Agency for Drugs and Technologies in Health; 2016 .

    • Search Google Scholar
    • Export Citation
  • 44.

    Magnusson SP. Passive properties of human skeletal muscle during stretch maneuvers: a review. Scand J Med Sci Sports. 1998;8(2):6577. PubMed ID: 9564710 doi:10.1111/j.1600-0838.1998.tb00171.x

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 45.

    LaRoche DP, Connolly DA. Effects of stretching on passive muscle tension and response to eccentric exercise. Am J Sports Med. 2006;34(6):10001007. PubMed ID: 16476913 doi:10.1177/0363546505284238

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

If the inline PDF is not rendering correctly, you can download the PDF file here.

Ansari, Alaei, Naghdi, Fakhari, and Komesh are with the Department of Physiotherapy, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran. Ansari and Naghdi are also with Sports Medicine Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran; and Neuromusculoskeletal Research Center, Iran University of Medical Sciences, Tehran, Iran. Dommerholt is with Bethesda Physiocare, Bethesda, MD, USA; and Myopain Seminars, Bethesda, MD, USA.

Ansari (nakhostin@sina.tums.ac.ir) is corresponding author.
  • View in gallery

    —Active knee extension test with subject in a supine position with the hip maintained at 90° flexion to measure the degrees of active knee extension with a handheld goniometer.

  • View in gallery

    —Locations along the reference lines for needling of the hamstring muscles. (A) Long head of biceps femoris, (B) Short head of biceps femoris, (C) Semitendinosus and semimembranosus.

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  • 25.

    Gerber LH, Sikdar S, Aredo JV, et al. Beneficial effects of dry needling for treatment of chronic myofascial pain persist for 6 weeks after treatment completion. PM R. 2017;9(2):105112. PubMed ID: 27297448 doi:10.1016/j.pmrj.2016.06.006

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 26.

    Furlan A, Tulder M, Cherkin D, et al. Acupuncture and dry-needling for low back pain: an updated systematic review within the framework of the Cochrane collaboration. Spine. 2005;30(8): 944963. PubMed ID: 15834340 doi:10.1097/01.brs.0000158941.21571.01

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 27.

    Mason JS, Crowell M, Dolbeer J, et al. The effectiveness of dry needling and stretching vs. stretching alone on hamstring flexibility in patients with knee pain: a randomized controlled trial. Int J Sports Phys Ther. 2016;11(5):672683. PubMed ID: 27757280

    • Search Google Scholar
    • Export Citation
  • 28.

    Neto T, Jacobsohn L, Carita AI, Oliveira R. Reliability of the active-knee extension and straight-leg-raise tests in subjects with flexibility deficits. J Sport Rehabil. 2015;24. PubMed ID: 25364856 doi:10.1123/jsr.2014-0220

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 29.

    Hamid MS, Ali MR, Yusof A. Interrater and intrarater reliability of the active knee extension (AKE) test among healthy adults. J Phys Ther Sci. 2013;25(8):957961. PubMed ID: 24259893 doi:10.1589/jpts.25.957

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 30.

    Cameron DM, Bohannon RW. Relationship between active knee extension and active straight leg raise test measurements. J Orthop Sports Phys Ther. 1993;17(5):257260. PubMed ID: 8343784 doi:10.2519/jospt.1993.17.5.257

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 31.

    Kuilart KE, Woollam M, Barling E, Lucas NP. The active knee extension test and slump test in subjects with perceived hamstring tightness. Int J Osteopathic Med. 2005;8(3):8997. doi:10.1016/j.ijosm.2005.07.004

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 32.

    Gajdosik RL. Passive extensibility of skeletal muscle: review of the literature with clinical implications. Clin Biomech. 2001;16(2):87101. PubMed ID: 11222927 doi:10.1016/S0268-0033(00)00061-9

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 33.

    Guex K, Fourchet F, Loepelt H, Millet GP. Passive knee-extension test to measure hamstring tightness: influence of gravity correction. J Sport Rehabil. 2012;21(3):231234. PubMed ID: 22100435 doi:10.1123/jsr.21.3.231

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 34.

    Brady S, McEvoy J, Dommerholt J, Doody C. Adverse events following dry needling: a prospective survey of chartered physiotherapists. J Man Manip Ther. 2014;22(3):134140. PubMed ID: 25125935 doi:10.1179/2042618613Y.0000000044

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 35.

    Askling CM, Tengvar M, Saartok T, Thorstensson A. Proximal hamstring strains of stretching type in different sports: injury situations, clinical and magnetic resonance imaging characteristics, and return to sport. Am J Sports Med. 2008;36(9):17991804. PubMed ID: 18448581 doi:10.1177/0363546508315892

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 36.

    Croisier JL. Factors associated with recurrent hamstring injuries. Sports Med. 2004;34(10):681695. PubMed ID: 15335244 doi:10.2165/00007256-200434100-00005

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 37.

    de Weijer VC, Gorniak GC, Shamus E. The effect of static stretch and warm-up exercise on hamstring length over the course of 24 hours. J Orthop Sports Phys Ther. 2003;33(12):727733. PubMed ID: 14743986 doi:10.2519/jospt.2003.33.12.727

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 38.

    Youdas JW, Krause DA, Hollman JH, Harmsen WS, Laskowski E. The influence of gender and age on hamstring muscle length in healthy adults. J Orthop Sports Phys Ther. 2005;35(4):246252. PubMed ID: 15901126 doi:10.2519/jospt.2005.35.4.246

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 39.

    Corkery M, Briscoe H, Ciccone N, et al. Establishing normal values for lower extremity muscle length in college-age students. Phys Ther Sport. 2007;8(2):6674. doi:10.1016/j.ptsp.2006.11.004

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 40.

    Cagnie B, Barbe T, De Ridder E, Van Oosterwijck J, Cools A, Danneels L. The influence of dry needling of the trapezius muscle on muscle blood flow and oxygenation. J Manipulative Physiol Ther. 2012;35(9):685691. PubMed ID: 23206963 doi:10.1016/j.jmpt.2012.10.005

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 41.

    Jafri MS. Mechanisms of myofascial pain. Int Sch Res Notices. 2014;2014 . PubMed ID: 25574501

  • 42.

    Magnusson SP, Simonsen EB, Aagaard P, Sørensen H, Kjaer M. A mechanism for altered flexibility in human skeletal muscle. J Physiol. 1996;497(pt 1):291298. PubMed ID: 8951730 doi:10.1113/jphysiol.1996.sp021768

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 43.

    Canadian Agency for Drugs and Technologies in Health. Dry Needling and Injection for Musculoskeletal and Joint Disorders: A Review of the Clinical Effectiveness, Cost-Effectiveness, and Guidelines. Ottawa, Canada: Canadian Agency for Drugs and Technologies in Health; 2016 .

    • Search Google Scholar
    • Export Citation
  • 44.

    Magnusson SP. Passive properties of human skeletal muscle during stretch maneuvers: a review. Scand J Med Sci Sports. 1998;8(2):6577. PubMed ID: 9564710 doi:10.1111/j.1600-0838.1998.tb00171.x

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 45.

    LaRoche DP, Connolly DA. Effects of stretching on passive muscle tension and response to eccentric exercise. Am J Sports Med. 2006;34(6):10001007. PubMed ID: 16476913 doi:10.1177/0363546505284238

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
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