Skip to main content
NCBI home page
Galen Medical Journal logoLink to Galen Medical Journal
. 2023 Aug 19;12:e2981. doi: 10.31661/gmj.v12i.2981

Comparison Between the Effects of Transfer Energy Capacitive and Resistive Therapy and Therapeutic Ultrasound on Hamstring Muscle Shortness in Male Athletes: A Single-Blind Randomized Controlled Trial

Haniyeh Choobsaz 1, Nastaran Ghotbi 1,*, Pooria Mohamadi 1
PMCID: PMC11234255  PMID: 38989035

Abstract

Background: Transfer energy capacitive and resistive (TECAR) therapy (TT) is a newly developed deep heating therapy that can generate heat within tissues through high-frequency wave stimulation. Compared to conventional physiotherapy methods, the application of TT especially in sports rehabilitation is becoming more popular. This study aimed to investigate the comparative effect of TT and therapeutic ultrasound (US) on hamstring muscle shortness. Additionally, the effects of TT with static stretching (SS) were compared with US combined with SS.Materials and Methods: Totally, 39 male athletes with hamstring shortness were randomly assigned into three groups: A, B, and C. Group A received 15 minutes of TT plus SS, while Group B received 15 minutes of US with SS, and Group C only performed SS. Hamstring flexibility was measured by active knee extension (AKE), passive knee extension (PKE), and the sit and Reach (SR) tests before the intervention, and following the first, and third treatment sessions.Results: The range of motion of the AKE and PKE, and displacement range in the SR test improved significantly after the first and third sessions in all three groups (P0.0001). The improvement of the three flexibility indices in the TT group was greater than in the other two groups.Conclusion: The present study showed that TT could increase the flexibility of hamstring muscles more than US therapy. However, TT in combination with SS had a similar effect to SS alone.

Keywords: Hamstring Muscle, Physical Therapy Modalities, Static Stretching, Radiofrequency Therapy, Diathermy

Introduction

Muscle flexibility is an important component of normal biomechanical functioning in athletes [1]. Insufficient muscle flexibility may cause musculoskeletal injuries [2]. According to studies, the reduced flexibility of hamstrings influences athletic performance and is a risk factor for developing hamstrings strain [3]. Therefore, the maintenance of the flexibility of hamstrings in athletes is a major issue in physiotherapy.

Various methods are used to improve the muscle flexibility of athletes, including stretching and thermotherapy [4]. Static stretching (SS), due to its low risk of inducing injury, is one of the most effective techniques to improve muscle flexibility [ 5][6]. Thermotherapy is another means of enhancing muscle flexibility, increasing tissue temperature and blood flow and reducing muscle activity [7][8]. Deep heating therapy can be applied through various modalities including ultrasound (US) [ 9], short-wave diathermy [10], and microwaves [11] which have been shown to have different clinical effectiveness.

It is believed that deep heating agents can increase the extensibility of collagen fibers by increasing intramuscular temperature [ 12]. In this way, more significant muscle elongation can be achieved even at lower stretch forces [13]. Low-frequency continuous therapeutic US can penetrate deep tissue layers containing thick muscles to improve muscle flexibility [14][15].

Recently, Transfer Energy Capacitive and Resistive (TECAR) therapy (TT) has been used for clinical purposes as almost a unique physiotherapy modality [16][17][18]. It consists of an electrical current, which induces deep endogenous heating by a 448 kHz capacitive/resistive monopolar radiofrequency [19][20], and can increase the extensibility of soft tissues and muscle flexibility [21][22]. Ribeiro et al. assessed the effectiveness of TT in musculoskeletal disorders. They concluded that this is one of the best modalities of physiotherapy whether used alone or integrated into conventional rehabilitation, with both short-term and long-term benefits. [ 21]. Recently, TT has been introduced to improve hamstring muscle flexibility [23][24]. However, it is unclear whether its effect on muscle elongation is more than the other mentioned methods (i.e., therapeutic US or SS). In our research, no study was found comparing the effects of TT with the therapeutic US on hamstring muscle shortness. Thus, this study aimed to compare the effects of TT and US on the flexibility of hamstrings in healthy athletes with short hamstrings. Furthermore, the effects of US with SS, and TT with SS were compared separately.

Materials and Methods

Study Subjects

A total of 39 non-professional male athletes with hamstring muscle shortness participated in the study [2]. The knee extension range of motion (ROM) of 70 degrees or less in the passive knee extension (PKE) test of the dominant leg was considered hamstring shortness [24]. The exclusion criteria were that the athlete had a history of orthopedic or neurological disorders in the lower limbs within the last six months. In addition, subjects with contraindications to TECAR or US were excluded from the study. The procedure was explained to the participants before obtaining their informed consent. The study was approved by the University’s Ethics Committee (IR.TUMS.FNM.REC.1398.063 ; (IRCT20190920044826N1)). The athletes were randomly assigned into groups of A, B, and C by a simple randomization method (using dice-throwing). One physiotherapist applied the interventions, and another physiotherapist who was unaware of the type of intervention performed the measurements.

Study Assessment

The Sit and Reach (SR) test (Figure-1) as well as active knee extension (AKE) and PKE tests (Figure-2), were used to measure hamstring muscle flexibility [ 25][26] using a Flex Tester Box and an orthopedic goniometer (Maurice E. Mueller Foundation, Bern, Switzerland), respectively. All measurements were carried out three times before the intervention and after the first and third sessions.

Figure-1.

Figure-1

Figure-1. Sit & Reach test to evaluate hamstring muscle flexibility

Open in a new tab

Figure-2.

Figure-2

Figure-2. Athlete's position for the measurement of Active Knee Extension

Open in a new tab

Study Intervention

Interventions included TT, SS, and US therapy administered on a group basis. Participants in each group received treatment three times a week. All interventions were applied in the following manner:

Group A: TT plus SS

The subjects received TECAR therapy (Exon Medical company, TecaTen model IRAN-Class B) in a prone position for 15 minutes at a frequency of 0.5 (MHz). The active electrode (5 cm2) had a continuous circular motion over the posterior surface of the thigh, while the inactive electrode was placed stationary over the quadriceps muscles (170 mm 230 mm). Then, the hamstrings were stretched four times for 30 seconds each. The time interval between stretches was 10 seconds.

Group B: US plus SS

Continuous US (Nutek model Pro UT1041, China) was applied to the hamstrings for 15 minutes while the subjects were in a prone position. US therapy was administered with a power of 2 W/cm2, a frequency of 1 MHz, and a cross-sectional probe area of 5 cm2 with a circular motion speed of 2 cm per second. Subsequently, the hamstrings were stretched four times for 30 seconds each. The period between stretches was 10 seconds.

Group C: SS

Passive stretching was applied in a supine position. The hip was flexed to 90° and the knee was passively and slowly extended [27]. To fix the pelvis, the therapist pushed down against the opposite leg (to prevent posterior pelvic tilt and lumbar flexion). Each stretching technique was performed for 30 seconds and repeated four times. There was a 5-second pause between each stretching technique (Figure-3).

Figure-3.

Figure-3

Figure-3. Summary of groups intervention

Open in a new tab

Statistical Analysis

The obtained data were analyzed using SPSS version 21(SPSS Inc; Chicago, IL, USA). The Kolmogorov-Smirnov test showed normal distribution for all variables (P>0.05). A one-way analysis of variance (ANOVA) was used to examine demographic differences between groups, as well as, determine the differences in flexibility indices (AKE & PKE ROM, and SR displacement) among the groups before treatment.

A two-way ANOVA was used to detect differences between groups and time points. A Tukey Honestly Significant Difference (HSD) post hoc analysis was performed to interpret the findings. Also, Cohen’s d was used to determine the effect size of the groups on hamstring flexibility indices. The level of significance for all tests was set at P<0.05.

Results

A total of 39 athletes participated in the study. The baseline measurements of the participants are presented in Table-1. One-way ANOVA test revealed no significant differences between groups in age, weight, height, and body mass index (BMI). Furthermore, no significant difference was found between the PKE and AKE ROM, and displacement range in the SR test before treatment among the groups (P>0.05). Two-way mixed model ANOVA revealed significant differences in AKE (P=0.001) and PKE (P=0.006) ROM among the three groups. However, the displacements in the SR test were not statistically significant among the groups (P=0.38). The effect of assessment time on hamstring muscle flexibility indices was significant in all three groups (P<0.05). The mean of all test variables after the third session was more than the first and the pre-treatment sessions (P<0.05). The effects of group interaction and assessment time were significant for all three indices (P<0.05) (Table-2). Tukey’s HSD post hoc test showed that in groups A and C, the mean ROM of the AKE and PKE was statistically greater than that of group B (P<0.05). However, there was no difference between groups A and C (P>0.05).

Table1. Demographic Data of Athletes in Three Groups .

Variable Group A (n=13) Mean (SD) Group B (n=13) Mean (SD) Group C (n=13) Mean (SD) P-Value
Age (years) 22.9(2.431) 24.38(2.364) 24.54(3.017) 0.23
Weight (kg) 69.62(4.053) 68.58(7.457) 72.38(4.92) 0.15
Height (cm) 179.54(4.648) 179.15(4.259) 181.54(2.847) 0.27
BMI (kg/m2) 21.592(0.982) 21.538(1.077) 21.938(0.9134) 0.54
Open in a new tab

*BMI: Body Mass Index

Table2. Main Group Interaction and Evaluation Time for Hamstring Muscle Flexibility .

Variables Source Type III Sum of Squares D.F Mean Square F Sig. Partial Eta Squared
SRT Time 66.462 1.190 55.856 14.526 .000 * .287
Time * Group 38.154 2.380 16.033 4.169 .017 * .188
Group 14.923 2 7.462 .971 .388 .051
PKE Time 238.308 1.633 145.936 86.995 .000 * .707
Time * Group 74.410 3.266 22.784 13.582 .000 * .430
Group 143.744 2 71.872 5.882 .006 * .246
AKE Time 291.897 1.729 168.826 72.178 .000 * .667
Time * Group 82.513 3.458 23.862 10.201 .000 * .362
Group 222.205 2 111.103 9.088 .001 * .336
Open in a new tab

SRT: Sit and Reach Test; PKE: Passive Knee Extension; AKE: Active Knee Extension *P<0.05 was significant

Displacement range in the SR test did not show a statistically significant difference among the three treatment groups (P<0.05, Table- 3). Cohen’s d was used to determine the extent of the effect of the different interventions on hamstring flexibility indices in the three groups. Values between 0.2 and 0.5 were interpreted as weak, while values between 0.5 and 0.8, and above 0.80 were considered as medium and strong effect sizes, respectively (Cohen J. Statistical Power Analysis for the Behavioral Sciences; Brydges, 2019 #72). The results showed that the effect size of Group A on changes for the AKE and PKE ROM, and displacement range for the SR test was strong. Group B had a strong effect on ROM changes for AKE and PKE, while it was moderate for the SR test. Group C effect size on the AKE and PKE ROM was strong, but the range of displacement in the SR test showed a moderate effect (Table-4).

Table3. Indices of Hamstring Flexibility (Knee Extension ROM and the Sit and Reach Test) between the Three Treatment Groups .

Variables (I) GROUP (J) GROUP Mean Difference (I-J) Std. Error P Value 95% Confidence Interval
Lower Bound Upper Bound
SRT Group A Group B .23 .628 1.000 -1.35 1.81
Group B Group C -.85 .628 .558 -2.42 .73
Group C Group A .62 .628 1.000 -.96 2.19
PKE Group A Group B 2.26 * .792 .022* .27 4.24
Group B Group C -2.44 * .792 .012* -4.42 -.45
Group C Group A .18 .792 1.000 -1.81 2.17
AKE Group A Group B 2.95 * .792 .002* .96 4.94
Group B Group C -2.90 * .792 .002* -4.89 -.91
Group C Group A -.05 .792 1.000 -2.04 1.94
Open in a new tab

SRT: Sit and Reach Test; PKE: Passive Knee Extension; AKE: Active Knee Extension Group A: TECAR Therapy; Group B: Ultrasound therapy; Group C: Passive stretching *P<0.05 was significant

Table4. Effect Size Values in Muscle Flexibility Indices .

Test Group A Group B Group C
PKE 1.60 1.12 1.44
AKE 3.31 0.65 2.60
SR 1.24 0.53 0.55
Open in a new tab

SR: Sit and Reach; PKE: Passive Knee Extension; AKE: Active Knee Extension

Discussion

This study was primarily conducted to compare the effects of TT and US therapy on hamstring muscle flexibility in male athletes with hamstring muscle shortness. The results showed that TT could improve hamstring flexibility more than US therapy in all measures. One possible explanation may be attributed to the different nature of these modalities. TECAR is a radiofrequency wave that can increase the endogenous temperature in biological structures [18][22]. We used the capacitive energy transfer mode, which affects the tissues that contain more electrolytes, including muscles and soft tissues [28]. On the other hand, the US mechanical acoustic wave is also absorbed by the muscles as protein-rich tissues [29]. However, high-frequency diathermy waves like TECAR can affect a much wider area than the US [30]. In other words, although the cross-sectional area of the TECAR active electrode and US probe were similar, the actual tissue area between both TECAR electrodes (with 17×23 cm inactive electrode size) was greater than that of the US. So, TECAR appears to give more energy to the hamstring muscles [31].

In addition, although US therapy with a frequency of 1 MHz and an intensity of 2 W/cm2 may increase intramuscular temperature, the heat generated under the probe dissipated throughout the tissue because the probe was moving during the treatment time. Therefore, the US could be more efficient in heating smaller areas of the body [ 14][32]. Furthermore, we only had three treatment sessions, and US treatment may not have been sufficient to elicit as much effect as TT (moderate effect size vs. strong effect size, respectively). So, more research with a longer treatment time for larger muscles like hamstrings with more treatment sessions is required to clarify this assumption.

In our study, SS alone improved the flexibility of the hamstring more than the US combined with SS. Nuri et al. [33] showed that SS could increase ankle dorsiflexion ROM more than US therapy (24.18% vs. 4.54%). It seems that stretching alone can increase the extensibility of tissues [34] due to a decrease in the stiffness of the muscle-tendon unit [35][36]. Although it was assumed that the combined effects of US and SS could improve flexibility more than SS alone, this was not the case. It could be due to the large surface area of the treatment, which prevents the local tissue temperature from rising. In addition, in our study, SS was performed after US therapy, additional benefits of US therapy may be seen when used concurrently with US therapy. Similar to our results, Mohammadi et al. did not find a significant difference between TT plus SS and SS alone in terms of improving hamstring flexibility [24].

On the other hand, Kim et al. showed that 15 minutes of TT alone could immediately improve hamstring flexibility [23]. It has been reported that deep heating modalities like the US or short-wave diathermy combined with stretching could have more immediate effects on muscle flexibility than stretching alone [37]. Therefore, it is possible that if we had performed SS simultaneously with either of the two thermal modalities, we could find a greater improvement than SS alone.

The effect size of the AKE ROM was more than PKE in both the TT and SS groups, which could be due to the difference in neurophysiological mechanisms of the two tests [27]. Also, quadriceps muscle strength should be considered, which was not taken into account in our study [6][38]. The change in AKE ROM was almost 7 degrees (6.38°) after three treatment sessions of TT.Concerning the minimal detectable difference in AKE in subjects with a flexibility deficit (7°-8°) [39], it appears that three sessions of TT may be useful for clinical purposes. The SR test between the groups showed no statistical difference. This test has shown high test-retest reliability [40]; however, its results could not only be influenced by the hamstring length but also by factors including the flexibility of the extensor muscles of the spine [41]. As a result, the assessment of the hamstring length may be influenced by the degree of spinal flexion.

To the best of our knowledge, this study was the first single-blind randomized controlled trial comparing the effects of TT and US therapy on the flexibility of hamstring muscles. The present study explored the immediate and short-term effects of the two thermal modalities, providing insight into their potential benefits. In addition, the knee extension ROM tests and the SR test were used concurrently. In this way, it is thought that the flexibility of the hamstring muscle from both ends (proximal and distal attachments) can be assessed. In the present study, the long-term effects of TT and US therapy were not evaluated. Further studies with more treatment sessions and simultaneous application of TECAR or US combined with SS are suggested.

Conclusion

This study showed that three sessions of TT plus SS could improve the length of hamstring muscles more than US therapy combined with SS in male athletes with hamstring shortness. However, based on the SR test the flexibility of hamstrings between the three groups was similar at the end of the interventions.

Acknowledgments

We would like to thank the Research Deputy at the Tehran University of Medical Sciences. We are also grateful to the athletes who participated in this research. This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors.

Conflict of Interest

The authors declare no conflict of interest.

References

  1. Koli BK, Anap DB. Prevalence and severity of hamstring tightness among college student: A cross sectional study . IJCBR. 2018:65–8. [Google Scholar]
  2. Hopper D, Deacon S, Das S, Jain A, Riddell D, Hall T. Dynamic soft tissue mobilization increases hamstring flexibility in healthy male subjects . Br J Sports Med. 2005;9(39):594–8. doi: 10.1136/bjsm.2004.011981. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Shadmehr A, Salemi P, Fereydounnia S. The immediate effect of static hamstring stretching on dynamic balance and gait biomechanical variables in athletes with hamstring tightness: A preliminary study . JMR. 2021;(15):141–50. [Google Scholar]
  4. Nakano J, Yamabayashi C, Scott A, Reid WD. The effect of heat applied with stretch to increase range of motion: a systematic review . Phys Ther Sport. 2012;3(13):180–8. doi: 10.1016/j.ptsp.2011.11.003. [DOI] [PubMed] [Google Scholar]
  5. Herda TJ, Costa PB, Walter AA, Ryan ED, Hoge KM, Kerksick CM. Effects of two modes of static stretching on muscle strength and stiffness . Med Sci Sports Exerc. 2011;9(43):1777–84. doi: 10.1249/MSS.0b013e318215cda9. [DOI] [PubMed] [Google Scholar]
  6. Ichihashi N, Ibuki S, Nakamura M. Effects of static stretching on passive properties of muscle-tendon unit . J Sports Med Phys Fit. 2014;1(3):1–10. [Google Scholar]
  7. Barton CJ, Webster KE, Menz HB. Evaluation of the scope and quality of systematic reviews on nonpharmacological conservative treatment for patellofemoral pain syndrome . J Orthop Sports Phys Ther. 2008;9(38):529–41. doi: 10.2519/jospt.2008.2861. [DOI] [PubMed] [Google Scholar]
  8. Silva LM, Neiva HP, Marques MC, Izquierdo M, Marinho DA. Effects of warm-up, post-warm-up, and re-warm-up strategies on explosive efforts in team sports: A systematic review . Sports Med. 2018;10(48):2285–99. doi: 10.1007/s40279-018-0958-5. [DOI] [PubMed] [Google Scholar]
  9. Garrett CL, Draper DO, Knight KL. Heat distribution in the lower leg from pulsed short-wave diathermy and ultrasound treatments . J Athl Train. 2000;1(35):50–5. [PMC free article] [PubMed] [Google Scholar]
  10. Giombini A, Di Cesare, Casciello G, Sorrenti D, Dragoni S, Gabriele P. Hyperthermia at 434 MHz in the treatment of overuse sport tendinopathies: a randomized controlled clinical trial . Int J Sports Med. 2002;03(23):207–11. doi: 10.1055/s-2002-23180. [DOI] [PubMed] [Google Scholar]
  11. Rabini A, Piazzini DB, Tancredi G, Foti C, Milano G, Ronconi G. Deep heating therapy via microwave diathermy relieves pain and improves physical function in patients with knee osteoarthritis: a double-blind randomized clinical trial . Eur J Phys Rehabil Med. 2012;4(48):549–59. [PubMed] [Google Scholar]
  12. Bito T, Tashiro Y, Suzuki Y, Kajiwara Y, Zeidan H, Kawagoe M. Acute effects of capacitive and resistive electric transfer (CRet) on the Achilles tendon . Electromagn Biol Med. 2019;1(38):48–54. doi: 10.1080/15368378.2019.1567525. [DOI] [PubMed] [Google Scholar]
  13. Lounsberry NL. Therapeutic heat: effects of superficial and deep heating modalities on hamstring flexibility . Osprey Journal of Ideas and Inquiry. 2008;(7):138–138. [Google Scholar]
  14. Miller DL, Smith NB, Bailey MR, Czarnota GJ, Hynynen K, Makin IR. Overview of therapeutic ultrasound applications and safety considerations . J Ultrasound Med. 2012;4(31):623–34. doi: 10.7863/jum.2012.31.4.623. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Rose S, Draper DO, Schulthies SS, Durrant E. The stretching window part two: Rate of thermal decay in Deep Muscle Following 1-MHz Ultrasound . J Athl Train. 1996;2(31):139–43. [PMC free article] [PubMed] [Google Scholar]
  16. Beltrame R, Ronconi G, Ferrara PE, Salgovic L, Vercelli S, Solaro C. Capacitive and resistive electric transfer therapy in rehabilitation: a systematic review . Int J Rehabil Res. 2020;4(43):291–8. doi: 10.1097/MRR.0000000000000435. [DOI] [PubMed] [Google Scholar]
  17. Kumaran B, Watson T. Thermal build-up, decay and retention responses to local therapeutic application of 448 kHz capacitive resistive monopolar radiofrequency: A prospective randomized crossover study in healthy adults Int . J Hyperth. 2015;8(31):883–95. doi: 10.3109/02656736.2015.1092172. [DOI] [PubMed] [Google Scholar]
  18. Vahdatpour B, Haghighat S, Sadri L, Taghian M, Sadri S. Effects of transfer energy capacitive and resistive on musculoskeletal pain: A Systematic Review and Meta-Analysis . GMJ. 2022;(11):e2407–e2407. doi: 10.31661/gmj.v11i.2407. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Oh D-G, Kim S-K, Yoo K-T. Effect of Physiotherapeutic Intervention using TECAR therapy on pain self-awareness and hip joint function in hip impingement syndrome: A Case Study . KSPM. 2021;3(16):45–53. [Google Scholar]
  20. Osti R, Pari C, Salvatori G, Massari L. Tri-length laser therapy associated to tecar therapy in the treatment of low-back pain in adults: a preliminary report of a prospective case series . Lasers Med Sci. 2015;1(30):407–12. doi: 10.1007/s10103-014-1684-3. [DOI] [PubMed] [Google Scholar]
  21. Ribeiro S, Henriques B, Cardoso R. The effectiveness of tecar therapy in musculoskeletal disorders . Int J Public Health. 2018;5(3):77–83. [Google Scholar]
  22. Yeste-Fabregat M, Baraja-Vegas L, Vicente-Mampel J, Pérez-Bermejo M, Bautista González, Barrios C. Acute effects of tecar therapy on skin temperature, ankle mobility and hyperalgesia in myofascial pain syndrome in professional basketball players A Pilot Study . Int J Environ Res Public. 2021;16(18):8756–8756. doi: 10.3390/ijerph18168756. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Kim YJ, Park J-H, Kim J-h, Moon GA, Jeon H-S. Effect of High-frequency Diathermy on Hamstring Tightness . Phys Ther Korea. 2021;1(28):65–71. [Google Scholar]
  24. Mohamadi P, Ghotbi N, Bashardoust S, Naghdi Dorbati, Salehi S. Comparison of the Effect of TECAR Therapy and Static Stretching on Hamstring Flexibility in Male Athletes . Babol-Jbums. 2021;1(23):53–9. [Google Scholar]
  25. Minkler S, Patterson P. The validity of the modified sit-and-reach test in college-age students . Res Q Exerc Sport. 1994;2(65):189–92. doi: 10.1080/02701367.1994.10607614. [DOI] [PubMed] [Google Scholar]
  26. Reurink G, Goudswaard GJ, Oomen HG, Moen MH, Tol JL, Verhaar JA. Reliability of the active and passive knee extension test in acute hamstring injuries . Am J Sports Med. 2013;8(41):1757–61. doi: 10.1177/0363546513490650. [DOI] [PubMed] [Google Scholar]
  27. Nakao G, Taniguchi K, Katayose M. Acute effect of active and passive static stretching on elastic modulus of the hamstrings . Sports Med Int Open. 2018;06(2):E163–E70. doi: 10.1055/a-0733-6957. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Rodríguez-Sanz J, López-de-Celis C, Hidalgo-García C, Canet-Vintró M, Fanlo-Mazas P, Pérez-Bellmunt A. Temperature and current flow effects of different electrode placement in shoulder capacitive-resistive electric transfer applications: a cadaveric study . BMC Musculoskelet Disord. 2021;1(22):139–139. doi: 10.1186/s12891-020-03918-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Quarato CMI, Lacedonia D, Salvemini M, Tuccari G, Mastrodonato G, Villani R. A Review on Biological Effects of Ultrasounds: Key Messages for Clinicians . Diagnostics. 2023;5(13):855–855. doi: 10.3390/diagnostics13050855. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Garrett CL, Draper DO, Knight KL. Heat distribution in the lower leg from pulsed short-wave diathermy and ultrasound treatments . J Athl Train. 2000;1(35):50–50. [PMC free article] [PubMed] [Google Scholar]
  31. Clijsen R, Leoni D, Schneebeli A, Cescon C, Soldini E, Li L. Does the application of Tecar therapy affect temperature and perfusion of skin and muscle microcirculation A pilot feasibility study on healthy subjects . J Altern Complement Med. 2020;2(26):147–53. doi: 10.1089/acm.2019.0165. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Sellani G, Fernandes D, Nahari A, de Oliveira, Valois C, Pereira WC. Assessing heating distribution by therapeutic ultrasound on bone phantoms and in vitro human samples using infrared thermography . J Ther Ultrasound. 2016;(4):13–13. doi: 10.1186/s40349-016-0058-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Nuri L, Ghotbi N, Faghihzadeh S. Acute effects of static stretching, active warm up, or passive warm up on flexibility of the plantar flexor muscles of Iranian professional female Taekwondo Athletes . J Musculoskelet Pain. 2013;3(21):263–8. [Google Scholar]
  34. Gajdosik RL. Passive extensibility of skeletal muscle: review of the literature with clinical implications . Clin Biomech (Bristol, Avon) 2001;2(16):87–101. doi: 10.1016/s0268-0033(00)00061-9. [DOI] [PubMed] [Google Scholar]
  35. Konrad A, Tilp M. The time course of muscle-tendon unit function and structure following three minutes of static stretching . J Sports Sci Med. 2020;1(19):52–8. [PMC free article] [PubMed] [Google Scholar]
  36. Takeuchi K, Akizuki K, Nakamura M. Time course of changes in the range of motion and muscle-tendon unit stiffness of the hamstrings after two different intensities of static stretching . PLoS One. 2021;9(16):e0257367–e0257367. doi: 10.1371/journal.pone.0257367. [DOI] [PMC free article] [PubMed] [Google Scholar]
  37. Peres SE, Draper DO, Knight KL, Ricard MD. Pulsed shortwave diathermy and prolonged long-duration stretching increase dorsiflexion range of motion more than identical stretching without diathermy . J Athl Train. 2002;1(37):43–50. [PMC free article] [PubMed] [Google Scholar]
  38. Herda TJ, Herda ND, Costa PB, Walter-Herda AA, Valdez AM, Cramer JT. The effects of dynamic stretching on the passive properties of the muscle-tendon unit . J Sports Sci. 2013;5(31):479–87. doi: 10.1080/02640414.2012.736632. [DOI] [PubMed] [Google Scholar]
  39. 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;4(24):1–1. doi: 10.1123/jsr.2014-0220. [DOI] [PubMed] [Google Scholar]
  40. Baltaci G, Un N, Tunay V, Besler A, Gerçeker S. Comparison of three different sit and reach tests for measurement of hamstring flexibility in female university students . Br J Sports Med. 2003;1(37):59–61. doi: 10.1136/bjsm.37.1.59. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. akınoğlu B, Paköz B, Hasanoğlu A, Kocahan T. Investigation of the relationship between sit-and-reach flexibility and the height, the leg length and the trunk length in adolescent athletes . Balt J Health Phys Act. 2021;(13):29–37. [Google Scholar]

Articles from Galen Medical Journal are provided here courtesy of SalviaPub

RESOURCES