Hamstring Strain

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Definition/Description

Hamstring strains are caused by a rapid extensive contraction or a violent stretch of the hamstring muscle group which causes a high mechanical stress. This results in varying degrees of rupture within the fibres of the musculotendinous unit.
Hamstring strains are common in sports with a dynamic character like sprinting, jumping, etc.,... where quick eccentric contractions are regular. In soccer it is the most frequent injury. 
The hamstrings consist of three muscles : The biceps femoris, the semitendinosus and the semimembranosus.

Clinically Relevant Anatomy

The hamstrings are a group of muscles which are comprised of three separate muscles located at the back of the thigh. The M. Biceps Femoris, M. Semitendinosus and the M. Semimembranosus. These muscles start at the ischial tuberosity, extending down the back of the thigh and along either side of the knee .

The M. Biceps Femoris exists out of two parts: the long head and the short head (Caput longum and Caput breve). These two parts are both attached to the head of the fibulae, but only the long head starts at the ischial tuberosity. The other part, the short head, starts at the lateral lip of the linea Aspera on the posterior aspect of the femur . The Caput Breve and Longum are innervated by 2 different nerves. The Caput Longum is innervated by the N. Tibialis, while the Caput Breve is innervated by the N. Fibularis, who are both originating from the spine segment L5-S2 .

The M. Semitendinosus starts at the ischial tuberosity but unlike the M. Biceps Femoris, it lays at the medial side of the thigh and is attached to the upper medial surface of the tibia, also called Pes Anserinus.

The M. Semimembranosus is the most medial of the three hamstring muscles . It also starts at the ischial tuberosity and is attached to the Condylus Medialis Tibiae . It’s also connected to the Lig. Popliteum Obliquum, and the fascia cruris .
  
This shows that all of the three hamstring muscles start at the same origin, but have different insertions .
Schematic Review of structural anatomy

- M. Biceps Femoris:
              o Caput Breve:
                      § O: Labium Laterale Lineae Aspera, Septum Intermusculare Laterale
                      § I: Caput Fibula

              o Caput Longum:
                      § O: Tuber Ishiadicum
                  § I: Caput fibula

- M. Semimtendinosus:
              o O: Tuber ishidadicum
              o I: Pes Anserinus (facies Medialis Tibiae)

- M. Semimembranosus:
             o O: Tuber Ishiadicum
             o I: Condylus Medialis Tibiae, Lig. Popliteum Obliquum, Fascia Cruris

Because the hamstrings cross 2 joints (the knee and the hip), their functions are varied.
The muscles function as movers and stabilizers of the hip and knee. The hamstrings are used to flex the knee, and extent the hip. The hamstrings help to get from a crouched position to an erect position. This refers to movements like getting up from a chair or in sprinting, where the front leg in starting position has to bear the effect or the start .

Because of the insertion of the muscles, the secondary function of the hamstrings is endo and exorotation of the knee. This makes the hamstrings extremely important muscles if it comes to walking and running .

Schematic review of functional anatomy:

- M. Biceps Femoris:
           o Extension Hip
           o Flexion Knee
           o Exorotation Bottom Leg

- M. Semitendinosus:
           o Extension Hip
           o Flexion Knee
           o Endorotation Bottom Leg

- M. Semimebranosus:
           o Extension Hip
           o Flexion Knee
           o Endorotation Bottom Leg

Epidemiology /Etiology

The cause of a hamstring muscle strain is often obscure. In the late forward swing phase, the hamstrings are at their greatest length and at this moment, they generate maximum tension . In this phase, hamstrings contract eccentrically to decelerate flexion of the hip and extension of the lower leg . At this point, a peak is reached in the activity of the muscle spindles in the hamstrings. A strong contraction of the hamstring and relaxation of the quadriceps is needed. According to “Klafs and Arnheim”, a breakdown in the coordination between these opposite muscles can be a cause for the hamstring to tear.

Predisposing Factors/Risk Factors

There are several predisposing factors to hamstring strains like fatigue, poor posture (anterior tilt of the pelvis), muscle strength imbalances, leg length inequality, non-flexibility and an insufficient warm-up . So reported Worrel et al. that the hamstring-injured group was significantly less flexible than the non-injured group. These factors have an influence on the tenderness of the hamstrings.
During activities like running and kicking, hamstring will lengthen with concurrent hip flexion and knee extension, this lengthening may reach the mechanical limits of the muscle or lead to accumulation of microscopic muscle damage. There is a possibility that hamstring injuries may arise secondary to the potential uncoordinated contraction of biceps femoris muscle resulting from dual nerve supply. Another debate is on hamstring variation in muscle architecture. BFS possess longer fascicles (which allow for greater muscle extensibility and reduce the risk of over lengthening during eccentric contraction) and a much smaller CSA compared to BFL. Whereas BFL presents with shorter fascicles compared to BFS which undergo repetitive over lengthening and accumulated muscle damage. Excessive anterior pelvic tilt will place the hamstring muscle group at longer lengths and some studies proposed that this may increase risk of strain injury.
There are various proposed risk factors which may play a role in hamstring injuries. Increased age, previous hamstring injury, limited hamstring flexibility, increased fatigue, poor core stability and strength imbalance have been listed as possible risk factors for hamstring strain injuries.

= Characteristics/Clinical Presentation  =

Hamstring strain results in a sudden sharp pain in the posterior thigh when it occurs during sport activities. Also a "popping" or tearing impression can be described. The patients may complain of tightness and improved range of motion like knee extension and hip flexion. Sometimes swelling and ecchymosis are possible but they may be delayed for several days after the injury occurs. Rarely symptoms are numbness, tingling and distal extremity weakness. These symptoms require a further investigation into sciatic nerve irritation. Large hematoma or scar tissue can be caused by complete tears and avulsion injuries.
Other possible symptoms:
· Pain
· Tenderness
· Loss of motion
· Decreased strength on isometric contraction
· Decreased length of the hamstrings

Hamstring strains are categorised in 3 groups, according to their severity.:

· Grade 1 (mild): just a few fibres of the muscle are damaged or have ruptured. This rarely influences the muscle's power and endurance. Pain and sensitivity usually happen the day after the injury (depends from person to person). Normal patient complains are stiffness on the back side of the leg. Patients can walk fine. There can be a small swelling, but the knee can still bend normally.

· Grade 2 (medium): approximately half of the fibres are torn. Symptoms are acute pain, swelling and a mild case of function loss. The walk of the patient will be influenced. Pain can be reproduced by applying precision on the hamstring muscle or bending the knee against resistance.

· Grade 3 (severe): ranging from more than half of the fibres ruptured to complete rupture of the muscle. Both the muscle belly and the tendon can suffer from this injury. It causes massive swelling and pain. The function of the hamstring muscle can't be performed anymore and the muscle shows great weakness.

Differential Diagnosis

On examining the patient, the physiotherapist possibly has to differentiate between different injuries e.g. adductor strains, avulsion injury, lumbosacral referred pain syndrome, piriformis syndrome, sacroiliac dysfunction, sciatica, Hamstring tendinitis and ischial bursitis. 
Other sources of posterior thigh pain could also be confused with hamstring strains and should be considered during the examination process. Specific tests and imaging are used to asses and exclude those different pain source possibilities.
Sciatic nerve mobility limitations can contribute to posterior thigh pain and adverse neural tension could in some cases be the only source of pain without any particular muscular injury. In certain cases it is difficult to determinate whether it are the Hamstrings or other muscle groups like hip adductors (eg. M. Gracilis and M. Adductour magnus and longus.) that are injured due to their proximity. Sometimes imaging procedures may be required to determinate the exact location of the injury.

Other conditions with similar presentations as hamstring strains are strained popliteus muscle, tendonitis at either origin of the gastocnemius, sprained posterior cruciate ligament, apophysitis-pain in ischial tuberosity, Lumbar spine disorders and lesions of the upper tibio-fibular joint.

Diagnostic Procedures

Most of the acute injuries can easily be found by letting the patient tell how the injury occured. To be sure they must do a little investigation of the hamstrings as well.

When the therapist Isn't too sure, he can ask for medical imaging. This will exclude al other possibilities.

- Radiographs: a good thing about radiographs is that with that kind of imaging, its possible to differentiate the etiology of the pain. It can differentiate in muscular disease (e.g muscle strain) or a disease of the bone (e.g. Stress fracture).

- Ultrasound (US): this kind of imaging is used a lot because it is a cheap method. It is also a good method because it has the ability to image muscles dynamically. A negative point about Ultrasound is that it needs a skilled and experienced clinician.

- Magnetic Resonance Imaging (MRI): MRI gives a detailed view of the muscle injury. But sometimes it may not be clear according to the images. If that happens, the therapist must rely on the story that the patient told him (see characteristics/clinical presentation).

Outcome Measures

• FASH: The FASH questionnaire is a self-administered questionnaire which now can only be used in Greek, English and German languages. Because hamstring injuries represent the most common football injury, they tested the validity and reliability of the FASH-G (G = German version) questionnaire in German-speaking footballers suffering from acute hamstring injuries.

The FASH-G questionnaire was tested on 16 footballers with hamstring injuries (patients’ group) , 19 field hockey players (at risk-group) and a healthy group: 77 asymptomatic footballers. For measuring the validity of the test they compared the total FASH-G score of the non-injured and injured groups. Reliability of the FASH-G questionnaire was analysed in 18 asymptomatic footballers using the intra-class coefficient.
The FASH (Functional Assessment Scale for Acute Hamstring Injuries) questionnaire:
· They came to the result there were significant differences between injured and non-injured participants.
· No statistical differences were found between healthy athletes (p = 0.257), but patients’ groups (footballers with hamstring injuries) and at-risk groups (hockey players) presented scoring differences(p = 0.040 and <0.001, respectively).
So we can conclude that the FASH-G is a valid and reliable instrument to assess and determine the severity of hamstring injuries, in this case tested on German footballers.

• LEFS: Lower Extremity Functional Scale "http://www.physio-pedia.com/Lower_Extremity_Functional_Scale_(LEFS)"

• SFMA: The Selective Functional Movement Assessment (SFMA) is a clinical assessment system designed to identify musculoskeletal dysfunction by evaluation of fundamental movements for limitations or symptom provocation.

• PSFS: Patient Specific Functional Scale <a href="http://www.physio-pedia.com/Patient_Specific_Functional_Scale"

• VAS: Visual Analog Scale "http://www.physio-pedia.com/Visual_Analogue_Scale">

• NPRS: Numerical Pain Rating Scale "http://www.physio-pedia.com/Numeric_Pain_Rating_Scale"

Examination

The physical examination begins with an examination of the running gait. Patients with a hamstring strain usually show a shortened walking gait. Swelling and ecchymosis aren’t always detectable at the initial stage of the injury because they often appear several days after the initial injury <span class="fck_mw_ref" _fck_mw_customtag="true" _fck_mw_tagname="ref" name="Frontera et al." />. The physical examination also exists of visible examination. The posterior thigh is inspected for asymmetry, swelling, ecchymosis and deformity. When there is a palpable defect, it indicates a more severe injury, mostly with a full rupture of the muscle. Also the active and passive range of motion should be tested and compared with the other leg.

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Clinical tests

1. Puranen-Orava test – Actively stretching the hamstring muscles in standing position with hip flexed at about 90*, the knee fully extended and foot on a solid surface. Positive – exacerbation of symptoms. (SN 0.76, SP 0.82, +LR 4.2, -LR 0.29)

2. Bent-Knee stretch test (SN 0.84, SP 0.87, +LR 6.5, -LR 0.18)

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3. Modified Bent-knee stretch test (SN 0.89 SP 0.91, +LR 9.9, -LR 0.12)
4. Taking off the shoe test/hamstring-drag test (SN 1.00, SP 1.00, +LR 280.0, -LR 0.00)
5. Active ROM test (SN 0.55, SP 1.00, +LR 154.6, -LR 0.50)
6. Passive ROM test (SN 0.57, SP 1.00, +LR 160.6, -LR 0.43)
7. Resisted ROM test (SN 0.61, SP 1.00, +LR 170.6, -LR 0.40)

Tests Summery

Test	Sensitivity	Specificity	+LR	-LR
Puranen-Orava	0.76	0.82	4.2	0.29
Bent-Knee stretch	0.84	0.87	6.5	0.18
Modified Bent-knee stretch	0.89	0.91	9.9	0.12
Taking off the shoe	1.00	1.00	280	0.00
Active ROM	0.55	1.00	154.6	0.50
Passive ROM	0.57	1.00	160.6	0.43
Resisted ROM	0.61	1.00	170.6	0.40

Medical Management

Surgical intervention is an extremely rare procedure after a hamstring strain. Only in case of a complete rupture of the hamstrings, surgery is recommended. Almost all patients believed that they had improved with surgery. A study  shows that 91% was satisfied after surgery and rated their happiness with 75% or better. Hamstrings endurance tests and hamstring strength tests were better and highly scored after an surgical procedure. The muscle strength testing after surgery ranged from 45% until 88%. The hamstrings endurance testing ranged from 26% to 100% .The physical examination and follow-up reveals that all repairs stayed intact.

Physical Therapy Management

The primary objective of physical therapy and the rehabilitation program is to restore the patient’s functions to the highest possible degree and/or to return the athlete to sport at the former level of performance and this with minimal risk of reinjury.
Hamstring strain injuries remain a challenge for both athletes and clinicians, given their high incidence rate, slow healing, and persistent symptoms. Moreover, nearly one third of these injuries recur within the first year following a return to sport, with subsequent injuries often being more severe than the original. The use of a specific and adequate training programme to rehabilitate hamstring strains can be determinant for the healing and prevention of a recurrent hamstrings strain injury. Different kind of therapies are used to rehabilitate hamstring strains, but are they all as effective enough to prevent a recur within the first year following a return to sport? Different studies tried to show the impact of eccentric exercises, dry needling, deep stripping massage, etc. on hamstring strain rehabilitation.
The use of eccentric strengthening at long muscle lengths exercises as rehabilitation where used to examine the effects to prevent a recurrence hamstring injury following the revalidation. The results shown that the use of eccentric strengthening exercises at long muscle had a positif effect. Fifty sporters with a hamstring strain injury were examined. Eight of the 50 athletes did not complete the rehabilitation. Four of them sustained reinjuries between 3 and 12 months after return to sport. The other 42 athletes had not sustained a reinjury at an average of 24±12 months after return to sport. Compliance with rehabilitation emphasizing eccentric strengthening with the hamstrings in a lengthened position resulted.

On the other hand, a study tried to compare eccentric strengthening exercises (STST) with progressive agility and trunk stabilization exercises (PATS). The rehabilitation of the STST group consisted of static stretching, isolated progressive hamstring resistance exercise, and icing. The PATS group consisted of progressive agility and trunk stabilization exercises and icing as treatment. The study found a significant better result in patients that were rehabilitated with progressive agility and trunk stabilization. Reinjury rate was significantly lower in the PATS group after one year returning to sport (1 of the 13 athletes instead of 7 on the 11 athletes in the STST group). A rehabilitation program consisting of progressive agility and trunk stabilization exercises is more effective than a program emphasizing isolated hamstring stretching and strengthening in promoting return to sports and preventing injury recurrence in athletes suffering an acute hamstring strain.
Deep stripping massage is another technique used as rehabilitation for hamstring strain injury. Most of the time it is combined with other rehabilitation technique. Deep stripping massage (DSMS) alone or with eccentric resistance where used to examine the impact on hamstring length and strength. These results suggest that DSMS increases hamstring length in less than 3 min but has no effect on strength. Furthermore, combining DSMS with eccentric resistance produces more hamstring flexibility gains than DSMS alone and does not affect strength.

Functional dry needling is a technique that has been reported to be beneficial in the management of pain and dysfunction after muscle strains and in combination with eccentric training program, but there is limited published literature on its effects on rehabilitation or recurrence of injury.

The impact of kinesiology tape has been demonstrated to be efficient on the improving of muscle flexibility, which can prevent or improve the risk of having injuries. The effectiveness of stretching techniques and kinesiology tape on hamstring extensibility were compared. Thirty male participated to the study. The patients had to perform an active knee extension assessment (of the dominant leg) to measure the hamstring extensibility. Three experimental interventions were applied in randomized order: Kinesiology tape (KT), static stretch (SS), proprioceptive neuromuscular facilitation (PNF). Measures were taken at baseline, +1min, + 30mins, + 3days and +5days days after each intervention. Each intervention displayed a unique temporal pattern of changes in active knee extension. SS was best suited to immediate improvements, and PNF to +30 minutes in hamstring extensibility, whereas kinesiology tape offered advantages over a longer duration, peaking at 2.76 days.

Kinesiology tape can be used in combination of other rehabilitation programmes to improve the muscle flexibility.
There are lots of techniques and programmes that can be used for the revalidation of hamstring strains injuries but due to a lack of studies, the effectiveness of these techniques can not all been demonstrated. Therefore eccentric exercises are the most known and applied programme for the rehabilitation of hamstring strains injuries. The use of this kind of programme has shown good results. One common criticism of rehabilitation programs that emphasize eccentric strength training, is the lack of attention to musculature adjacent to the hamstrings. It has been suggested that neuromuscular control of the lumbopelvic region is needed to enable optimal function of the hamstrings during normal sporting activities.

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Rehabilitation protocol

Phase I (week 0-3)

• Goals

1. Protect healing tissue
2. Minimize atrophy and strength loss
3. Prevent motion loss

• Protection

1. Avoid excessive active or passive lengthening of hamstring
2. Avoid antalgic gait pattern

• Rehab

1. Ice – 2-3 times daily
2. Stationary bike
3. Sub maximal isometric at 90, 60 and 30
4. Single leg balance
5. Balance board
6. Soft tissue mobs/IASTM
7. Pulsed ultrasound (Duty cycle 50%, 1 MHz, 1.2 W/cm2)
8. Progressive hip strengthening
9. Painfree isotonic knee flexion
10. Active sciatic nerve flossing
11. Conventional TENS

• Criteria for progession to next phase

1. Normal walking stride without pain
2. Pain-free isometric contracton against submaximal (50%-75%) resistance during prone knee flexion at 90.

Phase 2 (week 3-12)

• Goals

1. Regain pain-free hamstring strength, progressing through full ROM
2. Develop neuromuscular control of trunk and pelvis with progressive increase in movement and speed preparing for functional movements

• Protection

1. Avoid end-range lengthening of hamstring if painful

• Rehab

1. Ice – post exercise
2. Stationary bike
3. Treadmill at moderate to high intensity pain-free speed and stride
4. Isokinetic eccentrics in non-lengthened state
5. Single limb balance windmill touches without weight
6. Single leg stance with perturbations
7. Supine hamstring curls on theraball
8. STM/IASTM
9. Nordic hamstring Ex
10. Shuttle jumps
11. Prone leg drops
12. Lateral and retro bandwalks
13. Sciatic nerve tensioning

• Eccentric protocol

1. Once non-weight bearing exercises are tolerated start low-velocity eccentric activities such as stiff leg dead lifts, eccentric hamstring lowers/Nordic hamstring Ex, and split squats

• Criteria for progression

1. Full strength 5/5 without pain during prone knee flexion at 90
2. Pain-free forward and backward, jog, moderate intensity
3. Strength deficit less than 20% compared against uninjured limb
4. Pain free max eccentric in a non-lengthened state

Phase 3 (week 12+)

• Goals

1. Symptom free during all activities
2. Normal concentric and eccentric strength through full ROM and speed
3. Improve neuromuscular control of trunk and pelvis
4. Integrate postural control into sport-specific movements

• Protection

1. Train within symptoms free intensity

• Rehab

1. Ice – Post exercise – as needed
2. Treadmill moderate to high intensity as tolerated
3. Isokinetic eccentric training at end ROM (in hyperflexion)
4. STM/IASTM
5. Plyometric jump training
6. 5-10 yard accelerations/decelarations
7. Single-limb balance windmill touches with weight on unstable surface
8. Sport-specific drills that incorporate postural control and progressive speed

• Eccentric protocol

1. Include higher velocity eccentric Ex that include plyometric and sports specific activities
2. Examples include squat jumps, split jumps, bounding and depth jumps
3. Single leg bounding, backward skips, lateral hops, lateral bounding and zigzag hops and bounding
4. Plyometric box jumps, eccentric backward steps, eccentric lunge drops, eccentric forward pulls, single and double leg deadlifts, and split stance deadlift (good morning Ex)

• Return to sport criteria

1. Full strength without pain in the lengthened state testing position
2. Bilateral symmetry in knee flexion angle of peak torque
3. Full ROM without pain
4. Replication of sport specific movements at competition speed without symptoms.
5. Isokinetic strength testing should be performed under both concentric and eccentric action conditions. Less than a 5% bilateral deficit should exist in the ratio of eccentric hamstring strength (30d/s) to concentric quadriceps strength (240d/s).
   

Resources

•  ↑ 1.0 1.1 1.2 Sutton G. (1984) Hamstrung by hamstring strains: a review of the literature*.J Orthop Sports Phys Ther. 5(4):184-95. (Level of evidence = 3B )
  
•  ↑ 2.0 2.1 Schunke M., Schulte E., Schumacher (2005). Anatomische atlas Prometheus: Algemene anatomie en bewegingsapparaat. Nederland: Bohn Stafleu Van Loghum
•  E. Cattrysse, S. Provyn, A. Scafoflieri, P. Van Roy, J.P. Clarijs, P. Van Noten, J. Tresignie, S. Vantiegem, V. Jannsens, E. Schaillée; Compendium Topografische en Kinesiologische Ontleedkunde; Vrije Universiteit Brussel; Brussel; 2015-2016
  
•  ↑ 3.0 3.1 Coole WG, Gieck JH.(1987) An analysis of hamstring strains and their rehabilitation. J Orthop Sports Phys Ther 9(3):77-85.
•  ↑ Taylor M.P., Taylor K. D. (1988). Conquering athletic injuries. Illinois: Leisure press.
• 6 = 4
•  M. Tuerlinckx; “Quadriceps Muscle Strain”; Physiopedia.com; URL: http://www.physio-pedia.com/Quadriceps_Muscle_Strain
  
•  E. Van Haver; “Muscle Injuries”; Physiopedia.com; URL: http://www.physio-pedia.com/Muscle_Injuries
•  ↑ 6.0 6.1 6.2 Petersen J, Hölmich P. Preventie van hamstringblessures in de sport, "evidence based” Geneeskunde en Sport 2005; 38: 179-185 (Level of evidence = 3A )
•  ↑ Klafs CE, Arnheim DD: ( 1968 ) Principles of Athletic Training, Ed pp 370-372. St Louis: CV Mosby Co.
•  ↑ 4.0 4.1 Worrell, T.W.,Perrin, D.H. (1992). Hamstring muscle injury: the role of strength, flexibility, warm-up, and fatigue. Journal of Orthopaedic and Sports Physical Therapy, 16, 12-18. (Level of evidence = 5)
•  ↑ Brockett CL, Morgan DL, Proske U. Predicting hamstring strain injury in elite athletes. Med Sci Sports Exerc 2004 Mar; 36 (3): 379-87
•  ↑ 9.0 9.1 Opar MD, Williams MD, Shield AJ. Hamstring strain injuries. Sports medicine. 2012 Mar 1;42(3):209-26.
•  ↑ Abebe E, Moorman C, Garrett Jr W. Proximal hamstring avulsion injuries: injury mechanism, diagnosis and disease course. Oper Tech Sports Med 2009; 17 (4): 205-9
• 15 = 7
•  ↑ 11.0 11.1 Bryan C. Heiderscheit, PT, PhD, et al. (2010) Hamstring Strain Injuries: Recommendations for Diagnosis, Rehabilitation, and Injury Prevention. In Journal of Orthopaedic; Sports Physical Therapy (Level of evidence = 5)
• 17 = 35
• 18 = 34
• 19= 33
• 20 = 7
• 21 = 32
  
•  Validation of the FASH (Functional Assessment Scale for Acute Hamstring Injuries) questionnaire for German-speaking football players, Heinz Lohrer et al., Pubmed, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5078932/
• ↑ Cross MJ, Vandersluis R, Wood D, Banff M (1998) Surgical repair of chronic complete hamstring tendon rupture in the adult patient. Am J Sports Med 26(6):785–788 (Level of evidence = 2B)
•  Hamstring strain injuries: recommendations for diagnosis, rehabilitation, and injury prevention., Heiderscheit BC et al., Pumbed, https://www.ncbi.nlm.nih.gov/pubmed/20118524
•  Rehabilitation After Hamstring Strain Injury Emphasizing Eccentric Strengthening at Long Muscle Lengths: Results of Long Term Follow-up., Tyler TF et al., Pubmed, https://www.ncbi.nlm.nih.gov/pubmed/27632842 Level of evidence: 2
  
• 27 = 31
•  Effect of deep stripping massage alone or with eccentric resistance on hamstring length and strength., Forman J et al., Pubmed https://www.ncbi.nlm.nih.gov/pubmed/24411162 Level of evidence: 4
• 29 = 31
• 30 = 32
•  Treatment of hamstring strain in a collegiate pole-vaulter integrating dry needling with an eccentric training program: a resident's case report., Dembowski SC et al., https://www.ncbi.nlm.nih.gov/pubmed/?term=dry+needling+and+hamstring+strain Level of evidence: 4

•  Temporal efficacy of kinesiology tape vs. Traditional stretching methods on hamstring extensibility.Farquharson C et al., Pubmed, https://www.ncbi.nlm.nih.gov/pubmed/25709862 level of evidence : 2
  

•  Validation of the FASH (Functional Assessment Scale for Acute Hamstring Injuries) questionnaire for German-speaking football players, Heinz Lohrer et al., Pubmed, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5078932/
  

•  Jeffrey M. Heftler; "Hamstring Strain Clinical Presentation http://emedicine.medscape.com/article/307765-clinical#b4
•  ↑ Starkey C and Johnson G (2006) Athletic training and sport medicine. United States of America: Jones and Barlett publishers
  

Recent Related Research (from <a href="http://www.ncbi.nlm.nih.gov/pubmed/">Pubmed</a>)

http://www.ncbi.nlm.nih.gov/entrez/eutils/erss.cgi?rss_guid=1pwP1t1nr4XhjCZxQim64K0Sb4uq4Evw0ahSWz06Y95ZCyYMOk%7Ccharset=UTF-8%7Cshort%7Cmax=10

References

<span class="fck_mw_references" _fck_mw_customtag="true" _fck_mw_tagname="references" />

<a _fcknotitle="true" href="Category:Injury">Injury</a> <a _fcknotitle="true" href="Category:Sports_Injuries">Sports_Injuries</a> <a _fcknotitle="true" href="Category:Thigh">Thigh</a> <a _fcknotitle="true" href="Category:Thigh_Injuries">Thigh_Injuries</a> <a _fcknotitle="true" href="Category:Musculoskeletal/Orthopaedics">Musculoskeletal/Orthopaedics</a> <a _fcknotitle="true" href="Category:Vrije_Universiteit_Brussel_Project">Vrije_Universiteit_Brussel_Project</a>