Hamstring strains are one of the most common sporting injures, and they are often associated with sports which involve repetitive bouts of maximal sprinting (Schache et al, 2011), and sports with kicking and sudden acceleration (Arnason et al, 2008). These injuries are also prone to high recurrence rates (Schache et al, 2011). They are often injured as a result of sudden hip flexion (driving knee up) combined with knee extension or straightening of the lower leg (Ali & Leland, 2012). Hamstring injuries are thought to occur due to the large amount of eccentric (muscle lengthening under tension) force generated when running. Arnason et al (2008) noted that EMG analyses of sprinting has that muscle activity is highest during the late swing phase of the movement. During this phase the hamstrings are working eccentrically to slow the speed of the lower leg as well as during the foot strike. This overloading of the muscle is what may be causing tearing to the musculotendinous unit (MTU).
The severity of the injury can be classified into 3 grading categories. Grade 1:Overstretching of the muscle with minimal loss to the structural integrity of the musculotendinous unit. Grade 2: Partial or incomplete tears to the muscle or (MTU). Grade 3: This is the most severe injury resulting to a complete rupture of the muscle body or detaching of the muscle tendon from its origin (Ali & Leland, 2012).
Common risk factors include: those with a history of hamstring strains, poor flexibility, muscle fatigue, and insufficient warm up (Arnason, 2008). Other risk factors include older age, ethnicity and muscle strength deficits. There is particular interest regarding the strength of a muscle because this is the only modifiable risk factor (Schache et al, 2011). Opar et al (2012) state that the focus should be on developing the eccentric strength of the hamstring muscles, correcting muscle imbalances, and improve flexibility as a method to decrease the incidence of hamstring strain injuries.
⦁ Signs and symptoms of injury include: tenderness over the proximal aspect of the posterior thigh when palpated, pain and loss of ROM, pain and weakness in muscle contraction (Schache et al, 2011). Those with acute hamstring strains usually have pain when weight bearing, and present a stiff legged gait as a result of avoiding knee and hip flexion (Ali & Leland, 2012). People tend to note a popping feeling accompanied by pain at the time of the injury.
⦁ Treatment for acute hamstring strains (Grade 1 or 2) is to use the RICE (rest, ice, compression, elevation) protocol to help control the initial inflammatory response. For complete tears (Grade 3) or chronic hamstring pains, surgery is often the only solution. Those with chronic hamstring strains are known to have ‘hamstring syndrome’. These people report pain in the ischial tuberosity (sitting bones at the bottom area and have ‘shooting’ pain down the posterior aspect of their thigh. This occurs because each time they suffered a hamstring strain, scar tissue would build up around the injury site, commonly the muscle tendinous unit. As this scar tissue builds up over a period of time, it begins to impinge on the sciatic nerve resulting in pain (Ali & Leland, 2012).
⦁ Phases of healing
⦁ Acute inflammatory phase: this occurs immediately after the injury occurs. In this phase the body acts to protect the site by immobilising it through swelling to prevent further damage. The swelling is due to increased blood flow and other fluid to the area which often results in discolouration. The aim of this stage is to bring more cells (in particular white blood cells) to the area to fight against infection, control any internal bleeding, and prepare the area for the repair stage (Hardy, 1989).
⦁ Fibroplastic phase: Also known as the repair stage occurs immediately after the inflammatory phase is completed. In this phase, cells such as Fibroblasts go about rebuilding the structural frame work of the damaged tissue by laying down collagen scar tissue. The purpose of this stage is to resurface the wound, and bring back strength to the area. This process can take up to 3 weeks to complete (Hardy, 1989).
⦁ Remodelling phase: the goal of this stage is to return normal function to the area. This is achieved by remodelling the newly formed scar tissue, and turning it into functional tissue. This is achieved by changing the orientation and arrangement of collagen fibres (Hardy, 1989).
⦁ Goals of each phase
⦁ Acute phase: Restore full ROM of the knee to 130-140º extension, and 90-135º hip flexion by the end of week 2 (ACSM, 2010). Be able to walk with a normal gait by end of week 1.
⦁ Repair phase: Re-gain strength of the injured leg to that of the uninjured by end of week 5. Be able to run at a moderate pace by end of week 5. Maintain flexibility of hamstrings.
⦁ Remodelling phase: Be able to sprint at maximal effort without pain or discomfort by end of week 8. Perform functional tests from part C without any pain or discomfort by end of week 8.
⦁ Acute phase: 2 weeks; Repair phase: 3 weeks; Remodelling phase: 3 weeks. Note: these are only guidelines. Ali and Leland (2012) state that gradual return to sports can be made over 4-6 weeks.
Notes: Tempo starts with the eccentric phase (eccentric, pause, concentric, pause). X= perform as fast as possible.
A strong emphasis was put on time under tension on the eccentric phase of the movement in the acute and repair stages.
Functionally Progressive Exercises:
⦁ Side lunges
⦁ Single leg squats
⦁ Tuck jumps
⦁ Standing long jump
⦁ High knee skipping
⦁ Multi directional sprints
You would first need to be able to perform all above tests competently, and without pain or discomfort.
It is important to remember that these are just guidelines which are based on current research. Each injury is different and may present other complications. Please seek medical advice from your GP or physiotherapist to get a proper diagnosis and appropriate treatment plan.
Anarson, A., Anderson, T.E., Holme, I., Engebretson, R., & Bahr. (2008). Prevention of hamstring strains in elite soccer: an intervention study. Scandinavian Journal of Medicine and Science in Sports, 18, 1, 40-48.
Ali, K., Leland, M.J. (2012). Hamstring strains and tears in the athlete. Clinics in Sport Medicine, 31, 2, 263-272.
Opar, D.A., Williams, M.D., & Shield, A.J. (2012). Hamstring strain injuries: Factors that lead to injury and re-injury. Sports Medicine, 42, 3, 209-226.
Schache, G.A., Crossley, K.M., Macindoe, I.G., Fahrner, B.B., & Pandy, M.G. (2011). Can clinical testing of hamstring strength identify football players at risk of hamstring strain? Knee Surgery Sports Traumatology Arthroscopy, 19, 1. 38-41
Thompson, W.R. (Ed). American College of Sports Medicine. 2010 ACSM’s guidelines for exercise testing and prescription. (8th ed.). Baltimore, MD: Lippincott Williams and Wilkins.
Hardy, M.A. (1989). The biology of scar formation. Journal of the American Physical Therapy Association, 69, 12, 1014-1024.
TAGGED: COMMON INJURIES, EXERCISE REHABILITATION, HA
NOVEMBER 30, 2016
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