Guest blog by Paul Head
Paul holds a BSc Sports Therapy degree from University of Central Lancashire (UCLAN) and is a pre reg physiotherapy student. He received first Class Honours Classification (78% average) and an award for Academic Excellence in the field of sports therapy / physiotherapy from DJO UK. Find out more about Paul here…
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Hamstring strain injuries comprise a substantial percentage of acute musculoskeletal injuries incurred during sporting activities. They are the most prevalent muscle injuries reported in sport. Hamstring injuries account for between 6 and 29% of all injuries reported in Australian Rules football, rugby union, soccer, basketball, cricket and track sprinters (Mendiguchia and Brughelli, 2010). Participants in athletics, football and rugby are especially prone to this injury given the sprinting demands of these sports, while dancers have a similar susceptibility due, in part, to the extreme stretch incurred by the hamstring muscles.
Hamstring strain re injury rates have been shown to be 12-30% (Mendiguchia and Brughelli, 2010). With some of world’s most high profile sportsmen including Lionel Messi, LeBron James, Darren Clarke and Ashley Cole recently being sidelined due to hamstring injuries it is still a major problem today. This post will aim to go through how hamstring strains occur and hamstring exercises to improve prevention and rehabilitation. Part 1 goes through the anatomy, mechanism and assessment of hamstring strain injuries. Part 2 goes through the best evidence based exercises to prevent and rehabilitate hamstring strain injuries.
The hamstring muscle group consists of the semimembranosus, semitendinosus and bicep femoris muscles. All three muscles originate from the ischial tuberosity apart from the short head of bicep femoris which originates from the linea aspera and lateral supercondylar ridge of the femur. The semimembranosus inserts onto the medial condyle of the tibia. The semitendinosus inserts onto the superior medial surface of the tibia and the oblique popliteal ligament and both heads of the bicep femoris muscle insert onto the head of fibular. All 3 muscles are innervated by the tibial nerve with the short head of the bicep femoris being innervated by the common peroneal nerve. The hamstrings have a fascial connection to the peroneus brevis muscle linking to actions at the foot and the ankle, and the sacrotuberous ligament linking it with the pelvis and thoracolumbar fascia (Hoskins and Pollard, 2005).
[Accessed from www.morphopedics.wikidot.com]
Mechanism of Injury
The hamstrings can be injured by two main mechanisms, a sprinting type injury, that occurs at high-speed running and/or acceleration or by a stretching type injury that occurs during movements with large joint stretch moments that include; high kicking, split positions and glide tackling. The late swing phase of running is when the hamstrings are most prone to injury during. Yu et al. (2005) suggested that hamstring muscles were at risk from a strain injury during the late stance phase as well as during the late swing phase. However, hamstrings may have higher risk for strain injury during the late swing phase than during the late stance phase because the lengths of the hamstring muscles are significantly longer during the late swing phase than during the late stance phase.
The Bicep femoris muscle is the most commonly injured of the three hamstring muscles. It has two different nerve supplies and it reaches the greatest length and also greatest increase in length when eccentrically decelerating the anterior displacement of the lower leg during high speed running. It is the most commonly injured muscle in sprinting type mechanisms which is sometimes associated with a semitendinosus tear. The semimembranosus is the most commonly affected muscle in over stretching type mechanism hamstring strains.
In a recent literature review it was found that the most significant and consistent predisposing factors for getting a hamstring strain were: age, weight and previous hamstring injury. With more research needed to identify other predisposing factors including: quadriceps peak torque, hamstring flexibility, weight, hip flexor flexibility, ankle dorsiflexion ROM, hamstring peak torque, previous sacroiliac joint dysfunction and lumbar spine injury to determine whether they correlate fully with hamstring strain injuries (Freckleton and Pizzari, 2010).