The factors that are being implicated in this trend are the relative deterioration and muscle weakness that occur during the off-season.The hamstrings undergo a complex dynamic process during gait, making it unsurprising that they are frequently injured. They must first contract concentrically during the end of the stance phase in order to bend the knee and allow the foot (along with dorsiflexion at the ankle) to clear the ground. At the end of the swing phase, the hamstrings must eccentrically contract while applying a braking moment to knee extension, then immediately change functions to again concentrically contract and produce hip extension. Studies have shown that "the hamstring group reaches peak elongation and acts eccentrically at the hip and knee during the late swing phases of running" and that "the hamstrings are most active and develop the greatest torques at the hip and knee during the late swing through midstance phase of running." Thus, the hamstrings reach their maximum length while attempting to forcefully contract eccentrically and switch functions to immediately produce a concentric contraction, which makes the terminal part of swing phase the most vulnerable for injury. There have been many other proposed predisposing factors to injury. These include muscle weakness, muscle imbalance, poor flexibility, fatigue, inadequate warm up, poor neuromuscular control, and poor running technique. One of the few predisposing factors that most researchers agree upon however is previous hamstring injury. Brokett et al.
There is an immediate burning or stabbing pain and the individual is unable to walk without pain. The muscle is completely torn and there may be a large lump of muscle tissue above a depression where the tear is. After a few days with grade two and three injuries, a large bruise may appear below the injury site caused by the bleeding within the tissues. Treatment
Recommended treatment for this injury consists of the RICE protocol — rest, ice, compression and elevation. The RICE method is primarily used to reduce bleeding and damage within the muscle tissue. Lower grade strains can easily become worse if the hamstring is not rested properly. Complete ruptures require surgical repair and rehabilitation. Initial treatment of the injury, regardless of the severity of the strain, is the same. Within the first five days, the hamstring is rested in an elevated position with an ice pack applied for twenty minutes every two hours. A compression bandage is applied to limit bleeding and swelling in the tissues. After five days of rest, active rehabilitation begins. Epidemiology
An academic study found that the most common and prevalent musculoskeletal injury in the world is a hamstring strain. The study further explains that hamstring strains represented 15% of all injuries per club per season also had a 34% chance of recurrence. Another study showed that a previous hamstring injury is one of the most cited risks for future injury, with as many as one-third of active individuals experiencing a re-injury within 2 weeks of returning to activity.