Question
What are the common mechanisms of hamstring injuries and their impact on the recovery process?
Answer
Hamstring injuries are common among athletes, particularly those involved in high-speed, high-acceleration sports such as sprinting and jumping. Understanding the mechanisms of these injuries is crucial for effective rehabilitation and preventing recurrence.
Mechanisms of Injury:
- High Muscle-Tendon Unit Force: These injuries often occur at end ranges of motion where the muscle-tendon unit is subjected to high forces, either actively or passively. High-speed running, kicking, acceleration, and change of direction are typical activities leading to hamstring injuries.
- Lengthening Beyond Moderate Length: Injuries can also occur when the musculotendinous unit lengthens excessively, as seen in stretching-type injuries.
- High Velocity Movements: These injuries are more common in speed positions (e.g., wide receivers, running backs, basketball players) than in strength positions (e.g., offensive and defensive linemen in football).
Types of Hamstring Injuries:
- Type 1 (Force Mitigation): Common in sprinters, this injury occurs when the hamstring eccentrically contracts during the terminal swing phase of the running cycle. It typically affects the biceps femoris muscle and occurs more proximally.
- Type 2 (Stretch-Type): Seen in activities involving high hip flexion and knee extension (e.g., dancing, high kicking). This type affects the semimembranosus tendon and can occur in open and closed chain movements.
Recovery and Prognosis:
- Proximal vs. Distal Injuries: Proximal injuries near the ischial tuberosity tend to take longer to heal due to poorer blood supply compared to distal injuries in the muscle belly.
- Reoccurrence Rate: Hamstring injuries have a high recurrence rate, ranging from 14% to 34%, with many recurrences occurring within the first two weeks of return to sport. This highlights the importance of thorough rehabilitation and appropriate return-to-play criteria.
- Impact of High-Speed Running: The force on the hamstring increases significantly (1.3 times) when running speed increases from 80% to 100%, underscoring the need for rehabilitation exercises to mimic the high-speed demands of the sport.
Effective rehabilitation involves a combination of eccentric exercises, core stability training, and a structured return-to-play plan that addresses both strength and functional movement patterns. By understanding the specific mechanisms and types of hamstring injuries, sports medicine professionals can develop tailored rehabilitation protocols that enhance recovery and reduce the risk of re-injury.
This Ask the Expert is an edited excerpt from the course, "Rehabilitation for Hamstring Injuries: How Do We Achieve Success?" presented by JD Boudreaux, PT, EdD, ATC, SCS.
