Biomechanics of Movement | Lecture 6.4: Using Musculoskeletal Geometry to Compute Hamstring Velocity

Muscle-Tendon Velocity Analysis in Sprinting

Importance of Studying Hamstring Muscle Tendon Velocities

• The analysis of muscle-tendon velocities, particularly in the hamstrings during sprinting, is crucial due to the high incidence of hamstring injuries across various sports.

• Hamstring injuries are often severe and recurrent, leading athletes to miss entire seasons. These injuries typically occur during eccentric contractions when muscles stretch at high velocity and force.

Musculoskeletal Geometry Setup

• The setup for analyzing muscle-tendon velocities involves understanding the anatomy: the pelvis, thigh, shank, and specifically focusing on the biceps femoris long head as a representative hamstring muscle.

• This muscle crosses two joints (hip and knee), generating moments for hip extension and knee flexion. Its moment arm changes with joint angles.

Calculating Muscle Length Changes

• The length of the hamstrings is influenced by both hip flexion angle and knee flexion angle; this complexity increases in three-dimensional movement.

• To determine hamstring velocity during sprinting, one can measure joint angles through motion capture experiments.

Deriving Velocity from Joint Angles

• By applying angular velocities to the moment arm equation (moment arm = change in length/change in angle), we derive that the change in length over time (velocity) equals moment arm times angular velocity.

• This relationship allows us to calculate how fast the hamstrings are stretching based on measured joint angles and their respective angular velocities.

Total Muscle-Tendon Complex Velocity Calculation

• The total velocity of the muscle-tendon complex is calculated as a sum of products: each moment arm multiplied by its corresponding joint angular velocity across all joints involved.

• This method illustrates how musculoskeletal geometry can be applied practically to assess hamstring velocities during sprinting effectively.

Summary of Key Concepts Discussed