Differences in hamstring activation characteristics between the acceleration and maximum-speed phases of sprinting

Area of Science:

• Biomechanics
• Sports Science
• Human Movement

Background:

• The hamstring muscles, specifically the biceps femoris long head (BFlh) and semitendinosus (ST), play crucial roles in sprinting.
• Understanding their differential activation patterns during various sprint phases is essential for optimizing performance and preventing injuries.

Purpose of the Study:

• To investigate and compare the electromyographic (EMG) activation characteristics of the BFlh and ST muscles during the acceleration and maximum-speed phases of sprinting.
• To determine differences in hamstring muscle activation, joint kinematics, and torques between these two distinct sprinting phases.

Main Methods:

• Electromyography (EMG) and lower-extremity kinematics were recorded in 13 male sprinters during overground acceleration and maximum-speed sprints.
• Analysis focused on comparing hamstring muscle activation, hip and knee joint angles, and torques at specific points within the sprinting gait cycle.

Main Results:

• During early stance acceleration, hip extension torque was higher, with greater relative BFlh activation compared to ST.
• In maximum-speed sprinting, the knee was more extended with a higher flexion moment during late stance and terminal mid-swing, showing higher ST activation than BFlh.

Conclusions:

• The functional demands on the medial (ST) and lateral (BFlh) hamstring muscles are distinct between acceleration and maximum-speed sprinting phases.
• These findings suggest that training programs should consider the differential activation patterns of hamstring muscles for improved sprinting performance.