Electromyogram patterns during plantarflexions at various angular velocities and knee angles in human triceps surae...

Area of Science:

• Biomechanics
• Human Physiology
• Exercise Science

Background:

• Understanding synergistic muscle activity is crucial for optimizing athletic performance and rehabilitation.
• The triceps surae muscles (lateral gastrocnemius, medial gastrocnemius, soleus) play a key role in ankle plantarflexion.
• Previous research has explored muscle activation patterns, but the combined influence of knee angle and ankle angular velocity requires further investigation.

Purpose of the Study:

• To investigate how varying knee angles and ankle angular velocities influence the synergistic muscle activities of the triceps surae.
• To determine the specific recruitment patterns of the lateral gastrocnemius, medial gastrocnemius, and soleus muscles under different biomechanical conditions.

Main Methods:

• Surface electromyograms (EMG) were recorded from the lateral gastrocnemius (LG), medial gastrocnemius (MG), and soleus (SOL) muscles in six healthy young men.
• Participants performed ankle plantarflexions at three ankle angular velocities (6, 30, 60 degrees/s) and three knee angles (0, 30, 60 degrees) under constant load (5-10% MVC).
• Peak integrated EMG (iEMG) values were analyzed to assess muscle activity.

Main Results:

• At 0 degrees knee angle, increasing ankle angular velocity significantly increased peak iEMG in MG and LG, while decreasing it in SOL (P < 0.05).
• At flexed knee angles (30 and 60 degrees), muscle activity patterns showed no significant differences across angular velocities.
• Increasing knee flexion angles significantly increased peak iEMG in SOL and decreased it in MG during plantarflexion at all tested velocities (P < 0.05).

Conclusions:

• Motor unit recruitment in the triceps surae muscles can be selectively influenced by ankle angular velocity, particularly at full knee extension.
• Flexed knee positions appear to attenuate velocity-dependent muscle recruitment, potentially due to inhibitory effects on gastrocnemii and facilitative effects on the soleus.
• These findings highlight the complex interplay between joint angles and movement speed in modulating muscle activation strategies.