Does the global temporal activation differ in triceps surae during standing balance?

Area of Science:

• Biomechanics
• Human Physiology
• Motor Control

Background:

• The triceps surae muscle group is vital for maintaining upright standing balance.
• Understanding the specific activation patterns of its components, medial gastrocnemius (MG) and soleus (SOL), is essential for postural control research.

Purpose of the Study:

• To investigate and compare the temporal activation patterns of the medial gastrocnemius (MG) and the medial (MSOL) and lateral (LSOL) portions of the soleus muscle during upright stance.
• To determine if these differences contribute to the maintenance of standing balance in young adults.

Main Methods:

• Nine healthy young males participated in the study.
• Participants performed quiet standing and voluntary anterior-posterior postural sway tasks.
• Surface electromyograms (EMGs) were recorded from MSOL, LSOL, and MG using linear electrode arrays.
• The temporal index, representing the percentage of muscle activation over time, was calculated for each muscle.

Main Results:

• The medial soleus (MSOL) exhibited continuous muscle activation throughout the standing tasks.
• In contrast, the lateral soleus (LSOL) and medial gastrocnemius (MG) displayed intermittent activation patterns.
• These distinct temporal activation profiles were observed during both quiet stance and postural sway.

Conclusions:

• The postural control system employs differential temporal activation strategies for the medial and lateral portions of the soleus muscle, as well as the medial gastrocnemius.
• These findings highlight specific roles of triceps surae components in maintaining standing balance, suggesting a complex interplay for postural stability.