Posterior muscle chain activity during various extension exercises: an observational study

Area of Science:

• Biomechanics
• Exercise Physiology
• Rehabilitation Science

Background:

• Back extension exercises are common in low back pain rehabilitation.
• Muscle recruitment patterns during these exercises are not well understood.
• This study investigates posterior muscle activation during different extension exercises.

Purpose of the Study:

• To evaluate the myoelectric activity of thoracic, lumbar, and hip extensor muscles.
• To compare muscle recruitment during various trunk and leg extension exercises.
• To provide recommendations for clinical application of extension exercises.

Main Methods:

• Fourteen healthy subjects performed four standardized extension exercises (dynamic and dynamic-static trunk/leg extensions).
• Surface EMG of key posterior muscles (Latissimus dorsi, Longissimus thoracis, Iliocostalis lumborum, Multifidus, Gluteus Maximus) was recorded.
• EMG root mean square values were analyzed using mixed model analysis.

Main Results:

• Posterior chain muscles showed higher recruitment during trunk extension (56.6% MVC) versus leg extension (47.4% MVC).
• Thoracic muscles (LTT, ILT) were more recruited during trunk extension.
• No significant differences in muscle activity were found between dynamic and dynamic-static exercises.

Conclusions:

• Muscle recruitment is influenced by the moving body part (trunk vs. leg), not the contraction type.
• Trunk extensions enhance thoracic muscle activation; leg extensions are more suitable for lumbar muscle endurance.
• Specific exercises are not recommended for Latissimus dorsi and Gluteus Maximus endurance training.