Trunk muscle activity during lumbar stabilization exercises on both a stable and unstable surface

Area of Science:

• Biomechanics
• Exercise Physiology
• Neuromuscular Control

Background:

• Lumbar stabilization exercises are commonly performed on unstable surfaces.
• A perceived benefit is increased muscular demand, but evidence is limited.
• This study investigates the influence of surface stability on trunk muscle activation.

Purpose of the Study:

• To determine if surface stability affects trunk muscle activity during lumbar stabilization exercises.
• To compare electromyographic (EMG) activity of key trunk muscles between stable and unstable surfaces.

Main Methods:

• Nine healthy males performed five lumbar stabilization exercises (elbow-toe, hand-knee, curl-up, side bridge, back bridge) on both stable and unstable surfaces.
• Intramuscular or surface EMG recorded activity of rectus abdominis, external obliques, transversus abdominis, erector spinae, and lumbar multifidus.
• EMG data were normalized to maximum voluntary contraction and compared using the Wilcoxon signed-rank test.

Main Results:

• Elbow-toe exercise showed enhanced activity in all recorded trunk muscles on the unstable surface.
• Hand-knee and side bridge exercises demonstrated increased activity in global trunk muscles on the unstable surface.
• Curl-up exercise resulted in increased external oblique activity but decreased transversus abdominis activation on the unstable surface.

Conclusions:

• Lumbar stabilization exercises on unstable surfaces generally enhance trunk muscle activation.
• The effect varies by exercise type, with the back bridge exercise showing no enhancement.
• Findings suggest that unstable surfaces can augment training stimulus for specific trunk muscles.