Relationship between back muscle endurance and voluntary activation.

Area of Science:

• Kinesiology
• Neuromuscular Physiology
• Musculoskeletal Health

Background:

• The Biering-Sorensen test assesses back muscle endurance and its relation to low back pain.
• This test's efficacy may depend on voluntary activation (VA) of back muscles.
• VA, the neural drive to muscles, can be quantified using twitch interpolation.

Purpose of the Study:

• To investigate the relationship between back muscle endurance and voluntary activation (VA) in healthy individuals.
• To determine if VA influences performance in the Biering-Sorensen endurance test.

Main Methods:

• Twenty-one healthy volunteers underwent bilateral electromyographic recordings of erector spinae and rectus abdominis.
• Back extensor torque was measured using a dynamometer.
• Voluntary activation (VA) was assessed via magnetic brain stimulation and evoked twitches; endurance was measured concurrently.

Main Results:

• A significant linear correlation (r(2)=1, P<0.01) was found between voluntary torque and VA.
• No significant correlation was observed between endurance time and VA at maximal (100% MVC) or submaximal (50% MVC) effort.
• Mean endurance time was 174.9 (12.8)s.

Conclusions:

• Back muscle endurance, as measured by the Biering-Sorensen test, is not directly related to the capacity for voluntary muscle activation.
• The findings suggest that factors other than neural drive may limit back muscle endurance in this test.
• This has implications for understanding the mechanisms underlying back pain and the predictive validity of endurance tests.