A submaximal test to assess back muscle capacity: evaluation of construct validity

Area of Science:

• Kinesiology
• Biomechanics
• Occupational Health

Background:

• Assessing back muscle capacity is crucial for understanding functional limitations.
• Existing tests may not accurately reflect real-world occupational demands.
• Chronic low-back-pain patients often exhibit back muscle weakness and fatigability.

Purpose of the Study:

• To propose and validate a novel functional endurance test for back muscles.
• To determine if the test's performance is influenced by subject strength and relative endurance.
• To confirm the construct validity of this new functional endurance test.

Main Methods:

• A static intermittent contraction test (8-s work-rest cycles) with a fixed absolute load (90 Nm) was employed.
• Fifteen males and 17 females participated, undergoing assessments over three days for familiarization, strength, and endurance measurements.
• Absolute endurance (Tend(abs)) and relative endurance (Tend(rel)) were measured using both absolute (90 Nm) and relative (40% strength) loads at the L5/S1 joint.

Main Results:

• The functional endurance test demonstrated construct validity.
• Both subject strength and relative endurance significantly contributed to absolute endurance performance (explaining 61.5% of the variance).
• The test successfully differentiated between strength and fatigability components of back muscle capacity.

Conclusions:

• The proposed functional endurance test is a valid measure of back muscle capacity.
• This test is more specific to occupational tasks than previous methods.
• The test has the potential to better identify back muscle impairments in individuals with chronic low-back pain.