Relationship between metabolic function and skeletal muscle fatigue during a 90 s maximal isometric contraction

Area of Science:

• Exercise Physiology
• Skeletal Muscle Metabolism

Background:

• Fatigue resistance is influenced by muscle energy systems, but their specific contributions remain unclear.
• Understanding these metabolic pathways is key to optimizing athletic performance and recovery.

Purpose of the Study:

• To model fatigue resistance using muscle tissue metabolic measures during maximal short-duration isometric contractions.
• To identify the independent predictors of fatigue resistance among key energy systems.

Main Methods:

• Utilized [31P]-magnetic resonance spectroscopy (MRS) to measure muscle metabolic function.
• Assessed 54 premenopausal women performing 100% isometric plantar flexions.
• Employed multiple regression analysis to determine the predictive power of metabolic variables.

Main Results:

• Oxidative phosphorylation (OxPhos), anaerobic glycolytic rate (AnGly), maximum creatine kinase (CK) activity, and metabolic economy (ME) were all independent predictors of fatigue resistance.
• Metabolic economy (ME) explained the largest variance (36%), followed by OxPhos as the most significant energy system.
• Creatine kinase (CK) activity persisted throughout 90 seconds of maximal exercise.

Conclusions:

• OxPhos, AnGly, CK, and ME collectively contribute to short-duration fatigue resistance.
• The sustained activity of CK supports its role in facilitating mitochondrial energy transfer via a CK shuttle mechanism.