Altered Skeletal Muscle Phosphate Metabolism After Muscle Damage Is Associated With Elevated Effort Perception During...

Area of Science:

• Exercise physiology
• Muscle metabolism
• Biophysics

Background:

• Muscle damage from eccentric exercise (EIMD) increases perceived exertion.
• Inorganic phosphate (Pi) plays a role in muscle fatigue and sensory signaling.
• The link between muscle damage, phosphate metabolism, and perceived effort remains unclear.

Purpose of the Study:

• To investigate if muscle damage disrupts phosphate metabolism.
• To determine if disrupted phosphate metabolism is associated with heightened ratings of perceived exertion (RPE).

Main Methods:

• Eighteen adults underwent assessments before and 48 hours after EIMD.
• Magnetic resonance imaging (MRI) quantified quadriceps cross-sectional area (Qcsa).
• 31P-MR spectroscopy measured muscle phosphate metabolites (Pi, PCr, ATPγ) and pH at rest, during exercise, and recovery. RPE was recorded.

Main Results:

• EIMD increased muscle soreness, reduced maximal voluntary contraction, and increased Qcsa.
• Sustained elevations in resting Pi and Pi/PCr ratios, with lower ATPγ, were observed in the damaged leg.
• Elevated resting Pi/PCr ratio strongly correlated with higher RPE (r=0.856, p<0.001).

Conclusions:

• EIMD causes a persistent disruption in muscle phosphate homeostasis.
• This sustained disturbance in resting muscle phosphate metabolism is significantly associated with heightened perceived exertion after muscle damage.
• Findings link resting muscle metabolic disturbances to increased effort perception post-damage.