Exercise Induces Different Molecular Responses in Trained and Untrained Human Muscle

Area of Science:

• Exercise Physiology
• Molecular Biology
• Muscle Adaptation

Background:

• Human skeletal muscle is believed to have increased responsiveness to exercise stimuli due to prior training, a phenomenon termed "muscle memory."
• Understanding the molecular basis of muscle memory is crucial for optimizing training and rehabilitation strategies.

Purpose of the Study:

• To determine if prior strength training history affects basal and exercise-induced gene expression and cell signaling in human skeletal muscle.
• To investigate the molecular underpinnings of muscle memory following a period of detraining.

Main Methods:

• 19 participants underwent 10 weeks of unilateral leg strength training, followed by 20 weeks of detraining.
• An acute resistance exercise bout was performed on both legs, with muscle biopsies collected at rest and post-exercise.
• Analysis included gene expression (mRNA) and protein phosphorylation of key signaling molecules.

Main Results:

• The previously trained leg (memory leg) exhibited higher phosphorylation of AMPK, eEF2, and 4E-BP1 compared to the untrained leg.
• Basal PGC1α mRNA was lower in the memory leg, but it showed an increase in PGC1α-ex1a transcripts post-exercise, unlike the control leg.
• Differential expression of myogenesis-related genes (SETD3, MYOD1, MYOG) and SPRYD7 was observed between legs, with some sex-specific effects.

Conclusions:

• Previous resistance training history influences key regulatory genes and proteins involved in muscle adaptation.
• These findings provide molecular evidence supporting the concept of muscle memory, suggesting lasting changes in skeletal muscle signaling pathways.
• Further research is needed to elucidate the precise mechanisms and functional significance of these molecular adaptations.