Concise Notes on Concurrent Training and Interference

Concurrent Training and Interference Effect

• Concurrent training combines resistance and endurance exercise.
• May compromise gains in muscle mass, strength, and power compared to resistance training alone.
• Endurance exercise may inhibit protein synthesis and stimulate protein breakdown.
• Molecular mechanisms and the role of training variables are not fully understood.

Molecular Basis for Training Adaptation Specificity

• Skeletal muscle adapts to exercise, with resistance and endurance training inducing distinct responses.
• Resistance training enhances muscle activation and fiber hypertrophy.
• Endurance training increases mitochondrial density and oxidative capacity.
• mTORC1 is a key mediator of resistance exercise-induced protein synthesis.
• AMPK and CaMKII are activated by endurance exercise, promoting mitochondrial biogenesis via PGC-1a.
• AMPK activation may inhibit muscle hypertrophy.
• Molecular responses are influenced by training status, age, genetics, and nutrient availability.

Molecular Basis for the Concurrent Interference Effect

• Endurance exercise induces responses that inhibit protein synthesis and stimulate protein breakdown.
• AMPK activation inhibits mTORC1, negatively regulating protein synthesis and hypertrophy.
• AMPK promotes protein degradation via the ubiquitin-proteasome and autophagy-lysosomal systems.
• eEF2K, activated by endurance exercise, inhibits muscle protein synthesis.
• REDD1, activated by metabolic stressors, inhibits mTORC1.
• SIRT1, activated by endurance exercise, negatively regulates mTORC1.

Molecular Interference in Human Skeletal Muscle

• Limited data on acute molecular responses following concurrent exercise in humans.
• Studies have not consistently shown acute interference of anabolic molecular responses.

Limitations of Existing Molecular Concurrent Training Evidence

• Limited data on direct coupling between acute molecular responses and long-term adaptations.
• Training status influences exercise-induced molecular responses.
• Nutrient availability affects adaptive responses to exercise.

Role of Concurrent Training Variables in the Interference Effect

• Within-Session Exercise Order: Resistance exercise prior to endurance exercise may mitigate negative residual effects.
• Between-Mode Recovery Length: Adequate recovery may attenuate negative residual effects from endurance exercise.
• Endurance Training Intensity: Higher-intensity endurance exercise may exacerbate acute molecular interference.
• Endurance Training Volume: Higher endurance training volume may mediate concurrent interference.
• Endurance Training Modality: Running may induce greater eccentric muscle damage compared with cycling.