[Neuromuscular system and aging: involutions and implications]

Area of Science:

• Muscle physiology
• Aging research
• Exercise science

Context:

• Aging leads to decreased muscle fibers and motor unit functionality, impacting protein synthesis and satellite cell activity.
• Reduced anabolic hormone production and increased protein degradation factors exacerbate age-related muscle loss.
• Specific myosin heavy chain (MHC) isoforms shift towards slower types with age, affecting muscle performance.

Purpose:

• To investigate the effects of strength and aerobic training on muscle adaptation in aging humans.
• To analyze changes in myosin heavy chain (MHC) isoform expression following exercise interventions.
• To understand the molecular mechanisms underlying exercise-induced muscle hypertrophy and phenotype stabilization in older adults.

Summary:

• Strength training promotes muscle hypertrophy in older adults, primarily through myosin heavy chain (MHC) protein synthesis, though it increases MHC-I (slow) and decreases MHC-II (fast) gene transcription.
• While strength training cannot reverse the age-related shift to slower muscle fiber types, it can stabilize the muscular phenotype and reduce hybrid fiber proportions.
• Aerobic training increases mRNA synthesis for oxidative metabolism-related MHC isoforms (MHC-I, MHC-IIa) while decreasing MHC-IIx transcription.

Impact:

• Strength training counteracts detrimental aging effects on muscle by inducing hypertrophy and increasing anabolic hormone production.
• Exercise interventions can stabilize muscle phenotype and mitigate age-related functional decline.
• Findings provide insights into targeted exercise strategies for optimizing muscle health in aging populations.