Enhanced protein breakdown after eccentric exercise in young and older men.

Area of Science:

• Exercise Physiology
• Protein Metabolism
• Aging Research

Background:

• Eccentric exercise, characterized by muscle lengthening under load, is known to induce muscle damage and adaptations.
• Understanding the impact of aging on protein metabolism responses to exercise is crucial for optimizing training and recovery strategies.

Purpose of the Study:

• To compare the effects of a single bout of eccentric exercise on whole body protein metabolism in young and older untrained men.
• To investigate age-related differences in muscle protein breakdown following eccentric exercise.

Main Methods:

• Five young and five older untrained men performed 45 minutes of eccentric cycling exercise.
• A eucaloric diet with 1.5 g/kg/day protein was consumed pre- and post-exercise.
• Leucine metabolism was assessed using intravenous L-[1-13C]leucine infusion before, immediately after, and 10 days post-exercise.
• Urinary 3-methylhistidine excretion was measured as an indicator of myofibrillar protein breakdown.

Main Results:

• Leucine flux and oxidation increased immediately post-exercise and remained elevated 10 days later, with no significant age-related differences.
• Urinary 3-methylhistidine excretion increased post-exercise in both groups, but was significantly higher and sustained longer in older men.
• Older men exhibited a 37% greater increase in 3-methylhistidine excretion compared to young men.

Conclusions:

• Eccentric exercise induces a comparable increase in whole body protein breakdown in young and older men.
• Myofibrillar proteolysis appears to contribute more significantly to whole body protein breakdown in older men following eccentric exercise.
• These findings highlight potential age-related differences in muscle protein turnover dynamics after eccentric exercise.