Time course of glycogen accumulation after eccentric exercise.

Area of Science:

• Exercise Physiology
• Muscle Metabolism
• Sports Science

Background:

• Skeletal muscle glycogen is a crucial energy source during prolonged exercise.
• Eccentric muscle contractions, characterized by muscle lengthening under load, can cause muscle damage and alter metabolic responses.
• Understanding glycogen resynthesis after different exercise types is vital for optimizing recovery and performance.

Purpose of the Study:

• To investigate the time course of glycogen accumulation in skeletal muscle following eccentric exercise.
• To compare glycogen resynthesis rates between eccentrically exercised muscle and a non-exercised control limb.

Main Methods:

• Eight healthy men underwent exhaustive concentric cycling exercise followed by unilateral eccentric knee extensor exercise.
• Muscle biopsies were taken from the vastus lateralis of both the exercised (ECC) and control (CON) legs at various time points over 72 hours.
• Subjects consumed a controlled carbohydrate intake (7 g/kg body weight/day) during the recovery period.

Main Results:

• Immediately after exercise and at 6 hours of recovery, no significant difference in muscle glycogen content was observed between ECC and CON legs.
• At 18 hours post-exercise, the ECC leg showed significantly lower glycogen levels (15% less) compared to the CON leg.
• After 72 hours of recovery, the glycogen deficit in the ECC leg increased to 24% compared to the CON leg, despite carbohydrate consumption.

Conclusions:

• Eccentric exercise significantly impairs the rate of skeletal muscle glycogen accumulation during the initial 72 hours of recovery.
• This impaired glycogen resynthesis occurs despite adequate carbohydrate availability.
• The findings highlight a specific metabolic consequence of eccentric exercise that may impact subsequent training and performance.