Eccentric exercise prior to hindlimb unloading attenuated reloading muscle damage in rats

Area of Science:

• Skeletal muscle physiology
• Exercise-induced muscle damage
• Disuse atrophy and recovery

Background:

• Skeletal muscles reloaded after hindlimb unloading (HU) are susceptible to injury.
• Muscle damage from HU and reloading resembles damage from eccentric exercise (EE).
• Prior EE conditioning protects against subsequent EE-induced muscle damage.

Purpose of the Study:

• To investigate if prior eccentric exercise (EE) can attenuate muscle damage.
• To evaluate the effects of EE before hindlimb unloading (HU) and reloading.
• To assess damage in rat soleus muscles (SOL) after HU and reloading.

Main Methods:

• Four groups of Sprague Dawley rats were used: EEHUR, HUR, EE, and CON.
• Animals underwent a 2-week eccentric exercise protocol (5 days/week).
• Following exercise, rats were subjected to 7 days of hindlimb unloading and subsequent reloading.

Main Results:

• The hindlimb unloading + reloading (HUR) group showed significantly higher myofibrillar damage.
• Glucose-6-phosphate dehydrogenase activity, an indicator of muscle damage, was elevated in the HUR group.
• Prior eccentric exercise (EE) appeared to reduce muscle damage post-HU and reloading.

Conclusions:

• Eccentric exercise prior to hindlimb unloading and reloading demonstrated a protective effect.
• EE may be a viable strategy to minimize muscle damage and recovery time.
• Findings are relevant for individuals experiencing muscle damage after bed rest or spaceflight.