Effect of eccentric versus concentric exercise training on mitochondrial function

: The effect of eccentric (ECC) versus concentric (CON) training on metabolic properties in skeletal muscle is understood poorly. We determined the responses in oxidative capacity and mitochondrial H 2 O 2 production after eccentric (ECC) versus concentric (CON) training performed at similar mechanical power. Methods : Forty‐eight rats performed 5‐ or 20‐day eccentric (ECC) or concentric (CON) training programs. Mitochondrial respiration, H 2 O 2 production, citrate synthase activity (CS), and skeletal muscle damage were assessed in gastrocnemius (GAS), soleus (SOL) and vastus intermedius (VI) muscles. Results : Maximal mitochondrial respiration improved only after 20 days of concentric (CON) training in GAS and SOL. H 2 O 2 production increased specifically after 20 days of eccentric ECC training in VI. Skeletal muscle damage occurred transiently in VI after 5 days of ECC training. Conclusions : Twenty days of ECC versus CON training performed at similar mechanical power output do not increase skeletal muscle oxidative capacities, but it elevates mitochondrial H 2 O 2 production in VI, presumably linked to transient muscle damage. Muscle Nerve 50 : 803–811, 2014