Aims: 

Aerobic exercise is associated with an increase of functional activity and metabolic demands of both locomotor and respiratory muscles. However, the effect of endurance training on the muscle may depend on its untrained oxidative capacity. The aim of this work was to compare the effects of treadmill training on citrate synthase activity (CSA) in hindlimb muscles (gastrocnemius medial head -GM, plantaris -PL, gracilis -GR, soleus -SOL) as well as in costal part of diaphragm (DIA).

Methods: 

Male Wistar rats were treadmill trained for 8 wk at 20 m/min and 50 incline. Anaerobic threshold expressed as the running speed at which lactate starts to accumulate in blood was used to evaluate systemic effect of the training. CSA was measured in whole muscle homogenates spectrophotometrically.

Results: 

In sedentary rats CSA (mmol*min-1*mg protein-1) did not differ in GM (0.210.02), PL (0.230.01) and GR (0.230.01), but was higher in SOL (0.480.01) and DIA (0.570.06). Anaerobic threshold in trained rats (30 m/ min) increased as compared to sedentary rats (15 m/min). The training also increased CSA in GM (28%) and PL (16%), but not in GR indicating less involvement of hip muscles in running exercise. As well, CSA in DIA did not change after training, but increased in high-oxidative SOL (20%). This suggests that low metabolic plasticity of diaphragm muscle is not due to its higher untrained oxidative capacity.

Conclusion: 

A non-uniform effects of endurance training on locomotor and respiratory muscles is explained by their different activity in non-exercising state. Metabolic shift in permanently active diaphragm muscle may require higher intensity or duration of exercise training. Supported by RFBR (grant 09-04-01701-a).