Contractile properties of the diaphragm in creatine-fed rats.

1. Creatine feeding increases the oxidative capacity of type 1 skeletal muscle fibres and, in soleus muscles, consisting mainly of type 1 fibres, increases fatigue resistance. The diaphragm contains a relatively large content of type 1 fibres and respiratory muscle fatigue is a cause of respiratory failure. The aim of the present study was to determine whether creatine supplements increase fatigue resistance in the diaphragm. 2. Rats were given creatine monohydrate (2.55 g/L) in the drinking water. After 5-6 days, isometric contractile properties were measured in strips of costal diaphragm in Krebs' solution at 30 degrees C. Measurements were also made in soleus muscle strips. Values for strips from creatine-fed rats were compared with those from control rats. 3. Creatine feeding did not increase fatigue resistance and had no effect on twitch or tetanic tension or twitch kinetics in the diaphragm. Creatine increased fatigue resistance in soleus muscles, as reported previously.