Ultrastructural Characteristics of Slow and fast twitch Muscle Fibers of Rats after a Forced Swimming Cycle against a Background of Introduction of Green Tea Extract and Ammonium Salts

Finding and studying the mechanisms of action of substances of natural origin that would reduce fatigue and restore the performance of skeletal muscles under extreme physical loads are very important tasks of sports physiology and medicine. A comparison of the effects of decaffeinated green tea extract (GTE) and ammonium chloride (AChl), which we previously tested separately and in combination with GTE in the forced swimming model, allowed it to be established that has a greater stimulative effect than does GTE. In the present work, on the basis of electron microscopy data, morphometric studies of m. soleus (SOL) and m. extensor digitorum longus (EDL) muscle fibers of rats were conducted after a forced swimming cycle after the effect of GTE and low doses of ammonium salts (chloride (AChl) or carbonate (ACar)). In GTE group rats, the adaptation to physical load mainly occurs due to an increase in the average area of mitochondria in SOL muscles. In AChl group rats, the adaptation is caused by an increase in the average area of mitochondria in EDL muscles, while, at the same time, the average area of transversely oriented (in relation to the cut plain) T-tubules (TTs) in these muscles decreases along with an increase in the portion of longitudinally oriented TTs, indicating muscle fiber breaks. The combined action of AChl and GTE provides an additive functional effect due to an increase in the average area and volumetric density of mitochondria in EDL muscles and average area of TTs in SOL and EDL muscles, as well as their amount in EDL muscles. In ACar group rats, the functional effect is caused by an increase in the average area of TTs in EDL muscles and their amount in SOL muscles. At the same time, the portion of longitudinal TTs in EDL muscles (and therefore muscle fiber breaks) increases. In the group of combined ACar and GTE effect, changes in mitochondrial apparatus were detected in slow twitch, but especially in fast twitch muscles, as well as an increase in the area of TTs in SOL muscles. Analysis of ultrastructural characteristics indicates that the efficiency of preparations is mainly caused by adaptive changes of TTs and fast twitch muscle mitochondria, but it increases with the involvement of slow twitch muscle fibers in structural and functional adaptation to extreme physical load.