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Skeletal Muscle Fibre Types :

Most textbooks on exercise physiology classify the skeletal muscle fibres into three basic types. However, recent research suggests that there might be several additional muscle fibre types present. For the purpose of this blog, we shall focus only on the prevalent three muscle fibre types, namely :

Most muscles have all the three muscle types in varying proportion. The soleus muscle, thus consists not just of Type I muscle fibres. Instead, it has Type I as the predominant muscle fibre type but also includes Type IIA and Type IIX in lower proportion.

Type I muscle fibres facilitate endurance activities and are found in abundance in endurance athletes. In contrast, Type IIX fibres are found in relative abundance in sprint and power athletes. Type IIA fibres are essentially a hybrid of Type I and Type IIX fibres.

Training Effects on Skeletal Muscle :

The following three types of training can bring about physiological changes in skeletal muscles :

Aerobic (Endurance)Training :

With endurance training the Type I muscle fibres are challenged predominantly.

Although the percentage of Type I and Type IIX fibres does not change with regular endurance training, but it may cause Type IIX fibres to take on more characteristics of Type IIA fibres.

Other significant effects of endurance training are :

Anaerobic (Sprint) Training :

Benefits of regular anaerobic training are as follows :

Resistance Training

Following are the benefits of regular resistance training (3 to 5 sessions per week for at least 8 weeks) :

In the upcoming blogs we shall briefly checkout the various Endurance tests and assessments.

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