Why muscle atrophy (wastage) and hypertrophy (growth) is commonly paired...

A definition of either tissue type...

• Hypertrophy: The increase in muscle size resultant from growth of thousands of individual muscle fibres.

• Atrophy: The reduction in muscle size due to disuse of specific muscles which subsequently reduces strength.

Typically there are two types of atrophy, disuse and neurogenic. Disuse atrophy typically takes several weeks to a few months to become apparent. If the animal is completley non-weight bearing on a specific limb, this can often quicken the process of atrophy with signs visible as fast as 10-14 days. Alternatively, neurogenic atrophy typically effects more than one muscle and usually a group of muscles such as the triceps of pectoral as the nerve which send signals to contract this group of muscles is impaired. Therefore, muscles do not contract as they usually would and therefore incorrect recruitment contributes to the atrophy.

Hypertrophy on the other hand occurs when the body builds muscle in response to small controlled muscle damage induced by exercise, this process is required in order to build muscle and strength. Myofibrillar is one type of hypertrophy which involves increasing the number and size of muscle fibres which influence muscle strength and density. Whilst, sarcoplasmic hypertrophy leads to an increase in the volume of sarcoplasm, which is fluid within the muscle cell which aids in energy production for muscle and works to increase muscle size.

These tissue types are commonly seen alongside each other, for example if the animal is non-weight bearing in the left forelimb you will get atrophy due to disuse, whereas, the opposite limb (in this scenario the right forelimb) will be overworked to allow for the animal to remain upright and balance, therefore hypertrophy is likely to occur.

Both atrophy and hypertrophy can have negative effects on your animal musculoskeletal systems and can contribute to aysmetrical muscle coverage. Atrophy can lead to weakness and increase joint instability, thereby increasing injury risk. Whereas, hypertrophy can induce muscle fatigue and restricted joitn range of motion. However, it is important that a small controlled amount of hypertrophy can be desirable to help improve an animals strength and performance. If this is not rectified through treatment, injury risk hightens due to a build up of compensations. Locomotion (movement) is one of the first elements your animal will alter and overtime this can lead to further pain and reduced performance which ultimately ends up in a viscous cycle. It is therefore important to interrupt this cycle as more often than not this cycle leads to more severe issues than what had occurred initially.