Muscle-related disorders are not only associated with the muscles themselves but also influenced by upstream factors and, in turn, affect downstream systems. Muscles serve as a hub, so when we elaborate on indications, we center around this hub. These conditions may either be disorders of the muscles themselves, those caused by upstream factors, or downstream issues triggered by muscular problems. Upstream disorders are referred to as pre-muscular diseases—for example, ankylosing spondylitis and rheumatoid arthritis fall into this category. These autoimmune diseases first affect the muscles, keeping them in a state of pathological tension over the long term, which consequently leads to changes in bodily function. Downstream disorders are called post-muscular diseases—most cases of local numbness, cold sensations, and headaches, for instance, belong here, as many of these symptoms are caused by affected muscles.

Classifying all indications into pre-muscular diseases, muscular disorders themselves, and post-muscular diseases is an exploratory approach first introduced in the 2016 publication Foundation of Fu's Subcutaneous Needling Medicine, which has been widely recognized by practitioners of Fu's Subcutaneous Needling. In this book, we continue to adopt this classification method to help readers clarify their understanding of the role and position of muscles in the occurrence and development of diseases.

However, this classification is only a general division and may not always be definitive. Sometimes it is difficult to define using objective criteria. For example, chronic dry cough is mostly a muscular disorder itself, but in some cases, it can be a pre-muscular disease—since chronic infectious lesions or allergic conditions can also cause it, although the incidence is low. We ask readers to carefully reflect on and flexibly interpret this classification while reading.

This chapter focuses on pre-muscular diseases. The characteristics of pre-muscular diseases are as follows:

A. They are all caused by other reasons or underlying diseases;

B. Such conditions have a root cause—if the root cause is not eliminated, even if symptoms subside temporarily, recurrence is likely (e.g., allergic asthma);

C. They often exhibit a ceiling effect—symptoms can be improved, but excessive expectations (such as complete cure) should be avoided. For example, in the treatment of Parkinson's disease and intractable facial paralysis, achieving effectiveness (which is already quite challenging) is feasible, but a complete cure is difficult.