Almost all trainers will have experienced a problem with individual horses, groups of horses, or sometimes even a whole yard where performance drops off for no immediately apparent reason. In human medicine we talk about chronic fatigue syndrome (CFS) which can affect both athletes and non-athletes, but in athletes we may be more likely to talk about overtraining.
In people, chronic fatigue syndrome is well recognised but often poorly understood. It typically affects young to middle aged adults with women being more commonly affected than men. It is estimated that somewhere between 150,000-250,000 people in the UK alone are affected by CFS. CFS is also referred to as simply chronic fatigue, post-viral fatigue syndrome, or myalgic encephalomyeltis (ME). The latter term describes muscle pain and central nervous system inflammation but that is not always apparent in chronic fatigue patients and so the term CFS has become more commonly used.
Dr David Marlin (European Trainer - issue 32 - Winter 2010)