Although enemas were employed over many years within the fasting fraternity and esp' so in early Hygiene, it was eventually discovered that they were in fact very enervating to the individuals who had them during their fast. They can also be a painful experience for many even if carried out correctly.
Fasting is a way of recuperating energy, so any "forcing measure" such as enemas are counterproductive to the aims of the body in healing and cleansing.
Dr Charles Page MD commented that during a fast "the bowels will take care of themselves", as indeed they will after breaking the fast.