Definition: In this task, you need to reverse all words of a given length in the sentence. The number of letters in a word determine its length. For example, the length of the word "apple" is 5.
Input: Sentence: 'a man stares off to the side as he is walking his bike in the middle of muddy water'. Reverse all words of length '3' in the given sentence.

a nam stares ffo to eht side as he is walking sih bike in eht middle of muddy water