Details on the physical description of the Doctor in The Canterbury Tales are extremely sparse, at least within the confines of the General Prologue.  Most of what is said of the Doctor pertains to his practice. For instance, it is suggested that he is gifted at diagnosing illnesses, and there is a reference to his interest in astronomy.  We can deduce from the very limited information on his physical characteristics, however, that he is in very good physical condition, due in no small part to his proclivity for maintaining a healthy diet, as acknowledged in the following passage:

Of his diet measurable was he moderate
For it was of no superfluity excess
But of great nourishing and digestible.

That is it for physical characteristics, other than his clothing, which is described as follows:

In sanguine and in perse he clad was all In red & blue
Linèd with taffeta and with sendall,

As noted, most of the discussion in the General Prologue regarding the Doctor addresses this particular character's medical abilities and the aforementioned interest in astronomy.

In The General Prologue of The Canterbury Tales, the narrator gives a very long description of the Doctour of Phisik's (Doctor of Medicine's) credentials and accomplishments but gives only a brief physical description. No mode of transportation is mentioned nor any weapons or other accouterments. All we know of the Doctor is that his clothing is of blue and scarlet and lined with taffeta and sendal. Taffeta is a delicate, crisp silk fabric that lusterously shines and makes a rustling sound in response to movement. Sendal is a thin, soft silk fabric of Medieval fashion. He carried gold with him, earned as fees during the "pestilence," and he was careful about his expenditures. The gold was valuable to the Doctor because it was used medicinally in restorative cordials. (It is interesting to note that gold and silver are again being recommended as health aids.)