Yes. If he is experiencing pain. When we (works for horses, too) are in pain, our heart rate increases. When my non-verbal kids have had surgery and are hooked to a pulse oxymeter, onte way to detern=mine how much pain they are experiencing is to read their heart rate.
Some examples. I don't always use a heart monitor on training rides, but I did have it in place one morning when I went out on Hunter. His heart rate was elevated and I thought he felt a little "off". He had run a stick about the size of a piece of #2 pencil up beside his frog. My friend's horse stepped in a hole on an endurance ride and she got off and walked him in. His heart rate was quite elevated and the vet determined that he was either tying up or about to colic. I'm sorry - my friend was so upset I can't remember what the diagnosis was. Again, elevated heart rate associated with pain. Daughter Abby walked ten miles with her horse two weeks ago when an old pasture injury flared up, again, elevated heart rate. Abby's was probably a little elevated too. The trrick here, hwoever, is that you have to know your horse enough to know what "normal" is. You can't just take his pulse and assume pain. Nancy
