Answer: increased heart rate
Explanation:
A) The source is probably not valid because it is based on an opinion.
He or she that wrote it did not go into a lab and see if the resources are true its just based on what he thinks it is.
The body already produces enough protein to get by just fine. However, many people think athletes "use up" too much protein and faster than they gain it back, but that is not true because the body regulates homeostasis. I hope I helped :)