Which muscle fiber type is the best for competing in a triathlon?

slow-twitch muscle fibers

Explanation:

Marathons, ultra-running, and longer course triathlon pulls in mostly slow-twitch muscle fibers. “Type I, slow-twitch muscle fibers, are also known as aerobic muscle fibers due to their ability to create energy from oxygen, allowing them to produce force over an extended period of time

these are common warning signs of overtraining syndrome:

washed-out feeling, tired, drained, lack of energy

mild leg soreness, general aches, and pains

pain in muscles and joints

sudden drop in performance

insomnia

headaches

decreased immunity (increased number of colds, and sore throats)

decrease in training capacity/intensity

moodiness and irritability

depression

loss of enthusiasm for the sport

decreased appetite

increased incidence of injuries.

a compulsive need to exercise