5 surprising facts about getting into shape, according to a professional trainer

Spring seems to have come early in much of the world, and that's motivating many people to go outside and get back in shape.

Training for a competition to get fit - a triathlon, 10K, mud-and-obstacle run, or something else fun - is an excellent way to stay motivated.

But if it's your first time preparing for that kind of physical challenge, you're likely to learn a few unexpected things along the way.

Business Insider spoke with Dan Arnett, a professional triathlon coach, to see what surprises people encounter while getting into shape. Here are his top five.