When you tell someone you're doing a triathlon, you'll probably hear, "Oh dude, an Ironman? Intense!" But an Ironman is actually a specific distance of race-and the longest one.

There are actually four common triathlon distances. Before you can jump head first into training, you have to pick which one you're looking to tackle.

That's why we got in contact with Jennifer Harrison-professional USAT Level II certified triathlon coach from the Chicago area-to break down the basics that every guy must know before signing up for a race.

"There are many different variations of triathlons, but your classic four are the sprint distant, the Olympic distance, the half Ironman (which is now called the 70.3), and the Full Ironman (also known as the 140.6)," says Harrison.

Here are the common distances of each:


Which is right for you? Here's how to decide.

Sprint Triathlon Training
If you're going to sign up for a sprint triathlon, make sure you've got at least 5 to 6 hours to spare each week for training, says Harrison. And as for actual workouts, Harrison says you'll need to make sure you're doing one or two sessions-per sport-weekly. So that means at least 2 bike workouts, 2 swims, and 2 runs per week.

Olympic Triathlon Training
As the distance increases per race, it's not as easy to ballpark the "estimated hours per week" you'll need to put in because everyone's work schedules differ. But to go into the race confidently, you'll need to be able to at least swim 1 mile in open water, bike at least 40 to 50 miles on the bike, and complete a 12-mile run, says Harrison. (Not back-to-back.) And to give you an idea on what your longest workout will look like, Harrison says it typically looks something like this: A back-to-back workout (often called a 'double' or a 'brick'), consisting of a 40- to 50-mile bike ride, followed by a 10- to 12-mile run.

Half Ironman Triathlon Training
With the longer races, the only major change you'll notice from Olympic distance plan is when the actual training takes place, says Harrison. Your schedule Monday through Friday stays pretty much the same, but you'll have a much heavier training load on the weekend. Harrison says your typical weekend will look like this: A long bike ride on Saturday-50 to 60 miles-followed by a transition run-an easy 20-minute run done directly after your ride. (Total time: About 4 hours, depending on how fast you bike.) Then you'll hit your long run on Sunday, which is usually about 15 to 16 miles long. (That's about 2.5 hours at a 10-minute-per-mile pace.)

Full Ironman Triathlon Training
The Ironman routine works similar to the half Ironman training, except your distances are longer. If this is your first Ironman, it's always a good idea to squeeze in a simulation workout when you're at the peak of your training, says Harrison. This means you'll complete an hour-long swim, followed by a 100-mile ride, and topped off with a 8 to 9 mile run. And this counts as your longest workout because you're hitting all three components in one day.

So when do you know you're ready to advance to the next level? Harrison's advice is simple: Start at the bottom and work your way up. Once you've got at least one sprint under your belt, you'll have the experience to know whether or not you'll enjoy climbing up to the next distance, says Harrison. Then move on to Olympic, half Ironman, and-as long as you have plenty of time and no nagging injuries-the Ironman.