Spin your wheels.Your bike is powered by your legs and core, which means your upper body should be relaxed and motionless as your lower half does the work. Try not to hold tension up top.
"Most beginners fall in love with one gear and don't shift as often as they should," says Jonathan Cane, head coach for City Coach Multisport in New York City. You want less resistance while going uphill, so shift down into a lower gear (your legs will spin faster and with less effort) to help you over a climb. Do the same whenever you come to a complete stop—starting again will feel 10 times easier in a low gear.
On flat or downhill terrain, shift up to a harder gear to add resistance so you're not just coasting but powering through.
More: How to Make Bike Shifting Work for You
Pedal evenly. A good pedal stroke should be about pulling as much as pushing—a complete circle of power and efficiency. And the smoothness will help your entire form: "If you have a perfectly round pedal stroke, you'll notice your hips, shoulders, and torso are stationary," says Cane.
If the last bike you rode was pink and had a basket on the front, start by taking a spin class or riding a stationary bike at your gym for 30 minutes. Do that two or three times a week to remind your muscles how to pedal before hitting the road. Once you're used to the gym bike, hop on a road bike twice a week for 30 minutes (to start). Just don't forget to vary your terrain—especially if you're prepping for a hilly racecourse.
More: 3 Drills to Practice Pedal Efficiency
Because running is the last leg of the race, your training goal is to build muscle endurance so you'll be able to finish strong when you're spent from swimming and biking. "Since you have to bang out only a few miles on race day, your running training focuses on boosting your body's VO2 max, or its efficiency in using oxygen, to get you through all three legs," says McCall. "And the best way to do that is by running shorter distances at higher intensities. In other words, intervals."
Shorten your stride.
Reducing your stride lessens the impact on your body, which cuts your injury risk and also keeps your feet happy because they're spending less time on the ground. Count the number of steps you take per minute and aim for 180 (or three steps per second) as your goal.
Run relaxed. Bend your elbows to form 90-degree angles and make sure your fists aren't clenched. Keep your jaw loose and your shoulders down. During easy runs, you should be able to carry on a conversation. If you can't, slow down.
More: The Keys to Flawless Running Technique
Start the first month with 20-minute runs twice a week, increasing time or distance by no more than 10 percent each week. Smacks of slacking off? You're really not: Thanks to your bike and swim cardio, 20 minutes is all you need right now to stay fit, says Shepley. Adding two-minute speed intervals will strengthen your legs and build the power you'll need to finish strong on race day.
Before you dash, warm up your running muscles with the three plyometrics moves below. Do each one for 10 to 15 steps, rest for 30 seconds, and repeat once.
Walking lunges: Step forward with your right foot and lower your body until both knees are bent 90 degrees, keeping your right knee behind your toes. Push off your front foot and switch legs, moving forward.
Butt kicks: Run forward, kicking your feet directly behind your body so that your heels touch your butt.
Bounding: Run with an exaggerated stride length, lifting your front knee high with each bound.
More: 5 Exercises to Improve Running Mechanics