The Day and Night Before
You followed your training schedule and did virtually nothing two days before your triathlon. With one day to go, you have permission to move about, but you still won't be doing very much. You are saving your energy for race day.
The day before the triathlon, do some light exercise. You can hop on your bicycle for a fifteen-minute ride with a couple of quick accelerations. Just spin a bit, but don't strain yourself. Likewise, hit the road for a short run at an easy pace, perhaps five minutes.
If you are already at the race site, do your light workouts at the venue if it's convenient. Your objective is to stay loose. If you do nothing, you could become sluggish.
If you are traveling to your triathlon the day before and leaving in the morning for the airport, fit in what exercising you can before you leave. If it's not convenient, plan on doing your light exercise once you arrive and after you have picked up your race packet and checked in at your hotel.
Don't Forget the Water
Maintaining adequate hydration is an ongoing need, and you should keep it up, even increase the effort the day before your triathlon. The day before, you should take in enough fluid to keep your urine clear.
If the idea of drinking so much water is a turnoff, mix in a sports drink for variety. Whatever you have to do, adequate hydration is a must, especially if race-day temperatures will be elevated.
Eat for Success
Lots of races have prerace meals for “carbo loading,” frequently featuring mounds of pasta. Be careful. It's a mistake to take in a huge meal the night before your race. For one thing, your body has a limit to the amount of carbs that can be stored as glycogen. For another, remember that your first event will be a swim. Do you want to hit the water feeling weighed down by a massive dinner the night before? A big meal can also cause stomach upset and other gastric issues.
Take a couple of energy bars and eat small portions during the day before your race. At dinnertime, have a light meal as early as you can before turning in for the night.
If you can, it's best to do your light day-before workouts at about the same time your triathlon will start. If that doesn't work, do it when you can. Some light exercise is better than none, no matter when it happens.
If you're on the road, try to get back to the hotel room early so that you can relax with a book or the television prior to turning out the lights early. You will have lots of pent-up energy and you will be nervous about the race, and that might interfere with your sleep. Don't fret if you don't sleep as well as you would like. If you got adequate rest the night before, you will be okay. Instead of counting sheep, picture yourself crossing the finish line feeling great and deservedly proud.