Traveling two days before race day generally works well and is recommended for most races. But the sooner you can arrive the better when race heat or humidity is greater than where you train or the altitude is 2,000 feet (600m) above where you live. Also, if you are traveling east through two or more time zones or west through more than four you may need to arrive sooner than two days before the race to adjust to the clock change.
It takes about 10 to 14 days of exposure to a much hotter environment than you are used to for complete adaptation to occur. A difference of 10 degrees Fahrenheit (4C), especially when the race temperature is above 80F (25C), is probably enough to cause a significant reduction in performance. For example, in Kona, Hawaii the temperature and humidity are typically both very high for the Hawaiian Ironman World Championship Triathlon. The sooner you can arrive, the better adapted you will be on race day, even if this is only a week early. For such a race do all of your Race-week block workouts in the heat of the day. You do not need to turn off the air conditioning in your hotel room, however. This will not improve your readiness for the heat and only add to the misery of your rest and relaxation time. Cool off as soon as the workout is over each day.
As with heat and humidity, adaptation to altitude begins as soon as you arrive at the race venue. So getting there even a couple of days early is beneficial. This is contrary to the previously assumed method of arriving as close to race day as possible or else getting there two weeks or more early. Recent research has suggested this as-close-to-race-time-as-possible method is probably not correct. The body begins to adapt to the new altitude within hours of arrival. Still, the earlier you can get to the race altitude the better your performance is likely to be on race day.
Regardless of when you arrive at a high-altitude race you can expect your race-day performance to be compromised relative to a lower altitude. It takes about two to four weeks for a significant adaptation to occur. For every 1,000 feet (300m) above where you live expect about a one-percent slowing of race time if not adapted, less than that if adapted. For example, if you live at sea level and your race is in Boulder, Colorado, at roughly 5,000 feet (1500m) and you arrive two days before the race you can expect to race roughly five percent slower than you would back home.
Traveling through several time zones is physically stressful as the body doesn’t like quick changes in sleeping and eating routines. This is regulated to a great extent by sunrises and sunsets and requires a few days to adjust. While adjusting to the new time zone you may feel lethargic and sleepy withthis new stress. Traveling east is more stressful than traveling west. For every time zone you pass through when going east allow one day of time-zone adjustment before your race. So four time zones to the east would require arriving four days early to fully adjust. When flying west you can get by with only a half day for every time zone. In this case, arriving two days before your race when traveling through four time zones should do it. This adjusting may start in the days before you leave home by going to bed and getting up earlier or later, depending on the time zone you will be traveling to. By doing this you can reduce some of the time adjustment at the race venue just to get your body on the new schedule. Even a one-hour shift before the trip can save you the stress of one or two time zones on arrival.