The training for the marathon or triathlon is essential to actually completing the event.
If you’ve never run a marathon before you will need to build up your fitness before the race. Most runners try to reach about 20-22 miles on their longest weekly run and a total of about 37 miles per week. However there is a wide variation in practice and in recommendations. Elite runners will have much higher weekly mileage.
For marathon or triathlon, training programs should last a minimum of five or six months, with a gradual increase (every two weeks) in the distance run and finally a decrease or taper (1 to 3 weeks) for recovery. Most athletes recommend a weekly increase in mileage of no more than 10% to prevent injury and allow the body to adapt to new stresses.
During the last two or three weeks athletes typically reduce their weekly training by as much as 50%-75% to allow their bodies to recover and be well rested for the full out effort on the day. Many athletes also "carbo-load" (increase carbohydrate intake) during the week before to allow their bodies to store more glycogen.
It is also wise to feed in an element of strength work and cross training into exercise routines. This strengthens the core muscles while also using more of a variety of muscles, which can help prevent over use injuries.
Triathletes tend to have whole body muscular development thanks to their training. However they do need to adjust their technique during each discipline in a way that solo event competitors do not. For example during the swim leg triathletes will use their legs less vigorously and preserve them for the cycle and run to follow. During the cycle leg triathletes will cycle with a high cadence, particularly near the end, to keep the muscles loose and flexible for running. In the run leg athletes, particularly novices, may discover their legs are quite tired or heavy as they are already tired from the previous two events. Most athletes train for this phenomenon doing transition workouts; workouts using two disciplines back-to-back.
The key in training is to build a program that works with your lifestyle and to understand matters of nutrition, running form and heart rate training. If you need gear such as a bicycle you should learn how to maintain it and insure it is in best working order.
Gear Requirements/Packing lists
You will need to take all your own sports gear to the race, unless specified otherwise by race organizers. This usually means your own running shoes, swimming costumes, swimming goggles, bike pants, bike gloves, bicycle, helmet and so on. Make sure you pack all the tools and spares you need for fixing your bike as well. In some events you are also required to take your own bedding, food and other camping gear and to carry it. Some experimentation will be required for these races to insure you can manage the equipment you have. You should also train carrying these things.
It is a good idea to pack the items you need for the competition into your carry-on luggage to insure baggage-handling errors on arrival won’t affect your chances of entering the race.