Who is it suitable for and what level of fitness/ability will you need?
This race distance can take the fastest athletes around 7.5 hours, but most races have a cut-off of 17 hours. The biggest limiting factor is how much time you can dedicate to training. You must be cautious stepping up to this distance if you have previously struggled with injuries.
How many training hours do you need and how will it impact your life?
Because of the sheer distances involved, you need to allocate occasional ‘big weekends’. This can impact family life. You should discuss these goals with those closest to you. Most people stepping up to long-course training must allocate 1012hrs per week. You must find the time to do the important big sessions. These will vary through the season but could be century (5-7hr) rides and longer runs (~2 hours). Allocate six to eight months.
How should you split your training between the disciplines?
You must consider how close to the cutoffs you may be. You might have to be strategic on the swim and the bike to give yourself the best chance to get to the start of the marathon. The cut-offs are usually at 2:20hrs for the swim and 10:30hrs for the bike. For many people, the marathon becomes less of a run and more of a shuffle. Strength and conditioning, focusing on posture and core strength, can help stave off injury. You should have one rest day a week with bigger training sessions at weekends (or big scheduled weekends). You can do your shorter and more intensive sessions throughout the week. Aim to do 2-3 swim sessions, two bikes, and two runs on the weekdays and a longer bike and run at the weekend.
What kit will you need and how much?
You will need a wetsuit as all iron events are open water, goggles, a road bike and trainers. Unlike other distances, you may not choose to use a tri-suit, favouring comfort over speed. Many people ride in cycling kit and change into running gear in the second transition. Nutrition is critical. Many races will have aid stations with course nutrition, but you can plan to use your own fuel and work out how to carry it or rely on the aid stations.
Top long-distance tip
You don’t need to do a marathon before your long-course race, as it will usually take a lot of time out of your training. A middle-distance event a few weeks before your race is better preparation.