"Junk miles" have often been given a bad name. If you are an aspiring triathlete, you will need to put in some time to get better and that includes "junk miles". Most age group triathletes, even competitive ones don't do enough miles to compete at their highest possible level. Life and responsibilities take priority and that is completely understandable since it is not ones chosen profession.
Anyone that is new to the sport is able to make quick gains because they are increasing time and distance in one, two or even three sports and the effect on improving endurance is immediately noticeable. However, after the initial months̶—and then years—of training have transpired anathlete will eventually reach a plateau. After that, most athletes need to be doing more. That is when the real work to get better actually begins.
We are each an "an experiment of one." Myy knowledge and experience gained over the past 30 years has proven to me that "racing" a high quality half (70.3) or Ironman distance (140.6) event requires as much 15-20 hours a week to be competitive on a high level. To consider being among those athletes battling for a slot to IM Kona you may be doing somewhere in the area of 25-30 hours during a big block period of training. Realistically, that probably means 10,000yd in the pool with 15,000yd or so on some occasions. This is 3 to 4 sessions weekly. Since cycling makes up most of the event (if you run the run) you are looking at 200-250 (or more) miles on the bike and if you plan it right (take some Wednesday vacation days) that would be include mid-week and weekend long rides. You can add another 100 "junk miles" in somewhere else during the week for a 300 total if it's possible. This kind of volume will give you conditioning and most importantly the confidence that you will be ready for a long day of racing.
The run is another story. I consider 40 miles as a baseline and more is better except that more usually brings on injury. This can be accomplished with a long Brick (following your Wednesday long ride) and a long weekend run and another one or two shorter runs. The fine line of balancing injury and further conditioning is usually the "junk miles". Hence, more is better…until it isn’t. Yes, one more long run on tired legs may mean the difference in finishing the race strong. Or string a few of these in a row and you may end up hurt and not get to the starting line at all. Because we are an experiment of one, what someone else does may not be what works for you. However if you don’t reach that point on the edge, you just won't ever know.
This all seems very basic and self-explanatory for a race that will take somewhere between 8 and 12 hours. Do this for 3-5 years and you will be ready to train for racing an IM. Then all you need to do is a quality 12-16 week buildup and you will be ready to do well at IM. There may be a few people with the talent to get away with less, but most can't. If you are able to do the other things right like massage, nutrition, sleep, work or life issues (no spouse/sig other or children) and the disposable income you will be even better. Combine all that just right and you could be up front for an Age Group spot on the podium in Kona!
If you break down your week with another view of 20 hours, that may consist of 10-12 hours riding (say you ride an average of 20mph)that gives the magic 200. If you can add 5 hours of running at 7-8 mph, you’re at 35-40 miles and then another 4-5 hours of swimming (with intervals) gets you in at 15,000. Those miles are hard to sustain with a normal life that includes work, family, children, housework and so on. The real killer is having those as averages for 8-10 weeks prior to the taper for Ironman. Sure, you can surge and get a 300 mile week on the bike with a Monday holiday, but if the next 2 weeks are at 125 miles then the 3 week average is under 200—and that is short of the goal. For amateurs, it becomes a great big compromise and pressure to get in the miles needed to do well. If you don't get adequate training, or worse, you try to sustain the training without a solid winter base, or some overtime at work then fatigue, slop, and/or injury will inevitably show up.
Everyone's view of the details is slightly different, but no matter what, it is going to take time, dedication, sacrifice and perseverance. All those things most people already know, they just don't realize how much of all of it is really required. You can get by with a 75% effort and finish. The more you do the better you will get…up to reaching the fine line of doing the most you can, to be the best you can be (and then nothing more because everything over that breaks you back down). So be an experiment of one for a decade or so and see where it takes you.
About the author: Doug Marocco is a nine-time (9X) Hawaii Ironman finisher with a PR of 9:23:04. In addition, he has been a USAT All-American for the past two decades while winning two (2X) National Age-Group titles and four (4X) Military National Championships among his 47 overall wins. An accomplished Marathon runner, Marocco has a PR of 2:33 in his 37 finishes at the 26.2 mile distance.