Assessing Your Fitness Level
To help you judge whether you are fit enough to attempt a triathlon it is necessary to put the issue in context. A person might be incapable of running a marathon yet able to run a 5K in 20 minutes. That individual is definitely fit.
Fortunately for those venturing into the new territory of the triathlon, the unique demands of that sport lend themselves to quantification, at least in a general sense. You can use the following to help you decide where your position is in the fitness spectrum.
In the process of trying to measure your fitness in swimming, running, and cycling, do not go all out at any point in any of the activities. Your pace in each should be vigorous and sustained but not full speed. You will tire much too quickly if you open the throttle all the way, and you will risk injury as well.
Assuming you have some experience in athletic pursuits, you are probably in reasonably good shape to begin training for a triathlon without additional base building if you can:
Run 3 miles in less than 30 minutes without walking.
Ride a bicycle at a sustained pace for 45 to 60 minutes in relative comfort or without undue exertion.
Swim 500 to 1,000 yards in relative comfort without extended breaks.
As a test, try each of these activities. For the run, find a level surface with few turns — a mile and a half out and back would be ideal — and try to avoid running in hot weather. That will exacerbate any natural fatigue you might feel. If at any point you become uncomfortable, stop and take note of how far you have run. For example, if you run out of gas at the 2-mile mark on your run, you can figure you are about two-thirds of the way to making the grade in that discipline.
For your bike test, try to find a long stretch of road with a wide shoulder. If your community has streets with bike lanes, that would be an ideal venue for your road test. As with the run, look for a level surface.
Try to maintain an even pace without coasting. If it is feasible, have a friend or family member follow along in a car so that if your ride becomes difficult you can stop (noting your distance), load your bike, and return home without undue stress.
Swimming pools where athletes train are basically the same size, and most are 25 yards long. A mile is 1,760 yards, so to do a 1-mile swim you would have to swim from one end of the pool to the other and back again 35 times.
The swim test is less complicated than the other two. Simply get into the pool and see if you can go 500 or 1,000 yards with few or no rest breaks. It is okay to take a breather for a few seconds after each length, but to have a fair test you should try to keep the breaks to a minimum.
Don't worry if you make it only half way in one or more of the activities. Not being able to meet the standards laid out here does not mean you should scrap your plans for a triathlon. In fact, you can use the data you collect from these tests to measure your progress as you train.