Endurance athletes typically determine their ideal body weight, which, in their case is better termed optimal performance weight, through exercise performance; a good proxy for general health. Through experience in training and competition, endurance athletes learn their optimal performance weight, or the body weight at which they perform best. A recent scientific survey of 3,000 endurance athletes by researchers at St. Cloud State University found that more than 90 percent of respondents were able to identify a precise optimal performance weight. Fluctuations below and (more often) above this optimal performance weight over the course of the year were found to be normal, but the normal range was small: fewer than 10 pounds in the majority of those surveyed.
By paying attention to how your body performs at various weights throughout the year you will gain knowledge of when your weight is on track or off-track. A body weight that is higher than it should be at any given time of year could be an indication that you are eating more than you should be. The other possibility is that you are training less than normal. If you’re confident that under-training is not the problem, then experiment with a slight reduction in your eating and watch how it affects your weight.
Monitoring your body composition, or body fat percentage, is a useful supplement to monitoring your body weight. As with weighing, by stepping on a body fat scale such as the Tanita once a week throughout the year you will learn what your body fat percentage should be. Your optimal body fat percentage is that which is associated with your best training and race performances. An increase in your body fat percentage could indicate that you need to adjust your food intake to better match your current training demands.
Note, however, that it could indicate the very opposite. Some research has shown than when endurance athletes (and particularly female athletes) under-eat, their metabolism slows down to conserve energy and as a result they gain body fat and sometimes also lose muscle. So when you note an abnormal increase in your body fat level you may need to experiment to determine whether you are eating too little or too much.
The most precise way to determine your optimal performance weight is to create a graph that plots your body weight against your performance. The x-axis will define a range of body weights that’s a little broader than any fluctuations you’re likely to experience throughout the year. The y-axis will define a range of average speeds from a recurring test workout that’s a little broader than your performance fluctuations are likely to be over the course of a year. Once every four weeks, step on a scale and note your weight. Also once every four weeks, on the same day you weight yourself, perform a test workout that provides a good indicator of your race-specific fitness. For example, if you’re runner, go to the track and do a 10K time trial at 95 percent effort. Now calculate your average speed.
Create a data point on the graph that represents your speed and weight on each test day. After a few points have been plotted you will begin to notice a clear pattern. It is likely that you will achieve your best performance at your lowest body weight. In any case, the body weight at which you achieve your best performance is your optimal performance weight.
For the best results, you should also plot your performance against your body fat percentage. This is because you can reach any given body weight at more than one body fat percentage. You will probably find that the lower your body fat percentage is, the better you perform. This is important, because if you only look at body weight, and approach body weight management with a “lighter is better” mentality, you might try to slim down in ways that cause you to lose muscle and therefore put you at your optimal body weight at a greater than optimal body fat percentage. As a result, you will underperform at this body weight. So tracking your body fat percentage along with your body weight can function as a check against making this mistake. Yes, you want to be light, but you don’t want to be light at all costs. You want to be light and lean.
Tracking your body fat percentage is as easy as doing your weigh-ins on a body fat scale such as the Tanita Ironman. Every four weeks, plot your body fat percentage against your test workout average velocity and superimpose this graph over our body weight-average speed graph to see how they match up. They should match up closely, but in any case you will want to use both the body weight and the body fat percentage associated with your best performances as targets to pursue going forward.
Tony Troccoli has been a certified USA Triathlon and USA cycling since 2001. Tony has competed in nearly 20 Ironman events including Kona and coaches locally in the Southern California area and on-line nationwide. Thousands of athletes have had successful training and racing experiences using Tony’s pre-built, easy-to-follow training programs. Tony is also a F.I.S.T certified bike fitter and soon to be Certified Total Immersion instructor. Contact Tony at email@example.com.