eight points of contact through direct skin contact or via electrodes affi xed to the skin ($4,000 or more). Local availability of a quality device may be limited. Adherence to pretest criteria (see Box 9.2) is vital for accuracy. Because results are determined by body fl uid, testing in anything but a normally hydrated state (euhydration) will negatively aff ect the results. If suggested pretest criteria are not followed, results will not be accurate.


Box 9.2 Bioelectrical Impedance Analysis Pretest Criteria


• No food or drink for 2 hours • No caff eine use or heavy exercise for 4 hours


• No alcohol consumption for 12 hours • Maintenance of test position for 5 minutes


SKINFOLD THICKNESS


T e other measure in this category is the method that uses skinfold thickness to estimate percent fat. Within the traditional clinical techniques category, skinfold thickness measurement is readily available, fairly accurate, low cost, and requires only about 5 minutes per athlete. See Figures 9.1 through 9.7 for images of these measurements. T ere are, however, certain standards that must be met to ensure accuracy. T ree factors can aff ect the accuracy of an estimate of percent fat by skinfold thickness. First, measures


need to be taken at the correct anatomical location. Each standardized site is clearly demarcated by bony landmarks.6,16


T ese locations need to be identifi ed and the skinfold thickness measured when the athlete


is in the correct body position. In general, this is an anatomical position without twisting or bending to make the site more available to the tester. Twisting and bending may aff ect the skin and thus the size of the subsequent fold. A second contributor to accuracy is equipment. While there are a variety of calipers avail- able, inexpensive ones with thin spring mechanisms may stretch or lose recoil over time, changing the force of the caliper on the fold. T is may have a small impact on the measured size of the folds over time. For high-quality folds and research purposes, either Lange or Harpenden calipers are recommended because these tools provide a constant pressure of approximately 10 g/mm2


most accurately measured when taken by a trained technician. Training includes learning from an expert and practicing until repeated measures at the same, properly identifi ed site are consistently within 1 to 3 mm. T is is a learned skill. When all of the aforementioned criteria are met and the proper equations are utilized for the specifi c population that is being tested, estimates of percent fat from skinfold thickness are within about 3.5% of UWW.17 As indicated earlier, the cost of skinfold thickness is fairly low. It includes the cost of calipers, which


range from about $20 to $500, and any fees charged by the technician. T e time per athlete depends mainly on the number of skinfold thickness sites measured. For best results, three measures should be taken at each site, and the median value used. While measuring more sites results in higher accuracy, there may be a reasonable trade-off because measuring more sites takes more time, and “good enough” values may be achieved with fewer sites. T e number of sites should be determined by the purpose of the data. For health and across-season data, fewer sites (minimum of three) can be used. If the data are to be used for research, more sites (eg, fi ve to seven, depending on the equation) are appropriate. In terms of availability, it is easy to purchase or gain access to calipers, while the availability of a trained technician may be more diffi cult. Because of the need to measure each site three times, the skinfold thickness method is a bit more time intensive than BIA, requiring about 5 minutes per athlete. However, skinfold thickness can be measured with limited pretest considerations, improving accessibility. Caution should be exercised if those being tested are sweaty or have used lotion at the test sites, which makes the skin slippery and more diffi cult to pinch, reducing accuracy. Finally, keep in mind that if measures will be repeated at the end of the season, athletes should report in the same state, and skinfold thickness should be taken by the same trained tech- nician as in previous sessions to ensure consistency. See Box 9.3 (page 182) for skinfold analysis equations.


180 SECTION 2: SPORTS NUTRITION ASSESSMENT AND ENERGY BALANCE


. Most importantly, skinfold thickness is


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