BodPod Reliability and Validity: Especially in Male and Female Athletes.

A Literature Review

Research in Exercise Science

BODPOD INFORMATION AND BACKGROUND

The BODPOD is a fairly new form of body fat estimation introduced to the health and fitness world. BODPOD is a shortened term for the formally named air-displacement plethysmography. This tool for body composition estimation is called a two-compartment model, similar to hydrostatic weighing. Hydrostatic weighing is another two-compartment model that was around and used before the BODPOD’s existence. (Fields, Hunter & Goran , 2000) Also called under water weighing, hydrostatic weighing remains the gold standard for accurate measurements of body fat percentages. This can be an intimidating form of measurement because subjects are forced to be submerged underwater and exhale as much air as possible. Some Studies show that the hydrostatic method is still a more trusted means of estimation of body fat percentages and body density, while others show that their results are often times very similar. (Fields, Wilson, Gladden, Hunter, Pascoe & Goran, 2001) It is called two compartment because is measures two things, Body fat percentages (BF%) and body density (Bd), as opposed to a four compartment model which takes fat, water, minerals, and protein into account. (Sardinha, Silva & Teixeira, 2003) The BODPOD is a much cheaper and easier way to estimate BF%, which is why it is so commonly used.

These reasons along with the minimal training needed to run the machines is why more and more labs are switching over to the use of the BODPOD rather that more expensive and difficult means of estimating such as 4 compartment models, 5 compartment models and even 6 compartment models. (Sardinha, Silva & Teixeira, 2003) Another reason air-displacement is preferred is that it is so easy to administer, all one must do is enter the BODPOD with a minimal amounts of clothing and the calculations will be made. With hydrostatic weighing a person must be submerged numerous times for an accurate estimation to be calculated. Though this convenience in use does not come without a price, the BODPOD has been found in studies to be less valid and reliable when compared to other forms of body fat estimating. (Moon, Eckerson, Tobkin, Smith , Lockwood, Walter , Cramer & Beck, 2009; Collins, Millard-Stafford, Sparling, Snow , Rosskopf, Webb & Omer, 1999; Fields, Wilson, Gladden, Hunter, Pascoe & Goran, 2001; Ballard, Fafara & Vukovich, 2004, Tseh, Caputo & Keefer , 2010) These common discrepancies found among studies regarding the BODPOD would lead one to believe more research needs to be done on the reliability, variability, and validity of this method on athletes and non-athletes alike. Therefore I propose that furthering research be done on the validity and reliability of this machine as well as a development of more precise technology within the BodPod to obtain more accurate readings.

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The diagram above shows the anatomy of the BODPOD. This machine is an egg shaped chamber that the patient being tested will sit in. There is a front chamber where the subject sits and a back chamber where the electronics and a diaphragm are located. (Dempster, Aitkens, 1995) The diaphragm moves, which produces pressure changes in both chambers of the machine. The pressure changes, however, are not noticeable to the subjects being tested. (Dixon, Deitrick, Pierce, Cutrufello & Drapeau, 2005; Interdevice Varability, 2005 ) The subjects being tested will enter the chamber with minimal amounts of clothes and usually a cap to cover up the hair. This is so there is as little impedance as possible to the accuracy of the machines results.

MEN

As stated previously the reliability and validity or the BODPOD when used as a means to measure body composition has been called into question, this is no different when all the subjects are males. It seems as if many studies show that the BODPOD is a mediocre form of measurement, not terrible, but not spot on. (Moon, 2008; Pribyl, Smith & Grimes , 2011 )

The studies that have been done on the accuracy on the BodPod’s measurements on males seem to be fairly consistent depending on what model or method it is being compared too. One consensus that the studies seemed to come to was that the BodPod consistently underestimated body fat percentages in males. (Dixon, Deitrick, Pierce, Cutrufello & Drapeau, 2005; Collins, Millard-Stafford, Sparling, Snow , Rosskopf, Webb & Omer, 1999) One study done on this was conducted on 61 division 1A athletes, in which the BodPod was compared to Hydrostatic weighing. This particular study showed that the PodBod is a valid form of measurement but it routinely underestimated BF% in all of the football players. (Collins, Millard-Stafford, Sparling, Snow , Rosskopf, Webb & Omer, 1999)

Other studies conducted on collegiate wrestlers yielded similar results to the study discussed above. The wrestles were tested during pre-season with the BodPod and leg-to-leg bioelectrical impedance analysis. (LIBA) The BodPod was determined as a valid form of measurement but again consistently underestimated the BF% of the collegiate athletes. (Dixon, Deitrick, Pierce, Cutrufello & Drapeau, 2005) All in all the BodPod is a valid measurement of BF% in males as long a pinpoint accuracy is not required. The results of these studies have proved that furthering research needs to be done on the validity and reliability of the BodPod.

WOMEN

A fair number of studies have been completed on the use of BodPod technology on women, especially female athletes. Because more studies have been done on female athletes this is the demographic I will focus on. The use of the BodPod would seem more crucial for women then men considering the health problems associated with weight that are ever so prevalent in females: such as anorexia, bulimia ect. The BodPod can be used as a relatively accurate way of monitoring women’s overall body composition as to be sure healthy changes are being made. (Edwards , Randall Simpson & Buchholz)

Though the BodPod is commonly used on women studies have shown that there is a larger margin of error when testing women than men. (Fields, Higgins & Hunter, 2004) One study done on Division 1 female athletes found that the BodPod overestimated body fat percentages as much as 8% in slightly overweight people, while overestimated body fat percentages in thinner people by as much as 16%. (Moon, Eckerson, Tobkin, Smith , Lockwood, Walter , Cramer & Beck, 2009)

Studies have also been done on women comparing the results of the BodPod to other forms of body composition measurement. Studies have shown that when the BodPod is tested against dual energy x-ray absorptiometry (DXA) on female athletes the DXA has yielded more accurate results. Though DXA is proven to be at least slightly more accurate the practicality and convenience of the BodPod continues to make it a more desirable form of body composition measurement. (Maddalozzo, Cardinal & Snow, 2002) When the BodPod is tested against Skinfold methods of body fat measurement it has been found that the skinfold method underestimated body fat percentages compared to DXA, BodPod and Hydrostatic weighing. (Fruth, Morgan, Darby & Tobar, 2008; Maddalozzo, Cardinal & Snow, 2002) It was concluded that the margin of error for the BodPod was actually smaller (1-2%) when compared to Skinfold Methods which yielding an error range of 2-4%. (Fruth, Morgan, Darby & Tobar, 2008) The BodPod has also been used as a sort of health indicator in women as well. Studies have also been done on female athletes to determine healthy body composition over the course of a sports season. Tests were performed pre, mid, and post season. (Anderson, 2010)

OVERALL RELIABILITY AND VALIDITY

Many studies have been done on the reliability and validity of the BodPod. Many of these studies compare the reliability and validity of the BodPod against 3C, 4C, and other compartment models. (Tseh, Caputo & Keefer , 2010) Though many studies have come to similar conclusions: that the BodPod routinely overestimates the BF% percentages in leaner individuals and underestimate BF% in overweight subjects. (Ball, 2005; Ballard, Fafara & Vukovich, 2004; Collins, Millard-Stafford, Sparling, Snow , Rosskopf, Webb & Omer, 1999)

The BodPod has gained increasing popularity in the fitness industry as well as around college campuses. This increased popularity is due to the convenient use and little training required to man the machinery. Though the convenience and cheap cost seem to take a toll on the reliability and accuracy of the BodPod when compared too more sophisticated means of body composition measuring such as hydrostatic weighing, DXA ect. (Moon, Eckerson, Tobkin, Smith , Lockwood, Walter , Cramer & Beck, 2009)

The purpose of this literature review was to point out the discrepancies, lack of reliability, validity, as well as error ranges among the research done on the BodPod when compared to other forms of measurement of body composition. The research routinely proves that the BodPod is a semi-accurate form of composition measurement but is far pinpoint accuracy. These evidences prove that it is imperative that this fletching measurement tool undergoes further research on its reliability and validity as well as the development of more sophisticated and precise technology, especially in male and female athletes.

References:

Anderson, D. (2010). The impact of feedback on dietary intake and body composition of college women volleyball players over a competitive season. Journal of Strength and Conditioning Research, 24(8), 2220-2226.

Ball, S. (2005). Interdevice variability in percent fat estimates using the bod pod. European Journal of Clinical Nutrition, 59, 996-1001.

Ballard, T., Fafara, L., & Vukovich, M. (2004). Comparison of bod pod® and dxa in female collegiate athletes . Medicine and Science in Sports Exercise, 36(4), 731-735. doi: 10.1249/01.MSS.0000121943.02489.2B

Collins, M., Millard-Stafford, M., Sparling, P. J., Snow , T., Rosskopf, L., Webb, S., & Omer, J. (1999). Evaluation of the bod pod(r) for assessing body fat in collegiate football players. Medicine and Science in Sports and Exercise, 31(9),

Dempster, P., & Aitkens, S. (1995). A new air displacement method for the determination of human body composition. Medicine and Science in Sports and Exercise, 27(12), 1692-1697.

Dixon, C., Deitrick, R., Pierce, J., Cutrufello, P., & Drapeau, L. (2005). Evaluation of the bod pod and leg-to-leg bioelectrical impedance analysis for estimating percent body fat in national collegiate athletic association division iii collegiate wrestlers. Journal of Strength and Conditioning Reseach, 19(1), 85-91.

Edwards , H., Randall Simpson, J., & Buchholz, A. (n.d.). Air displacement plethysmography for fat-mass measurement in healthy young women. Department of Family Relations and Applied Nutrition,

Fields, D., Hunter, G., & Goran , M. (2000). Validation of the bod pod with hydrostatic weighing: In¯uence of body clothing. International Journal of Obesity, (24), 200-205.

Fields, D., Higgins, P., & Hunter, G. (2004). Assessment of body composition by air-displacement plethysmography: influence of body temperature and moisture. Dynamic Medicine, 3(3), 1-7.

Fields, D., Wilson, D., Gladden, B., Hunter, G., Pascoe, D., & Goran, M. (2001). Comparison of the bod pod with the four- compartment model in adult females . Medicine and science in sports and exercise, 33(9), 1605-1610.

Fruth, J., Morgan, A. M., Darby, L., & Tobar, D. (2008). Evaluation of three skinfold equations by using the bod pod as the criterion in caucasian female athletes. Journal of Exercise Physiology, 11(1), 28-37.

Maddalozzo, G., Cardinal, B., & Snow, C. (2002). Concurrent validity of the bod pod and dual energy x-ray absorptiometry techniques for assessing body composition in young women.

Moon, J. (2008). Percent body fat estimations in college men using field and laboratory methods: A three-compartment model approach. Dynamic Medicine, 7(7), 1-9. doi: 10.1186/1476-59187-7

Moon, J., Eckerson, J., Tobkin, S., Smith , A., Lockwood, C., Walter , A., Cramer , J., & Beck, T. (2009). Estimating body fat in ncaa division i female athletes: a five-compartment model validation of laboratory methods . Euro J Applied Physiology, 105, 119-130. doi: 10.1007/s00421-008-0881-9

Pribyl, M., Smith, J., & Grimes , R. (2011). Accuracy of the omron hbf-500 body composition monitor in male and female college students. Texas A&M University , 4(1), 93-101.

Sardinha, L. B., Silva, A. M., & Teixeira, P. J. (2003). usefulness of age-adjusted equations to estimate body fat with air displacement plethysmography in male adolescent athletes. Acta Diabetol, (40),

Tseh, W., Caputo, J., & Keefer , D. (2010). Validity and reliability of the bod pod ® s / t tracking system . International Journal of Sports Medicine, (31), 704-708.