Skinfold calipers: which instrument to use?

The considerable amount of original and generic types of skinfold calipers available is a source of systematic measurement error. This study is a brief report that critically examines the original and illustrated structural configuration of the three main types of skinfold calipers. For more than half a century, the Harpenden®, Lange® and Slim Guide® skinfolds calipers have been widely used in clinical and research settings. It is well established that the physical, mechanical and functional specificity of each type of skinfold caliper makes its interchangeable use impossible. Our report suggests that commercially available technical specifications are insufficient to judiciously choose a skinfold caliper. The area of the jaws, the coefficient of spring and the static and dynamic downward pressure of each type of skinfold caliper must be determined in the metrological laboratory and added to the technical user manual. Choosing a type of skinfold caliper for regular use, without conflict of commercial interest, requires a critical understanding of the physical, mechanical and functional characteristics that configure it. Therefore, a new downward static calibration test and the first eligibility flowchart for a skinfold caliper have been proposed. Finally, the information gathered in this report may be useful for manufacturers of anthropometric instruments and health professionals who use the skinfold technique as a tool for diagnosis and nutritional control.

Validity and accuracy of body fat prediction equations using anthropometrics measurements in adolescents.

BACKGROUND: The pediatric relative fat mass (RFM) has been recently presented and validated as an index for estimating percentage body fat (%BF) in North American children and adolescents. Similar to body mass index (BMI) and tri-ponderal mass index (TMI), RFM uses anthropometric measures (i.e., weight, height and waist circumference) to estimate body composition. The primary purpose of this study was to validate the newly developed RFM equation for %BF prediction in Southern Brazilian adolescents; as secondary objective, we compared %BF estimation from BMI- and TMI-derived equations. METHODS: A total of 631 individuals (434 boys) aged 11 to 18 were analyzed. Bland-Altman analyses were used to determine concordance between predicted equations and %BF measured by DXA; results are presented using mean difference (i.e., bias) and standard deviation. Sensitivity and specificity were calculated for %BF percentile classifications. RESULTS: RFM underestimated %BF in 65.2% of boys (- 4.3 ± 2.8%) and 84.8% of girls (- 5.3 ± 2.7%). In contrast, TMI overestimated %BF in 62.9% of boys (4.0 ± 2.9%) and 56.3% (3.5 ± 3.0%) of girls. The performance of BMI showed mixed results; %BF was overestimated in 68.4% of boys (5.0 ± 4.0%) and underestimated in 67.5% of girls (- 3.9 ± 2.6%), all p < 0.001. Although, RFM had the highest specificity for %BF percentile classifications, sensitivity was low and inferior to BMI and TMI. CONCLUSION: TMI was superior to RFM and BMI in predicting %BF in Southern Brazilian adolescents. Using RFM, BMI or TMI equations for %BF prediction without a population-specific correction factor may lead to incorrect interpretations. We suggest that correction factors should be investigated to improve the accuracy of these surrogate indices for body composition assessment. LEVEL OF EVIDENCE: Level V, cross sectional descriptive study.

Application of a photogrammetric kinematic model for prediction of lung volumes in adolescents: a pilot study.

BACKGROUND: There are several ways to measure the respiratory system, among them inductance plethysmography and three-dimensional kinematic analysis, methods of high cost and difficult transportability. The objective of this study was to correlate respiratory volumes obtained by spirometry standard equipment with a biomechanical model photogrammetric analysis of adolescents. METHODS: We evaluated 50 subjects of both genders, aged between 14 and 17 years old, excluding those with respiratory obstruction or restriction. Stickers with markers, there was a five-point mapping for anatomical modeling and photogrammetry, with each evaluated in supine position, was sought to test the Forced Vital Capacity (FVC). The test was filmed and repeated three times. Images of the films were extracted for the moment of maximum exhalation and inhalation of proof with better breathing. With the use of a commercial software, defined the respiratory volumes to the thorax and abdomen. RESULTS: The photogrammetric analysis has found values strongly correlated with the spirometric measurements of FVC (0.812), forced expiratory volume in one second (FEV1 - 0.708), Peak Expiratory Flow (PEF - 0.762) in addition to post test performed Inspiration (IP- 0.816). There was a higher ventilatory mobility for boys than girls for Lower Chest and Lower and Upper Abdomen. It was possible to reach a regression R2 = 0.866 for proof of FVC and R2 = 0.776 for IP with the use of photogrammetry, presenting a standard error of 0.353 and 0.451, respectively. CONCLUSIONS: Photogrammetry can be used to study thoracoabdominal movements by applying analytical two-dimensional and three-dimensional images acquired using a video camera being, applicable and reproducible.