Background: The skinfold caliper reading of the skinfold thickness depends on its dynamic compressibility. This has led to the fact that, while it is indicated that skinfold readings should be taken when the reading is stable, there is no consensus on at what second the reading should be taken after the application of the skinfold caliper. The new Lipowise PRO digital skinfold caliper was used to analyze the evolution of skinfold readings under skinfold caliper pressure. The aim of the present investigation were: a) to analyze the evolution of the reading time of individual skinfolds when subjected to skinfold caliper pressure and when the skinfold reading reaches stability; b) to describe the physical behavior of skinfold tissues' time response to skinfold caliper pressure, and to explore differences between sites and subjects' skinfolds compressibility; and c) to analyze the sex differences in both the reading and the evolution of the skinfold over time.
Methods: A descriptive cross-sectional design was followed with a convenience sample of 165 healthy young adults (79 males and 86 females), with eight skinfolds measured using the Lipowise PRO skinfold caliper. The Lipowise PRO skinfold caliper uses a programmable reading time allowing for the measurement of the skinfold's thickness at a rate of 100 times per second, and monitoring skinfold behavior over the 3-second measurement period, thereby enabling the assessment of the tissue response to the constant force exerted by the skinfold caliper jaws.
Results: All skinfolds showed statistical differences in terms of compressibility characteristics (p < 0.001). Significant differences were found between measurement time points for individual skinfolds and sum of skinfolds (p < 0.001-0.025). Stabilization being found depending on the skinfold measured from 1.5 seconds for biceps, subscapular, iliac crest, supraspinale, abdominal, and thigh skinfolds; 2.0 seconds for ∑6 and ∑8 skinfolds; and 2.5 seconds for triceps and calf skinfolds. It was observed an effect of sex on this issue (p < 0.001-0.030). More specifically, in the case of males, the supraspinale and abdominal skinfolds stabilized after 1.5 seconds; the calf skinfold and ∑6 and ∑8 skinfolds stabilized after 2 seconds; while the rest of the skinfolds did not stabilize until 3 seconds. In the case of females, no stabilization of the triceps skinfold was found, while the rest of the individual skinfolds and the ∑6 and ∑8 skinfolds stabilized from 1.5 seconds. A regression analysis indicated that skinfold thickness could be predicted based on measurement time in 50-77% of the cases (p = 0.001).
Conclusion: A skinfold caliper application, using the digital caliper Lipowise PRO, of three seconds may be sufficient for achieving stability in the measurement and for obtaining the minimum value for most individual and sum of skinfolds. However, there are certain skinfolds that may require more time when performed on certain individuals, which vary according to sex.
Keywords: Skinfold thickness; anthropometry; body composition; fat mass; response time; skinfold caliper.