Measurement Differences Between Harpenden® And Slim Guide Rosscraft® Skinfold Calipers In Active Adults

BACKGROUND: The International Society for the Advancement of Kinanthropometry (ISAK) recommends the Harpenden® Skinfold Caliper (HSC) for its accuracy, reliability, and 0.2 mm resolution. Furthermore, HSC is the only one used in experiments that determined the static and dynamic calibration by jaw’s pressure and the maintenance procedures of the physical-mechanical components (Cintra-Andrade et al., 2023). However, many professionals use plastic calipers with 1.0 mm resolutions in their daily practice and, although not widely studied, this could result in measurement inaccuracies. PURPOSE: Compare skinfold measurements between HSC and the Slim Guide Rosscraft® (SGSC), and subsequently the calculated body fat percentage (% BF) in active adults. METHODS: Forty-six active subjects (25 men and 21 women; Age: 32.81 ± 13.87 years; Weight: 71.37 ± 13.46 kg; Height: 171.56 ± 10.96 cm; BMI: 24.11 ± 2.92 kg/m2) were assessed with the ISAK anthropometric measurement protocol of six skinfolds (triceps, subscapular, supraespinale, abdominal, front thigh, and medial calf) with both HSC and SGSC by the same evaluator. Then, the % BF was calculated through the 5-component equation of Kerr & Ross (1991) and the hydrodensitometry-based equation of Yuhasz (1974). The comparison of the sum of skinfolds (Σ6SF) and % BF, and the correlation between calipers were analyzed using Paired T-tests and effect size (Cohen's d) and Pearson coefficient, respectively, with p < 0.05. RESULTS: There are significant differences between HSC and SGSC measurements in Σ6SF (80.28 ± 26.12 mm vs. 66.17 ± 25.72 mm, p < 0.001, d = 5.4, respectively), % BF based on Kerr & Ross equation (27.98 ± 4.78% vs. 24.58 ± 4.67%, p < 0.001, d = 4.1, respectively), and % BF based on Yuhasz equation (13.59 ± 5.08% vs. 11.77 ± 4.77%, p < 0.001, d = 3.6, respectively), despite the very high correlation between calipers (r = 0.995, p < 0.001). CONCLUSIONS: Overall, our findings suggest that professionals be cautious when reporting results using plastic calipers despite the very high relationship with HSC because SGSC yields lower Σ6SF and consequently underestimates % BF according to classical equations. Future studies should investigate whether this trend holds in overweight/obese subjects and elite athletes.