Skinfold caliper

Gestational age (GA) was estimated by a dating scan in the first trimester; preterm birth was defined as delivery of a live birth <37 weeks of gestation. Birth weight was measured shortly after birth to the nearest 1 g (SECA 334; SECA Corp.), and recumbent length measured to the nearest 0.5 cm from the top of the head to the soles of the feet (SECA 210). Sex-specific birth weight-for-GA z-scores were derived using a global birth weight reference^{47 (link)} adapted for the GUSTO population^{48 (link)}. Triceps and subscapular skinfold thicknesses, which have greater discriminative power than other anthropometric measurements for neonatal total body adiposity^{49 (link)}, were measured in triplicate to the nearest 0.2 mm on the right side of the body by anthropometrists and summed (Holtain Skinfold Caliper; Holtain Ltd.). All research personnel were trained according to standardized procedures obtained from the PhenX toolkit^{50 (link)}. Infant sex was retrieved from birth delivery reports.

All measurements were performed at schools in the morning according to the World Health Organization (WHO) standards [35 ].
Weight and height were measured with the participants in underwear and barefoot using a digital electronic scale (model SECA ALPHA, GMBH & Co., Igny, France) (range: 0.1–150 kg, accuracy 100 g) and a Harpenden digital stadiometer (Pfifter, Carlstadt, NJ, USA) (range: 70–205 cm, accuracy 1 mm), respectively. Body mass index (BMI) was calculated by dividing the weight (kg) by height squared (m²). Subsequently, the BMI z-score (z-BMI) was calculated. The cut-off points were established according to the standard deviation of the z-score established by the WHO [36 ] (z < −2: underweight, z: −2–1: normal weight z: 1–2: overweight; y z > 2: obesity) [37 (link)].
The tricipital skinfold was measured on the right side of the body using a Holtain skinfold caliper (constant pressure of 10 g/mm² (range: 0–39 mm) and 0.1 mm accuracy, Holtain Ltd., Crymych, Wales) following the recommendations by the ISAK [38 ]. Fat mass (FM) was obtained using the formula by Dezemberg et al. in 1999 [39 (link)]. FM was classified according to McCarthy’s cut-off points as insufficient fat, normal fat, excessive fat, and obesity [40 (link)].

Procedures and instrumentation were previously described in detail [6 (link)]. In brief, all cycling tests were performed on a cycle ergometer (Velotron, RacerMate inc, Washington, USA) in a laboratory with stable conditions. Measurements included blood lactate (Biosen C-Line Sport, EKF Industrial Electronics, Magdeburg, Germany), heart rate (Polar RS800, Polar Electro OY, Kempele, Finland), skinfold thickness (Holtain skinfold caliper, Holtain Ltd, Crymych, Wales) and pVO₂ (Open-circuit indirect calorimetry, Oxycon Pro, Jaeger GmbH, Hoechberg, Germany, calibrated using gas from Riessner-Gase GmbH & Co, Lichtenfels, Germany and a 3-liter syringe). Muscle oxygenation was measured with a continuous wave near-infrared spectrophotometer system (Portamon, Artinis Medical Systems, the Netherlands) and an inflatable pneumatic cuff system (Hokanson E20 Rapid Cuff Inflator + Hokanson AG-101 Air Source, Marcom Medical ApS, Denmark) was used to apply the arterial occlusions.
Pedals instrumented with force cells (Revere Model 9363, capacity 250 kg per cell, the Netherlands) were used to measure pedal forces and a ProReflex 3D motion analysis system (Qualisys, Sweden) was used for kinematic analysis. A detailed description of the force pedal and kinematic analysis systems can be found in Ettema et al. [19 ] and Skovereng et al [6 (link)].