Bodpod

Body composition and anthropometric measures were taken before the physical fitness tests, in accordance with standard procedures, i.e., wearing only underwear and no shoes²⁶ . Height was measured using a wall stadiometer (Tillquist, Spånga, Sweden) to the nearest 0.5 cm. Body composition was measured after a 2 h fast using air-displacement plethysmography (BodPod, COSMED USA, Concord, CA, USA), which is a reliable, valid and safe technique for the evaluation of body composition in children²⁶ . Briefly, body weight was measured to the nearest gram with an electronic scale attached to the air-displacement plethysmograph (BodPod, COSMED USA, Concord, CA, USA). Subsequently, body volume was measured using the BodPod and body density was calculated as measured weight divided by measured volume. Subsequently, body fatness was calculated utilizing the densities of fat- and fat-free mass according to Lohman’s model²⁷ . BMI was calculated as body weight (kg) divided by height (m) squared. Overweight and obesity were classified according to the BMI cut-offs by Cole and Lobstein^{28 (link)}. Fat mass index was calculated by dividing fat mass (kg) with height (m) squared (i.e., fat mass/height²), whereas fat-free mass index was calculated as the amount of fat-free mass (kg) divided by height (m) squared (i.e., fat-free mass/height²).

Subjects were instructed to drink only water and not to eat or exercise for the preceding two hours. Upon arrival to the laboratory, height and body mass were recorded to the nearest 0.01 cm and 0.02 kg, respectively using a stadiometer and digital scale (Bod Pod; Cosmed, Chicago, IL, USA) calibrated according to manufacturer guidelines with subjects bare foot. Body composition was then assessed using air displacement plethysmography (Bod Pod; Cosmed, Chicago, IL, USA) calibrated according to manufacturer guidelines. Lycra and swim caps were worn during testing. Jewelry was removed prior in accordance with standard operating procedures in order to reduce air displacement. A trained Bod Pod technician performed all testing. Previous studies indicate air displacement plethysmography to be an accurate and reliable means to assess changes in body composition [26 (link)]. Body mass and body volume were then used to estimate body fat percentage (%BF) based upon the Brozek equation for men and women [27 (link)].

Subjects were instructed to drink only water and not to eat or exercise for the preceding two hours. Further, subjects were advised to refrain from any training for the preceding 24 h and no lower body training for the preceding 48 h. Upon arrival to the laboratory, height and body mass were recorded to the nearest 0.01 cm and 0.02 kg, respectively using a stadiometer and digital scale (Bod Pod; Cosmed, Chicago, IL, USA) calibrated according to manufacturer guidelines with subjects bare foot. Body composition was then assessed using air displacement plethysmography (Bod Pod; Cosmed) calibrated according to manufacturer guidelines. Lycra and swim caps were worn during testing and jewelry was removed prior in accordance with standard operating procedures to reduce air displacement. A trained Bod Pod technician performed all testing. Previous studies indicate air displacement plethysmography to be an accurate and reliable means to assess changes in body composition [19 (link)]. Body mass and body volume were then used to estimate body fat percentage (%BF) based on the Brozek equation for men and women [20 (link)]. Fat free mass (FFM) and fat free mass index (FFMI) were calculated using the following equations.

$\text{FFMI}=\frac{\text{Fat free mass} \left(\text{FFM}\right) \left(\text{kg}\right)}{{\text{Body height}}^2\left(\mathrm{m}\right)}$