Sedentary behaviors, defined as sitting or lying-down activities involving an energy expenditure of 1.0 to 1.5 basal metabolic equivalents,¹ are considered the fourth greatest risk factor of mortality worldwide.² Specifically, screen media use is the most popular leisure-time sedentary behavior among children and adolescents. Screen media use includes screen-based activities such as internet surfing, computer use, mobile phone use, television viewing, and video game playing.³ On average, during their free time, children and adolescents watch television between 1.8 and 2.8 hours, play video games for 40 minutes, and use a computer 34 minutes per day.³ Quiz Ref ID Overall, 28% of children and adolescents are engaged in these screen-based activities more than 4 hours per day, with higher prevalence among boys than girls (30% vs 25%).³ Along with screen media’s advantages of access to a wide variety of resources and fast communication, use of screen media has been associated with adverse physical, psychological, and social health consequences.^4,5

During the COVID-19 pandemic, entire populations were instructed to live in home-confinement to prevent the expansion of the disease. Spain was one of the countries with the strictest conditions, as outdoor physical activity was banned for nearly two months. This study aimed to analyse the changes in physical activity and sedentary behaviours in Spanish university students before and during the confinement by COVID-19 with special focus on gender. We also analysed enjoyment, the tools used and motivation and impediments for doing physical activity. An online questionnaire, which included the International Physical Activity Questionnaire Short Form and certain “ad hoc” questions, was designed. Students were recruited by distributing an invitation through the administrative channels of 16 universities and a total of 13,754 valid surveys were collected. Overall, university students reduced moderate (−29.5%) and vigorous (−18.3%) physical activity during the confinement and increased sedentary time (+52.7%). However, they spent more time on high intensity interval training (HIIT) (+18.2%) and mind-body activities (e.g., yoga) (+80.0%). Adaptation to the confinement, in terms of physical activity, was handled better by women than by men. These results will help design strategies for each gender to promote physical activity and reduce sedentary behaviour during confinement periods.

Objective To examine the association of healthrelated physical fitness with total and central body fat in adolescents. Participants/Methods The present cross-sectional study comprises 363 Spanish adolescents (186 female participants) aged 12.5–17.5 years. We assessed fitness by the 20-m shuttle run test (cardiorespiratory fitness); the handgrip strength, the standing broad jump and the Abalakov tests (muscular strength); and the 4×10-m shuttle run test (speed–agility). Total body fat was measured by dual energy x-ray absorptiometry (DXA), BodPod and sum of six skinfolds, and central body fat was measured by DXA at three regions (R1, R2 and R3) and waist circumference. Results The Abalakov, the standing broad jump, the 4×10-m shuttle run and the 20-m shuttle run tests were negatively associated with all markers of total and central body fat in men and women after controlling for age, pubertal status and objectively assessed physical activity (p<0.01). Handgrip strength test was positively associated with waist circumference (p<0.01). Conclusions Lower body muscular strength and cardiorespiratory fitness are negatively and consistently associated with total and central body fat in adolescents, whereas levels of upper body muscular strength were superior in adolescents with higher levels of central body fat.

Reference values are necessary for classifying children, for health screening, and for early prevention as many non-communicable diseases aggravate during growth and development. While physical fitness reference standards are available in children aged 6 and older, such information is lacking in preschool children. Therefore, the purposes of this study were (1) to provide sex-and age-specific physical fitness reference standards for Spanish preschool children; and (2) to study sex differences across this age period and to characterise fitness performance throughout the preschool period. Cross-sectional. A total of 3179 preschool children (1678 boys) aged 2.8-6.4 years old from Spain were included in the present study. Physical fitness was measured using the PREFIT battery. Age- and sex-specific percentiles for the physical fitness components are provided. Boys performed better than girls in the cardiorespiratory fitness, muscular strength, and speed-agility tests over the whole preschool period studied and for the different percentiles. In contrast, girls performed slightly better than boys in the balance test. Older children had better performance in all fitness tests than their younger counterparts. Our study provides age- and sex-specific physical fitness reference standards in preschool children allowing interpretation of fitness assessment. Sexual dimorphism in fitness tests exists already at preschool age, and these differences become larger with age. These findings will help health, sport, and school professionals to identify preschool children with a high/very low fitness level, to examine changes in fitness over time, and to analyse those changes obtained due to intervention effects.