Cardiorespiratory fitness in adolescents before and after the COVID-19 confinement: a prospective cohort study

Long periods of free-movement restrictions may negatively affect cardiorespiratory fitness and health. The present study investigated changes after the COVID-19 confinement in maximal oxygen intake (VO(2) max) levels in a sample of 89 Spanish school children aged 12 and 14 years at baseline (49.8% girls). The 20-m shuttle run test served to estimate VO(2) max before and after the COVID-19 confinement. Paired t-tests estimated an overall difference of − 0.5 ml.kg(−1).min(−1) (SD 0.3) (p = 0.12), whereas the highest significant reductions were observed for girls aged 14 years (− 1.5 ml.kg(−1).min(−1) (SD 0.6) (p < 0.05)). Boys aged 14 years showed a slight increase (0.4 ml.kg(−1).min(−1) (SD 0.5) (p = 0.44)), whereas boys aged 12 years presented an important decrease (− 1.2 ml.kg(−1).min(−1) (SD 0.7) (p = 0.14)). Healthy Fitness Zone (HFZ) levels also experienced a decrease of − 3.4% as regards baseline levels over the examined period. All the examined subgroups showed lower levels in relation to a normal VO(2) max rate development, although girls aged 14 and boys aged 12 years accounted for the highest part. Conclusion: The results indicate that COVID-19 confinement might delay the normal development of VO(2) max in adolescents. Strategies to tackle this concerning decline are warranted.