Aerobic capacity limitation in adolescent children born premature is driven by blunted cardiac output rather than activity level or strength
Authors: Centanni Ryan , Haraldsdottir Kristin , Tetri Laura , Goss Kara , Palta Mari , Beshish Arij , Watson Andrew , Eldridge Marlowe 
Published: November 2023

PurposeOne in 10 children in the United States are born preterm. Young adults born preterm have been shown to have impaired gas exchange and diminished aerobic capacity, but very little is known about the effects of prematurity on fitness and cardiovascular function in adolescent children. The intent of this study was to identify the etiology of reduced exercise capacity in adolescent children born premature by measuring strength, power, maximal aerobic capacity (VO2max), and cardiac output (Q) using bioimpedance, while also collecting pubertal development (Tanner stage), and physical activity assessment data. We hypothesized that adolescent children would have lower strength, power, physical activity scores and VO2max compared to term born controls.MethodsEight children born preterm (PT) (age 12–13, birth weight <1500g, gestational age <32 weeks) and 7 age‐matched children born full term (CT) (gestational age 38–40 weeks) completed maximal hand grip strength (HG) using a dynamometer and vertical jump displacement (VJ). Subjects performed a progressive maximal exercise test on a cycle ergometer, with continuous measurement of O2 consumption (ml/kg/min), as well as Q using thoracic bioimpedance. Q was indexed to body surface area (BSA (m2), Qi). Subjects completed pubertal (Tanner Stage) and physical activity questionnaires (PAQ‐C). Statistical analysis was done using multiple t‐tests.ResultsThere was no difference in PT compared to CT in combined HG (112.1 ± 9.6 v 115.3 ± 11.5 kg, p=0.79), VJ (29.5 ± 5.0 v 33.5 ± 4.7 cm, p=0.23), Tanner Stage (3.3 ± 0.6 v 2.9 ± 0.7, p=0.19), or PAQ‐C (2.05 ± 0.5 v 2.15 ± 0.4, p=0.72). PT had lower relative maximal oxygen consumption (VO2max, ml/kg/min) compared to CT (38.3 ± 9.3 v 51.5 ± 7.3 ml/kg/min, p=0.03). Qi significantly increased in PT from rest to maximal exercise (6.7 ± 1.6 v 10.4 ± 3.4 L/min/m2, p=<0.01) and significantly increased in CT (5.9 ± 0.9 v 14.2 ± 3.4 L/min/m2, p<0.01), however the change in Qi from rest to maximal exercise was significantly smaller in PT compared to CT (5.6 ± 1.1 v 9.0 ± 2.6 L/min/m2, p=0.02). By calculating SVi from Qi and HR, it was found that SVi did not increase in PT from rest to maximal exercise (51.7 ± 9.0 v 53.3 ±8.3 ml/m2, p=0.04), while SVi significantly increased in CT (47.4 ± 4.0 v 67.7 ± 14.4 ml/m2, p=0.01). The change in SVi from rest to maximal exercise was significantly smaller in PT compared to CT (1.6 ± 6.5 v 13.2 ± 2.3 ml/m2, p=0.04).ConclusionAdolescent children born preterm exhibit lower VO2max and significantly lower maximal Qi than age‐matched controls. PTs do not have decreased hand grip strength or vertical jump displacement compared to CTs. PTs have similar levels of physical activity as CTs. This data suggests that PTs may not be able to adequately increase Q in response to increasing metabolic demand, and this may reduce their ability to exercise at higher intensities. These differences are not due to differences in activity level or puberty, and are localized to cardiac‐specific differences.Support or Funding InformationNational Institutes of Health: 1R01 HL086897 (M.W.E.) and R01 HL38149 (M.P.)