title: Exercise-induced breathing patterns of youth are related to age and intensity.
abstract: The influences of sex, age, exercise intensity, and end-tidal CO(2) on the inspiratory drive ([V(T) kg(-1)] x T(i)(-1)) and respiratory timing (T(i) x T(tot)(-1)) components of ventilation were examined in 295 youth (138 females, 157 males); similarly distributed 8-18 years of age. Ventilatory and metabolic measures were collected breath-by-breath at rest and during a slow walk (4.0 km h(-1)), fast walk (5.6 km h(-1)) and run (8.0 km h(-1)). Regression modeling for drive (age, sex, and P(ET)CO(2)) found that sex was significant (R (2) < 0.017; P < 0.05) for rest and running, but not walking. Compared to rest, drive increased by 120% for the slow walk, 217% for the fast walk and 258% for the run (P < 0.0001). Drive decreased with age (P < 0.0001): rest = 0.41 ml kg(-1) s(-1) year(-1); slow walk = 0.90 ml kg(-1) s(-1) year(-1); fast walk = 1.30 ml kg(-1) s(-1) year(-1); and run = 1.47 ml kg(-1) s(-1) year(-1). In the regression models for timing, sex provided approximately 1% of the variance during the run, but was not significant during rest or walking. Timing increased with exercise intensity by approximately 0.02 units (P < 0.001), but decreased by approximately 0.002 units year(-1) with age for all conditions (P < 0.003). Changes in drive and timing were marginally related to end-tidal CO(2) (exercise R(2) < 0.063 for all models). These results suggest that in the control of inspiratory drive and timing during exercise in youth, sex is of minor importance but there are age-related changes which are marginally associated with CO(2).
authors.affiliation: Department of Exercise and Sport Science, The University of North Carolina, 209 Fetzer Gymnasium, Chapel Hill, NC 27599-8700, USA. kondrak@unc.edu
authors.forename: Kristin S
authors.initials: KS
authors.lastname: Ondrak
authors.forename: Robert G
authors.initials: RG
authors.lastname: McMurray
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D002648:Child; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*; D012737:Sex Factors; D016138:Walking / Q000502:physiology*