title: The influence of priming exercise on oxygen uptake, cardiac output, and muscle oxygenation kinetics during very heavy-intensity exercise in 9- to 13-yr-old boys.
abstract: The present study examined the effect of priming exercise on O(2) uptake (Vo(2)) kinetics during subsequent very heavy exercise in eight 9- to 13-yr-old boys. We hypothesised that priming exercise would 1) elevate muscle O(2) delivery prior to the subsequent bout of very heavy exercise, 2) have no effect on the phase II Vo(2) tau, 3) elevate the phase II Vo(2) total amplitude, and 4) reduce the magnitude of the Vo(2) slow component. Each participant completed repeat 6-min bouts of very heavy-intensity cycling exercise separated by 6 min of light pedaling. During the tests Vo(2), muscle oxygenation (near infrared spectroscopy), and cardiac output (Q) (thoracic impedance) were determined. Priming exercise increased baseline muscle oxygenation and elevated Q at baseline and throughout the second exercise bout. The phase II Vo(2) tau was not altered by priming exercise (bout 1: 22 + or - 7 s vs. bout 2: 20 + or - 4 s; P = 0.30). However, the time constant describing the entire Vo(2) response from start to end of exercise was accelerated (bout 1: 43 + or - 8 s vs. bout 2: 36 + or - 5 s; P = 0.002) due to an increased total phase II Vo(2) amplitude (bout 1: 1.73 + or - 0.33 l/min vs. bout 2: 1.80 + or - 0.59 l/min; P = 0.002) and a reduced Vo(2) slow component amplitude (bout 1: 0.18 + or - 0.08 l/min vs. bout 2: 0.12 + or - 0.09 l/min; P = 0.048). These results suggest that phase II Vo(2) kinetics in young boys is principally limited by intrinsic muscle metabolic factors, whereas the Vo(2) total phase II and slow component amplitudes may be O(2) delivery sensitive.
authors.affiliation: Children's Health and Exercise Research Centre, School of Sport and Health Sciences, Univ. of Exeter, Exeter, EX1 2LU, UK. A.R.Barker@exeter.ac.uk
authors.forename: Alan R
authors.initials: AR
authors.lastname: Barker
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jones
authors.forename: Neil
authors.initials: N
authors.lastname: Armstrong
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D002302:Cardiac Output; D002648:Child; D015444:Exercise; D005080:Exercise Test; D006339:Heart Rate; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010108:Oxyhemoglobins / Q000378:metabolism; D012039:Regional Blood Flow; D019265:Spectroscopy, Near-Infrared; D013318:Stroke Volume
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin; D010100:Oxygen