Peak Responses To Graded Exercise Protocols In Young Children

Abstract

The Bruce protocol (Bruce) is a progressive treadmill test with an aggressive initial grade that was developed for use in adults, and is often used to assess cardiac patients. Due to the steep grade, young children may terminate the Bruce prematurely. The University of Kentucky Pediatric Exercise Physiology Lab has developed a protocol (PEP Lab) with lower grades which we hypothesized would be better tolerated and potentially elicit greater peak VO2 and cardiovascular responses. PURPOSE: To compare peak oxygen uptake (pVO2; ml·kg-1·min-1), heart rate (pHR; bpm), systolic blood pressure (pSBP; mmHg), and respiratory exchange ratio (pRER) responses to the Bruce versus the PEP Lab in 43 (22 boys) young (7-11 yr old) children of varying adiposities. We also evaluated each subject’s perception of difficulty between the two protocols. METHODS: Subjects completed the Bruce and the PEP Lab protocols in a random order 1 week apart. pVO2 and pHR were determined with an integrated metabolic system, and pSBP was determined by manual auscultation. Verbal encouragement was provided during both testing sessions and test completion based on volitional fatigue. Results are expressed as mean ± SE and significance p < 0.05. RESULTS: The Bruce versus PEP Lab pVO2 (43.6 ± 1.5 vs 43.9 ± 1.5) and pHR (186.6 ± 2.0 vs 188.2 ± 2.2) did not significantly differ. However, pSBP during the Bruce was significantly lower (136.4 ± 1.4 vs 141.3 ± 1.1) and the Bruce pRER was significantly higher (1.065 ± 0.018 vs 1.013 ± 0.014) than the PEP Lab. Bruce and PEP Lab protocol pVO2, pHR, pSBP, pRER were significantly correlated (r = 0.61, 0.47, 0.53 and 0.42, respectively). The majority (88%) of the children perceived the Bruce to be more difficult. CONCLUSIONS: : A less steep protocol can elicit similar cardiopulmonary results as the Bruce. Protocols that are perceived as less difficult may help guarantee that children do not terminate their exercise tests prematurely to reaching their true pVO2. Supported by the University of Kentucky Pediatric Exercise Physiology Lab Endowment; NIH National Center for Advancing Translational Sciences through grant number UL1TR001998. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.