Oxygen uptake kinetics during treadmill walking in adolescents with clinically stable cystic fibrosis

ABSTRACT

Background

Oxygen uptake (V̇O₂) kinetics have been shown to be slowed in adolescents with cystic fibrosis (CF) during heavy-intensity cycling and maximal exercise testing.

Objectives

This study investigated V̇O₂ kinetics in adolescents with CF compared to control adolescents (CON) during a treadmill-walking exercise.

Methods

Eight adolescents with CF and mild-to-moderate pulmonary obstruction (5 girls; 13.1 ± 2.5 years; FEV₁ 67.8 ± 21.4%) and 18 CON adolescents (10 girls; 13.8 ± 1.8 years) were recruited. Pulmonary gas exchange and ventilation were measured during a single transition of 10 min of treadmill walking and a 5 min seated recovery period. Participant’s walking speed was determined during a one-minute self-paced walking task along a 50-m corridor. A six-parameter, non-linear regression model was used to describe the changes in V̇O₂ function during the treadmill walking and recovery, with monoexponential curve fitting used to describe the mean response time (MRT₁) at the onset of exercise, and the half-life (T_1/2V̇O₂) at the offset of exercise. V̇O₂ baseline and amplitude, minute ventilation and respiratory equivalents were recorded.

Results

V̇O₂ kinetics were slower in CF group compared to CON group during the treadmill walking with a greater MRT₁ (32 ± 14 s vs 21 ± 16 s; p = .04, effect size = 0.75). The T_1/2V̇O2 was prolonged during recovery in CF group compared to CON group (86 ± 24 s vs 56 ± 22 s; p = .04, effect size = 1.31). The mean VE/V̇CO₂ during exercise was the only parameter significantly greater in CF group compared to CON group (32.9 ± 2.3 vs 29.0 ± 2.4; p < .01, effect size = 1.66).

Conclusion

V̇O₂ kinetics were found to be slowed in adolescents with CF during treadmill walking.

KEYWORDS:

• Exercise capacity
• muscle metabolism
• exercise testing
• pulmonary disease
• pediatrics

Acknowledgments

The authors would like to thank Johanna Robertson and Jennifer Dandrea Palethorpe for language assistance and constructive criticism. The authors would also like to thank Dr. William Poncin, Professor Gilles Caty and Professor Thierry Zintz for their precious advice regarding the study design and the writing of the article.

Declaration of Interest

The authors have no conflicts of interest to disclose.