RESEARCH ARTICLE
Supramaximal Verification of Peak
Oxygen Uptake in Adolescents
With Cystic Fibrosis
Maarten S. Werkman, PT, MSc; Hendrik J. Hulzebos, PT, PhD; Pauline B. van de Weert-van Leeuwen, MSc, MD;
Hubertus G.M. Arets, PhD, MD; Paul J.M. Helders, PT, PhD; Tim Takken, PhD
Child Development & Exercise Center, Wilhelmina Children’s Hospital, University Medical Center Utrecht, Utrecht, the
Netherlands (Mr Werkman and Drs Hulzebos, Helders, and Takken); and Cystic Fibrosis Center and Department of
Pediatric Respiratory Medicine, Wilhelmina Children’s Hospital, University Medical Center Utrecht, the Netherlands
(Drs van de Weert-van Leeuwen and Arets).
Purpose: To study whether peak oxygen uptake (V
.
O
2 peak
), attained in traditional cardiopulmonary exercise
testing (CPET) in adolescents with cystic fibrosis (CF), could be verified by a supramaximal exercise test.
Methods: Sixteen adolescents with CF (forced expiratory volume in 1 second as % of predicted [range,
45%-117%]) volunteered and successively performed CPET and a supramaximal test (Steep Ramp Test [SRT]
protocol). Results: Cardiopulmonary exercise testing and the SRT resulted in comparable cardiorespiratory
peak values. We found no significant difference in oxygen uptake (V
.
O
2 peak
/kg) between CPET and the SRT
(38.9 ± 7.4 and 38.8 ± 8.5 mL min
−1
kg
−1
, respectively; P = .81). We found no systemic bias for CPET and SRT
measurements of V
.
O
2 peak
/kg and no differences between CPET and SRT V
.
O
2 peak
values within and between
the maximal and non-maximal effort groups (P > .4). Conclusion: The V
.
O
2 peak
measured in CPET seems to
reflect the true V
.
O
2 peak
in adolescents with CF. (Pediatr Phys Ther 2011;23:15–21) Key words: adolescents,
cystic fibrosis, exercise testing, exercise tolerance, pulmonary ventilation
INTRODUCTION AND PURPOSE
Exercise testing is increasingly used to evaluate the
level of exercise capacity and to define training inten-
sity in adolescents with chronic lung diseases like cys-
tic fibrosis (CF).
1,2
Cardiopulmonary exercise testing
(CPET) is currently accepted as the gold standard to
study a patient’s aerobic capacity and possible limiting
factors.
2,3
Most clinical exercise testing is performed with
0898-5669/110/2301-0015
Pediatric Physical Therapy
Copyright c 2011 Wolters Kluwer Health | Lippincott Williams &
Wilkins and Section on Pediatrics of the American Physical Therapy
Association.
Correspondence: H.J. Hulzebos, PT, PhD, Child Development & Ex-
ercise Center, Wilhelmina Children’s Hospital, Room KB.02.056, Uni-
versity Medical Center Utrecht, PO Box 85090, 3508 AB Utrecht, The
Netherlands (H.Hulzebos@umcutrecht.nl).
Grant Support: This study was funded by an unconditional research
grant (DO-IT) from the Scientific College Physiotherapy of the Royal
Dutch Society for Physiotherapy (Wetenschappelijk College Fysiother-
apie, Koninklijk Nederlands Genootschap voor Fysiotherapie) and an
unrestricted grant from the Dutch Cystic Fibrosis Society.
DOI: 10.1097/PEP.0b013e318208ca9e
progressive workloads during cycle ergometer or tread-
mill exercise. During both tests, cardioventilatory parame-
ters such as peak oxygen uptake (V
.
O
2 peak
), peak workload
(W
peak
), peak heart rate (HR
peak
), and the ratio of carbon
dioxide production to oxygen consumption (respiratory
exchange ratio [RER]) can be calculated using gas analysis
of expired air.
4
The most important parameter of exercise capacity
is the V
.
O
2 peak
.
2,3,5
Maximum oxygen uptake (V
.
O
2 max
) is
considered to be the maximum attainable oxygen uptake
by the cardiorespiratory and neuromuscular system, re-
sulting in a
˙
VO
2
plateau at the end of testing despite a
further increase in workload.
6,7
Furthermore, V
.
O
2 peak
is
defined as the highest level of oxygen uptake attained dur-
ing a single test without necessity of a plateau of the
˙
VO
2
curve.
8
Questions can be raised about the validity of that
attained
˙
VO
2peak
during CPET in adolescents with CF, be-
cause reduced exercise capacity during CPET in adoles-
cents with CF compared with peers without the disease has
been reported.
9-12
However, the observed peak heart rates
in these studies were lower than values observed in ado-
lescents without CF. Therefore, this lower V
.
O
2 peak
might
be due to an actual lower V
.
O
2 peak
or to an incapability of
CPET to reach real V
.
O
2 peak
in adolescents with CF. This
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins and Section on Pediatrics of the American Physical Therapy
Association. Unauthorized reproduction of this article is prohibited.
Pediatric Physical Therapy Verification of
˙
Vo
2peak
in CF 15