Skip to main content
Kent Academic Repository

Reliability of Cycling Gross Efficiency Using the Douglas Bag Method

Hopker, James G., Jobson, Simon A., Gregson, Hannah C, Coleman, Damian A, Passfield, Louis (2012) Reliability of Cycling Gross Efficiency Using the Douglas Bag Method. Medicine and Science in Sports and Exercise, 44 (2). pp. 290-296. ISSN 0195-9131. (doi:10.1249/MSS.0b013e31822cb0d2) (KAR id:28959)


Purpose: The aim of this study was to establishthe reliability of gross efficiency (GE) measurement (the ratio of mechanical power input to metabolic power output, expressed as apercentage) using the Douglas bag method. Methods: The experiment was conducted in two parts. Part 1 examined the potential forerrors in the Douglas bag method arising from gas concentration analysis, bag residual volume, and bag leakage or gas diffusion rates.Part 2 of this study examined the within-subject day-to-day variability of GE in 10 trained male cyclists using the Douglas bag method.Participants completed three measurements of GE on separate days at work rates of 150, 180, 210, 240, 270, and 300 W. Results: Theresults demonstrate that the reliability of gas sampling is high with a coefficient of variation (CV) G0.5% for both O2 and CO2. Thebag residual volume CV was È15%, which amounts to +0.4 L. This could cause the largest error, but this can be minimized bycollecting large gas sample volumes. For part 2, a mean CV of 1.5% with limits of agreement of +0.6% in GE units, around a mean GEof 20.0%, was found. Conclusions: The Douglas bag method of measuring expired gases and GE was found to have very high reliabilityand could be considered the gold-standard approach for evaluating changes in GE. Collecting larger expired gas samples minimizespotential sources of error.

Item Type: Article
DOI/Identification number: 10.1249/MSS.0b013e31822cb0d2
Subjects: Q Science > QP Physiology (Living systems)
R Medicine > RC Internal medicine > RC1200 Sports medicine
Divisions: Divisions > Division of Natural Sciences > Sport and Exercise Sciences
Depositing User: Louis Passfield
Date Deposited: 24 Feb 2012 00:42 UTC
Last Modified: 16 Nov 2021 10:07 UTC
Resource URI: (The current URI for this page, for reference purposes)

University of Kent Author Information

Hopker, James G..

Creator's ORCID:
CReDIT Contributor Roles:

Jobson, Simon A..

Creator's ORCID:
CReDIT Contributor Roles:

Passfield, Louis.

Creator's ORCID:
CReDIT Contributor Roles:
  • Depositors only (login required):

Total unique views for this document in KAR since July 2020. For more details click on the image.