Purpose:
The purpose of this investigation was to determine the effect of body movement on the ability of a portable telemetric gas analysis device, the Cosmed K4b², to produce a reliable measure of walking oxygen consumption (VO₂).

Methods:
Thirteen adults were asked to report to a laboratory for three test sessions. During Session 1, participants were familiarized with the data collection procedures and completed a 15-min treadmill accommodation. In Sessions 2 and 3, each participant completed four 5-min treadmill walking trials at 1.8 m • sec^–1 under different experimental conditions while VO₂ was collected using the portable system. The four conditions were used to manipulate the portable metabolic system to mimic different types of movement.

Results:
Data analysis revealed no significant differences (p = 0.070) amongst VO₂ values across all four experimental conditions during Sessions 2 and 3. Between-day coefficients of variation for the mean VO₂ values of the four conditions ranged from 2.7% to 3.8%, with the highest level of variation occurring whilst the unit was strapped to the participant’s chest.

Conclusions:
Viewed collectively, the Cosmed K4b² may produce reliable measures of VO₂ in adult participants during treadmill walking who exhibit little vertical oscillation. However, future research is necessary to determine if the K4b² is a valid instrument for collecting VO₂ data if excessive body movement in the vertical direction can affect the data collection instrumentation.