The purpose of this investigation was to assess the accuracy of the COSMED
K4 b(2) portable metabolic measurement system against the criterion Douglas
bag (DB) method. During cycle ergometry on consecutive days, oxygen consum
ption (VO2), carbon dioxide production (VCO2), minute ventilation (V-2), an
d respiratory exchange ratio (R) were measured at rest and during power out
puts of 50, 100, 150, 200, and 250W. No significant differences (P >0.05) w
ere observed in VO2 between the K4 b(2) and DB at rest and at 250 W. Though
the K4 b(2) values were significantly higher (P <0.05) than DB values at 5
0, 100, 150, and 200 W, the magnitude of these differences was small (0.088
, 0.092, 0.096, and 0.088 L x min(-1), respectively). VCO2 and V-E values f
rom the K4 b2 were significantly lower than the DB at 200 and 250 W, while
no significant differences were observed from rest through 150W. The slight
overestimation of VO2 (50-200 W) combined with the underestimation of VCO2
(200 and 250 W) by the K4 b(2) resulted in significantly lower R values at
every stage. These findings suggest the COSMED K4 b(2) portable metabolic
measurement system is acceptable for measuring oxygen uptake over a fairly
wide range of exercise intensities.