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Indexed/Abstracted in: Chemical Abstracts, CINAHL, Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
Impact Factor 1,111
Online ISSN 1827-1928
Jacobsen D. J. 1, Coast R. 2, 3, Donnelly J. E. 1
1 Human Performance Laboratory, University of Nebraska-Kearney, Kearney, NE;
2 Human Performance Laboratory, Texas A&M University, College Station, TX;
3 Exercise Physiology Laboratory, Northern Arizona University, Flagstaff, AZ, USA
Objectives. To evaluate the slow component of V.O2 in persons of different fitness levels exercising at different intensities and the contribution of proposed mediators to the slow component of V.O2 using equations from the literature.
Experimental design. Cross-sectional.
Participants. Low (N=15) and high (N=15) fitness (V.O2max of 37 vs 62 ml·min-1·kg-1).
Measures. Each subject completed, in random order, a series of 12 mim cycle ergometer exercise trials corresponding to 50, 60, 70 and 80% of V.O2max. V.O2, minute ventilation (MV), blood lactate (BL), rectal temperature (RT), heart rate and blood pressure were measured.
Results. There was a significant (p<0.05) increase in the slow component of V.O2 for each level of fitness across time and at each workrate. There were no between group differences for any variable. The increase in the slow component of V.O2 ranged from 70 ml·min-1 for the lighter workrates to 543 ml·min-1 for the high fitness group at 80% of maximal V.O2 (both p<0.05). The oxygen cost of MV, RT and rate pressure product accounted for about 50% of the observed increase in the slow component of V.O2. MV appears to increase in a pattern most similar to the slow component of V.O2 and the oxygen cost of MV generally accounted for the highest percentage of the observed increase.
Conclusions. The slow component of V.O2 needs to be considered when prescribing exercise. These results are not conclusive concerning the primary mediators of the slow component of V.O2.