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A re‐analysis of the 1968 Saltin et al. “Bedrest” paper
Author(s) -
Wagner P. D.
Publication year - 2015
Publication title -
scandinavian journal of medicine and science in sports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.575
H-Index - 115
eISSN - 1600-0838
pISSN - 0905-7188
DOI - 10.1111/sms.12597
Subject(s) - cardiac output , microcirculation , skeletal muscle , cardiology , rest (music) , medicine , bed rest , cardiac muscle , blood flow , hemodynamics
In 1968, Saltin et al. published a landmark paper describing the alterations in VO 2max resulting from two sequential interventions – 20 days of bed rest and almost 8 weeks of training. They concluded that bed rest reduced VO 2max through reductions in maximal cardiac output, while training enhanced VO 2max by an equal combination of increased maximal cardiac output and increased arterio‐venous [O 2 ] difference (A‐V Δ [O 2 ]). At the time, A‐V Δ [O 2 ] was taken as an index of peripheral (skeletal muscle) adaptation. A key interpretive element that was not featured was consideration of how alterations in cardiac output affect the O 2 extraction process secondary to changes in red cell transit time through the muscle microcirculation, even in the absence of adaptive changes in the skeletal muscles per se. For the 2015 Saltin Symposium, it was therefore thought appropriate to re‐examine the 1968 O 2 transport data and re‐evaluate the roles central cardiovascular and peripheral muscle changes after bed rest and training allowing for their interaction. The analysis supports the conclusion that bed rest reduced VO 2max mainly through reduction in cardiac output, but after training, it is proposed that the 1968 conclusions should be modified: the majority of the increase in VO 2max from the control state can be attributed to an improvement in diffusive unloading of O 2 from the muscle microcirculation, with a much smaller role for enhanced blood flow.