Objectives: This work provides a reference for future papers originating from this study by providing basic results on body mass, urine volume, and hemodynamic changes to 5 days of bed rest (BR) and by describing acute cardio-respiratory/mechanographic responses to a short versatile upright exercise battery.
Methods: Ten male subjects (mean ± SEM age: 29.4 ± 1.5 years; height: 178.8 ± 1.5 cm; body mass: 77.7 ± 1.5 kg) performed, in random order, 5 days of 6° head-down tilt (HDT) BR with no exercise (CON), or BR with daily 25 minutes of quiet upright standing (STA) or upright locomotion replacement training (LRT).
Results: Plasma volume, exercise capacity and orthostatic tolerance decreased similarly between interventions following 5 days of BR. Upright heart rate during LRT and STA increased throughout BR; from 137 ± 4 bpm to 146 ± 4 bpm for LRT (P<0.01); and from 90 ± 3 bpm to 102 ± 6 bpm (P<0.001) for STA.
Conclusion: the overall similarity in the response to BR, and increase in upright heart rate during the LRT sessions suggest early and advancing cardiovascular deconditioning during 5 days of BR bed rest, which was not prevented by the versatile exercise regime.