Resistive exercise versus resistive vibration exercise to counteract vascular adaptations to bed rest

Abstract

Bed rest results in marked vascular adaptations, and resistive vibration exercise (RVE) has been shown to be an effective countermeasure. As vibration exercise has practical and logistical limitations, the use of resistive exercise (RES) alone has the preference under specific circumstances. However, it is unknown if RES is sufficient to prevent vascular adaptations to bed rest. Therefore, the purpose of the present study was to examine the impact of RES and RVE on the vascular function and structure of the superficial femoral artery in young men exposed to 60 days of bed rest. Eighteen healthy men (age: 31 +/- 8 yr) were assigned to bed rest and randomly allocated to control, RES, or RVE groups. Exercise was applied 3 times/wk for 5-7 min/session. Resting diameter, blood flow, flow-mediated dilation (FMD), and dilator capacity of the superficial femoral artery were measured using echo-Doppler ultrasound. Bed rest decreased superficial femoral artery diameter and dilator capacity (P < 0.001), which were significantly attenuated in the RVE group (P < 0.01 and P < 0.05, respectively) but not in the RES group (P = 0.202 and P = 0.696, respectively). Bed rest significantly increased FMD (P < 0.001), an effect that was abolished by RVE (P < 0.005) but not RES (P = 0.078). Resting and hyperemic blood flow did not change in any of the groups. Thus, RVE abolished the marked increase in FMD and decrease in baseline diameter and dilator capacity normally associated with prolonged bed rest. However, the stimulus provided by RES alone was insufficient to counteract the vascular adaptations to bed rest.

Impact of Bed Rest on Conduit Artery Remodeling

“…Offline analysis was performed using custom-designed wall-tracking software, which is independent of investigator bias, 21,22 by an experienced sonographer who was blinded to group allocation. Briefly, the initial video signal was encoded and stored as a digital DICOM file on a personal computer, using an IMAQ-PCI-1407 card.…”

“…47,48 Because the magnitude of physical inactivity is time dependent, 49 60 days clearly resulted in a large impact on the vasculature. The profound stimulus of complete bed rest, 49 combined with the excellent reproducibility of our technique, 22 allowed us to detect these important findings in a relatively small group of participants. It should also be emphasized that bed rest such as that used in the present experiment does not represent a sedentary lifestyle, and our findings cannot necessarily be extrapolated to those of sedentary, yet ambulatory, individuals.…”

“…Indeed, previous studies found that vibration exercise during bed rest amplifies exercise gains in skeletal muscle morphology and function. 21 Moreover, others found that vibration exercise involving a resistive component at least partly prevents detrimental changes in vascular function 4,22 and structure. 4,22,23 However, no previous studies have examined the potential of exercise countermeasures to prevent changes in artery wall characteristics associated with chronic bed rest.…”

“…21 Moreover, others found that vibration exercise involving a resistive component at least partly prevents detrimental changes in vascular function 4,22 and structure. 4,22,23 However, no previous studies have examined the potential of exercise countermeasures to prevent changes in artery wall characteristics associated with chronic bed rest. To examine this, we assessed the impact of countermeasures involving resistive exercise alone, or in combination with vibration, on carotid and superficial femoral arterial wall thickness and wall:lumen ratio before and after 60 days of bed rest in healthy, young volunteers.…”

Low-magnitude whole body vibration with resistive exercise as a countermeasure against cardiovascular deconditioning after 60 days of head-down bed rest

“…Whole body vibration has been proposed as a countermeasure to prevent muscle and bone deconditioning induced by bed rest and an environment of weightlessness (2). A recent study (41) compared the effects of whole body vibration associated with resistive exercise versus resistive exercise alone on the vascular changes induced by 60-day bed rest. In that study, the combined countermeasure prevented superficial femoral artery diameter and flow-mediated dilation changes induced by bed rest, whereas resistive exercise alone was insufficient to prevent those macrocirculatory changes.…”