L35 Microgravity and Bed rest

Question 1

Describe the design of the Dallas Bed-Rest Study

Answer 1

meh no

Question 2

Explain how VO2max, cardiac output, stroke volume, heart rate and a-vO2 difference were influenced by
20 days of bed-rest followed by 50 days of exercise training in the Dallas study.

Answer 2

Vo2 max reductions closely associated with reduction in heart volume.
Higher heart rate at a given work rate compared to control for bed rest. Same for A-V O2 and cardiac output is lower

Question 3

List four strategies used to simulate microgravity

Answer 3

• Head-down bed rest
• Wheelchair
• Immobilization
• Parabolic flight

Question 4

Explain how spaceflight influences aerobic exercise capacity (VO2max) and orthostatic tolerance

Answer 4

• reduces exercise capacity. Induces an orthostatic intolerance.
  Microgravity –:> reduced hydrostatic gradient –> head wards shift of leg fluid –> increases GFR, decreased ADG and water reabsorption –> diuresis –> reduced blood volume –> orthostatic tolerance

Question 5

Describe the effects of spaceflight on:
o Cardiac mass
o Stroke volume
o Plasma volume
o Red blood cell mass
o Haemoglobin
o Bone mineral density

Answer 5

o Cardiac mass
- 20 loss mass from the left ventricle
o Stroke volume
- falls 
o Plasma volume
- reduction in plasma volume 
o Red blood cell mass
- red blood cell mass decreases
o Haemoglobin
- over all total decreases
o Bone mineral density
- demineralization . crew lost 11% of their total hip bone mass over the course of their mission

Question 6

Outline the changes in skeletal muscle mass, strength, explosive power, fibre type and enzyme levels with
spaceflight

Answer 6

Muscle mass and strength decrease with microgravity
- Maximal explosive power similarly reduced with microgravity
Muscle fibre type changes with microgravity
- More loss of CSA of type II fibres than type I but they both decrease.
- Greater proportion of type II fibres

Question 7

Explain why exercise training and fluid loading are valuable countermeasures to the deleterious effects of
spaceflight on physical performance and orthostatic tolerance

Answer 7

Less depletion of VO2 max - preservation of aerobic capacity

Question 8

Graph the time course of changes in cardiovascular function, body fluids, bone mass and skeletal muscle
with microgravity exposure

Answer 8

In the lecture slides.

Cardiac index of deconditioning increases. Everything else decreases.