Week 6 - Dallas Bedrest study

Question 1

What did this Dallas Bedrest study seek to investigate?

Answer 1

the influence of detraining followed by training on cardiovascular function

Question 2

What was the protocol for the study?

Answer 2

5 study participants
20 days bed-rest followed by 50 days training.

• 2 x daily Mon-Fri. 1 x Sat
• Continuous exercise 2.5 - 7 miles running
• Interval training 2-5 min running at near VO2max

Question 3

What happened to participants V02max with 20 days of bed-rest and 50 days training?

Answer 3

20days bed-rest: decreases in v02max as they began to lose the ability to take up and use oxygen.

50 days training: returned to resting levels and some participants vo2max went above their pre bed-rest values.

Question 4

What participants saw the greatest improvement in their V02max during the training stage of the study?

Answer 4

The unfit/sedentary participants - some had a v02max greater than their pre bed-rest value.

Question 5

What is Ficks equation?

Answer 5

Oxygen consumption = cardiac output X a-vo2 difference

Question 6

How did this study impact cardiac rehabilitation?

Answer 6

Rather than prescribing bed rest, cardiac rehabilitation now involves exercise rehabilitation when safe to do so.

Question 7

Following the training, how did participants HR, a-vO2 difference, CO and SV compared to after bed-rest?

Answer 7

HR lower at any given workload
CO + SV greater
a-vO2 difference increases sooner with BR

Question 8

What happened to SV after training? How does this compare to before the study?

Answer 8

SV improved with training and there is a linear increase in stroke volume with oxygen consumption.
This differs to before the study where SV starts to plateau at around 40% of their V02max. Therefore, you get a much greater cardiac output relative to control and bed-rest period.

Question 9

What happened to a-vo2 difference after training?

Answer 9

a-vo2 difference capacity was greater with training compared to control and bed-rest

Question 10

Why is there a higher oxygen uptake when sedentary (control) compared to after bed-rest? How can we explain the further increases in oxygen uptake after training?

Answer 10

Sedentary had higher oxygen uptake due to an increase maximal cardiac output relative to after-bed rest, caused by changes in SV (huge decrease after bed-rest).

Further increases with training is due to increase in cardiac output, caused by increased SV and changes in a-vo2 difference capacity.