| At
first :
Every non aquatic mammal does hold its breath if submerged, but
man is abel to do this for a prolonged time, the way diving
mammals do like otter, beaver, seal, dolphin and whale.
It seems that we are also adapted to water during our evolutionary history, as is stated
in the "Aquatic Ape Theory" of Prof. Hardy (Oxford 1960) .
One of
these adaptations is the diving reflex. In diving, our heart beat
slows down
10 - 40 %, something that is not happening when we hold our breath
normally.
In general a slowing down with about 13 beats per minute is observed.
Tests
to show the diving reflex.
| A. |
Standing
on the platform, take your heart beat for 20 seconds and
multiply by 3. Repeat tree times.
|
=
|
____beats per minute
(mean) |
|
B.
|
The same, laying down on the platform |
=
|
____ beats per minute
|
|
C.
|
The same, floating horizontally, wit your face under water
. |
=
|
____ beats per minute
|
|
D.
|
Repeat standing on the bottom at the deepest point with
a lead girdle attached. |
=
|
____ beats per minute
|
Note:
In C. and D. a partner gives the signal for the start and end of
20 the second time lap by tapping the swimming pool ladder or by
slightly pulling a string, attached to the upper arm of the swimmer.
A divingclub can assist by using
assistant breathing under water.
- Question
1.
What is the difference between beats per minute in A. B. C. and
D?
Fill in the table below.
| Differences
in beats/minute |
A. |
B. |
C. |
D. |
| A. |
|
|
|
|
| B. |
|
|
|
|
| C. |
|
|
|
|
| D. |
|
|
|
|
- Question
2.
Find out what the advantages of the diving reflex are in active
diving.
- Question
3.
If your own observations are compared to the ones mentioned in
the illustration below, what are the conclusions about your achievement?
 |