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Testing Revised I
received complaints that the article ‘Testing”
which this article replaces was not well explained and the graphs not
legible. I fully agree with the criticism and realise that I did not
start at the beginning of this biomechanical exercise. So, I shall try
again with help from Prof David Costill’s “SWIMMING” a very clear
explanation from the beginning. A
method of assisting a swimmer’s stroke economy is by using the
following formulae, and using this information as a guide to
improvement. The
following measurements are required:
An
example of the above would be: A
swimmer swims 50m in 30 seconds and takes 25 strokes. V
= 50m. 30sec = 1.66 m.sec SR
= (25 strokes.30sec) x 60 = 50 s.min DS
= 50m.25 strokes = 2m per stroke. The
Stroke Index (SI) is calculated: V
x DPS = SI. This index
assumes that at a given
velocity, the swimmer who moves the greatest distance per stroke
has the most effective swimming technique. Especially over middle
distance 200m – 400m. The
illegible graphs were simply recording the above data from a test. A
further question has been raised: How do I use all these measurements? As
a swimmer increases pace there is a relationship between velocity,
distance per stroke, and stroke rate. An example of this is demonstrated
in a graph (also from ‘Swimming:)
showing the following relationships: (The
figures given are nearest) DPS
(metres. stroke) Stroke
Rate (strokes.min) Velocity
(metres.sec)
2.4
20
.75
2.3
25
1.0
2.1
35
1.2
1.9
43
1.4
1.8
55
1.7 It
is quite apparent that an increase in velocity is the product of a
decrease in stroke length and an increase in cycling rate. But it is
equally clear that there must be different combinations for different
distances. The combination for sprint events will not work for middle
distance. A
study by Prof Boomer, carried out over a number of years ‘Making
Finalists – A Matter of
Choices ‘ started by comparing finalists with non-finalists,
non-finalists being a group of swimmers whose times in any event ranged
between 93% and 97% of the average times of the finalists. There was a
significant difference in choices of combinations between the two
groups. The analysis of the various combinations forms the body of the
presentation. The
ability to adjust stroke rate and distance per stroke should be learned
as part of training and the Stroke Index will help to gauge the economy
of the combinations. I believe that this is one of the ways to use a Stroke Index. To
the last and final question: Don’t
think of how far you can reach with your arms over the water, that has
nothing to do with stroke length rather watch how far your head moves
through the water. Please have a look at my article Distance
per Cycle and Cycles per
Minute. The
‘anchoring’ of the arms at the catch is also called ‘holding the
water’. The catch is the point where pressure is first put on the
water to develop the pull/push. This point is about one- third of the
way through the underwater stroke. Dr
Ernie Maglischo writes:” The catch is that point in the underwater
stroke where propulsion begins. Most swimmers mistakenly believe that it
should take place immediately after their hands enter the water, this
belief has resulted in perhaps the most common stroke problem in
competitive swimming” Maglischo
cites one of the problems as a cause of the ‘dropped elbow’; I
believe that would depend upon the angle of entry. Trying to go straight
to the catch results in spinning and the loss of ‘feel’ at the point
of catch. The
hand and arm action just before the catch is one of the most interesting
developments at present. How
well a swimmer can hold the water is going to affect the distance per
stroke and may be a pointer to talent, as such a swimmer has more
choices. Of the choices made which have made dramatic results in success
when comparing two Olympic games results are: Increased distance per
stroke and reduced cycling rate; Increased distance per stroke and
cycling rate kept the same; Holding the same distance per stroke and
increasing the cycling rate and; Slight increase in distance per stroke
and a slight increase in cycling rate. In
this last combination, neither the difference in cycling rate nor the
distance per cycle was significant but when multiplied together they
made a significant velocity change. The researchers felt that this was a
very efficient method of increasing speed. |