Biomechanics and Medicine in Swimming XI

the ankles during 25 to 800 m all-out trials. It is likely that the larger
increase in speed found in our study is due to the fabric composition
of the suits from Bluesevnty TM , made of 75% nylon and 25% PU-CR
(polyurethane that improves buoyancy), in contrary to the polyester and
lycra composition of the FastSkin TM .
Parsons and Day (1986) and Cordain and Kopriva (1991) analyzed
the effects of wetsuits, allowed in triathlon competitions and made of
low-density material, which is similar to the bodysuits analyzed in our
study. The authors suggested that the performance enhancement was directly
related to the improved buoyancy offered by the suit. According to
Benjanuvatra et al. (2002), improved buoyancy allows a smaller energetic
cost to sustain an optimal body position, and therefore greater force can
be applied on generating propulsion.
In the present study, the increase in speed was due to an increase in
stroke length, since there was no difference in the stroke rate when using
the bodysuit. Roberts et al. (2003) found similar results when comparing
front crawl swimming using the Speedo Fastskin TM to ordinary suits.
These authors, however, analyzed sub-maximal swimming intensities.
Chatard and Wilson (2008) found a significant decrease of the energetic
cost associated with an increase of the stroke length when using
the Fastskin TM body suit, which means improved swimming economy.
Our subjects showed a shorter duration of the entry and catch phase
during the second split of the trial when using the bodysuits, resulting
in a significant decrease in the duration of the non-propulsive stroke
phase. This result took us to believe in a possible influence on the index
of coordination, which was not confirmed. This result is in accordance
with the ones presented by Hue et al. (2003) who found differences in
the index of coordination when using a triathlon wetsuit only when analyzing
long distance races, with no differences found during swimming
at velocities similar to the 100 m and 50 m races.
Analyzing the subjects individually, five subjects showed a similar
index of coordination on both suit situations and one subject showed
a greater continuity between the propulsive actions during the first 25
m split. During the second split four out of the six subjects showed a
greater continuity of the propulsive phases using the suit and the other
two did not change their index of coordination values. This suggests that
the suit may have a greater influence on technique during the final portion
of the race.
Since the suit did not interfere with the duration of the propulsive
phase of the stroke, the greater stroke length is probably as a result
of more effective force application during the phase probably due
to a decrease in drag. The propulsive effectiveness is dependent on the
combination of a high displacement speed of the hand and its adequate
trajectory during the propulsive phase, generating higher peak forces
(Toussaint & Beek, 1992).
It was not possible to evaluate the body compression caused by the
suit, if any, and this is a limitation of this study. However, the subjects
reported difficulties to put on the suits, taking a long time dress them
properly. Kainuma (2009) suggests that the compression of the LZR
Racer TM from Speedo, can modify the physiological systems by an alternative
mechanism, where the compression would affect the blood circulation,
forcing the use of anaerobic-glycolitic pathways. This would in
turn enable an instantaneous increment in force generation, which could
have some influence on short distance, more high-speed races.
Even though we randomized the tests order and tried to verbally
stimulate the athletes the same way on both trials, a possible placebo
effect could not be controlled for.
conclusIon
Wearing a full bodysuit, covering from the shoulders to the ankles, from
Blueseventy TM , significantly improves the swimming speed during an
all-out 50 m front crawl swimming trial, mostly on the second half of
the test. When wearing the suits, the subjects showed a greater stroke
length during both 25 m splits and shorter duration of the non-propulsive
phase of the arm stroke during the second half of the test.
chaPter2.Biomechanics
reFerences
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AcKnoWledGeMents
The authors want to express their gratitude to the athletes and coaches
from Grêmio Náutico União, for the contribution in this study, and to
Aquatic Sports Research group for their cooperation.
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