Biomechanics and Medicine in Swimming XI

Repeated measures general linear modelling tests were used to compare
the changes in the relative durations of the Entry and Glide, Pull, Push
and Recovery phases between the affected and unaffected arms and between
the percentage swimming speeds. In all comparisons, the level of
statistical significance was set at p < .05.
results
There were significant differences (p < .05) between the affected- and
unaffected-arm for the relative durations of each arm stroke phase across
the five percentage speed increments (Fig. 2). The affected-arm on average
spent relatively longer in all arm stroke phases, with the exception of
the Pull phase, when compared to the unaffected-arm.
The mean relative duration of the Entry and Glide phase (A) for the
affected and unaffected arms did not significantly change as the participants
increased their swimming speed. While the unaffected-arm’s relative
Entry and Glide phase duration remained relatively constant (23.2
± 8.0% vs. 23.1 ± 6.8%, for 80% and 100% of SS max respectively) with an
increase in swimming speed, there was a slight reduction in the affectedarm’s
relative Entry and Glide phase duration between 80% and 100% of
SS max (38.3 ± 9.5% vs. 36.2 ± 11.6%).
The mean relative duration of the Pull phase (B) for the unaffectedarm,
but not for the affected-arm, changed significantly (p < .05) as the
participants increased their swimming speed. While the affected-arm’s
relative Pull phase duration remained relatively unchanged (10.9 ± 2.8%
vs. 11.0 ± 2.3%, for 80% and 100% of SS max respectively) with an increase
in swimming speed, there was a significant reduction (p < .05)
in the unaffected-arm’s relative Pull phase duration between 80% and
100% of SS max (23.1 ± 5.9% vs. 20.5 ± 4.9%).
The mean relative duration of the Push phase (C) for both the affected
and unaffected arms changed significantly (p < .05) as the participants
increased their swimming speed. At 80% of SS max , the mean Push
phase durations were 18.4 ± 6.4% and 13.8 ± 2.7% for the affected- and
unaffected-arm respectively. At 100% of SS max , the mean Push phase
durations were 19.4 ± 5.3% and 15.4 ± 3.9% for the affected- and unaffected-arm
respectively.
The mean relative duration of the Recovery phase (D) for the affected
and unaffected arms did not significantly change as the participants
increased their swimming speed.
Figure 2. Means and standard deviations of relative arm stroke phase
durations for both the affected- and unaffected-arms (* Differences
between arms are statistically significant p < .01). Bold bars indicate
affected-arm.
dIscussIon
The purpose of this study was to determine whether the arm stroke
phases used by competitive unilateral arm amputee front crawl swim-
chaPter2.Biomechanics
mers differed between their affected and unaffected sides and whether
these phases changed with an increase in swimming speed.
At all swimming speeds, the stroke phases of the affected and unaffected
arms differed significantly. Whilst all swimmers pulled their affected-arm
through the water fastest, the affected-arm on average spent
relatively longer in all arm stroke phases, with the exception of the Pull
phase, when compared to the unaffected-arm. Unfortunately, it is not
possible to directly compare these findings with those for able-bodied
swimmers or other swimmers with various loco-motor disabilities, since
arm stroke phases are only reported in the literature as mean values of
both arms (e.g., Chollet et al., 2000; Potdevin et al., 2006; Satkunskiene
et al., 2005).
As a consequence of their physical impairment, at all swimming
speeds the arm amputees used an asymmetrical strategy for coordinating
their affected-arm movement with their unaffected-arm. It was apparent
that the amputees held their affected-arm stationary in the Entry
and Glide phase before pulling it rapidly under the shoulder. As the
affected-arm was then pushed towards the hip, its motion slowed before
the Recovery phase commenced. Conversely, the amputees’ unaffectedarm
moved steadily though the Entry and Glide phase and the Pull
phase before being rapidly pushed into the Recovery phase. Such different
bi-lateral motor control strategies might be linked to how these
swimmers learnt to organise the motor skills necessary to swim front
crawl.
As swimming speed increased the relative durations of certain arm
stroke phases changed. With increasing speed: 1) the affected-arm’s Entry
and Glide phase decreased, while the unaffected-arm’s Entry and
Glide phase remained unchanged; 2) the unaffected-arm’s Pull phase
decreased, while the affected-arm’s Pull phase remained unchanged; and
3) both arms’ Push phase increased. Both Chollet et al. (2000) and Potdevin
et al. (2006) showed that for able-bodied swimmers, the relative
duration of the Entry and Catch phase (mean of both arms) decreased,
while the relative durations of the Pull and Push increased with increasing
swimming speed. The authors suggested that in making these adaptations,
able-bodied swimmers were able to take advantage of longer
periods of propulsive force application. In the current study propulsion
was not measured. However, as a consequence of task (e.g., swimming
faster), physical (e.g., single-arm amputation) and environmental (e.g.,
larger resistive forces at higher speeds) constraints, the unilateral arm
amputee front crawl swimmers asymmetrically adjusted their arm movements
to maintain the stable repetition of the overall arm stroke cycle.
conclusIon
The results from this study show that at all swimming speeds the stroke
phases of the affected and unaffected arms differed significantly. The
affected-arm on average spent relatively longer in all arm stroke phases,
with the exception of the Pull phase, when compared to the unaffected
arm. Such differences might be linked to how these swimmers learnt
to organise the motor skills necessary to swim front crawl. As swimming
speed increased, the duration of the affected-arm’s Entry and
Glide phase and the unaffected-arm’s Pull phase significantly decreased,
while the duration of both arms’ Push phase significantly increased. The
arm amputees used a coordination strategy that asymmetrically adjusted
their arm movements in order to maintain the stable repetition of their
overall arm stroke cycle when swimming at different speeds.
reFerences
Chollet, D., Chalies, S., & Chatard, J.C. (2000). A new index of coordination
for the crawl: Description and usefulness. International Journal
of Sports Medicine, 21(1), 54-59.
Maglischo, C.W., Maglischo, E.W., Higgins, J., Hinrichs, R., Luedtke,
D., Schleihauf, R.E., & Thayer, A. (1988). A biomechanical analysis
of the 1984 U.S. Olympic freestyle distance swimmers. In B.E. Ungerechts,
K. Wilke, K. Reischle (Eds.), Swimming Science V, Champaign,
IL: Human Kinetics, 351-360.
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