Biomechanics and Medicine in Swimming XI

Evaluation of Force Production and Fatigue using
an Anaerobic Test Performed by Differently Matured
Swimmers
soares, s., silva, r., Aleixo, I., Machado, l., Fernandes, r.J.,
Maia, J., Vilas-Boas, J.P.
University of Porto, Faculty of Sport, Cifi2d, Porto, Portugal
The purpose of this research was to characterize fatigue determining
thresholds in force-to-time curves produced during 30 second tethered
swimming efforts. Ninety swimmers of three maturational groups took
part in the study. Values of maximal, mean, and minimum force were determined,
as well as the variation coefficient of the mean force. The anaerobic
fatigue thresholds were determined on the individual force-totime
curves, and typical stroke cycles were determined before and after
the fatigue occurrence. Typical force cycles were quantitatively analysed.
It was possible to conclude that force tends to increase with maturation
in males. In females, tethered force seems to stabilize after puberty.
Key words: anaerobic performance, fatigue, force, tethered swimming
IntroductIon
Delaying fatigue is a desire in competitive swimming. In swimming,
the use of the anaerobic threshold concept has lead to the growth of
scientific knowledge applied to swimming training and seems to keep
up with performance evolution. That threshold establishes the border
between balanced and unbalanced lactate production and removal (maximal
full aerobic and partially anaerobically supported energy production).
Fatigue studies of anaerobic function and high power production
resisted exercises are not so well developed. It is not clear when fatigue
significantly emerges in those efforts and how to get useful information
for control and planning of anaerobic swimming training. In a previous
study from our group (Soares et al., 2003), we were able to study fatigue
and determine fatigue thresholds on velocity-to-time curves obtained in
30 second maximal efforts. Those findings made it possible to improve
the control over swimming planning and training in the anaerobic domain.
The purpose of the present study was to investigate fatigue and
determine fatigue thresholds in force-to-time curves produced during
30 second bouts of tethered swimming.
Methods
A total of 90 swimmers (Table 1) divided into three maturational groups
according to Tanner (Tanner, Whitehouse et al., 1962) performed a 30
second maximal tethered swimming test attached by a non-elastic cable
to a strain-gauge system (Globus, Italy). Previously to the starting signal,
swimmers adopted a horizontal position with the cable fully extended
starting the data collection only after the first stroke cycle was completed.
This procedure was used to avoid the inertial effect of the cable
extension usually produced immediately before or during the first arm
action. The end of the test was indicated by an acoustic signal. Video
images were captured during all the tests using a JVC camera (JVC GR-
Biomechanics SX1EG SVHSC), and Medicine and individual in Swimming force-to-time XI / Chapter 4 Training curves [F(t)] were Page pro- 128
duced for each session.
using a JVC camera (JVC GR-SX1EG SVHSC), and individual force-to-time curves
[F(t)] Table were 1. Anthropometric produced for each session. characteristics (mean±SD) and maturational
status.
Table 1. Anthropometric characteristics (mean±SD) and maturational status.
Swim level Pre-pub. - Pre-Competition Pub. - National Post-pub - Interational
M (n=15) F (n=15) M (n=15) F (n=15) M (n=15) F (n=15)
Age, years 9.42±0.82 8.45±0.94 13.51±0.65 12.65±0.98 18.18±2.35 16.54±2.35
Weight, kg 34.20±7.21 28.20±3.22 55.28±7.04 47.47±5.66 69.88±7.03 58.47±7.22
Height, cm 136.47±4.73 131.33±4.84 165.53±8.06 160.00±5.18 176.27±7.49 165.80±3.32
Ts: g - b 1.00±0.00 1.00±0.00 3.80±0.41 3.20±0.77 3.87±0.36 4.27±0.70
Ts: ph 1.00±0.00 1.00±0.00 4.13±0.64 4.00±1.00 4.73±0.46 4.80±0.68
Pre-pub: pre-pubertal; Pub: pubertal; Post-pub: post pubertal; M: males;
F: females; Ts: g – b: Tanner stage for genitalia or breast; Ts: ph: Tanner
stage for pubic hair.
The maximal (Fmax), mean (Fmean) and minimum (Fmin) force values were obtained
directly from the F(t) curve and normalized to body weight. The variation coefficient
(VC) of Fmean was calculated for each maturational group. Data treatment for fatigue
was performed using a routine based on a wavelet analysis, written by our research
group, in the MatLab software. The complete routine has already been described by
Soares et al. (2006). Before running the routine, the first 2 seconds of the test were
chaPter4.trainingandPerformance
The maximal (Fmax), mean (Fmean) and minimum (Fmin) force values
were obtained directly from the F(t) curve and normalized to body
weight. The variation coefficient (VC) of Fmean was calculated for each
maturational group. Data treatment for fatigue was performed using a
routine based on a wavelet analysis, written by our research group, in
the MatLab software. The complete routine has already been described
by Soares et al. (2006). Before running the routine, the first 2 seconds
of the test were removed in order to eliminate the initial peak force.
The routine allowed the determination of fatigue thresholds in each
individual F(t) curve and the time of occurrence. The intracyclic variation
of the force expressed through typical force cycles was established.
Typical force cycles were quantitatively analysed through: (i) total cycle
duration time (tcycle); (ii) stroke frequency (SF); (iii) mean cycle force
(FmeanC), and (iv) FmeanC VC. Due to technical problems, data of
intracyclic force variations are presented for pre-pubertal and pubertal
groups only.
Comparison of means between maturational groups was performed
through an ANOVA test for independent groups. Gender comparisons
were performed using a t-test for independent groups. Normal distribution
of data was verified. Significance level was 5%.
results
The Fmax, Fmean and Fmin values obtained for the male and female
swimmers of the three maturational groups studied can be observed in
Table 2. The forces produced during anaerobic tethered efforts seemed
Biomechanics and Medicine in Swimming XI / Chapter 4 Training Page 129
to increase with maturation, in contrast to VC which tends to decrease.
Table 2. Mean±standard deviation of maximal, mean and minimum
force values obtained during the 30 second tethered swimming test.
Table 2. Mean±standard deviation of maximal, mean and minimum force values
obtained during the 30 second tethered swimming test.
Fmax Fmean Fmin VC of Fmean
(%)
pre-pub M 0.74±0.27 0.63±0.22 0.55±0.22 66.57±17.55
Pre-pub F 0.66±0.21 0.56±0.18 0.46±0.16
pub M 1.50±0.14 a 1.32±0.11 a 1.16±0.10 a
52.86±11.36 a
pub F 1.34±0.40 1.20±0.36 a 1.06±0.32 a
post-pub M 1.82±0.23 *,a,b 1.62±0.20 *,a,b 1.43±0.19 *,a,b
46.53±7.67 a
Post-pub F 1.31±0.23 a 1.19±0.20 a 1.06±0.17 a
*
Significantly different from females at p