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- Understanding the importance of drag coefficient assessment for a deeper insight into the hydrodynamic profile of swimmersPublication . Morais, J.E.; Marinho, D.A.; Bartolomeu, Raúl Filipe; Barbosa, Tiago M.The main objective of this study was to confirm that the passive drag coefficient is less dependent on swimming speed than the passive drag, Froude, and Reynolds numbers, even as swimming speed increases. The sample consisted of 12 young proficient non-competitive swimmers (seven males and five females: 20.4 ± 1.9 years). Passive drag was measured with a low-voltage isokinetic engine at 1.2, 1.4, 1.6 and 1.8 m/s. The frontal surface area was measured using digital photogrammetry. Passive drag showed significant differences with a strong effect size over the four towing speeds measured (F = 116.84, p < 0.001, η2 = 0.91) with a quadratic relationship with speed. The Froude and Reynolds numbers had similar trends, but with linear relationships. Conversely, the passive drag coefficient showed non-significant differences across the four towing speeds (F = 3.50, p = 0.062, η2 = 0.33). This strongly suggests that the passive drag coefficient should be the variable of choice for monitoring the hydrodynamic profile of swimmers rather than the absolute value of passive drag.
- Underwater and surface tethered swimming, lower limb strength, and somatic traits as the basic indices of young swimmers’ sprint performancePublication . Sokołowski, Kamil; Bartolomeu, Raúl Filipe; Krężałek, Piotr; Bragada, José A.; Pałka, Tomasz; Ambroży, Dorota; Strzała, MarekPurpose: The ability to swim fast underwater is believed to be connected to lower limb strength and some somatic traits. The main purpose of the study was to evaluate strength and speed parameters based on the relationship between the strength of underwater dolphin kicks and the countermovement jump test (CMJ) among adolescent swimmers. Methods: 48 adolescent male swimmers (13.47 +/- 0.84 years) were examined for muscle mass of arms (mm arms), trunk (mm trunk), and legs (mm legs), body height (BH), and biological age (BA). An underwater tethered dolphin kicking test was conducted in a pool; average force (5Fave) and impulse per single cycle (5Iave) in the 5-second period were measured. Force indices (20Fave - average force from 20 seconds and 20Iave - average impulse per single cycle from 20 seconds) were also measured in 20-second tethered front crawl swimming. During CMJ testing, general lower body muscle motor capabilities were evaluated by extracting the work (CMJw [J]) and height (CMJh [m]) of the jump. Results: The strongest correlations were observed between: (a) 5Fave and BH, mm arms and CMJw; (b) CMJw, mm arms, and 20Fave; (c) indices of swimming speed and 5Iave (BA control); (d) total swimming velocity and average tethered swimming force (BA control). Moderate partial correlations (BA control) were noted between speed indices of swimming race and CMJ. Conclusions: The underwater tethered dolphin kick test is a useful predictor test of 50-m front crawl performance in young male swimmers, with better specificity for swimmers than CMJ results themselves.
- Association between the upper quarter dynamic balance, anthropometrics, kinematics, and swimming speedPublication . Bartolomeu, Raúl Filipe; Sampaio, Tatiana; Oliveira, João P.; Barbosa, Tiago M.; Morais, J.E.Besides recurrently assessed water-based parameters, there are also some individual characteristics that affect swimming performance that are not water related. In the past few years, dynamic balance has been associated with land sports performance. Conversely, evidence on this topic in swimming is scarce. The purpose of this study was to assess the association between on-land dynamic balance and swimming performance. Sixteen young adults and recreational swimmers were recruited for the present study (8 males 20.8 2.0 years, and 8 females 20.1 1.9 years). A set of anthropometric features were measured. The upper quarter Y-balance test was selected as a dynamic balance outcome, and swimming speed as the swimming performance indicator. The results showed a moderate and positive correlation between dynamic balance and swimming performance (p < 0.05). Speed fluctuation was highly and negatively related to swimming speed (p < 0.001), i.e., swimmers who had higher scores in the dynamic balance were more likely to deliver better performances. This suggests that in recreational swimmers, the stability and mobility of the upper extremity had a greater influence on swimming performance. Therefore, swimming instructors are advised to include dynamic balance exercises in their land-based training sessions to improve their swimmers’ performance
- Net Heart Rate for Estimating Oxygen Consumption in Active AdultsPublication . Bragada, José A.; Magalhães, Pedro; São-Pedro, Eric; Bartolomeu, Raúl Filipe; Morais, J.E.The aim of this study was to verify the accuracy of predicting oxygen consumption (O-2) in predominantly aerobic activities based on net heart rate (netHR), sex, and body mass index (BMI) in active adults. NetHR is the value of the difference between the resting HR (HRrest) and the average HR value obtained during a given session or period of physical activity. These activities must be continuous, submaximal, and of a stabilized intensity. The magnitude of the netHR depends mainly on the intensity of the exercise. The HR is measured in beats per minute (bpm). A total of 156 participants, 52 women and 104 men, between the ages of 18 and 81, had their netHR and net oxygen intake (netVO(2)) assessed. There were 79 participants in group 1 (prediction sample) (52 males and 27 females). There were 77 people in group 2 (validation sample) (52 males and 25 females). The results of the multiple linear regression showed that netVO(2) (R-2 = 85.2%, SEE = 3.38) could be significantly predicted by sex (p < 0.001), netHR (p < 0.001), and BMI (p < 0.001). The Bland-Altman plots satisfied the agreement requirements, and the comparison of the measured and estimated netVO(2) revealed non-significant differences with a trivial effect size. We calculated the formula NetVO(2) (mL/(kgmin)) = 16 + 3.67 (sex) + 0.27 (netHR) - 0.57 (BMI) to predict netVO(2), where netVO(2) is the amount of oxygen uptake (mL/(kgmin)) above the resting value, netHR is the heart rate (beats per minute) above the resting value measured during exercise, sex is equal to zero for women and one for men, and BMI is the body mass index. In addition, based on the knowledge of VO2, it was possible to estimate the energy expenditure from a particular training session, and to determine or prescribe the exercise intensity in MET (metabolic equivalent of task).
- Nonlinear Analysis of the Hand and Foot Force-Time Profiles in the Four Competitive Swimming StrokesPublication . Bartolomeu, Raúl Filipe; Rodrigues, Pedro; Sokołowski, Kamil; Strzała, Marek; Santos, Catarina C.; Costa, M.J.; Barbosa, Tiago M.Human locomotion on water depends on the force produced by the swimmer to propel the body forward. Performance of highly complex motor tasks like swimming can yield minor variations that only nonlinear analysis can be sensitive enough to detect. The purpose of the present study was to examine the nonlinear properties of the hand/feet forces and describe their variations across the four competitive swimming strokes performing segmental and full-body swimming. Swimmers performed all-out bouts of 25 m in the four swimming strokes, swimming the full-body stroke, with the arm-pull only and with the leg kicking only. Hand/foot force and swimming velocity were measured. The Higuchi's fractal dimension (HFD) and sample entropy (SampEn) were used for the nonlinear analysis of force and velocity. Both the arm-pull and leg kicking alone were found to produce similar peak and mean hand/foot forces as swimming the full-body stroke. Hand force was more complex in breaststroke and butterfly stroke; conversely, kicking conditions were more complex in front crawl and backstroke. Moreover, the arm-pull and kicking alone tended to be more complex (higher HFD) but more predictable (lower SampEn) than while swimming the full-body stroke. There was no loss of force production from segmental swimming to the full-body counterpart. In conclusion, the number of segments in action influences the nonlinear behavior of the force produced and, when combining the four limbs, the complexity of the hand/foot force tends to decrease.