1,721,107 research outputs found
The Decline of Swimming Performance With Advancing Age: A Cross-Sectional Study
No full textThe aim of this cross-sectional study was to measure the swimming parameters - speed (V), stroke frequency (SF), and stroke length (SL) - in 162 male athletes aged 50-90 (divided into 7 age groups, from A to G) participating in the World Master Championships in the 200-m freestyle event, and to analyze the rates and magnitudes of their age-associated declines. The swimmers were video-recorded by 2 digital cameras during the competitions and the swimming parameters related to every 50-m section (lap) and to the entire race (average) subsequently measured or calculated. Lap V and SF decreased in the second and third quarter (11 and 4% on average) and increased (3% on average) in the fourth quarter of the race, whereas lap SL decreased from the first to the last 50-m section. Average V (m·s-1) decreased from 1.39 ± 0.09 (group A) to 0.84 ± 0.11 (group G); average SL (m) decreased from 2.10 ± 0.20 (group A) to 1.78 ± 0.19 (group G); and average SF (cycles·s-1) decreased from 0.67 ± 0.06 (group A) to 0.47 ± 0.04 (group G). One-way analysis of variance showed significant declines in average V, SL, and SF (p < 0.01) across the 7 groups. The swimming parameters were normalized to the highest values (set equal to 100); thereafter, a linear regression curve was fitted and the regression equations calculated. Decline of SF was about 2.5 times steeper than that of SL. It was highlighted that (a) among the swimming parameters, SL is less affected by the ageing process; (b) SL decreased from group A through group C and thereafter tended to keep steady, whereas the trend for SF was opposite. The results have the potential to give master swimmers and their coaches useful information for training program desig
The energy cost of swimming and its determinants
No full textThe energy expended to transport the body over a given distance (C, the energy cost) increases with speed both on land and in water. At any given speed, C is lower on land (e.g., running or cycling) than in water (e.g., swimming or kayaking) and this difference can be easily understood when one considers that energy should be expended (among the others) to overcome resistive forces since these, at any given speed, are far larger in water (hydrodynamic resistance, drag) than on land (aerodynamic resistance). Another reason for the differences in C between water and land locomotion is the lower capability to exert useful forces in water than on land (e.g., a lower propelling efficiency in the former case). These two parameters (drag and efficiency) not only can explain the differences in C between land and water locomotion but can also explain the differences in C within a given form of locomotion (swimming at the surface, which is the topic of this review): e.g., differences between strokes or between swimmers of different age, sex, and technical level. In this review, the determinants of C (drag and efficiency, as well as energy expenditure in its aerobic and anaerobic components) will, thus, be described and discussed. In aquatic locomotion it is difficult to obtain quantitative measures of drag and efficiency and only a comprehensive (biophysical) approach could allow to understand which estimates are "reasonable" and which are not. Examples of these calculations are also reported and discussed
Effects of intra-cyclic velocity variations on the drag exerted by different swimming parachutes
No full textSwimming parachutes are often used as a tool for resisted swimming training. However, little is known on their behavior in terms of exerted drag as a consequence of intra-cyclic velocity fluctuations. This study aimed to assess the drag provided by two swimming parachutes of different shape, also characterized by different volumes and cross-sectional areas, under conditions of velocity variations in the range of those occurring in swimming. A flat square shaped parachute (FLAT, cross-sectional area and volume: 400 cm; 0.12 l) and a truncated cone shaped parachute (CONE, 380 cm; 7.15 l) were passively towed: 1) at constant velocities ranging from 1.0 to 2.2 m/s, and 2) with velocity fluctuations from 10 to 40 % around a mean of 1.6 m/s. At constant velocities, FLAT showed 0.1 N (at 1.0 m/s) to 10.8 N (at 2.2 m/s) higher drag than CONE. For both parachutes, the average drag showed trivial differences between constant and any fluctuating velocity. Conversely, the maximum drag values were higher under conditions of velocity fluctuations than the respective values estimated under stationary instantaneous velocity, although this was observed in CONE only. These findings suggest that swimmers and coaches can select the parachute characteristics based on whether the focus is on increasing/decreasing the average drag or regulating the maximum resistance provided
Evaluation of the Effectiveness of Compression Garments on Autonomic Nervous System Recovery After Exercise
Full text linkThe aim of this investigation was to evaluate the recovery pattern of a whole body compression garment on hemodynamic parameters and on ANS activity following a swimming performance. Ten young male athletes were recruited and tested in two different days, with and without wearing the garment during the recovery phase. After a warm-up of 15 minutes, athletes were instructed to perform a maximal 400m freestyle swimming event, and then time series of beat-to-beat intervals for heart rate variability (HRV), baroreflex sensitivity (BRS), and hemodynamic parameters were recorded for 90 minutes of recovery. The vagally mediated HF power of R-R intervals, NN50, and pNN50 showed a faster recovery due to the costume, meanwhile, the LFRR index of sympathetic modulation of the heart, as well as LF:HF ratio and BRS alpha index (αLF) were augmented in control than in garment condition. When athletes wore the swimsuit, cardiac output was increased and the returning of the blood to the heart, investigated as stroke volume, was kept constant due to the reduction of the total peripheral resistances. During control condition, HR was restored back to baseline value 20 minutes later with respect to garment condition, confirming that the swimsuit recover faster. The effectiveness of the swimsuit on ANS activity after a maximal aerobic performance has been shown with a greater recovery in terms of HRV and hemodynamic parameters. BRS was reduced in both conditions, maybe due to prolonged vasodilatation that may have also influenced the post-exercise hypotension
In water study of force-velocity and power-velocity relationships for water polo players
No full textRecovery time profiling after short-, middle- and long-distance swimming performance
No full textWe investigated cardiac autonomic responses and hemodynamic parameters on recovery time following short-, middle- and long-swimming performance. Ten male regional-level swimmers were tested to estimate time and frequency domains of arterial baroreflex sensitivity and heart rate variability after 100-, 200-, and 400-m of front crawl. We found a BRS reduction for 90 min after a maximal 100- and 200-m front crawl event, meanwhile the reflex was restored back to the baseline value about 70 min after 400-m. The vagally mediated HF power of R-R intervals was significantly reduced for 30 min after 400-m, and more than 90 min after 100- and 200-m, with a concomitant increase of sympathetic modulation. After 400-m athletes have reduced their stroke volume for 50 min, which remained at the baseline level following 100- and 200-m. HR was restored back after 90 min in all conditions, whereas TPR was significantly reduced for 50 min after 200- and 400-m, with a persistent reduction after 100-m. Time course of autonomic recovery after 3 different swimming performances is influenced by exercise intensity and duration, showing a rapid recovery after 400-m, an intermediate recovery after 200-m, and a significantly delayed recovery after a more strictly anaerobic performance like 100-m of front crawl. These results could encourage coaches to consider that athlete might be affected by the specific recovery time of the previous exercise performed, suggesting that the management of the exercise intensity, and appropriate monitoring of cardiac autonomic parameters might be helpful to know the physical condition of each athlete
The effect of swim-cap surface roughness on passive drag.
No full textIn the last decade, great attention has been given to the improvements in swimming performance that can be obtained by wearing "technical swimsuits"; the technological evolution of these materials only marginally involved swim caps production, even if several studies have pointed out the important role of the head (as main impact point with the fluid) on hydrodynamics. The aim of this study was to compare the effects on passive drag (Dp) of 3 swim cap models: a smooth silicon helmet cap (usually used during swimming competitions), a silicon helmet cap with "dimples," and a silicon helmet cap with "wrinkles." Experiments were performed on 10 swimmers who were towed underwater (at a depth of 60 cm) at 3 speeds (1.5, 1.7, and 1.9 m·s) and in 2 body positions: LA (arms above the swimmer's head) and SA (arms alongside the body). The Dp values obtained in each trial were divided by the square of the corresponding speed to obtain the speed-specific drag (the k coefficient = Dp/v). No differences in k were observed among swim caps in the LA position. No differences in k were observed between the smooth and dimpled helmets also in the SA position; however, the wrinkled swim cap helmet showed a significant larger k (4.4%) in comparison with the model with dimples, when the swimmers kept their arms alongside the body (in the SA position). These data suggest that wearing a wrinkled swim cap helmet can be detrimental to performance at least in this specific position
Wearable inertial sensors in swimming motion analysis: a systematic review
No full textThe use of contemporary technology is widely recognised as a key tool for enhancing competitive performance in swimming. Video analysis is traditionally used by coaches to acquire reliable biomechanical data about swimming performance; however, this approach requires a huge computational effort, thus introducing a delay in providing quantitative information. Inertial and magnetic sensors, including accelerometers, gyroscopes and magnetometers, have been recently introduced to assess the biomechanics of swimming performance. Research in this field has attracted a great deal of interest in the last decade due to the gradual improvement of the performance of sensors and the decreasing cost of miniaturised wearable devices. With the aim of describing the state of the art of current developments in this area, a systematic review of the existing methods was performed using the following databases: PubMed, ISI Web of Knowledge, IEEE Xplore, Google Scholar, Scopus and Science Direct. Twenty-seven articles published in indexed journals and conference proceedings, focusing on the biomechanical analysis of swimming by means of inertial sensors were reviewed. The articles were categorised according to sensor's specification, anatomical sites where the sensors were attached, experimental design and applications for the analysis of swimming performance. Results indicate that inertial sensors are reliable tools for swimming biomechanical analyses
Estimating active drag based on full and semi-tethered swimming tests
No full textDuring full tethered swimming no hydrodynamic resistance is generated (since v = 0) and all the swimmer's propulsive force (F-P) is utilized to exert force on the tether (F-T = F-P). During semitethered swimming FP can be made useful to one of two ends: exerting force on the tether (F-ST) or overcoming drag in the water (active drag: Da). At constant stroke rate, the mean propulsive force (F-P) is constant and the quantity F-P - F-ST (the "residual thrust") corresponds to Da. In this study we explored the possibility to estimate Da based on this method ("residual thrust method") and we compared these values with passive drag values (Dp) and with values of active drag estimated by means of the "planimetric method". Based on data obtained from resisted swimming (full and semi-tethered tests at 100% and 35, 50, 60, 75, 85% of the individual F-T), active drag was calculated as: Da(ST) = kaST .v(ST)(2 )= F-P - F-ST ("residual thrust method"). Passive drag (Dp) was calculated based on data obtained from passive towing tests and active drag ("planimetric method") was estimated as: D-aPL = Dp.1.5. Speed-specific drag (k = D/v(2)) in passive conditions (kp) was approximate to 25 kg.m(-1) and in active conditions (ka) approximate to 38 kg.m(1) (with either method); thus, D-aST > D-p and D-aST approximate to D-aPL. In human swimming active drag is, thus, about 1.5 times larger than cal setting (in the swimming pool) by using basic instrumentation and a simple set of calculations
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