Estudio de la potencia aplicada en nataciónsu relación con la potencia muscular, la técnica y su modificación con el entrenamiento

Resumen

Muscle power output is a critical issue in sport performance. Thus, since swim power is a reliable predictor of swim speed in front crawl, it is considered an important practical issue in swimming. Therefore, the main purposes of this thesis were to further investigate upper-limb swimming power output, to determine the relationships among swimming power, dry-land muscular power output and swimming velocity, and to assess the effect of power training on dry-land power and swimming performance. Despite the importance of swim power, a complete power curve (power vs. load) for swimming has not been described, and intra-cycle power has not been quantitatively assessed. In Chapter 2, intra-cycle power output during propulsive phases was examined. The maximum swimming power, the corresponding load and swimming speed were also determined. Eighteen male swimmers performed a swim power test for this purpose. It consisted of 12.5-m all-out swims using only the arms, with a load attached to the swimmer. A linear encoder and a load cell recorded intracycle speed and force, respectively, in each trial. The test was recorded with two underwater cameras. Intra-cycle power was obtained for propulsive stroke phases (pull: 60.32±18.87 W; push: 71.21±21.06 W). Mean maximum swim power was 66.49 W (0.86 W/kg), which was achieved at a swimming velocity of 0.75 m/s with a 47.07 % of the individual maximal load. Significant positive correlation (r = 0.76, p < 0.01) between maximum swim power and maximum swim speed was observed. These results suggested that the proposed test may be a useful training tool that is relatively simple to implement and would provide swimmers and coaches with quick feedback. The former protocol may be used in resisted swimming training to develop specific swim power. The continued use of resisted swimming in training may have, however, an effect on several swimming parameters. In Chapter 3, it was analysed to what extent the use of load during semi-tethered swimming modifies the freestyle stroke and coordination parameters, and it was examined whether those changes are positive or negative to swimming performance. First, behaviour of swim speed (v), stroke rate (SR) and stroke length (SL) with increasing load was examined. Secondly, mean and peak speed of propulsive phases (propvmean and propvpeak) were analysed, as well as the relative difference between them (%v). Finally, index of coordination (IdC) was assessed. The same sample and protocol as in Chapter 2 were used. Variables v and SL decreased significantly when load increased (p < 0.05), while SR remained constant. Propvmean and propvpeak decreased significantly with increasing load (p < 0.05). In contrast, %v grew when load rose (r = 0.922, p < 0.01), being significantly different from free swimming over 4.71 kg. For loads heavier than 4.71 kg, swimmers did not manage to keep a constant velocity during a complete trial. IdC was found to increase with load, significantly over 2.84 kg (p < 0.05). It was concluded that semi-tethered swimming is a useful training method to enhance swimmers¿ performance, although load needs to be individually determined and carefully controlled. It is accepted that power measured during swimming is a better predictor of swim velocity than power measured on dry-land exercises. In Chapter 4, dry-land power and swim power values were obtained by means of different methods. The relationships among dry-land power, swim power and swim velocity in each case were determined, and these relationships were compared between methods. The bench press power was higher than arm stroke power and swim power. Complete power vs. load curves were represented for bench press and semi-tethered swimming. High correlations were found between power on dry-land exercises and swim power, being higher for the arm stroke exercise. There was a high and significant correlation between swim velocity and swim power; it was high but not significant between swim velocity and arm stroke power, and moderate and almost significant between swim velocity and bench press power. This confirmed that swimming is the most specific way to measure swim power, although the arm stroke exercise may be a suitable dry-land alternative. However, despite muscular power being positively related to optimal performance, this does not necessarily indicate that training power will enhance swimming performance. The effects of an easy-to-implement dry-land power training program on arm muscular power were assessed in Chapter 5, and whether this resulted in faster sprint swimming was determined. Eight male swimmers performed dry-land power tests (bench press and bench pull) and swimming velocity tests (free, 2.5 kg, 5 kg, 7.5 kg) before and after a 7-week training period. The maximum propulsive power increased significantly on bench press (7.27±7.77 %, ES=0.60) and bench pull (7.52±6.99 %, ES=0.52) after seven weeks of training. Free swimming velocity increased significantly (15.59±6.61 %, ES=1.61), as well as when swimming pulling three different loads. Stroke rate decreased in free swimming, while stroke length was enhanced in every condition. These findings suggest that dry-land power training may be an effective method to complement and optimise swimming training. The results of this thesis evidence the important role of power in swimming, as it happens in many other sports.