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The aim of this study was to examine the influence of leg kick on the pattern, the orientation and the propulsive forces produced by the hand, the efficiency of the arm stroke, the trunk inclination, the inter-arm coordination and the intra-cyclic horizontal velocity variation of the hip in sprint front crawl swimming. Nine female swimmers swam two maximal trials of 25 m front crawl, with and without leg kick. Four camcorders were used to record the underwater movements. Using the legs, the mean swimming velocity increased significantly. On the contrary, the velocity and the orientation of the hand, the magnitude and the direction of the propulsive forces, as well as the Froude efficiency of the arm stroke were not modified. The hip intra-cyclic horizontal velocity variation was also not changed, while the index of coordination decreased significantly. A significant decrease (13%) was also observed in the inclination of the trunk. Thus, the positive effect of leg kick on the swimming speed, besides the obvious direct generation of propulsive forces from the legs, could probably be attributed to the reduction of the body's inclination, while the generation of the propulsive forces and the efficiency of the arm stroke seem not to be significantly affected.

Aim: The aim of the study was to assess the acute effect of front crawl sprint resisted swimming on the inter-arm coordination and the fluctuation of the swimming velocity., Methods: Nine female swimmers swam four all-out trials of 25 m, without and with low, moderate and high added resistance. Four camcorders were used to record the underwater movement. The inter-arm coordination was quantified using the index of coordination and the hip intra-cyclic velocity variation was analysed by calculating the coefficient of variation and the difference between the maximum and minimum velocities normalized for the mean stroke cycle velocity., Results: One-way repeated measures analyses of variance showed that swimmers change their inter-arm coordination from a "catch up" toward an "opposition" mode. Concerning the hip horizontal intra-cyclic velocity variation, it was increased significantly during resisted swimming., Conclusion: These findings indicate that although resisted swimming cause an increase in the index of coordination and consequently it could be speculated a better propulsive continuity, the velocity fluctuations of the hip within a stroke cycle are not decreased, probably due to the inability of the swimmers to overcome effectively the concrete added resistances used in this study. Thus, at least concerning its acute effect, the hypothesis that the sprint resisted swimming could led to a technical improvement can not be satisfied.

To determine the time course of performance responses after an acute bout of plyometric exercise combined with high and low intensity weight training, a 3-group (including a control group), repeated-measures design was employed. Changes in performance were monitored through jumping ability by measuring countermovement and squat jumping, and strength performance assessment through isometric and isokinetic testing of knee extensors (at two different velocities). Participants in both experimental groups performed a plyometric protocol consisting of 50 jumps over 50 cm hurdles and 50 drop jumps from a 50 cm plyometric box. Additionally, each group performed two basic weight exercises consisting of leg presses and leg extensions at 90-95% of maximum muscle strength for the high intensity group and 60% of maximum muscle strength for the low intensity group. The results of the study suggest that an acute bout of intense plyometric exercise combined with weight exercise induces time-dependent changes in performance, which are also dependent on the nature of exercise protocol and testing procedures. In conclusion, acute plyometric exercise with weight exercise may induce a substantial decline in jumping performance for as long as 72 hours but not in other forms of muscle strength.

The aim of this study was to examine the acute effect of front crawl sprint resisted swimming with different added resistances on the kinematic characteristics of the stroke and the orientation of the hand. Ten female swimmers swam four maximal trials (25 m) with small, moderate, large, and no added resistance respectively. Four camcorders were used to record the underwater motion of the right hand and digitizing was undertaken using the Ariel Performance Analysis System. Stroke rate, the stroke length, and mean swimming velocity were significantly decreased, whereas the total duration of the stroke and the relative duration of the pull and push phases were significantly increased during resisted swimming. The increase in the total duration of the stroke was accompanied by an increase in absolute pull length, while no alterations were observed in relative pull length or medial-lateral displacements of the hand. Moreover, the mean resultant velocity of the hand, as well as the pitch and the sweepback angles of the hand were not modified. In conclusion, resisted swimming appears to be a specific form of training, at least regarding its acute effect, although long-term effects should be investigated further.

The aim of this research was to study the effect of hand paddles on the pitch, the sweepback angles and other stroke kinematic characteristics of the hand during front crawl swimming. Ten female competitive swimmers swam without and with small (116 cm (2)) and large (268 cm (2)) paddles. Four cameras (60 Hz) were used to record the underwater strokes and the digitizing was undertaken using the Ariel Performance Analysis System. When the size of the paddles increased, the stroke length, the mean swimming velocity and the total duration of the stroke were significantly increased (p < 0.05), while the average velocity of the hand during the pull and the push phases were significantly decreased (p < 0.05). The stroke rate was decreased significantly (p < 0.05) only when using large paddles. The relative duration of the separate phases of the stroke, the magnitude of the medial-lateral displacements and the pitch and sweepback angles of the hand were not modified, indicating that the use of hand paddles did not caused significant alterations in the orientation and the movement of the hand during the underwater stroke in front crawl swimming.