Abstract
The purpose of the present study was to establish relationships between sprint front crawl performance and a swimming load-velocity profile. Fourteen male national-level swimmers performed 50 m front crawl and semi-tethered swimming with three progressive loads. The 50 m performance was recorded with a multi-camera system, with which two-dimensional head displacement and the beginning of each arm-stroke motion were quantified. Forward velocity (V50m), stroke length (SL) and frequency (SF) were quantified for each cycle, and the mean value of all cycles, excluding the first and last cycles, was used for the analysis. From the semi-tethered swimming test, the mean velocity during three stroke cycles in mid-pool was calculated and plotted as a function of the external load, and a linear regression line expressing the relationship between the load and velocity was established for each swimmer. The intercepts between the established line and the axes of the plot were defined as theoretical maximum velocity (V0) and load (L0). Large to very large correlations were observed between V50m and all variables derived from the load-velocity profiling; L0 (R = 0.632, p = 0.015), L0 normalized by body mass (R = 0.743, p = 0.002), V0 (R = 0.698, p = 0.006), and the slope (R = 0.541, p < 0.046). No significant relationships of SL and SL with V50m and the load-velocity variables were observed, suggesting that each swimmer has his own strategy to achieve the highest swimming velocity. The findings suggest that load-velocity profiling can be used to assess swimming-specific strength and velocity capabilities related to sprint front crawl performance.
Highlights
The shortest competitive swimming event is the 50 m freestyle, where the fastest swimmers finish in less than 21 s using the front crawl style
Given the extremely large correlation between the slope and L0 as well as the non-significant relationship between the slope and V0, it is very likely that the slope was strongly affected by L0, which means that the moderate-large association between the slope and V50m can be explained by the influence of L0. rL0 exhibited slightly stronger correlations with both V50m and t50m than L0
Assuming that the body mass of the subjects can be used as an indicator of their body size, the very large correlation is reasonable as a large body size does positively affect the propulsive force production and increase the resistive force (Kjendlie and Stallman, 2011), meaning that a large velocity can be achieved with a small propulsive force production if the swimmer has to overcome a small resistive force
Summary
The shortest competitive swimming event is the 50 m freestyle, where the fastest swimmers finish in less than 21 s using the front crawl style. During front crawl free-swimming phases, performance is determined by the ability to produce and maintain the highest forward swimming velocity This is achieved by maximizing and minimizing propulsive and resistive forces, respectively (Maglischo, 2003), and the propulsive force is linked to the ability to convert muscular to hydrodynamic forces. It is essential for swimmers to have both an ability to produce a large muscular force and proper technical skill to apply the force to the water (Maglischo, 2003). It has been of great interest for researchers to investigate relationships between on-land strength measurements and swimming performance. Among the two important factors suggested earlier (muscular force production ability and conversion of the muscular to hydrodynamic forces), establishing relationships between on-land strength training and swimming performance can only show the importance of the former factor but not the latter one
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