Swimming performance is a multi-factorial phenomenon depending on several factors such as energetics, biomechanics, hydrodynamics, anthropometries and strength parameters (Poujade et al. 2002; Barbosa et al. 2009). Considering that heavy training loads start at relatively young ages, it seems important to assess which parameters best predict swimming performance. In a longitudinal study, Tella et al. (2002) reported that the improvement observed in young swimmers performance results from an increase in stroke length (SL), which reflects, in part, the increase of anthropometrical characteristics (arm span, height and hands and feet length). Similarly, Chatard et al. (1990) stated that performance is related to passive drag, which depends on anthropometric factors. More recently, in a swimming performance's multivariate analysis, it was found that higher height and arm span, characterised the best male swimmers (Saavedra et al. 2010). Other studies found similar results (e.g. Uitt et al. 2010; Geladas et al. 2005), allowing researchers to conclude that usually higher height and arm span benefits swimming efficiency (i.e. higher SL) (Saavedra et al. 2010) and a better glide (Geladas et al. 2005; Toussaint and Hollander 1994). However, this larger SL could be also related to a hyperflexibility presented by swimmers, which benefit the glide and create less resistance (they could streamline their body to a greater extent). This contributes to a more laminar and less turbulent flow around the pressure points, such as the shoulder, hip, knee, ankle, where most of the changes in body shape occur (Chatard et al. 1990). Many sports depend mainly upon muscular strength and aerobic enhancement especially at a competitive level (Leverittet al. 2000), as in swimming. In fact, studies showed positive effect of dryland upper limb strength training, varying the gains in sprint performance between 1.3 and 4.4% (Strass 1988; Costill1999). Regarding young swimmers, it was noticed that the significant increase in velocity between 12 to 14 years old is coincided with a significant increase in the mean force production (Taylor et al. 2003). Moreover, strength training could allow the enhancement in coordinative profile, helping the swimmer to improve his/her technique (Maglischo 2003). In fact, when competitive young swimmers are involved in strength training, to take full benefit of an increase in muscle strength, coordination needs to be adapted (Newton et al. 2002). The swimmer has to modify the control of the neuromuscular system, commonly referred as coordination, timing or technique, to actually produce an increased in-water performance (Faigenbaum 2000). Unfortunately, results that try to support this idea remain inconclusive (Girold et al. 2007; Aspenes et al. 2009). Nevertheless, it was found positive associations between in-water and dry-land tests (Morow;:o et al. 2011a), as well as strong relationship between mean absolute force and the time at 50 m for the four swimming techniques (Morow;o et al. 2011b). The aim of this study was to determine which parameters are predominant to achieve better performances in age group swimmers. it was hypothesised that faster swimmers are taller and achieve higher values of mean (Fmean) and maximal force (Fmax). Moreover, it was hypothesised that faster swimmers present a more continuous arm coordination movement pattern, reflected through higher index of coordination (ldC) values.
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