# Acceleration Capacity and Vertical Jump Performance Relationship in Prepubertal Children
## 1 Introduction  
Physical testing is necessary to identify strengths or weaknesses to build an efficient training periodization. It is also used to monitor training efficiency and to assess fatigue and over-reaching [1, 2]. In this way, physical tests are commonly used during childhood in the context of training. Moreover, tests are used in a recreational context, for instance in school physical education programs, to provide information about general fitness levels [3]. Thus, it is still an actual concern to establish normative values for children [4] and to propose test batteries appropriated to this population [5]. These tests should be easy to administer under time constraints. For this reason, most test batteries apply jump and sprint assessments. These two abilities are considered fundamental and determinant in several activities [6, 7]. Moreover, jump and sprint performances are used in many federations and institutions for talent identification. The development of jumping and sprinting performance during growth is well documented. A rapid increase is generally observed from 5 to 14 years of age [8], with a slower increase between 9 and 12 years of age [9] due to the stabilization of central nervous system development [10]. The second rapid increase after 12 years of age is generally attributed to gains in strength and power associated with hypertrophy, observable by an increase in the cross-sectional area [11]. This hypertrophy can be associated with changes in the muscle architecture including lengthening of the fascicle and modifications of the pennation angle. Moreover, an increase in the proportion of fast-twitch fibers is observed during adolescence [11]. It has also been shown that prepubertal children have a reduced efficiency during exercises involving the stretch-shortening cycle [12, 13]. Other authors have explained this low efficiency by neural aspects such as inefficient muscle preactivation [14] or a lower stretch reflex control [15]. These deficits in neural capacities induce a suboptimal regulation of the muscle-tendon stiffness during jumps [14]. Moreover, children have a more compliant muscle-tendon system than adults, which may reduce their ability to recoilelastic energy [16; 17]. It could be principally explained by the greater compliance of the tendons [16], which could imply a lower efficiency in force transmission. Muscle strength positively influences both sprinting and jumping performance, suggesting a strong relationship between jump and sprint abilities. Such association has already been demonstrated in adults [18; 19] and adolescents [20; 21; 22]. These correlations are generally attributed to the importance of lower body strength and power output for sprint and jump performances [23]. Some studies have suggested a similar relationship in children. Indeed, several training programs have induced an improvement in both sprint and jump performance [24; 25]. Recently, a study showed a correlation between 20 m sprint and horizontal jump performance [26]. Some others have identified a relationship between vertical jump and 30 m sprint performance with 7- to 10-year-old boys [27], and between CMJ and 15 m sprint performance in prepubertal boys [28]. However, to our knowledge, no study has investigated the relationship between jump and short-sprint performance. However, the ability to accelerate over a short distance is important in several activities [29; 30]. In adults, some studies dealing with strength capacity and running acceleration or maximal velocity have shown different correlations. [PERSON] et al. [31] demonstrated that acceleration was strongly correlated with peak force during a squat jump, corresponding to a concentric contraction. In contrast, the maximal velocity was more strongly correlated with the stretch-shortening cycle and maximal absolute strength. This distinction between acceleration and maximal velocity remains to be explored in children.