title: The effects of anthropometry and leg muscle power on drive and transition phase of acceleration: a longitudinal study on young soccer players.
abstract: BACKGROUND
  The aim of this study was to examine the effect of anthropometry and leg muscle power on accelerative ability and its phases (drive and transition).
  
  
  METHODS
  Thirty-six soccer players (age 12.4±1.2 years, body mass 49.9±8.9 kg and height 154.2±10.3 cm) were tested twice, in the beginning and in the end of competitive season, for anthropometric characteristics, countermovement jump and 20-meter acceleration (split 0-10 meters and 10-20 meters, indices of drive and transition, respectively). The soccer players were grouped according to seasonal changes in 20-meter acceleration (Δacc) in responders (Δacc≤-0.10 s), control (-0.05≤Δacc≤0.08 s) and non-responders (Δacc≥0.10 s).
  
  
  RESULTS
  Compared with the non-responders at baseline, the responders were younger (-2.0 years [-2.8;-1.1]), shorter (-10.1 cm [-19.4;-0.7]), with higher body fat percentage (7.7% [2.7%;12.6%]) and fat mass (4.1 kg [0.7;7.4]), and lower performance in the countermovement jump (-8.9 cm [-13.9;-4.0]) and 20 m acceleration (0.63 s [0.39;0.87]); during the season they had smaller body mass gain (-2.8 kg [-5.4;-0.1]), decreased Body Mass Index (BMI, -1.0 kg/m2 [-1.9;0]) and greater improvement in the 20-meter acceleration (-0.33 s [-0.38;-0.28]). The effect size for these between-group differences was large (η2≥0.18). The Δacc and Δ10-20 were moderately correlated with body mass difference (r=0.48 and r=0.53, P<0.01, respectively) and ΔBMI (r=0.50 and r=0.51, P<0.01, respectively), whereas the Δ0-10 was correlated with ΔBMI (r=0.34, P<0.05) and ΔCMJ (r=-0.34, P<0.05).
  
  
  CONCLUSIONS
  The findings indicated that the changes in body mass had the largest effect on changes in accelerative ability and on both two phases (drive and transition). On the contrary, changes in leg muscle power had impact only on the drive phase of the acceleration.
authors.affiliation: Department of Physical and Cultural Education, Hellenic Army Academy, Athens, Greece - pademil@hotmail.com.
authors.forename: Pantelis T
authors.initials: PT
authors.lastname: Nikolaidis
authors.forename: Jorgen
authors.initials: J
authors.lastname: Ingebrigtsen
authors.forename: Ian
authors.initials: I
authors.lastname: Jeffreys
mesh_terms: D000054:Acceleration; D000886:Anthropometry; D054874:Athletic Performance / Q000502:physiology*; D002648:Child; D015444:Exercise; D005080:Exercise Test; D006801:Humans; D007866:Leg / Q000502:physiology; D008137:Longitudinal Studies; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D012420:Running / Q000502:physiology; D012916:Soccer / Q000502:physiology*