Jalilvand, F, Banoocy, NK, Rumpf, MC, and Lockie, RG. Relationship between body mass, peak power, and power-to-body mass ratio on sprint velocity and momentum in high-school football players. J Strength Cond Res XX(X): 000-000, 2018-The ability to rapidly shift one's body mass horizontally or vertically is common within American football irrespective of field position, and the capacity to generate power is a favorable physical quality. This requires analysis in high-school football players, especially considering the body mass disparities that exist in this population. Sixteen high-school players (7 backs and 9 linemen) completed the vertical jump (VJ) to determine jump height, peak anaerobic power measured in watts (PAPw), and power-to-body mass ratio (P:BM), and a 36.58-m sprint (0-4.57, 0-9.14, and 0-36.58-m intervals) to determine sprint velocity and momentum. Independent-samples t-tests (p < 0.05) determined differences in these variables between the backs and linemen. Pearson's correlations (r; p < 0.05) computed relationships between body mass, VJ height, PAPw, P:BM, with 36.58-m sprint velocity and momentum on the pooled data. Linemen were heavier, and slower in the 36.58-m sprint, but had greater PAPw and sprint momentum compared with backs. Body mass exhibited negative relationships to velocity across all sprint intervals (r = -0.55 to 0.70), and positive relationships with momentum across all intervals (r = 0.95-0.96). The VJ correlated with sprint velocity across all intervals (r = 0.51-0.83), but not momentum. PAPw was positively correlated with body mass and momentum across all intervals (r = 0.77-0.85), but not velocity. There were significant correlations between P:BM with velocity (r = 0.51-0.85) and momentum (r = -0.53-0.62) across all intervals. Heavier high-school players could focus on improving P:BM to positively influence jumping ability and sprint velocity.

The aim of the study was to determine the between-match and between-halves match variability of various Global Positioning System (GPS) variables and metabolic power average (MPA) in competitions, based on the match results obtained by professional soccer players over a full season. Observations on individual match performance measures were undertaken on thirteen outfield players competing in the Iranian Premier League. The measures selected for analysis included total duration, accelerations in zones (AccZ1, 2, and 3), decelerations in zones (DecZ1, 2, and 3), and MPA collected by the Wearable Inertial Measurement Unit (WIMU). The GPS manufacturer set the thresholds for the variables analyzed as follows: AccZ1 (<2 m.s−2); AccZ2 (2 to 4 m.s−2); AccZ3 (>4 m.s−2); DecZ1 (<−2 m.s−2); DecZ2 (−2 to −4 m.s−2); DecZ3 (>−4 m.s−2). The results revealed significant differences between wins and draws for the duration of the match and draws compared to wins for the first- half duration (p ≤ 0.05; ES = 0.36 [−0.43,1.12]), (p ≤ 0.05; ES = −7.0 [−8.78, −4.78], respectively. There were significant differences on AccZ1 during the first-half between draws and defeats (p ≤ 0.05; ES = −0.43 [−1.32,0.46]), for AccZ3 in the second-half between draws and defeats (p ≤ 0.05; ES = 1.37 [0.48,2.25]). In addition, there were significant differences between wins and draws (p ≤ 0.05; ES = 0.22 [−0.62,1.10]), and wins and defeats for MPA in the first- half (p ≤ 0.05; ES = 0.34 [−0.65,1.22]). MPA showed further differences between draws and defeats in the second- half (p ≤ 0.05; ES = 0.57 [−0.22,1.35]). Descriptive analysis revealed differences between the first and second half for wins in AccZ2 (p = 0.005), DecZ2 (p = 0.029), and MPA (p = 0.048). In addition, draws showed significant differences between the first and second half in duration, AccZ1, AccZ2, and DecZ2 (p = 0.008), (p = 0.017), (p = 0.040), and (p = 0.037) respectively. Defeats showed differences between the first and second half in AccZ1, AccZ3, and MPA (p = 0.001), (p = 0.018), and (p = 0.003) respectively. In summary, the study reveals large variations between the match duration, accelerometer variables, and MPA both within and between matches. Regardless of the match outcome, the first half seems to produce greater outputs. The results should be considered when performing a half-time re-warm-up, as this may be an additional factor influencing the drop in the intensity markers in the second half in conjunction with factors such as fatigue, pacing strategies, and other contextual variables that may influence the results.