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 33(7): 1871-1877, 2019-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.