The National Football League Scouting Combine from 1999 to 2014: normative reference values and an examination of body mass normalization techniques.

Abstract

The primary purpose of this study was to identify the most appropriate method for normalizing physical performance measures to body mass in American football players. Data were obtained from the population of players (n = 4,603) that completed the vertical jump, broad jump, 40-yd sprint, 20-yd shuttle, 3-cone drill, and bench press at the National Football League Scouting Combine from 1999 to 2014. Correlation coefficients were used to assess relationships between body mass and physical performance measures. For the entire group and each playing position, absolute (i.e., non-normalized) performance measures were significantly (p ≤ 0.05) correlated with body mass, indicating that normalization is warranted. Ratio scaling, however, was not appropriate for normalizing most performance measures because it merely reversed (and increased in magnitude) the significant correlations between body mass and performance. Allometric scaling with derived allometric parameters was appropriate for normalizing all performance measures because correlations between body mass and performance were near to zero and no longer statistically significant. However, the derived allometric parameters differed by playing position. Thus, when normalizing physical performance measures to body mass, strength and conditioning professionals should use allometric scaling with test- and position-specific allometric parameters. Additionally, in the current study, percentile rankings were generated to provide test- and position-specific normative reference values for the absolute measures. Until body mass normalization techniques are adopted more broadly, strength and conditioning professionals can use these normative references values to compare current players with those who have already participated in the Scouting Combine.