This is the second blog post on fat and lean muscle mass ratios in college and professional football players.  The first blog post examined body composition ratios in defensive football players, and in this blog post, we will look at the offensive football players. As in the other posts that I have written examining body composition in college and professional football players, the data used in this blog comes from two large research studies that we conducted in our laboratory.  The first study examined body composition in over 467 NCAA Division 1 collegiate football players (Bosch et al., 2019), while the second study examined body composition in 342 National Football League (NFL) players (Bosch et al., 2014; Dengel et al., 2014).  Both studies collected data using the same model of dual X-ray absorptiometer (DXA) and all raw scan data were analyzed at one central location using the same software. In this blog post we will look at offensive football players (i.e., offensive lineman, tight ends, running backs, quarterbacks and wide receivers) data.

Total Upper to Lean Legs Ratio (TULLR)
The Total Upper to Lean Legs Ratio (TULLR) is a ratio of upper body total mass to lean muscle mass in the legs.  If we look at the table below we see that in both college and professional offensive football players the offensive linemen have a higher TULLR than tight ends, running backs, quarterbacks and wide receivers. This is very similar to what we found in defensive players where the defensive linemen had the highest TULLR compared to the other defensive football positions (i.e., linebackers and defensive backs). This ratio tells us that in both college and professional offensive football players, the offensive linemen are carrying more lean and fat masses in the upper region of their body compared to the other offensive positions.  This makes sense as this position requires holding space or driving the opponent back.  What is interesting in both college and professional offensive players in regards to the TULLR is that the quarterbacks have the second highest TULLR in professional football players and the third highest in college offensive football players. In both college and professional offensive players, the running backs and wide receivers have the lowest TULLR.  These positions put a premium on quickness and lateral movement, so these athletes need to sacrifice mass to be quicker.

Lean Upper to Lean Legs Mass Ratio (LULLR)
The Lean Upper to Lean Legs Mass Ratio (LULLR) is the ratio of lean muscle mass in the upper body (trunk and arms) to lean muscle mass in the legs (Table below). In both professional and collegiate offensive football players, quarterbacks had the highest LULLR. Offensive linemen in both college and professional offensive football had the lowest LULLR. On the defensive side of the ball, we saw that defensive linemen also had the lowest LULLR.  Given that these two positions mirror each other, it is not too surprising that they have similar LULLR values. The low LULLR coupled with the high TULLR, which is exactly what we saw in defensive linemen, suggests that the offensive linemen have a higher percentage of fat mass in their trunk and arms compared to the muscle mass of their legs. This fits with what we have seen in the research, that as players get larger, the amount of lean mass in the trunk starts to plateau and the amount of fat mass increases. In both college and professional offensive players, running backs came in with the second lowest LULLR after the offensive linemen. Given the need to drive forward, sometimes with other players holding on, it is not too surprising that these players need more muscle mass in the lower region of their body. Wide receivers and tight ends fall between our quarterbacks and running backs.  

Using TULLR and LULLR to look at change over time.
As we discussed in our blog examining these ratios in defensive football players, these two ratios provide a good way to quickly get a sense of how a player’s distribution has changed. If TULLR goes up and LULLR goes down it suggests the player has increased fat mass in the trunk and arms (this would likely be a concern). If both TULLR and LULLR go up it is likely the increase is driven by an increase in trunk lean mass or a loss in leg lean mass (or both), which would also, potentially, be a concern. If TULLR goes down and LULLR goes down it suggests a gain of lean leg mass or a loss of fat (and lean mass) from the trunk. These ratios help tell a complete story about change over time without having to look at 3-5 variables at once.

Gynoid Lean Mass to Lean Leg Mass Ratio (GLR)
The Gynoid Lean Mass to Lean Leg Mass Ratio (GLR) is the ratio of lean muscle mass in the gynoid region (the region around the hips and gluteal muscles) to the lean muscle mass in the legs (Table below).  As with the LULLR in both college and professional offensive football players, the quarterbacks had a higher GLR compared to other offensive football positions.  In both college and professional offensive football players, the tight ends had the second highest GLR after the quarterbacks. In professional offensive football players, wide receivers had the lowest GLR, while in college offensive players, offensive linemen had the lowest GLR. It should be noted that the difference in GLR across positions in both collegiate (range: 0.45-0.47) and professional (range: 0.46-0.48) offensive football players was not very different. Given that the gluteal muscles are the power producers, this can be an important ratio, however, it is also very important in return to play scenarios because the gluteal muscles are often one of the last muscle groups to come back. Tracking this ratio during the recovery process can be informative as to how an athlete is progressing.

What does it all mean?
So what does it all mean? As we stated in the blog examining these ratios in college and professional defensive players, these ratios give coaches and trainers who use DXA to examine body composition in their players a better understanding of the distribution of these masses. This distribution can be important in how players move through space. If a player is slow out of his cuts and is top-heavy (high TULLR and high LULLR) that could be their limiting factor in improvement.  Secondly, when players add total mass and lean mass the use of ratios allows trainers a way to monitor the addition of this weight. Finally, the data presented here demonstrate why methods such as DXA that allow us to make regional measures of body composition allow us to understand the different physical characteristics needed for the different offensive positions.  I hope these two blogs on the LULLR, TULLR and GLR ratios provide you with some new ideas on how to examine body composition data with an eye on the demands of a particular sport and position.  These and other ratios can be used in other sports such as track and field, baseball, hockey, volleyball, etc., that have distinct positions and might require very specific demands on body composition. For those that want more detailed information found in this paper and other papers we have written on this topic, please look at the references cited below. 

References
Bosch TA, Burruss TP, Weir NL, Fielding KA, Engel BE, Weston TD, Dengel DR: Abdominal body composition difference in NFL football players. Journal of Strength and Conditioning Research 28(12):3313-3319, 2014.
Bosch TA, Carbuhn A, Stanforth PR, Oliver JM, Keller KA, Dengel DR: Body composition and bone mineral density of division 1 collegiate football players: a consortium of college athlete research study. Journal of Strength and Conditioning Research 33(5):1339-1346, 2019. 
Dengel DR, Bosch TA, Burruss TP, Fielding KA, Engel BE, Weir NL, Weston TD: Body composition of National Football League players. Journal of Strength and Conditioning Research 28(1):1-6, 2014.
 

About the Author
Donald Dengel, Ph.D., is a Professor in the School of Kinesiology at the University of Minnesota and is a co-founder of Dexalytics. He serves as the Director of the Laboratory of Integrative Human Physiology, which provides clinical vascular, metabolic, exercise and body composition testing for researchers across the University of Minnesota.