As part of our blog series on exploring body composition in college and professional football players, I want to look at some ratios that we utilize in analyzing body composition in football players as well as other athletes. Ratios are just a way to compare the distribution of total, muscle and fat masses in the upper body to the distribution of these masses in the lower body.  In a sport such as football, the distribution of total, muscle and fat masses is important and often differs between positions. Ultimately, a player has to move their body on the field, and the distribution of their mass will affect those movements. However, in some positions, you may need to hold an area and it may be beneficial to be bottom-heavy (i.e. defensive tackle).  One of the unique things about using dual X-ray absorptiometry (DXA) to measure body composition is that it not only gives you total muscle, fat and bone masses, but it also gives you regional measures of these three masses.  These regional measures of muscle, fat and bone masses allow us to look at the distribution patterns of these masses. 

To look at these ratios in college and professional football players I am going to use data from two research studies that we conducted in our laboratory.  Data for both studies was collected using the similar DXA devices at each location and all data were analyzed at one central location using the same software.  The first study examined body composition in over 467 NCAA Division 1 collegiate football players (Bosch et al., 2019). The second study examined body composition in 342 National Football League (NFL) players (Bosch et al., 2014; Dengel et al., 2014).  In this blog, we will look at defensive players (i.e., defensive lineman, linebackers and defensive backs) and in a subsequent blog; we will look at offensive players. (i.e., offensive lineman, tight ends, running backs, quarterbacks and wide receivers).


Total Upper to Lean Legs Ratio (TULLR)
The 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 defensive football players the defensive linemen have a higher TULLR than both linebackers and defensive backs.  Linebackers in both college and professional defensive football players had a higher TULLR than defensive backs.  This ratio tells us that in both college and professional defensive football players, the defensive linemen are carrying more lean and fat masses in the upper region of their body compared to the other two defensive positions.  This makes sense since this position requires holding space or driving the opponent back, while the linebacker and defensive back positions require more quickness and lateral movement, so these athletes need to sacrifice mass to be quicker.

Lean Upper to Lean Legs Mass Ratio (LULLR)
The 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 defensive football players, the defensive backs had the highest LULLR.  In college defensive football players, linebackers had a similar value to the defensive backs, while in professional defensive football players, the linebackers had LULLR that was lower than the defensive backs.  Defensive linemen in both college and professional defensive football had the lowest LULLR. The LULLR and TULLR suggest that the defensive linemen have a higher percentage of fat mass in their trunk and arms compared to the muscle mass of their legs (they had the highest TULLR but lowest LULLR). This corresponds with what we have learned from the research over the years, that as players get larger, the amount of lean mass in the trunk starts to plateau and the amount of fat mass increases. 

Using TULLR and LULLR to look at change over time.
Using these two ratios is 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 suggest the player has increased fat mass in the trunk and arms, which may actually 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 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 defensive football players, the defensive backs had a higher GLR compared to both linebackers and defensive linemen.  In professional defensive football players, the linebackers had a similar GLR to the defensive backs while in college the linebackers had a greater GLR than defensive backs.  In college defensive football players, the linebackers and defensive linemen had similar GLR while in professional defensive players, defensive linemen had a GLR that was greater than both linebackers and defensive backs. 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 when time is missed. Tracking this ratio during the recovery process can be informative as two how an athlete is progressing.

What does it all mean?
So what does it all mean? First, these ratios give trainers and coaches 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 demonstrates 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 these three different defensive positions.  In an upcoming blog, we will examine these ratios in collegiate and professional offensive football players. 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.

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