Recently, I wrote a blog on the muscle-to-bone ratio (MBR). The first blog was on what the MBR was and how it could applied to sports. In a follow-up blog I wrote about a scientific paper [Juckett et al., 2023] that came out of my laboratory that compared MBR measured by DXA in female collegiate rowers to a group of healthy aged-matched females. This blog also looked at seasonal changes in the MBR in this group of collegiate female rowers. In these next blogs, I am going to examine another recent paper [Dengel et al., 2023] from my laboratory that we published on MBR determined using DXA in National League Football (NFL) players. Like the paper on collegiate female rowers, this paper compares total as well as regional measures of MBR to a healthy aged-matched control group. In addition, this paper examines total as well as regional measures of MBR in NFL players by position. Since there is so much information in this paper I have decided to split up the information into two blogs.

In this blog, I am going to discuss total as well as regional measures of MBR in NFL players (n=346) compared to a healthy aged-matched control group (n=228). Since we used DXA to determine measures of MBR we are also able to compare fat, lean and bone masses of NFL players to the age-matched, healthy, male control group. Let’s first deal with measures of fat, lean, and bone masses in these two groups. As expected, the NFL players had more total, fat, lean, and bone masses than their age-matched counterparts (Figure 1). In addition, NFL players had significantly greater bone mineral density (1.61+0.11 vs. 1.26+0.21 g/cm2, p<0.0001) than controls. The greater amount of bone mass and higher bone mineral density in NFL players compared to aged-match controls is not too surprising. It has been reported that athletes in high-impact sports (e.g., gymnastics, judo, karate, volleyball, and other jumping sports) or impact-loading sports (e.g., soccer, basketball, racquet games, step-aerobic and speed skating) have higher bone mass compared to athletes from low impact sports (e.g., swimming, water polo, cycling) [Tenforde & Fredericson, 2011]. In addition, high-impact sports have been reported to improve bone mass [Burt et al., 2013; Hagman et al., 2018; Lozano-Berges et al., 2018]. Therefore, given the impact and training that football players are exposed to, a greater bone mineral density would be expected.

Now, let’s look at the MBR data from this study. Although the NFL players have significantly greater amounts of both bone and lean masses than controls, they had a lower total MBR (Figure 2). This is probably due to the fact that the NFL players were taller than controls resulting in a larger total skeleton and ultimately a greater amount of bone mass for a proportional amount of lean mass resulting in a lower total MBR. Similar to total MBR, trunk MBR was significantly lower in the NFL players compared to controls. This is not surprising given the amount of core exercises that NFL players do compared to the normal population. Arm MBR was significantly greater in the NFL players while there was no difference in leg MBR between NFL players and controls. Although one would expect arm and leg MBR to be similar, these differences may be due to the fact that the legs support a larger total mass in the NFL group, and NFL players do large volumes of training that load the lower body (e.g., squat lift, deadlift, etc.). This loading of both bone and muscle results in proportional changes in muscle as well as bone. Although the arms also undergo targeted strength training (e.g. arm curls, bench press) they are not involved in supporting the body mass as in the legs. This results in less loading of the bone and ultimately leads to development of more lean mass than bone mass in the NFL player’s arms.

What does it all mean?

First of all, DXA allows coaches and athletic trainers the opportunity to determine MBR that does not require specialized anthropometric devices. Unlike anthropometric methods that utilize skinfolds, circumferences, length, and breaths to estimate muscle, fat, and bone masses, DXA provides a valid, accurate, and high-resolution measure of a three-component model of body composition. In addition, the DXA can provide both total as well as regional measures of MBR and is much faster than anthropometric methods to calculate MBR. Finally, we observed that total MBR was lower in NFL players than aged-matched healthy controls. This lower total MBR suggests that NFL players have a higher amount of bone for a given amount of lean mass. Our next blog will examine positional differences in total as well as regional MBR in NFL football players.

Burt LA, Greene DA, Ducher G, Naughton GA. Skeletal adaptations associated with pre-pubertal gymnastics participation as determined by DXA and pQCT: a systematic review and meta-analysis. Journal of Science and Medicine in Sport 16:231–239, 2013

Dengel DR, Evanoff NG. Positional Differences in Muscle-to-bone ratio in National Football League Players. International Journal of Sports Medicine 44:720-727, 2023.

Hagman M, Helge EW, Hornstrup T, Fristrup B, Nielsen JJ, Jørgensen NR, Andersen JL, Helge JW, Krustrup P. Bone mineral density in lifelong trained male football players compared with young and elderly untrained men. Journal of Sport Health Science 7:159–168, 2018.
Juckett WT, Stanforth PR, Czeck MA, Evanoff NG, Dengel DR. Total and regional body composition of NCAA collegiate female rowing athletes. International Journal of Sports Medicine 44:592-598, 2023.

Lozano-Berges G, Matute-Llorente Á, González-Agüero A, Gómez-Bruton A, Gómez-Cabello A, Vicente-Rodríguez G, Casajús JA. Soccer helps build strong bones during growth: a systematic review and meta-analysis. European Journal of Pediatrics 177: 295–310, 2018.
Tenforde AS, Fredericson M. Influence of sports participation on bone health in the young athlete: a review of the literature. PM&R 3:861–867, 2011.

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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