Recently, I wrote a blog on the muscle-to-bone ratio (MBR). As we noted in that blog the MBR is not a new concept in the animal science/meat industry, but it has drawn new interest from strength and performance coaches as a new way of looking at an athlete’s body composition. Studies in athletes that have examined MBR have used anthropometric (i.e., skinfolds, bone breaths, and lengths) measures to estimate MBR. However, as I pointed out in that blog there are a number of issues when using anthropometrics to determine the MBR. Unlike anthropometrics, dual X-ray absorptiometry (DXA) does not have the issues and is a more accurate way to determine the MBR. Recently, we published a paper (Juckett et al., International Journal of Sports Medicine 44:592-598, 2023) that determined the MBR using DXA in 91 female NCAA Division I rowers, and 173 age-, sex-, and body mass index (BMI)-matched controls.
Let’s look at the results of this research in DXA-determined MBR. Not too surprising female collegiate rowers were taller (68.6±2.3 vs. 64.6±2.5 in; p<0.001) and weighted (165.8±18.1 vs.138.1±17.1 lbs.; p<0.001) more than their matched controls. In addition, the rowers had more lean mass (114.6±8.7 vs.90.6±11.0 lbs.; p<0.001), fat mass (45.7±11.6 vs. 42.6±10.9 lbs.; p=0.037), and bone mass (6.2±0.6; 5.2±0.6 lbs.; p<0.001) than controls. In examining the MBR, the female rowers had a significantly (p<0.001) greater total (18.5±1.3 vs. 17.4±1.4) as well as arm (15.9±1.5 vs. 14.0±1.5) and trunk (29.6±2.7 vs. 27.9±2.9) MBR than controls (Figure 1). Interestingly there was no difference in leg (17.0±1.6 vs. 16.8±1.6) MBR between rowers and controls (Figure 1). This lack of difference may be due to the fact that legs are involved in locomotion in both rowers and in controls.
College rowing involves sweep-style rowing, which involves one oar per rower on a single side. Although one might suspect that body composition asymmetries may develop in rowers due to the requirements of the sport, we did not observe any differences in total or regional measures of body composition asymmetries based on which side the athlete rowed on. In other words, even though rowers may be port or starboard rowers these performance aspects of rowing didn’t lead to any asymmetries in their body composition.
Because the NCAA Division I collegiate season involves a Fall season and a Spring season, during which the NCAA National Championships take place we sought to examine changes in body composition during these two distinct compete seasons. In addition, during the winter offseason, female collegiate teams spend a lot of time training and preparing for the Spring season. We observed that lean muscle mass was significantly (p<0.001) greater during the winter offseason and Spring season compared to the Fall season. In addition, bone mass was significantly greater (p=0.015) in the Spring season compared to the Fall season. No other measures were shown to be different (Figure 2).
These results demonstrate how the body composition of NCAA Division I female rowers differs from controls. A follow-up examination of rower-specific body composition showed a significant increase in arm bone mass and lean mass from the Fall to Spring competitive seasons. These findings will help rowing personnel better understand body composition of female collegiate rowers for training, injury, and performance.
References
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.
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.