This is the second blog post on body composition in female collegiate soccer athletes.  As I stated in the first blog post, we recently published a paper in the International Journal of Sports Medicine (Roelofs et al., 2020) on body composition measures in over 175 NCAA Division I collegiate female soccer athletes by position and season. In the first blog post, we explored total and regional body composition by position (i.e., forwards, midfielders, defenders, and goalkeepers).  In this blog post, we will examine the changes in body composition that occur throughout a competitive season. The athletes examined for this study underwent the measurement of body composition using dual X-ray absorptiometry (DXA) at six different time points (i.e., summer off-season, pre-season, in-season, post-season, winter off-season, and spring season) during a single competitive season.

Descriptive data by position (Table 1).
In this blog post, significant differences between positions in both the tables and figures are indicated by letters. For example, if goalkeepers have the letter b next to their value and midfielders do not share that same letter next to their value then there is a significant difference between these two positions regarding this value. On the other hand, if goalkeepers and midfielders have the same letter b next to their value then there is no significance in this value between the two positions. For figures in this blog post, we will use the same color scheme.  Goalkeepers are represented by red data points and a red line, defenders are represented by black data points and a black line, forwards are represented by green data points and a green line, and midfielders are represented by blue data points and a blue line. Like the tables, we used letters in the figures.  If a season does not share the same letter then there is significant difference for all position groups.

With that out of the way let’s look at the data in Table 1. Defenders and goalkeepers were significantly taller than both forwards and midfielders. Goalkeepers were significantly heavier than defenders, forwards, and midfielders. It should be pointed out that the goalkeepers also had a higher percent fat than both defenders and forwards. Not too surprising goalkeepers are bigger (i.e., height and weight) than athletes playing the other positions. Goalkeepers also carried more body fat than athletes at the other positions. More detailed information regarding both total and regional body composition differences by position can be found in the first blog post of this two-part series. This blog post will focus on the changes in body composition that occur during a competitive season.

Seasonal changes in body composition by position (Table 2, Figures 1, 2 & 3)
Let’s look at the changes in body composition over a competitive season for these female collegiate soccer athletes. When the data are stratified by position, the seasonal changes in body composition measurements all trended in the same direction for all positions (Figures 1, 2 & 3). For example, total body mass for all positions was significantly lower in winter off-season compared to the spring season and the summer off-season (p < 0.01; Figure 1). Similarly, percent body fat was significantly higher in winter off-season compared to summer off-season and pre-season (p < 0.01; Figure. 2). Lean muscle mass was significantly lower in winter off-season compared to all other seasons and the summer off-season was significantly higher than pre-season (p < 0.01; Figure 3). Bone mineral density (BMD), visceral adipose tissue mass, and total fat mass did not change between any seasons for any of the positions (Table 2).

What does it all mean?
So what is the take-home message of this research article (Roelofs et al., 2020) and the corresponding blog posts? First of all, the data presented in this blog illustrates the importance of tracking body composition in athletes throughout an entire season. As demonstrated in this study, in the spring and summer off-season when strength training loads are typically higher, athletes had greater lean muscle mass and lower percent body fat. Athletes maintained this body composition through the in-season to post-season periods, and then decreased lean muscle mass and increased percent body fat during the winter-off season. If athletes were only measured at pre-season and post-season, which is often the case in a lot of programs you would have missed a number of changes in lean muscle mass and fat mass that occurred during the entire competitive season. For example, the loss in lean muscle mass that occurred during the winter off-season might be concerning to a number of coaches, who want athletes to maintain or add lean muscle mass. In addition, limited assessments of body composition in athletes would give coaches, trainers, and athletes an incomplete picture of an athlete’s overall health during a season. Adaptations to training to enhance performance or prevent injury could also be missed if limited assessments of body composition were performed.

Finally, the results of this study (Roelofs et al., 2020) expand the existing literature body examining female collegiate soccer athletes. Nonetheless, further research is warranted to better understand the relationship of these changes in body composition to performance, injury, recovery, and appropriate changes to training. For those who want more detailed information found in this paper, please contact the corresponding author Dr. Don Dengel (e-mail: denge001@umn.edu).

References
Roelofs E, Bockin A, Bosch T, Oliver J, Bach CW, Carbuhn A, Stanforth PR, Dengel DR: Body composition of National Collegiate Athletic Association (NCAA) division I female soccer athletes through competitive seasons. International Journal of Sports Medicine 41:766-770, 2020.

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.