Body size

Body size refers to the stature and mass of the player. Someone with a very limited understanding of rugby may describe the body size of a rugby player as big, muscular, and tall. In a collision sport such as rugby, bigger is often seen as better. Increased body mass has several potential advantages:

1. harder to move – players with a greater mass are harder to knock off balance, which can be beneficial in contact situations
2. greater momentum – in physics, momentum is mass multiplied by velocity and it is a key consideration. For example, if a player is hitting the defensive line with a greater momentum, then they will be much harder to stop and thus more likely to make a line break. Momentum can be increased by increasing body mass or velocity or both
3. protection from injury – increased body mass surrounding key joints and body structures can provide more cushioning from the impact of contact
4. greater force production - if a high proportion of the large body mass is muscle mass, then the player has the capacity to produce large levels of force which will be extremely beneficial.

Figure 3. Body mass change over a 13-year period in male under-20 players (Lombard et al 2015).

According to research, body mass is a very important physical characteristic to performance. A study by Lombard and colleagues in 2015 examined the physical characteristics of the South African U20’s national team over a 13-year period from 1998 to 2010. This period coincided with the beginning of professionalism and finished in the relatively modern era. They found that when forwards and backs were combined, the average body mass rose from 87kg in 1998 to 99kg in 2010. This indicates that an increased body mass was important to performance in the game of rugby as it evolved over this period. Body mass has also been shown to be able to differentiate between levels of play in rugby and to correlate with success in rugby competitions. Jones and colleagues in 2019 looked at comparing body size and lower body power measures of professional and amateur rugby players. Where body mass was concerned, they found that the professional rugby players were on average 9.9% heavier than their amateur counterparts.

While body mass is a physical characteristic that can impact the game, caution should be advised against thinking that bigger is always better. With increased body mass, the body is more difficult to move about the pitch which could impact fatigue levels. Players should strive for a body mass which allows them to complete the technical and tactical demands of their position whilst being able to compete physically with their opponents. Body mass composition is also important, and this is examined next.