Specificity

Specificity in your conditioning programme is training your body to cope with the movements and challenges associated with your sport.  This needs to be taken a level further in rugby and drills should reflect your on-field position.  The very start of a programme may be more general so you can get overall fitness and stability up to an acceptable level, but you must progress to more complex and more specific routines.  

To achieve the physical adaptations necessary to attain peak rugby fitness, the individual elements of your game need to be isolated and worked on.  This includes raw and dynamic strength, position-specific speed, combined anaerobic and aerobic endurance, and agility in the specific movements associated with playing in your position.

Running at the same speed for 6 miles, or spending lots of time on bicep curls will not give you the results you need.  There is a role for interval running, and for compound strength exercises such as deadlifts, but endurance and strength exercises should progress to being dynamic and reflective of the game.  Specificity is key. Focus your training and performance nutrition on rugby.