Max Strength – This is the amount of force you can generate within the muscles. This is also called slow speed strength as it takes up to a second plus to exert maximum force. For sprinting the stronger you are the better. A key point to note is that it is the maximum strength produced at the muscle angles involved in sprinting. While the squat is often assumed to be the max strength exercise with best cross over there are contrasting views on this. For the average amateur rugby player a 1 leg squat probably has the biggest cross over in my experience. Obviously the amount you can bench press will have little effect on your sprinting speed so ensure your training plan and goals are aligned
Speed Strength – This is the % of your maximum strength you can exert within the short space of time (~ 0.2 sec) that the foot is on the floor . The % of force you can output can be increased, meaning you are generating more ground impact and thus will go faster. Power exercises and plyometrics work on this facet.
Technique – The optimal mechanics will make a massive difference to your speed. This looks at foot placement, leg recovery, body angles, nervous system activation and more while ensuring they are optimal for the different elements of sprinting (first few yards, pick up, max speed and speed endurance elements of a sprint), albeit most rugby sprints never get past the acceleration phase. See more on sprinting technique here>>
* Bio-mechanical efficiency – This could be put under all of the 3 above categories. Often your strength is greatly inhibited by the angles of the joints being slightly off. This refers to having locked ankle bones, compressed sacrum, rotated spine or lower leg bones and would even include breathing. While these are not serious injuries they can down regulate strength by 10-20%. These joint imbalances go hand in hand with faulty muscle activation techniques. This area is improved away from the weights room.
Fatigue – However “fast” you are when there is acid in the legs, bruised muscles from contact and a down regulated nervous system from exertion your maximal output will be diminished and you will be slower than when fresh out of the changing rooms. Improve your resistance to fatigue through fitness and endurance based sprint work and you will diminish this effect to some extent.
Bodyweight – Sprinting at its basic level is strength vs weight. Professional sprinters are ridiculously strong and surprisingly light for how they appear just by looking at them. Rugby players are naturally heavier. You can help yourself here by dropping excess body fat so you are not carrying dead weight around in the form of extra KG’s. To lose body fat it is pretty much all about your nutrition.