Training to run faster or run further requires the runner to extend the current pace that a runner can manage or the distance a runner can run by small increments at a time in order for the body to adapt to the greater stresses gradually without injury.
The main elements that a runner needs to improve to run faster or longer are STRENGTH SPEED and ENDURANCE. A bit like baking a good cake these 3 ingredients need to be put together in the correct amounts to achieve the best result.
Strength can be improved by undertaking HILL training and some weight training (such as lifting kettle bells and small dumbells). Using the body's own weight is also good such as doing push ups and squats. There is no need for a runner to embrace weight training using heavy weights as large oversized muscles are not required, just good all round strength.
It is recommened that runners undertake STRENGTH training once a week or once a fortnight, depending how many days are available for training.
Endurance for runners means the ability to run for long periods of time at a given pace. This is improved by undertaking one of the key training runs (TEMPO) once a week. This should be a run of at least 6 miles up to 10 miles long run at a "swift" pace throughout. This will be just below your current race speed. Tempo runs are best done with other runners as this will ensure you do not slow down when you are feeling a bit tired or not so good during the run. At a Tempo speed you are unlikely to want to or be able to talk to anyone running near you apart from the first mile that may be run a bit slower in order to warm up the body.
The second training run to improve endurance is the long slow distance (LSD) run. Typically from 11 miles to 20 miles. This should be undertaken once a week if possible. If training days are limited the Tempo run should be undertaken in preference to the long slow run. The speed of the long run should be at easy pace that talking to other runners is easy, the running feels easy, the time will be well over a hour to 3 to 4 hours.
A runners SPEED for an endurance runner means the base speed that you can run at for a distance of at least 5km or 3 miles. It is not the speed you can run at for short bursts such a 100m.
Endurance running speed can be improved by undertaking short intervals of speed that are slightly faster than your current race speed. Improvements are gained by undertaking interval or repetition training either on a running track, treadmill or flat clear footpath or road. Typical sessions would be a warm up 10 minutes of jogging and drills (such a high knees, butt kicks, leg swings etc) running 800m at speed, rest or jog slowly for 2 minutes and repeat 10 times, cool down by jogging slowly for 2 minutes. There are many combinations of distance to run and time for the recovery that can be undertaken to give a variety. 1mile repetitions would be the longest distance and 200m the shortest distance for this.
FARTLEK (Swedish for Speed Play) is a form of training that combines endurance and speed in one session. Runners choose a route to run (road, footpaths, trails etc) and at random intervals run at speed for various lengths of time running slower inbetween these speed bursts. It is easy to run like this between objects such a 2 lamp posts or between park benches. If a group is doing this different runners can choose when to run fast each to make it more random.