These are sprinting intervals of 100m (a quarter lap of a standard running track i.e one straight section) to 400m. The purpose of short intervals is to increase your speed, power, and ability to sustain both of these. They're good for increasing sprinting speed, but also work for for marathon runners because they will help you sustain your current marathon pace more easily.
Recovery periods between short intervals should be relatively long – roughly three times the length of the intervals – so you can maintain a consistent level of performance. If you don’t have enough time to recover, you'll slow down from one interval to the next and the workout will become a test of your fatigue resistance rather than a speed and power builder. The recovery period can be active (jogging) or passive (standing or walking).
Intervals of 600-1,200m are middle-distance, they can be used to improve aerobic capacity, lactate threshold and fatigue resistance, which all help you to run at faster speeds for longer periods of time. It's not realistic to be able to run flat out for this distance so try going at around 70% of your maximum speed. It's not an exact science but a general rule to follow is if you feel yourself starting to slow apply a little more pace so that you're just out of your comfort zone. The idea is still to run each interval as fast as you can, but it's important to finish the intervals rather than to run yourself to total exhaustion. Wait until you have fully caught your breath before starting your next interval.
Long intervals range from 1,600-3,000m in distance. It's not possible to maintain flat-out speed for this time and 70% effort will also be hard, instead just ensure you're constantly pushing and not settling into a jogging pace.
Because of their length, it only takes a few long interval sessions until you'll start feeling the benefits. They're particularly good for building overall stamina and increasing your lactic threshold (the time it takes until your muscles start to really ache). Rest periods between intervals should be as long as it takes for you to fully catch your breath and for your legs (or any other muscles) to stop feeling achey.
Great for: Burning fat
Pyramid training involves gradually increasing the duration at which you run at a high intensity before peaking and then working back down.
Great for: Improving match fitness
This interval session is perfect for improving your ability to run in short, sharp bursts over and over again, which is required by many team sports including football and rugby.
Great for: Spicing up your regular run
Fartlek is Swedish for speed play. Unlike other forms of interval training, which have pre-determined time limits, in Fartlek sessions you run at varying intensities for different lengths of time. This keeps your body guessing at what's coming next, forcing your heart, lungs and muscles to work harder and leading to improved fitness.
5min warm-up … and then go with the flow. If you spot a lamppost, tree or another runner in the distance, run hard until you get to them before reducing your speed to recover. Then aim for another landmark and run fast to it. The beauty of Fartlek training is that you can make it as hard or easy as you want, and it makes the extremely familiar sights of your normal run a little more rewarding.