The legendary New Zealand coach, Arthur Lydiard, who was one of the modern pioneers of distance running, used to advocate long slow distance (LSD) to build strength and endurance, but speed work to train the heart to adapt to a harder workload and help you run more efficiently. To make you run more efficiently don't just think you have to pound out mile after mile at a steady pace.
At least once a week some kind of resistance or "speed training" must complement all those slow miles. Experienced runners, although dreading any kind of speed work or hill work at first, grow to enjoy it as they see the benefits.
Ideally speed work should be overseen by a running coach, personal trainer or friends who have experience of doing similar sessions. If this is not possible follow the basic rules of: 5-10 minute warm up, easy stretching before the main efforts, and the same afterwards. Decide on what your session is going to be beforehand and then stick to it.
1. Minute hard, minute easy
As the name suggests, after warming up, just start to run harder (but not flat out) for one minute, followed by an easy minute. Repeat about 4-6 times to start with and gradually increase the number by 1 or 2 each week up to a maximum of 10. If you don't have or don't choose to wear a watch, you can easily use natural objects like lampposts. Run hard a distance of 1 or 2 posts then a similar distance running easy before repeating.
2. Steady out, faster back
Plan an out and back route (as flat as possible works best), from home or work. Without holding back on the outward run, run steadily to your turn-around point. Check the time and try and return in at least an equal time, or if you are feeling good, slightly faster than your outward journey.
3. Tempo runs
These are designed to develop speed and endurance. As the name suggests, a continuous run at a pace that is not flat out, but is certainly faster than regular training pace. It will help you to hold a faster pace for longer. The speed and length is all relative to what you are training for, and how fit you are at any point in your training programme. If you are training for 5k or 10k then 15-20 minutes is fine. If you are training for half marathon or longer, then it can be for up to an hour or longer.
4. Up the clock
As the name suggests, a session based on set time spans, and an extension of one minute hard / one minute easy. After warming up, run one minute hard followed by one minute easy; then two minutes hard, two minutes easy; three minutes hard three minutes easy, before reducing down to 2 minutes hard, 2 minutes easy and finishing with 1 minute hard, 1 minute easy. There are many variations to try as you get used to this exercise such as; 1-1 2-2 3-3;3-3 2-2 1-1. Or as you gain experience and confidence repeating the whole sequence twice or even extending it to 1 -2- 4 -5 etc.
5. Fartlek sessions
A word from Sweden, fartlek literally means 'speed play' and is a more spontaneous version of the structured 'up the clock'sessions. Originally run on forest trails, they can easily be done on the roads too. Instead of running for 1 or 2 minutes hard then easy, you pick a landmark (like a tree, or a brow of a hill, or a junction) and run hard until you reach it, then run easy to the next local landmark (which you have decided on while jogging) before picking up the pace again to your next chosen landmark. Can be done alone, but also fun in a group where it is taken in turns to choose the next landmark. The shorter the distance, the faster you run!
Remember the golden rule: train, don't strain! While most coaches or trainers will recommend going slightly out of your comfort zone once a week, speed work should be a little taxing on the body, but it wasn't designed to propel you into oblivion or injury.
Don't kid yourself out of harder training, but be prepared for warning signs of dizziness or slight pains, and ease back or just jog the remainder of the session. Whatever distance you are training for, getting to the start line and not the physiotherapists's couch is the 'big picture'.