This is my take on popular (and perhaps not-so-popular) running terminology. If there's a term that you've come across and it's not in this running glossary, let me know in the comments below and I'll try to add it in.
Aerobic - literally 'with oxygen'. Running aerobically means that your muscles are getting enough oxygen to function normally and maintain your effort.
Aerobic threshold - the onset of lactate accumulation in your blood as a result of sustained effort. Provided that the effort is not increased too much, it's possible to keep at this level without going into the lactate threshold. This typically corresponds to marathon pace.
Anaerobic - literally 'without oxygen'. The point at which the body starts to produce lactic acid a lot faster than it can be removed, leading to fatigue and a decline in performance.
Base miles - easy pace running commonly done at the start of or before a training block with the aim of giving you a foundation on which to build your endurance and speed.
Bonking - also known as 'hitting the wall', this is the result of having depleted your glycogen stores and the body is unsuccessful in using your other main energy supply, fat. This will lead to the quick onset of fatigue and declining performance.
Cool down - the reduction of effort before the conclusion of a run, aiming to lower your heart rate and allow you to transition to post-exercise.
DOMS - stands for delayed onset muscle soreness, it is the intense fatigue that you feel in the days following a hard workout. Especially common when adapting to strength training.
'Drop' (heel-toe drop) - the measurement in height between the heel and toe of a running shoe. Most shoes tend to be between 8-10mm, however more minimal drops are available, including zero drop by niche brands such as Altra.
Dynamic stretching - performing stretches while moving at the same time. These are preferable as part of the warm up to the opposite, which is static stretching. Examples of dynamic stretches include lunges, squats, and calf raises.
Electrolytes - salts and minerals, such as sodium, potassium, chloride and bicarbonate, which are found in the blood. When we sweat, the loss of electrolytes can bring upon a sharp decline in performance. During hard efforts or hot weather where you sweat more, drinking water alone won't be enough to rehydrate, you also need to replenish electrolytes. You can do this in the form of tablets or even just dissolving some salt in your water.
Fartlek - taken from Swedish, literally meaning 'speedplay'. It involves changes of pace to include periods of faster running with periods more steady pace. A popular example of this is the Mona Fartlek, but fartleks can also be unstructured and run on feel.
Glycogen - the form that carbohydrates are stored in the body, either in the liver or the muscles. When we 'carb load' for marathons, it's the increase in the total amount of stored glycogen which we are trying to achieve.
Interval training - running faster paces for shorter durations, followed by recovery periods which may involve jogging, walking, or altogether rest.
Lactate threshold - the point at which, due to intense effort, lactate is accumulating in your blood and will eventually cause you to fatigue. Most athletes can sustain this for 40-60 minutes, which for amateurs is 10k but elites can go up to half marathon. Otherwise known as LT2.
Microcycle - how a training plan is divided up, normally into single weeks (e.g. a 12-week training plan could be 12 x 1 week microcycles). 8, 9, 10 and 14 and 21-day microcycles are also common, though most amateurs use a 1-week template.
Macrocycle - the overall training cycle for a long term period, up to a year.
Mesocycle - a block of microcycles, normally 4-6 depending on the length of the microcycle, which normally have a specific focus, e.g. hills, speed, race pace.
Negative split - running the second half of a race faster than the first half.
Overtraining - the result of overloading your body with too much training relative to your capacity, and not allowing for enough recovery. Can lead to a decline in performance and injury. See my post on overtraining for more detail.
Periodisation - structuring your training mesocycles to peak at the time of your goal race(s), rather than attempting to train the same way all year round.
Polarised training - doing more training at the easier and harder range of efforts rather than in the middle. Similar to 80/20 training which suggests doing 80% of training at an easy effort and 20% at harder ones.
Positive split - running the first half of a race faster than the second half.
RPE - rate of perceived exertion. Commonly done on a 1-10 scale where the easiest effort is scored 1 and the hardest 10. This can be used to gauge training levels and track progress over time.
Recovery run - an easy pace run designed to take place in the days following a race or hard workout in order to stimulate the recovery from it.
Running economy - the amount of energy used to sustain a certain pace. Improvement in running economy mean the ability to run at the same pace as a previous measurement, but using less energy, meaning theoretically that you should be able to hold that pace for longer.
Static stretching - stretches which involve holding a muscles in a lengthened position, typically for 10-20 seconds. Contrary to common thought, this is best done after a run and not before, where dynamic stretching is preferable.
Steady running - running at a pace where it feels like you are working moderately. Sometimes referred to as 'zone 3', this is normally slower than marathon pace but faster than your typical easy run pace.
Strides - accelerations of around 10-20 seconds where you run up to around 90% effort (around the pace you'd run for a 1 mile race), hold at the top end for a couple of seconds, and then ease back down. It's normal to do 3-4 as part of a warm up and then again near the end of your run.
Surges - also known as 'pickups', these are accelerations of no defined length but which aren't as quick as strides. You will probably run up to around marathon pace/effort when surging.
Taper - a period before a race where you lower the overall volume of running and strength training in order to be fresh for it. The longer the race (and the longer the training block you have put in for it), the longer your taper should be. Tapering too much can lead to lost training gains and feeling sluggish on race day.
Tempo run - a workout commonly around 4-8 miles in duration, run around a pace somewhere between your half marathon and marathon pace, though it may include some faster segments.
VO2 Max - the maximum amount of oxygen your body is able to use during exercise. Increasing this number is normally a sign of increased fitness. Training at fast paces and racing, particularly at 5k and below, can lead to increased VO2 Max.
Warm up - the initial transition from non-exercise to exercise, with the aim of preparing your body for an increased effort. See my article on how to warm up properly for more detail.