As you may have guessed from a previous blog on speed training for ultrarunners you’ll know I’m a big fan of speed training and tempo running is a great speed workout. But what is a tempo run?
A bit of research on the internet shows that a tempo run can be simply defined as a 20 minute run at threshold pace which is 25-30 seconds per mile slower than current 5k pace or a run at 90 % of your maximum heart rate. Of course if you feel 90% is too hard then 75-85 % of max heart rate is also tempo intensity as is a run of 20-25 minutes in duration at between 10k and 15k race pace.If you are very fit it’s your 15-21k pace. It can also be defined as 70-80% of your aerobic capacity or a run of 20-25 minutes at 20-25 seconds per mile slower than your 5k pace or 40-45 minutes at 15-20 seconds slower than your 10k pace. The fastest pace you can manage for an hour is another common way of describing tempo intensity.
Just in case you didn’t quite follow me there, it’s a 20-60 minute run of between 75-90% of your max heart rate or at a pace somewhere between your 10-21k race pace
So to that’s pretty straight forward then, not much confusion on that issue!
Why is there such a big discrepancy on what the experts recommend as a tempo run?
Problems with defining tempo running
Most scientists and coaches definition of a tempo run is a run at just below your anaerobic threshold pace but the definition of anaerobic threshold isn’t as clear cut as you may think. Some say its the point where your body can no longer clear the lactate being produced in your muscles as fast as your body is producing it and therefore it starts to build up, others says its the point where respiratory rate increases without a matching increase in oxygen intake, others use a figure of blood lactate of 4mmol
The problem is that whilst we’d like to be able to define exactly how fast, far and at what heart rate a tempo run should be done researchers are even questioning whether a definitive point or threshold even exists. Some argue that blood lactate accumulates continuously and no specific threshold can be determined.
Whether it exists or not (and I believe it may exist in some people and not in others) both science and runners agree that training just under this supposed threshold does improve running performance significantly, particularly for races 15k to 42km.
But with no consensus on exactly what anaerobic threshold is and if it exists and no agreement on the ideal tempo intensity or distance how can we determine the most effective tempo run for us and is it a worthwhile training session for an ultrarunner
Why ultrarunners should include Tempo running
For ultra runners tempo pace (however you define it) will be quicker than race pace. However there are still substantial benefits to be had from doing tempo sessions. As I have argued in the speed training for ultra runners blog, if you can improve your pace at shorter distances then you have the potential to improve your pace at longer distances
For example if your marathon pace improves from 5 min ks to 4.30 minute ks then running at 5.30 minute k pace will seem very comfortable.
Its no coincidence that the majority of the winners of ultra races are also very credible marathon runners, often sub 2.30.
If we agree that tempo running is beneficial for ultrarunners then the next step is working out what a tempo run actually is and how best to use them in your training.
Tempo running for an ultrarunner
The fact that there is no consensus on tempo runs implies that the correct pace, distance and speed will be specific to the individual and the race the individual is training for.
When looking at any training run we should always have an understanding of the purpose of a particular training session. How do we want the body to respond?
For an ultrarunner two of the most important training effects are an increase in sustainable aerobic running pace (in terms of both speed and duration) and an increase in strength endurance to handle the repetitive loading on the legs that occurs during an ultra.
For this to happen we obviously need to run at a speed close to our supposed threshold to stimulate the body to respond by pushing that threshold up but also run for long enough to cause enough damage to the legs to force the body to respond by increasing strength endurance.
Pure speed training is great for speed but the load on the legs will be less since you are covering far less ground.Long runs do put a reasonable amount of load through the legs if they are long enough but most of us cant run long more than once a week so tempo running is an ideal mid week training run that develops both speed and strength endurance in the legs.
Tempo runs have a good balance of speed and duration that can help us develop both speed and resistance to fatigue.
With this in mind I would argue that shorter tempo runs of 15-20 minutes have limited value for ultra runners (except as a means of progressing to longer runs) as the time is not sufficient to place a significant load on the legs.
I believe that starting with 2-3 efforts of 15 minutes and then as your mileage and fitness increase build the time up to 90 minutes. One of my favourite tempo runs is 2 x 45 minutes hard with a 10 min jog in between. Keep in mind the pace for the hard sections will be slower than half marathon pace and probably very close to your marathon pace.
Strictly speaking 90 minutes isn’t a tempo run but I believe what you lose in running at a slower pace you gain from the extra load on the legs involved in running relatively fast for 90 minutes.
How fast should a tempo run be?
The fastest pace you can maintain for the specified time. If you can’t maintain the same pace for the whole run then it’s too fast. If you use a heart rate monitor it will be somewhere between 80-90% but will vary depending on a number of factors including fitness, fatigue levels and the weather so don’t be a slave to a number on your watch. Go with how you feel.
Running out and back courses are a great way to determine if you are pacing your runs correctly. Eg if you run out for 10 minutes then turn and run back to the start in 10 minutes then your pacing was good. If you made it back with time to spare you started too slow if you made it back in more than 10 minutes you started too fast.
How often should you include a tempo run in your training?
This will depend on how long your tempo run is. Anything lasting an hour or less can be done weekly (depending on your other training of course). Longer runs like the one I mentioned above are very demanding and are best done once every 2-3 weeks.
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