How to prevent running injuries and maximise performance by managing training intensity
Injuries are not a new thing for runners with some research showing that up to 80% of runners will have an injury at any given time. Runners, coaches and physiotherapists are always in the pursuit of injury prevention with load management and strength training being the Gold standard. Managing training intensities is something that isn't talked about as much but can have a huge impact on injury and performance.
Why running slower can be better for you:
Total volume, intensity and variability are all important to consider if you want to maximise your fitness gains. As we get fitter and stronger it is exciting to run fast and feel good doing it. There is temptation to keep pushing the pace until suddenly you are doing 4.30 min/KM on your long runs. While this may feel good short term and is certainly impressive this can cause more harm than good. Some of the benefits of running at a slower pace:
Lower risk of injury:
As our speed increases, so does the demand on all of the muscles and tendons in our legs and feet. They have to generate more force to increase stride length, increase the rate of force development to increase turn over AND have to absorb more load and ground reaction forces. This increase in load is good, great in fact, for increasing the tolerance of those tissues, but only when done gradually. Too much too soon will result in overload of the muscles and tendons which do take longer to adapt compared to our fitness levels. If not addressed, this overload then turns into injury, time off running and overall reducing you fitness gains.
Maximising total volume levels:
Many runners tend to focus on pace and weekly KMs as a measure of how much running they do, after all saying you do 100 kms a week at 4:30 min/KM pace sounds more impressive. But KMs run is less important compared to the total volume of duration of weekly training. The cardiovascular system (heart and lungs) adapts to exercise based on the amount of time loading it, so the more minutes and hours you do the better. Doing 100kms at 4:30 pace will only be 7.5 hours of training for the week, but if you slow down to 6 min ks it will be 10 hours a week. AND if you slow down you will probably be able to increase your weekly KMs because your legs aren’t so tired!
Maximising the aerobic energy system capacity:
Any event that lasts longer than 2 minutes is going to be predominantly fueled by the aerobic energy system. So it is super important for performance that we maximise aerobic capacity and the only way to do this is by training below our aerobic threshold (AeT, a metabolic marker relating to blood lactate). If we are running too fast the energy demands increase and we start to utilize more of our anaerobic energy systems. Long term training like this can result in Aerobic Deficiency Syndrome (ADS) and poorer performance.
So how fast should we be running?
Using heart rate (HR) to determine intensity is the best way to set our training sessions and maximise the benefits of training. Once you have determined your different HR zones that will dictate your desired HR for a particular session and then you run at a pace that matches that HR. Keep in mind that this pace will fluctuate day to day depending on how you're feeling. This allows for more flexibility in training and means we are actually listening to the body's needs (super important!). When setting out your running training you should be doing 80% of your running in zone 1 and 2 and up to 20% doing intensity training in zone 3 and 4. BUT if you have ADS then you should be doing 100% of your training below the AET ( i.e zone 1 and 2) until you have maximised your aerobic capacity.
What are the heart rate zones:
While there are a few different models for HR zones, most of them are very similar and just use slightly different terminology. However the recommendation of how to determine an individual person's HR zones is varied and there are many generic calculations, such as using percentages of estimated maximal HR, that are inaccurate. This simple 4-zone system does a good job of personalizing intensities to your unique metabolic response by anchoring this system to two important metabolic markers (AeT and AnT).
BUT FIRST, to understand this best you need to know a little bit about the exercise physiology and energy systems. Here are the basics broken down very simply:
We have 2 main energy systems that generate energy, they don't work in isolation but one will be working more than the other depending on intensity.
The aerobic system uses oxygen in a chemical reaction to create energy without by-products like lactic acid that slow us down, BUT it takes time to do this.
The anaerobic system doesn’t use oxygen and so it can generate energy faster allowing us to go faster, BUT it has by-products like lactic acid that slow us down.
If we are exercising at a low intensity and have sufficient time to use oxygen then we will use the aerobic system. As the intensity increases, the percentage of energy provided by the anaerobic system increases. Eventually it is nearly 100% anaerobic and we are producing too much lactic acid and have to slow down. Think of a bathtub filling up with water faster than it can drain and it eventually overflows.
Not only does the aerobic system not create by products, it also helps to “ mop up” the overflowing lactic acid and reuse it to create more energy (this is why the aerobic system is so important!)
Our AeT is the point of 2mmol of lactate in the blood and is when we start using more of the anaerobic system
Our AnT is the point of 4 mmol of lactic acid in the blood and is when we are creating more lactic acid than we can get rid of and can only sustain this level of intensity for a short time.
Aerobic Deficiency Syndrome ( ADS) is when the difference in HR of the AeT and AnT is >5-10%. (Eg an AeT=150bmp and a AnT =180bmp has a 17% difference)
So without further ado, here are the HR zones and how to best use them:
Perceived effort: very easy to easy
Purpose: Aerobic conditioning
Method: continuous 30 minutes to several hours
Perceived effort: moderate for those with a high AeT, easy for those with a low AeT
Purpose: Aerobic capacity, muscle economy
Method: continuous 30-90 minutes
HR: AeT to AnT
Perceived effort: medium, fun hard, not exhausting
As you can see the all important AeT and AnT numbers are key in determining your HR zones and also whether or not you have ADS. There are a few ways of testing for these numbers with varying levels of accuracy and accessibility.
Uses a protocol on the treadmill to increase speed progressively until exhaustion
HR and lactate measures taken at each stage
Data then plotted on a graph to assess lactate curve, AeT (2mmol blood lactate), AnT (4mmol blood lactate) and max HR
Although this type of testing is the most accurate they can be expensive and not easily accessed outside of major cities. The following two tests measure AeT and AnT respectively and have been shown to have a good correlation with the above lactate testing.
HR drift test: How to measure AeT:
Equipment needed: HR monitor ( not wrist based) and either; a treadmill or a flat track/running loop AND a GPS enabled watch
Step 1: Estimate what you think your AeT might be, then do a 15 minute warm up building up to the pace that correlates with that HR. This pace should feel easy and like you could breathe through your nose only.
Step 2: start the test: maintain the pace you have found that initially matches your estimated AeT, do not deviate from this pace, go for 1 hour, press the lap marker on your watch at 30 minutes.
Step 3: as this is a submaximal test you shouldn’t need to warm down
Step 4: analysis: Compare the HR average in the first half of the test to the second half. When you hold an aerobic pace at the AeT, your HR will remain nearly constant for as long as an hour. If yourHR rises more than 5 percent at that steady pace, your starting HR is higher than AeT. If the HR drift is less than 5 percent, your starting HR was below AeT. Repeat the test if necessary to get a correct measure.
Lactate Threshold test: How to measure AnT:
Equipment needed: HR monitor ( not wrist based) and a GPS watch
Step 1: warm up at an easy pace for at least 20-30 minutes and include a few faster 1-2 minute efforts so that you are fully warmed up
Step 2: chose either a 30 minute or 60 minute test. 30 minutes is suited for those who are starting out and 60 minutes is suited for higher aerobically trained athletes with good muscular endurance.
Step 3: Start the test: run for the duration of the test ( 30 or 60 minutes) at a consistent moderate to hard effort pace. You want to be going as fast as you can. That is sustainable for the whole test without blowing up and having to slow down.
Step 4: easy active warm down jog or walk for at least 20-30 minutes
Step 5: analysis: first compare your pace in the first half to the second half to assess the validity of the test and your effort. If you were much faster in the second half it means you probably didn't run fast enough in the first half and conversely if you had to slow down a lot then you probably started out too hard or needed to do a shorter test.
Step 6: if the pace was fairly even then we can say that you were running at your maximum sustainable pace and the average HR for the test equates with the metabolic point where you are accumulating lactate at a high rate but you are still able to clear it aka the AnT and top end of zone 3.
So now what?
Once you have determined all of the above information you can set up your training zones and map out training sessions to include a variety of sessions at varied appropriate intensities (Keep the 80%/20% rule in mind).
This will allow you to train effectively like the best athlete is the world and get good performance gains. Using this method will ALSO reduce your risk of injury because you allow for flexibility in pace, variety in the loads being placed on the muscles and tendons and reduce the risk overload.
At the end of the day, less injuries equals less days off running and more consistency which ALSO leads to better performance! SO good luck and HAPPY TRAINING!