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What is intensity in relation to training? Why is it important?

Hello again RealFITT community! I hope that your week is going well and thank you for taking the time to read my answer to this week’s great question about intensity and how it relates to training.


All of us engage in several types of training here at RealFITT, most commonly strength training and conditioning style training. Strength training targets our musculoskeletal (muscles-soft tissue, bones, joints) systems and conditioning training targets our cardio respiratory systems (heart and lungs). These systems are fuelled by the phosphate, lactate, and aerobic energy systems. Intensity effects these systems and their ability to perform in different ways. Generally speaking the more intensity the harder it gets! 

So let’s discuss intensity in relation to strength training first. Intensity refers to either a percentage of a one repetition maximum (1RM) or a rate of perceived effort (RPE). 

For example, if you have a 1RM of 100kgs in the back squat then working at 90% of your 1RM would be considered high intensity and you are likely to only be able to perform 1-4 reps safely before your form and technique begins to breakdown. Alexander Sergevich Prilepin created a table, Prilepins chart in the 1970’s that is an effective guide to how many sets and  repetitions can be safely performed at certain percentages of our maximal efforts.

Low intensity training would be considered 60% and below, at these percentages you can comfortably perform many repetitions. 

RPE is another way to gauge intensity when strength training. For example an RPE of 10 would mean that you couldn’t possibly perform another repetition, whereas an RPE of 6 would mean that you could comfortably perform another 4 repetitions. 

In order to get stronger it’s important to carefully plan out your training so that at some stage in your cycle you train at high intensity, this will teach your nervous system and musculoskeletal systems to get used to handling heavier loads, and hence adapting to them. 

So why is intensity important in strength training? Depending on your goal intensity can be very important, for instance if you’re aim is to get stronger and increase maximal strength then you must spend time training at high intensities. There is a cost to this though, it is much harder to recover from, so you have to make sure that you do your active recovery. People who are used to training at a high intensity regularly will have what we call a high level of General Physical Preparedness (GPP) for it and will be adapt to recovery quite quickly from high intensity strength training. If you’re new to it then take care, do your cooldowns and mobility, and any stretching that your coach has prescribed for you.

Most of your strength training will be spent at low and moderate intensities because it’s the safest and most effective way to be able to train and perform week in, week out, year round. Don’t worry though, you can and will still build the body’s most precious metal....muscle, working at these intensities when done correctly. 

Ok, so onto intensity in relation to anaerobic and aerobic style training. Most commonly we refer to intensity as a percentage of your heart rate maximum (MHR) when it comes to these styles of training. To get your MHR it’s simply 220 minus your age, whilst not entirely accurate it can be used as a guide. High intensity conditioning would be considered working in the 70-85% of MHR zone throughout your session. Moderate intensity being considered 50-70% of MHR. If you’re aiming to work at a given heart rate training zone it’s a good idea to consider using the Heart Rate Reserve (HRR) formula to calculate this.

Accumulating short bouts of high intensity conditioning training regularly throughout the week is a great way to increase your lung capacity and your cardiac output whilst increasing your capacity for fat loss. 

For most it is unrealistic to expect to train at a high intensity for your whole session, every session of the week. It can take years to build the general physical preparedness to train at a high intensity daily. You can effectively utilise interval training for your conditioning as a means of accumulating intensity throughout a session without being forced to drop your heart rate due to fatigue. The benefits of doing this are great and include, improved lactate tolerance and endurance, increased lung capacity, increased cardiac output, lowered heart rate, and body fat reduction to name a few. 

Let’s say you’ve allocated 20mins of your day for some conditioning training whether it be aerobic or anaerobic in nature, a good goal would be to safely achieve as much high intensity as you can relative to your fitness goals and aptitude. An example might be using the airdyne or exercise bike, or even the rower- work at a 1:2 ratio. If we go off 1 minute as our interval time then this becomes 1 min high intensity, followed by 2 minutes moderate to low intensity. Alternatively you could do a 1:3 ratio, using 15 second intervals, meaning high for 15secs and moderate too low for 45 seconds. The challenge here is that, depending on your level of fitness 45 seconds may not be long enough to reduce your heart rate enough to recover for another high intensity burst, meaning that you will begin your next 15 second high intensity burst under fatigue and most likely in the presence of lactic acid which has a part to play in the process that gives us that muscle ‘burning’ sensation. Work to rest ratios are adapted to suite the individual’s goals and current fitness levels.

To give you an idea, Rugby Sevens players are some of the fittest athletes in sport and it is not uncommon to see them using the ergs for 7:7 intervals, for up to 15 minutes at a time, as in 7 seconds all out effort, followed by 7 seconds recovery. You can imagine the ‘burn’ here and the conditioning required to even attempt this style of interval training.

In summary, intensity is an important training variable, that needs to programmed carefully. If you want longevity in your training, you can’t train at a high intensity every single session. Imagine if you owned a car that was capable of going 200km/hr, if you drove it around at 200km/hr everywhere you went, the engine would break down quickly. Training at a high intensity is important, but be careful not to overdo it.

If intensity interests you and you’d like to continue this discussion then, please as always chat with your coach or shoot me an email and we can get into the finite detail about intensity in training and it’s effect on the body. 

See you in the gym! 

Joe Matthews


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