Understanding Intensity & Output

Monitoring your training intensity and workload is an art form and we have lots of toys which can help us to achieve it successfully. A lot of runners have GPS devices and heart rate monitors, the cyclists amongst you may have a ‘power meter’ to measure your output in ‘watts’. So, what’s the best toy to use and how should it be used to gain the most benefit?

Intensity and Output

Understanding the difference between intensity and output is the most important thing before we go any further, so let’s just clarify how exercise intensity differs to exercise output.

  1. Intensity is simply how hard your body is working. You can measure intensity by checking your heart rate, your breathing rate and perhaps the most reliable gauge, perceived effort (PE). Perceived effort is a posh term for ‘how hard does it feel’. You can only measure how hard your body is working from physiological markers, whether that be your breathing and heart rate going through the roof, or your brain telling you that you can’t go any harder!
  1. Output is the performance achieved as a result of your exercise intensity. For example, whilst running you may feel as though you’re working really hard and your heart rate may be close to maximum (therefore your intensity is high). A quick glance at your fancy watch tells you your running speed is 7 minutes per mile (that’s your output). Alternatively, you might head out for a steady cycle ride and your heart rate and breathing rate might be considered to be ‘moderate’ (your intensity is moderate) and your cycle power meter shows 190 watts (that’s you output).

Aren’t they the same?

No, absolutely not. Let’s be really clear that OUTPUT measurements are not measurements of how hard you are working. Certainly from experience, you may know that when you run 7 minute miles, you tend to be working very hard. You may also know from experience that if you cycle at 190 watts, it generally equates to a steady and comfortable intensity. But they are not the same. The biggest reason why they are not the same, is that OUTPUT is impacted by lots of external variables, which therefore make it unreliable.

Example 1:

You go to the running track to run 6 X 800m, but due to a hard week of training, you don’t feel great. Nevertheless, you crack on and push your heart rate up to the planned level for that session. You feel as though you’re working as hard as you should be and your heart rate is also where it should be, but because your legs are tired, your split times / times per 800m are slower than normal.

Question: If your heart rate is at the correct level and you feel as though you’re working hard, but your pace per 800m is slower than normal, are you running at the right intensity?

Answer: Yes, you are training at you target intensity

Example 2:

You travel abroad for a cycling holiday and find yourself cycling at high altitude. Whilst completing a training ride your heart rate reaches the correct level and it certainly feels like you’re working as hard as you normally do. However, due to the altitude, your power output (watts) is lower than normal.

Question: If your heart rate is at the correct level and it feels like you’re working at the correct level, but your power output is lower, are you cycling at the correct intensity?

Answer: Yes, you are training at you target intensity

To be fair, scenario 1 is more likely, as not many of us jet-set to altitude on a weekly basis, but I’m sure you get my point. Sometimes, your intensity can be high (heart rate, breathing and perceived effort), but power and speed are lower. Irrelevant of whether power and speed are lower, the simple truth is, if it feels hard, then it is hard. Alternatively, if it feel easy, then it generally is easy.

Your point is?

If you use ‘output’ to gauge your training, then that means your intensity in some circumstances may be wrong. If you run on the track and use lap splits, or you use a gps and watch your minutes per mile, you’re choosing output and not intensity to gauge training. If you’re a cyclist and you use either speed or power to dictate training, you too are choosing output and not intensity to gauge your training. Some people choose to do this, which is fine, so long as you understand fully the difference between the 2 and the potential pitfalls.

Training is about intensity

Training is designed to place a stress or load on your body. As a result, you get an adaptation response and your fitness improves. To measure the training ‘stress or load’ you need to know how hard your body is working, or the ‘intensity’ of the workout. Therefore heart rate, breathing rate and perceived effort (how hard does it feel) should be used frequently to measure your intensity. If it feels like you’re training hard… then you’re training hard, irrelevant of what your speed or power output display shows.

Performance is about outcome

Here’s the catch. If you want to improve your performance, the simple truth is that you need to run at a faster pace or produce a greater cycle power output. Heart rate is irrelevant, nobody wins a race by saying “yes, I did finish 20 minutes behind the first finisher, but my heart rate was higher than theirs, so I win”. Using outcome measurements such as speed or power give you clear benchmarks for improvement in key sessions. Ultimately, if you want to cycle or run a certain time, you have to produce the right amount of power or travel at a specific speed.

You can’t perform all the time

So this paragraph is the crux of this blog post. It’s important to understand that OUTPUT measurements, are a gauge of your PERFORMANCE. So if you choose to use output such as a power meter, to gauge your training, you are testing your performance, every single session.

There’s 3 things to consider here:

  1. You can’t be at your best every single session. It’s simply impossible. In fact, why would you even want to be at your best every session? As the saying goes, the only important performance is on ‘test day’ or ‘race day’. Your performances in training will fluctuate from week to week. Linear improvement every week does not happen.
  2. If you train to output, you may train at the wrong intensity. For example, what happens if the session says ‘run at 7 minute mile pace’ or ‘cycle at 250 watts’ and you’re having a bad day and feeling a little tired? The answer is you’ll push way too hard to achieve the pace/power and train at the wrong intensity, causing even greater fatigue.
  3. From a psychological perspective, it can be a total ‘mind f**k’. Constantly fighting to hit the correct pace or power and feeling as though you’ve failed when you don’t. The pressure of having to ‘perform’ every single session, for both yourself and (if you’re on Strava) for others watching. It can be the absolute killer of joy. If your plan says ‘run easy’ then simply go and run easy, switch off your GPS so you don’t even know how fast you’re running. Why would you add that pressure to a potentially enjoyable run?

So finally, that means what?

Output should be used for key sessions to measure progress, but you should be ‘fresh’ and able to give 100%. There’s no point going to the running track and aiming to complete 800m repetitions in a key time, if you’re tired from a hard week of training. Your output (speed) will be slow and you’ll be disappointed when you don’t hit those key times. For the rest of your training, use intensity. If you’re riding easy, then ride at a pace which feels ‘easy’. If you’re doing maximal intervals, then do them at the intensity which feels ‘maximal’. The output will be what it will be.

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Marc Laithwaite is a level 3 qualified coach, who has been coaching endurance sports for the last 22 years. He is a former sports science lecturer of 12 years and spent 2 years with the British Cycling team as a bloods analyst. He has worked with British Triathlon Coach Education as a coach educator and spent 5 years as head coach of the NW Regional Triathlon Talent Squad. He’s also a former national age group triathlon champion, European duathlon champion and Ironman age group winner.

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