TRAINING LOAD – What is it and why it’s important!

Training Load – A brief Summary.

We live in a world where information is freely available everywhere we go. For anyone who exercises, amateur or professional, this means a constant knowing of your physiological metrics for training and recovery. Take your smart watch for example- it gives you an indication of your sleep quality, recovery status, training suggestions, performance metrics, and so much more. But amongst all of this, how accurate is it, and what lens should we use to understand our internal physiological status. We will briefly deconstruct the most essential aspects of “training load”, with the goal of providing a pragmatic way of using it.

What is training load?

There are two important terms to think of when understanding training load- namely internal and external load. External load refers to the work done to produce a quantifiable output. Power, pace, speed, distance, and time are some of the common forms of external load that can be measured, however there are numerous others. Internal load refers to a physiological response (within the body) to such work done. Measurables such as heart rate, perceived exertion, lactate measures, and a few others are the types of measurements reflecting internal load. When we talk about training load, we are referring to both variables, with the product of them representing your total load.

How are these measures calculated?

The calculation of training load is not as simple as that though. For example, your fatigue and TSS score on Training Peaks calculates your training load very differently to the Garmin stress score algorithm. What they all have in common though is that they use both internal and external loads. In its purest form, your training load is an expression of the work you are doing AND the response to that work.

When calculating external load, we always try to remove variables that impact the actual work done, for example using normalized pace instead of average pace (remember normalized pace removes any gradient affects). Or another example, using actual cycle time rather than total time when riding (because with an outdoor ride, just rolling down a hill with no pedaling is not work done).

Obtaining internal load is more challenging. The best form of internal load (response to work done) is measuring lactate within the blood. This is, however, not possible for almost anyone during training. So, we use either heart rate, or rate of perceived exertion (RPE). Which one is better? There is no end to that debate, but we would say that you should use both. Your heart rate is a singular quantitative metric, meaning it is a numerical value directly measured from your cardiovascular system when you are doing work. RPE is a qualitative metric, meaning it is reported by an athlete, and is a more wholistic picture of what you are experiencing when doing work. Things that can influence the internal response to exercise are hydration status, stress, hormone levels, emotional status, sleep status, and many others. Considering this, a heart rate response today at say 8/10 RPE effort may look very different tomorrow at the same effort. For this reason, linking RPE scores to heart rate zones can be useful for session interpretation and planning training load.

Using training load to improve performance.

Training load can be used to plan, interpret, manipulate, and monitor training. External loads like power or pace can be used to constrict training within certain “zones” to get a desired internal response. Distance and/or time can also be used to limit the volume of work done. The internal responses can be analyzed and used to progress training and monitor training status.

Here are four principles to consider for endurance training load:

1. Progressive overload – do not do too much too soon
2. Functional overreaching – stress your systems just enough to get an adaption to your training
3. Reversibility – your adaptions can be lost with a break in training
4. Specificity – you need to target specific systems within a training session

Acute and chronic training load

Acute load refers to new work done, and chronic load refers to a sum of past work done. Your chronic training load is a good indicator of your capacity to do work, hence why it may be called “fitness” on many programs. When thinking about load we consider an athlete’s chronic load (using different formulas) and decide what sort of acute load they can do. This is useful for session planning, injury prevention, and peak performance planning. To be pragmatic in getting this concept across, all we can say is that you should not stretch yourself too far beyond your current capacity; you will likely end up in a state of over-training and miss out on your best performances at your races.

Final thoughts

To end off with, a common belief in the endurance world is that training volume should not be increased by more than 10% per week. Whilst the concept is wise, it is poorly understood. If you progress your load of 30km running per week, that means you will run 33km next week. Distance alone is an external load (volume) and has no internal load variable. Rather, we suggest you consider the concepts discussed above as a tool for deciding how much to progress your load each week. Consider sessional targets of volume or pace/power in alignment with responses such as heart rate. Then you will be able to progress enough to get you the fitness adaption you want, without compromising on your performance.

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Happy training!
Team Coach M