Quantifying Training Load
An important principle of training is the concept of overload, recovery and super-compensation and it is important to consider how to measure these in order to structure your training effectively.
When we exercise, the body endures a certain amount of physical stress which disturbs the normal balance of the physiological systems, or what is known as homeostasis. Following a period of recovery the body not only restores the previous state of homeostasis but is stimulated to incur further adaptations so it is better prepared for the next time we exercise. Successive bouts of training result in overload, or overreaching, which, provided it is optimally applied and balanced with adequate recovery, results in superior gains in fitness known as ‘super-compensation’.
It doesn’t require scientific knowledge to understand this principle. As legend has it the ancient Greek wrestler Milo of Croton carried a calf every day from its birth so that as it grew, so did his strength. Eventually he could lift a full-grown bull. He also understood the need for recovery, eating an extraordinary diet of many kilos of meat and bread along with wine and the gizzard stones of cockerels! Of course these days we know much more about the underpinning science, but the approach is still the same: design a training programme which has a progressive and achievable increase in load, schedule adequate recovery, and re-fuel.
Rating Training Load
The overall training load is dependent upon three factors: the frequency, duration and intensity of training. An elite athlete may train with a high frequency sometimes completing two or even three sessions per day, but because they are accustomed to training and capable of dealing with high loads they are able to recover from training within a matter of hours. On the other hand a beginner may only cope with training every other day. The only rule is to experiment and see what works best for you - everyone is different.
In the old days cyclists often used to measure the overall load in terms of hours or kilometres ridden. Neither of these metrics is adequate as they do not take into account how hard you are working so it is better to incorporate a measure of intensity such as power or heart rate. There are a number of software packages that provide an estimate of overall training stress and you may well have heard of TSS (training stress score), ACT (acute training load) and CTL (chronic training load). These measures provide a reasonable indication of overall load, but the algorithms do have some shortcomings so they should not be blindly followed without considering other factors such as perception of effort and the physical and psychological manifestations of fatigue.
A very simple and effective approach, which is used at all levels including elite cyclists, is the Session RPE (rating of perceived exertion). Simply rate the average intensity of the session according to the 10-point category-ratio scale (see here) and then multiply the score by the number of minutes completed. Most athletes are good judge of how hard they have worked so this low tech, simple method is surprisingly effective.
Rating Fatigue
All good coaches know to simply ask their riders each day, ‘How are your legs?’ and they usually get all the information they require. This type of qualitative assessment can be combined with more objective measures of training stress to build a better picture of how you are coping with training.
The simplest of these is to take the resting heart rate in the morning after waking. If the heart rate rises significantly from normal it may be a sign that you are ill or poorly recovered. A more sophisticated tool is heart rate variability which measures the beat to beat differences in heart rate. A healthy, well-recovered athlete would expect a high degree of heart rate variability, but if it falls and remains depressed over several days this might indicate non-functional overreaching (as opposed to an optimal functional overreaching) and the need to take some recovery. This technology has been incorporated into heart rate monitors and phone apps that advise you when to train or rest.
Even the training itself can be used to judge fatigue. It is not uncommon for track riders to cool down and go home following the first couple of intervals within a training session if they are unable to hit the target numbers. Their intervals can be so intense that there really is no point in continuing if the desired training stimulus cannot be elicited.
In a similar fashion, endurance riders can employ a ‘readiness to train test’ at the start of a ride. If in conjunction with an elevated RPE their heart rate is significantly different from that which they would normal expect at a given power output then that day’s training needs to be altered or abandoned in favour of rest.
The Lamberts Sub-Maximal Cycling Test (LSCT) is a more sophisticated version of this test and can be performed on the road or on the indoor trainer. It is easily used as a warm-up prior to an interval training session and is best performed after a recovery day. The test also incorporates heart rate recovery. Interestingly, one would expect heart rate recovery to be blunted during times of fatigue, but in fact the opposite happens and heart rate returns to resting levels much quicker following exercise. You should accurately record your data following every test and over time you will develop a good picture of your response to varying training loads.
Summary
Balancing training load with adequate recovery is critical to maximise gains in fitness whilst minimising the risk of non-functional overreaching or even chronic overtraining which can be hugely debilitating. Measuring overall training load and evaluating the resultant fatigue will help you to set challenging, but achievable training. There are a number of metrics you can use to do this - hopefully this article gives you an idea of the most useful ones.
