How Your Body Adapts to Training – General Adaptation Syndrome
Training is defined as an athletic task that stresses your body’s homeostasis to trigger positive physiological adaptation.
In simple terms, after a training session, your performance will first decrease to a point (depending on how hard the training sessions was) and then slowly increase until your body has adapted, leading to improved performance. This physiological principle was first described in 1936 by Hans Selye and it is known as the general adaptation syndrome (Figure 1).
Figure 1: A diagram describing effect of training stress upon performance, as described originally by Hans Selye in the general adaptation syndrome.
Applying General Adaptation Syndrome to Your Training
The simplified explanation of the general adaptation syndrome shown in Figure 1 consists of an alarm phase and a resistance phase. In brief, the alarm phase is the body’s initial response to the training stress and may be demonstrated by performing an extremely hard session or effort two days in a row. This will normally lead to a worse performance on the second day.
The resistance phase is the phase after the body has responded and adapted to the training stress. During this phase a repeated very hard effort will lead to an improved performance.
Stressors External to Training Must Also Be Accounted For
When we think about the general adaptation syndrome and stress in the context of training, we can’t exclude the effects of other sources of stress on your body. Stress, whether it is training stress or work stress, accumulates and may prolong the alarm phase, or even blunt the resistance phase.
Therefore, if you responded positively to 3 days of rest between key hard training sessions in the past, you may need more recovery if you have had a couple of late nights with a lot of work stress.
A good training program consists of very hard sessions that are only repeated once you’ve recovered and are within this resistance phase. There really is no way to know when you are within this phase until you analyse a specific session retrospectively.
Frequent analysis will inform you about your body and how it recovers from specific training sessions. Everybody responds differently to training stress. For example, you train with a partner on Tuesday, then you both perform the same session on a Thursday and your training partner feels great – seemingly has improved – but you feel sluggish, tired, and simply can’t sustain the same power you did two days before.
This is a perfect example of two people responding differently and highlights the importance of data analysis to understand training load, recovery and positive session adaptations. When we think about General Adaptation Syndrome, we must never exclude the effects of non-training (life) stressors on your body. We have covered this extensively in our Monitoring Training Load articles, in particular part 2 which covers internal load monitoring,submaximal fatigue tests and subjective wellness.
How to Analyse Your Training Session
What practices allow us to best analyse training data and measure improvement? Commonly, hard training sessions consist of interval sessions. The major advantage of training with a power meter is that it provides you with an exact, objective measure of your performance.
For Interval Sessions, Calculate Your Session Average
If you do a 3 x 10 minute interval session, and you achieve 410W, 398W and 388 watts for the 3 respective intervals, your session average is 399 watts. It becomes harder to measure performance objectively when you are not training with a power meter. Measures such as speed and distance may be affected by the wind and other factors.
Below is an example of analysis for two different interval sessions:
Figure 2: A diagram showing session analysis of all 4 minute (typically 6 x 4 minute intervals with 2.5 minutes rest) and 2 minute intervals (8 x 2 minute intervals with 90 second rest) that a certain athlete has performed. These sessions are analysed to ensure that the session average (shown in pink and black by short dashes) improves from session to session.
Sticking to a standardised training session which is repeated allows coaches to compare apples to apples. It may seem monotonous to be repeating certain sessions, but it is difficult to compare 5 x 5 minute intervals to 6 x 4 minute intervals.
For this reason, session variance can sometimes be limited by the need to program the same session at a given interval, so that progress can be measured.
What should I do when I am not improving?
Referring back to Hans Selye, if training is not bringing on improved adaptations you are either not training enough (in which case you are past the resistance phase and detraining has occurred), or in most cases you simply have not rested long enough.
The most common error made by competitive, recreational, amateur and elite cyclists is that they simply do not include enough rest between training sessions.
Doing successive hard training sessions within the alarm phase, before your body has adapted to previous training sessions will eventually lead to a downward spiral of performance. Consistent lack of recovery can compound to the point where you are in a state of overtraining. When overtrained, prolonged rest is required.
Getting Out of an Overtraining Rut
In most cases simply including adequate rest & recovery sessions between hard sessions – ensuring that the easy days remain easy – this is usually enough to get most athletes out of an overtraining rut.
What about the days between interval sessions?
We have previously discussed the principle of polarised training. In brief, polarised training implies that your hard rides should be very hard and constitute approximately 20% of your training load. The remaining 80% should remain very easy. Therefore, in support of this principle, and in support of the general adaptation syndrome, ensure that the days between your hard interval sessions remain very easy and do not add significant training stress.
About the Author
Prof Jeroen Swart
S2S Coach & Head of Performance, UAE Team Emirates XRG
Jeroen is a professor of Sports & Exercise Medicine and Exercise Science, and co-founder of Science to Sport. With over 50 peer-reviewed publications spanning cycling physiology, performance testing and sports medicine, he brings a rare combination of clinical depth and applied coaching experience to athlete development.
He has coached leading international cyclists for close to two decades, and as Head of Performance at UAE Team Emirates XRG — the UCI's number-one ranked WorldTour team from 2023 to 2025 — has worked with three different Tour de France winners. Jeroen is also the architect of the ErgoFiT predictive bike fitting system, the only scientifically validated tool of its kind.
Credentials & Background
MBChB, MPhil (SEM), ACSEM, FFIMS, PhD. A multi-time South African national champion in XCO mountain biking, Jeroen's own competitive background gives him a first-hand understanding of the demands elite cycling places on the body — and the ways it can break down.
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