How Much Will I Lose, if I Stop Training Through Illness or Injury?

Recently I had a client come to me and ask ‘how much will I lose, if I stop training through illness (holiday or injury)?’ He had unfortunately picked up a cold from one of children and was worried that if he took a few days off training then his fitness would collapse. I suggested that he should rest firstly and then come back to training after his cold had gone. His worry about his decreasing fitness level may not have been something to worry about if his cold lasted a short period of time. In fact over a short period of time his ‘race fitness’ may actually improve, based upon the theory of super-compensation. However, I did give him a warning that if he was ill (you should never train with a cold that has symptoms at or below the neck) and not training for a longer period of time than a week his fitness may indeed start to reduce.

I looked into this for him and found some numbers to quantify how much he may lose if he was out of training for more that three weeks. I found a study by Wilber and Moffatt (1994) in their study they found that in three weeks of interrupted training resulted in the following changes in the physiology of the body.

Measure of Fitness Change
Aerobic Capacity -8%
Heart stroke volume (blood pumped per beat) -10%
Sub-maximum heart rate (beats/minute0 +4%
Blood plasma volume -12%
Muscle capillary density -7%
Oxidative enzymes -29%
Blood lactate during exercise +17-120%
Lactate threshold +88%
Use of fat for fuel during exercise -7%
Muffins -52%
Time to fatigue -10%

If at any time you were to stop training your body would start to revert back to an untrained state. Your body requires a stimulus (provided by the intensity, frequency and duration of training) to maintain it’s current fitness level. If you have a training interruption you may not receive this stimulus and this would start the detraining effect (a reduction in your fitness levels). Typical forms of interruptions to training include illness, injury, burnout, over-training, work commitments, family worries, study periods etc. All of which have the ability to stop you from training. Athletes that are more highly trained will lose their fitness more quickly than less trained individuals (so beware you elites).

The key to reducing the effects of detraining is to provide your body with the minimum stimulus to maintain your fitness level and allow your body to recover. A prime example of this is when a cyclist wishes to ‘Taper’ before an event (a taper is a period of reduced training to allow the body to recover before a key race) if they rest but stimulate the body enough through specific training sessions, resulting in the body not detrain but increase its fitness levels (this should only be carried out if you do not have a cold).

So if you have limited time for training you should be looking to complete the minimum of training to maintain your fitness level. I suggest you talk to me about this kind of training if you have a busy period coming up.

His next question was ‘how long will it take for me to get back to my previous level of fitness?’ I suggested to him that it would take longer than the length of his illness. Unfortunately you need to retain your self back up to the level you stopped at, how much and how long will depend upon the type of training you have been completing during you time off. If you managed to get out and do some riding then it would take less time for the changes to take place than no riding. In general it may take up to twice as long as the time off to get back to full race fitness.


Wilber, R.L, and Moffatt R. J, (1994),Physiological and biomechanical consequences of detraining in aerobically trained individuals. Journal of Strength Conditioning Research. 8:110.

Dan Bennett

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