Runners and resting – should I train without having a rest or should I have a bit of resting during season?

Runners and resting – should I train without having a rest or should I have a bit of resting during season?

At work I’m often confronted with athletes’ dilemmas and questions related to “losses” they experience when they can’t train or simply don’t train. The reasons can vary. Among the most common are work- and family-related duties, illness and, in the worst case, injury. What’s going on when you’re not training, how much time do you need to regain the previous shape – I’ll answer all of these questions in this article. Researches made on runners are hardly accessible or relatively hard to find, so I used similar researches which deal with the state of our body when “compulsory” resting is needed.

“Detraining” is defined as a period completely or partly without training which doesn’t cause an adaptation on existing stimulus in organism. “Detraining” is related to various injuries which affect motor and physical skills of athletes and prevent them to continue their trainings. In the following section, I’ll outline what kind of “losses” appear in aerobic and muscular endurance, which is the most important part of the runner’s training. Let me first explain that the point is not in constant training. After every season is finished you have to rest at least for four weeks, because the body has to regenerate. If you skip the transitional part, you definitely won’t be very successful in the next season.

To recreational runners the levels of oxidative enzymes in muscles, VO2max or lactate are not important. Pleasure and love for running are what it really counts. Let the article enrich your knowledge, so you’ll know what happens when you’re not training.


The heart muscle is tightly related to aerobic endurance and strengthens with every pulse, higher than 55% of the maximal pulse, and activities that last longer than 20 minutes. An activity that lasts long enough can cause an adequate adaptation of functional system. The research that I’m going to present was conducted in the USA and analyzed two well trained and three average-trained swimmers who, after a period of long-lasting training, rested for 20 days.

In 20 days of rest:

  • submaximal heart frequency has increased drastically,
  • ejection fraction of the heart decreased by 25%,
  • oxygen consumption decreased by 27% (VO2 max).

Decreased ejection fraction and oxygen consumption (VO2max) are consequences of decreased blood volume, blood plasma and ventricular contractile. It’s interesting that the better the shape of the test subjects (athletes) was the bigger were losses in oxygen consumption. This means that the better shape you are in the more you lose. But that’s not always bad. The research showed that after 20 days of resting the subjects had better results in oxygen consumption in the first 35 to 60 days of training. All individuals had better measurement results considering the previous state. It’s gratifying that resting caused a complete regeneration, which contributed to better VO2max results. This means that after resting you’ll be even better machines for the next season.

The second research was conducted on 7 female athletes. The research started after the end of the season and lasted for 3 months. In that time the girls were occupied with daily schoolwork and PE. Their oxygen consumption (VO2max) has decreased by 15.5%, which means that in these 3 months their VO2max was on the same level as the one of their non-athlete peers. In conclusion, the oxygen consumption definitely decreases due to inactivity, which means that aerobic endurance is worse. Researches also show that at least three training sessions a week at 70% of VO2max assures the maintenance of aerobic condition.

Muscular endurance

Beside aerobic endurance, a functional ability to endure long-lasting exertion, muscular endurance is important as well. The ability to endure exertion (interval, sprint, uphill running) decreases already in the first two weeks of resting. The differences between the VO2max and the enzymes in muscles and glycogen are bigger than you would expect. Let me complicate this thing. In short: training causes different adaptations of the organism – adaptation to aerobic endurance and adaptation of heart and respiratory system are crucial to runners, but not only that. The enzymes also have an important role in the body. Researches have shown that the levels of VO2max have increased by 25% in the first two months, but in the following four months by only 2–4%. So, the question is – why train for ten months if you reach the peak in the first two months? The answer is – because of the level of enzymes which increases simultaneously with the amount of training. From first to seventh month of training the level of an enzyme called SDH (Succinate Dehydrogenase), an important oxidative enzyme in muscles, increases by 800%. Why am I telling you this? Because its levels after two weeks without training is considerably lower, including oxidative cytochromes, by 40–60%. What are the consequences? Lower speed, lower adaptation to the lactate and lower borderline lactate level. In short – you are not what you’ve been before the (compulsory) rest anymore.

Findings about glycogen – at athletes four weeks of rest decrease supplies of glycogen by 40%. At inactive people there’s no change, if they rest 😉!

Findings about lactate – five months of training are followed by four weeks of rest. The swimmers are tested every week at 183m of distance (200 yards). Every week the level of lactate increases from an average 4.2 mmol/l to 6.3 mmol/l, then to 6.8 mmol/l and in the fourth week reaches 9.7 mmol/l. This means that you’re becoming “sourer” every week you don’t train

What’s the conclusion? During the time when you can’t train significant changes occur, that are the most distinctive in the first two to four weeks. Which is not ideal! However, researches have shown that the athletes got back in a good shape very quickly. So, don’t worry. If you’ll train well even after rest, you’ll get good results. Probably even better than before the rest, at least in terms of oxygen consumption.

Marko MRAK


Physiology of sport and exercise (third edition) – Wilmore, Costill – Human kinetics 2004

Essentials of strength training and conditioning – Baechle, Earle – Human kinetics 2004


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