Although sports performance depends largely on technical, tactical, and physiological factors, other variables such as injury resistance and the athletes’ continuity also play an important role. Injuries are one of the biggest concerns in sport. The absence of an athlete not only affects them at an individual level, but it also has significant consequences for the team, as it compromises training at a tactical level because the injured athlete must temporarily refrain from competing—which will ultimately affect the performance of the team.1 For example, 30% of sports injuries involve 1 to 3 weeks of inactivity. Besides, the interruption in an athlete’s training as a consequence of illness or injury will lead to a process called detraining. It means that the athlete will suffer partial or complete loss of training-induced adaptations in response to insufficient training stimulus. This includes weight gain, strength and muscle mass loss and deterioration of cardiorespiratory fitness, among others.

There is evidence that relatively short periods—even days—without training are enough to cause detraining. Thus, as in the case of young and healthy people (~20 years old on average), it only takes two days of leg immobilisation to lose almost 2% of mass muscle, whereas a 3.5% and 9% loss of muscle mass and strength, respectively, can occur in 5 days. In addition, a recent study published in Plos One showed that two weeks without training during the post-season break are enough to reduce semi-professional football players’ performance in a high-intensity intermittent test, although it was not enough time to cause deterioration in other markers, such as strength or repeated sprint ability. In a systematic review published in Sports Medicine, the authors stated that strength levels can be maintained even during 3 weeks of detraining, but longer periods (~7 weeks) will result in about 14.5% and 0.4% losses of strength and power levels when it comes to elite rugby and American football players.

The Consequences of Detraining Derived from the Pandemic

Within the current context of the pandemic, athletes have also had to adapt themselves to exceptional situations. Thus, during the state of alarm that was proclaimed in much of the world, they were forced to interrupt their season and put their regular training on hold. Even today, many athletes are still cancelling their regular training during a few weeks as they have to stay in quarantine like many other people. In this sense, the results of the studies with models of detraining similar to the situation experienced during confinement (for example, the reduction in the number of daily steps, that is, the levels of daily physical activity), makes it possible to obtain a better understanding of the physiological deterioration that athletes are exposed to during quarantine. Therefore, adults (~36 years old) considered physically active (>10,000 steps per day) who reduced their number of daily steps by 81% and increased their daily sedentary time by ~4 hours for 14 days showed deterioration in their cardiorespiratory fitness and their lower extremity muscle mass, as well as in cardiometabolic health markers.8 Similarly, a study that examined the effect of 14 days on a group of young people who significantly reduced their levels of physical activity from an average of 10,500 steps to 1,400 steps (similar to what happened during confinement), showed a 7% loss of maximal oxygen consumption and a 3% loss of leg muscles mass, although not of the arms or trunk. This showed that, as seen in a recent study on the consequences of confinement in elite badminton players, athletes’ performance and autonomic nervous system (the latter analysed through heart rate variability), were affected despite continuing to train in their homes, with losses ranging from 6.5% to 11.5% in diverse tests, such as jumping or maximum strength in squat, respectively.

Therefore, detraining produced as a consequence of a few weeks of cessation (whether by injury or illness, holidays, or home confinement), will be a great hindrance to the preparation of any athlete, especially for elite ones, not only affecting their performance, but most likely also entailing a high injury risk. For example, in different sports, it has been observed that there is an injury rate between 2 and 3 times higher during pre-season training than during competition, being athletes’ physically deconditioning after holidays, one of the main reasons for this higher injury rate.16 Another clear example is the one occurred after the NFL lockout, which lasted more than 3 months and during which athletes were not able to train as usual.17 Over the first 12 days back after the break, 10 Achilles tendon injuries were reported, whereas an average of 5 injuries of this kind previously occurred during the whole season.

Conclusions

It is important to be aware of the significant adverse effects that occur as a consequence of sports breaks following injuries, holidays, or confinement, and try to reduce as much as possible the cessation of physical exercise. Besides, when it is inevitable, we will apply nutritional (increased intake of protein, creatine, HMB, etc.) and physical strategies (traditional training or alternatives such as electrostimulation, vibration, or voluntary isometric contraction when limb immobilisation prevents us from exercising), in order to avoid the negative effects of detraining.

Javier S. Morales

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