November 11, 2025, 3:04 am | Read time: 5 minutes
Among ambitious athletes who train intensively, overtraining is either denied or feared. What are the first symptoms? What to do if it happens? Does one become more susceptible to physical overload reactions with age–and should training be adjusted accordingly? FITBOOK explains all this with the help of sports scientist and personal trainer Jörn Giersberg.
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What is Overtraining?
Suddenly, performance levels drop, you feel weak, and the immune system seems to falter. Overtraining can manifest in various ways, but it always describes an overload reaction of the body to excessive training volume and intensity or insufficient recovery time. “Overtraining is an intense process where the biochemical balance, the homeostasis, is significantly disturbed. Athletes train too much over several weeks, overexert themselves, and neglect recovery. This disturbed balance of stress and relief leads to overtraining in the long term. Often, short-term fatigue symptoms are misinterpreted as overtraining,” explains the sports scientist.
Signs of Overtraining
Everyone reacts differently to external stimuli. This individuality is also reflected in the symptoms of overtraining. According to Giersberg, performance often stagnates or even decreases in such cases. Increased susceptibility to infections and sleep disturbances can also be signs of overtraining.
Additionally, overtraining can lead to mental changes: fatigue, lack of motivation, and disinterest in training. “But physical changes, such as headaches, an increased resting heart rate, and wear and tear on physical structures, can also be precursors of overtraining,” adds Giersberg.
Decline in Cognitive Performance
An analysis of seven studies, all dealing with overtraining, found that cognitive performance significantly deteriorates in overburdened endurance athletes. The reaction time was particularly noticeable–it was up to 20 percent slower in overtrained athletes compared to the control group. It also showed that overburdened athletes were more prone to impulsive behavior and preferred short-term rewards over more sensible long-term decisions.1
If you notice such changes in yourself, take a break with less training–your mind will thank you, as we’ve seen.
What to Do if It Happens?
If you’ve fallen into the trap and the overload reaction is present, the expert says the question arises: What can or must I do now to recover from overtraining?
“Strength training always means triggering anabolic, or muscle-building, processes in the body. In overtraining, the hormonal environment shifts to catabolism, which is associated with muscle-breaking processes. The result is that catabolic hormones flood the body, and muscle-building processes have no chance to prevail,” explains Giersberg.
The sports scientist advises consciously taking a break from training for several weeks. This “forced break” should ideally be both physical and mental. The mind needs to distance itself to allow for conscious recovery. Giersberg recommends active rest, such as light activities like walking, to stimulate metabolism.
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Does Age Make You More Susceptible to Overtraining? And Can You Counteract It?
Incorrect training execution, minor injuries, and very high training volumes: What the body can still compensate for in youth becomes more difficult with age. The tolerance threshold for overtraining decreases. Giersberg: “Training always works the same–whether someone is 18 or 80 years old. The body is stressed, recovers, and becomes stronger during the break. Due to the aging process, recovery times are extended–both between individual sets and between training sessions. The body needs longer to recover to maintain building processes.”
What many do not know or at least do not want to admit: Physical “decline” does not begin only at the age of 50. As early as the early 30s, the body slowly starts to break down muscle cells. Both the number and size of the cells decrease. The reason: The transmission of stimuli to the muscles worsens because the motor nerve pathways atrophy. Conversely, the remaining nerves must stimulate larger muscle areas and are more susceptible to high loads.
»From 30, Ten Percent Less Muscle Mass Annually
Regular training can intervene at this point, emphasizes Giersberg. Provided you don’t overdo it: “From the age of 30, the body loses ten percent of muscle mass per decade. Strength athletes can reduce this loss to two percent through regular training. One reason for this is the declining hormone production, which directly affects anabolism.”
At What Age Should You Adjust Your Training to Reduced Load Capacity?
Giersberg advises: “First and foremost, you should allow the aging process in your mind and not try to fight it with all your might.” High-performance athletes who have worn themselves out at a young age will probably notice the aging process as early as 30 because the body can no longer tolerate the training volume. However, moderate training can be continued into old age.
Important: By the mid-40s at the latest, training should be adjusted to reduced load capacity.
»Those Who Train Smart Stay Fitter in Old Age Than Their Peers
“A change in thinking is worthwhile,” says the sports scientist. “The final tally is made at the end, and especially those who train smartly in strength sports regain a lot in old age and stay fitter and younger than their peers.”