Overtraining symptoms: 8 signs and what else could be behind them

Overtraining symptoms include a resting heart rate that stays high for weeks, fatigue that rest days do not fix, and worse sleep. You also catch colds more often, and your performance drops while you train harder. The awkward part is that those same signs fit iron deficiency, an underactive thyroid, low vitamin D, or simply eating too little.

So the symptom list is the easy part.

What I notice as a training partner: almost everyone who calls themselves overtrained reached that conclusion too fast. They never ruled out a single alternative. Below are eight signs. For each one you get when it fits overtraining, what else it could be, and the value that separates the two.

1. Your resting heart rate stays elevated for weeks

A resting heart rate five to ten beats above your normal fits overtraining. Especially when it stays there for weeks. But it also rises with iron deficiency, an infection you have not noticed yet, or a bad week of sleep. Your heart is covering for something.

The question is not whether it is up. The question is why.

With iron deficiency your oxygen transport drops, and your heart rate fills that gap by beating more often. This happens before your haemoglobin is officially low, because ferritin falls earlier than your blood count does. Iron deficiency is more common in athletes than in the general population, with endurance athletes and women most at risk (PMID 31055680).

What to do: put your morning heart rate next to your training log before drawing conclusions. More on the value itself in resting heart rate and recovery and iron deficiency in athletes.

2. Fatigue that rest days do not fix

This is the sign most often misread. Fatigue that clears after two or three rest days is ordinary training load. Fatigue still there after a full rest week is something else. That does not automatically mean overtraining, because an underactive thyroid produces the same picture.

A slow thyroid makes you tired, cold and sluggish, and rest does not touch it. Two values separate them: TSH and free T4. This is exactly why blood testing has value here even though no overtraining test exists. It rules suspects out.

What to do: write down how many true rest days you took and whether things improved. That single data point settles most arguments. See also underactive thyroid symptoms.

3. Your performance drops while you train harder

Persistent underperformance despite rest is the core sign of overtraining. It also has the most annoying competitor: eating too little for the load you are carrying. That is called low energy availability, and it looks almost identical.

Picture two athletes who both get slower over 8 weeks. The first trains eleven hours a week and eats accordingly. The second trains those same eleven hours and has been in a mild deficit for months while cutting. For the second one the problem is not the volume. It is the fuel.

The IOC describes this as a syndrome affecting hormones, bone and performance, not a deficit you can spot on the scale (PMID 37752011). In men testosterone can move with it. In women the cycle usually changes first.

What to do: honestly count a week of intake against your training hours before you change the programme.

4. You keep catching colds

Getting ill more often fits a heavy training block, and it fits low vitamin D. In the Netherlands that difference is largely a question of season. RIVM tracks the vitamin D status of the population. It runs lower in winter than in summer, because less sunlight reaches the skin.

If you fall apart every November and never in April, your training schedule is probably not the variable that changed.

Vitamin D plays a role in muscle function and immune defence. The effect of extra intake on performance is smaller than often assumed (PMID 29368183). The value here is vitamin D (25-OH).

What to do: check whether your colds follow a seasonal pattern. More in frequent colds when you train hard and vitamin D deficiency in athletes.

5. Sleeping badly while you are exhausted

Being wiped out and still unable to fall asleep is one of the most reported complaints in overtraining. It is also what happens with stress outside sport. Or with coffee late in the day, or a session too close to bedtime. All four feel the same.

Sleep here is not a standalone symptom but an amplifier. Sleeping badly lowers recovery, which makes training feel heavier, which makes you sleep worse.

What to do: move the two easiest things first. Your last coffee, and the timing of your hardest session. Do that before you rebuild the whole block.

6. You are irritable and your motivation is gone

Losing the appetite for a session you normally enjoy is a real sign. It gets dismissed as attitude far too often. In overtraining, mood often shifts before performance does.

The trouble is that a busy stretch at work does exactly the same thing. That is how stress works: your body adds training load and life load together without telling them apart.

What to do: check whether the dip lines up with something outside the gym. A deadline in the same week is not a coincidence.

7. Muscle soreness that lingers far longer

Soreness lasting three or four days instead of two fits incomplete recovery. It also just fits a session you had not done in a while. Eccentric loading, the braking part of a movement, produces the largest and longest response.

The matching value is creatine kinase, and it is almost always elevated after a hard session. That makes it useless as proof of overtraining, and useful as a measure of muscle damage.

What to do: compare against the last time you did that same exercise. See high CK explained.

8. Your appetite and weight shift

Losing your appetite while training hard is a classic sign, and unintended weight loss goes with it. Both fit overtraining, and both fit an energy deficit or a thyroid that is off.

This is the sign people ignore longest, because losing weight rarely feels like a problem.

What to do: record your weight weekly at the same moment, so a trend becomes visible instead of noise.

How do you know for certain that you are overtrained?

With certainty: not from a single test. Overtraining syndrome is described in sports medicine as persistent underperformance despite adequate rest, established by ruling other causes out. The joint statement from the European and American sports medicine bodies gives no cut-off value, because there is none (PMID 23247672).

Blood testing does something different here from what people hope. It rarely names the culprit, but it crosses suspects off.

Hormone research in athletes with overtraining syndrome shows the same thing. Baseline hormone levels were mostly normal. The problem only showed up under stimulation testing (PMID 28785411). So a normal result rules nothing out, and an odd one proves nothing. How the individual markers behave is covered in recognising overtraining through your blood values.

What is the difference between overreaching and overtraining?

The difference is how long you need to come back. After a hard block you feel temporarily worse and recover fully within days to a couple of weeks. That is functional overreaching and it belongs to training. If it drags on for months, it is called overtraining syndrome.

Which means you only know afterwards which one it was.

So the practical question is not which label fits, but whether you take the rest that makes the distinction possible. See also the deload week.

How long does recovery from overtraining take?

It varies widely, from several weeks to several months, and it depends on how long the situation had been running. There is no fixed schedule. The pattern is consistent though: the later it is recognised, the longer it takes.

My advice stays simple. Treat a persistent dip as information, not as something to train through.

What to do this week

Take the table and mark which of the eight signs you recognise. Then look at the middle column, not the left one. Is there a suspect in there you never ruled out? Then that is your next talk with your GP, not your next training tweak.

Do one thing this week: record your resting heart rate for seven consecutive mornings before you get up. A number with a line under it says more than a single reading.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

References

• Meeusen R, et al. Prevention, diagnosis, and treatment of the overtraining syndrome: joint consensus statement of the European College of Sport Science and the American College of Sports Medicine. Medicine and Science in Sports and Exercise, 2013. PMID 23247672.
• Cadegiani FA, Kater CE. Hormonal aspects of overtraining syndrome: a systematic review. BMC Sports Science, Medicine and Rehabilitation, 2017. PMID 28785411.
• Sim M, et al. Iron considerations for the athlete: a narrative review. European Journal of Applied Physiology, 2019. PMID 31055680.
• Owens DJ, Allison R, Close GL. Vitamin D and the athlete: current perspectives and new challenges. Sports Medicine, 2018. PMID 29368183.
• Mountjoy M, et al. 2023 International Olympic Committee consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine, 2023. PMID 37752011.