The Triathlete Blueprint Newsletter #119-Overtraining in Triathlon: How to Spot the Red Flags Before It’s Too Late

Yan Busset
Aug 9
6 min read

Read time: 6min.

By Coach Yan Busset

Overtraining: Recognising the Red Flags Before You Dig Too Deep

We’ve all heard about overtraining. Maybe it’s happened to you, or you know someone who’s been through it. In an endurance sport like triathlon, which asks a lot from your body, it’s something worth paying attention to. But most of the time, if you train correctly and monitor the right things, you’re already keeping an eye on what matters to avoid it, even without realizing it.

The first step to prevention is understanding that training alone is not enough to progress and stay healthy. You only absorb training when you recover. Recovery and proper fueling are not optional extras, they are part of the training itself. Once this clicks, you’ve already solved most of the problem. But knowing it and actually applying it consistently are two different things. Let’s go through what overtraining is, the red flags to watch for, and how to adjust your training load before you dig too deep.

What Exactly Is Overtraining Syndrome?

Overtraining Syndrome (OTS) isn’t just “feeling tired.” It’s a state where your body’s ability to recover can’t keep up with the training stress you’re putting on it.

There are different levels:

Functional Overreaching (FOR) – short drop in performance (days to a week or two) followed by a bounce-back when you recover.
Non-Functional Overreaching (NFOR) – longer fatigue, no real performance rebound.
Overtraining Syndrome (OTS) – months of reduced performance, often with mood swings, low immunity, and a complete loss of motivation.

You don’t want to wait until you’re in that last category.

Key Warning Signs to Watch

These are the red flags I tell my athletes to look out for:

You feel flat or sluggish in training, even after rest days
Elevated resting heart rate or a drop in HRV over several days
Sleep is short or low quality
Loss of appetite, or your weight starts dropping without trying
You’re more irritable, moody, or unmotivated than usual
You keep getting small colds or illnesses
Sessions feel harder than they should for the same effort
Difficulty getting your heart rate up to usual levels during training – a common sign of accumulated fatigue or early overtraining

How I Get Athletes to Track Recovery

Recovery values are as important as training sessions data. For me, tracking recovery it’s the best way to adjust workload and training stress, and to know if you’re actually absorbing the training. Because once again, it’s during recovery that you adapt and get stronger, if recovery doesn’t happen, all you’re doing is stacking fatigue.

Simple things you can log daily to spot patterns:

Hours and quality of sleep
Resting heart rate or HRV
Body weight
Your mood
Perceived difficulty of each session

The first three are objective data points. The last two – mood and perceived difficulty/efficiency of the session – are more subjective, but they carry a lot of value, especially when tracked over a long period of time.

Eating: The Fourth Discipline in Triathlon

Call it what you want, the silent killer, the missing link, nutrition is often the hidden factor that tips the balance between steady progress and burnout. And here, we need to look at it in two ways.

First, nutrition in general: giving your body all the macros and micros it needs to function properly day to day. This comes from your main meals and overall food quality. If your diet is poor in nutrients, you can start digging deficits that, over time, will push you closer to overtraining.

Then there’s fueling: meeting the energy demands of your training sessions. This is often where many triathletes go wrong. If you don’t fuel enough during training – especially during long workouts – you limit your performance in the session and slow down your recovery afterwards. Learning to take carbs on the bike or run, and even during longer swims, is a game-changer.

A big issue is the chronic underestimation of calorie needs. Many athletes end up under-eating, both in quantity and quality. That’s why one of the red flags I watch is body weight – not for aesthetics or performance numbers, but as a health and prevention metric. Gradual weight changes from improved body composition, such as gaining muscle and losing fat, are normal over time. Short-term fluctuations from hydration or dehydration are also common. What is more concerning are clear trends. A rapid drop in weight may indicate under-fueling, excessive calorie deficit, or illness. A rapid increase in weight could signal poor recovery habits, excessive calorie surplus, or water retention linked to inflammation or hormonal imbalance. In both cases, sudden shifts usually mean something in nutrition, training, or recovery is out of balance.

Don’t just wait until you feel bad to check in on your health. If you’re training and racing regulary, plan at least two key blood tests per year, timed with important points in your season, to make sure everything is on track. A coach is not and do not replace a doctor, so it is a must to have regular medical follow-up alongside your training program.

Rest Doesn’t Always Mean Doing Nothing

One mistake is thinking “rest” means lying on the couch all day. Sometimes that’s exactly what you need, and especially when you’re starting out, or when you feel you need it, it’s totally OK to take full days off. Often, that’s as much about a mental reset as it is about physical recovery.

There’s also active recovery, easy spins, walks, mobility work, gentle swims, which can help the body bounce back faster than total inactivity. The key is to keep it genuinely easy. Active recovery is not another sneaky workout in disguise.

Both are valid tools. It’s about discussing with your coach what’s best for your situation, and also listening to your body to make the call.

If You’re Already in Overtraining: What to Expect and How to Get Out

I hope you never get there, but if you do, here’s the reality. The deeper you are into overtraining, the longer the road back.

Functional overreaching can clear in days to a week with reduced load and better recovery habits.
Non-functional overreaching can take several weeks.
True Overtraining Syndrome? We’re talking months – sometimes a whole season – before you’re back to full capacity.

How to approach it:

Unload first – Cut training volume and intensity drastically. This is not the time for “just pushing through”.
Sleep and nutrition first – Extend sleep time if you can, and make sure you’re eating enough to support recovery.
Active recovery beats doing nothing (in most cases) – Light movement like easy spins, walks, mobility, or gentle swims can promote blood flow, maintain movement patterns, and help your head, without adding stress. Keep it genuinely easy.
Rebuild gradually – Once you feel your energy, mood, and resting metrics (HRV, resting heart rate, sleep quality) improving, start adding back volume and intensity very slowly.
Work with a sports doctor – Especially if you suspect you’re deep into NFOR or OTS, get medical guidance to make sure you’re rebuilding on a solid base.
Don’t rush the process – Coming back too fast is the easiest way to fall right back into the hole. Respect the time your body needs to reset.

Overtraining doesn’t happen overnight, and it’s not inevitable. If you learn to track the right things, fuel properly, and respect recovery as much as training, you’ll be able to keep progressing without hitting the wall.

Very often, we want to do more because we think that’s how we’ll progress. Of course, volume matters – but it has to be a volume that fits your personal situation, your family life, your work, your recovery capacity. Everyone is different. Too often, we try to copy others, or even the pros, and end up trying to absorb more than we can handle.

What really drives progress is being consistent over a long period of time. If you do too much, you break that consistency, and progress disappears. Sometimes we ignore the signs and push too hard. It usually comes from a good intention – wanting to improve – but “too much” ends up doing the opposite.

Don’t be afraid to back off. Sometimes that’s exactly what will help you progress more in the long run. It can be hard to understand at first, but that’s why having structure and guidance matters. An outside point of view, like a coach, can often help you make the right call when it’s difficult to judge for yourself.

Listen to your body, watch the trends, and when in doubt – back off before it’s too late. Triathlon is a long game. The aim is to stay healthy, consistent, and ready to race at your best.