Fitness culture glorifies intensity: no pain, no gain. But what happens when that push turns into a problem? Overtraining syndrome (OTS) is real - and it’s backed by science. 

When I first got into running in my early twenties I fell in love with it, but I had never played sports before or ran more than a mile in my life but within a few months I was doing 6 mile runs in an hour and feeling great. I lived in New York City and would run before work, then rush to take a shower, get ready, and put on my heels to walk around the city for the rest of the day. After a few months of this, I was out on a run a couple of miles from my apartment and it felt like the muscle in my foot just broke in half - I ended up with plantar fasciitis and completely had to stop my newfound love tht day, and the pain in my foot still flares up today. It really is a mistake you don't want to make. 

Pushing your body too hard without proper recovery doesn’t just stall your progress - it can derail it entirely. We’re talking chronic fatigue, hormone imbalances, and even long-term injury. Here’s what science says about the signs of overtraining, why it happens, and how to stop it.

1. You’re Not Eating Enough for Your Output

High-intensity training burns through calories quickly. But if you’re not refueling properly, you’re setting yourself up for trouble. Inadequate nutrition during intense training schedules can deplete glycogen stores and lead to Relative Energy Deficiency in Sport (RED-S), a condition that impairs performance, metabolism, and recovery [source].

Consistent calorie deficits during overtraining can cause:

• Nutritional deficiencies – leading to fatigue, weakness, and anemia.
• Hormonal disruption – particularly in thyroid and reproductive hormones.
• Increased injury risk – as under-fueled muscles become weaker and more prone to strains.

👉 Science says: When training intensely, athletes should aim for a balanced diet rich in complex carbs, lean protein, and healthy fats to prevent energy depletion [source].

2. Persistent Soreness and Injury

Feeling sore after a tough session is normal. But if you’re always in pain, you’re overdoing it. Chronic muscle soreness without full recovery is a hallmark sign of OTS. Overtraining causes micro-tears in muscle fibers faster than your body can repair them, increasing your risk of strains, sprains, and overuse injuries like stress fractures [source].

Common overuse injuries from overtraining:

• Shin splints
• Tendinitis
• Plantar fasciitis
• Stress fractures

If you’re dealing with recurring pain or lingering injuries, consulting orthopedic surgeons is a smart move. They can identify underlying issues, recommend treatment plans, and help prevent long-term damage.

👉 Science says: Consistent muscle pain without recovery time indicates your body is in a catabolic state (breaking down tissue faster than it repairs) [source].

3. Chronic Fatigue and Performance Decline

Fatigue that doesn’t improve with rest is a red flag. Overtraining causes dysregulation in the hypothalamic-pituitary-adrenal (HPA) axis, resulting in elevated cortisol levels and impaired recovery. This chronic stress response leads to systemic fatigue, reducing both physical and mental performance [source].

Signs of fatigue from overtraining:

• Decreased strength and endurance
• Slower reaction times
• Reduced coordination and focus

👉 Science says: Long-term fatigue from overtraining can reduce mitochondrial function, lowering cellular energy production [source].

4. Disrupted Sleep Patterns

Overtraining throws your sleep cycle into chaos. Elevated cortisol levels and nervous system overstimulation can make it harder to fall and stay asleep. In turn, poor sleep impairs muscle recovery, slows down cognitive function, and weakens your immune system [source].

Signs your sleep is impacted by overtraining:

• Difficulty falling asleep despite exhaustion
• Waking up frequently or feeling unrested
• Night sweats or disrupted REM sleep

👉 Science says: Overtrained athletes often experience reduced sleep quality due to nervous system dysregulation and elevated cortisol levels [source].

5. Loss of Appetite and Weight Fluctuations

Training hard usually makes you hungrier, but OTS can blunt your appetite. Overtraining dysregulates ghrelin and leptin - hormones responsible for hunger and satiety - causing reduced appetite despite higher energy expenditure. In the long term, this hormonal imbalance can lead to unintentional weight loss and muscle wasting [source].

Signs your appetite is being impacted:

• Loss of interest in food, even after intense workouts
• Unintended weight loss or fluctuating weight
• Digestive issues from chronic stress

👉 Science says: Leptin levels decrease and cortisol rises in overtrained individuals, reducing appetite and promoting catabolism [source].

How to Prevent and Recover from Overtraining

If you’re hitting these warning signs, it’s time to take recovery seriously. Science-backed strategies include:

• Prioritizing sleep: Aim for 7-9 hours of high-quality sleep per night.
• Deload weeks: Scale back intensity and volume every 4-6 weeks.
• Active recovery: Incorporate yoga, walking, or light mobility work.
• Balanced nutrition: Ensure you’re consuming enough carbs, protein, and fats to meet your training demands.
• Rest days: Give your body time to recover - rest is as important as training itself.

Overtraining doesn’t make you tougher - it breaks you down. If you’re seeing signs of fatigue, soreness, or performance dips, science says it’s time to hit the brakes. More is not always better. In fitness, smarter always wins.