The Adrenal Glands, HPA Axis and REDs: Understanding Stress in Athletes
Your body is constantly balancing stress and recovery.
Training is a form of stress. When managed correctly, this stress is positive—it creates a signal for your body to adapt, become stronger and improve performance.
However, when training stress is combined with inadequate fuelling, poor sleep and insufficient recovery, the body can struggle to maintain balance.
A key system involved in this process is the HPA axis.
The Adrenal Glands: Your Stress Response System
The adrenal glands are small glands that sit on top of your kidneys.
They produce important hormones involved in stress, energy and exercise, including:
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Cortisol
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Adrenaline (epinephrine)
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Noradrenaline (norepinephrine)
These hormones help your body respond to demands, whether that is a hard training session, a race, illness or everyday stress.
Cortisol: The Adaptation Hormone
Cortisol is often called the “stress hormone,” but it is not a bad hormone.
Athletes need cortisol because it helps:
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Release energy during exercise
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Maintain blood glucose
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Support the body's response to training
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Regulate inflammation
A healthy cortisol response helps you meet the demands of exercise and then return back to normal afterwards.
The problem is not cortisol itself—it is when stress signals remain high for too long without enough recovery.
The HPA Axis: How Your Body Communicates Stress
HPA stands for:
Hypothalamus → Pituitary Gland → Adrenal Glands
This is the communication pathway that controls your body's response to stress.
Step 1: Hypothalamus
The hypothalamus detects stress and sends a signal that the body needs to respond.
Stress can include:
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Exercise
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Emotional stress
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Illness
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Lack of sleep
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Low energy availability
Step 2: Pituitary Gland
The pituitary gland receives the signal and releases hormones that communicate with the adrenal glands.
Step 3: Adrenal Glands
The adrenal glands respond by producing cortisol and other stress hormones.
This system helps your body manage challenges and maintain balance.
Exercise, Stress and Adaptation
A well-designed training programme creates a controlled stress response.
You train → your body experiences stress → you recover → your body adapts.
This process helps improve:
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Strength
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Endurance
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Fitness
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Performance
Recovery is the step that allows adaptation to happen.
Without recovery, the stress signal continues to build.
How REDs Affects the HPA Axis
With low energy availability (LEA), the body does not have enough energy left after exercise to support all normal physiological functions.
The body interprets this as a stress state.
As a result, changes can occur within the HPA axis and other hormone systems.
This can contribute to:
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Altered cortisol patterns
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Increased perception of stress
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Poor recovery
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Fatigue
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Reduced performance
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Changes in reproductive hormones
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Increased injury risk
The body is not “breaking down”—it is trying to protect itself by prioritising survival over performance.
Signs Your Stress and Recovery Balance May Need Attention
Athletes should pay attention to patterns such as:
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Feeling constantly tired
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Declining performance despite training harder
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Taking longer to recover
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Frequent illness
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Increased injuries
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Poor sleep
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Mood changes
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Feeling unable to relax away from training
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Changes to menstrual cycle
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Reduced motivation or enjoyment of sport
These signs do not automatically mean REDs, but they are signals worth listening to.
Supporting Your HPA Axis as an Athlete
The best support for your stress system comes from the basics.
Fuel Your Training
Adequate energy intake helps signal to your body that resources are available.
Prioritise:
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Enough total calories
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Carbohydrates around training
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Regular meals and snacks
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Recovery nutrition after exercise
Manage Training Load
More training is not always better.
Your body needs:
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Hard sessions
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Easy sessions
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Rest days
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Periods of lower training load
Progress comes from balancing stress and recovery.
Prioritise Sleep
Sleep supports:
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Hormone regulation
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Recovery
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Immune function
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Nervous system balance
Maintain Life Balance
Sport is important, but it should add to your life—not remove everything else.
Time with friends, education, work, hobbies and relaxation are all part of a healthy athlete lifestyle.
The Athlete Takeaway
Your adrenal glands and HPA axis help your body respond to stress—but they need recovery and fuel to function properly.
The goal is not to eliminate stress. Training requires stress.
The goal is to create the right balance:
Train hard. Fuel enough. Recover properly. Adapt.
Because the strongest athletes are not the ones who push the hardest every day—they are the ones who know when to recover.
