Athletes train hard.

But performance doesn’t just come from training—it comes from how well your body is fueled to support that training.

Relative Energy Deficiency in Sport (RED-S) occurs when an athlete isn’t taking in enough energy to meet the demands of their sport. This can affect everything from performance to injury risk to long-term health.

At Breathe in Motion, we work with female athletes in Brookfield and Mequon to identify early signs of under-fueling and support their bodies so they can train, perform, and recover effectively.

What Is RED-S?

RED-S happens when energy intake doesn’t match energy output.

This can be:

  • Intentional (diet restriction, weight goals)
  • Unintentional (training increases but fueling doesn’t)

Over time, the body doesn’t have enough energy to support normal function.

Why RED-S Matters for Athletes

When the body is under-fueled, it starts to prioritize basic survival over performance.

This affects multiple systems—and often shows up first in subtle ways before becoming more serious.

How RED-S Impacts the Body

Low energy availability can lead to:

For athletes, this often means the body can’t keep up with training demands.

How RED-S Affects Performance

Athletes experiencing RED-S may notice:

  • Decreased endurance
  • Reduced strength and power
  • Poor coordination
  • Slower reaction time
  • Difficulty concentrating
  • Increased fatigue

Performance often declines before athletes realize what’s happening.

Who Is at Risk?

RED-S is more commonly discussed in female athletes, but it can affect anyone.

Higher-risk groups include:

It’s especially common when:

  • training volume increases
  • recovery doesn’t match
  • fueling isn’t adjusted

Early Warning Signs to Watch For

Red Flags

  • Diagnosed eating disorders
  • Extreme or rapid weight loss
  • Significant physical or psychological effects

Requires medical management and restricted training

Yellow Flags

  • Irregular or missed periods
  • Low energy levels or fatigue
  • Frequent injuries or slow recovery
  • Noticeable weight or body composition changes
  • Inconsistent fueling habits

Requires monitoring and structured support

Green Flags

  • Consistent energy and recovery
  • Regular menstrual cycles
  • Stable performance
  • Strong bone and tissue health

Indicates appropriate fueling and recovery

Why Early Intervention Matters

RED-S doesn’t always show up dramatically at first.

Often it looks like:

  • “Just feeling tired”
  • Small injuries that won’t go away
  • Performance plateaus

Addressing it early helps:

  • Reduce injury risk
  • Improve recovery
  • Support long-term performance

How to Reduce Risk of RED-S

1. Fuel for Your Training

Your nutrition should match:

  • Training volume
  • Intensity
  • Recovery needs

Under-fueling limits adaptation.

2. Shift Focus From Weight to Performance

Performance improves when the body is:

  • Fueled
  • Strong
  • Supported

Not when it’s restricted.

3. Monitor Changes in Your Body

Pay attention to:

  • Energy levels
  • Menstrual changes
  • Recovery time
  • Injury patterns

4. Build a Support Team

Working with:

  • Physical therapists
  • Physicians
  • Nutrition professionals

Helps catch issues early and guide recovery.

How Physical Therapy Fits In

At Breathe in Motion, we often see RED-S show up as:

We help identify patterns, modify training, and guide athletes toward better load management and recovery strategies.

The Goal: Fuel Performance, Protect Your Body

Your body needs energy to:

  • Train
  • Recover
  • Perform

When those needs are met, performance improves—and injury risk decreases.

Sports Physical Therapy in Brookfield & Mequon

If you’re dealing with recurring injuries, fatigue, or performance changes, this is something we look at during a full evaluation.

Serving athletes in Brookfield, Mequon, and the greater Milwaukee area.

Book your physical therapy evaluation at Breathe in Motion and get a plan built to support your training, recovery, and long-term performance.