Relative Energy Deficit in Sport (RED-S)
Physiotherapy support for RED-S screening and recovery.
RED-S physiotherapy care can support athletes when low energy availability starts affecting recovery, injury risk, mood, hormones, and sport output.
RED-S stands for Relative Energy Deficiency in Sport. It can happen when an athlete does not take in enough energy to cover training, sport, recovery, and normal body needs. Over time, the body starts to save fuel. Recovery slows. Injury risk can rise.
Many athletes think long-term fatigue is just hard training. However, repeat injuries, poor recovery, missed periods, low sex drive, or a sudden drop in sport output may point to low energy availability. Early screening helps athletes protect health while they rebuild a safer plan.
For broader athlete care, see sports physiotherapy Brisbane and our sports health hub. Useful related pages include injury prevention programs, biomechanical assessment, acute sports injury management, and sports massage for athletes.
For clinician-led screening, the IOC provides the RED-S Clinical Assessment Tool version 2.
Quick Guide: When Should Athletes Think About RED-S?
- Fatigue lasts longer than expected.
- Performance drops despite training effort.
- Injuries keep returning.
- Periods change, stop, or become irregular.
- Recovery, mood, sleep, or sex drive changes.
What Is RED-S?
RED-S occurs when the body does not have enough available energy after training and daily activity. The issue is not only “not eating enough”. It is the gap between energy coming in and energy going out.
That gap can happen during heavy training blocks, weight-focused sport, poor meal timing, appetite loss, stress, illness, travel, or disordered eating. RED-S can affect athletes of any gender, age, or sport level.
Common RED-S Signs and Symptoms
RED-S can look different in each athlete. Still, some patterns show up often. Female athletes may notice late, missed, or changed periods. Male athletes may notice low sex drive, fewer morning erections, or heavy fatigue. Any athlete with repeat bone stress injuries needs careful review.
- Persistent fatigue: tiredness that does not match the training load.
- Slower recovery: heavy legs, soreness, or poor bounce-back.
- Performance drop: reduced pace, strength, power, or training quality.
- Repeat injuries: tendon pain, muscle strains, or bone stress injuries.
- Illness: frequent colds, infections, or feeling run down.
- Hormone changes: altered periods, low libido, or fewer morning erections.
- Mood changes: irritability, anxiety, low mood, or food stress.
- Cold sensitivity: feeling cold often, even in normal conditions.
What Happens Inside the Body?
When energy availability stays low, the body protects vital tasks first. It may lower sex hormones, slow bone repair, and change how it uses energy. This can affect strength, power, focus, and training tolerance.
| Body system | Possible effect | Why it matters |
|---|---|---|
| Bone | Slower bone repair | Higher risk of stress reaction or stress fracture |
| Hormones | Period or testosterone-related changes | Reduced recovery, drive, and adaptation |
| Immune system | More illness or slow recovery | More missed training and poor consistency |
| Muscle and tendon | Poor load tolerance | More risk of tendon pain or repeat muscle strain |
Can RED-S Cause Injuries?
Yes, RED-S may raise injury risk. When the body lacks fuel for repair, bone and soft tissue recovery can slow. Athletes may notice tendon pain, repeat strains, or bone stress injuries. If “bad luck injuries” keep happening, RED-S screening can help guide the next step.
How Can Physiotherapy Help With RED-S?
RED-S care usually needs a team. A physiotherapist can check injury patterns, training load, strength, and return-to-sport steps. A sports dietitian can guide food timing and training-day fuel. A GP or sports doctor may arrange medical checks when red flags appear.
A physiotherapist may help by:
- screening injury history, fatigue, load, sleep, and recovery quality
- checking strength, power, balance, and movement control
- modifying training load while symptoms settle
- guiding a graded return to running, jumping, gym, or sport
- coordinating care with a GP, sports doctor, psychologist, or dietitian when needed
Can I Keep Training?
This depends on the athlete, symptoms, and injury risk. RED-S does not always mean full rest, but it does mean the plan needs review.
- Lower concern: mild fatigue with no injury, normal periods, and stable health markers.
- Moderate concern: repeat soreness, illness, poor sleep, or clear performance drop.
- Higher concern: bone stress pain, fainting, rapid weight loss, missed periods, or disordered eating signs.
Training and Fuelling Principles
Do not try to fix RED-S by training harder. First, reduce the gap between fuel and training demand. This may mean changing meal timing, rest days, session load, or race plans while the body settles.
Useful First Steps
- Fuel before, during, and after key training sessions where needed.
- Avoid long fasted sessions if fatigue or injury risk is rising.
- Plan easier weeks after heavy training or competition blocks.
- Track sleep, mood, soreness, illness, and training quality.
- Seek dietitian input if food stress, restriction, or poor intake is present.
When Should an Athlete Seek Medical Review?
Seek medical review if there are signs of bone stress injury, fainting, chest symptoms, rapid weight loss, ongoing missed periods, disordered eating, or marked mood change. RED-S can affect health beyond sport, so early support matters.
Related PhysioWorks Guides
- Sports health for athletes
- Sports physiotherapy Brisbane
- Acute sports injury management
- Injury prevention programs
- Biomechanical assessment
- Sports massage for athletes
Frequently Asked Questions
What is RED-S?
RED-S is Relative Energy Deficiency in Sport. It means the body does not have enough available energy to support both sport and normal body function. It can affect recovery, bone health, hormones, mood, immunity, and performance.
What are common signs of RED-S?
Common signs include ongoing fatigue, poor recovery, repeat injuries, frequent illness, mood change, and sport decline. Female athletes may notice period changes. Male athletes may notice low sex drive, fewer morning erections, or heavy fatigue.
Can RED-S increase stress fracture risk?
Yes. Low energy availability may reduce bone repair and alter hormones that support bone health. This may increase the risk of bone stress injury, especially during heavy training blocks or rapid load increases.
How is RED-S managed?
RED-S is usually managed with a team approach. A physiotherapist can help with injury care and training load. A sports dietitian can guide fuelling. A GP or sports doctor may help with medical checks when needed.
Should athletes keep training with RED-S symptoms?
Some athletes can keep training with changes, while others need rest or medical review. The safest plan depends on injury risk, symptoms, health markers, and sport demands. A clinician can help guide this decision.
Who should I see if I suspect RED-S?
A physiotherapist can help screen injuries, load, recovery, and return-to-sport needs. A sports dietitian can review fuelling. A GP or sports doctor may help with blood tests, bone health, hormone concerns, or wider health checks.
What to Do Next
If fatigue, repeat injuries, period changes, or sport decline are showing up, start with a plan rather than guessing. Track training load, sleep, soreness, mood, and food timing for 7 to 14 days.
Then book an assessment so your clinician can screen for RED-S patterns, treat injuries, and map out practical next steps.
Book your appointment – 24/7
Choose your preferred PhysioWorks clinic and book online.
Follow PhysioWorks
Get free physiotherapy tips, exercise videos, recovery advice, and blog updates.
 |  |  | B |  |  |
References
- Mountjoy M, Sundgot-Borgen J, Burke L, et al. 2023 International Olympic Committee (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023;57(17):1073-1097. doi:10.1136/bjsports-2023-106994
- Stellingwerff T, Heikura IA, Meeusen R, et al. Review of the scientific rationale, development and validation of the International Olympic Committee Relative Energy Deficiency in Sport Clinical Assessment Tool V.2. Br J Sports Med. 2023;57(17):1109-1118. doi:10.1136/bjsports-2023-106914
- Heikura IA, McCluskey WTP, Stellingwerff T, et al. Application of the IOC Relative Energy Deficiency in Sport Clinical Assessment Tool version 2 across 200+ elite athletes. Br J Sports Med. 2025;59(1):24-31. doi:10.1136/bjsports-2024-108121
