The Injury Pattern That Has Nothing to Do With How Hard You Train

Some of the most dedicated athletes we see are also some of the most frequently injured. Stress fractures that don’t fully heal. Hormonal disruption. Fatigue that doesn’t respond to rest. A training history that looks disciplined on paper but keeps producing setbacks.

Often, the missing piece isn’t biomechanical. It’s a condition called Relative Energy Deficiency in Sport (RED-S), and it’s one of the most underdiagnosed problems in active people today.

What Is RED-S?

RED-S describes what happens when the body isn’t taking in enough energy to support both the demands of training and the demands of normal physiological function. The body, faced with a deficit, starts making trade-offs. It down-regulates processes it considers non-essential, like bone remodeling, hormonal regulation, immune function, and tissue repair.

The result is a cluster of health consequences that can look, to the untrained eye, like a series of unrelated bad luck: a stress fracture here, a slow recovery there, persistent fatigue, recurring soft tissue injuries.

RED-S was previously described as the “Female Athlete Triad” – a framework that linked low energy availability, menstrual dysfunction, and low bone density specifically in female athletes. That model has since been expanded. RED-S affects athletes of all genders, all sports, and all levels, from elite competitors to recreational runners logging 25 miles a week.

The Energy Availability Problem

The key concept in RED-S is energy availability – not just total caloric intake, but how much energy remains for bodily functions after exercise is accounted for. An athlete can be eating what seems like a reasonable amount and still be in a state of low energy availability if their training volume is high.

This means RED-S isn’t always about disordered eating, though it can be. It can also develop gradually and unintentionally – through a heavy training block, a period of stress, a well-meaning attempt to lose a few pounds before a race, or simply not understanding how much fuel a training load actually requires.

The body doesn’t distinguish between intentional restriction and inadvertent underfueling. The physiological response is the same.

What This Looks Like in a PT Context

Physical therapists are often the first clinical contact for athletes with RED-S, not because the patient comes in describing an energy problem, but because they come in with an injury.
Some patterns that should prompt closer questioning:

• Stress fractures, particularly recurrent ones or those occurring in relatively low-impact athletes
• Stress fractures in locations that are less typical, like the femoral neck, sacrum, or metatarsals
• Poor healing timelines (injuries that should resolve within a standard window but don’t)
• A history of multiple seemingly unrelated musculoskeletal problems over a short period
• Reported fatigue, mood changes, or declining performance alongside physical complaints

Bone health is particularly relevant here. Low energy availability suppresses the hormones responsible for bone remodeling. A bone that is chronically under-resourced becomes less able to tolerate load, which means the training itself becomes a liability rather than a stimulus for adaptation.

This Isn’t Something PT Treats Alone

RED-S is a multidisciplinary problem. Managing it properly involves input from a physician, and often a registered dietitian and a sports psychologist as well. A physical therapist’s role is not to diagnose or manage the underlying energy deficiency.

But PT is a critical part of the picture in identifying the pattern, in managing the musculoskeletal consequences, in guiding safe return to activity during recovery, and in being a consistent, trusted presence for an athlete who may not yet understand what’s happening in their body.

If you’re an active person with an injury history that feels disproportionate to your training, or if you’ve been told your bone density is low, or if your body simply doesn’t seem to respond to training the way it should, it’s worth having a conversation that goes beyond the presenting injury.

At Aureum Physio in Cary, NC, we take a whole-athlete view. Sometimes the most important thing we can do in a PT assessment is recognized when the injury in front of us is pointing to something bigger, and make sure you get connected to the right people.

If any of this sounds familiar, we’d encourage you to come in and talk through your full history with us. You don’t have to keep treating injuries one at a time.