High-Intensity Interval Training (HIIT) and Stress Fractures: Insights from a Medical Research

High-intensity interval training (HIIT) has become a widely adopted exercise approach due to its time efficiency and cardiovascular benefits. However, recent medical literature has highlighted that repetitive high-impact training may also contribute to overuse injuries, including bone stress injuries such as stress fractures.
 

A medical research case report published in the World Journal of Clinical Cases describes an unusual presentation of both medial tibial stress syndrome (MTSS) and an incomplete femoral neck stress fracture in a physically active young adult female following several months of HIIT participation. The findings provide clinically relevant insights for individuals who experience persistent shin or hip pain during high-intensity exercise routines.
 

This research involved contributions from healthcare professionals including Dr Alan Cheung of the International Orthopaedic Clinic in Singapore, among others.

Understanding Stress Fractures and Bone Stress Injuries

A stress fracture is a small crack or severe bruising within a bone that develops over time due to repeated loading rather than a single traumatic event. Stress fractures are most commonly associated with running, jumping sports, military training, and other activities involving repetitive impact.
 

Bone stress injuries exist on a spectrum, ranging from early inflammation of bone tissue to more severe stress fractures. When repetitive loading continues without sufficient recovery, microdamage can accumulate faster than the body’s ability to repair it.

The Research Case: Stress Injuries Following HIIT Training

The published case report described a 26-year-old female who had participated in HIIT workouts for approximately 45 minutes per session, five times a week, over a period of seven months.
 

She initially experienced bilateral shin pain, which progressively worsened. MRI imaging supported a diagnosis of medial tibial stress syndrome, a condition commonly referred to as “shin splints.”
 

Subsequently, the patient developed severe pain in the right hip region. Further evaluation using MRI identified an incomplete femoral neck stress fracture, a potentially serious injury due to its location near the hip joint.
 

The researchers highlighted that this sequential development of MTSS followed by femoral neck stress fracture after HIIT training is not commonly reported in existing literature, making the case clinically notable.

What Is Medial Tibial Stress Syndrome (MTSS)?

Medial tibial stress syndrome is a frequent cause of exercise-related shin pain. It is associated with repetitive traction forces along the tibia, commonly affecting runners and individuals performing repetitive jumping or high-impact activities.
 

Typical symptoms include:

• Pain along the inner border of the shin bone
• Discomfort that worsens with activity
• Tenderness along the tibia
• Pain that may improve temporarily with rest but returns when activity resumes
   

MTSS is considered a stress-related injury and may occur alongside more serious bone injuries if physical activity continues without appropriate modification.

Femoral Neck Stress Fracture: Why It Matters

A femoral neck stress fracture involves the upper portion of the thigh bone near the hip joint. While stress fractures may occur in various locations, femoral neck fractures are clinically significant due to the risk of progression into a complete fracture.
 

Symptoms may include:

• Groin pain or deep hip pain
• Pain triggered by weight-bearing or walking
• Reduced tolerance for exercise
• Pain that may persist even at rest in more severe cases
   

The research report emphasised that early diagnosis is important because missed femoral neck stress fractures can lead to worsening injury and prolonged recovery.

The Role of MRI in Stress Fracture Diagnosis

The research highlighted the importance of imaging in diagnosing bone stress injuries. Early-stage stress fractures may not always appear clearly on standard X-rays.
 

In this case, MRI was used to confirm both diagnoses:

• MRI findings supported medial tibial stress syndrome through evidence of periosteal and marrow oedema.
• MRI also detected an incomplete femoral neck stress fracture that may not have been obvious through initial clinical assessment alone.
   

MRI remains one of the most sensitive imaging methods for identifying stress-related bone injuries, particularly in early stages.

HIIT and Injury Risk: What the Research Suggests

HIIT workouts often combine rapid bursts of high-intensity activity with short recovery periods. While the format may be effective for fitness development, certain HIIT programmes involve repetitive jumping, sprinting, lunging, or loaded lower limb movements.
 

The researchers noted that high-impact HIIT training, particularly when performed frequently, may expose participants to increased repetitive load. Over time, this may contribute to stress injuries, especially if recovery periods are insufficient.
 

Although this is a single case report, the findings raise clinical considerations for individuals who experience persistent pain while participating in HIIT training.

When to Consider Orthopaedic Screening

The case described in the research reinforces the importance of not dismissing prolonged shin or hip pain during exercise. Pain that persists despite rest may indicate an underlying stress injury rather than simple muscle soreness.
 

Orthopaedic screening may be considered when symptoms include:

• Shin pain lasting more than several weeks
• Pain that worsens progressively with exercise
• Pain that begins to affect walking or daily activity
• Hip or groin pain that appears without trauma
• Pain that does not improve despite reduced training volume
   

Early evaluation by an orthopaedic specialist may allow identification of stress injuries before they progress into more severe fractures.

Treatment Approach Highlighted in the Research

The patient in the case report was treated conservatively with:

• Rest and activity modification
• Physiotherapy support
• Pain relief medication as needed
   

Her symptoms eventually resolved following appropriate rehabilitation and reduction of impact activity.
 

The report suggests that conservative management may be effective for selected patients, particularly when stress fractures are incomplete and identified early.

Key Takeaways

This case report adds to clinical awareness of bone stress injuries associated with high-intensity training programmes. While HIIT remains a widely practised exercise method, the research indicates that repetitive impact without adequate recovery may contribute to injuries such as MTSS and femoral neck stress fractures.
 

Individuals who experience ongoing shin or hip pain during HIIT should consider early evaluation, especially when symptoms persist or worsen. Imaging, particularly MRI, may be required to confirm stress injuries that are not visible on standard X-rays.

References

• Tan DS, Cheung FM, Ng D, Cheung TLA. Femoral neck stress fracture and medial tibial stress syndrome following high intensity interval training: A case report and review of literature. World Journal of Clinical Cases. 2022 Aug 16;10(23):8323–8329. doi:10.12998/wjcc.v10.i23.8323. PMCID: PMC9403697. PMID: 36159550.