Hamstring Strains: Causes, Symptoms & Evidence-Based Treatment

Expert Physio Insights from Sports Performance Physiotherapy

Hamstring strain injuries (HSI) are one of the most common muscle injuries seen in athletes and active individuals, especially in sports involving sprinting, rapid acceleration and high-speed running.

Despite advances in rehabilitation, recurrence rates remain high, and many athletes struggle to return safely without re-injury.

At Sports Performance Physiotherapy in Drummoyne, we combine current research with structured, criteria-based rehabilitation to optimise recovery and performance.

What Is a Hamstring Strain?

The hamstrings are a group of three muscles located at the back of the thigh:

• Biceps femoris

• Semitendinosus

• Semimembranosus

They are responsible for:

• Hip extension

• Knee flexion

• High-speed running function

A hamstring strain occurs when one of these muscles is overloaded — often during sprinting or lengthening movements — resulting in damage to:

• Muscle fibres

• Musculotendinous junction

• Intramuscular or free tendon

Injury Severity

Hamstring strains range from:

• Mild muscle strain

• Moderate tear

• More severe injuries involving the intramuscular tendon

Intramuscular tendon injuries often have longer recovery timelines and higher recurrence risk.

Why Do Hamstring Strains Occur?

Multiple Contributing Factors

Hamstring injuries are multifactorial, with both modifiable and non-modifiable risk factors including:

• Previous injury history

• Age

• Neuromuscular deficits

• Strength imbalances

• Running mechanics

• Training load and sprint exposure

High-Speed Running

Most non-contact hamstring injuries occur during the late swing phase of sprinting — when the hamstrings are lengthening under load (eccentric contraction).

Both insufficient and excessive exposure to high-speed running can increase injury risk.

Strength & Muscle Architecture

Stronger hamstrings and longer muscle fascicle length are associated with lower injury risk.

These adaptations are achieved through:

• Eccentric strengthening

• Progressive loading in training and rehabilitation

Recurrence Risk

Hamstring strains have a high recurrence rate, particularly within the first year after return to sport.

Higher-grade injuries carry an increased risk of reinjury, especially if rehabilitation is incomplete.

Diagnosis & Imaging

Diagnosis involves:

• Clinical history

• Physical examination (strength, length, activation)

• Assessment of the kinetic chain

Imaging (MRI or ultrasound) may be used to:

• Identify injury location

• Assess intramuscular tendon involvement

• Guide return-to-play timelines

At Sports Performance Physiotherapy in Drummoyne, imaging is used when clinically relevant — particularly in higher-grade or elite athlete cases.

Evidence-Based Rehabilitation: What Works

Successful rehabilitation should be:

• Progressive

• Criteria-based

• Individualised

—not time-based alone.

1. Eccentric Strengthening

Eccentric training is one of the most supported interventions.

Benefits include:

• Increased muscle fascicle length

• Improved strength at long muscle lengths

• Reduced injury risk

Examples include:

• Nordic hamstring exercise

• Hip extension-based exercises

2. Progressive & Functional Loading

Rehabilitation progresses through increasing:

• Load

• Exercise complexity

• Movement intensity

Exercise selection is important, as different exercises target different hamstring muscles.

For example:

• Knee-dominant exercises bias medial hamstrings

• Hip-dominant exercises target other regions

Progression eventually includes:

• Running

• Sprinting

• Sport-specific movements

For structured progression back to running, see our Return to Run Programs in Drummoyne.

3. Intramuscular Tendon Considerations

Higher-grade injuries involving the intramuscular tendon require modified rehabilitation.

Key considerations include:

• Early emphasis on isometric exercises

• Delayed introduction of eccentric loading

• Delayed return to running

• Careful load progression

These injuries require a more conservative approach to reduce recurrence risk.

Return to Sport: Criteria Over Timeframes

Return to sport should be based on objective criteria, including:

✔ Pain-free strength across multiple ranges

✔ Equal strength and rate of force development

✔ Eccentric hamstring strength (e.g. Nordic peak force)

✔ Sport-specific speed and power benchmarks

✔ Movement quality and biomechanics

✔ Imaging confirmation in higher-grade injuries

Athletes returning without meeting criteria have a significantly higher risk of reinjury.

Prevention Strategies

Preventing hamstring strains involves:

• Consistent eccentric strengthening

• Gradual exposure to sprinting and high-speed running

• Addressing kinetic chain imbalances

• Monitoring training load

Regular hamstring strengthening programs have been shown to significantly reduce injury incidence.

Summary: Key Points for Athletes & Clinicians

✔ Hamstring strains are common and highly recurrent

✔ Risk factors include previous injury, strength deficits and load errors

✔ Eccentric strengthening is a key component of rehab

✔ Return to sport should be criteria-based, not time-based

✔ Intramuscular tendon injuries require modified rehabilitation

At Sports Performance Physiotherapy in Drummoyne, we use structured, evidence-based rehabilitation to help athletes recover safely and return to peak performance.

If you are dealing with a hamstring injury, early assessment is key.

👉 Book here:https://www.sportsperformancephysio.com/contact