Isometric training involves creating muscle tension without actual movement at the joint, for example holding a squat, wall sit or split squat position. While it’s often used in the early stages of rehab, this research shows that how and where you hold the contraction makes a big difference to your results.
This systematic review analysed 26 studies looking at how different isometric training variables affect muscle size, tendon health, strength and performance.
Training at Longer Muscle Lengths = Bigger Strength Gains
One of the clearest findings was that doing isometric holds when the muscle is in a more stretched position (long muscle length) produces better results than when it is in a shortened position.
Training at longer muscle lengths led to:
● Greater increases in muscle size (hypertrophy)
● Better improvements in strength across more joint angles
● Greater improvements in tendon stiffness and resilience
● Better transfer to real-life movement and sport
This helps explain why a deeper squat hold or deeper calf stretch hold is often more effective than a shallow
position.
High Intensity Is Key for Tendon Health
If the goal is to improve tendon strength (for example Achilles or patellar tendon), the research showed that:
● Higher intensities (around 70–100% effort) are needed to significantly increase tendon stiffness and
function
● Lower intensities may not be enough to create meaningful tendon changes
● Improvements in tendon stiffness can help with pain reduction, force transfer and injury prevention
This is particularly important in managing tendinopathies, where the tendon needs strong, controlled loading to recover.
Intent Matters: Fast vs Slow Effort
The study also found that your intention during the hold influences the adaptation:
● Explosive intent (driving into the position quickly) improved early muscle activation and rate of force
development
● Sustained intent (building and holding maximum tension) produced greater increases in muscle size and
maximum strength
This means we can tailor isometric training depending on whether the goal is power, speed, or strength.
What This Means for Your Training & Rehab
Isometric exercises are much more than a “basic” option. When applied correctly, they can:
● Build muscle
● Strengthen tendons
● Reduce joint pain
● Improve control and stability
● Prepare the body for dynamic movement
Takeaway
It’s not just about holding a position, how hard you hold, where you hold it, and how you engage the muscle determines your results. Isometrics are a powerful and underused tool for rehab, performance, and injury prevention when prescribed correctly.
Newsletter By: Emre Oz (Musculoskeletal Physiotherapist at Crouch Physio).
