Blog 2: Muscle Contractions
Part 2: Isometric Contractions: The Most Underrated Tool in Athletic Training
Welcome back to Understanding Muscle Contractions. In Part 1 Dr. Keirstyn introduced the three types of muscle contractions and explained why the differences between them matter more than most athletes appreciate. Now we go deep on the first one: isometric contractions.
If you have ever held a plank, pressed your palms together, or squeezed a wall that was not going anywhere, you have performed an isometric contraction. The muscle is working hard. The joint is not moving. And the training effect is far more powerful than most people give it credit for.
What an Isometric Contraction Actually Is
An isometric contraction occurs when a muscle generates tension without changing its length. The force the muscle produces is equal to the external load it is resisting, so nothing moves. From the outside, it looks like nothing is happening. Inside the tissue, quite a lot is happening.
The word isometric comes from the Greek for equal measure — iso meaning equal and metric meaning length. The length of the muscle stays the same throughout the contraction. What changes is the tension within it.
Common Isometric Contractions in Daily Life and Sport:
Holding a plank: your core is generating constant tension to prevent your spine from collapsing, without any spinal movement occurring
Gripping a handlebar or a racquet: the forearm muscles are contracting isometrically to maintain grip under load
Single-leg stance during the gait cycle: every time your foot is on the ground during running or walking, your hip stabilizers are contracting isometrically to prevent your pelvis from dropping
Maintaining a cycling position: the lower back, hip flexors, and core are all working isometrically to hold your posture on the bike across hours of riding
Wall sits, dead hangs, and holds of any kind in the gym
Why Isometric Training Is Undervalued
Isometric training does not look impressive. There is no movement to film for social media, no satisfying completion of a rep, and no obvious progression to show off. This is probably why it gets so little attention relative to its actual value.
The research tells a very different story. A 2015 review in the British Journal of Sports Medicine found that isometric exercise was one of the most effective interventions for reducing tendon pain in athletes, with immediate analgesic effects that could last for up to 45 minutes post-exercise. For athletes dealing with patellar tendinopathy, Achilles tendinopathy, and rotator cuff issues, isometric loading is frequently the first type of contraction introduced in rehabilitation precisely because it loads the tendon without the mechanical complexity of movement.
Beyond rehabilitation, isometric training develops what exercise scientists call positional strength: the ability to maintain a specific joint position under load. This is exactly what the body needs to hold technique together under fatigue, to stabilize during high-velocity movements, and to protect joints when external forces try to push them out of position.
Where Isometric Strength Shows Up in Sport
Once you understand isometric contractions, you start seeing them everywhere:
Running:
At midstance, the entire lower limb is absorbing ground reaction forces isometrically before the propulsive phase begins. Weak isometric hip stabilizers here are one of the most direct causes of IT band syndrome and patellofemoral pain
Swimming:
The catch position in freestyle requires significant isometric shoulder and scapular stability. Without it, the force generated by the pull phase leaks and the rotator cuff compensates under load
Cycling:
The sustained isometric demand on the lower back and hip flexors across a long ride is one of the primary drivers of cycling-related lower back pain. Improving isometric endurance in these structures is a key intervention
Hockey:
The skating stride involves a brief isometric glute and hip stabilizer hold at the peak of hip abduction before each push. Weakness here feeds directly into groin and adductor injuries
Any sport involving bracing, tackling, contact, or landing: the body's ability to hold position under sudden external force is entirely isometric
How to Train Isometric Strength
Isometric training is versatile and accessible. A few principles:
Position specificity matters: isometric strength is most developed at the angle you train it. If you want isometric hip stability at 20 degrees of hip flexion (midstance running position), you need to train at that angle
Duration over intensity for endurance sports: longer holds at moderate intensity build the postural endurance most relevant to running, cycling, and swimming
High intensity for power and tendon loading: brief maximal isometric holds generate significant tendon force and are used in advanced rehabilitation and strength development
Isometrics are ideal during injury: because they load tissue without creating joint movement, they can often be performed through injury when concentric and eccentric work is too painful or risky
Practical examples: plank variations for core and shoulder stability, wall sit for quad and knee tendon loading, Copenhagen holds for adductor strength, single-leg stance progressions for hip stability, and isometric wrist holds for forearm tendon rehabilitation.
Up Next: Concentric Contractions
We have established the stable foundation. Part 3 of Understanding Muscle Contractions moves into concentric contractions — the power-production phase that most athletes are most familiar with and most focused on. We will look at what it actually trains, where the common misunderstandings are, and how it fits into a complete training picture. See you there.
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Isometric strength deficits are one of the most common findings in athletes with recurring injuries. If you want to know where yours are, a movement assessment at Endurance Therapeutics gives you that picture. Reach out to book yours.
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