Blog 3: Muscle Contractions
Part 3:Concentric Contractions: The Power Phase (And Why It Is Only Half the Story)
Welcome back to Understanding Muscle Contractions. In Part 1 we laid the foundation for all three contraction types. In Part 2 we covered isometric contractions, the stability work that holds everything together. Now we move to the one most athletes know best: concentric contractions.
If isometric is the quiet one and eccentric is the intense one, concentric is the life of the party. It is the phase that feels powerful, that looks impressive, and that most training programmes are built almost entirely around. There are good reasons for that — and some important limitations.
What a Concentric Contraction Is
A concentric contraction occurs when a muscle generates force and shortens in the process. The force the muscle produces exceeds the external load, so the muscle wins the tug of war and gets shorter as it contracts. The joint moves in the direction the muscle is pulling.
This is the lifting phase of any movement. The bicep shortening to curl a weight up. The glutes and quads shortening to drive you out of a squat. The calf shortening to push off the ground in a running stride. The chest muscles shortening to push a barbell away. Every time you produce movement against a resistance, concentric contractions are doing the work.
The word comes from the Latin con, meaning together, and centrum, meaning centre — the muscle fibres are pulling toward their centre as they shorten.
What Concentric Training Develops
Concentric training is the primary driver of several important adaptations:
Muscular Strength and Hypertrophy:
The shortening phase stimulates muscle protein synthesis and is the principal mechanism behind muscle growth in most training programmes
Rate of Force Development:
Training the concentric phase at speed develops the ability to generate force quickly, which is directly relevant to sprinting, jumping, throwing, and striking
Neural Efficiency:
The nervous system becomes better at recruiting motor units quickly and synchronously, which is why strength increases in the early weeks of a new training programme before significant muscle growth has occurred
Power Output:
Explosive concentric training (plyometrics, Olympic lifting, sprint work) develops the ability to produce large amounts of force in short timeframes
These adaptations are genuinely important. A strong concentric phase means better propulsion in running, more power on the bike, a stronger swim pull, and better acceleration in court sports. This is why concentric training is the backbone of most strength and conditioning programmes.
Where Concentric Strength Shows Up in Sport
Running: The propulsive phase from toe-off is driven by concentric calf, glute, and hip flexor contractions. Weak concentric glutes reduce stride length and increase the demand on the calf and Achilles
Cycling: The power phase of the pedal stroke, from roughly 12 o'clock to 5 o'clock, is primarily concentric quad and glute work. This is where watts are generated and where quad dominance patterns develop if glute strength lags
Swimming: The catch-to-finish pull phase is driven by concentric latissimus dorsi, pec major, and tricep contractions. This is the engine of forward propulsion in the water
Hockey and Skating: The push phase of each skating stride is a powerful concentric hip abductor and glute contraction. Developing this is central to skating speed
Any jumping, throwing, or striking sport, the power generation phase is entirely concentric and is where sport-specific strength training has the most direct transfer
The Limitation Most Athletes Miss
Here is where it gets important. Concentric training is valuable, but it is also the easiest of the three contraction types on the tissue. The muscle shortens under load, which is mechanically the least demanding scenario for the muscle and tendon. Recovery from pure concentric training is faster, and the injury risk during the contraction itself is lower.
The problem is that most sports are not predominantly concentric. Running, landing, decelerating, changing direction, absorbing impact — these are all eccentric-dominant movements. Athletes who train predominantly concentric patterns in the gym are building power without the matching capacity to control that power under real sport demands. This is a setup for injury.
Research comparing concentric-only training to programmes that include eccentric and isometric work consistently finds that mixed programmes produce better injury resilience, better functional strength transfer to sport, and better long-term performance outcomes. Concentric training alone builds the engine. You also need the brakes.
Practical Takeaways
Do not abandon concentric training, it is producing real, important adaptations that matter for your sport
Recognize that the concentric phase of most gym exercises is only half the movement — the return phase (lowering the weight, the descent of a squat) is equally important and deserves equal attention
Explosive concentric training (jumps, throws, sprint starts) builds qualities that slower tempo work cannot replicate — include it if your sport demands it
Balance your programme: for every heavy concentric session, include work that specifically trains the eccentric and isometric demands your sport places on the same muscles
Up Next: Eccentric Contractions
Part 4 is where things get really interesting. Eccentric contractions are the most powerful, the most tissue-damaging, the most adaptation-producing, and the most injury-relevant of the three types. They are also the most undertrained in recreational athletes and the most misunderstood. See you there.
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Want to know if your training programme is actually balanced across all three contraction types? I work with athletes to build training approaches that develop the full picture. Reach out to book an assessment at with Dr. Keirstyn today at Endurance Therapeutics.
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