What is it all about? How do we use it? Why do we love it?
Everyone likes a new toy to play around with in the gym, especially ones which have real benefit and novel in their approach. Eccentric flywheel training is one of them! Used extensively in rehab populations and sports performance, the flywheel is all about giving some love to the eccentric contraction.
Before stating why an eccentric contraction is important, first we have to know what it is...
An eccentric contraction happens “when a force applied to the muscle exceeds the momentary force produced by the muscle itself, resulting in the forced lengthening of the muscle-tendon system while contracting" (Lindstedt et al., 2001). More simply put, a lengthening muscle contraction. I know what you’re thinking, it’s difficult to get your head round, as typically a contraction is synonymous with shortening. But if that were the case, how would we resist motion when a force is applied to us? How would you stop yourself suddenly from falling? How do you resist a weight applied to a limb? How do you control yourself in a negative phase of a squat and not just crumble? Hence why eccentric training is often called “negative work”.
“Skeletal muscles contract eccentrically to support the weight of the body against gravity and to absorb shock or to store elastic recoil energy in preparation for concentric contractions” (Lindstedt et al., 2001).
Eccentric contractions are just one part of the contraction cycle and one that often we neglect or fail to truly overload in the gym. However, they are perhaps the most important when it comes to strength, power and reducing risk of injury.
You could argue in sports which require high rates of force development (the ability to produce force quickly, where time isn't a luxury) that you're only as strong as your eccentric contraction. That is, the greater the ability for an individual to decelerate under high velocities and high force, the better they will be in the carryover to the concentric phase of a movement. Stopping and changing direction is a great example of this. The faster and harder you can decelerate and load the "elastic components" of the muscle & tendon the more force you can produce in the concentric action or push phase of the motion. Even something as simple as running this happens on ground contact for every stride, what stops you spending too long on floor (and therefore being slower) is your ability to decelerate and transfer that energy into an effective push off.
Producing force quickly to one side, there is some good evidence eccentric strength training is superior for muscular hypertrophy (muscle growth), maximal strength, and as mentioned above, power. Methods like slow tempo negatives, increasing time under tension and supra-maximal negatives are powerful tools to develop the eccentric contraction. But sometimes they are difficult to execute, in the former to create sufficient overload (as you are up to 1.5x stronger in an eccentric contraction) and in the later to do it safely and with repetition when gravity is present! This is where the flywheel comes into it's own......
So what is a flywheel?
When applying force in the concentric phase (the up phase of a squat for example) the flywheel at the front of the box starts to spin, as you reach the top of the squat the flywheel returns the energy you’ve created by pulling you back down using the straps that are attached to a harness. This means you must decelerate and resist this pull creating overload on the eccentric contraction. The more force you put into the concentric phase, the faster the wheel spins and more force is returned on the way down. You can create even more overload by using hand supported variations to increase the eccentric demand on the way down, as using the arms helps exceed force produced by the legs. You can also play around with the speed of the descent and at what point you resist the flywheel creating overload at different joint angles.
It also means, unlike typical barbell work for example, there is no rest and you are constantly contracting. Flywheel training is about inertia not gravity.
So all in all, a pretty cool bit of kit to have around and we look forward to getting the most out of it!
References;
Eccentric Muscle Contractions: Risks and Benefits (2019).
When active muscles lengthen: properties and consequences of eccentric contractions (2001)
Effects of Flywheel Training on Strength-Related Variables: a Meta-analysis (2018).
https://simplifaster.com/articles/high-speed-eccentric-resistance-training/
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