What is an Eccentric Flywheel Inertial Trainer?
An eccentric flywheel trainer is a strength and power training device that uses muscle force to rotate a weighted flywheel. A nylon strap connects the exerciser to the central shaft of the flywheel. Spinning the flywheel winds the strap around the shaft. The inertia (spinning resistance) created by the spinning flywheel supplies the resistance felt by the person exercising. Flywheel trainers are typically used to apply an eccentric muscle overload.
Research has shown that eccentric flywheel training may be more effective than traditional strength training for strength, hypertrophy and power development. Other research suggests flywheel training improves muscle function, balance and gait in elderly individuals and stroke patients (Maroto-Izquierdo et al., 2017).
Flywheel trainers come in two main configurations: vertically mounted or platform based. Vertically mounted flywheels can replace cable machines (left above). I find our vertical flywheel is best suited for upper body workouts and lower body accessory exercises. Our platform based flywheel is typically used for lower body main lifts and some compound upper body exercises.
Flywheel Training Guide
Where Did Flywheel Training Come From?
I think that it’s important to understand where training ideas come from to understand their usefulness.
Flywheel inertial training was originally developed to be used by astronauts in space (Wonders, 2019). Scientists in the 90’s needed a gravity-independent way to load muscles to prevent the muscle wasting and strength losses, among other serious effects of space, that were seen in astronauts.
As a result, Swedish scientists developed the flywheel ergometer (Maroto-Izquierdo et al., 2017). It was a brilliant move because it uses the resistance of a spinning disc to provide resistance. Astronauts (and now people around the world) could alter the spinning disc’s size and the speed of exercises to train their muscles without depending on lifting a weight.
Little did they know that flywheel training would be the hottest training trend three decades later.
How Do Eccentric Flywheels Work?
A flywheel is a heavy disc that needs externally applied force to spin it. The size and weight of the disc affects the inertia of the disc, with larger and heavier discs requiring more energy to spin. Flywheels use the kinetic energy held by the spinning wheel to resist the concentric and eccentric motions of an exercise, as shown in the video above (Petré et al., 2018).
Flywheel exercise works based on the inertial resistance of the spinning flywheel disc, rather than traditional weights that use gravity. The flywheel disc is attached to a central shaft and strap. The strap winds around the shaft as the flywheel spins, which produces eccentric and concentric resistance. Resistance is increased with heavier discs and faster spinning speed.
The movement begins by either spinning the flywheel or by pulling on a band or nylon strap attached to the shaft that runs through the center of the flywheel disc. When the strap reaches its maximum length (which is adjustable), the flywheel disc begins to spin in the opposite direction. The strap begins wrapping around the central shaft providing a heavy eccentric load (Petré et al., 2018). The person then resists the eccentric movement. A high braking force is required but the eccentric load is too great to stop the flywheel so the strap winds around the central shaft despite the person resisting as hard as they can (Burton & McCormack, 2022).
At the end of the eccentric motion, the wheel will briefly stop and then spin the opposite direction. This unwinds the strap and begins the concentric portion. The concentric portion of the lift is typically used to accelerate the flywheel as much as possible. Increasing the spinning speed of the flywheel disc increases the stored energy, and thus the eccentric resistance on the next rep.
Flywheel Inertia Wheels
Inertial discs or wheels provide the resistance in flywheel strength training. The resistance of the discs is indicated by their moment of inertia, usually ranging from 0.01-0.145 kg/m2. The larger the moment of inertia, the more force required to begin spinning the flywheel, and the more difficult it is to slow it down. Increasing disc size and weight increases the resistance, as does the speed that the disc spins (Maroto-Izquierdo et al., 2017).
Flywheel Trainer Attachments
Our Exxentric kBox and Exxentric kPulley Go systems (check them out here) did not come with attachments, but you need some to use the flywheels.
Generally, you will want the same handles, ankle straps, grips and ropes that you might use with a cable weight stack. These will allow you to perform upper body and lower body exercises on either a platform or vertically mounted flywheel system.
Flywheel companies will sell these attachments, but you’re probably better off buying off of Amazon. You don’t need to pay the markup for an Exxentric branded ankle cuff when you can get them for less than half the price elsewhere.
You will also need a belt to do squats on a platform flywheel. We have the Exxentric belts in both of their sizes (small-medium; medium-large). This allows the flywheel strap to attach close to your pelvis. Again, you can buy off-brand versions of this.
Some research has suggested that using a torso harness is the best way to perform squats or single leg work on platform flywheel trainers. The harness decreases the technical skills needed (Petré et al., 2018). Personally, I feel fine using a belt with squats and split squats. However, a harness is a nice option for explosive work because it decreases the pull I feel on my low back/pelvis under high eccentric load. So, it might be worth it to get a harness if you will be using a flywheel to work on your explosive ability.
Flywheel Technique
There is no doubt that it takes a couple of flywheel training sessions before getting the proper technique down.
The timing of when to maximally resist against the flywheel, when to accelerate and how to apply braking forces requires some mental concentration. However, once you get the technique sorted you can quickly feel why flywheel strength training is becoming more mainstream.
Key Instructions for Flywheel Training:
- Apply maximal effort through the entire concentric muscle action (try to accelerate the flywheel throughout).
- Begin resisting the eccentric movement as soon as the flywheel starts spinning in the opposite direction (nylon strap begins unwinding)
- Maximally resist during the last 1/3 of the eccentric portion of the movement (this is where eccentric overload really comes into play) (Maroto-Izquierdo et al., 2017)
- Have a fast turnaround from the eccentric to concentric by immediately trying to accelerate the flywheel again
- Repeat, starting with Step 1
One of the training benefits of flywheels is their use of muscle’s stretch shortening cycle. Training the stretch shortening cycle allows your muscles and tendons to act as springs and store more potential energy from the eccentric portion of an exercise. This results in greater concentric force production (or strength).
The high contraction speed and force required to slow down the spinning flywheel results in an eccentric muscle overload. This increases muscle activity and prepares the muscle to work better in the concentric portion of the lift. As a result, there is increased power production and force output in the concentric portion of the lift if you perform exercises following the above technique.
How is Flywheel Training Different Than Conventional Strength Training?
Flywheel strength training is different than traditional weight training because it does not rely on gravity for resistance. Flywheel training utilizes the kinetic energy of a spinning disc to provide consistent resistance throughout the exercise’s range of motion. Traditional training is limited by the concentric strength of the person, but flywheel training provides high eccentric and concentric loading leading to greater muscle activation.
There are 4 keys ways that flywheel strength training is different from conventional strength training:
- Flywheel resistance is not dependent on gravity
- Flywheels produce resistance through an exercise’s full range of motion
- Muscles can be eccentrically overloaded by flywheels without sacrificing the concentric movement
- You can self-adjust the resistance mid set by changing your exercise technique
Read More: 5 reasons why your home gym needs a flywheel
Gravity Independent Resistance
The most obvious difference between flywheel and traditional strength training is that flywheel training does not rely on weights to be lifted. The resistance created by the flywheel is based on the angular velocity and inertia associated with the spinning discs.
You can create very high resistance through a combination of just a few small discs, rather than having to load a large amount of weight onto a barbell or machine.
This leads to a compact and mobile machine that can provide essentially limitless resistance for your workouts.
The gravity-independent characteristic of flywheel exercises results in continuous resistance and eccentric overload. This isoinertial type of resistance facilitates optimal muscle force generation throughout all the angles of a movement (Wonders, 2019).
Resistance Through Full Range of Motion
The iso-inertial resistance of flywheels results in continuous resistance in the eccentric and concentric portions of an exercise (Petré et al., 2018).
In traditional strength training, the difficulty of lifting a load is different as you move through the range of motion. This is why people have sticking points in their lifts. With flywheel training, you are consistently resisting (in the eccentric) or accelerating the spinning disc (in the concentric).
The amount of braking force or accelerating force that you are applying to the flywheel is naturally altered as you move through a range of motion. You can always have maximal muscle engagement because of the way that the flywheel’s resistance is applied. This results in an appropriate resistance throughout the full range of motion with flywheel training.
The weight used in traditional strength training is dependent on what you can lift in your weakest position of the exercise. On the other hand, some phases of a traditional lift (think about the top ¼ of a back squat) require almost no engagement because the body is naturally stronger in these positions. You are limited by your body’s internal muscle attachments and limb lengths.
Flywheels allow you ACTUALLY train through a full range of motion.
Eccentric Overload of Muscles
Flywheel training is unique because it allows you to eccentrically overload muscles without sacrificing the concentric part of a lift.
Muscles are 20-50% stronger eccentrically than concentrically (Petré et al., 2018). This is why we fail lifts during the concentric portion of the movement.
People often try increase the eccentric load in a lift by doing a slow lowering phase, however it isn’t as effective as the eccentric overload stimulus that flywheel training provides.
Accelerating the flywheel as hard as possible during the concentric phase of an exercise transfers more kinetic energy to the spinning flywheel disc. This increases the braking force needed in the eccentric phase (Petré et al., 2018). If this technique is applied correctly then one can resist the flywheel as hard as possible during the eccentric phase of the movement, without actually stopping the flywheel until the end of the range of motion. This is how an eccentric overload of muscles occurs with flywheel training.
Self-Adjusting Resistance
The weight on the bar or machine determines the resistance that you need to overcome when lifting traditional weights. There’s no real way to modulate the load within a set. However, flywheel training allows you to alter the resistance by adjusting the flywheel disc’s spinning velocity and the range of motion where you apply forces.
Purposefully increasing the speed of the flywheel disc will increase the resistance felt during the movement. The opposite is also true when you slow down the spinning speed of the disc.
You can also dramatically change the stimulus by altering where you apply forces.
One of my favourite exercises to do this is a flywheel pop and drop squat.
You accelerate the flywheel as much as possible on the upward motion of a squat, then race to a ½ squat position. Eventually the nylon strap catches and tries to pull you down from the half squat. You then fight to maintain your position before accelerating upwards again. This ability to fight to hold a position is a drastically different stimulus than performing a regular squat.
The possibilities to alter the resistance mid-rep or mid-set are endless because the resistance is dependent on the flywheel’s inertia and spinning velocity, not a set load.
The Training Effects From Eccentric Flywheel Training
There is sufficient research evidence to confidently say that flywheel resistance training can result in increased muscle size (hypertrophy) and muscle strength in the upper and lower body. In fact, flywheel training is at least on par with, or better than, traditional weight training for strength and hypertrophy building in untrained, moderately-trained and highly-trained individuals (Petré et al., 2018).
Flywheel Training and Hypertrophy
Multiple meta-analyses show that flywheel training is a very effective training method for building muscle. The hypertrophy seen as a result of flywheel training is likely due to the combination of high-load concentric-eccentric coupled contractions (Beato & Dello Iacono, 2020).
Studies have shown significant increases in muscle size after as little as 5 weeks of flywheel strength training (Petré et al., 2018). Typically, studies looking at muscle hypertrophy are longer than 5 weeks so finding large changes in muscle size in that short of a time frame is a very good indicator of the positive effect flywheel training can have on muscle size.
Some research studies even suggest that flywheel training can result in 5-13% greater changes in muscle cross-sectional area compared to regular resistance training (Maroto-Izquierdo et al., 2017).
Flywheel Training to Increase Muscle Strength
Research consistently shows that flywheel training is an effective way to increase muscular strength. It is as effective, or more effective, than traditional weight training. Meta-analysis results have shown that a change in max strength was the muscle property most positively affected by implementing flywheel training.
This is likely do to the increase in muscle fibre recruitment that is associated with heavy loads in both the concentric and eccentric phases of the lift. As a result, flywheel training outperforms traditional training in some studies (Maroto-Izquierdo et al., 2017). This suggests a high likelihood that you would see more strength gains using flywheel training vs. traditional training.
These differences in strength outcomes are more pronounced in the upper body compared to the lower body (Maroto-Izquierdo et al., 2017).
Considerations for Implementing Flywheel Training in Your Routine
Like all types of training, the sets and reps prescribed for flywheel training will change the training stimulus and resulting strength, hypertrophy and power outcomes. Strength and conditioning coaches call this “specific adaptations to imposed demands”, which is the foundation for much of the art and science of being a coach. Systematically changing these variables over the course of time is considered training periodization.
Sets and Reps for Flywheel Training
Most studies on increasing muscle strength and hypertrophy using flywheel training call for 3-6 sets of 8-10 repetitions of a given exercise. In these cases, the first 2 reps of a set are used for developing the spinning speed of the flywheel (and the remaining 8 reps are the “working reps” ) (Beato et al., 2021; Burton & McCormack, 2022). So really, the prescription should really be 3-4 sets of 8 real reps.
The key is that the working reps must be performed at maximum intensity for both the concentric and eccentric motion.
How Often Should You Do Flywheel Training
Most research suggests performing flywheel training between 2 and 3 times per week for a given exercise or muscle group (Maroto-Izquierdo et al., 2017). As low was one flywheel training session per week has resulted in the positive effects that are associated with flywheel training (Beato et al., 2021). The recommendation for frequency of flywheel training is similar to the training frequency recommendations for traditional weight training.
Some sporting contexts include a ‘micro-dose’ of flywheel training (1-2 sets of 2-3 exercises) each week. This gives a dose of the stimulus but is unlikely to cause any noticeable fatigue. Sport organizations may use this micro-dose technique in their competitive season to maintain fitness while focusing on games or matches.
Exxentric kBox4
Concluding Thoughts on Flywheel Training
Flywheel training has taken over the sport performance space and I feel like it’s just a matter of time before it’s a key part of home gyms.
The training stimulus is at least on par, if not better, than traditional training. Both platform and vertically-mounted flywheels offer a near endless resistance level with a very small footprint. The bang for your buck is so high with these products.
I am a huge fan of our Exxentric flywheel systems and use them in nearly every workout I do. I strongly suggest you consider a flywheel as a next purchase for your home gym.
References
Beato, M., & Dello Iacono, A. (2020). Implementing Flywheel (Isoinertial) Exercise in Strength Training: Current Evidence, Practical Recommendations, and Future Directions. Frontiers in Physiology, 11, 569. https://doi.org/10.3389/fphys.2020.00569
Beato, M., Maroto-Izquierdo, S., Hernández-Davó, J. L., & Raya-González, J. (2021). Flywheel Training Periodization in Team Sports. Frontiers in Physiology, 12, 732802. https://doi.org/10.3389/fphys.2021.732802
Burton, I., & McCormack, A. (2022). Inertial Flywheel Resistance Training in Tendinopathy Rehabilitation: A Scoping Review. International Journal of Sports Physical Therapy, 17(5). https://doi.org/10.26603/001c.36437
Maroto-Izquierdo, S., García-López, D., Fernandez-Gonzalo, R., Moreira, O. C., González-Gallego, J., & de Paz, J. A. (2017). Skeletal muscle functional and structural adaptations after eccentric overload flywheel resistance training: A systematic review and meta-analysis. Journal of Science and Medicine in Sport, 20(10), 943–951. https://doi.org/10.1016/j.jsams.2017.03.004
Petré, H., Wernstål, F., & Mattsson, C. M. (2018). Effects of Flywheel Training on Strength-Related Variables: A Meta-analysis. Sports Medicine – Open, 4(1), 55. https://doi.org/10.1186/s40798-018-0169-5
Wonders, J. (2019). FLYWHEEL TRAINING IN MUSCULOSKELETAL REHABILITATION: A CLINICAL COMMENTARY. International Journal of Sports Physical Therapy, 14(6), 994–1000. https://doi.org/10.26603/ijspt20190994