Developing explosive power with creative solutions for eccentric overload

For decades research has shown numerous benefits for pure strength, speed, and power athletes. Practically speaking, however, it is not always easy to implement eccentric work into training. Achieving eccentric overload with traditional strength training is a pain. Having multiple spotters or adjusting weight releasers are typical forms of accentuating the eccentric phase during compound exercises like the squat or bench press. But the complications involved in eccentric training have left it as an afterthought to many coaches. Advances in flywheel and other technologies are starting to not only make eccentric training more accessible, but allow for new methods of eccentric training. Below I will overview eccentric training, its key benefits, and then share some ideas on how to achieve it using flywheel devices.

What is eccentric training?

Let’s start with a little explanation of what I mean when I’m talking about eccentric training. An eccentric contraction is the motion of an active muscle while it is lengthening under load. Concentric action, on the other hand, is the motion with the muscle is shortened. As an easy example, in doing a squat the quadriceps are lengthening (eccentric) on the descent while shortening (concentric) on the ascent.

Eccentric training focuses on overloading the eccentric phase. This means more than just lengthening the eccentric phase. That is just tempo training. Why? Because we are typically 20-50% stronger during eccentric vs. concentric contractions so, to truly emphasize the eccentric phase, we must lift with greater loads. This is called accentuated eccentric training: coupling eccentric and concentric actions where the eccentric loads are higher. A classic example would be weight releasers where a heavier weight if used on the descent in a squat, then released to allow for a lighter load on the ascent.

The benefits of eccentric training

Why should we even consider eccentric training? Research continues to show a broad range of benefits of accentuated eccentric training, including:

• Higher forces with minimal metabolic cost – An interesting feature of eccentric training is that it allows the production of high force and power output with a low metabolic cost. I have experienced this first hand using connected cycles, which have been the subject of a lot of published research. To do this, two bikes are connected with one long chain while facing each other. One bike pedals forward (concentrically), and one resists backward (eccentrically). The results show that the oxygen requirement for the eccentric cycling is about 14-17% of the concentric cycling at the same workload.
• Enhanced elasticity and stiffness of the musculotendinous unit – Enhancing the stretch-shortening cycle (SSC) improves the ability to rapidly transition from an eccentric to concentric muscle action. Often, the SSC is broken down into fast and slow SSC relating to reactive and explosive strength, respectively. A practical example would be a drop jump for fast SSC and a countermovement jump for slow SSC. Regardless of the SSC type, eccentric exercise has been shown to elicit superior adaptations to traditional strength training to enhance the SSC. Further, a stiffer leg can halve the energy cost of each foot strike which is one key aspect for improving running economy.
• Simultaneously train with high force and velocity – For concentric training higher force means lower velocity. But this force-velocity relationship does not seem to apply to eccentric contractions. Instead of force and velocity following an inverse relationship, you can simultaneously generate high force and velocity to a certain point.
• Target type IIx muscle fibers – With traditional strength training, we see a shift in the proportion of Type IIx muscle fiber to Type IIa. While this is a valuable adaptation for mixed sports, it’s not ideal for pure speed and power sports like jumpers, throwers, and sprinters. Eccentric training maintains or increases the proportion of Type IIx muscle fibers, enhancing muscle contractile velocity.
• Increase muscle length – Eccentric training is likely a better method for increasing muscle length and, therefore, joint range of motion than static stretching since changes within the muscle are structural. In contrast, stretching enhances the tolerance to stretch. These structural changes come as adding sarcomeres in series, improving the ability to produce force at long muscle lengths, and increasing contractile velocity. Essentially, we can move the length-tension relationship up and to the right, leading to reductions in the risk of injury.
• Reduce eccentric muscle soreness with the repeated bout effect – When performing eccentric training for the first time, the DOMS experienced the following day can be debilitating. Rolling out of bed or getting off the couch is like performing a max effort squat. But, after the second or third session, this soreness no longer comes with the same vengeance. The reduction in muscle soreness is a protective adaptation to eccentric exercise known as the repeated bout effect.
• Enhance athletic performance – The above benefits lead to improved athletic performance. Typically, enhanced vertical jump, sprint, and drop jump performance. This makes sense as eccentric specific adaptations prioritize speed and reactivity.

Creative solutions for eccentric overload with the flywheel

Flywheel technology has come a long way, becoming an excellent tool for emphasizing the eccentric phase of movement without needing multiple spotters, supramaximal loads on the spine, or adjusting weight releasers. In other words, it has helped bring eccentric training to the home gym.

The concept of the flywheel is simple: your concentric movement pulls a strap that turns an inertial flywheel. When the strap reaches its end, the flywheel maintains its speed as the strap is pulled back during the eccentric movement. Since the flywheel only gives back the effort produced concentrically, it is not strictly eccentric. But flywheel training makes it easy to find eccentric overload with some simple modifications.

The simplest way is to use the new generation of flywheel devices which have a built in motor such as those from fellow Kiwis over at Exerfly. These allow you to have motorized assistance in the concentric phase (set, for example, at 10%) so that the eccentric phase is boosted to the same degree.

But what if you have a flywheel device without an eccentric motor? You can manipulate how the exercise is performed, so the eccentric phase is more demanding and, therefore, overloaded. Here are some ideas, with some video below as well:

• Delayed braking action – Often the eccentric work is spread out through out the whole range of motion. In the squat, for example, we aim to brake the weight starting at the top of the rep. But if we actively seek to delay the braking action, we can concentrate force production to the end range of motion. We are essentially enhancing eccentric rate of force development and overloading the end range.
• Concentric overload – If we can find some assistance to speed up the concentric phase, then the eccentric phase will be supramaximal. You can also do this manually by assisting yourself with your upper body. Or you can also have a partner join in and help pull the rope with each rep.
• Movement assisted overload – Movement-assisted overload is only possible with certain exercises, but it is very effective where possible. For example a deadlift (concentric) can be paired with a Romanian deadlift (eccentric). Since we can produce much more force concentrically during the standard deadlift, the eccentric phase during the Romanian deadlift will be overloaded.
• 2 up, 1 down – This method is a classic eccentric overload technique often used on machines like the leg curl or leg extension. But you can do the same on the flywheel pushing up with two legs and resisting the eccentric on one leg.

Final Thoughts

Flywheel training has been shown to enhance jump, sprint, and change of direction performance even with short 5–10 week training interventions. For example, academy-aged soccer players saw a 3.3% reduction in flying 10 m sprint times using eccentric flywheel training. On a more personal level I’ve found the flywheel to be an epic tool for overloading the eccentric phase. There is no chance I’d be performing accentuated eccentric training without a flywheel device, especially out of a home gym. I just don’t have the equipment or training partners to do it safely. By simply wearing a hip belt, I can overload my legs without the immense axially loading on my upper body. Further, flywheel training seems not to create the same level of DOMS as traditional eccentric training. For example, I recently performed maximal speed Bulgarian split squats. I’d always have soreness at the glute-ham tie-in using dumbbells or a barbell. But with the flywheel, I had no soreness whatsoever. Many others report similar anecdotal findings. Flywheels are an excellent tool to add to your training arsenal for a simple high-intensity training stimulus.