Building A Strong & Powerful Backside for Athletic Performance

Excelling in activities such as sprinting, jumping, cutting, and reacting to in-game situations are prevalent duties for athletes across a variety of sports. In this blog post, S&C coach Matthew Ibrahim explains the benefits of flywheel training in posterior chain strength development and injury prevention with the kBox. Read all the details below.

Key Points

  1. Sprinting, jumping, cutting, and reacting to in-game situations are common tasks required from athletes in various sports across the board.
  2. Developing a strong and powerful backside (posterior chain) is a surefire way to perform at higher levels in all of those categories within your sport, in addition to reducing the potential risk of injury.
  3. Eccentric training strategies used with the kBox flywheel system can help to improve outcomes in posterior chain strength and power development with our athletes.

Posterior Chain: Defining It & Reviewing Common Sport Injuries

Here is an easy way to better understand and define the posterior chain of the lower body in the image below:

To further illustrate this region and how it translates to the weight room, here are a few training examples with the kBox:

In terms of the roles in athletic performance for all 3 regions, here is how we can view them:

  • Calf Region: Ankle Plantarflexion & Dorsiflexion ⇒ Lower Body Force Application (i.e., jumping/landing, changing direction, lower leg “spring loading”, etc.)
  • Hamstring Region: Hip Extension & Knee Flexion ⇒ Lower Body Power & Force Application (i.e., sprinting/accelerating, slowing down/decelerating, jumping/landing, etc.)
  • Glute Region: Hip Extension ⇒ Lower Body Power (i.e., jumping, leaping, sprinting, etc.)

Unfortunately, we’re seeing a high rate of sports injuries within these 3 important lower body regions of the posterior chain, which stresses the importance of developing both strength and power to combat the potential injury risks.

Here is what the current research and evidence are telling us as practitioners within the sport and athletic performance:

  • Calf Region: “Calf muscle strain injuries (CMSI) are common across sports involving high-speed running or high volumes of running load, acceleration, and deceleration, and upon fatiguing conditions of play or performance” (Green et al, 2017).
  • Hamstring Region: “Hamstring strain injury (HSI) is one of the most commonly reported sports injuries” (Wing et al, 2020).
  • Glute Region: “Gluteal tendinopathy is the most common local source of lateral hip pain” (Grimaldi et al, 2015).

Importance of Eccentrics & Flywheel Training

The kBox flywheel system is an intelligent training tool that allows the athlete to essentially work against the variable inertia of heavy steel flywheels. This becomes especially important if our goal is to help athletes build strength and power in the 3 key regions of the posterior chain, in addition to reducing the risk of injury.

Higher levels of effort come with a heavier level of intensity when using the kBox, which is what we want in order to allow for a physiological adaptation to take place. When an athlete unleashes maximum effort on the kBox, this ultimately provides a bit of an overload. However, more importantly, using advanced overloading methods equates to a greater eccentric (lowering portion) force. Overall, this amount of physiological stress has its merit, especially as we learn to both absorb force (decelerate) and produce force (accelerate) with training exercises.

Current research suggests that “eccentric overload has demonstrated efficacy in the literature as a means of increasing eccentric work and rate of force development (RFD)” (Wagle et al, 2021). In addition, we can also find in the research that “short-term incorporation of slow accentuated eccentric loading (AEL) has been shown to be superior to traditional resistance training (TRT) in improving strength and maximum velocity sprinting speed” (Douglas et al, 2018).

Eccentric loading refers to a lengthening muscle contraction. Most often known as the “lowering” aspect of an exercise, the eccentric component causes a great deal of warranted muscle damage, which must be utilized strategically from a return on investment standpoint. A more advanced version of eccentric loading is referred to as Accentuated Eccentric Loading (AEL) where there is a primary emphasis on the eccentric (descending) aspect of a lift.

All in all, the kBox flywheel training system is a pivotal tool to use when promoting eccentric training and eccentric overload for the purposes of increasing posterior chain health, strength, power, and performance.

Posterior Chain Training Application with the kBox

With a primary focus on the 3 key lower body regions of the posterior chain, let’s review exercises that you can apply right away with your athletes. 

For a complete breakdown of posterior chain strength and power development in the lower body, check out the brand-new Exxentric Online Academy course below:

Posterior Chain Training for Athletic Performance


It’s important for coaches and practitioners to better understand the posterior chain as a whole as it pertains to human movement and function in sports.

Moreover, it’s vital to check in on the current status of athletic injuries in sports related to the posterior chain, in addition to ways to reduce injury risk and enhance athletic performance.

In doing so, this will allow us to utilize better eccentric training strategies with the kBox flywheel training system to improve outcomes in posterior chain strength and power development with our athletes.


– Douglas J, Pearson S, Ross A, McGuigan M. Effects of accentuated eccentric loading on muscle properties, strength, power, and speed in resistance-trained rugby players. J Strength Cond Res. 2018; 32(10):2750-2761.
– Green B, Pizzari T. Calf muscle strain injuries in sport: A systematic review of risk factors for injury. Br J Sports Med. 2017; 51:1189-1194.
– Grimaldi A, Fearon A. Gluteal tendinopathy: Integrating pathomechanics and clinical features in its management. J Orthop Sports Phys Ther. 2015; 45(11):910-922.
– Wagle J, Cunanan A, Carroll K, Sams M, Wetmore A, Bingham G, Taber C, DeWeese B, Sato K, Stuart C, Stone M. Accentuated eccentric loading and cluster set configurations in the back squat: A kinetic and kinematic analysis. J Strength Cond Res. 2021; 35(2):420-427.
– Wing C, Bishop C. Hamstring strain injuries: Incidence, mechanisms, risk factors, and training recommendations. Strength Cond J. 2020; 42(3);40-57.


Author Bio

Matthew Ibrahim is an experienced Strength & Conditioning Coach, College Professor of Exercise Science and Ph.D. student in Human and Sport Performance with a demonstrated history of working in the high-performance setting since 2007.
As a public speaker, he has presented nationally at the National Strength & Conditioning Association (NSCA) National Conference, the Perform Better 3-Day Functional Training Summit, the Sports Academy (formerly Mamba Sports Academy) Human Performance Summit, EXOS inside Google Headquarters, Equinox and Stanford University, in addition to several international presentations in Europe.
His work has been featured in Men’s Journal, T-Nation, Science for Sport,, Exxentric, TrueCoach and TrainHeroic.





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