What is Patellar tendinopathy?

Patellar tendinopathy (PT) is one of the most common overuse knee injuries among athletes (9).  PT can occur across both physically active individuals and athletic populations.  The prevalence rate is particularly high for athletes who participate in sports that have a high involvement of running, change of direction task, and especially jumping.  In fact, PT is often referred to as “jumpers’ knee” due to its impact on sports such as basketball and volleyball.  For instance, approximately 45% of volleyball players and 31% of basketball players that competed at the national level experience PT symptoms at some point (3).  

PT can be classified as the tendon failing to adequately heal, and often leads to chronic pain, and impaired function (1).  In the sports world, this results in an inability to train/play, manage adequate workloads, and reduced performance (1).  Thus, it is extremely important to manage, improve and even prevent PT.  One of the most common and effective ways to improve PT is through eccentric training.  Eccentric training has been shown to promote tendon remodeling by stimulating collagen synthesis, improved metabolism of the tendon, increases in tendon stiffness, and central adaptations of both agonist and antagonist muscles (4).  In addition, eccentric training can improve eccentric muscle coordination and strength, in which the lack of these physical qualities could be potentially considered as risk factors for PT (4). 

What is flywheel resistance training?

Flywheel resistance training (FRT), a form of eccentric training, has been gaining traction in the treatment of PT.    FRT provides your athletes with roughly a 1:1 ratio (concentric:eccentric) of resistive load.  Meaning the energy that is applied by your athletes in the concentric (upward) phase is also applied equally in the eccentric (downward) phase.  When we compare the forces to traditional training, FRT can yield similar outputs concentrically, yet much greater outputs eccentrically (2). 

Flywheel resistance training and Patellar tendinopathy

Exerfly and FRT has recently taken the rehabilitation field by storm due to its ability to effectively treat multiple injuries including PT.  Similar to other forms of eccentric training, FRT can provide an extremely high eccentric stimulus which is crucial for tendon adaptations and the treatment of PT.  In addition, Exerfly’s motorized technology gives you the ability to create a true eccentric overload (eccentric output > concentric output).  The motorized technology can boost the eccentric repetition up to 80% greater than the concentric repetition, which allows coaches to easily overload and progress the eccentric phase.  For more information on the motorized technology visit our blog here.

FRT also provides you with user-dependent resistance.  Meaning the resistance that is applied will always be proportional to the athlete’s effort.  Making it a great tool regardless of the stage of rehab.  For instance, FRT can be utilized in the early stages at low intensity and can be gradually increased as pain and discomfort subsides.  The user-dependent resistance also allows for it to be utilized across different strength levels, ages, and training levels.

A major difference between traditional eccentric training and FRT is its ability to create eccentric overload at high speeds.  Traditional forms of eccentric training are often performed at high intensities with slow movements speeds.  However, Rees et al. (5), suggested that high speed eccentrics may lead to greater tendon remodeling in athletes with tendinopathy.  FRT with Exerfly’s motorized technology does an exceptional job at creating high speed movements while still providing an eccentric overload.  Additionally, these high-speed eccentrics can play a crucial role in the return to sport process as it can expose athletes to game-like eccentric speeds in the weight room before they step on the court or field.

Finally, FRT can provide you with the ability to apply eccentric overload in multidirectional planes.  This allows you to recreate similar sport specific tasks or movements.  The video below highlights an athlete performing a similar movement to a triple jump.  This athlete suffered from PT symptoms specifically in his final step of his jump, and this pain dissipated following the incorporation of this exercise into his program.

 Flywheel resistance training and Patellar tendinopathy: Research

Although FRT has increased its popularity in its ability to treat PT, the current body of literature is still limited.  A recent systematic review that analyzed 5 investigations reported that FRT can improve strength, power, increase tendon cross-sectional area and reduced tendon temperature among athletes who are at risk or diagnosed with PT (8). More specifically, a 16% increase in cross-sectional area of the patellar tendon was found in healthy runners after performing flywheel squats for 6 weeks, 2x per week (7).  Additionally, Ruffino et al. (6), reported improvements in pain and function following a 6-week FRT program among athletes who were diagnosed with PT.  Although limited, the current literature does support why so many practitioners are utilizing FRT in the field to rehab PT.

Practical applications

The table below gives you a general guideline on how to program a flywheel squat for athletes with PT.  Although this program is only written for the squat, it is recommended that you implement other exercises such as flywheel split squats, Bulgarian squats, and knee extensions (note: loading and reps will need to be slightly altered for these exercises).  The loads listed below are generalized towards the athletic population.  It is always recommended that you take an individualized approach to loading by utilizing the metrics provided in the Exerfly App (i.e. velocity or power).

When initially introducing FRT it is recommended to start with moderate effort at moderate loads with patients suffering from PT.  This will help mitigate any exercise induced symptoms and ensure proper technique is achieved.  As their technical proficiency increases and ability to manage the flywheel load, the intensity of the exercise can be increased by the athlete’s effort during the initial two phases (acclimatization and progression).  Concurrently, you should be able to see the concentric output (i.e. average velocity of a set) progressively increase for each training session (Figure 1).  For more familiarizing your athletes to FRT, visit our getting started blog here.

The 3^rd phase of this program incorporates the motor, which will provide your athletes with an eccentric overload.  Whereas the final phase also incorporates the motor, but at high speeds to replicate on field/court demands.  The duration and progression of each phase are based on an individual’s ability to adequately perform flywheel movements and their ability to respond to the stimulus (i.e., improved symptoms).  Athletes may need longer or shorter time in each phase based on their movement quality and severity of symptoms.

Conclusion

Patellar tendinopathy is a very common knee injury and is often treated with eccentric training.  FRT has recently taken the rehab field by storm due to its versatility and its ability to apply eccentric overload across a wide range of rehab stages.  If you are working with athletes that are suffering from PT symptoms, contact us today!  

References

1. Aicale, R, Oliviero, A, and Maffulli, N. Management of Achilles and patellar tendinopathy: what we know, what we can do. J Foot Ankle Res 13: 59, 2020.

2. Hu, Z, Liu, Y, Huang, K, et al. Effects of inertial flywheel training vs. accentuated eccentric loading training on strength, power, and speed in well-trained male college sprinters. Life 14: 1081, 2024.

3. Lian, ØB, Engebretsen, L, and Bahr, R. Prevalence of jumper’s knee among elite athletes from different sports: a cross-sectional study. Am J Sports Med 33: 561–567, 2005.

4. Murtaugh, B and M. Ihm, J. Eccentric Training for the Treatment of Tendinopathies. Curr Sports Med Rep 12: 175–182, 2013.

5. Rees, JD, Lichtwark, GA, and Wilson, AM. The mechanism for efficacy of eccentric loading in Achilles tendon injury; an in vivo study in humans. Rheumatol 47: 1493–1497, 2008.

6. Ruffino, D, Malliaras, P, Marchegiani, S, and Campana, V. Inertial flywheel vs heavy slow resistance training among athletes with patellar tendinopathy: A randomised trial. Phys Ther Sport 52: 30–37, 2021.

7. Sanz-López, F, Berzosa, C, Hita-Contreras, F, and Martínez-Amat, A. Effects of eccentric overload training on patellar tendon and vastus lateralis in three days of consecutive running. Knee 24: 570–579, 2017.

8. Soler Lomba, R, González Castro, A, Hernández Lucas, P, and Machado De Oliveira, I. Effects of inertial flywheel training on risk factors for tendinopathy: systematic review. Retos 66: 108–119, 2025.

9. Swenson, DM, Collins, CL, Best, TM, et al. Epidemiology of knee injuries among U.S. high school athletes, 2005/2006–2010/2011. Med Sci Sports Exerc 45: 462–469, 2013.