Study Information

Title: Flywheel Resistance Training for Anterior Cruciate Ligament Rehabilitation  ‍

Journal: Published in the International Journal of Strength & Conditioning ‍

Link to Study: https://journal.iusca.org/index.php/Journal/article/view/545

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Purpose

This review examined the potential role of flywheel resistance training (FRT) in anterior cruciate ligament reconstruction (ACLR) rehabilitation. The authors aimed to synthesize current research on FRT in ACL rehabilitation and evaluate its effects on neuromuscular outcomes, while also proposing strategies for implementing FRT within different rehabilitation stages.

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Methods

A narrative review with a systematic search approach was conducted following PRISMA guidelines. Three databases (Google Scholar, PubMed, and ScienceDirect) were searched for peer-reviewed studies investigating flywheel resistance training as part of ACL rehabilitation.

Three studies met the inclusion criteria, representing a total of 44 athletes (20 males, 24 females) with an average age of 20.4 ± 3.6 years. The athletes were primarily elite or collegiate team-sport athletes from sports such as soccer, volleyball, basketball, and handball.

Across the studies, the interventions tended to range from 6-8 weeks with 2-3 sessions per week. Two of the studies focused on the Bulgarian split squat, while the third included other FRT exercises like half squats, Romanian deadlifts, hip thrusts, and hamstring curls.  

The studies assessed performance on a variety of neuromuscular and functional outcomes such as isometric strength and rate of force development (RFD), countermovement jump (CMJ) performance, triple hop for distance and unilateral performance measures.  

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Results from reviewed studies

Research comparing flywheel resistance training to traditional resistance training (TRT) during ACL rehabilitation reported several meaningful improvements:

FRT-based vs Traditional ACL Rehabilitation

• One study compared the effects of an eccentric-focused ACL rehab program (featuring 4 FRT exercises) to a traditional program (4).  

• They found that the FRT program resulted in greater isometric squat strength gains for both the injured (+27.1%) and non-injured leg (+28.1%) compared to the traditional program (~15% gains).  

• The strength gains also translated to bigger improvements in countermovement jump height (12.9% vs 6.7%), single leg jump height (+23.8% vs 13.7%) and triple hop distance (+14.3% vs 5.3%).  

Other results:

• The other two studies assessed the effects of a single set of FRT Bulgarian split squats to exhaustion in athletes after ACL reconstruction (1,2)  

• These studies found that FRT significantly improved quadriceps rate of force development (RFD) and improved single leg drop jump height (23.1%) in the injured leg.  

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Proposed FRT Strategies in ACL Rehabilitation

While the research has so far been focused on late-stage rehabilitation, the authors provided perspectives on how FRT could be useful across the entire ACL rehabilitation process. Here are a few key takeaways:

Early Stage

During early-stage rehab, FRT can be introduced at low intensities and exertion levels to the injured limb within a limited range of motion. Because FRT resistance is dependent on what the user puts into each rep, it has a natural form of autoregulation built in. This ensures the resistance can be kept at a level that is appropriate for the athlete’s current capacity and comfort at this stage of the rehabilitation process.  

Concurrently, the athlete can introduce moderate-high intensity FRT on the healthy limb. This has several potential advantages: 1) it provides opportunities for the patient to gain comfort and familiarity with higher intensity FRT before it is introduced to the injured limb, and 2) FRT on one limb has been found to result in benefits to the untrained limb through the cross-education effect (3). While this has not been validated in an ACL rehabilitation setting, it is possible that training the healthy limb at higher intensities could result in some neuromuscular benefits to the injured limb, setting the stage for mid and late-stage rehabilitation.  

Mid-Stage

During mid-stage, the inertial loading and exertion can be gradually increased as range of motion gets re-established and the patient gains comfort and confidence with the loading it provides. Loading and exertion can start at a conservative level and gradually progressed across this stage, dependent on how the patient responds.

Late Stage

Across this stage, the patient can progress to higher intensity and higher velocity FRT movements alongside other methods (e.g., plyometrics) to prepare them for return to sporting demands. Notably, the authors noted that supramaximal eccentric loading could help bridge the gap between traditional rehabilitation and their sport, highlighting the potential benefits of the motorized eccentric overload offered by Exerfly Flywheel devices.    

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Key Takeaways and Conclusions

• Flywheel resistance training has shown promise as a late-stage ACL rehabilitation method, improving neuromuscular and functional outcomes associated with return to play.

• The eccentric overload offered by flywheel training may help restore braking force capacity and deceleration control, which is critical when preparing for return-to-sport readiness.  

• The interventions in the current research are relatively short (6-8 weeks) and limited in terms of application. More research is needed to determine optimal loading strategies and how flywheel training fits into the entire ACL rehabilitation process.  

• Due to its autoregulatory resistance and eccentric loading capabilities, flywheel training may be a valuable tool across multiple stages of ACL rehabilitation, from early recovery to return-to-sport preparation.

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Additional References

1. Henderson, F. J., Konishi, Y., Shima, N., & Shimokochi, Y. (2022). Effects of 8-week exhausting deep knee flexion flywheel training on persistent quadriceps weakness in well-trained athletes following anterior cruciate ligament reconstruction. International Journal of Environmental Research and Public Health, 19(20), 13209.

2. Henderson, F. J., & Shimokochi, Y. (2025). Inertial one-leg squat training and drop jump biomechanics in athletes with anterior cruciate ligament reconstruction after return to sport. The Journal of Strength & Conditioning Research, 39(2), 156-164.

3. Maroto‐Izquierdo, S., Nosaka, K., Blazevich, A. J., González‐Gallego, J., & de Paz, J. A. (2022). Cross‐education effects of unilateral accentuated eccentric isoinertial resistance training on lean mass and function. Scandinavian journal of medicine & science in sports, 32(4), 672-684.

4. Stojanović, M. D., Andrić, N., Mikić, M., Vukosav, N., Vukosav, B., Zolog-Șchiopea, D. N., ... & Melinte, R. M. (2023). Effects of eccentric-oriented strength training on return to sport criteria in late-stage anterior cruciate ligament (ACL)-reconstructed professional team sport players. Medicina, 59(6), 1111.