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Flywheel training has strong scientific support.

Multiple academic studies have provided wide support for flywheel training over the past decades. Today, there are over a dozen published or ongoing scientific studies using the kBox at research institutions across Europe, North America and Australia.

Below is a selection of some of the more important studies in the field.


Criterion Validity of Force and Power Outputs from the kMeter

The aim of this study was to assess the validity of the kMeter app for quantifying force and power at a range of different isoinertial loads from a flywheel training device when compared against a criterion measure. Very large to nearly perfect relationships were observed between the two measures, with trivial to moderate bias reported. The researchers concluded that the kMeter app demonstrates acceptable levels of validity.


Record Gains in Muscle Mass After Two Weeks of Flywheel Training

This study showed a paradigm-shifting increase of 5.5% muscle mass in the thighs in only two weeks of flywheel squatting. Historically gains in muscle mass has been thought to be a delayed response to chronic training. However, already in 2008 Norrbrand et al* showed robust and early gains in muscle mass with flywheel but this is now repeated and shown in the normal vertical squat. On top of that, the gains in muscle mass were accompanied with a 30% increase in force and a 50% increase in concentric and eccentric power over four weeks.


Meta Analysis on the Effect of Flywheel Training on Strength Related Variables

Meta analysis made at University of Sport and Health Science in Stockholm (GIH) by Henrik Petré, MSc with supervisor Mikael Mattson, PhD. In the Meta-analysis they looked at outcomes important or defining for performance and eventually 15 studies met the inclusion criteria. The study shows that when it comes to flywheel training and hypertrophy you see significant increases in muscle mass in a shorter time frame compared to traditional weight training. The largest gains and effect sizes associated with flywheel training are seen for maximal strength and power. Vertical movement is showing moderate effect size and horizontal movement small effect size. Data suggests flywheel training is more effective for younger and better-trained subjects.


Meta Analysis: Flywheel Training vs Traditional Resistance Training

Meta-analysis from 2017 including 276 subjects from 9 studies comparing outcomes between flywheel eccentric overload training (FWEOT) vs traditional weight training. The meta-analysis showed significant differences between FWEOT vs. conventional resistance training in concentric and eccentric strength, power, hypertrophy, vertical jump height and running speed, favouring FW-EOT. No surprise for you read up on the subject since actually all studies comparing flywheel devices (with the same design as the kBox) vs weights shows flywheel to be superior. The only studies with a similar or lesser effect are a few using a conic flywheel and sometimes comparing different exercises so not all are actually FW vs weights studies either. This is shown pretty clear on the far right in this graph where all studies favour flywheel training.


Flywheel Training Causes Fatigue: Myth or Fact?

Flywheel training is “known” for giving high degrees of muscle soreness and causing fatigue but what do the studies say? And if so, how can we get around that with monitoring and smart programming? Here is a blogpost compiling the current evidence in this area and also how the kMeter can help you limit fatigue and shorten recovery time.

GUAL ET AL. 2015

Effects of In-Season Inertial Resistance Training With Eccentric Overload in a Sports Population at Risk for Patellar Tendinopathy

A Spanish research group (Gual, G., Fort-Vanmeerhaeghe, A. & Romero-Rodríguez, D. 2015) examined flywheel training with eccentric overload during season for a population at risk for patellar tendinopathy. 81 (38 women and 43 men) basketball and volleyball players conducted a 24-week long intervention period. 37 of the subjects performed one training session a week with flywheel training (squat; 4 sets x 8 reps). 44 of the subjects maintained in their regular scheduled in-season training routines. Results: Both CMJ and Power were significantly (p<0.05) different between groups in favour of the flywheel group. No player in the flywheel group suffered from patellar tendinopathy during the intervention period. Conclusion: Adding a weekly eccentric overload squat training bout to a regular basketball and volleyball exercise routine, enhances lower limb muscle power in flywheel device and vertical jump performance without triggering the patellar tendon complaints. “Effects of in-season inertial resistance training with eccentric overload in a sports population at risk for patellar tendinopathy”


Effects of a 10-week in-season eccentric-overload training program on muscle-injury prevention and performance in junior elite soccer players

A research group consisting of De Hoyo, Pozzo, Sañudo, Carrasco, Gonzalo-Skok, Dominguez-Cobo & Moran-Camacho examined the effect of in-season eccentric-overload training program with flywheel training on muscle-injury incidence and severity and performance in junior elite soccer players. 18 junior elite soccer players from Spain underwent a 10 week intervention period with flywheel training 1-2 session per week. Training consisted of 3-6 sets of six repetitions of leg curls and squats in a flywheel device and was implemented on top of there normal soccer training, 5-6 time a week. The intervention group was compared with a control group that just trained the normal soccer training. Conclusion: 10 –weeks in-season flywheel training focusing on maximal power concentric load and eccentric overload is effective in reducing muscle-injury incidence and severity in elite junior soccer players. In addition, improvements in jumping and sprinting abilities were obtained. “Effects of a 10 week in-season eccentric overload training program on muscle-injury prevention and performance in junior elite soccer players”


Muscle damage responses and adaptations to eccentric-overload resistance exercise in men and women

Both men and women develop Strength, Power and muscle mass with flywheel training. In a study conducted by Fernandez-Gonzalo, Lundberg, Alvarez-Alvarez and de Paz from 2014 they assessed markers of muscle damage and training adaptations to eccentric-overload flywheel resistance exercise (RE) in men and women. 32 subjects (16 men and 16 women) underwent a 6-week intervention period with 2-3 training sessions a week (a total of 15 sessions). Each session consisted of 4×7 reps in the supine leg press. Pre and post test consisted of maximum dynamic strength (1RM), vertical jump performance, power at different loads of 1RM (40, 50, 60, 70, 80 %) and measuring thigh muscle mass with DXA. Results showed comparable increases in strength, power and muscle mass across sexes, even though men showed slightly greater improvements in the 1 RM and Power at 80% of 1 RM, than women.


Quadriceps muscle use in the flywheel and barbell squat

This study, published in January 2011, compares squats in a flywheel device and traditional barbell squats.


Flywheel resistance training calls for greater eccentric muscle activation than weight training

This study shows higher eccentric muscle activation with flywheel training. This could explain the earlier hypertrophic response seen with flywheel training compared to traditional weights.


Blood lactate and hormonal responses to prototype flywheel ergometer workouts

“Although the FERG (Flywheel Ergometer) was originally designed for microgravity, the effort put forth by current subjects was like that for workouts aimed at greater athletic performance and conditioning. Practical applications suggest that eccentric actions should be used for flywheel ergometer workouts geared toward muscle mass and strength improvement.” (March 2010). Citation from study, published March 2010, shows benefits of sets with concentric-eccentric actions over concentric-only.


Effects of strength training with eccentric overload on muscle adaptation in male athletes

Eccentric overload gave significantly better responses compared to ordinary con-ecc in trained male athletes. A higher expression of mRNA for MHC IIx, fibre typ IIX CSA and glycolytic enzymes makes the author draw the conclusion that this type of training is good for explosive sports and performance since the eccentric overload gives a transformation of the muscle to a faster phenotype.

ROIG ET AL. 2009

The effects of eccentric versus concentric resistance training on muscle strength and mass in healthy adults: a systematic review with meta-analysis

A meta-analysis from 2009 including 20 studies showed higher increases in total and eccentric muscle strength and higher increases in muscle mass and cross-sectional area with high-intensity eccentric training.


Neuromuscular and balance responses to flywheel inertial versus weight training in older persons

“Quadriceps flywheel loading not only produces a greater increase in power than weight training but its physiological benefits also transfer/overspill to the plantar flexor muscle-tendon unit resulting in a significantly improved balance.” Flywheel training improved power more than weight training and also improved balance. The study subjects were 69.9 +/- 1.3 years old.


Early skeletal muscle hypertrophy and architectural changes in response to high-intensity resistance training

Study by Seynnes, de Boer and Narici (2006) shows remarkable hypertrophy after 5 weeks of flywheel training. A small test group showed increase in muscle mass in quadriceps by 0.2% per day for the first 20 days of training and after 5 weeks by 7% on total average. Strength also increased by 38% in those five weeks.


Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload

A Swedish team of scientists (Askling, Karlsson, Thorstensson) proved in 2003, that regular training with eccentric overload, in a flywheel leg curl, decreased the risk of a hamstring injury in elite soccer players during the season. The flywheel group had 3 injuries (20%) and the group with no-flywheel had 10 injuries (67%) in 10 months. Both test groups comprised of 15 subjects. Moreover, both strength and sprinting speed were increased for the flywheel group. Increased sprinting speed, in already elite trained subjects, is truly remarkable.