LegFlexx: Transforming The Seated Leg Curl With Flywheel Overload and Feedback Technology
Introducing our latest innovation in flywheel-based training, a single-exercise machine designed to target a specific…
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.
This study aimed to examine whether flywheel resistance exercise training improved muscle strength, muscle power, and physical function in older adults. 36 participants (64 ± 5 years) were randomly allocated to either a flywheel training group, where they underwent 6 weeks of resistance training on a flywheel squat device, or a control group. Researchers looked at isokinetic concentric and eccentric knee extension and flexion peak torques and mean power as well as physical function (CST) and walking speed. Results showed that flywheel resistance exercise training (2–3 times/week) has the potential to enhance muscle strength, muscle power, and physical function in older adults. The study also showed great compliance with the subjects on average taking part in 14 out of 15 planned sessions.
The aim of this study was to summarize the evidence on postactivation potentiation (PAP) protocols using flywheel eccentric overload (EOL) exercises. In total, 7 eligible studies were identified and analysed based on four criterias: inertia intensity, PAP time window, total volume and experience from EOL exercises (fully explained in the article). Based on the current evidence, the authors concluded that EOL exercise can be used to stimulate PAP responses to obtain performance advantages in various sports. However, future research is needed to determine which EOL exercise modalities among intensity, volume, and rest intervals optimally induce the PAP phenomenon and facilitate transfer effects on athletic performances.
Male participants underwent eight weeks of HIIT followed by eight weeks of IRT, which involved seated knee extension using a flywheel ergometer. While after both HIIT and IRT the men saw improvements in muscle mass and composition, only IRT had an effect on the voluntary activation and muscle torque of the quadriceps. Intramuscular Adipose Tissue (IMAT) also saw greater benefit from the IRT. This study supports the benefits of resistance training, helping to combat sarcopenia, which occurs as part of ageing and preventing the increase of IMAT.
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.
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 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 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 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.
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”
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”
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.
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.
“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.
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.
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.
“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.
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.
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.
Kickstart your Flywheel Training with our entry-level kBox model. The perfect device for strength training, rehabilitation, injury prevention, and training in general. Available with our free Flywheel Training app to design all your kBox workouts.
Broader range of resistance provided by the lightest kBox model, practical to pack and bring with you on the move. Its built-in kMeter feedback system allows you to monitor your progress in real-time.
The premium and best-selling kBox model with the largest performance area. Made for intense workouts and serious strength building exercises. Its built-in kMeter feedback system allows you to monitor your progress in real-time.
The kPulley unlocks a variety of horizontal movements, creating limitless training possibilities especially when combined with the kBox. Its built-in kMeter feedback system allows you to monitor your progress in real-time.
Kickstart or enhance your Flywheel Training setup with one of our entry-level models. Its compact size and design provides you with freedom in your training, while also maintaining a great capacity for loading & variable resistance.
These uniquely mobile machines allow you to incorporate leg extension & flexion movements into your training like never before with variable & unlimited resistance. Progress can be monitored in real-time and beyond through the kMeter app.
Exxentric AB is a company developing innovative, science-based training equipment and methods for strength and conditioning, including the LegExx, LegFlexx, kPulley, and the kBox used by performance coaches, personal trainers and physiotherapists worldwide since 2011.
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