kBox (exercise equipment)

kBox
TypeFlywheel training exercise equipment
InventorFredrik Correa; Mårten Fredriksson
Inception2011 (2011)
ManufacturerExxentric
Models madekBox; kBox2; kBox2.5; kBox3; kBox4 Pro; kBox4 Lite; kBox Gen5
Websitehttp://exxentric.com/kbox

kBox is a line of flywheel-based resistance training devices manufactured by the Swedish company Exxentric.

The device uses the inertia of a spinning flywheel to provide variable resistance that varies according to the user's force output during the concentric (lifting/pulling) and eccentric (lowering/return) phases of an exercise, rather than relying on gravity and free weights.[1]

The kBox has been described in sports media as a Swedish-developed flywheel training device used by professional football clubs and athletes.[2] The device has also been used as exercise equipment in scientific studies on flywheel training and test–retest reliability.[3]

History

The kBox was developed by Exxentric co-founders Fredrik Correa and Mårten Fredriksson.[4]

According to a feature in the Swedish business newspaper Dagens industri, Exxentric developed the kBox following interest in flywheel resistance training methods that had been investigated in a space research context, and the company launched its first kBox product in 2011.[4]

Use in sport and research

Elite sport

Swedish sports coverage has reported that professional clubs including Juventus, Inter, Dynamo Moscow, Palermo and Djurgården have adopted the technology as part of strength training and rehabilitation training, highlighting the device's variable resistance and eccentric loading characteristics.[2][5]

Scientific research

Studies in sports science and strength and conditioning research have used Exxentric kBox devices as test platforms for flywheel resistance training protocols. A 2018 study examined unilateral and bilateral eccentric overload flywheel training using a kBox device to assess power and performance outcomes,[6] while a 2020 study assessed the validity and test–retest reliability of performance measurements obtained using an Exxentric kBox4 Pro device across multiple exercises and inertial settings.[3]

Other peer-reviewed studies have examined flywheel resistance training more generally, including investigations of eccentric overload and mechanical outputs during flywheel exercises.[7][8]

A 2024 master's thesis at the KTH Royal Institute of Technology examined machine learning approaches for exercise detection and activity recognition using Exxentric kBox machines and sensor data collected during flywheel training sessions.[9]

Reception

Fitness equipment reviewers have described the kBox as a compact flywheel-based alternative to traditional weight training equipment, noting its emphasis on eccentric loading and its use in strength and conditioning contexts.[10][11][12]

See also

References

  1. ^ Thieme, Trevor (23 October 2025). "What Is Flywheel Training? This Fitness Tool Builds Muscle Without Heavy Weights". Men's Health. Retrieved 23 January 2026.
  2. ^ a b Wagner, Michael (4 February 2013). "Blågult ska lyfta – med rymdträning". Aftonbladet (Sportbladet) (in Swedish). Retrieved 23 January 2026.
  3. ^ a b Bollinger, Laura M.; et al. (2020). "Construct Validity, Test–Retest Reliability, and Repeatability of Performance Variables Using a Flywheel Resistance Training Device". Journal of Strength and Conditioning Research. 34 (10): 2768–2776. doi:10.1519/JSC.0000000000003570. PMID 33105365.
  4. ^ a b Rönnlund, Emil (10 November 2018). "Rymdforskning gav dem idén till träningsmaskinen". Dagens industri (in Swedish). Retrieved 23 January 2026.
  5. ^ Bratts galna gympass – så tränar NHL-stjärnan [Bratt's crazy workout – this is how the NHL star trains]. Sportbladet (video) (in Swedish). Aftonbladet. 25 November 2021. 7 minutes in. Retrieved 23 January 2026.
  6. ^ Núñez, Francisco Javier; et al. (28 March 2018). "The effects of unilateral and bilateral eccentric overload training on hypertrophy, muscle power and COD performance, and its determinants, in team sport players". PLOS ONE. 13 (3) e0193841. Bibcode:2018PLoSO..1393841N. doi:10.1371/journal.pone.0193841. PMC 5874004. PMID 29590139.
  7. ^ Tsoukos, Antonios; et al. (2025). "Acute Effects of Low vs. High Inertia During Flywheel Deadlift on Force-, Power-, and Velocity-Time Characteristics". Sensors. 25 (4): 1125. doi:10.3390/s25041125. PMC 11858857. PMID 40006353.
  8. ^ Belegišanin, Bogdan; et al. (2025). "A Comparison of Bilateral vs. Unilateral Flywheel Strength Training on Physical Performance in Youth Male Basketball Players". Journal of Functional Morphology and Kinesiology. 10 (1): 81. doi:10.3390/jfmk10010081. PMC 11943462. PMID 40137333.
  9. ^ Huang, Yuping (2024). Feasibility of Exercise Recognition on Exxentric kBox With IMU and Machine Learning (PDF) (Master's thesis). KTH Royal Institute of Technology. Retrieved 23 January 2026.
  10. ^ Seedman, Joel (22 September 2017). "Product Review: Exxentric kBox". Advanced Human Performance. Retrieved 23 January 2026.
  11. ^ Mitchell, Coop (20 June 2023). "Exxentric kBox4 Flywheel Training Review". Garage Gym Reviews. Retrieved 23 January 2026.
  12. ^ Grey, Joe (17 October 2024). "Exxentric kBox V5 Review". Gray Matter Lifting. Retrieved 23 January 2026.
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