The MyPhysio High Performance Centre is the first and only clinic in Australia to have the kBox from Exxentric. It is used by our many National champion athletes and "Sports Stars" here and around the world including Cricket Australia and Baltimore Orioles.
The kBox, or kinetic Box, is a flywheel exercise device. The principle with a flywheel device is that, through muscle force, you accelerate or decelerate a flywheel (or flywheels). The force needed to manipulate the speed in the flywheel, depends on the inertia of the flywheel, not on the weight.
This is different to traditional weights which rely on repeated muscle contractions (concentric and eccentric), usually lifting a heavy weight against gravity which means the effect is limited by the fact that only the athlete's last effort is maximal.
The resistance is variable and unlimited. There is no upper limit in how much kinetic energy you can produce in the flywheel motion. This means that you can always use a higher force and accelerate the flywheel more. It is also suitable for rehabilitation in that if you pull less the flywheel will resist less.
With traditional weights only the last repetition is maximal, if you continue until failure then all reps prior to that are submaximal. However, with flywheel devices, if you go maximal then every repetition is maximal, with a higher force and power output early in the set and lower in the end (see diagram). A maximal set with a flywheel device is actually a maximal drop set. This is how flywheel training gives an increased hypertrophic response earlier in the training regimen compared to traditional weights.
Eccentric overload training is regarded as the most effective way to gain strength fast. After reviewing the kBox, Olympic Athletics coach Carl Valle stated it produced "the fastest drug free changes I have seen on paper"! Without risk of injury, training partners or large volumes of weights the kBox can produce eccentric overload training volumes simply by the athlete decelerating the flywheel in a shorter time span than the concentric phase. Ie. Ask the athlete to count 3 on the way up and 2 on the way down.
The Scientific Support
Multiple academic studies have provided support for flywheel training over many years. Here is a selection of some of the more important studies in the field from both athletic performance to older rehab patient groups.
- A Swedish team of scientists (Askling, Karlsson, Thorstensson) showed in 2003, that regular training with eccentric overload, in a flywheel leg curl, decreased the risk of 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%), during 10 months. Both test groups comprised of 15 subjects. And both strength and sprinting speed was increased for the flywheel group. Increased sprinting speed, in already elite trained subjects, is truly remarkable.
"Hamstring injury occurence in elite soccer players after preseason training with 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 was 69.9 +/- 1.3 years old.
"Neuromuscular and balance responses to flywheel inertial vs weight training in older persons"
- Eccentric overload gave significant better response than 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.
"Effects of strength training with eccentric overload on muscle adaptation in male trained subjects"
- 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.
"The effects of eccentric versus concentric resistance training on muscle strength and mass in healthy adults: a systematic review with meta-analysis"