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The driver behind the development of motorized equipment is to make the training more efficient while maintaining safety and control of progression. The typical ability to control load and speed during both the concentric and eccentric phase of any movement allows for the application of specific training modalities and research have shown promising results for motorized equipment when comparing with traditional methods. A recent study showed that a combination of eccentric overload, isokinetic strength training and ballistic training yielded better results than both Olympic weight lifting and tradition weight training.
Over the last 10 years, resistance training beyond barbells and dumbbell has merited a comprehensive guide to those options in training and rehabilitation. Terms like “isokinetic,” “isotonic,” and “isoinertial” are brought up in budgeting circles, sometimes explained correctly and sometimes misunderstood. For the sake of simplicity, this review will cover any resistance machine that requires electricity and a computer or similar.
The market is early stage and therefore cloudy with both biological science and engineering, so this guide covers why and what steps to take in order to make a purchase. At this moment, a half dozen or more companies are viable options, since it takes more than just building a machine to be a solvent company. If rehabilitation, human performance, research, and health promotion interest you, you will benefit from this outline and these recommendations.
Motorized Resistance and Muscle Contraction Types
The cornerstone of an electronic resistance machine is that the resistance comes from a motorized option, usually controlled by a combination of the settings, the user, and sometimes a computer. Typical barbells, flywheels, and cable machines don’t require electric power to change their resistance, so any equipment that can run without power but uses technology cannot fall into this category of product. Plenty of traditional squat racks and platforms are made “smart” because they use sensors and displays, but the technology doesn’t affect the resistance type. If power and programming are not adjusting the load, the device is simply not motorized resistance—it’s just a traditional piece of equipment with technology features.The basis of an electronic resistance machine is that the resistance comes from a motorized option. Click To Tweet
Most, if not all, equipment not only produces resistance, but also measures the output of the resistance from the user. Some systems display the output in real time and some record and display it through a computer or tablet wirelessly. Hardwired options for display still matter, because USB connections also power devices and wireless connectivity can benefit from redundancy. An easy way to summarize the function of motorized resistance machines is that they use technology to create, measure, and report human output in training.
While some machines simply create resistance and don’t report much data on how that load interacts with a human, the benefit of specific resistance modes is the central driver to adopting such equipment. A resistance that can’t be found in traditional gravity and pulley solutions is the primary value of the machine, and data from it is secondary. Quantification of the load is expected, but how the load interacts in detail is usually a feature within the industry. For example, the kBox has a measuring device for the flywheel to add more precision, but we see a cause and effect with indirect testing.
As mentioned earlier, users want specific resistance modes when investing in motorized machines. Typical research and rehabilitation machines provide isokinetic resistance, where the device manipulates force and speed to be uniform in velocity by matching resistance up and down. In the past, research and sport science used simple assessments like hamstring and quadriceps testing to observe changes or profiling, but much of it was limited due to the open chain muscle actions and lack of relationship to complex movement and performance. Isokinetic training is still relevant, is effective, and increasingly an interesting option as more equipment focuses on multi-planar motion and multi-joint actions.
Flywheels can provide a rapid eccentric force, but true overload is when the net demand is higher than the concentric component. Dialing up eccentric forces with machines is possible with an array of equipment lines providing controlled overloads at specific ranges of motion and speeds. Obviously, safety is a factor, and machines are designed to reduce risk and improve outcomes from engineering and coaching education.
Isoinertial resistance doesn’t rely on gravity, is balanced between concentric and eccentric nature, and is relatively uniform. Isoinertial resistance is commonly applied with flywheel training, but some systems mimic that modality with biofeedback sensors and loading responses. Isoinertial resistance is about manipulating momentum and forces, not manipulating the gravitational responses of loads.
Isotonic resistance is very broad; thus, most machines and traditional equipment will provide some sort of isotonic stimulus. Isotonic is just creating a change in tension on muscle, and nearly any exercise outside of isometric training (static contraction) will provide a dynamic contraction. Some muscle groups will co-contract or statically contract to stabilize a joint or transfer force, but most will lengthen and shorten during movement and training. The typical Isotonic resistance is air driven resistance, where there is no inertial component present.
One of the advantages with motorized equipment is the possibility to control inertia. Unlike isotonic air driven systems with no inertial effect, solutions which are directly controlled by an electric motor can simulate a weight in a gravitational field during acceleration. Hence the inertial resistance as well as the set load has to be overcome to move the simulated weight. There’s nothing strange with that as a regular barbell or a weight stack will act in the same way. The interesting part is during the deceleration of the movement where a regular weight stack will provide very little resistance or even start to fly on its own in a fast deceleration. This is not very efficient training, is unpleasant, and is a barrier to training explosive movements with regular weights. A motorized solution can in contrast apply resistance also in the deceleration phase which means the athlete is always in contact with the load and can perform high speed multiple repetitions at a high velocity and change of direction frequency.
Collinear resistance is a new and completely unique training modality for sports performance and rehabilitation. Unlike cables and gravity dependent options, the system provides resistance to any movement in all dimensions simultaneously. Users have unlimited freedom in both motion and speed, and every movement is recorded to capture actionable data. While Collinear resistance loads all three planes concurrently, current technology options can reduce the dimensions to one or two. In addition, high velocity or ballistic loading is possible with collinear resistance. No research exists yet on collinear resistance but the modality is expected to grow as more research and adoption increases.Two barriers to resistance machine usage are the stigma attached to them and a lack of education. Click To Tweet
More resistance options exist, including vibration, accommodating methods, and assisted solutions that reduce the demand of gravity on conventional training. The main point is that outside of barbells, alternative forms of training exist and provide powerful stimuli to athletes if used correctly. The main barrier for motorized resistance machines is the education gap.
General Machine Design Factors to Consider
When investing in equipment, a priority exists, and that starting point is the overall construction and design. Most companies that create motorized machines are not in the business of welding or equipment-making; they are in the business of providing a comprehensive solution. Companies have the burden of not only creating a well-designed training system, but also creating electronics and calibrating the validity of the load readings, which are very demanding processes. In short, resistance machines that are analog (not powered) just need to ensure that pulleys and gears are oiled and in good standing, while motorized or sometimes-called “robotic” machines have much higher demands.
Manufacturers should design motorized machines to the same level of expectation as non-motorized machines. In addition to the overall structure, additional needs such as the resistance engine (whether the belt is motorized or pneumatic) require equal attention. Finally, after the hardware is complete and provides valid and accurate force outputs, software demands should meet the technology expectations of the current market.
In general, most of the manufacturers or providers of resistance technology struggle to have every facet of their equipment on par with industry standards. This is normal and far from ideal, but the gap is closing with every generation. In the past, equipment was dated and primitive, but now the same aerospace quality of design and engineering is available to the market.
The same rules and approaches in adopting strength training equipment apply to specialized resistance technology. Space, portability, workflow, and event aesthetics all matter when making a purchase. On average, a disconnect between designer and user usually exists, due to the fact few engineers have experience in the coaching realm. While consultants are available, most don’t have enough creativity or expertise to fulfill both needs; thus, most systems evolve very slowly. Shipping, instruction, and development costs cause many machines to run in the neighborhood of tens of thousands of dollars, but the expectation is that the value makes up for the upfront costs.
Safety Considerations of Machines
Many of the myths and misconceptions about the safety of machines come from the experiences of others who train with them. In general, most machines have safety components and mechanisms in place to reduce risk, but even the best designs will fail when people use equipment incorrectly. It’s the expectation, regardless of the design, that the users be competent with the equipment. Most of the protection is in the physical construct of the machine, with safety systems in place in the firmware and emergency buttons for at-risk scenarios. The majority of machines pose little to no risk because they match loads from users and have actual structural limitations to prevent catastrophic injury.
Due to the fact many isokinetic machines are used for rehabilitation, it’s reasonable to say that machines are likely to be a safe option for training as well, provided the absolute and relative loads are appropriate. Exercise selection, load progression, and athlete readiness are all factors that the practitioner is expected to be proficient in, and if they are not, sometimes the companies that provide the equipment also provide training. Eccentric overload, especially high intensities and velocities, is a powerful option and requires responsibility by all parties. Motorized systems have been historically safe and no pattern of problems are known in the industry.
Validity and Accuracy of the Data
The most difficult challenge with any new technology is vetting the quality of the data, and with resistance machines, this can be a real struggle. Research is slow to respond to trends in training, as fads come and go, and scientists get weary of examining an area that may not be relevant a year or two later. Equipment providing research data to evaluate change must be vetted against existing measurement options that have already been established as accurate, reliable, and precise. Coaches and therapists expect that information provided by the machines they use is at the same research-grade level as the tools used by scientists. Having an expectation of high accuracy and having the machine be user-friendly and efficient is difficult, but still a requirement in the current market.
The reliability of the data is usually paramount to everyone working with athletes because the most important goal is to see progress. Accuracy is knowing that the given information truly represents the output of the device, but sometimes indirect measures or estimations are good enough to give a working idea of how things are trending. Precision matters, but with most resistance machines, the acceptable level is usually fairly easy to achieve. Finally, the system’s validity, or how it truly measures what it is supposed to, is highly connected to the scientific standards set in the field. For example, a system measuring leg power using a leg extension would be false, as single joint evaluation of one muscle can’t represent the entire lower extremity that includes an array of muscles and multiple joint systems.
All companies listed have either research or documentation on their systems for evaluation. You can cross-validate data through self-investigation, but only a few companies have leasing agreements. Some companies have had multiple studies that indicate the data is useful in clinical or training sessions, but the data can’t be considered research or medical grade. Equipment that delivers reliable data is fine for field testing for intervention changes, but less valuable than highly precise and accurate data. Reports and output for athlete or patient feedback will vary from simple readouts from LCD screens to comprehensive reports on screen or via hard copy.
New and Top Options in the Market
Some giants exist, but most of the resistance options are small companies that are highly specialized. One obvious fear of teams and facilities is that a new company will form and go insolvent after they invest heavily in the new technology. While that can happen, it’s most likely that even after a company dissolves, a third party can still support most equipment. Several companies have grown to be major players in the fitness and performance space, and several have existed for more than 20 years.
Here are the new and leading options that are good examples of what the scope of the market can offer. Each company has strengths and specializations that may or may not fit your specific needs.
Keiser: Based in California, this company is a leader not only in technology-driven resistance machines, but in the global fitness market as a whole. Keiser uses a pneumatic pressure option, basically taking air and converting it to isotonic resistance using motorized pumps. Keiser has spread to all areas of performance, ranging from seniors to elite sport, making them an established brand over the last few decades. The most important market is the general fitness space, and Keiser leads here with an array of models covering total body as well as specialized pieces. Each machine uses a digital screen to show instant feedback and precise estimations of resistance, ranging from therapeutic loads to massive forces for elite athletes. Keiser has a strong presence in the cycling industry, as their indoor bikes are very popular.
Biodex: This New York company is world-renowned for isokinetic testing, and also involved in other areas of assessment. Biodex has been in business for over 60 years, and is the largest of all the brands listed. While they are the leader overall with market saturation, they have not made many changes in their equipment over the years and it is not appropriate for training. However, the data integrity is especially high, and it’s considered research-grade in the industry. Finally, most of the equipment is designed for general rehabilitation assessment, not for progressive return to play, like newer companies. Dynamometers are testing tools, not training equipment for actual closed chain exercises, as those are open chain devices that isolate muscles and joints.
1080 Motion: 1080 Motion makes the Quantum and the Syncro, two resistance machines that both use a patented robotic mechanism of force transmission. Each system provides an impressive set of modes of resistance and operates through a touchscreen which also synchronize with a cloud data storage. The Quantum is similar to a cable column, while the Syncro is essentially two Quantums fused with a squat rack. In addition to the resistance machines, the Swedish company provides a resisted sprint machine, the 1080 Sprint, that can provides both resisted and assisted options to athletes. TBoth team sport facilities and rehabilitation clinics as well as research institutions use 1080 Motion equipment. The machines provide every common resistance type and also include a vibration setting for those looking to incorporate pulsating force, as well as the ability to control inertia which allows for ballistic training.
Exerbotics: The Tulsa company provides a small line of commercial equipment for those looking for eccentric training, as well as iso-velocity resistance. Exerbotics’ equipment manipulates the resistance and speed of movement, with fixed mechanical vector paths based on user height. The specialized equipment solutions are unique in that they use linear actuators, not pneumatic or cables. They boast a 10-year durability standard and include readouts with each system. Exerbotics equipment has both closed-chain and open-chain movements, including an innovative hamstring system called the CrossFire.
Boston Biomotion: Originally founded at MIT, the newest option on the market now operates out of New York City. Boston Biomotion’s flagship product is the Proteus, which resembles a giant arm and provides a radical approach to resistance. Termed “collinear,” the resistance is a true 3-D force tool and just entered the market in 2017. The system has won innovation awards and is currently a leasing solution for both rehabilitation and general training. The software is complete with reporting, instant feedback, and data export features. Similar to cable motions, but with concentric-only resistance in multiple plains, the system is ideal for those wanting high speeds and high ranges of motion.
FastTwitch Isokinetics: Formerly TEKS, this Australian company has an isokinetic solution in two full lines of machines, one for performance and the other for rehabilitation testing and training. Similar to Biodex and Exerbotics in technology and design, the company’s products are available outside of Australia and appear to be viable options for professional teams such as the Chicago Bulls, Sacramento Kings, and Dallas Mavericks. The company is also a provider of other equipment, including traditional fitness machines and supplies.
X-Force: The final company on the list is from Sweden, and offers a complete line of eccentric training devices. While X-Force uses weight stack loading, they add in increased resistance on the eccentric portion of their lifts. The extensive line includes over a dozen different machines, all targeting muscle groups for an approach to fitness similar to Nautilus from decades ago. The company provides customized options like color choice and includes business opportunities like licensing options.Look at the science and functionality of equipment before buying any resistance training technology. Click To Tweet
The market will likely have some surprise new players down the road, as technology evolves within all sports training, rehabilitation, and fitness equipment. More innovations in design, as well as advancements in research, will make all of the current options more valuable due to education and awareness.
How to Invest Smarter
Buying a resistance system, or a fleet of systems, is one of the most expensive investments a professional team, college, or even hospital must decide on. Next to medical imaging and other major purchases, the most demanding decision will be the resistance machines. The market is now growing faster, with new options and iterations of old standbys, and we can expect more choices and more advancements in the space in the future. It is essential that you always look at the science and functionality of equipment before buying any resistance training technology.