It goes without saying that to implement Velocity Based Training in a weight room and do so accurately, technology is necessary. While velocity based training (VBT) is still a relatively young method of training, more options for VBT devices are coming onto the market each year. As we mentioned in the second post, we believe VBT should be a ubiquitous form of training. We would not have built a company around it if we did not truly believe in it as a training modality.
We also recognize that we would not be doing our due diligence as a company if we did not educate you further on all of the different VBT technology options currently available. When it comes time for you to make a purchasing decision, we want to help you make your decision with confidence that the product you have is going to serve you well in a variety of environments for years to come. The technical aspects of this post are relatively brief to ensure comprehension. At Perch, we geek out over this stuff. If you have any questions or would like to dig deeper, please reach out!
What are the different forms of VBT?
3D cameras produce images with pixels, just like any camera. However, instead of each pixel having an associated color, each pixel has an associated “depth.” The “depth” is simply how far away that object is from the camera.
The image is represented by a number of pixels. Each pixel has a corresponding “depth.” In this image above, the barbell is ~ 5.3 feet away from the camera, the lifters chest is ~3.5’ away from the camera, and the back of the platform is ~11.3’ away from the camera. If we know the angle of the camera and an object’s distance from the camera, then the object’s position in three dimensional space can be determined. We can take those 3D coordinates and calculate displacement over time. When displacement is known, barbell path, velocity, acceleration, and power output can be calculated.
Linear position transducers
Linear position transducers are the original velocity based training devices. They have been around for decades due to their simplicity, intuitive user experience, and the minimal processing power needed to sample the data. A string is attached to the object of interest, usually a barbell. The string is wrapped around a pulley which is connected to an encoder. When the string is pulled, the pulley spins, and the encoder measures the rotational displacement over time. From this information, linear velocity can be determined. A tension force of a couple of pounds is often applied to the string to ensure that during the eccentric (downward) portion of the movement, the string remains taught.
Accelerometers can be found in many consumer electronic devices. These are one of the many electronic components your FitBit uses to count your steps and it is how your phone determines its orientation. These same chips can be put on a barbell or on an athlete to measure velocity.
An accelerometer is basically a series of tiny springs put on a chip. When the accelerometer accelerates, these springs feel a force proportional to the acceleration. This force is measured and the acceleration can be calculated.
We hope this helps clarify any lingering questions you may have had about how certain technology works and provide some guidance for what form of technology may be right for you in the long term. Like we said, we geek out about this kind of stuff, so please feel free to leave any comments on the bottom and be sure to follow our RSS feed and follow us on social media channels linked below.