A brief history of telemetry - measuring movement

I’m switching back to biomechanics this week for a quick history lesson on tools for measuring human movement. The inspiration for this week’s Tech Corner came about yesterday evening during our rowing club’s weekly summer ‘Fight Night’ (i.e. randomized boat lineups going for a speedy side-by-side race down the Thames). Post-race I was chatting with a member / coach who is colloquially known in the wider British rowing community as ‘Telemetry* Steve’. He previously worked for the Great Britain National Rowing Team (GB Rowing) and is a hands-on biomechanist who has seen human performance tech evolve over the decades, so we had a great conversation about where biomechanics has been and where it’s going (with a sidetrack into low Earth orbit satellites, but that’s a topic for another Tech Corner). Much of our conversation centered around motion capture systems and balancing measurement precision with the why of what you’re measuring. 

But let’s start at the beginning. I’ll skip the earliest work in human mechanics that relied on dissection and observation (see: the ancient Egyptians, Hippocrates, da Vinci, Galileo, and Borelli) and we’ll pick up with the advent of motion capture in 1878 by Eadweard Muybridge (funded by Leland Stanford, yes, that Stanford) who used a line of cameras firing in rapid succession to analyze movement. Movement analysis took off with the acceleration in camera technology, and the two fields remain closely tied. Building off of Muybridge’s work, Étienne-Jules Marey developed a “photographic rifle” in 1882 and controlled the surrounding conditions to improve accuracy in measuring motion - he used a black, gridded background and had subjects wear a bodysuit with dots and lines demarking the segments of the body, much like the reflective marker systems we use in gait labs today. The earliest version of the modern force plate was invented by Jules Amar around 1918 and used primarily for lower limb prosthetic development, and the schematics for the first true force plate were published by Herbert Elftman in Science in 1938. The earliest work in electromyography (measuring muscle firing) began in the 1920s. Swiss scientist, Richard Scherb, was among the first to link the neurological world with gait mechanics - he was one of the first to examine neuromuscular control, and invented possibly the first treadmill to be able to examine patients’ gait mechanics while remaining in-place. 

Motion analysis through the ages

The biomechanics labs of today use a combination of all this technology; climate-controlled, white rooms with arrays of high-frame rate video cameras, embedded force plates, pressure pads, and even split-belt, force-sensing treadmills to capture each foot’s impact separately. Research participants and athletes wear an array of sensors on-skin as well; reflective stickers or “markers” that translate body segments to computer visualizations with high precision, electromyographic sensors to measure muscle firing, and physiological monitors like heart rate bands. All of this is great for lab work, but these systems are big, expensive, and really only suited for controlled laboratory environments. The data they capture is highly precise and goes towards answering research questions to further our understanding of the building blocks of human motion (next time you turn around a corner, take a moment to think about the level of coordination that requires - what muscles are firing, where are your feet positioned, how have you shifted your weight, what are your arms doing - but don’t trip!). Outside of the research world, motion capture has also seen massive innovation through the movie industry’s pursuit of bridging the real world with CGI. Advances in computer vision technology and unmarked motion analysis are opening up new realms of motion capture in the “real world” (primary use-case: security), but still struggle with camera positioning, lighting, and bulky clothing, which obscures movement. Smart mirrors have gained some traction in the last five years in the fitness realm, allowing you to mimic movements displayed on the mirror to ensure you’re matching the exercise position. Digital physical therapy companies and telemedicine are pushing the bounds of using phone cameras to track progress in range of motion exercises during recovery. Human-machine interaction is still in its infancy. And, of course, as cameras and sensors shrink, wireless capacity improves, computational power accelerates, and bluetooth range expands, the opportunities for bringing human movement analysis outside of controlled environments opens up new doors to understanding humans and how we navigate our world, whether it’s in a racing shell out on the water or on your daily dog walk. 

Oh, and a fun note, our CTO Marcus was coached by Steve back when he was on the GB Junior Team as a teen. Sports, biomechanics, and health are never far apart 🧠

*Telemetry, broadly, is the collection of data from remote sensors. In rowing, this is a catch-all term for collecting data from sensors on the boat - typically a combination of strain gauges placed on the oarlock by each seat and sensors on the hull of the boat to track surge, boatspeed, etc.