In the second installment of this series on technology in sport, I addressed how coaches can use technology to time various aspects of performance to better enhance training and analysis of competition and training performances. As I mentioned in that installment, timing is fundamental to the sport of track and field and can be similarly useful in the training and testing of athletes in other sports.The same can be true for measurement. While measuring displacement (height or horizontal movement) are the most commonly used forms of measurement in the sport, I’m going to look at some means outside of the standby measuring tape that can be used. In a later installment I’ll look in to how coaches can use technological gadgets to measure kinetic and kinematic qualities not typically available to coaches.
- Height with Light Beams: I’ve seen some laser gates that have been used for throwing events that consist of hundreds of light beams vertically stacked perpendicular to the direction of the throw. When the implement disrupts one of the beams it acts in much the same way as the spinning ‘rulers’ do on a Vertec machine and coordinate data that can be used to provide the height of release. These can also be used to determine release angle. I’ve only seen one functioning unit in action but this type of thing could be very useful for coaches in the throws who are looking to provide immediate quantitative feedback. I would also love to one day see this setup used in the vertical jumps to determine how high someone is actually jumping and clearing without regard to the specific accuracy / location of their peak height relative to the bar. I suspect, if these had been part of the measurement system for the past 20 years we’d have likely seen pole vault world records in excess of 20’6 from Sergey Bubka and 8’2 from Soto.
- Distance with Light Beams: The most common method of measuring distance is with a standard scaling device like a measuring tape or yard stick. These have their limitations in both ease of use and accuracy (temperature can change the scale of the measuring device and produce false distances). There are however alternatives that use laser technology to determine distance. One could string together a series of light beams closely bunched (similar to what I mentioned above) and determine stride length, and flight phases in the triple jump or even the flight / stride length in throwing events. The Optojump device that I mentioned in my previous post is capable of doing this with a little help from the included software. Measuring distance can also be used lasers and a triangulation method. In fact, the same triangulation methods that are employed in construction and surveying are now commonplace tools for measuring the long throws at large international meets. These seem to speed up the measuring process but the accuracy of the system is very dependent on the levelness of the field and the pre-meet calibration and setup of the system. I’m not sure if these would have much practical use for training, especially considering the cost (~$8k).
- Linear Scaling using Motion Analysis Software: Most of the latest consumer motion analysis software on the market now (like Dartfish, Sports Motion, Silicon Coach and Kinovea) have built in linear scaling that allows you to estimate linear measurements by scaling them against an object of known length in the same plane. This can be useful for very quick estimations but in my experience the accuracy is VERY dependent on the initial camera setup and the colinearity of the distance being measured with the calibration distance. It is likewise imperative that both the scaling device and the estimated measurement are perpendicular to the camera angle. This means that the camera must be stationary for the entire performance and perpendicular to the direction of movement. Any deviations from these guidelines can make the scaling almost completely worthless. Ninety percent of the time when coaches use this tool it’s giving numbers that are completely worthless because the above guidelines are violated.
- Panned Scaling:It is difficult, though possible, to do accurate measurements with a panning camera. This requires either a specially outfitted camera tripod or software that permits panned 3D transformations. For most coaches this is outside of the realm of practicality to use this type of measurement but if it’s available in the research community now (and it has been for about a decade) then it’s only a matter of time before it shows up as an option for coaches.
- 3D Scaling using DLT or NLT procedure: Using video data from 2 or more cameras and methods known as direct linear transformation (DLT) or non-linear transformation (NLT) it is possible to turn 2D spatial data in to 3D spatial data, thus eliminating perspective and planar errors. This is largely considered the gold standard for spatial measurements in movement analysis and research data and the results of this method are readily available to coaches in research papers. In fact, with proper equipment, a good camera setup, and the required software, many coaches (or officials) could actually perform these spatial calibration procedures themselves which could produce measurements in 3 dimensions. To give this some relevance, think of the triple jumper who takes off in the center of the board and lands to the far right (or left) side of the pit. The current method of measuring these performances leaves something to be desired but this could theoretically be resolved by calibrating the 3D space from the takeoff board to the end of the pit. It could also mean that after the initial spatial calibration, jump and short throws distances could be immediately determined without need for a measuring tape. You’d also be able to get instant feedback on things like peak height during throws or jumps which might have both fan and coach appeal.
- Height with Force or Piezoelectric Platforms: This one is essentially using timing of the flight phase to figure out height of a jump through a fairly simple projectile motion equation. These can be quite accurate for vertical jump tests and research studies have found them to be as valid and reliable as other forms of measuring vertical jumping ability.
- Distance with GPS:
- Distance with Accelerometers:
- Distance with Web Applications: Due to the work of Google, MapQuest, Geoportail and other satellite based mapping and their easily integrated APIs, many web applications exist that allow you to do fairly accurate estimations of run distances over a mile on city streets and park trails. If you’re a runner that does frequent tempo running or extended distance running you may want to check out sites like MapMyRun, G-Map Pedometer, FavoriteRun, or other sites like them to take much of the guess work out of tracking your mileage. These map routing apps likely won’t be accurate enough to gauge off-track runs of under 1 mile with any accuracy.
Most people are familiar with GPS units in cars now but there use in running is only just starting to catch on. These devices determine your instantaneous position on the earth via interaction between your device and 4 satellites. The devices that can be used in athletics typically come in the form of a wrist watch however there are other solutions which are worn on the back that are being used by Rugby, Soccer, Football, and even Hockey teams to determine how far players are running / skating in a game. This makes for an interesting way of quantifying the physiological load of team based sports because the more advanced units and monitoring systems can determine peak and average velocities (a gauge of intensity) as well as total distance (a gauge of volume).
These things have been around forever. Most people know them as pedometers. Those in use today aren’t the same as the pager-looking things your parents wore on their waists though. Today’s accelerometers are MUCH smaller and considerably more accurate than their predecessors. Accelerometers track the vertical oscillations of your body while in flight and support and make guestimations of your stride length between the phases of support. Old school pedometers basically just knew up (mid-stance through apex of the flight phase) and down (apex of flight phase through peak amortization). These older devices didn’t accurately register changes in stride length which can lead to large inaccuracies if the athlete becomes fatigued or is running over varying surfaces (hills, trails, different surfaces). The newer accelerometer based pedometers that are seen in gadgets like the Nike + seem to be a little more advanced. I’ve tested my own Nike + device as well as some of my athlete’s against known distances on different terrains and under different temperature conditions. My general thoughts are that if they are calibrated before use that they can provide good enough data about pace and distance to cover distances as short as 300m reliably. This can be convenient if you want to do something like a tempo workout off the track without measuring out distances with a measuring wheel. It also means you could basically just go out on the street or in the woods and do your interval repeats without having to double back to ensure accuracy and consistency.
If you have any questions or comments, or can think of any other tech-based means of measuring height and distance, please share your thoughts in the forum.