Frequently Asked Questions
Q: Can I use Innervations software such as BMS, KMS, Pacer, and InnerBalance on an Apple computer?
Q: Where are the sound files for the Pacer Performance System stored and how can I add my own customised sound files?
A: On most windows computers the sound files will be stored in a folder named C:\Users\Public\Documents\Pacer Performance System\SoundFiles. If the software has been installed in a different location then simply search on one of the sound file names such as “Walk.wav” and this should provide you with the full folder path. To add sound files to this folder record the voice command or other sound using Windows “Sound Recorder” or program with similar sound recording capabilities and then save the resulting file to the SoundFiles folder. All sound files must be located in this folder otherwise the Pacer Performance System software will not be able to access them. To select the sound file that you wish to be played at the start of a particular stage enter the file name in the Program Designer exactly as it appears in the SoundFiles folder.
Q: Who do I contact to order hardware such as force plates and timing systems?
A: Fitness Technology manufactures and supplies the following equipment that can be used by Innervations software systems:
- 400S Performance Force Plate
- 200S Clinical Force Plate
- FT700 Power Cage and Magnetic Brake System
- Olympic Training Platform
- Portable Squat Rack
- Timing lights, contact mats and switches for Kinematic Measurement System
Ballistic Measurement System
Q: Does the linear position transducer (LPT) measure horizontal and vertical displacement?
A: The LPT constantly measures the straight-line distance (displacement) between the transducer and the end of the cable. It does not separate the horizontal and vertical components of this displacement but rather provides the resultant. For the majority of test movements such as squat, jump squat, bench press and most weight lifting movements such as snatch, clean and jerk the horizontal displacement of the attachment point is small relative to the vertical displacement and so is generally ignored.
Q: What are the formulas for calculation of jump height from flight time versus peak velocity? Which is better to use in which circumstances?
A: The formulae for calculating jump height from flight time versus peak velocity are as follows:
Flight time: Jump Height = 9.81 * (flight time) ^ 2 / 8
Peak Velocity: Jump Height = peak velocity ^ 2 / (2 * 9.81)
^ indicates to the power of so in other words squared.
Jump height calculated from velocity is an estimate of the height of rise of the center of mass and so may be a better indication of actual jump performance. However, accurate velocity data from measurement of ground reaction force requires the initial conditions to be well established i.e. athlete standing upright on force plate and completely still for at least 1 second of data collection before initiating the jump.
Flight time can be influenced by body position at takeoff and landing and so may not be truly reflective of actual jump height. However, many other measurement systems use flight time to calculate jump height so this is included in the BMS for comparison.
Q: Why do some people calculate Reactive Strength Index (RSI) using flight time / contact time and others use jump height / contact time?
A: I prefer to use flight time / contact time. Both FT and CT can be measured directly and are very accurate and it is clear what these physical quantities are. RSI can also be expressed as jump height / contact time. In most instances flight time is used to estimate jump height based on the formula:
Jump Height = 9.81 * (flight time) ^ 2 / 8
It is important to note that this is only an estimate of jump height because take-off and landing position effect flight time and so jump height varies accordingly. In terms of RSI it makes little difference which calculation is used because the correlation between the two methods is perfect because it is a straight mathematical derivation. When testing using a force plate it is better to use actual jump height based on ground reaction force calculations and then divide by contact time as this provides an even more valid RSI measure. Having said this, a simple contact mat system and using RSI = flight /contact works well and has been used extensively for diagnosis and programming as well as research.
Q: The force plate does not maintain the correct body mass measurement during use following calibration. At times, it seems to be quite extreme. How do we fix this?
A: System should read body mass to within 0.1kg or roughly 1N of force consistently. Check that the plate is correctly zeroed prior to measurement. Check the plate is level and on a firm surface such as concrete rather than carpet or sprung wood floor. Refer to the 400S Manual page 5 & page 7 item 5 + the instructions on the FT700 Instructional Footage here is the direct link. http://www.fittech.com.au/videos/ft700_poscal_512Kbps.wmv
Q: The braking system seems to have a baseline level of operation that is constantly there. How do we eliminate it?
A: The brake has tension due to the spring return system which is around 100N of force. It is fairly constant across the range of movement due to the spring and cam arrangement but the force does decrease slightly from full extension to retraction. It is advised to only use the braking system for training and use free weight only for testing. If the research involves examining the effect of the brake then this is OK as force is measured directly at the ground so upward brake force is included.
Q: If the braking cannot be reduced to zero, how do we quantify this baseline? If using the force plate, would it be correct to say that we will have the correct mass information when the weight is un-racked? If we are not using the force plate, how do we quantify the contribution of the braking force?
A: We advise to not use the brake during testing and only attach for training when the load is too high to tolerate without eccentric assistance. However, even when using the brake, the force plate will reflect the ground reaction force and this will include the body weight, brake force and acceleration force components. To get an actual load with the brake attached we just “weigh” the person plus bar using the force plate.
Q: Even more important than just how do we quantify it while in use, is how do we control it? Our initial experience with the braking system was that the control, especially the external manual one, had a much smaller range and resolution than we had anticipated. Our expectation had been that the percentage control of the braking force would be a percentage of a total load value that we would enter. It now seems to us that the settings may instead be percentages of the braking force that the system can provide. Is this the case?
A: The brake should provide infinite adjustment from 10 to 150kg whether on manual or computer control. Video Explanation: http://www.fittech.com.au/videos/ft700_brakesetup512Kbps.wmv
(also see next Question).
Q: Therefore, if we are dealing with the same absolute force from the breaking system at a particular setting regardless of the load on the bar, we need to know from you what are those absolute values…what is the lowest one and what is the highest one, and what is the smallest change in braking that can truly be controlled within that range?
A: We hang various loads from the brake to determine this. In our experience this is in the range 10 -150kg corresponding to brake OFF and FULL ON.
Q: What guidelines/advice can you provide on cutoff frequency for filtering each of the three variables to produce a smooth representative signal?
A: Initially go with the default settings of 0, 16 and 10 Hz for displacement, velocity and acceleration. If the signals are too noisy then consider lowering the velocity and/or acceleration cutoffs. Filter cutoff will impact measured variables such as peak velocity and power so it is important not to change the settings between repeat tests.
Q: Can the 30-ms default epoch be changed when calculating maximum RFD (N/s)?
A: No it can’t be changed but it is a good suggestion and we will add this to the software in coming updates.
Q: Does the Time to Peak Force calculation begin only at the start of the period enclosed by the two cursors on the graph or does it always use the same initiation time point? I will check to see if the cursor position affects it but thought you might have a quick answer for me.
A: Yes – time to peak force is from cursor line 1 to the highest peak between the two cursors.
Q: In the information you provide, it is stated: “For a squat or bench press, set the zero at the bottom of the movement. The zero point is not as crucial for movements that do not involve a flight phase.”…Do you have to use a lighter weight ahead of the set to make sure the athlete can fully pause at the bottom without fatigue and assume the same “zero” depth will be used for other heavier barbell loads?
A: The zero point is not that critical except for measuring maximum and minimum height which are not commonly used variables anyway. The zero is just relative so for example, you might find it easier to set the zero for squat or bench press at the top of the ROM.
Q: When saving a training set, is there no automated process within the program to save time once the training begins (prompts based on pre-selected number of sets, athletes involved in session, date, etc.)?
A: No, not as yet but could be added in future. We will add to the list of client suggestions.
Q: How can we use the software to set up Bosco-type jump testing (e.g., total contact time versus total air time of repeat jumps)?
A: At present you would have to analyze each jump and then add the times together. We will add this to the data analysis in future releases.
Q: According to the user guide, it indicates that power in training mode is calculated (mass x 9.81 x displacement) only from the displacement transducer. How do we make sure that data from the force plate is used during training mode?
A: At present data from the force transducer is not used in the training mode as there are issues around processing the calculations fast enough in real time. We will investigate this and see what variables e.g. peak force could be added.
Q: “Eccentric Strength Test” – Need additional explanation than what is in the user guide within the options and settings table under “Configuration-Ballistic Measurement System”.
A: Eccentric Strength Test is a test specifically developed for the US Ski and Snowboard Association. It involves determining the maximum weight that the athlete can lower in a controlled manner over a 4 second period. This test is no longer available on the BMS software as it is so specific to USSA. We will remove from user guide.
Q: “Test Serial Interface” – What kind of commands are there that one can send to test the communication with the serial transducer?
A: This option only applies to the older XPV6 and RS232 transducer. This does not apply to the USB based units.
Q: Do you have any recommendations/guidelines for setting up a bench press on the force plate, when it is obviously larger than the area of the force plate?
A: Several labs have built custom benches which sit isolated on the force plate. This is the best option. However, depending on design some off the shelf benches can be isolated on the plate.
Q: Why not attach the position transducer to the athlete’s waist for barbell jump squats instead of attaching to barbell?
A: Many labs and teams do attach the transducer to the belt rather than bar. There are no strict methodologies at this time and it depends on movement, setting, athlete experience, personal preference. I would test each and see which provides more representative data. Caution re attaching to waist belt – that belt position must be secure so it can’t slip. Belt slippage causes inaccuracy data recorded re squat jumps Counter Movement Jumps etc.
Q: Please confirm if the minimum velocity occurs at the highest eccentric value?
A: The minimum velocity is the fastest velocity in the negative direction so will occur somewhere in the middle of the eccentric phase.
Q: What is “count in start” selection in “Collect and Analyze” window?
A: This provides a three second countdown to the start of data collection. This is useful when the athlete is operating the computer for testing or training. Or can be used to count the person being tested down to the start of the test.
Q: We seem to be having some problems as the results, particularly the power and displacement when using the force only are wrong. So to simplify things to understand where our problems are stemming from we have been having someone standing stationary or place a weight on the force plate and measuring the force. Again the results appear to be incorrect – a minimum displacement is recorded which is significant (-90 in some instances) and the graph appears to be very noisy. I’m not sure where the error is stemming from but when we zero force we get a peak force of around 20KN in the result window. Is this right? I would have imagined that if we zero force everything should be zero in the results window before we start the collection.
A: First off make sure the software is set to force only. There is a zero offset of around 20,000 but this is the summed Analogue to Digital count. This is normal; it has been put into the XPV7 to account for any instances when there is a tensile force on the load cells. The graph would be noisy if the person is just standing on the plate because it is auto-scaling to the maximum and minimum readings. To solve this problem we recommend you have the person perform a CMJ and then stand still. This process is shown in the following link (3MB video file). http://www.fittech.com.au/videos/ft700_cmjtest_512Kbps.wmv
Q: When “mean concentric only” box is ticked, at which point on the graph are the measurements taken from?
A: All calculations are for the period selected between the two points (vertical lines inserted on the graph). For some measures e.g. power it may not be suitable to include eccentric (negative velocity) phases in the calculation of mean values so selecting this option causes the system to only average values between the selection points during concentric phases.
Q: Is velocity calculated from the linear transducer only? (as results make no sense with the force only!). If so, why can’t we use the force plate to get Vertical velocity at take-off (and hence jump height also calculated)? (as we know the mass)
A: This depends on which option is selected to calculate data sets – displacement only (linear transducer), force only, or both. If both is selected then displacement and velocity are calculated from linear transducer data and force is measured from the force plate. If force only is selected then velocity data is calculated from force data using impulse-momentum relationship and displacement data including peak height are calculated by integrating the velocity time data.
Q: With printing from excel, I couldn’t just use selected part of graph for results (it only worked with all the data)? Any ideas? Would be good to have force by time scale on the graph, then be able to print selected part.
A: Right click on the graph and the options to copy selected section of data are displayed. The displayed data set or all data sets between the two selections points can be copied and then pasted into Excel for graphing or other analysis.
Q: Can the data be smoothed to remove noise (eg. just after take-off/landing etc.)?
A: A Fourth order Butterworth digital filter is provided for all data sets including force. Cutoffs are selected under options.
Q: I am using the BMS to analyse bench throw power, based on the below evidence this would now be inaccurate. Luckily I have access to the force plate as well, my question is would there be enough impulse from/through a bench to record meaningful ground reaction force data that can be coupled with the BMS data to give an accurate power reading?
A: Measurement of power during bench press using the BMS and linear transducer only is not as problematic as for a movement such as squat jump or power clean as you are measuring the power applied to the bar only. So depending on the level of validity that you require using the linear transducer should be sufficient. If you do have access to a force plate then measuring the force directly by placing the bench on the plate will work well. I did most of my early power research using this setup. I have attached my PhD for your reference which details these studies.
Q: Where should the (linear position transducer) LPT be attached to the barbell and will the resistance of the spring return effect the athlete’s movements?
The attachment of the LPT to the barbell should not cause any problems for the athlete even when using a very lightweight carbon fibre or wooden pole if the attachment is to the centre and the LPT is suspended above the athlete. This is the best solution. If the LPT has to be positioned on the ground then it must be placed to one side so as not to interfere with the athlete movement. When there is some minimal weight being lifted this does not create any problems because the resistance of the LPT is so small relative to the load being moved. We find that even a standard 20 kg Olympic barbell can be used with the LPT attached just lateral to the left or right hand without any interference to normal jumping, squatting, overhead lifts and weightlifting movements. For any weight less than this the LPT really needs to be mounted centrally and above the athlete.
For any movement where the athlete and resistance do not contact any surface if is preferable to use the force plate with all measures derived from the vertical ground reaction force. In this case there is no requirement to attach the LPT at all. This allows very free movement of the athlete in activities such as jumping, squatting, overhead lifts and any weightlifting movements from the hang position. This circumvents the issue of LPT placement and also makes consideration of horizontal movement irrelevant as only vertical force, impulse, power, velocity and displacement are being measured without contamination from movement in the horizontal plane.
If it is required to track barbell displacement using the LPT and horizontal movement is a concern then multiple displacement transducers can be used and the two or even three-dimensional position of the barbell determined using triangulation. In my experience this is not worth the additional effort as the error introduced due to horizontal movement of the barbell for most movements is insignificant.