FITRODYNE, COMPUTER BASED SYSTEM FOR STRENGTH DIAGNOSTIC
AND FEEDBACK MONITORING OF WEIGHT TRAINING

FiTROdyne is a system working on the simple principle of mechanics saying that actual force is a product of acceleration and mass.

(Since the velocity and acceleration change during the lifting exercise, so does the actual force and also the other variables, e.g. power. Therefor, lifting the same weight in a more dynamic way with pronounced acceleration produces a higher peak force than a slowly performed lift. Also counter movement exercise produces much higher peaks than lift from rest position. Differences in parameters like force and power (which may be well quantified by this system) due to different physiological mechanisms involved in control of muscle contraction. One may, therefore, expect also different adaptation patterns.)

Acceleration of vertical movements (above or below g) is being obtained by derivation of vertical velocity, measured by highly precise analogue device mechanically coupled with a barbell or weights of an exercise machine (also complex lifting movement like clean and jerk or snatch can be monitored). In addition, power is being calculated as a product of force and velocity, the actual position by integration of velocity.

However, to be able to carry out these calculation, you have to enter mass of barbell or weights on the exercise machine first.

Technically the system consists of 2 functional components, a sensor and an electronic unit, stored in a small box of about 28x13x7,5 cm.

The sensor unit contains a precise analog velocity sensor and an infrared impulse sensor with resolution of 3 mm. Both are mechanically coupled with the reel. While pulling the tether out of the reel, this rotates and velocity is being measured. Back movement of the reel is guaranteed by string producing force of about 2 N. The tether can be pulled out to the distance of about 2.5 meter.

The other end of the tether is to be connected by means of a small hook either to the barbell axis or to the weights of the weight exercise machine. The attachment is easy and does not take more than several seconds.

The electronic box, contains the signal modification part, a 12 bit AD convertor and an acoustic device for differential signalization of reaching preset lower and upper positions during exercise (range of motion) as well as decrease of power under preset level. Use of signalization is optional, you can switch it on or off in a software setup.

The electronic box communicates with the computer by means of COM1. You can use any IBM-compatible computer (even 286), clock speed does not play any role. The only requirement is a VGA card and a VGA monitor (color or monochrome).

Comprehensive software allows you to collect, calculate and on-line display the basic biomechanical parameters involved with the weight exercise. Of course you can store the data for further analyses of single repetitions or the whole set.

During the diagnostic measurement a movement of symbolic barbell axis and graph of any of derived parameter, i.e. velocity, force, power or acceleration. After each repetition you receive a summary of mean and peak data in digital form, separately for eccentric and concentric phase.

Typical test routine consists of a set of full effort repetitions from lower weights (e.g. 20 kg in bench press) with steps of 10 kg up to the maximum. There is a special menu driven software routine for this procedure. From such a test series you can obtain the individual force-velocity and power-velocity curves allowing you to assess the force and power at the velocities close to the velocities at sports specific movements. Such an approach provides a more sensible method for detection of specific adaptation changes due to various forms of weight training (e.g. slow or fast) than simple 1RM.

Should you wish to analyze the single repetition you may assign any of the parameters (force, power, velocity, acceleration, position and time) to either the X, Y1 or Y2 axis. Scaling, i.e. definition of minimum, maximum and step of parameter on all 3 axis is available. In addition, while moving the left and right cursors, the digital values of parameters on the X, Y1 and Y2 axis are being displayed. Also integral and mean values between both cursors are being actualized.

Such an analysis may for example demonstrate nicely the differences in time course of force, power and velocity between repetitions performed in slow or fast way, with or without counter movement, etc.

There is also a software routine available allowing you to use the system as a feedback for weight training. After each repetition you can see the decline of power output if performed in an all-out way. Drop under preset critical level will be indicated visually as well as by an acoustic signal. The patterns can be very different according to individual morphological dispositions (FT/ST muscle fiber ratio). In this way you can obtain some information about the quality of strength training stimuli. Also this information can be stored for the subsequent analyses.

The calibration of the system is software driven and basically very simple. This is due to simultaneous registration of velocity and distance. According to instructions on the screen you only have to pull the tether the defined distance between 50 and 100 cm (system calibrates the distance) and then to pull at least 50 cm with medium velocity (system calibrates the velocity). The calibration is in fact stable, a recalibration is necessary only if you use an exercise machine, in which - due to other than 1:1 levering - the weights are moved with different velocity than axis at which force is being applied. In this case you move the axis while performing calibration.