Measuring Work Output From Anaerobic Weightlifting Designed, Built, and Tested by David Wolney Prof. Julie Ellis- Advisor Prof. Chris Scott- Client

Professor Chris Scott of the Department of Exercise, Health, and Sport Sciences needed a means of measuring work output done by a weightlifter. How much work am I doing? Prof. Scott hopes to find a correlation between work output and calories burned. Work Calories

Clarifying the problem: what, exactly is required for measurement Actual work done during a set is zero. Only positive displacement is counted. Force is the force required to overcome gravity and lift the weight. The average force during the lift is the force required to hold position, this is equal to the weight being lifted. The only required measurement is distance.

Using a digital rotary encoder to measure the cable travel Weight The Smith machine, like many weight machines, utilizes a cable that is attached to the moving weight. Pulley Counterweight Another pulley wheel with an encoder is attached to the machine to measure the cable travel

Rotary encoder theory of operation Radius=0.5 cm 3.14 cm (0.785 cm in this example) An encoder disk has alternating light and dark wedges and two photodetectors. This example disk has 4 light-dark transitions per revolution Left-US Digital Encoder, Above-signal from encoder; A and B are in quadrature. This arrangement allows for determination of direction as well as improved resolution

The Intel 8051 microcontroller provides the interface. The 8051’s serial port allows for detailed data of the lift on a PC The 8051 Development Board from PJRC works well in this application Counterweight Encoder Wheel Weight lifted The display gives the distance lifted in “clicks” Work Done: Lots of clicks The encoder wheel attaches to the Smith machine

The processor counts transitions Signal A is monitored for a high-low transition When A goes high, B is checked to determine direction Absolute count is incremented or decremented, as applicable Positive distance count is incremented if direction is up The absolute count is regularly sent to the serial port and the positive count is sent to the LCD display

A PC can collect the data from the serial port so that it can be processed Raw data is collected. The data contains distances and, implicitly, time A detailed analysis of the lift can be done. Knowing distance, time, and weight allows determination of many different statistics of the lift. Work, power, velocity, acceleration and others can be calculated

The first prototype has been installed and some preliminary tests have been performed. Client Measuring Wheel Smith Machine Controller The wheel installed

Some refinements were necessitated by the preliminary tests. 8-bit counters free up the processor A keypad allows entry of weights Reading in “CLICKS” Prof. Scott prefers to have more information on the display of the device. He found the detailed computer analysis less useful for his purposes, so efforts were focused away from the computer interface

The revised system better fits the client’s needs. External 8-bit counters count the encoder clicks and free the processor for other tasks The display gives more information Work Done and Seconds Clock The encoder wheel attaches to the Smith machine The PC is treated as an optional component A keypad allows entry of weights