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RFID Fitness Tracking System

Our present goal as of fall quarter, 2004, is to create an RFID based fitness tracking

system that can be used to count and record athlete laps, lap times, energy expenditures, and

heart rate. This system is to be incorporated into MSOE’s Kern Center running track. In this

first quarter of 2004, an exhaustive literature search was performed with the goal of deciding

which features we are to incorporate into our project and developing a general idea of what our

project will do. Six specific areas of research were addressed: medical/clinical foundations with

an emphasis on underlying physiological and pathological issues associated with the product;

discipline-specific literature covering all important areas of the product (medical,biological,

etc.); existing and related commercially-available product literature; engineering and technical

aspects of the product; patents related to existing and related products; and conference

proceedings covering aspects of the product. The results of the literature searches in all of these

areas will be briefly summarized along with basic ideas of our product and how it relates to the

literature found.

Engineering and Technical Aspects of the Products

The basis of this fitness tracking system is the RFID technology it incorporates. The

technology itself has been around for a while, but has only recently gained attention as an

extremely versatile automatic identification solution. The RFID system is a relatively simple

technology consisting of three components: an antenna or coil, a transceiver with a decoder

(reader), and a transponder (RF tag) containing an integrated circuit that can be programmed

with unique information. The antennas can be built into various shapes and sizes in order to

accommodate the function of the system. They are usually built into the reader and are designed

according to their function (built into a door frame for sensing objects with a tag passing through

the door, for example). The reader, usually fixed-mounted, emits EM radio waves that are

detected by an RFID tag. The tag then transmits its own signal back to the reader where the

signal is decoded and sent to a computer for processing. The significance of this technology is

that RFID allows the automatic identification of any number of hidden tags from various

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distances. This is not possible with more current automatic identification systems used to day

such as bar codes.

There are a variety of RFID tags, and each type of tag has unique characteristics that

make it more suitable for different applications. Generally, RFID tags can be divided into two

groups: active and passive. Passive tags do not require an internal battery, and therefore must

reflect or absorb a small amount of energy from the reader’s signal to generate its own signal. In

order for it to absorb enough power to generate a signal, the reader must produce a large amount

of power. The tag can only produce a signal when in the reader’s range, and the reader can only

receive the tag’s signal when it is in the tag’s range. Because of this, the range of these types of

tags is usually less than three meters. Also, because of this limited range, passive RFID tags

cannot have continuous sensor ability. The data produced by any sensors will only be able to be

transferred when the tag is within the reader’s range. Also, because of the small amount of

power available to the tag, it can only transfer small amounts of data (128 bytes). The advantage

of these tags is that they are cheap and have an almost indefinite life.

The active version of the RFID tag is much more versatile than its passive counterpart,

but is also more expensive and has a shorter life. This type of tag has its own built in battery and

is able to be continuously powered on its own. Because of this, the reader signal need not be

nearly as strong. Also, the tag can produce a much larger signal which results in a much larger

range of 100 or more meters. The continuous power of these tags also allows them to

continuously monitor and record sensor data, and gives them the ability to utilize date/time

stamps that can be used to record sensor events. This is especially important to the

determination of lap times in our project. With the larger amount of available power, large

read/write data storage (about 128 kb) results in the possibility of sophisticated data processing.

Because of the advantages of active RFID tags, they appear to be more suited for the project we

are pursuing.

Besides considering the type of tag used in our system, the frequency of the EM signal is

also important. Different frequencies have different characteristics including range, cost, and

functionality that are important to different types of RFID systems. For areas with many large

solid obstructions, lower frequency waves are best. They can travel around objects better, but

travel shorter distances. They also have slower reading speeds and lower cost. Higher frequency

waves can travel large distances, but must have a clear line of site from the tag to the reader

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because they do not diffract as well as lower frequency waves. They have faster reading speeds

which make them better suited for processing larger amounts of data, but they are also more

costly than the lower frequency type systems.

Countless numbers of uses for RFID technology have been discovered, and its potential

has only recently been realized. The basic areas of RFID use today include transportation and

logistics, manufacturing and processing, and security. The technology has found its use in such

large manufacturing companies as Ford where the tags are used to identify what specifications

such as color and add-ons are to be placed on mini-vans. Walmart has also realized the potential

in RFID and has mandated that each of its top 100 suppliers incorporate RFID tags in each of

their boxes/cases. One small company has developed a system of computer security combining

RFID and biometrics. In this system, a person must log into a computer using his/her

fingerprint, and the computer automatically logs out if an RFID tag that the person is wearing

falls out of the computer’s range. These are only but a few of the uses found for RFID. With a

decrease in RFID tag prices and with the development of RFID standards, the technology is

expected to explode in 2010.

The use of RFID to monitor running times has been employed in events such as the

Seattle Marathon, but these devices have been used mainly to monitor each runner’s progress

and start/finish times. One specific device, the ChampionChip, uses RFID technology for this

purpose. In the ChampionChip system, a passive RFID tag is placed inside a device that may be

attached to the runner’s shoelaces or is placed in an ankle brace. The antenna is incorporated

into a mat that extends the width of the track. The antenna is connected to a battery powered

transceiver that sends the runner’s data to a central computer for processing times. Although this

device is effective for monitoring single passes across the mat, no devices have been found that

use the technology to count laps and measure lap times.

Also, technology is available that is able to monitor heart rate, energy expenditures, and

speed/distance (some also do lap times). These devices, called heart rate monitors, consist of

chest-straps and wristwatches. The chest-strap uses electrodes to monitor a runner’s heart rate,

and then transfers this data through the air to the wristwatch where the heat rate is displayed.

Energy expenditures are calculated with the heart rate data and user-entered body weight. The

speed and distance of the runner are calculated in different ways in different HRMs. One type

that is made by Timex uses GPS while another type made by Polar uses a sensing device that is

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placed on the ankle. However, no heart rate monitors have been found that utilize RFID

technology.

Our current concept of the RFID fitness-tracking system consists of ideas from both the

ChampionChip technology, and current heart rate monitor technology. Our system will utilize

an antenna implanted into a running mat, battery powered transceiver, and passive ankle-brace-

mounted RFID tag just as is used in the devices used in the large marathons. However, our

system will allow a runner to pass the same running mat (located near the entrance of the Kern

Center) as many times as he/she wishes, each time recording the lap time and number of laps.

Each time the runner passes the mat, data will be sent by the reader to a central computer for

processing. Also, a wristwatch device containing an active RFID tag and integrated circuit will

have electrodes capable of monitoring heart rate just as current heart rate monitors do. However,

this information will be sent to the central computer for processing by the active RFID tag that is

capable of sending data over the full range of the track. The central computer will use the lap

counts/times and HR data to calculate energy expenditures, and will form a personal database

used for performance trending for the person using the track. Whenever the person runs on the

track, he/she can log into the computer and load his/her personal settings and store new data for

each run. Blood pressure monitors and security capabilities are other features we are currently

undecided about employing into the device.

Existing Products

Radio frequency identification, or RFID, technology has been around since WWII, but recent

advances in technology have brought many new uses for this formerly military product. (Booth-

Thomas) One such civilian use is in tracking and identifying objects electronically. By

attaching an RFID tag to a person, the person could be tracked as they pass a certain point. This

technology lends itself to tracking athletes as they move around a track. By having an external

timer linked to the RFID reader, the time elapsed between one reading and another can be

determined, giving the lap time for the athlete. Since RFID tags can identify each individual

person uniquely, the lap times for that person can be recorded in a database and, combined with

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some separately collected data, other biometric data such as total energy expended can be

determined.

There are several products on the market already that do time athletic events. However, most of

these products use low frequency tags (134 kHz), and are therefore limited to the range that they

can be used at. (RFID Race Timing Systems) Most systems have an operational range of less

than 3 feet. This means that the easiest way to accomplish the reading of the RFID tags as they

pass is to have the reader on the ground, and the tags mounted on a part of the athletes near to the

ground, most commonly on the shoes or an ankle strap. (ChampionChip) This existing

technology is also limited to low resolution timing, most to within a second or so. (RFID Race

Timing Systems) For lap timing at the Kern Center, where the track is 0.1 miles long, this error

amounts to about + 5 seconds per mile, or under 1.5% error in the speed calculation at a runner’s

speed of 10 miles per hour, under 0.7% error at a moderate speed of 5 miles per hour, or under

0.3% error at a slow speed of 2 miles per hour.

There are also active RFID tags, meaning tags that are powered by a battery. (RFIDtalk.com)

These tags can send more information and have a longer range than passive tags. Because of

this, an active tag could possibly be mounted on a wristband or other body part and take real-

time measurements of heart rate or other biometric data, and send those data to the database on

the run. However this would be much more expensive, and require much more technical

expertise to pull off than using a passive system. Also, the active tags have a much more limited

lifespan due to the fact that the tags’ internal power source will run low eventually.

Summary of Conference Proceedings: Concerns of RFID in Industry

Very few conference proceedings were relevant to an RFID-based lap counter. The

information from conferences indicated that not many people knew the details of RFID

technology and had many questions. Some of the concerns included whether RFID technology

would replace bar coding. For our application, it is more practical to use RFID technology rather

than bar code technology because the bar code would need to be directly pointed at the sensor

whereas an RFID tag can be received by a reader even if they are not facing one another.

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Since RFID tags do not need direct contact with the sensor businesses are concerned

about the reliability of RFID-based technology. However, a study shows that the accuracy of

RFID is 99.9% (McGraw Hill Construction Next Phase). Another concern was whether RFID

technology would affect users’ health. RFID technology has not been proved to be dangerous.

The waves emitted are on the low end of the electromagnetic spectrum. They “are no more

dangerous than the waves coming to your car radio” (RFID Journal).

An additional source of concern is that not all companies use RFID-based technology.

Since it is not widely used, people do not feel secure in applying it. RFID technology is usually

marketed towards healthcare, pharmaceutical, manufacturing, consumer packaged goods, and

retail companies (ProQuest SeeBeyond). It has been reported that RFID tags can be connected to

pulse oximeters (ProQuest Precision Dynamics)

The reason that many companies do not use RFID technology is that it is difficult to use

the technology in a closed-loop system. Company A might implement RFID technology through

a given provider. Company B might implement RFID technology through a second provider.

Companies A and B will not be able to share the technology since they went through different

vendors. Other companies do not have closed-loop systems, and information can be transferred

via RFID between companies. For a lap counter on a stationary track, a closed-loop system

would not create problems. However, if the track RFID system was integrated with a college

campus, each building would need to obtain equipment through the same vendor, so that the tags

could be received in various locations.

Another reason that RFID technology is not widely used in businesses is that it is still

relatively expensive. Each tag costs an average of 25 cents. If RFID tags were to completely

replace bar codes, certain products might cost less than their tags which would not be practical.

For our purposes, the cost of tags is not critical. Tags could be used multiple times for different

runners.

People who have decided to use RFID technology need to consider the range of

frequency that will be necessary. The frequencies of RFID tags and readers generally come in

three ranges: low, high, and ultra-high. Low frequency tags are typically used to read close

objects that contain water. Ultra high frequency tags cannot penetrate as easily as low frequency

tags. They do, however, transfer data faster and offer a better range (RFID Journal). For use on

a track, tags could be applied to shoes in order to use low frequency tags or they could be used in

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the form of a wrist band in which high or ultra-high frequency tags would need to be used. Most

marathon runners apply the RFID tags to their shoes, however, if a digital display were applied,

the tag would need to be located on the wrist to increase visibility.

Another uncertainty of RFID technology is that it will not be as affective in highly

metallic, exposed environments. Researchers are currently testing this hypothesis and have

reported that “it looks pretty good” (McGraw Hill Construction E-Construction). It has been

found that “radio waves bounce off metal and are absorbed by water at ultra-high frequencies”

(RFID Journal). This means that lower frequency tags should be used around both metal and

water.

Medical/Clinical Foundations and Discipline-Specific Literature

The Medical/Clinical Foundations for this design project were deemed to be the physiological

effects of exercise, specifically running. For our purposes, the physiological effects of exercise

were divided into the categories of heart rate, weight, blood pressure, and energy usage.

Given that the heart is responsible for pumping the blood that carries necessary oxygen to

muscles during exercise, one of the main concerns regarding the heart with exercise is the

maximum heart rate, or target heart rate. There are two main formulas for calculating the

maximum heart rate (MHR). The first suggests subtracting one’s age from 220. (Heart 2 and 1)

The second method is to use the equation MHR = 217 – (0.85*age), then for athletes under 30,

subtract 3 beats, for elite athletes 50 years old add 2 beats, and for 55+ year old elite athletes add

4 beats. (Heart 4) For aerobic exercise, the heart rate should be between 55% and 88% of MHR.

(Heart 2 and 1) One indicator of aerobic activity is ease of talking; for aerobic respiration, one

should be able to say a few words, catch one’s breath and continue speaking; for anaerobic

respiration, one experiences much difficulty attempting even just to say a few words. (Heart 1)

Furthermore, training zones have been discovered based on percentage of MHR (x%). To

calculate the heart rate for any of the training zones, the use formula:

MHR-Resting heart rate = Working heart rate

Working heart rate*x% = Z

Z + Resting heart rate = Heart rate for the desired training zone

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There are four training zones, each with specific benefits, and each at different percentages of

MHR. The first training zone is the Energy Efficient, or Recovery Zone which is for 60%-

70%MHR. Exercising within this zone develops basic endurance and aerobic capacity and

allows muscles to re-energize with glycogen while still burning fat. The second training zone is

the Aerobic Zone which is for 70%-80%MHR. Exercising within this zone develops the

cardiovascular system, improving the ability to transport oxygen to and carbon dioxide from

working muscles. Specific benefits for working within the Aerobic Zone include some fat

burning and improved aerobic capacity. The third training zone is the Anaerobic Zone which is

for 80%-90%MHR. Exercising within this zone develops the lactic acid system which is

important because through proper training, the ability to deal with lactic acid in the muscles will

increase. Also when working out in this zone, glycogen in the muscles is the main source of

energy instead of fat. The final training zone is the Red Line Zone which is for 90%-

100%MHR. Exercising within this zone is only recommended for the extremely physically fit

and is reserved for interval running only. Working within this zone helps train fast twitch

muscles and develops speed. (Heart 3)

The next physiological effect of exercising researched was the effect on weight. When

discussing weight with regard to exercise, fat is generally referred to as a body fat percentage.

Body fat percentage is simply the percent of total body weight that is fatty tissue. When calorie

intake is greater than the combination of calories needed for maintenance and for the current

activity, the excess calories are stored as fat in the body. Therefore, it is possible to lose excess

fat by burning more calories than one is consuming, thus causing the fat to be broken down to

supply energy for the activity. Before considering weight loss with exercise, the realization must

first be made that some fat is essential for normal healthy physiological functioning. This

essential fat consists of fat stored in bone marrow, in the heart, lungs, liver, spleen, kidneys,

intestines, muscles and lipid-rich tissues of the central nervous system. Additionally, females

require an extra 9% of fat for childbearing/hormonal reasons. Another important fact to note is

that the areas in which each individual stores fat are dictated by heredity, and exercising a

particular part of the body will not necessarily remove any fat from that part of the body. What

exercising specific areas does is to tighten the muscle underneath the fat causing the general

appearance to improve, but the actual fat used for energy during the exercise most likely will be

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taken from other areas of the body. (Weight 1) Exercise is a great way to lose excess fat by

burning calories. Burning approximately 4,000 calories is equivalent to losing 1 lb of fat.

(Weight 1) The best MHR range to maintain for maximum fat oxidation is between 68% and

79% MHR. (Weight 2) This is based on the fact that the body burns a higher percentage of

calories from fat when involved in lower intensity cardiovascular exercise. However, the body

does burn a higher total number of calories at higher intensities, which may be more important to

an individual trying to lose weight. (Weight 3) The key point to remember is that exercising at a

higher intensity for the same amount of time as exercising at a lower intensity will yield more

calories total burned at the higher intensity, but an identical number of calories from fat burned

for both the higher and lower intensity workouts. (Weight 2)

The next physiological effect of exercising studied was blood pressure. Blood pressure is

defined as “The force of blood exerted on the inside walls of blood vessels. Blood pressure is

expressed as a ratio (ex. 120/80). The first number is the systolic pressure, or the pressure when

the heart pushes blood out into the arteries. The second number is the diastolic pressure, or the

pressure when the heart rests.” (BP 4) The systolic blood pressure is the larger blood pressure

because it is measured when the ventricles of the heart are contracting whereas the diastolic

pressure is lower because it is measured when the heart is filling with blood. (BP 3) Normal

blood pressure is considered to be 120/80 mmHg. A blood pressure of 140/90 mmHg is

considered borderline hypertension (high blood pressure): 141/90 mmHg is considered moderate

to high risk; and a blood pressure of 160/95 mmHg is considered high risk for hypertension. (BP

1) Risks involved with hypertension include heart attacks and strokes. (BP 2) Tulane University

recently conducted research showing that aerobic exercise helps control blood pressure. Results

showed a decrease in blood pressure regardless of age, weight, or what blood pressure was

before the person started to exercise. Additionally, the extent of blood pressure drop was

consistent regardless of the type of exercise performed. The average systolic pressure reduction

observed was 3.8 mmHg, and the average diastolic pressure reduction observed was 2.58 mmHg.

Reducing blood pressure can reduce the risk of cardiovascular disease, stroke, and all other

negative effects of hypertension. (BP 5)

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As a final point, the physiological energy usage required for exercise was studied. A few

basic points must be known before a discussion on energy usage can begin. First of all,

Adenosine Triphosphate (ATP) is the complex chemical formed from energy released from food

and it powers all bodily functions. ATP is stored in all cells, especially muscles, and the

breakdown of ATP forms ADP (Adenosine Diphosphate) and energy. Next, Phosphate-Creatine

(PC) is a chemical stored in muscle that breaks down to help manufacture ATP. ADP combines

with PC to form ATP. Finally, lactic acid (LA) is a metabolite of the lactic acid system. Lactic

acid is formed from the incomplete breakdown of glucose. Excessive lactate production

contributes to fatigue, and protons released during lactate production restrict further

performance. Another key metabolic fact is that during aerobic running, ATP is synthesized

from food, mainly proteins, fats and carbohydrates (glycogen). Aerobic respiration therefore is

the main energy source for endurance activities. When exercising, muscles first obtain energy by

producing ATP using glucose stored in the blood stream and the breakdown of glycogen stored

in the muscles. When those sources run out, ATP is produced through the complete oxidation of

carbohydrates or free fatty acids in the mitochondria. (Energy 2) The breakdown of glucose

produces pyruvic acid and ATP. In aerobic conditions, the pyruvic acid is converted to CO2,

H2O, and ATP. In anaerobic conditions, however, the pyruvic acid is converted to lactic acid.

When oxygen becomes available again, the lactic acid will convert to pyruvic acid which then

converts to CO2, H2O, and ATP. One Hydrogen ion is formed for each Lactate molecule formed

during anaerobic respiration. The presence of Hydrogen ions makes the muscles acidic which

halts muscle function, slows down enzyme activity (& therefore the breakdown of glucose),

aggravates nerve endings causing pain, and increases irritation of the central nervous system.

Lactic acid usually starts to build up in muscles when one is exercising above 85%-90% of

his/her MHR. (Energy 4)

During exercise, increased oxygen is needed for the muscles. Consequentially, blood

vessels in the muscles dialate and blood flow increases to meet the increased need for oxygen.

Excess Post-Exercise Oxygen Consumption, (EPOC) is the oxygen consumed after exercise

stops that is in excess of a pre-exercise baseline level. For low intensity, aerobic exercise, half of

the total EPOC occurs within 30 seconds of exercising stopping, and oxygen uptake usually

returns to the pre-exercise level in several minutes. For strenuous exercise (especially if the

exercise is accompanied by an increase in blood lactate and/or body temperature), EPOC may

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require 24 hours or more before oxygen uptake returns to the pre-exercise level. (Energy 6)

Another concept to consider regarding increased need for oxygen during exercise is maximum

VO2. VO2 max is the maximum amount of oxygen in mL one can use in one minute per kg of

body weight. For male athletes, VO2 max is usually about 3.5 liters/minute, and for female

athletes, VO2 max is usually about 2.7 liters/minute. VO2 max can be increased with proper

training. Also, it is possible to estimate exercise intensity as a % of VO2 max based on training

heart rate (% MHR) using the equation : (Energy 7)

%MHR = 0.64* % VO2 max + 37

Finally, different intensities and types of exercises will have differing physiological

effects. “Endurance exercises (such as running) result in cardiovascular and respiratory changes

that cause skeletal muscles to receive better supplies of oxygen and carbohydrates but do not

contribute to muscle mass.” (Energy 5) Also, for high intensity workouts, carbohydrates are the

main source of energy which means that this type of workout is only sustainable for short periods

of time because of the limits of the amount of glycogen that can be stored in the muscles.

Finally, for low intensity workouts, fat is the main source of energy, so this type of exercise can

be sustained for long periods of time due to the large stores of fat in the human body. The

following chart shows the relationship between exercise intensity (%MHR) and the energy

source (carbohydrate vs. fat): (Energy 3)

Intensity % MHR % Carbohydrate % Fat

65 - 70 40 60

70 - 75 50 50

75 - 80 65 35

80 - 85 80 20

85 - 90 90 10

90 - 95 95 5

100 100 0

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Additionally, the number of calories burned per minute can be calculated based on body mass for

walking on a firm level surface such as a road, track or grass: (Energy 1)

Next, the number of calories burned per minute can be calculated based on body mass for

running on a firm level surface such as a road, track or grass: (Energy 1)

Speed Body Mass (Kg)

km/hr 55 65 75 85 95

8 7.1 8.3 9.4 10.7 11.8

9 8.1 9.8 11.0 12.6 14.4

10 9.1 10.8 12.2 13.6 15.3

11 10.2 11.8 13.1 14.7 16.6

12 11.2 12.8 14.1 15.6 17.6

13 12.1 13.8 15.0 17.0 18.9

14 13.3 15.0 16.1 17.9 19.9

15 14.3 15.9 17.0 18.8 20.8

16 15.4 17.0 18.1 19.9 21.9

Speed Body Mass

Kg 36 45 54 64 73 82 91

mph km/hr Lb 80 100 120 140 160 180 200

2.0 3.22 1.9 2.2 2.6 2.9 3.2 3.5 3.8

2.5 4.02 2.3 2.7 3.1 3.5 3.8 4.2 4.5

3.0 4.83 2.7 3.1 3.6 4.0 4.4 4.8 5.3

3.5 5.63 3.1 3.6 4.2 4.6 5.0 5.4 61

4.0 6.44 3.5 4.1 4.7 5.2 5.8 6.4 7.0

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Finally due to the rate of energy consumption, when walking speed exceeds 8 km/hr (5mph), it is

much more energy efficient to run rather than walk. (Energy 1)