Abstract:
The invention pertains to a portable device comprising a housing, a display, a storage medium, at least one acceleration sensor, means for calculating an activity parameter based on the signal generated by the acceleration sensor, storing the calculated parameter in the storage medium, and showing the same in the display. The said parameter is the Physical Activity Index (PAI) or a derivative thereof.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This Application is a Section 371 National Stage Application of International Application No. PCT/EP02/04968, filed May 6, 2002 and published as WO 02/091923 A1 on Nov. 21, 2002, published in English, which claims priority to EP Application No. 01201653.1, filed May 7, 2001. 
   BACKGROUND OF THE INVENTION 
   The invention pertains to a portable device comprising a housing, a display, a storage medium, at least one acceleration sensor, means for calculating an activity parameter based on the signal generated by the acceleration, sensor, storing the calculated parameter in the storage medium, and showing the same in the display. The invention further pertains to a method of generating instructions or advice on how to increase physical activity as well as to a computer program comprising program code means for performing all the steps of the said method. 
   An example of a device as described above is known from e.g. U.S. Pat. No. 5,788,655, which relates to an exercise amount measuring device. This particular device calculates and displays total consumed calories, a remaining target calorie value, and a life activity index, which is classified into e.g. one of three ranks (I ‘light’, II ‘medium’, and III ‘a little heavy’). To calculate these parameters, gender, age, height, and weight should be inputted by means of switches on the device. 
   Similar devices are disclosed in U.S. Pat. No. 5,989,200 en European patent application EP 0 797 169 A1. 
   U.S. Pat. No. 6,135,951 and U.S. Pat. No. 5,976,083 disclose a pedometer comprising a accelerometer subsystem. This subsystem and a heart beat subsystem are sampled and a moving average of acceleration is computed at each sample time. This moving average serves as a baseline for describing the acceleration waveform of a locomotor step. 
   Nowadays, many people are aware of the importance of healthy nutrition and sufficient exercise, yet appear unable to accomplish the same. 
   It is an object of the present invention to provide a device which stimulates (daily) physical activity through relatively uncomplicated and user-friendly means. 
   To this end, the device according to the invention is characterised in accordance with claim  1 . 
   To this end, the device according to the invention is characterized in that the said parameter is the Physical Activity Index (PAI) or a derivative thereof. It is preferred that the PAI or a derivative thereof is calculated by multiplying an average of a processed signal or samples of a signal of the acceleration sensor with at least one constant. 
   It was surprisingly found that the PAI can be established readily, because the relation between the PAI and a processed signal or samples of a signal of the acceleration sensor is substantially linear. 
   For instance, PAI can be established by subtracting an offset from the processed signals or sample and multiplying the result with a constant. Such a constant is preferably determined by measuring the oxygen consumption of several subjects. Personal data of a user, such as gender, age, height, and weight, need not be inputted thus further enabling straightforward construction and enhancing ease of use. Also, the PAI is universal in that e.g. a PAI of 1.5 indicates a sedentary lifestyle independent of personal data, i.e. for a woman in her early twenties and a middle-aged man alike. Thus, suitable instructions or advice on how to increase physical activity can be readily selected based on the measured PAI and competition between e.g. colleagues or family members is being provoked. 
   It is preferred that the device comprises an input/output connector which enables the transfer of at least some of the stored information to a computer that contains or is connected or connectable to an electronic database and/or an electronic algorithm. 
   The method of generating instructions or advice according to the invention involves electronically obtaining, from an individual, the Physical Activity Index (PAI) or a derivative thereof and selecting, based on this parameter, one or more instructions or advice components from a database. It is preferred that the said parameter is downloaded by a remote server system, which selects, based on this parameter, one or more instructions or advice components from a database and wherein the selected items or a processed version thereof are subsequently uploaded. 
   The invention further pertains to a computer program comprising program code means for performing all the steps of this method. The computer program product may of course comprise both modules intended for implementation on a remote service system, e.g. located at a service provider, and modules intended for implementation on a local processing unit, such as a personal computer and/or portable computer device of some sort. 
   The Physical Activity Index (PAI), sometimes also referred to as Physical Activity Level (PAL), can be established by dividing the Total Energy Expenditure (TEE), i.e. the amount of energy that is consumed by a person during a selected period of time, e.g. a day, by the Basal Metabolic Rate (BMR), i.e. the amount of energy that is consumed by a person lying still on a bed for the same period of time. Typically, the PAI has the value of 1.0 when the person is lying on a bed, 1.5 when the person leads a sedentary life and 2.0 when the person has an active lifestyle. 
   It is noted that the TEE is roughly equal to the sum of the Activity Induced Energy Expenditure (AEE), the BMR, and the Diet Induced Energy Expenditure (DIE). The latter is usually equal to approximately 10% of the TEE. 
   Both AEE and BMR are proportional to the body weight of an individual. When compared to a relatively heavyweight person, a relatively lightweight person will consumes less energy both when in rest (BMR) and while performing a certain physical activity (AEE). In other words, the ratio of TEE to BMR, i.e. the PAI, is substantially independent of body weight. In this respect, the PAI and its derivatives differ from indices derived directly from AEE, such as joule or calorie consumption or an index proportional to such consumption. The latter indices require individual data (gender, age, height, and weight), whereas the device according to the present invention does not require such data. 
   An example of a preferred derivative of the PAI is the ratio of AEE to BMR, preferably multiplied by 100. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be explained with reference to the drawings in which a preferred device and method according to the present invention are schematically depicted. 
       FIGS. 1A to 1C  show respectively a front, rear and side view of a portable device according to the present invention. 
       FIGS. 2A and 2B  show a cradle for receiving the device according to  FIG. 1B . 
       FIG. 3  is a block diagram of electrical circuitry for use in the device according the invention. 
       FIG. 4  is a block diagram of exemplary electrical circuitry for use in the device according to the invention. 
       FIG. 5  is a flowchart of a website where the method according to the invention has been implemented. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A to 1C  show an exemplary embodiment of the device according to the present invention, which embodiment will be referred to as activity monitor  1 . The activity monitor  1  comprises a injection moulded housing  2  of a thermoplastic material such as PBT, a Liquid Crystal Display (LCD)  3 , and four buttons  4  to  7 . The rear side of the monitor comprises a bayonet catch  8  engaging a clip  9  for attaching the monitor  1  to an item of clothing and a cavity for accommodating a battery, which cavity is closed by means of a cover  10 . It further comprises three I/O connectors, in this case butt contacts  11 ,  11 ′,  11 ″ which, upon placing the monitor in a complementary cradle, e.g. a docking station  12  shown in  FIGS. 2A and 2B , contact three connectors  13 ,  13 ′,  13 ″ in the docking station  12  and enable the transfer of information, e.g. by means of an RS-232 protocol, between the monitor  1  and a computer to which the docking station  12  is connected. 
   The LCD  3  features the time, the numerical value of the Physical Activity Index (PAI) averaged over one or more selectable periods of time, and a segmented bar to graphically display the PAI within a specific range, e.g. from 1.0 to 3.0, in a number of discrete steps, e.g. of 0.1. 
   Instead of PAI, derivatives of PAI, such as (PAI−1)×100 or, if the Diet Induced Energy Expenditure (DIE) is to be excluded, (0,9×PAI−1)×100, can be employed. When using these particular derivatives, a value of 0 means that the user has been at rest (at least for the selected period of time for establishing PAI), whereas a value of e.g. 100 respectively 90 indicates an active lifestyle. 
   Buttons  4  to  7  serve to display and adjust time (respectively button  4  and buttons  5 / 6 ) and switch between displaying the PAI over e.g. the last day and the last week (button  7 ). 
     FIG. 3  shows a block diagram of an electrical circuitry for use in the activity monitor  1 . The circuitry in this example comprises a single one-dimensional accelerometer  14 , e.g. a so-called uniaxial piezo-electric accelerometer, which registers body movement of a wearer of the monitor  1  in the longitudinal direction or the antero-posterior and longitudinal directions. To achieve the latter, the accelerometer  14  is positioned at an angle of approximately 45 degrees to a horizontal position (as shown in  FIGS. 1A and 1B ) of the monitor  1 . The aforementioned clip  9  in  FIG. 1C  facilitates attachment of the monitor  1  to e.g. the belt of a wearer in such a way as to ensure a substantially horizontal position during most of the time, especially when the wearer is standing upright. As a matter of course, it is also possible to employ e.g. three sensors  14  (as depicted by dotted lines). 
   The accelerometer  14  generates, dependent on the movements of a wearer, which typically occur in a frequency range from 0.5 to 16 Hz and with an amplitude of less than 5G, an analogous signal, e.g. a voltage fluctuating in a range from 0 mV to 10 mV. This signal is subsequently amplified by means of amplification circuitry  15  and converted to a digital sequence of numbers by means of an A/D converter  16  with a sample frequency of e.g. 32 Hz. A dedicated microprocessor  17  calculates the average of the absolute value of the acceleration data over e.g. the last day and the last week. To obtain the PAI the average is multiplied by a metabolic factor reflecting the average oxygen consumption of relatively large number of experimental subjects and a sensor calibration factor. 
   Thus, to calculate the average value of the PAI over a certain period of time, e.g. a day, the signal can be processed e.g. as follows. The absolute value of the signal, which fluctuates within the said range of from 0 mV to 10 mV, is amplified by an amplification factor and sampled by the A/D converter  16 , which then generates a sample value e.g. an integer in a range from 0 to 255. Subsequently, the average of the sample values is calculated and multiplied by a metabolic factor, which can be established by comparing the said running average with true PAI values obtained by measuring oxygen consumption in one or more subjects in a manner which is known in itself. It is further preferred to employ a calibration factor to compensate for variations specific to the sensor in hand. For piezo-electric sensors variations were found to be ±20% and, accordingly, the calibration factor is preferably in a range from 0.8 to 1.2. 
   The microprocessor  17  stores the calculated PAIs in a memory  18 , such as a random access memory chip, and shows the information, selected by the wearer by means of the appropriate button  4 , in the display  3 . 
     FIG. 4  comprises an advantageous embodiment, wherein the circuitry comprises a rectifier  19  which comprises four diodes and an operational amplifier and is connected to the output of the amplifier  15 . An integrator  20 , which comprises a capacitor circuit, is connected to the output of the rectifier  19  and accumulates the analogous signal from the same. Instead of sampling the acceleration at a relatively high rate of e.g. 32 Hz, one can now reduce this rate to e.g. 1 Hz and, accordingly, significantly lower the power consumption of the activity monitor  1  and extend battery-life. A further advantage resides in that the PAI can be established with a high accuracy even when an low accuracy A/D converter (e.g. 8 bits) is being used. 
   Although the activity monitor  1  can be used as a stand-alone entity, which provides its user with accurate information of his or her activity, either relative to past activity of the user himself or relative to that of other people e.g. by means of the table or chart reflecting typical PAIs for specific persons (in terms of e.g. profession, sport, age, gender etc.), it is preferably used in conjunction with a personal computer (PC) and/or a remote computer, e.g. a server system. In that case, the user can compare his or her PAI with that of numerous other users and automatically select instructions or advice components from a database or calculate a new PAI goal by means of an algorithm. 
   To this end, the docking station  12  is connected to a PC or a remote server system in which software has been installed which preferably recognises the presence of the activity monitor in a known manner and performs a number of actions, e.g. download a 32-bit unique identification code, download last docking date, download PAI values of e.g. the last months, synchronise the clock of the activity monitor  1  and that of the PC or server system, and upload the present docking date. 
   A flowchart of a preferred website, which is installed on the said server system and which can be accessed via the Internet by the user with a web browser, such as Microsoft Explorer or Netscape Navigator or similar (future) means, is depicted in  FIG. 5  and comprises a home page  0 . 0 . This home page  0 . 0  shows several menus, which provide access to subpages of the website concerning, inter alia, the host, products of the host, health issues, registration, and login. The remainder of the home page  0 . 0  may comprise news items, advertisements, pictures, and the like. 
   A personal coach page  1 . 0  forms the kernel of the website. This page  1 . 0  can be accessed via a registration page  1 . 1  or login pages  1 . 8  and  1 . 9 . The former page  1 . 1  comprises an electronic form for gathering information from users of the activity monitor  1  who visit the website for the first time. Such information may comprise the name, address, city, country, weight, height, age, gender, and weight goal, and will be used by the personal coach page  1 . 0  to generate instructions and personalised advice. The registration page  1 . 1  further provides a username and password, which enables users to by-pass registration page  1 . 1  and enter the personal coach page  1 . 0  directly through login pages  1 . 8  and  1 . 9 , and links the username information to the aforementioned unique address code. During login, the system compares the downloaded ID to the ID in the server so as to provided automatic login. The last docking date and most recent PAI values are used to update the database. 
   The personal goals of a user of the activity monitor  1  in terms of a desired activity level and a desired weight are calculated on a personal goals page  1 . 7 . Such calculations can be based on the personal data of the customer, e.g., weight, height, age, and gender, as well as on other personal parameters that can be changed and/or updated on a preferences page  1 . 4  and/or on the average PAI of the first week and/or a numerical parameter representing the motivation of the customer and determined by means if a questionnaire page  1 . 6 . Upon approval of the user, the calculated goals are set to be reached at the end of a coaching period of e.g. six months. During this period, the personal coach page  1 . 0  provides information concerning the personal history of the user in terms of activity and body weight and advice comprising suggestions on a preferred PAI selected on selector page  1 . 5  and activities required to reach the set personal goals, e.g. half an hour of walking every day or 5 km running every day. 
   Finally, the website comprises a links page  2 . 0  containing links to interesting pages that can help reach the personal goals, such a as a link to go to a page containing recipes which support a healthy lifestyle, a link to a service providing direct access to an instructor or dietician, and a link containing information on regional activities. If a goal is reached, the personal coach page  1 . 0  may start another page, which shows a message congratulating the user or sends an actual congratulations post card to the users&#39; address. A special printer on the system could do this automatically. 
   The invention is not restricted to the above described embodiments which can be varied in a number of ways within the scope of the claims. For instance, the display device can be equipped with a rechargeable battery or even means for generating energy, such as a (piezo)electric generator which converts movement into electrical energy.