Activity measuring device

Abstract

Activity measuring device for detecting the activity of a test subject, wherein the device can be worn on the body of the test subject and the device has at least one acceleration sensor, characterized in that the activity measuring device is arranged in a belt buckle (2) of a belt (3) that can be attached to the body of the test subject and has acceleration sensors (10, 10') for detecting acceleration in all three mutually orthogonal spatial directions.

Description

[0001] The invention relates to an activity measuring device for detecting the activity of a subject and further to a method for detecting the activity of a subject.

[0002] State of the art: WO 2003 / 055 389 A1, DE 31 09 026 C2, DE 297 21 632 U1, DE 35 13 400 A1, US 6 506 152 B1, US 5 263 491 A, US 7 062 225 B2

[0003] Such devices are known, for example, as so-called pedometers, which can be attached to the body of a test subject. During the subject's running or walking movement, the acceleration forces acting on the body are recorded via an acceleration sensor of the body-mounted pedometer, and the number of steps completed is counted. The determined step count represents a measure of the subject's physical activity. Such pedometers are used as sports or recreational devices and have only a one-dimensional acceleration sensor for detecting accelerations in the vertical direction.

[0004] However, such a device has only limited use in the medical-clinical field for determining the degree of physical disability of patients, in particular patients suffering from multiple sclerosis (hereinafter abbreviated to MS patients), since with this state of the art technology only dynamic types of movement such as walking and jogging can be recorded in an undifferentiated manner, whereas for MS patients with a more severe degree of disability, continuous walking or even jogging is only possible to a limited extent or not at all and the types of movement are restricted to more static states such as lying, sitting and standing, as can be seen from Table 1 below, which shows the so-called "Hauser Ambulation Index" for the medical classification of multiple sclerosis patients, with the scale of this index ranging from level 0 to 9. Low values correspond to no or only slight disability, while high values correspond to a severe degree of disability. Table 1 0 No symptoms, fully active 1 Normal walking behavior, but the patient reports difficulties in sports and other demanding activities 2 Unusual gait or temporarily disturbed balance; the unusual gait is noticed by relatives and friends, takes a maximum of 10 seconds to walk 8 m 3 Can walk unaided, needs 20 seconds or less to walk 8 m 4 Requires one-sided support (crutch or stick), needs a maximum of 20 seconds for 8 m 5 Requires support on both sides (crutches, sticks or walking aid) but needs more than 20 seconds for 8 m 6 Requires bilateral support and takes more than 20 seconds to walk 8m, can occasionally use a wheelchair 7 Walking is limited to a few steps with bilateral support, can no longer walk 8 m, can use a wheelchair for most activities 8 Confined to a wheelchair, can still move it himself 9 Confined to a wheelchair, can no longer move it himself

[0005] In addition to the Hauser Ambulation Index summarized in Table 1, there are other measurement systems for classifying the degree of disability of MS patients. The EDSS (Expanded Disability Status Scale) is mentioned here as an example. The existence of several such independent classification systems already demonstrates the weaknesses of such a classification caused by subjectivity.

[0006] Currently, an inpatient hospital stay with the treating physician is required for ongoing monitoring of whether and to what extent a prescribed therapy leads to an improvement or deterioration in an MS patient's health. During these regularly scheduled inpatient stays, a medical examination is conducted, and on this basis, the patient is assigned a degree of disability. Naturally, the examination results depend on the patient's and the examining physician's current state of mind (particularly influenced by the so-called "white coat" effect) and thus on non-objective criteria. Consequently, the assessment of the effectiveness of medication used in MS therapy is also subject to non-objective criteria, with the result that timely correction of the chosen therapeutic approach cannot be made early enough.

[0007] The examination and classification of patients' degree of disability or activity plays a special role in drug development and clinical trials to test their efficacy. Naturally, the degree of physical disability is assessed at certain intervals during the course of a drug being tested. Due to the fluctuation range of the measurement results described above, a reasonable assessment of efficacy is currently virtually impossible.

[0008] The invention is therefore based on the object of creating an activity measuring device and a method with which, in particular for determining the degree of disability of MS patients, in addition to dynamic forms of movement such as walking, jogging or running, more static states such as lying, sitting and standing can be recorded according to objective criteria and corresponding activity measures of the patient to be examined can be determined.

[0009] From a device-technical perspective, the problem is solved in that the activity measuring device is arranged on and / or in a belt buckle of a belt that can be attached to the subject's body and has acceleration sensors for detecting acceleration in all three orthogonal spatial directions. Depending on the design of the belt buckle, the activity measuring device can be arranged or formed on the buckle (front, back, top, bottom, or side). The activity measuring device can also be arranged in the buckle, preferably with appropriate miniaturization of the circuit elements (e.g., as an ASIC). In this case, a design or integration of the activity measuring device in the buckle is preferred.

[0010] By designing the activity measuring device in the belt buckle, this creates a practical way of easily attaching the device to a test subject. In the event of repairs, the belt can be simply removed, or just the belt buckle can be removed and sent in for repair or maintenance. Another advantage is that the telemetry device designed as a belt does not require regular washing. In addition, the arrangement on or in the belt buckle is also advantageous in that the very frequently occurring movements of the extremities (such as arms, legs or head), which are not characteristic for an objective assessment of the degree of disability of an MS patient, are recorded or suppressed as little as possible by this arrangement, or only slightly impair the measurement.It is also advantageous that the belt buckle is positioned close to the patient's center of gravity when the belt is worn as intended. The belt buckle's orientation (forward and centered) when worn as intended also makes it easy to computationally record and process the accelerations detected by the acceleration sensors. The tripod of the spatial directions sensed by the acceleration sensors is preferably oriented such that one of the spatial directions is perpendicular to the buckle, i.e., in the forward direction when walking (straight ahead), jogging, or running. Another spatial direction preferably runs parallel to the vertical.

[0011] Particularly advantageously, the activity measuring device according to the invention can identify different forms of movement through the three-dimensional recording of acceleration forces acting on the body. These forms naturally differ from one another due to characteristic movement sequences with corresponding acceleration forces. Since the various forms of movement each have different energy requirements and thus different activity levels, the device according to the invention enables a differentiated assessment of the patient's physical activity, thus providing the physician involved in the therapy with a means of assessing the progress and success of the therapy based on objective criteria, regardless of the patient's potentially fluctuating daily condition.A potentially negative course of therapy in MS patients, for example due to the administration of unsuitable medication, can thus be identified at an early stage based on corresponding measurement results, so that the use of a negatively acting medication can be discontinued promptly, whereby risks for the patient can be reduced and costs resulting from expensive but unsuitable medication can be contained.

[0012] A preferred embodiment of the activity measuring device according to the invention for the optimal recording of the acceleration forces occurring in the various forms of movement consists in that the activity measuring device arranged in the belt buckle is designed in such a way that it can be attached near the body's center of gravity of the subject.

[0013] According to an advantageous embodiment of the invention, the activity measuring device transmits the recorded measurement data via a radio link to a central server, preferably located in an external data-protected service center or the medical treatment center, so that the telemetered data can be directly viewed and evaluated by medical staff. This means that the attending physician is no longer exclusively dependent on the examinations performed during inpatient hospital stays when assessing the patient's physical condition, provided the device according to the invention is also used as intended in the patient's everyday life.

[0014] For this purpose, the activity measuring device can be electrically coupled to a mobile phone that can also be worn on the belt and is designed as a PDA according to a preferred embodiment of the invention, in such a way that data transmission can be established between the activity measuring device and the mobile phone. The activity measuring device has an electrical connecting cable that can be electrically connected to a device interface of the mobile phone. The connecting cable can then provide both data transmission between the device and the mobile phone and, by tapping into the battery cells provided in the mobile phone, power for the device. The measurement data recorded by the activity measuring device can be transmitted to the mobile phone via the device interface and from there transmitted to the external server, for example, via a GPRS or UMTS radio connection.

[0015] A metrologically advantageous embodiment of the activity measuring device according to the invention provides that a one-dimensionally operating acceleration sensor for detecting acceleration forces acting along the vertical spatial direction and a two-dimensionally operating acceleration sensor for detecting acceleration forces acting orthogonally thereto are provided as acceleration sensors of the activity measuring device.

[0016] A useful development of the invention consists in that a belt section adjacent to the belt buckle on the cable side has a hook-and-loop fastener for receiving the connecting cable, which largely prevents accidental tearing or loosening of the connecting cable and thus increases the security of data transmission. Furthermore, a microprocessor is provided in the activity measuring device to control both the measurement data acquisition and the data transmission. Using a control program implemented in the microprocessor, the activity measuring device acquires and transmits the measurement data at a sampling frequency of the order of 100 Hz. This sampling frequency has proven particularly suitable for resolving even fast movement sequences on the order of a hundredth of a second. The system according to the invention comprises the activity measuring device, the belt, the mobile phone, and preferably also the server.

[0017] From a procedural point of view, the task is solved by continuously measuring the body accelerations underlying the current body activity of the subject to be examined in all three mutually orthogonal spatial directions and determining a current state of movement from this.

[0018] To do this, a distinction is first made between static and dynamic movement states to determine the test subject's current state of movement. In the static movement states, a distinction is made between sitting, standing and lying down, and in the dynamic movement states, a distinction is made between walking and jogging. To differentiate between static and dynamic movement states, the maximum and minimum of a series of measurements from successive acceleration measurements determined in a spatial axis direction are calculated and the difference between the maximum and minimum is compared with a threshold value. Maximum and minimum are understood to be a suitable maximum or minimum value of the measurement series. To avoid falsification by outliers, for example, an average of a predetermined number (e.g. ten) of maxima in the measurement series can be used as the maximum.If fewer maxima than the predetermined number occur, correspondingly fewer maxima are used for averaging. Accordingly, an average value from a predetermined number (e.g. ten) of minima in the series of measurements can be used as the minimum. If fewer minima than the predetermined number occur, correspondingly fewer minima are used for averaging. A movement of the patient is then detected if the inequality max - min > δ is satisfied in at least one spatial axis direction, ) where max or min is the maximum or minimum value from a series of measurements of successive acceleration measurements determined in this spatial axis direction and δ is a threshold value.

[0019] In the case of motion detection, to distinguish between walking and jogging, the mean difference from the mean of measured values belonging to a series of measurements is determined for each spatial axis direction, and the resulting difference from the mean in the corresponding spatial axis direction is compared with an assigned threshold value. In contrast, to distinguish between lying, standing, and sitting motion states, the mean of the corresponding series of measurements is determined for each spatial axis direction, and the determined mean values are compared with assigned threshold values. By determining the respective duration and, if applicable, step frequency for each identified movement type, a corresponding activity measure can be determined.

[0020] The invention, as well as further features, objects, advantages, and possible applications thereof, will be explained in more detail below with reference to a description of preferred embodiments with reference to the accompanying drawings. In the drawings, the same or similar reference numerals designate the same or corresponding elements. All described and / or illustrated features, individually or in any meaningful combination, constitute the subject matter of the present invention, regardless of their summary in the claims or their reference back to them. The drawings show, in a highly schematic representation: Fig.1 shows a belt for fastening to the body of a patient in a plan view, wherein the belt can be arranged around the waist of the patient and has a belt buckle with an activity measuring device accommodated therein, which is in signal connection with a mobile phone attachable to the belt; Fig. 2 a partial view of the belt from behind in the area of the belt buckle, wherein the activity measuring device according to the invention is integrated as a box in the belt buckle; Fig. 3 is a block diagram of a circuit accommodated in the box of the activity measuring device according to the invention, which circuit comprises a microprocessor, a quartz oscillator for generating the processor clock frequency of the microprocessor, a one-dimensional and a two-dimensional acceleration sensor for detecting acceleration forces; and Fig.4 a flowchart showing the essential process steps taking place in the external server or the activity measuring device for determining a current movement state of the patient.

[0021] In Fig.1, the activity measuring device 1 according to the invention is arranged in a belt buckle 2 of a belt 3 that can preferably be worn around the patient's waist. Near the belt buckle 2 containing the activity measuring device 1, a belt area with a case for holding a mobile phone 4, which can also be designed as a PDA ("personal digital assistant"), is arranged. Measurement data acquired by the activity measuring device 1 can be transmitted to the mobile phone 4 via a connecting cable 5, which is electrically connected at one end to the activity measuring device 1 and at the other end to a device interface of the mobile phone or PDA 4. The multi-core connecting cable 5 is also electrically coupled to the internal power supply of the PDA 4 and thus additionally serves to supply power to the activity measuring device 1.The connecting cable 5 runs between the belt buckle 2 and the belt area to which the mobile phone 4 is attached, and the belt 3 has a hook and loop fastener 6 on its surface, which serves to guide or hold the connecting cable 5 and for this purpose has a closure seam running in the longitudinal direction of the belt, so that the connecting cable can be inserted into the hook and loop fastener when the closure seam is open and is received in the hook and loop fastener in a sleeve-like manner when the closure seam is then closed.

[0022] The acceleration measurement data acquired by the device are transmitted via the connecting cable 5 to the mobile phone or PDA 4, and are then transmitted from the mobile phone 4 via a mobile network to an external server 7 for evaluation. This server 7 can be located in a medical service center, so that the data transmitted by the activity measurement device 1 can be retrieved at any time by the medical staff via an evaluation program implemented in the server 7.

[0023] In Fig.2 shows the activity measuring device 1 accommodated in the belt buckle 2. The belt buckle 2 is a substantially planar or flat, rectangular element made of metal or plastic in the exemplary embodiment. The activity measuring device 1 is arranged as a box or case or housing 14 on the back or inside of the belt buckle 2. The connecting cable 5 to the PDA 4 is led out of the box 14 and extends along the outer surface ( Fig. 1) of the adjacent belt area 3. At the opposite end of the belt buckle 2, a pin 12 is provided, onto which the free end of the belt 3 can be hooked by means of one or more holes 13 provided there (for adjusting the belt circumference) in order to close the belt 3.

[0024] Fig.Figure 3 shows a block diagram of a circuit 15 provided in box 14 of the activity measuring device 1 according to the invention. In the exemplary embodiment, a microprocessor or microcontroller 8, whose processor clock frequency is generated by a quartz crystal 9, is electrically connected to a one-dimensional and a two-dimensional acceleration sensor 10, 10', and records and processes the acceleration forces continuously measured by these acceleration sensors 10, 10' on the body of the patient to be examined in all three spatial dimensions. To facilitate the calibration of the acceleration sensors 10, 10', the belt is applied to the patient's body such that the belt buckle with the device 1 accommodated therein rests against the body, so that a measuring axis of the two-dimensional acceleration sensor 10' almost coincides with the forward movement direction of the body.The acceleration sensors 10, 10' are arranged and connected in such a way that the one-dimensionally operating sensor 10 measures acceleration forces acting along the vertical, and the two-dimensionally operating sensor 10' measures the acceleration forces acting orthogonally thereto along the two remaining spatial axes of a Cartesian coordinate system. The acceleration measurement values x recorded in analog form by the acceleration sensors 10, 10' are digitized via AD converters (not shown) and converted into an interval 0 ≤ x ≤ 255, whereby this interval corresponds, for example, to a measuring range of (-2g) to (+2g) and g is the acceleration due to gravity, so that a digitized measurement value x from the interval 0 ≤ x ≤ 255 can be converted into units of acceleration due to gravity g according to (4 / 256)*x*g-2g. AThe program implemented in the microcontroller 8 controls, on the one hand, the measured value acquisition and thus the interaction between acceleration sensors 10, 10', the AD converters and the microprocessor 8, whereby a timer or time generator of the microprocessor 8, which is dependent on the processor clock frequency, controls the use and length of the measuring cycles, and, on the other hand, the processing of the measured data in the microprocessor 8 and their transmission via an interface of the microprocessor 8 to the PDA 4. The recorded measured values are provided with a time stamp for the current time and date, and thus the patient's activity can be recorded over the entire daily routine.

[0025] The method according to the invention with its essential process steps is shown in a flow diagram designated as a whole by 100 in Fig.4. After program start 101, a step 102 first checks whether the criteria for no movement of the patient being examined are met. For this purpose, the maximum and minimum acceleration values for each spatial direction per second are calculated based on the measured data. The difference between the maximum and minimum values is compared with a specific threshold value δ in the y-axis and z-axis directions: Max_y−Min_y≤δ Max_z−Min_z≤δ where Max_y, Max_z are the maximum and average maximum values of the measured acceleration values in the y-axis direction, and Min_y, Min_z are the minimum and average minimum values in the z-axis direction, respectively. δ is an empirically determined threshold value whose value corresponds to 20. The digital value δ=20 can be converted into a corresponding g-value according to (4 / 256)*δ*g-2g. If one of the two above inequalities is met, the presence of no movement is classified as the patient's activity measure, and the program checks in further process steps whether this immobility can be differentiated between lying, standing, or sitting.

[0026] If the test in step 102 shows that the criteria for no movement are not met, a subsequent method step 103 checks whether a movement of the patient can be detected based on the following criteria: Max_y−Min_y>δ Max_z−Min_z>δ If the respective difference between maximum and minimum in the y-axis direction or the z-axis direction exceeds the threshold value δ = 20, the criteria are met and a movement is detected.

[0027] In this case, the program goes to program step 104 and checks whether the person is jogging by applying the following criteria for jogging to the measured data: MW_Diff_MWx<γ1 MW_Diff_MWy<γ2 MW_Diff_MWz<γ3 where MW_Diff_MWx, MW_Diff_MWy, MW-Diff_MWz are the mean differences from the mean value of the accelerations in the respective axis directions x, y, z, and the values to be compared γ1 = 20, γ2 = 28, γ3 = 21 are the respective threshold values, which can be converted into a corresponding g-value as digital values according to (4 / 256)*δ*g-2g. The mean differences of the measured values a ito the mean according to the following equation 1100∑ι=1100|aι−mean| for 100 measured values. If each of the above inequalities (3a) to (3c) is satisfied, the movement state 105 of jogging is detected as the activity measure. However, if the criteria checked in process steps 103 and 104 are not met, the program classifies the movement state 106, 107 of walking and calculates a step frequency from the measured data in corresponding calculation steps 108, 109.

[0028] Following process step 102, if the criteria underlying equation (1a) or (1b) are met, the program proceeds to process step 110 and checks whether the immobility is a lying state by checking the corresponding criteria: MW_z>α11 and MW_y<α12 MW_z>α21 and MW_y<α22 MW_x>α31 and MW_y<α32 MW_x>α41 and MW_y<α42 where MW_x, MW_y, MW_z are the respective mean values of the measured data in the x-axis direction, y-axis direction and z-axis direction and with the respective assigned threshold values α 11 =47, α 12 = 42, α 21 = -47, α 22 = 12, α 31 = -43, α 32 = 12, α 41 = 43, α 42 = 12. If inequality (4a) is satisfied, the examined person is lying in a supine position; if inequality (4b) is satisfied, the person is lying in a prone position; if inequality (4c) is satisfied, the person is lying on their left side; and if inequality (4d) is satisfied, the person is lying on their right side. In these four cases (4a) to (4d), the program detects the static state of motion or rest state 111 of lying down.

[0029] However, if the test in this step leads to a negative result, the program proceeds to step 112, where it is checked whether the person is standing. For this purpose, the following inequality combination is used: MW_z<β1 and MW_y−MW_z≥β2 checked. If this combination of inequalities is satisfied for the threshold values β1 = 2 and β2 = -68 from the interval 0 ≤ x ≤ 255, the person is in the static motion state 113 of standing. If the result of process step 112 is negative, the program classifies the static motion state 114 of sitting.

[0030] For each identified movement type, the program calculates an activity measure based on the determined step frequency and duration of the identified movement type. This measure depends on physical parameters, namely the patient's height and weight, and the energy requirements characteristic of the movement type. Furthermore, a total activity measure is calculated for the entire measurement duration, which corresponds to the average of the individual activity measures weighted by the respective movement durations.

[0031] In addition, with the device and the method according to the invention, it is possible to detect limping or stumbling due to the three-dimensional detection of the acceleration forces in the case of the walking movement form by comparing the respective step durations for the left and right-sided movement components of walking and determining an asymmetry factor therefrom, which indicates the presence of limping or stumbling when a specific threshold value is exceeded.

[0032] The invention has been explained in more detail above with reference to preferred embodiments thereof. However, it is obvious to a person skilled in the art that various modifications and variations can be made without departing from the spirit of the invention.

Claims

[1] Activity measuring device for detecting the activity of a subject, wherein the device can be attached to the body of the subject in a wearable manner, and the device has at least one acceleration sensor, characterized by that the activity measuring device is arranged in a belt buckle (2) of a belt (3) which can be attached to the body of the subject and has acceleration sensors (10, 10') for detecting acceleration in all three spatial directions which are orthogonal to one another. [2] Activity measuring device according to claim 1, characterized by that the activity measuring device (1) arranged in the belt buckle (2) is designed such that it can be attached near the body's center of gravity of the subject. [3] Activity measuring device according to claim 1 or 2, characterized by that the activity measuring device (1) telemeters the recorded measurement data via a radio connection to a central server (7). [4] Activity measuring device according to claim 3, characterized by that the activity measuring device can be electrically coupled to a mobile telephone (4) which can also be attached to the belt (3) in such a way that data transmission can be established between the activity measuring device (1) and the mobile telephone (4). [5] Activity measuring device according to claim 4, characterized by that the activity measuring device (1) has an electrical connecting cable (5) which can be electrically connected to a device interface of the mobile telephone (4). [6] Activity measuring device according to one of claims 3 to 5, characterized by that the measurement data recorded by the activity measuring device (1) can be transmitted to the mobile phone (4) via a device interface of the mobile phone (4) and from there can be transmitted to the external server (7) via a radio connection. [7] Activity measuring device according to one of claims 1 to 6, characterized bythat a one-dimensionally operating acceleration sensor (10) for detecting acceleration forces acting along the vertical spatial direction and a two-dimensionally operating acceleration sensor (10') for detecting acceleration forces acting orthogonally thereto are provided as acceleration sensors (10, 10') of the activity measuring device (1). [8] Activity measuring device according to one of claims 5 to 7, characterized by that a belt section adjacent to the belt buckle (2) on the cable side has a Velcro fastener (6) for receiving the connecting cable (5). [9] Activity measuring device according to one of claims 1 to 8, characterized by that a microprocessor (8) is provided in the activity measuring device (1) both for controlling the measurement data acquisition and for data transmission. [10] Activity measuring device according to one of claims 1 to 9, characterized bythat the activity measuring device (1) records and transmits the measurement data with a sampling frequency of the order of 100 Hz. [11] Method for detecting the activity of a subject with an activity measuring device according to one of the preceding claims, characterized by that the body accelerations underlying the current body activity of the subject to be examined are continuously measured in all three mutually orthogonal spatial directions and a current state of movement is determined from this. [12] Method according to claim 11, characterized by that in order to determine the current movement state of the subject, a distinction is made between static and dynamic movement states. [13] Method according to claim 12, characterized by that in the static movement states a distinction is made between sitting, standing and lying and in the dynamic movement states a distinction is made between walking and jogging. [14] Method according to claim 12, characterized by that in order to distinguish between static and dynamic states of motion, the maximum and minimum of a series of measurements of successive acceleration measurements determined in a spatial axis direction are calculated and the difference between the maximum and minimum is compared with a threshold value. [15] Method according to one of claims 11 to 14, characterized by that a movement of the subject is detected if the inequality max - min > δ is satisfied in at least one spatial axis direction, where max or min is the maximum value or minimum value from a series of measurements of successive acceleration measurements determined in this spatial axis direction and δ is a threshold value. [16] Method according to one of claims 11 to 15, characterized bythat in order to distinguish between the movement states of walking and jogging, the mean difference from the mean value of measured values belonging to a series of measurements is determined for each spatial axis direction and the difference from the mean value thus determined in the corresponding spatial axis direction is compared with a respectively assigned threshold value. [17] Method according to one of claims 11 to 15, characterized by that in order to distinguish between the movement states of lying, standing and sitting, the mean value of the corresponding series of measurements is determined for each spatial axis direction and the mean values determined in each case are compared with assigned threshold values. [18] System comprising activity measuring device, belt, mobile phone and preferably the server according to one of claims 1 to 10.

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