SI25959A - Multi-accelerometer system and method for evaluating mechanical stress during walking and running - Google Patents

Abstract

The multi-accelerometer system and method for evaluating mechanical stress during walking and running is a system basically consisting of six three-axis accelerometers (59), a central unit (58) and software for displaying measurement results. A central unit (58) consisting of an electronics housing (5, 7, 11), a Raspberry Pi 4B computer (10), a PiJuice power supply module (8) with two batteries (6, 9), a ChronoPi time module (12), the cooling fan of the system (15), the on / off switches of the data acquisition system (13) (14) and the six visual indicators of the operation of the sensors (20, 21, 22, 23, 24, 25), the subject wears on his back or on his belt handbags. The central unit (58) is connected by cables (4) to the accelerometer sensor elements (3), which are protected by two halves of the housing (1, 2). The cables (4) are made in three lengths, which allows the placement of accelerometers on certain parts of both lower extremities (top of the foot, top of the tibia and pelvis). The system is switched on by switching the on / off switch (13), switching the data acquisition switch (14) to ON triggers the start of the measurement. The measurement is completed by switching the switch (14) to OFF, when the recording of data to the usb key, where the text file is stored, is also completed. The Telasi Preview software then performs a quick analysis of the data obtained from the measurements and graphically displays the results of all three axes (x, y and z) of all six accelerometers (59) separately in the 3x2 grid. The present invention makes it possible to capture accelerations and thus obtain data on biomechanics and loads of all joints of the lower extremities during walking and running.

Description

TITLE

Multi-accelerometer system and method for evaluating mechanical stress during walking and running

PROBLEM REMOVAL

Running is one of the basic ways of moving a person. To understand the biomechanics of running, we must first understand the course of walking. The walking cycle can be described as the sequence of movement of the lower extremities between the initial contact of the foot with the ground and the re-contact with the ground at the end of the pair cycle of two steps. This is divided into two main phases: the support phase (60% of the cycle) and the swing phase (40% of the cycle). The support phase represents the contact of the foot with the ground, while this is absent during the swing phase. When one lower limb is in the support phase, the other is in the swing phase. The change from walking to running occurs at a speed of about 2 m / s. Unlike walking, when at least one lower limb is always in contact with the ground, the running phase is shorter during running and represents less than 50% of the cycle. The higher the speed of movement, the shorter the support phase. As a result, a longer swing phase, lasting more than 50% of the entire cycle, results in a simultaneous swing phase for both lower extremities in a given part of the cycle. This is the phase we call the flight phase and separates walking from running. Although running may seem like a simple movement compared to other, more complex sports / movements, it represents high physiological and biomechanical requirements for the human body. As a result, runners often experience musculoskeletal injuries. The most common are injuries to the knees (28%), ankles or feet (26%) and shins (16%) or patellofemoral syndrome (17%), Achilles tendon tendinopathy (10%) and medial tibial stress syndrome (8%). One of the potential risk factors for injuries is incorrect running biomechanics, which occurs in as many as 80% of runners for various reasons. Based on biomechanical analyzes, many researchers in this field have suggested possible risk factors for injury, such as increased vertical load and forces acting on the tibia, increased hip or foot eversion, decreased knee mobility, and decreased preactivation of some muscles.

Nowadays, running is one of the most widespread physical / sports activities for both recreational and professional athletes. In Slovenia, more than 450 running events are held annually, such as the Three Hearts Marathon Radenci, the Istrian Marathon, the Soča Outdoor Festival, the Trojk Run, the Ljubljana Marathon and others. The number of participants is growing from year to year. For example, in 1996 the Ljubljana Marathon session was attended by 673 runners, in 2019 as many as 19,592. Due to the growing popularity of running among the population, this topic is very often discussed in the field of scientific research. The choice of method for running analysis depends on the research question or problem, the subject and purpose of the research or practical professional use. The gold standard for evaluating both walking and running is the optical kinematic system. The aim of kinematic studies is to assess the motion of individual body segments or the body as a whole including a description of position, velocity, acceleration and rotational parameters (orientation angle and angular velocity) in space and time independently of the forces representing the cause of motion. In this field, researchers are particularly interested in the position and orientation of the lower extremities and the foot as the only segment in contact with the ground. Several studies have already been performed on the position of the foot in the lateral and frontal planes or on the running pattern. In addition, the degree of pronation / supination of the foot, various movements of the upper extremities, the position of the torso in the lateral plane and the position or inclination of the pelvis during the run were also evaluated. The most commonly evaluated biomechanical parameters of running are speed, pace, frequency and length of steps, length of double step, duration of individual phases of walking, strength, shock, both vertical and horizontal forces in different parts of running, extent of pronation or supination of foot and angular speed. Furthermore, asymmetries between the left and right lower extremities during running are an important aspect, both for the occurrence or prevention of injuries as well as for running efficiency.

Kinematic analysis can be performed two- or three-dimensionally with or without active or passive markers placed on the bone-anatomical points of the body when they are identified by software. The accuracy of the measurements depends on the location and number of cameras, the distance between the cameras and the markers, the number and type of markers and their movement within the data acquisition area. The complexity and high price of the equipment needed to perform measurements limits it to use in science or in top sports. Because optical kinematic systems are based on static cameras, data capture is limited to a specific area. Aware of the fact that running today is carried out in a variety of environments from city parks, forests, mountain trails to athletic stadiums and running tracks, we find that the use of optical kinematic systems is not always possible. This is quite complex, time consuming and limited to the laboratory environment; equipment is expensive. Therefore, the researchers began to develop and, in addition to the optical kinematic system, also use other systems that enable the performance of measurements in an uncontrolled / real environment or outside the laboratory. Global positioning systems (GPS) are widely known. These operate on the basis of electromagnetic and radio waves traveling from the transmitting to the central unit. GPS is used in sports watches, most commonly to measure distances and speeds. In addition, another commonly used support system is an inertial measuring unit measuring device consisting of an accelerometer and a gyroscope. Due to the completeness of the obtained data, other motion sensors such as barometers and magnetometers can be added to these measuring units and then called magneto-inertial measuring units. A magnetometer is used to determine the position of the north and thus determine the position of the device. With intensive development in recent times, wearable systems for running analysis are becoming smaller, more energy efficient and more affordable. Therefore, the number of professional and scientific contributions reporting on sports performance based on inertial measurement units has been gradually increasing over the last decade.

BACKGROUND OF THE INVENTION

There are many known solutions for physical activity measurements. Devices such as ActivPAL, ActiGraph and the like, which are placed on the wrist, waist or thigh, determine the position of the body or the state of activity of the individual with the help of accelerometers. The ActiGraph device provides data on the time of waking or sleeping on the basis of physical activity, activPAL measures the time of lying, sitting, standing and walking. Quite a few devices are commercially available for evaluating various running parameters. Different pedometers (RealAlt TriSport 3D Pedometer, Pingko Walking Pedometer, Omron Walking Style IV Pedometer, Newfel onwalk 500, etc.) are simpler, which allow measuring steps, distances and some also report calorie consumption. Most smartphones also contain accelerometers that allow you to determine an individual's physical activity and count steps. More complex devices are bracelets and sports watches such as the Nike + Sportband, Adidas miCocach Zone and Pacer, Suunto and Polar, which contain accelerometers and are created primarily to measure running speed. In addition, most also allow heart rate measurements. On the other hand, there are devices (Polar G3, Apple watch, various Garmin watches, etc.) and applications for smartphones such as Sports Tracker, Runkeeper - GPS Running Tracker and Map my run, which use GPS to track the route and calculate the distance. Even the simplest sports watches measure the heart rate, follow the route and give information about the distance traveled, the speed and pace of the run, the length and cadence of the steps (number of steps per minute).

The disadvantage of these systems is that they do not allow measurements of the orientation of body segments (eg pronation / supination of the foot) or the load on individual parts of the body or the forces acting on them during running. For optimal evaluation of the efficiency and biomechanics of running in a real environment in order to determine and eliminate risk factors for running injuries, measuring equipment that analyzes the movement and loads of the lower extremities is needed. Furthermore, a method is needed that allows easy analysis of data obtained by direct running measurements and a system that allows easy and understandable reporting of this data to the user. It also requires easy installation, which will at the same time ensure good sensor stability and comfort, as well as ease of use for runners.

The 3-axis accelerometer systems described in U.S. Patent Nos. 2,20150335280A1 and US9514625B2, which are mounted on the seventh cervical vertebra and on the sacrum, evaluate posture and provide feedback (acoustic or tactile) on adverse changes. U.S. Pat. Nos. 2,99824265B2 and US 9,811,720B2 disclose inertial measurement systems that are mounted on a crosshair and a method that allows individuals to be identified by their movement dynamics. According to patent EP2924675A1, a known solution for improving the technique of performing physical exercise consists of at least one accelerometer (which must be placed on the upper body - head, chest, upper back or shoulder ring), central and memory units. This system provides real-time feedback on the compliance of the performed movement with the previously set (reference) values. Accelerometer systems are also used to evaluate the effectiveness of medical devices such as orthoses and prostheses. US20140343460A1 discloses a system for determining asymmetries of movement of the lower extremities in individuals with prostheses, while CA2592042C presents a system and method that allows monitoring the movement of devices (orthoses or prostheses) based on measurements made with accelerometers.

Patents CN208876547U, CN102824177B and US9307932B2 disclose devices based on inertial measurement units and mounted on the feet either on the instep or on the heel. They are used to evaluate the temporal-spatial parameters of running. A similar solution is presented in US20190150793A1, except that the sensor is located below the outer ankle. Patent JP6037183B2 presents sensors in shoe insoles and a method for analyzing running technique. This system then uses the clock to give feedback to the runners. The accelerometer system is patented

US8744783B2 upgraded with one force sensor and a central data analysis unit. They then presented a method that, based on these measurements, allows the calculation of the power generated by the body during movement.

These solutions offer a good basis for studying movement, but in most cases they focus or allow use on only one body segment (foot). In case of desire or need to evaluate a larger part of the body (eg lower extremities) and relationships between individual joints, a different solution is needed. Closest to the subject is the invention CN103505219A, which discloses a system and method for estimating the movement of the human body based on the signals of accelerometers placed on both feet and on the belt. The system is wireless and, in addition to accelerometers, also contains a central unit for data storage and analysis. Despite the fact that in this case the accelerometer is placed on the belt in addition to the feet, it still does not allow obtaining data on the movement and loads of the knees and hips.

Various inertial or magneto-inertial measuring units such as RunScribe, Styrd, ETHOS, Garmin Footpood, FWIS Physiolog and DeltaTron have been used in scientific research in this field. These were in most cases placed on the feet or in one study on the ankle and knee, in another on the thigh and tibia, and in the third on the soft muscle (m. Gastrocnemius). Multisegmentality in this case would provide important insight into, for musculoskeletal safety, the key biomechanical technical characteristics of running. As far as we know, only three studies have installed sensors on several different parts of the body. In two studies, the areas of sensor placement were the lower back, thigh, shin, and foot, but the authors evaluated only walking in individuals with osteoarthritis of the knee. Therefore, the question of the applicability of such a method of evaluation in progress remains open. In the latest study, 12 ETHOS sensors were installed to monitor whole body movement while running. The authors of this study conclude that the most important areas of placement are on the torso and feet. They conclude that fewer sensors would allow for faster and easier installation and cause fewer disturbances or restrictions during the run.

The invention described in this application is a multi-accelerometer system and a method for evaluating mechanical stress during walking and running. The presented solution brings the possibility of evaluating the mechanical stress of all joints of the lower extremities during movement. The invention is intended to obtain important data on the biomechanics of walking in individuals experiencing various movement problems (eg after a stroke) and running in recreational and professional athletes. The invention makes it possible to capture accelerations at all joints of both lower extremities (foot, knee and hip) during walking or running. The system works by creating a text file when the measurement is started, where the data of all six accelerometers and the duration of the measurement are stored. When the measurement is completed, it is possible to view the graphs of each sensor separately in the 3x2 grid, where each of the three axes (x, y and z) is shown in a different color.

PRESENTATION OF THE TECHNICAL SOLUTION

The portable acceleration measuring system basically consists of a central unit 58, six three-axis accelerometers 59, which are connected to the central unit 58 via cables 4, and a computer program for plotting each sensor separately. The central unit 58 is carried by the subject either on the back (Figure 1) or on a belt in a purse. The sensors 59 are attached, depending on the length of the cables 4, to the lower limbs on both sides: the top of the foot (base of the second foot), the top of the tibia (tibial spasm) and the pelvis (upper anterior intestinal thorn). As shown in Figure 2, the central unit 58 consists of an electronics housing made of elements 5, 7 and 11, a Raspberry Pi 4B 10 computer, a PiJuice 8 power supply module with battery 9, an additional battery 6, a ChronoPi time module 12, a system cooling fan 15 with screws 16, 17, 18 and 19 and nuts M3 26, 27, 28, and 29 for mounting on the housing, on / off switches of the system 13, on / off switches for data acquisition 14, six visual indicators (LEDs) of sensor operation 20, 21, 22, 23, 24 and 25, nuts M3 30, 31,32, 33 and screws M3 34, 35, 36 and 37 for attaching the lower part of the electronics housing to the central part of the electronics housing, screws M3 38, 39, 40 and 41 for attaching the Raspberry Pi 4B to the lower part of the electronics housing, nuts M3 42, 43, 44, 45, 46, 47, 48 and 49 and screws M3 50, 51, 52, 53, 54, 55, 56 and 57 for attaching the housing cover electronics to the central part of the electronics housing. Each sensor (details shown in Figure 3) consists of two halves of a protective housing 1 and 2, a cable 4 connecting the sensors 59 to the central unit 58, and a printed circuit board with an accelerometer sensor element 3. Each pair of sensors (one sensor for the left and the second for the right lower limb) has the same length of cables 4. Three different lengths of cables 4 allow the placement of sensors 59 on certain parts of the lower extremities.

The system is started by switching the power switch 13. The constant illumination of LEDs 20, 21, 22, 23, 24 and 25 indicates that the system is ready to capture data. By switching the data acquisition switch 14 to ON, the measurement is started, a text file is created on the USB stick, in which the acceleration values of all six sensors and the relative measurement time are stored. During the measurement, the LEDs 20, 21,22, 23, 24 and 25 flash once per second. In case of problems with any of the six sensors, after switching the switch, the measurement does not start, the LED indicator of the non-functioning sensor or several of them starts flashing five times per second. The measurement is completed by switching switch 14 to OFF and the USB stick ends writing data to a text file. The data file name consists of the year, month, day, hour, minute, and second of the measurement start. After the measurement, the USB stick can be inserted into the computer on which Telasi Preview is installed, which enables quick analysis of measurement results.

The computer does not have a built-in auxiliary button battery that allows the system to maintain the correct date and time when the computer is without power. For this purpose, the time module provides the computer with the exact time even when it is without the main power supply. The computer program for plotting graphs (Telasi Preview) is designed in the Matlab software environment (The Math Works Inc., Natick, Massachusetts, USA) and can be installed as a standalone program on any computer. In the program, we select a text file of the measurement and the program makes its own graph for each sensor, which it arranges on the screen in a 3x2 grid for faster data review. Each of the X, Y, and Z axes on each graph is shown in its own color.

Claims (11)

PATENT APPLICATIONS 1. Multi-accelerometer system and method for evaluating mechanical stress during walking and running. characterized in that they consist of six three-axis accelerometers (59) connected by cables (4) to a central unit (58) and a computer program (Telasi Preview) for plotting graphs with measurement results; The system according to claim 1, characterized in that it has a printed circuit board with an accelerometer sensor element (3), which is protected by two halves of the protective housing (1,2) and is connected to the central unit (58) by cables (4); System according to claim 1, characterized in that the method of positioning the system is such that the subject carries a central unit (58) on the back or on a belt in a bag and accelerometers (59) are mounted on both lower limbs at the top of the foot feet), the top of the tibia (tibial spasm) and on the pelvis (upper anterior intestinal thorn); System according to claim 1, characterized in that the cables (4) are made of the same length for each pair of accelerometer sensor elements (3), which allows the accelerometers (59) to be placed on certain parts of both lower extremities (mentioned under claim 3); System according to claim 3, characterized in that the central unit (58) consists of an electronics housing (5, 7, 11), a Raspberry Pi 4B computer (10), a PiJuice power supply module (8) with a battery (9). , additional batteries (6), ChronoPi time module (12), system cooling fan (15), system on / off switches (13), data capture on / off switches (14) and six visual (LED) operation indicators sensors (20, 21,22, 23, 24, 25); System according to claim 5, characterized in that the system on / off switch (13) enables the system to be switched on and off; The system according to claim 5, characterized in that the on / off switch of data acquisition enables the start and end of data acquisition; The system according to claim 5, characterized in that the visual indicators of the operation of the sensors (20, 21, 22, 23, 24, 25) each have their own corresponding LED indicator; The system according to claim 5, characterized in that the visual indicators of the operation of the sensors (20, 21, 22, 23, 24, 25), with a constant light, inform about the readiness of the system for data acquisition; System according to Claim 5, characterized in that the visual indicators of the operation of the sensors (20, 21, 22, 23, 24, 25) flash once per second during the measurement, but in the case of problems with the sensors, the indicators of the inoperative sensor or more they start flashing five times per second; System according to claim 1, characterized in that the computer program for plotting graphs (Telasi Preview) prepares graphs of all three axes (x, y and z) on the basis of a text file, each colored with its own color, for each accelerometer separately in a 3x2 network.