Keywords

1 Introduction

In the era of knowledge economy, the refinement of social division of labor and the progress of science and technology liberated human physical burden gradually. The number of mental workers increased, and more and more work needs to be done with long time sitting at the desk. Professor Blackburn of University of Minnesota said that sitting was the change of civilization in the history of the most profound impact on human. This is the cause of metabolic disorders, and sedentary will not only cause disease, but also fatal.

Research from the World Health Organization (WHO) shows that each year about two million people died due to sedentary lifestyle, and it has become the first independent factor of the chronic non-infectious disease, a world-recognized public health and social problem. Therefore, while enjoying the rich material life brought by the social development, the sedentary crowd’s health problems should be taken seriously.

From scientific researches, there are three main theories about the sedentary hazards.

1.1 The Sitting Theory

Sang et al. (2015) proposed the necessary conditions in good posture: there are the most appropriate pressure distribution on intervertebral discs between each vertebrae, and the most appropriate, the most uniform static load distribution on the attached muscle tissue. If people sit on a chair in a way that is not in the natural shape of the spine, the intervertebral disc is subject to an abnormal pressure distribution, which can cause waist discomfort over a long time. When the angle between the trunk and thighs maintains about 115°, the spine is close to the natural shape, while the lumbar part must be supported. People who use a back about 90° will feel uncomfortable, because the trunk upright sitting posture will produce a lot of spine twisting force, at this time the weight of the upper body will also have a negative effect on the lumbar spine. The posture with trunk forward will straighten the originally lordotic lumbar, and makes it bend backward. This affects the normal curvature of thoracic and lumbar vertebra, leading to kyphosis (Namkoong et al. 2015). At the same time the increasing isometric trunk muscle strength for head supporting will cause fatigue in neck and back.

Sitting in a chair, people are in a dynamic state of stability. By constantly adjusting the position slightly, people eliminate abnormal pressure on the spine, which is called sitting posture. In addition to the spine, legs and pelvis are equally important, we can regard them as a simple mechanical lever support system: the hip (pelvis) is an unstable inverted triangle when sitting, and the surface between human body and seat is two piece of circular ischial tuberosity bones with little muscle attachment. The 25 cm2 sciatic tuberosity and the muscles under it bear the load of the weight of human body, which is sufficient to cause pressure fatigue. From a physiological point of view, this fatigue will restrict the blood circulating to the capillary, thereby affecting the nerve endings, leading to pain and numbness, etc. The two points on a seat cushion carry on most of the weight of human body, which has great mechanical instability. Under upright sitting position, the center of body gravity will deviate from the vertical of ischial tuberosities (about 2.5 cm in front of navel), which further aggravated the instability. Only by increasing the leverage effect provided by the legs and feet can people offset this instability. For example, sitting with leg crossed, arms relying on the desktop or supporting on the handrail, etc. are common ways to solve this instability. Good posture is often in a nearly natural state to balance the pressure of the body and reduce body discomfort. And its specific performance is waist straight naturally, two shoulders flush, and body slightly bent forward (backward). At the same time, sedentariness should be avoided in order to make the body relax in a half-dynamic state.

1.2 The Sedentary Pathological Hazards

The soft tissue of the human hip is a multi-layer structure, which is composed of the skin, fat, gluteus maximus and the capillary and nerve endings inside. Under the sitting position, the force between the hip and the seat surface is mainly made up of the pressure and shear stress from different directions, and they act on gluteus maximus together. If the gluteal soft tissue is excessively oppressed for a long time, then it will cause hip muscle contraction, and capillary blood flow slowdown or closed (Sugimura and Wada 2004), resulting in sitting discomfort or tissue damage, mainly manifested as fatigue, numbness and pain (Nakamura and Csikszentmihalyi 2014).

The force between the hip and the seat is mainly divided into pressure and shear stress, in which the shear stress is divided into horizontal shear stress and compressive shear stress with the same units. Usually, the maximum pressure is concentrated on the soft tissue of the 25 cm2 region below the sciatic bone. The pressure is derived from the vertical direction of the erect body and the supporting force of the seat surface; the horizontal shear stress comes from the frictional force parallel to the contact surface from the opposite direction. The compressive shear stress is formed by the pressure from the same direction but of different values. It usually appears in the area under uneven stress.

Improper posture will result in uneven distribution of body pressure, which may be one of the causes of lumbar spine disease, such as lumbar spine injury (Hu et al. 2015). The long-term poor posture will cause unbalanced pressure distribution of hip and back. While it is the spine and pelvis that mainly support the sitting human body, if the body is in a forward position for a long time, the protruding lumbar will be straightened and bend backward, which will finally lead to kyphosis. It is the same while under a left-leaning or right-leaning posture. The deformation could result in spinal injury. The treatment of kyphosis and spinal cord injury is quite a large expenditure annually, and the price our families and society pay for it is imponderable. It is of great significance to measure the pressure distribution of sitting posture and to study the relationship between the pressure distribution and the occurrence of lumbar disease.

1.3 The Sedentary Psychological Hazards

Not only the physical impact, but also sedentary people’s psychological impact cannot be ignored. However, psychological change is a complicated and step-by-step process, and at present there is no research to determine there is a strong correlation between sedentariness and psychological aspects such as emotion and fatigue. But there are experimental results from relevant medical institutions show that in the process of sedentariness, the continuous accumulation of metabolic substance will make the glycogen level decrease, and when it reduces to a certain level, people’s working efficiency will be decreased. Mental activity also consumes a lot of energy, so sedentary people, although not involve in physical activity of high intensity consumption, are still easy to feel physically and mentally exhausted. This fatigue is also related to people’s sense of work and the characteristics of brain processing. In modern society, the social division of labor becomes more and more detailed, and people often doubt about the meaning of work because of the lack of connection to their external factors. In addition, when work is disturbed or interrupted, people will also generate the negative feeling of fatigue. Psychologist Mihaly madean explanation of this phenomenon of mental activity. “Flow” refers to people’s sense of fullness and excitement when they give full attention to something. “Entropy” refers to the mentality of confusion when people are unable to concentrate on their work. In the state of “entropy”, the efficiency, creativity and autonomy of human will be reduced. People will doubt their own value, and thus become depressed and anxiety, and sedentariness will increase these psychological factors, which undoubtedly will aggravate the negative feelings of sedentary people. Sedentary people are more likely to be affected by the surrounding environment. Coupled with the pressure of work and life, these will make people lose their passion and sharpen the entropy state. In addition, people’s daily communication in contemporary society is becoming more and more dependent on the social network, the reduction of face-to-face communication between people is more likely to lead to communication barriers. If the psychological pressure cannot be timely troubleshooting, it is more easily to lead to mental illness.

In the past twenty years, PC and mobile phones have greatly promoted the development of the Internet. The Internet of things and smart device have become a hot field and trend that cannot be ignored. Smart device is a concept of science and technology arisen after the smart phone. Through the combination of hardware and software, such as upgrading traditional equipment or developing new equipment, products are given smart features with Internet of things. Smart enables the equipment to connect with the device, achieve the loading of Internet services, and form the typical architecture of “cloud + terminal” with the additional value of big data. Smart device has been extended from wearable devices to smart TVs, smart home, smart cars, health care, smart toys, robotics and other fields, which typically includes Google Glass, Samsung Gear, Jawbone, Tesla, LETV TV etc. In this paper, the design of the smart cushion for sitting posture correction of the sedentary crowd is to detect the sitting time and the pressure distribution of these people, and then give advice such as stand to rest or adjust the sitting position at the right time.

2 The Device Design

2.1 The Design Aim of Smart Cushion

The outcome can be used in home-care and office-care, for example, the health examination and health care of desk workers and the elderly. In addition, it is effective to help people get rid of bad habits and improve the quality of life.

Sitting balance is an important indicator to measure whether people’s sitting posture is healthy or not. The daily monitoring and analysis of sitting balance of sedentary people, can not only help them to get a more comprehensive understanding of their sitting posture, but also dig deeper on the relationship between the center of sitting pressure and human health. And sufficient amount of data can reflect the general habit of sitting posture. The existing sitting pressure distribution measurement system has the disadvantages of high cost, importability and complexity.

Based on the measurement of sitting pressure data of the sedentary crowd, the smart cushion can display, store and carry out preliminary analysis.

The smart cushion needs to meet the following requirements:

  1. (1)

    The cushion design should conform to ergonomics, which helps disperse the pressure generated by the weight of the ischial tuberosity and the hip. Its materials should ensure the thermal comfort of human body.

  2. (2)

    It can record the data and store the data to the cloud server with Internet of things. It cannot only display the measured data in real time, but also compare it with the measured data in history and make relevant evaluation based on measurement data.

  3. (3)

    The device system is stable, easy to use, suitable price, and easy to promote. It can be used by the social.

2.2 The Cushion Design

Kazushige et al. studied the static and dynamic pressure distribution on cushion made of polyurethane foam. The results show pressure distribution in the various parts of the body both in short time and long time, and foam with low stiffness has better effect of than that of high stiffness. Stepen Spdglr et al. (Yost and Oates 1968) made impact testing on wheelchair cushions of different materials, and the results indicate that contour foam cushion could reduce impact loading, showing remarkable resilience.

In this study, the design of smart cushion is based on contour foam cushion with low stiffness.

2.3 The Size of Cushion

This study chooses the physical parameters of 50% digits, namely sitting depth 457 (male), 433 (female), hip width 344 (male), and 306 (female) as the dimensions of the cushion design reference. Based on the size of general office chair and the characteristics of cushion materials, the overall dimensions of the cushion is 44 cm × 34 cm × 7.5 cm, as shown in Fig. 1.

Fig. 1.
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The shape of cushion

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The ischial tuberosity is not a anatomical landmark, but rather a curved bone area. The distance of the high pressure areas depend on the forward/backward rotation of the pelvis, since the ischial bones converge towards the pubis. According to general human physiological characteristics, referring to the distance between ischiums under upright sitting position, the placement of pressure transducer is shown as in Fig. 2, the measured pressure is Ful, Fur, Fdl, Fdr.

Fig. 2.
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The position of the sensors

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2.4 The Material of the Cushion

Memory foam was created in 1962 in a study by NASA. During the design of escape system of Apollo command capsule, this material was developed and used to absorb the tremendous impact generated when the rocket takes off and the spacecraft returns to the atmosphere, or in some unexpected circumstances (such as crash), as well as improve the protectiveness and comfort of the seat[33]. Memory foam is a polyurethane polymer with open cell structure, with special viscoelastic property and strong ability of impact absorption. The molecule is very sensitive to temperature, so it is also called the temperature sensitive memory foam.

As material for cushion, it is under the pressure that is near static pressure. The molecular structure of memory foam material will flow to fit the deformation, and spread force to the entire surface, shown as in Fig. 3.

Fig. 3.
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The material of memory foam

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The choice of memory foam as a the cushion is based on its two characteristics:

  1. (1)

    Thermal properties: it could react to the human body temperature and gradually become soft. While absorbing the human body pressure, it can also help people adjust to the most comfortable posture. As for the lower part not exposed to the human body, it still maintains full supporting ability;

  2. (2)

    Viscoelastic characteristics: though under compression and subsidence, it will not rebound strongly, and will gradually return to its original shape when the pressure is removed;

The pressure of human skin blood circulation is 36 mmHg, and the memory foam could distribute the pressure evenly and reduce it to less than 36 mmHg thus enhance blood circulation.

3 Function Module Design

The framework of the multi-channel pressure acquisition system is shown in Fig. 4.

Fig. 4.
figure 4

The multi-channel pressure acquisition system

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The pressure acquisition module realizes the basic data acquisition. It comprises a pressure sensor, a signal amplification circuit and a digital to analog conversion module. The pressure sensor and digital circuit are used to collect data. The Arduino board realizes the conversion between analog signal and digital signal. Pressure acquisition module itself does not analyze or store data, but by the other two modules (mobile phones and server) for processing. Its basic structure is shown in Fig. 5.

Fig. 5.
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The pressure acquisition module

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In order to ensure the simpleness and feasible of data viewing, it uses the mobile phone as the actual data receiving and analyzing terminal. The pressure acquisition module transmits the real-time data to the mobile phone through the Bluetooth. The mobile phone receives the data and calculates and displays the relative value of the force, the pressure center and the impulse. When the measurement is completed, the data is uploaded to the server. At the same time, users can obtain their historical measurement data and some other relevant data through the network (such as their sitting habits, family sitting habits, etc.). The overall function of the mobile phone is shown in Fig. 6.

Fig. 6.
figure 6

The overall function of the mobile phone

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The function of each module is as follows:

Bluetooth receiving module: By calling the system API and Bluetooth pairing and connecting, it could achieve the real-time monitoring of data collected by the acquisition module.

Data processing module: Achieve the real-time processing of the received data, data transmitted to the mobile phone through Bluetooth is pressure values with range of 0~50 kg, so calculation is necessary to get the relevant useful parameters (pressure center, impulse).

Data display module: It is the visual part of the program responsible for displaying useful information to users such as the real-time measurement interface, historical data and the proposed interface on App.

Network communication module: Based on the HTTP protocol, this module uses Web Service to communicate with the server, upload data and query the overall data and historical data.

Storage and analysis module: It stores the data of measurement each time in the cloud to ensure the consistency of the data at different mobile terminals, and collect data for analysis. The server is also responsible for data storage and analysis and the maintenance of user tables and measurement data tables. The user table records the user’s basic information, such as height, weight, etc., for reference in the server analysis. The measurement table records the measurement results of each user each time, which is divided into 5 parts: the pressure of four measuring points and their force center. When the measurement is completed, the mobile terminal sends the request to the server, and the server stores the data and returns the corresponding test result.

4 Device Implementation

Device implementation of the overall system requires the acquisition of 4 channels pressure signal, after A/D conversion and the initial processing by the serial port to the host computer. The pressure sensor using a common half bridge strain sensor. A/D and DSP processing part using Arduino Uno programmable board. Power supply uses 3 AAA batteries.

4.1 Component Selection

The system requires the pressure signal to be a low frequency biological signal, usually not more than 2 Hz. Because of the long duration of the data acquisition, high sampling rate will lead to excessive data. According to the sampling law, the acquisition frequency of this system is determined as 5 Hz. Pressure sensor’s parameters are shown in Table 1. The full load output of the sensor at 5 V voltage is 5 mv, and the input range of the Arduino Uno A/D is 0–5 V, so the amplification of the amplifier circuit is about 1000. The accuracy of the coordinates accuracy is 0.2%, requiring the accuracy of A/D more than 9 bits, and Arduino Uno with 10 bit A/D converter can meet the requirements.

Table 1. The component selection
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4.2 Operational Amplifier

Because the output pressure signal is too small to carry on the A/D conversion directly. Amplifier is necessary to realize the preamplifier, which is to amplify and buffer the input signal to improve the resolution, so that the voltage range of the signal could match that of the A/D conversion circuit. According to the previous magnification of 1000, the INA128 operational amplifier of TI can meet this requirement, which is a universal instrument amplifier with low power and high precision. The operational amplifier design and small size enable it to obtain a wide range of applications. The feedback current input circuit can provide wide bandwidth even at high gain. Any increased profit between 1~10000 can be determined by a single external resistor.

INA128 magnification G is

$$ {\text{G}} = 1 + \frac{{50\,{k}\Omega}}{{R_{g} }} $$

After calculation, The Rg is 50 Ω.

The main Features of INA128 are as Table 2.

Table 2. Theparameter of INA128
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4.3 Digital Circuit Part

The function of the digital circuit includes the A/D conversion of analog signal, the initial processing and the serial communication to the host computer. The parameters of the selected Arduino Uno programmable board are shown in Table 3.

Table 3. The parameter of Aduino Uno
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Table 4. The mean value of the pressure center in the 10 sitting postures
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4.4 Circuit Design

The amplifier circuit is shown in Fig. 7, where Rg is 50 Ω, R1a and R1b are adjustable resistors that are used to adjust the static bias of the circuit.

Fig. 7.
figure 7

The signal amplifier circuit design

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4.5 Design of Data Receiving Module

The data acquisition module does not store the data, so data receiving is realized by APP. Through the data processing and storage can it real-time display sitting posture to users, and record and summary long-term sitting habits.

APP mainly includes three modules, the detection module, query module, setting module. The detection module is mainly responsible for the collection and calculation of data in real time, to show users their sitting posture, and record sitting habit; query module is responsible for providing historical data; setting module mainly carries on the entry of basic information such as weight and height.

5 Data Calculation

Calculation is mainly related to the data center of pressure and the impulse of each sensor. With 9600 baud rate, the real-time calculation is used to avoid excessive memory occupation and independent storage space. Among the characterization indexes of body pressure distribution, the asymmetry is related to sitting balance, which is shown as follow.

$$ {\text{C}}_{V} = \frac{{\sum\nolimits_{{\varvec{i} = 1}}^{{\varvec{ N}/2}} {|\varvec{P}_{{\varvec{iL}}} - \varvec{P}_{{\varvec{iR}}} | \cdot\Delta s} }}{{\sum\nolimits_{{\varvec{i} = 1}}^{{\varvec{ N}/2}} {|\varvec{P}_{{\varvec{iL}}} + \varvec{P}_{{\varvec{iR}}} | \cdot }\Delta s}} $$
(1)

ΔS is the action area of a single sensor PiL, PiR are the pressure of the first i left and right measuring point

The larger the CV is, the less balanced the body pressure distribution is.

The smart cushion collects and analyzes the signal of four pressure sensors, and calculates the pressure center and compares it with that of the natural sitting posture. It also calculates the impulse within a period of time of each sensor, in order to provide guidance of sitting behavior.

5.1 Mathematical Model

The mathematical model of the human body itself is highly symmetrical. Overlooking the cavity profile, it can be seen as a flat oval. When a person is fixed on seat, poor posture would show deviation from the standard value of the state, specifically refers to the adjustment of sitting behavior leading to the change of coordinates of centroid of the upper part of the body. If we take the geometric center of the four sensors for the origin, and the pressure center under standard posture as the first reference point, we could establish a two-dimension coordinate system. Then the real coordinate deviation caused by sitting behavior could reflect the change of centroid. So we need to transform the centroid deviation into quantity available to sensors, and give specific and scientifically reliable formula, as shown in Fig. 8.

Fig. 8.
figure 8

Pressure center calculation reference coordinate system

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For analysis purpose, the formula is built on the base of the following assumptions:

  1. (1)

    Ignore the individual differences in the body part, and under the standard sitting posture trunk is both front-back and left-right symmetrical;

  2. (2)

    The centroid related inertia parameters can be measured or simulated by functions or empirical formula;

  3. (3)

    The effect of non observed variables such as the environment, physiological state of mutation and other uncontrollable factors on the observed quantities is small.

5.2 Calculation of Pressure Center

The original stress distribution is simulated by the shape function, and the pressure is taken as the shape function F (x, y). Because the pressure values of four points Ful, Fur, Fdl, Fdr are known, there are 4 parameters a1, a2, a3, a4,

$$ {\text{F}}\left( {{\text{x}},\,{\text{y}}} \right) = {\text{a}}_{ 1} {\text{xy}} + {\text{a}}_{ 2} {\text{x}} + {\text{a}}_{ 3} {\text{y}} + {\text{a}}_{ 4} $$

Four points can be substituted and get a1, a2, a3 and a4

Set the Force as

$$ {\text{F}}_{\text{k}} = \smallint _{\varOmega } F\left( {x, y} \right)dxdy $$
(2)

Then the coordinate of Force is

$$ {\text{x}}_{\text{c}} = \frac{{\mathop \smallint \nolimits_{\Omega }^{{}} {\text{F}}({\text{x}},{\text{y}})\cdot{\text{y}}\cdot{\text{dxdy}}}}{{\mathop \smallint \nolimits_{\Omega }^{{}} {\text{F}}({\text{x}},{\text{y}}){\text{dxdy}}}} $$
(3)
$$ {\text{y}}_{\text{c}} = \frac{{\mathop \smallint \nolimits_{\Omega }^{{}} {\text{F}}({\text{x}},{\text{y}})\cdot{\text{x}}\cdot{\text{dxdy}}}}{{\mathop \smallint \nolimits_{\Omega }^{{}} {\text{F}}({\text{x}},{\text{y}}){\text{dxdy}}}} $$
(4)

5.3 Impulse Calculation

Impulse is the effect of a Force varying with time on the an object. It is the integral of force to time:

$$ {\text{I}} = \smallint {\text{Fdt}} $$
(5)

The impulse of the four points of Ful, Fur, Fdl, Fdr can be calculated.

6 The Whole Device Realization and Experiment

6.1 Device Acquisition Section

The whole device was completed according to the above analysis and design, as shown in Fig. 9.

Fig. 9.
figure 9

The whole device

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6.2 Implementation of Mobile Terminal

The main factors that affect the App interface design of medical mobile products are user, business, scene and product. Users’ difference in physical and psychological aspect and difference in scenarios will determine the App interface design, while the user’s behavior habits determine their operating logic.

The design of mobile App for sedentary family, follow the development flow of App interface design. Through the user interviews and survey data of qualitative research and quantitative research to determine the demand for products → information architecture design → interaction design → visual interface design. In this section, the pressure center setting interface and the detection interface, as shown in Fig. 10.

Fig. 10.
figure 10

Impulse display interface of each measuring point of pressure center detection

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6.3 Test and Analysis

Subjects

15 healthy people without lumbar spine disease were tested. Informed consent of all subjects. The age is 26.5 ± 1.4 years, the weight is 71.5 ± 8.4 kg, the height is 174.4 ± 3.4 cm and the BMI is 23.4 ± 2.09.

Experimental preparation

Test cushion is of 44 cm long, 34 cm wide, 7 cm high, placed on a height adjustable office chair with a back and no handrails. The seat surface length 47 cm, width 43 cm, nylon mesh fabric material, steel structure.

Because of the difference of individual body, it is difficult to define a pressure center suitable for everyone. The specific method used in this paper is: The subjects are seated, and adjust the seat to the comfortable height according to their daily habit of sitting posture. Then take natural sitting posture, namely the trunk and thighs about 150°, when the spine is close to the natural form. The observer record the center of pressure at this time as a reference point of the subjects.

Due to the limited storage space, in actual use, the phone does not store all the original data. Data testing and analysis are carried on by PC. The pressure center collection interface is shown in Fig. 8, and the pressure center coordinate data in real time is shown in Fig. 11.

Fig. 11.
figure 11

The pressure center interface and the pressure center coordinate data

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Experiment design

A total of two tests carried out in this paper, the center of pressure acquisition test for validating the feasibility and rationality of this design, which perform as realizing the dynamic real-time measurement of people’s pressure center, and calculating the cumulative effect; sedentary pressure center acquisition test aims to give preliminary exploration of the sedentary pressure distribution.

Multi seat pressure center acquisition test

When start, the observer records time, and ask every subject to change posture following a certain order LF - F - RF…… nine postures in total, each position for 5 s, to record the coordinate of the pressure center in this period of time, explore the pressure center under different sitting postures. The table is the mean value of the pressure center measured under 10 kinds of sitting posture for 15 persons (Table 4).

Sedentary stress center collection test

The subjects sit uninterruptedly in the testing chair for in 30 min, during which they can adjust themselves to maintain a comfortable position, and track the pressure center in this period. Because the sampling rate is high, so take the arithmetic mean value of the pressure center in 1 min as the pressure center within this period of time. The pressure center track drawing 10 min, 20 min, 30 min, as shown in Fig. 12.

Fig. 12.
figure 12

The pressure center tracks of the 15 subjects in each 10 mins

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6.4 Test Result Analysis

Test 1 shows that the smart cushion can basically reflect the balance of human sitting posture. According to the coordinates of the pressure center, the balance of sitting posture can be determined. The test results show that the design is feasible.

Results of test 2 show that in the 30-minute test time, pressure center changes from denseness to divergence. It indicates that over time, the amplitude of the change of pressure center increases, and it can be inferred that in the earlier period the subjects’ sitting behavior is more singular and stable, latter they adjust posture to relieve the fatigue caused by sedentary.

7 Discussion

This paper describes the research at home and abroad of pressure distribution, sitting thermal comfort and cushion design, and analyze and summarize the pathological and psychological mechanisms of the influence of sedentariness. According to the anthropometric data of Chinese, this paper builds an smart cushion prototype, and realizes the hardware prototype of each module and illustrates the key technology of the software module used. It also puts forward an algorithm for simulating sitting balance. At the end this paper presents the mobile terminal prototype, sums up the results and makes analysis and prospect.

Design and fabricate a 4-point sensor array. The distribution of the sensor array is in accord with the characteristics of the human body pressure distribution, and the sensor has the advantages of stable conductivity and appropriate price, which makes the whole sensor array cost-effective and has great potential in commercial applications.

By calculating the pressure center to reflect the balance of human sitting posture, and display it to the users through a simple and intuitive form in the mobile terminal so users are available to the real-time results of adjusting sitting position. By calculating the cumulative effect of the force, reflecting the long-term sitting habits of the user, in order to further explore the balance of sitting posture and its pathological basis. When the smart cushion is finished, which could detect social problem of sittingsedentariness.

Considering the cost and practicality, the number of sensor points is less. In the future, we can increase the number of sensor points and improve the resolution of the system.

The relationship between the sitting balance and path physiology has not yet been studied quantitatively and qualitatively. The analysis needs a large sample of normal and diseased people to get the correlation between body pressure distribution data and disease, thus can provide guidance for sitting behavior.

In this paper, the stability of the sensor and the circuit has a lot of room for improvement, and joint research is necessary for investment.