when a body part is under pressure , tissue cells do not 
 receive nutrients properly , thereby resulting in their death and the appearance of a lesion . in addition to exposure to pressure , an elevated body temperature and a high skin humidity 
 may also contribute to pressure ulcer formation , which appears as an irritation in the upper 
 layers of the skin and may reach muscles and bone tissue2 . pressure ulcers are harmful to subjects , particularly those who 
 have additional risk factors related to poor health3 . in this sense , therefore , it is important to prevent pressure 
 ulcers . the correlation between being seated and the presence of pressure ulcers has been reported 
 frequently since epidemiological studies of pressure ulcers were first conducted4 . barbenelet et al . reported the pressure 
 ulcer prevalence survey in the united kingdom and noted that chair - bound patients 
 consistently exhibited a higher frequency of developing pressure sores compared with 
 bed - bound patients with a similar degree of helplessness5 . other surveys have also shown this association between being seated 
 and the presence of pressure ulcers6 , 7 . the guidelines concerning pressure ulcers issued by the national institute for health and 
 care excellence ( nice ) in the united kingdom include a statement regarding seating , in which 
 the authors stressed the need for qualified assessment of seating needs , the importance of 
 correct eating positions , and the need to maintain posture and support the feet when using a 
 wheelchair8 . in people who are at risk 
 for pressure ulcers or in those with bedsores , pressure redistribution must be tended to 
 such that no pressure is applied to the pressure ulcer9 . a number of management strategies , including a number of 
 commercially available alternating pressure cushions and wedges , can provide pressure 
 redistribution10 , 11 . lee reported the effectiveness of cushions and an anterior wedge sitting position in 
 pressure ulcers . in their study , they showed that the type of cushion and appropriate height 
 wedges made a statistically significant difference in sitting pressure12 . several studies found a correlation between cushion types 
 and sitting pressure or between anterior wedge height and sitting pressure . however , 
 pressure redistribution when cushions and wedges are applied simultaneously has not been 
 investigated . consequently , the purpose of this study was to analyze user  cushion interface pressure 
 redistribution when different cushion types and height anterior wedges are applied 
 simultaneously for healthy volunteers . this 
 study was a pilot study to direct future research , to perform adult norm pressure 
 mapping . all participants were identified as able - bodied subjects , and the 
 procedure was fully explained to them . the exclusion criteria included any type of sitting problems , or 
 hearing , visual , or cognitive impairments that interfere with accurate participant 
 assessments . the subjects were informed that they could withdraw from the study at any 
 stage for whatever reason . participant characteristics are provided in table 1table 1.general characteristics of the subjectsmale ( n=15)female ( n=21)age ( years)21.7  2.020.1  0.5weight ( kg)66.1  8.753.9  9.2height ( cm)171.8  6.2158.4  5.1seat to footplate ( cm)46.7  5.343.8  4.6seat depth ( cm)49.5  3.545.9  4.9seat width ( cm)36.0  3.434.3  3.6hip ( )99.9  5.599.5  7.2knee ( )93.9  5.999.5  6.8ankle ( )93.4  5.797.3  6.3 . the conformat system and research software v.7.2 were used for pressure mapping and data 
 acquisition , respectively . one occupational therapist and three university students 
 collected the pressure data while the participants were sitting on a firm surface without a 
 cushion , a 5-cm height gel cushion , a 5-cm height memory foam cushion , a 3-cm anterior wedge 
 without cushion , a 3-cm anterior wedge with a 5-cm height gel cushion , a 3-cm anterior wedge 
 with a 5-cm height memory foam cushion , a 6-cm anterior wedge without cushion , a 6-cm 
 anterior wedge with a 5-cm height gel cushion , and a 6-cm anterior wedge with a 5-cm height 
 memory foam cushion . the participants were instructed to keep their chins tucked in , spines 
 straight , hands on their thighs , and pelvis neutrally positioned when sitting on the 
 cushions . they were initially instructed to flex their hips , knees , and ankles at 
 approximately 90 and to put their feet flat on the floor . each joint angle and sitting 
 position were checked for each measurement . after measurement , the pressure map was divided into four quadrants on screen graphics , with 
 each quadrant representing the left hip , left thigh , right hip , and right thigh . for the 
 quadrant division , the mergl method was adapted and used to analyze the sitting pressure on 
 the cushion . the peak pressure 
 was the mean of the maximum pressures measured with four sensors in each quadrant . the mean 
 pressure was the mean of the pressures measured with every sensors in each quadrant . the participant characteristics were 
 tested by descriptive statistical analysis , and results were tested by a one - way analysis of 
 variance and post - hoc analysis . general demographic information , including age , weight , height , and sitting position , is 
 shown in table 1 . in both genders , the mean and 
 peak pressures were the lowest when sitting on a 5-cm foam cushion . the mean pressure in the 
 hip and thigh was the highest on a 6-cm wedge and on a firm surface , respectively . the mean 
 pressure was observed to increase in the following order : a foam cushion , a 3-cm anterior 
 wedge with a 5-cm foam cushion , a 6-cm anterior wedge with a 5-cm foam cushion , a 5-cm gel 
 cushion , a 3-cm anterior wedge with a 5-cm gel cushion , a 6-cm anterior wedge with a 5-cm 
 gel cushion , a 3-cm anterior wedge without cushion , without cushion , and a 6-cm anterior 
 wedge without cushion ( tables 2table 2.peak pressure distribution according to wedge height and cushion type ( n=36 , 
 mmhg)firm surface5  cm gel cushion5  cm foam cushion3  cm wedge5  cm gel cushion with 3  cm wedge5  cm foam cushion with 3  cm wedge6  cm wedge5  cm gel cushion with 6  cm wedge5  cm foam cushion with 6  cm wedgerhpp*304.43  95.46123.04  71.21116.09  69.57308.64  91.46131.88  55.87122.25  67.42346.25  91.69158.92  55.58168.22  43.09rtpp*62.83  19.9352.49  17.7943.85  24.2877.73  29.5757.01  21.3948.19  18.1585.52  39.8966.28  25.9465.20  27.81lhpp*305.89  85.11120.03  40.14127.96  42.27321.21  88.04130.64  57.14130.03  92.82321.91  94.82146.31  65.99166.83  88.00ltpp*71.47  25.2454.61  24.8141.93  17.0567.99  37.9858.01  24.6143.75  17.4792.15  38.3757.52  25.0761.00 21.22r / lhpp : right / left hip pressure peak pressure ; r / ltpp : right / left thigh pressure 
 peak , * p<0.05 and 3table 3.mean pressure distribution according to wedge height and cushion type ( n=36 , 
 mmhg)firm surface5  cm gel cushion5 cm foam cushion3  cm wedge5  cm gel cushion with 3  cm wedge5  cm foam cushion with 3  cm wedge6  cm wedge5  cm gel cushion with 6  cm wedge5  cm foam cushion with 6  cm wedgetpm*59.09  10.2937.86  9.2429.45  9.3057.00  11.4939.14  6.5029.60  6.4360.45  10.0441.70  7.1330.92  8.52rhpm*85.04  17.6249.76  15.3939.41  13.0484.55  19.6454.74  14.0541.80  12.7288.61  18.3067.02  48.0342.65  15.67rtpm*31.88  11.7325.45  12.4117.78  7.1127.04  9.8524.93  6.6818.81  5.5629.26  9.3225.31  7.5822.59  19.51lhpm*85.86  16.4349.53  16.4142.53  18.7287.96  17.4967.39  6.0842.58  16.9288.68  17.0258.01  17.4545.83  17.91ltpm*30.84  11.1325.92  8.1218.19  6.9227.07  9.3426.61  6.7219.15  5.8129.06  9.6526.43  7.9027.71  8.02tpm : total pressure mean ; r / lhpm : right / left hip pressure mean ; r / lhpp : right / left 
 hip pressure peak , * p<0.05 ) . r / lhpp : right / left hip pressure peak pressure ; r / ltpp : right / left thigh pressure 
 peak , * p<0.05 tpm : total pressure mean ; r / lhpm : right / left hip pressure mean ; r / lhpp : right / left 
 hip pressure peak , * p<0.05 prolonged mechanical loading can lead to breakdown of the skin and underlying tissues , 
 which can , in turn , develop into a pressure ulcer13 . it may be caused by inadequate blood supply and resulting 
 reperfusion injury when blood re - enters the tissue . when sitting in the same position for 
 extended periods , the dull ache experienced is indicative of impeded blood flow to affected 
 areas . the shortage of blood supply may lead to tissue damage and cell death within 2 h14 . one of the assessment factors relating to 
 the prevention of pressure sores is the pressure of cushions on clients15 . the benefits of pressure relief and/or redistribution in minimizing pressure - related health 
 risk ( including of pressure ulcer ) , among other issues , have been well documented . however , few studies have offered information on the 
 combination effects of cushions with anterior wedges . hence , the objective of this study was 
 to evaluate pressure redistribution effects on the user  cushion interface pressure of 
 healthy volunteers in their 20s when applying different cushions , including a firm surface 
 with and without different height anterior wedges . our results show that the mean and peak pressures were greatest when sitting without a 
 cushion with 3-cm and 6-cm anterior wedges and without anterior wedge compared with the 
 other sitting arrangements . the mean pressure in the hip was the highest when sitting on a 
 6-cm anterior wedge without a cushion , whereas the mean pressure in the thigh was the 
 highest when sitting on a firm surface without an anterior wedge . in addition , the mean and 
 peak pressures were the lowest when sitting on a foam cushion without an anterior wedge . gong and an reported that the mean and peak pressures were the lowest when a 6-cm anterior 
 wedge was used . however , in this study , these two variables were the lowest when sitting on 
 a foam cushion without an anterior wedge11 . the participants of this study sit with the hip , knee , and ankle joint at 
 an angle of more than 90. therefore , the sitting professional must assess posture before 
 recommending the use of cushions and wedges . from the results , we presumed that the foam cushion could be the best choice for pressure 
 redistribution . these results suggest that people who sit , particularly those with diseases , 
 seek out professional support in choosing the appropriate cushion and height of their chair 
 based on their needs . the present study only compared the performance of two cushions , including a firm surface , 
 and two types of anterior wedges , in redistributing user hence , the number of participants , cushions , and wedge types , as well 
 as the height of the cushion and wedges , must be expanded for generalization in future 
 studies . cushion 
 interface pressure redistribution , the relationship between sitting positions and interface 
 pressure redistribution must be investigated . as the proper cushion types and anterior 
 height wedges for people with or without diseases , such as stroke , spinal cord injury , and 
 muscular dystrophy , must be established , this study establishes important guidelines for 
 future research for establishing a sitting environment .
[ purpose ] the purpose of this study was to investigate interface pressure redistribution 
 in healthy volunteers when applying different cushions and anterior wedge heights . 
 [ subjects and methods ] this study included 36 healthy individuals in their 20s . 
 the peak 
 and mean pressures were measured by applying different cushions and anterior wedge 
 heights . 
 the results were analyzed by using a one - way analysis of variance and post - hoc 
 analysis . 
 [ results ] the peak and mean pressures were statistically significant based on 
 the cushion types and anterior wedge height . 
 the peak pressure was at its highest and 
 lowest when sitting on a 6-cm anterior wedge and a foam cushion , respectively . 
 the mean 
 pressure was greatest when sitting on a 6-cm anterior wedge of a firm surface and smallest 
 when sitting on a 5  cm foam cushion . 
 [ conclusion ] this study shows that the most effective 
 method for pressure redistribution was sitting on a 5  cm foam cushion without an anterior 
 wedge .