with recent rapid economic growth , an affluent diet , lack of exercise , professional jobs , 
 and a sedentary life - style in which people are usually standing or sitting for long hours , 
 is on the rise1 . also , as people spend 
 more and more time using computers at home and in the workplace , thanks to the 
 popularization of the pc and universal usage of computers at work , hours of sedentary work 
 are increasing2 . crossing the legs can cause hip adduction , provide stability to the sacroiliac joint3 , and increase the torque on the lumbar 
 region by rotating the pelvis of a person with a limited joint range of motion in the 
 coxa4 . it has been reported that when 
 working in a standing position , an asymmetrical weight supporting stand - up position causes 
 asymmetric activation of the left and right trunk muscles and the muscles surrounding of the 
 hip joint , imposing abnormal stress on the tissue surrounding the hip joint and sacroiliac 
 joint . also , the habit of sitting with crossed legs can cause kyphosis , with 
 the additional possibility of causing scoliosis6 . minimal stimulus following a postural change elicits a change in 
 the peripheral circulation7 . sitting with 
 the legs crossed has the same impact on the nuclei and peripheral blood pressures , 
 temporarily causing partial numbness with a stinging tingly feeling , as if pricked by pins 
 and needles , due to neural pressure or blockage of blood supply8 . if the peripheral circulation does not function smoothly , the tissue or cells are not 
 provided with sufficient oxygen , causing organic change9 . the skin temperature is associated with the change of blood flow rate , and the skin s 
 absolute temperature is known to vary depending on the temperature of the external 
 environment , time , and the measured part . the controlling factor of skin temperature is 
 blood flow rate , and a lot of blood vessels and nerves are concentrated in the skin of the 
 body , playing a pivotal role in controlling the body temperature of the extremities10 . consequently , it is thought that sitting 
 upright or with the leg crossed for a long time causes a temporary disturbance in the blood 
 circulation , which will have significant impacts on the lower extremities . a number of studies have been conducted focusing on the asymmetric muscle activities of 
 truncal muscles during sitting with crossed legs11 , 
 12 , the legs on the spinal kinematical 
 changes and pelvic inclination in the sitting position with the legs crossed6 , but no research has measured the change in 
 the blood flow rate in the lower extremities through the change in skin temperature in the 
 sitting position with the legs crossed . accordingly , this study was conducted to test the hypothesis that if the sitting position 
 with crossed legs were to be continued , it would lead to neurothlipsis and blockage of the 
 blood supply to the lower extremities , causing leg numbness and poor blood circulation . infra - red computer thermography was used to measure the change in blood flow rate and the 
 variation of skin temperature in the lower extremities over the course of time . the subjects of this research were healthy adults who habitually adopted a posture of 
 sitting with their legs crossed . they were 23 healthy university students ( 8 males , 15 
 females ) who voluntarily agreed to participate in the experiment after receiving a full 
 explanation of the purpose and methods of research . because this experiment required the 
 adoption of a position of sitting with the legs crossed for a long time , the subjects were 
 selected from among persons without peripheral vascular diseases or blood circulation 
 disorders . the average age of the subjects was 19.480.80  years , their average height was 
 166.983.16  mm , and their average weight was 64.025.13  kg . the subjects had sufficient 
 muscular strength to perform the experiment and had no problems with the joint motion range 
 of the coxa . those who had congenital deformity in the lower extremities , or those who 
 suffered serious surgical or neurological disorder , or who had a physical injury in the 
 nether extremities , felt pain in the feet or waist over the past six months , were excluded . all test protocols were approved by the ethics committee of the physical therapy faculty of 
 kangwon national university . in order to estimate the change in the blood flow rate in the lower extremities , a 
 thermograph ( iris - xp , medi - core , south korea ) which senses the fine infrared light emitted 
 from the body surface and it as a map of body heat was used . it is a visual measuring method 
 which senses the infrared light naturally emitted from the body with a highly sensitive 
 sensor , in order to measure the temperature on the body surface . the data is recorded and 
 analyzed on a computer to calculate the subtle changes in temperature around painful or 
 diseased body parts . it draws a contour map of body heat in a full - color image , in order to 
 diagnose a bodily disease . the skin temperature is affected externally by the atmospheric temperature , humidity , air 
 current , etc . , and internally by the skin blood flow rate ( 56  mm depth ) . skin temperature 
 is usually in the range of 2434  c when the external temperature is steady at 21  c , and it 
 is mainly controlled by the vasomotion . thus , skin temperature under normal conditions shows 
 bilateral symmetry in the temperature distribution , but when a blood vessel is constrained 
 before vasomotion , it shows an asymmetrical temperature distribution . skin temperature , 
 which is the surface temperature surrounding a deep part , is regulated by the vasomotion of 
 skin , and it is used as an index to indicate the blood flow rate13 . before examining the shift in the blood flow rate , the 
 study procedures and precautions were explained to the subjects before the measurements , and 
 the changes in skin temperature were measured over time at specific sites , while the 
 subjects maintained sitting position with their legs crossed . for accurate imaging , the range of the indoor 
 temperature for each experiment was kept within 2021  c , the subjects were given 20 minutes 
 to adapt to the laboratory conditions . before the test , subjects were given sufficient 
 information about the factors affecting infrared images , and sunbathing was prohibited for 
 one week before the experiment . electromyography ( emg ) , nerve block , acupuncture , body 
 manipulation , and massage were prohibited within 72 hours before the test ; and alcohol 
 consumption , smoking , physical therapy , and transcutaneous electrical nerve stimulation 
 ( tens ) were prohibited within 24 hours before the test14 . the chair used in the experiment had a backrest and armrest , adjustable height , and was 
 fixed to the floor . the height of chair was adjusted so that in the upright sitting position 
 the hip joint and knee joint formed angles of 90 degrees . subject wore shorts to expose the 
 legs for measurement . taking into consideration the physical fatigue caused by the 
 experimental tasks , subjects were divided into a group of 12 persons ( group a ) who first 
 adopted a sitting position with the legs crossed , the lower part of the thigh of one leg 
 touching the upper part of the thigh of the other leg ( upper leg cross ; ulc ) and a group of 
 11 persons ( group b ) who first adopted a position with one ankle placed on the opposite knee 
 ( ankle on knee ; aok ) . the two other sitting postures were adopted in a random order in both 
 groups a and b ( fig . the subjects were instructed to adopt as comfortable posture as possible so that 
 they could sustain that posture , and they were continuously advised not to excessively lean 
 on the chair s backrest . they were also asked to adopt a position in which their knee , shin , 
 and instep were clearly seen on the monitor . each posture was kept for 30 minutes , and each 
 posture was photographed a total of 4 times , at 0  min , 10  min , 20  min , and 30  min . between 
 each posture measurement , subjects were given a 10  min break to allow their bodies to return 
 to the original body temperature , and during the break , an ankle pumping exercise was 
 executed while sitting on the floor with the legs stretched . normal sitting , b. ankle on knee , c. upper leg cross on the assumption that in the upright sitting position the temperature in the both legs are 
 symmetrical because subjects are healthy adults , only one leg which is raised upward was 
 measured . the 
 measurement sites were the knee ( patella ) , shin ( at the midway point of the shin bone ) , top 
 of the foot ( midway along the third metatarsal ) . the tip of the toe showed the biggest 
 temperature change , but it was omitted for convenience of measurement because of subjects 
 with obscure toe tips . among the 32 constituent parts , it is said that the average 
 temperature difference is 0.24  c15 , so 
 if at least 0.50.7  c difference is found in the symmetrical comparison , it should be 
 generally evaluated as significant16 . a repeated one - way anova determine the significance of temperature differences between the 
 upright sitting position and sitting with the legs crossed position . scheffe s test was 
 conducted as a post hoc test to determine the significance of differences . statistical 
 analysis was performed using spss 21.0 , and a significance level of 0.05 . the results are shown in table 1table 1.the changes in temperature of the lower extremity ( n=23 , unit :  c)0102030u - anklens27.30.627.10.726.70.826.30.2ulc27.20.726.70.726.10.825.60.8*aok27.50.927.21.126.71.026.11.1u - shinns29.60.429.30.429.00.428.60.3*ulc27.30.726.80.826.20.825.70.8*aok27.31.127.31.226.91.226.41.2u - kneens27.80.427.70.427.50.427.20.4ulc28.01.028.11.027.80.927.61.0aok27.20.927.00.826.60.726.50.7l - anklens27.30.627.10.726.70.826.30.2ulc27.60.727.51.027.00.926.51.0aok27.90.727.50.827.10.826.40.8l - shinns29.60.429.30.429.00.428.60.3*ulc28.91.028.60.828.30.728.00.7aok28.90.728.80.728.40.628.10.7l - kneens27.80.427.70.427.50.427.20.4ulc27.30.627.10.626.90.626.90.6aok27.00.626.90.526.70.526.60.4ns : normal sitting , ulc : upper leg cross , aok : ankle on knee . * was found with the course of time in the 
 ulc upper ankle , ns upper shin , ulc upper shin , and the ns lower upper shin positions 
 ( p<0.05 ) . there were no statistically significant changes in the other measured body 
 parts , but a clear difference in temperature was found in a temperature transition by 
 posture with the course of time . ns : normal sitting , ulc : upper leg cross , aok : ankle on knee . * p<0.05 there has been little research of contemporary subjects sitting position with the legs 
 crossed , and the research that has been performed has focused on the spinal angle , abdominal 
 muscles , and activity of the psoas muscles . even though previous studies have always emphasized the importance of an upright sitting 
 position , contemporary subjects who work on computers or study for long hours tend to adopt 
 a posture that strays from normal alignment to reduce fatigue in the postural muscles . also , 
 crossing the legs causes hip adduction , which provides stability to sacroiliac joint12 , and reduces the muscle activities of the 
 internal and external obliques . it is a posture which is often adopted to reduce fatigue in 
 the abdominal muscles during long hours of work . on the other hand , sitting with the legs 
 crossed can also increase lumbar region torque by rotating the pelvis of a subject with a 
 limited joint motion range of a coxa4 . it 
 causes axial asymmetry with asymmetrical activation of the internal obliques on both sides , 
 and the posture of sitting with the legs crossed for a long time may also cause cyanosis and 
 scoliosis6 . if the peripheral 
 circulation does not function smoothly , the tissues or cells are starved of oxygen , 
 resulting in organic change , but minimal stimulus following a posture change elicits a 
 change in the peripheral circulation5 , 7 . sitting with the leg crossed has the same impacts on the nuclei and peripheral blood 
 pressures , temporarily causing partial numbness with a stinging / tingly feeling as if pricked 
 by pins and needles , due to neural pressure or blockage of blood supply8 . the controlling factor of skin temperature is blood flow rate , and a lot of blood vessels 
 and nerves are concentrated in the skin of body , playing a pivotal role in controlling the 
 body temperature in the extremities10 . accordingly , this study measured the change in blood flow rate based on the change of 
 temperature in an upright sitting position and in a sitting position with the legs crossed 
 over the course of time , and discussed the results . the temperature of the lower extremities 
 decreased in the three postures adopted in this study . this is in agreement with a previous 
 report that found that sitting without moving the legs for a long time decreases the 
 circulation in the lower extremities17 . a 
 significant drop in temperature was found over the course of time in the ulc position . this 
 result may be explained by different compression forces in the two crossed - leg positions . compression force on the femoral vein in the ulc position is stronger than in the aok 
 position , causing problems with venous return from the distal lower extremity . an earlier study found that , subtle voluntary movement does not cause a significant 
 decrease in the surface vein pressure in legs18 . this is significant in that a subtle voluntary movement is related 
 to a 50% decrease in foot edema compared to a static sitting position19 . in a sitting position , voluntary foot movement prevents a 
 drop in the skin surface temperature , and it is recommended to do leg exercises frequently 
 and voluntarily during long hours of sitting at work20 . this study performed basic research into the estimation of the blood circulation in 
 multiple sitting positions using infrared computer thermography ( irct ) . the subjects were in their twenties , and they had no perspiration in the extremities or 
 circulation disorders . nevertheless , they showed a decrease in the temperature in the lower 
 extremities and started to suffer dysesthesia in the sitting position from 10 minutes after 
 the start of experiment . this result has a clinically significant implication for the 
 elderly , diabetics , and patients with peripheral vascular diseases . the leg numbness 
 recorded in this study supports the result of a previous study that reported that leg 
 numbness is caused by neurothlipsis or blockage in the blood supply8 . diabetic patients have a limited blood flow rate to the lower extremities , and diabetic 
 patients are 34 times more likely to have a peripheral vascular disease than a healthy 
 person , and the disease tends to be more severe and caused by blood vessels21 , 22 . in this regard , diabetic patients and patients with a peripheral 
 vascular disease are more likely to be affected by sitting for long periods than a healthy 
 person . disturbance in a smooth blood circulation , neurosis , infection , creation of calluses are 
 reasons for the delay of wound - healing in diabetic patients23 . blood circulation helps metabolism , growth , and reproduction by 
 supplying tissue cells with nutrients and oxygen . it also transports carbon dioxide and 
 wastes generated within cells for elimination in the lungs and kidneys . if the temperature drops , phagocytic ability is decreased and cell 
 mitosis is reduced24 . for this reason , it 
 is our recommendation that the elderly , diabetics , and patients with a peripheral vascular 
 disease have an injury in the extremities , they shouldl avoid sitting for long hours , and 
 especially sitting with their legs crossed as it causes dysesthesia and poor 
 circulation . a previous study reported that continuous and regular muscular contraction increases blood 
 flow slightly25 , 26 . accordingly , since contemporary work styles involve sedentary 
 work , sedentary workers should be encouraged to sit upright , and when long hours of work is 
 unavoidable , they should be instructed to do frequent leg exercises to facilitate blood 
 supply . in addition , for the smooth blood circulation , they should take a break to prevent 
 disturbance of the blood circulation in the lower extremities . a limitation of this study was that the subjects were limited to healthy persons in their 
 twenties , preventing a generalization of research outcomes to all age groups . also , because 
 of the difficulty of keeping one position for a long time , the measurement time was limited 
 to 30 minutes . furthermore , although efforts were made to measure precisely the same area of 
 all participants , because of the small size of the areas being measured and the programming 
 features of the measuring machine , subjective positioning was involved , and the area 
 observable on the surface was limited . irct estimates the blood flow over the course of time by comparing the temperatures at one 
 point of on surface images . future studies need to investigate subjects with a wide range of 
 ages and clinically useful body parts other than the three areas measured in this study . an 
 ultrasound study of direct observance of the blood flow inside blood vessels also needs to 
 be simultaneously conducted .
[ purpose ] the purpose of this study was to identify the effect of different sitting 
 positions on the skin temperature of the lower extremity . [ subjects ] 
 the subjects of this 
 study were 23 healthy university students ( 8 males , 15 females ) . 
 [ methods ] normal sitting 
 ( ns ) , upper leg cross ( ulc ) and ankle on knee ( aok ) positions were conducted to measure 
 the changes in skin temperature using digital infrared thermographic imaging ( diti ) . 
 [ results ] ulc upper ankle , ns upper shin , ulc upper shin and ns lower shin showed 
 significant declines in temperature with time . 
 [ conclusion ] these finding suggest that the 
 ulc and ns sitting positions cause decline of blood flow volume to the lower extremity 
 resulting in decrease of temperature of the lower extremity . 
 especially , sitting with the 
 legs crossed interferes with the circulation of blood flowing volume much more than just 
 sitting in a chair .