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Effectiveness of leg movement in reducing leg swelling and discomfort in lower extremities
Applied Ergonomics 43 (2012) 1033e1037
Contents lists available at SciVerse ScienceDirect
Applied Ergonomics journal homepage: www.elsevier.com/locate/apergo
Effectiveness of leg movement in reducing leg swelling and discomfort in lower extremities Yen-Hui Lin a, b, *, Chih-Yong Chen c, Min-Hsien Cho c a
School of Occupational Safety and Health, Chung Shan Medical University, No. 110, Sec.1, Jianguo N. Rd., Taichung City 402, Taiwan, ROC Department of Occupational Medicine, Chung Shan Medical University Hospital, Taiwan, ROC c Institute of Occupational Safety and Health, Council of Labor Affairs, Executive Yuan, Taiwan, ROC b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 19 April 2011 Accepted 5 March 2012
Various occupations required that workers stand for long periods, causing discomfort and pain. This study considered the effectiveness of three leg movements in relieving discomfort of the lower extremities during long periods of standing at work. Ten paid male subjects with no history of problems of the lower extremities were enrolled in this study. They performed three leg movements on a hard floor while standing for 4 h in a laboratory setting. Each 1 h experimental test had two phases e 50 min of standing, followed by 10 min of rest. During the period of standing, one the following leg movements was made. No movement (no change in posture), ankle movement (twice, for 2 min each time), and hip movement (twice, for 2 min each time). Observations revealed that the three leg movements yielded different degrees of lower limb swelling. The percentage changes in thigh (1.22%) and shank (1.32%) circumferences were largest during prolonged standing without any movement and lowest during prolonged standing with ankle movement (0.61%) and hip movement (0.80%). The relationship between perceived discomfort and standing time was determined. The subjects perceived the most shank discomfort (5.8) during the 4 h test without any movement. Leg movement greatly influenced perceived discomfort of the shank. The results of this study suggested that workers should move their ankles and hips for a short period following prolonged standing for 30 min to reduce lower extremity discomfort. Ó 2012 Elsevier Ltd and The Ergonomics Society. All rights reserved.
Keywords: Prolonged standing Leg movement Lower extremity circumference
1. Introduction Various workers, including supermarket checkout employees, assembly and quality control workers, and healthcare staff, are required to stand for long periods (Ryan, 1989; Cook et al., 1993; Redfern and Chaffin, 1995; Redfern and Cham, 2000; King, 2002). Many studies had found that standing for long periods is related to various health problems, including, in particular, low back pain and lower extremity discomfort (Zhang et al., 1991; Marr and Quine, 1993; Kim et al., 1994; Cham and Redfern, 2001; Chester et al., 2002). The effects of musculoskeletal disorders that were associated with prolonged standing on health insurance, absenteeism, productivity and well-being was substantial (King, 2002). Therefore, the prevention of musculoskeletal disorders that were associated with prolonged standing in the workplace has become an
* Corresponding author. School of Occupational Safety and Health, Chung Shan Medical University, No. 110, Sec.1, Jianguo N. Rd., Taichung City 402, Taiwan, ROC. Tel.: þ886 4 2473 0022x12119; fax: 886 4 23249194. E-mail address: [email protected] (Y.-H. Lin).
increasingly important concern in many industries (Zander et al., 2004). Many ergonomic interventions that were used during prolonged standing tasks, including alternation of the flooring on which workers stood, changed of posture, the provision of sit/stand chairs, and the use of in-soles in footwear, had been proposed to tackle musculoskeletal disorders (Hasegawa et al., 2001; Messing and Kilbom, 2001; King, 2002; Chiu and Wang, 2007; Bridger, 2009). However, complaints of musculoskeletal disorders that were associated with long-term standing in the workplace had not been completely eliminated. For example, many studies had studied the effect of floor type on subjective and biomechanical/physiological objective measures that were believed to be related to standing discomfort (Madeleine et al., 1998). However, investigators who were concerned with the effect of flooring on these measures had obtained conflicting results (Redfern and Cham, 2000; Zander et al., 2004). Some studies had revealed a relationship between floor type and fatigue, while others had not. Additionally, studies had established that standing work without any motion or walking caused greater musculoskeletal discomfort than a combination of standing/walking tasks (Hansen et al., 1998). However, relatively
0003-6870/$ e see front matter Ó 2012 Elsevier Ltd and The Ergonomics Society. All rights reserved. doi:10.1016/j.apergo.2012.03.002
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Y.-H. Lin et al. / Applied Ergonomics 43 (2012) 1033e1037
few attempts had been made to evaluate the practical effectiveness of a considerable variation in the motion of the feet and legs in tackling musculoskeletal disorders. One aim of this study is to determine if the use of three leg movement strategies during prolonged periods of standing change leg circumference and subjective discomfort ratings. Another goal is to provide to industrial personnel regarding evidence in support of ergonomic recommendations to promote health in the workplace by reducing pain or fatigue of the lower extremities during prolonged standing. 2. Materials and methods
were the fixed factors. Subjects were treated as a random factor. In the experiment, each subject performed simulated standing in the laboratory three times, each time for 4 h. During each such period, the subject intermittently performed a particular leg movement. Therefore, each subject performed a total of three 4 h tests. The response variables were a subjective rating of lower extremity discomfort and the circumferences of the thigh and shank before and after the test. Subjective ratings of lower extremity discomfort were consistent with the study of Cham and Redfern (2001): they were given on a seven-point Likert scale, ranging from 1 for “no discomfort” to 7 for “extremely uncomfortable”. The circumferences of the thigh and shank were measured at the start of each session and after 50 min of standing.
2.1. Subjects 2.4. Experimental procedure Ten paid male subjects aged 26e35 (mean, 30.2) participated in this study. Their average height was 170.9 7.3 cm and their average weight was 67.6 5.9 kg. All subjects were in good health and had no history of musculoskeletal, cardiovascular and diabetic problems. Before participation, the subjects were informed of the aims of the study, and they all participated voluntarily. 2.2. Apparatus A compatible personal computer (PC) with a 17inch TFT-LCD monitor was used in the computer-related tasks. A Gulick measuring tape was used to measure variations in the circumference of the lower extremities. This tape measure did not generate tension, and a tension meter at one end of the tape ensured that all measurements were made with equal pressure on the test area, to minimize errors that would otherwise have been caused by traction and the compression of soft tissues. Subjects were asked not to remove marks. 2.3. Experimental design An experiment was performed with a two-factor design with repeated measurements. Leg movements (no movement, ankle movement and hip movement) and measurement time (four levels)
Before the experimental session, a subject’s experimentally significant anthropometric data were measured to facilitate workstation adjustments. These covered body height, weight, eye height, and elbow height. Keyboard height at the workstation was adjusted to suit the subject’s elbow height; the monitor was placed approximately an arm’s length from each subject, and the center angle between the eye and monitor was 20 . As indicated above, each subject participated in three experimental sessions. The experimental task, performed on a computer, simulated prolonged standing tasks in a realistic work situation. The computer-related task involved netsurfing or watching movies, with no data input via the keyboard. Subjects adopted a natural stance when performing the tasks on the computer and were permitted to work at their own rhythm. Each session lasted for approximately 4 h, and each subject had a single session daily. Each 1 h period comprised of two periods e 50 min of standing followed by 10 min of rest. A force plate was used as the hard floor on which each subject stood. During each 50 min standing period, one of the following leg movements was performed. (1) No movement (no change of posture), (2) two ankle movements, and (3) two hip movements. Under condition (1) without movement, the subject’s feet were verified to be within the range of the force plate, and leg resting was discouraged. Under conditions (2) and (3), subjects were asked to
Fig. 1. Ankle (a) and hip (b) movement strategies examined during prolonged standing.
Y.-H. Lin et al. / Applied Ergonomics 43 (2012) 1033e1037
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Table 1 Means and standard deviations of thigh and shank circumferences (cm), and their changes (% change) for three leg movement strategies used during a period of prolonged standing. Without any movement Thigh
Pre Post1 Post2 Post3 Post4 Average D(D%)
Ankle movement Shank
Hip movement
Thigh
Shank
Thigh
Shank
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
49.3(2.9) 49.8(3.0) 49.8(2.9) 49.9(2.8) 49.9(2.9)
e 0.5(1.01) 0.5(1.01) 0.6(1.22) 0.6(1.22) 0.55(1.12)
37.8(2.5) 38.2(2.5) 38.3(2.5) 38.3(2.5) 38.3(2.5)
e 0.4(1.06) 0.5(1.32) 0.5(1.32) 0.5(1.32) 0.48(1.26)
49.4(3.6) 49.6(3.5) 49.7(3.6) 49.7(3.6) 49.7(3.6)
e 0.2(0.40) 0.3(0.61) 0.3(0.61) 0.3(0.61) 0.28(0.56)
37.5(2.8) 37.8(2.9) 37.9(2.9) 38.0(2.9) 38.0(2.9)
e 0.3(0.80) 0.4(1.07) 0.5(1.33) 0.5(1.33) 0.43(1.13)
49.4(3.6) 49.6(3.6) 49.7(3.6) 49.8(3.6) 49.8(3.7)
e 0.2(0.40) 0.3(0.61) 0.4(0.81) 0.4(0.81) 0.33(0.66)
37.3(2.8) 37.4(2.8) 37.5(2.8) 37.6(2.8) 37.6(2.8)
e 0.1(0.27) 0.2(0.54) 0.3(0.80) 0.3(0.80) 0.23(0.60)
Note: Pre: beginning of the work; Post1: after 1-h work; Post2: after 2-h work.; Post3: after 3-h work.; Post4: after 4-h work. D: the average difference between before and after experimental tasks. D% ¼ {(PostAPre)/Pre} 100, Where Pre is the initial circumference; cm, PostA is the circumference at time A; cm.
move their ankle and hip joints twice on the force plate, for 2 min each time. The first movement was made after the subject had been standing for 30 min: the subject wiggled his toes (ankle movement) or lifted his feet (hip movement) for 2 min within the perimeter of the force plate; he then stood for 1 min, before performing the second movement (ankle or hip) for another 2 min. The period of the movement cycle was approximately 2 s. During the rest period, subjects sat, and had no posture restrictions. Fig. 1 presents the ankle and hip movements. The circumferences of the thigh and shank were measured at the start of each session and after the subject had stood for 50 min. The subjects then completed a questionnaire. The same pressure was always applied by the measuring tape to the measured area to minimize errors that were caused by traction and the compression of the soft tissue. The circumferences of the thigh and shank were measured at their mid points, and a colored pen was used to mark the measurement site; all measurements were made in triplicate. No subject practiced before the experiment. The order in which each subject performed each of the three movements was randomly assigned.
2.5. Data analysis All analyses were performed in SPSS Release 11.5.0 (SPSS Institute Inc, 2002). First, descriptive statistics were calculated for all of the variables. The following formula (Chester et al., 2002) was used to determine change in circumference.
DC% ¼ fðCA C0 Þ=C0 g 100%; where C0 is the initial circumference (in cm) and CA is the circumference (in cm) at time A. Next, repeated-measures analysis of variance (ANOVA) was performed for each dependent variable to test whether the foot activities or standing duration significantly affected any measure. All subjective ratings were subjected to nonparametric KruskaleWallis analysis. Post hoc multiple-range tests were performed to compare values of relevant variables whenever a factor was found to be statistically significant at the a ¼ 0.05 level.
3. Results Table 1 showed the means and standard deviations of the circumferences of the thigh and shank, measured at the start of the 4 h standing period and after each hour of standing. The circumference of the lower extremity increased steadily during the first hour, and increased slightly or nearly as much after the first hour and after the second hour under all three conditions of motion. An absence of movement was associated with the largest mean increase in thigh circumference (0.55 cm) and the largest average percentage increase in shank circumference (1.26%) over 4 h. The mean changes in thigh circumference (0.28 cm; 0.56%) and shank circumference (0.43 cm; 1.13%) associated with ankle movement and those (0.33 cm; 0.66% and 0.23 cm; 0.60%, respectively) associated with hip movement during a period of prolonged standing were also obtained. The repeated-measures ANOVA results shown in Table 2 revealed that both the leg movement and measurement time after the subject began to stand significantly influenced the difference between the measured thigh circumference and shank circumference. The interaction between leg movement and measurement time was significant for shank circumference but not thigh circumference. To determine which leg movements significantly affected collective foot swelling, a multiple-range test using LSD was performed. Figs. 2and 3 presented the results of such tests. This grouping comparison revealed that ankle movement and hip movement reduced the increase in thigh circumference below that observed without movement, but no significant difference existed between ankle movement and hip movement (Fig. 2). Additionally, the results of the grouping comparison revealed that ankle movement and no movement increased shank circumference more than did hip movement, and that ankle movement and no movement resulted in shank circumferences that did not differ significantly (Fig. 3). Mean changes were compared using LSD multiple-range tests to determine if prolonged standing time significantly affected collective foot swelling alone. The grouping indicated that the percentage changes in thigh and shank circumference during the first hour of standing was more than that during the second, third
Table 2 Summary of factorial analysis of variance (ANOVA) in this study. Performance measure
Thigh circumference Shank circumference **p < 0.01.
Leg movement
Leg movement Measure time
Measure time
F
P
F
P
F
P
13.65 80.79
0.000** 0.000**
32.88 27.00
0.000** 0.000**
1.19 12.67
0.312 0.000**
Mean circumference changes (cm)
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Y.-H. Lin et al. / Applied Ergonomics 43 (2012) 1033e1037
0.6
KruskaleWallis analysis (Table 4). The effects of measurement time on the subjective rating of discomfort of the thigh and shank were significant, and leg movement significantly affected the change in shank discomfort, but not the change in thigh discomfort. A correlation analysis was performed to examine the relationships between subjective discomfort ratings and objective variables that were thought to be related to standing discomfort. A significant positive correlation existed between change in shank circumference and subjective discomfort of the shank (Pearson correlation coefficient, R ¼ 0.55, p < 0.01), but the change in thigh circumference was uncorrelated with subjective discomfort of the thigh at an a of <0.05.
0.5 0.4 0.3 0.2 0.1 0.0
No movement
Hip movement
Ankle movement
4. Discussion Grouping
Mean circumference changes (cm)
Fig. 2. Mean thigh circumference changes and significance grouping as a function of experimental leg movements.
0.6 0.5 0.4 0.3 0.2 0.1 0.0
No movement
Ankle movement
Hip movement
Grouping Fig. 3. Mean shank circumference changes and significance grouping as a function of experimental leg movements.
and fourth hours, and that the differences among the changes in circumferences in the second, third and fourth hours were not significantly different. Each subject rated discomfort in two parts of their lower extremities at the end of each hour of the 4 h testing period. Table 3 showed the discomfort ratings after 50 min under the three conditions on a scale of 1e7, where 7 means “extremely uncomfortable”. The discomfort increased over time from 2.5 to 5.8. The absence of movement during the 4 h testing period caused the most discomfort in the shank (5.8) when ankle movement caused the most discomfort in the thigh (5.0). The variations in the subjective ratings of thigh and shank discomfort were analyzed by the nonparametric
In most industrialized countries, increasing emphasis was being placed on ergonomic interventions to reduce worker discomfort. Since many workers stood for long periods during their work day, interventions to improve worker fitness and the work environment were critical to promoting the health, safety, and comfort of workers. The restriction of blood flow to lower extremities that was caused by long periods of standing had been posited to be related to venous insufficiencies and leg fatigue (Ryan, 1989; Krijnen et al., 1996; Madeleine et al., 1998). Many studies had recorded shank circumference and foot dimensions as indirect measures of leg swelling (Hansen et al., 1998; Madeleine et al., 1998; Cham and Redfern, 2001). The results of this study suggested that leg movements could influence standing comfort, as quantified either subjectively or by changed in leg circumference. Thigh and shank circumferences increased during prolonged standing on a hard surface in a 4 h shift (Table 1). The results revealed some interesting trends: the largest increase in leg circumference was recorded without any movement during the standing period. One possible cause of the larger increased in swelling under this condition than under either of the other two conditions of leg movement were that restricted movement of the lower body allows no muscle activity, causing venous blood pooling. Additionally, both ankle and hip movements inhibited oedema formation in the lower extremities. Similarly, Hansen et al. (1998) found significant differences between the degrees of foot swelling associated with two simulated tasks, and they found that a combination of standing/walking tasks reduced foot swelling by 50% below that associated with standing tasks alone. Additionally, hip movement reduced the increase in mean shank circumference (0.23 cm) that occurs during long periods of standing, but the measurement time had no significant effect when either ankle movement (0.43 cm) or no movement (0.48 cm) was made. Therefore, the data in Fig. 3 revealed that hip movement reduced shank swelling more than did ankle movement or no movement. Work that allowed a large
Table 3 Means and standard deviations of subjective rating of discomfort, and their changes (% change) for three leg movement strategies used during a period of prolonged standing. Without any movement Thigh
Post1 Post2 Post3 Post4 Mean
Ankle movement Shank
Thigh
Hip movement Shank
Thigh
Shank
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
2.5(1.1) 3.4(0.7) 4.2(1.2) 4.6(1.3) 3.7(1.3)
e 0.9(36.0) 1.7(68.0) 2.1(84.0) 1.2(48.0)
3.5(1.4) 4.4(1.5) 5.3(1.3) 5.8(0.9) 4.8(1.5)
e 0.9(25.7) 1.8(51.4) 2.3(65.7) 1.3(37.1)
2.8(1.1) 3.8(1.3) 4.4(1.1) 5.0(1.2) 4.0(1.4)
e 1.0(35.7) 1.6(57.1) 2.2(78.6) 1.2(42.9)
2.7(1.2) 3.4(1.5) 4.0(1.6) 4.9(1.9) 3.8(1.7)
e 0.7(25.9) 1.3(48.1) 2.2(81.5) 1.1(40.7)
2.6(1.0) 3.4(0.8) 4.0(0.8) 4.7(0.9) 3.7(1.2)
e 0.8(30.8) 1.4(53.8) 2.1(80.8) 1.1(42.3)
2.5(1.1) 2.9(1.4) 3.6(1.5) 4.4(1.3) 3.4(1.5)
e 0.4(16.0) 1.1(44.0) 1.9(76.0) 0.9(36.0)
Note. Post1: after 1-h work; Post2: after 2-h work.; Post3: after 3-h work.; Post4: after 4-h work. D: the average difference between before and after experimental tasks; D% ¼ {(PostAPost1)/Post1} 100, Where Post1 is the discomfort rating after 1-h work; PostA is the discomfort rating after 2-h work, 3-h work, and 4-h work, respectively.
Y.-H. Lin et al. / Applied Ergonomics 43 (2012) 1033e1037 Table 4 Summary of subjective discomfort ratings for nonparametric KruskaleWallis analysis. Performance measure
Leg movement Chi-square
Subjective rating of thigh discomforts Subjective rating of shank discomforts
1.80 13.70
Measure time P
Chi-square
P
0.407
42.48
0.000**
0.001**
30.11
0.000**
**p < 0.01.
variation in the activity of the feet and leg might therefore cause the least discomfort. Another important finding was that extensive movement of the ankle and hip while standing might significantly inhibit the formation of oedemas. This study found that the effect of leg movement on standing discomfort or measured of swelling of the lower extremities might be enough to enable the detection of statistically significant difference between the effects of leg movements during the first 2 h of standing. Such movements were expected to cause dynamic squeezing of the foot tissues, including the venous plexus in the plantar and the lymph vessels (Hansen et al., 1998). To obtain objective measures of the effects of prolonged standing, the correlations between these measures and subjective measures was useful (Redfern and Cham, 2000). The significance of the relationships identified between subjective discomfort ratings and objective variables (such as shank circumference) confirmed that discomfort associated with prolonged standing was not only a subjective feeling but also quantifiable using physiological variables. In this study, increased in discomfort were associated with increased in shank circumference. However, a fundamental physiological question remained unanswered since, for example, this study identified no significant relationship between subjective discomfort ratings and changed in thigh circumference that was similar to those found by Hansen et al. (1998) and Cham and Redfern (2001). Additionally, the findings of this study contradicted those of Chester et al. (2002), who suggested that increased calf circumference was associated with higher subjective discomfort. A possible explanation for the lack of a significant relationship between changed in thigh circumference and ratings of discomfort was that sustained tonic muscle contraction in the lower limb without movement condition increased reported discomfort. Since the effectiveness of leg movement in preventing discomfort was confirmed herein, determining whether the workers favored the moving of their legs and whether a change in the duration or frequency of leg movement during standing was favorable, would be of great value. Unfortunately, the data from this study cannot answer that question. Therefore, further studies are needed. One limitation of this study concerned the movement strategies: participants were instructed to ensure that their hip movement elicited knee movement, albeit passively in most cases.
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This condition should be taken into consideration in future research. Another limitation of this study that concerned the applicability of the data to a wide range of industries was the fact that subjects did not wear shoes. While this approach prevents the characteristics of shoes from affecting results, future studies should consider standardizing footwear or making footwear an experimental variable. 5. Conclusions The venous pump mechanism depended upon the phasic activity of muscles in the legs, which helped pump the venous blood back toward the heart. Making various leg movements caused ten subjects in standing work situations in the laboratory to report less discomfort and swelling in their lower extremities. This study suggested that workers should move their legs for a short period following prolonged standing for 30 min, to reduce the discomfort and swelling of lower extremities. References Bridger, R.S., 2009. Introduction to Ergonomics, third ed. Taylor & Francis, NW. Cham, R., Redfern, M.S., 2001. Effect of flooring on standing comfort and fatigue. Hum. Factors 43, 381e391. Chester, M.R., Rys, M.J., Konz, S.A., 2002. Leg swelling, comfort and fatigue when sitting, standing, and sit/standing. Int. J. Ind. Ergon. 29, 289e296. Chiu, M.C., Wang, M.J.J., 2007. Professional footwear evaluation for clinical nurses. Appl. Ergon. 38, 133e141. Cook, J., Branch, T.P., Baranowski, T.J., Hutton, W.C., 1993. The effect of surgical floor mats in prolonged standing: an EMG study of the lumbar paraspinal and anterior tibialis muscles. J. Biomed. Eng. 15, 247e250. Hansen, L., Winkel, J., Jorgensen, K., 1998. Significance of mat and shoe softness during prolonged work in upright position: based on measurements of low back muscle EMG, foot volume changes, discomfort and ground reactions. Appl. Ergon. 29, 217e224. Hasegawa, T., Inoue, K., Tsutsue, O., Kumashiro, M., 2001. Effects of a sit-stand schedule on a light repetitive task. Int. J. Ind. Ergon. 28, 219e224. Kim, J.Y., Stuart-Buttle, C., Marras, W.S., 1994. The effects of mats on back and leg fatigue. Appl. Ergon. 25, 29e34. King, P.M., 2002. A comparison of the effects of floor mats and shoe in-soles on standing fatigue. Appl. Ergon. 33, 477e484. Krijnen, R.M.A., De Boer, E.M., Ader, H.J., Bruynzeel, D.P., 1996. Venous insufficiency in male workers with a standing profession. Part 2: diurnal volume changes of the lower legs. Dermatology 194, 121e126. Madeleine, P., Voigt, M., Arendt-Neilsen, L., 1998. Subjective, physiological and biomedical responses to prolonged manual work performed standing on hard and soft surfaces. Eur. J. Appl. Physiol. 77, 1e9. Marr, S.J., Quine, S., 1993. Shoe concerns and foot problems of wearers of safety footwear. Occup. Med. 43, 73e77. Messing, K., Kilbom, Å., 2001. Standing and very slow walking: foot pain-pressure threshold, subjective pain experience and work activity. Appl. Ergon. 32, 81e90. Redfern, M.S., Chaffin, D.B., 1995. Influence of flooring on standing fatigue. Hum. Factors 37, 570e581. Redfern, M.S., Cham, R., 2000. The influence of flooring on standing comfort and fatigue. AIHA J. 61, 700e708. Ryan, G.A., 1989. The prevalence of musculoskeletal symptoms in supermarket workers. Ergonomics 32, 359e370. SPSS Institute, Inc, 2002. SPSS User’s Guide, Release 11.5.0. Zander, J.E., King, M.P., Ezenwa, B.N., 2004. Influence of flooring conditions on lower leg volume following prolonged standing. Int. J. Ind. Ergon. 34, 279e288. Zhang, L., Drury, C., Wooley, S., 1991. Constrained standing: evaluating the foot/floor interface. Ergonomics 34, 175e192.
Contents lists available at SciVerse ScienceDirect
Applied Ergonomics journal homepage: www.elsevier.com/locate/apergo
Effectiveness of leg movement in reducing leg swelling and discomfort in lower extremities Yen-Hui Lin a, b, *, Chih-Yong Chen c, Min-Hsien Cho c a
School of Occupational Safety and Health, Chung Shan Medical University, No. 110, Sec.1, Jianguo N. Rd., Taichung City 402, Taiwan, ROC Department of Occupational Medicine, Chung Shan Medical University Hospital, Taiwan, ROC c Institute of Occupational Safety and Health, Council of Labor Affairs, Executive Yuan, Taiwan, ROC b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 19 April 2011 Accepted 5 March 2012
Various occupations required that workers stand for long periods, causing discomfort and pain. This study considered the effectiveness of three leg movements in relieving discomfort of the lower extremities during long periods of standing at work. Ten paid male subjects with no history of problems of the lower extremities were enrolled in this study. They performed three leg movements on a hard floor while standing for 4 h in a laboratory setting. Each 1 h experimental test had two phases e 50 min of standing, followed by 10 min of rest. During the period of standing, one the following leg movements was made. No movement (no change in posture), ankle movement (twice, for 2 min each time), and hip movement (twice, for 2 min each time). Observations revealed that the three leg movements yielded different degrees of lower limb swelling. The percentage changes in thigh (1.22%) and shank (1.32%) circumferences were largest during prolonged standing without any movement and lowest during prolonged standing with ankle movement (0.61%) and hip movement (0.80%). The relationship between perceived discomfort and standing time was determined. The subjects perceived the most shank discomfort (5.8) during the 4 h test without any movement. Leg movement greatly influenced perceived discomfort of the shank. The results of this study suggested that workers should move their ankles and hips for a short period following prolonged standing for 30 min to reduce lower extremity discomfort. Ó 2012 Elsevier Ltd and The Ergonomics Society. All rights reserved.
Keywords: Prolonged standing Leg movement Lower extremity circumference
1. Introduction Various workers, including supermarket checkout employees, assembly and quality control workers, and healthcare staff, are required to stand for long periods (Ryan, 1989; Cook et al., 1993; Redfern and Chaffin, 1995; Redfern and Cham, 2000; King, 2002). Many studies had found that standing for long periods is related to various health problems, including, in particular, low back pain and lower extremity discomfort (Zhang et al., 1991; Marr and Quine, 1993; Kim et al., 1994; Cham and Redfern, 2001; Chester et al., 2002). The effects of musculoskeletal disorders that were associated with prolonged standing on health insurance, absenteeism, productivity and well-being was substantial (King, 2002). Therefore, the prevention of musculoskeletal disorders that were associated with prolonged standing in the workplace has become an
* Corresponding author. School of Occupational Safety and Health, Chung Shan Medical University, No. 110, Sec.1, Jianguo N. Rd., Taichung City 402, Taiwan, ROC. Tel.: þ886 4 2473 0022x12119; fax: 886 4 23249194. E-mail address: [email protected] (Y.-H. Lin).
increasingly important concern in many industries (Zander et al., 2004). Many ergonomic interventions that were used during prolonged standing tasks, including alternation of the flooring on which workers stood, changed of posture, the provision of sit/stand chairs, and the use of in-soles in footwear, had been proposed to tackle musculoskeletal disorders (Hasegawa et al., 2001; Messing and Kilbom, 2001; King, 2002; Chiu and Wang, 2007; Bridger, 2009). However, complaints of musculoskeletal disorders that were associated with long-term standing in the workplace had not been completely eliminated. For example, many studies had studied the effect of floor type on subjective and biomechanical/physiological objective measures that were believed to be related to standing discomfort (Madeleine et al., 1998). However, investigators who were concerned with the effect of flooring on these measures had obtained conflicting results (Redfern and Cham, 2000; Zander et al., 2004). Some studies had revealed a relationship between floor type and fatigue, while others had not. Additionally, studies had established that standing work without any motion or walking caused greater musculoskeletal discomfort than a combination of standing/walking tasks (Hansen et al., 1998). However, relatively
0003-6870/$ e see front matter Ó 2012 Elsevier Ltd and The Ergonomics Society. All rights reserved. doi:10.1016/j.apergo.2012.03.002
1034
Y.-H. Lin et al. / Applied Ergonomics 43 (2012) 1033e1037
few attempts had been made to evaluate the practical effectiveness of a considerable variation in the motion of the feet and legs in tackling musculoskeletal disorders. One aim of this study is to determine if the use of three leg movement strategies during prolonged periods of standing change leg circumference and subjective discomfort ratings. Another goal is to provide to industrial personnel regarding evidence in support of ergonomic recommendations to promote health in the workplace by reducing pain or fatigue of the lower extremities during prolonged standing. 2. Materials and methods
were the fixed factors. Subjects were treated as a random factor. In the experiment, each subject performed simulated standing in the laboratory three times, each time for 4 h. During each such period, the subject intermittently performed a particular leg movement. Therefore, each subject performed a total of three 4 h tests. The response variables were a subjective rating of lower extremity discomfort and the circumferences of the thigh and shank before and after the test. Subjective ratings of lower extremity discomfort were consistent with the study of Cham and Redfern (2001): they were given on a seven-point Likert scale, ranging from 1 for “no discomfort” to 7 for “extremely uncomfortable”. The circumferences of the thigh and shank were measured at the start of each session and after 50 min of standing.
2.1. Subjects 2.4. Experimental procedure Ten paid male subjects aged 26e35 (mean, 30.2) participated in this study. Their average height was 170.9 7.3 cm and their average weight was 67.6 5.9 kg. All subjects were in good health and had no history of musculoskeletal, cardiovascular and diabetic problems. Before participation, the subjects were informed of the aims of the study, and they all participated voluntarily. 2.2. Apparatus A compatible personal computer (PC) with a 17inch TFT-LCD monitor was used in the computer-related tasks. A Gulick measuring tape was used to measure variations in the circumference of the lower extremities. This tape measure did not generate tension, and a tension meter at one end of the tape ensured that all measurements were made with equal pressure on the test area, to minimize errors that would otherwise have been caused by traction and the compression of soft tissues. Subjects were asked not to remove marks. 2.3. Experimental design An experiment was performed with a two-factor design with repeated measurements. Leg movements (no movement, ankle movement and hip movement) and measurement time (four levels)
Before the experimental session, a subject’s experimentally significant anthropometric data were measured to facilitate workstation adjustments. These covered body height, weight, eye height, and elbow height. Keyboard height at the workstation was adjusted to suit the subject’s elbow height; the monitor was placed approximately an arm’s length from each subject, and the center angle between the eye and monitor was 20 . As indicated above, each subject participated in three experimental sessions. The experimental task, performed on a computer, simulated prolonged standing tasks in a realistic work situation. The computer-related task involved netsurfing or watching movies, with no data input via the keyboard. Subjects adopted a natural stance when performing the tasks on the computer and were permitted to work at their own rhythm. Each session lasted for approximately 4 h, and each subject had a single session daily. Each 1 h period comprised of two periods e 50 min of standing followed by 10 min of rest. A force plate was used as the hard floor on which each subject stood. During each 50 min standing period, one of the following leg movements was performed. (1) No movement (no change of posture), (2) two ankle movements, and (3) two hip movements. Under condition (1) without movement, the subject’s feet were verified to be within the range of the force plate, and leg resting was discouraged. Under conditions (2) and (3), subjects were asked to
Fig. 1. Ankle (a) and hip (b) movement strategies examined during prolonged standing.
Y.-H. Lin et al. / Applied Ergonomics 43 (2012) 1033e1037
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Table 1 Means and standard deviations of thigh and shank circumferences (cm), and their changes (% change) for three leg movement strategies used during a period of prolonged standing. Without any movement Thigh
Pre Post1 Post2 Post3 Post4 Average D(D%)
Ankle movement Shank
Hip movement
Thigh
Shank
Thigh
Shank
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
49.3(2.9) 49.8(3.0) 49.8(2.9) 49.9(2.8) 49.9(2.9)
e 0.5(1.01) 0.5(1.01) 0.6(1.22) 0.6(1.22) 0.55(1.12)
37.8(2.5) 38.2(2.5) 38.3(2.5) 38.3(2.5) 38.3(2.5)
e 0.4(1.06) 0.5(1.32) 0.5(1.32) 0.5(1.32) 0.48(1.26)
49.4(3.6) 49.6(3.5) 49.7(3.6) 49.7(3.6) 49.7(3.6)
e 0.2(0.40) 0.3(0.61) 0.3(0.61) 0.3(0.61) 0.28(0.56)
37.5(2.8) 37.8(2.9) 37.9(2.9) 38.0(2.9) 38.0(2.9)
e 0.3(0.80) 0.4(1.07) 0.5(1.33) 0.5(1.33) 0.43(1.13)
49.4(3.6) 49.6(3.6) 49.7(3.6) 49.8(3.6) 49.8(3.7)
e 0.2(0.40) 0.3(0.61) 0.4(0.81) 0.4(0.81) 0.33(0.66)
37.3(2.8) 37.4(2.8) 37.5(2.8) 37.6(2.8) 37.6(2.8)
e 0.1(0.27) 0.2(0.54) 0.3(0.80) 0.3(0.80) 0.23(0.60)
Note: Pre: beginning of the work; Post1: after 1-h work; Post2: after 2-h work.; Post3: after 3-h work.; Post4: after 4-h work. D: the average difference between before and after experimental tasks. D% ¼ {(PostAPre)/Pre} 100, Where Pre is the initial circumference; cm, PostA is the circumference at time A; cm.
move their ankle and hip joints twice on the force plate, for 2 min each time. The first movement was made after the subject had been standing for 30 min: the subject wiggled his toes (ankle movement) or lifted his feet (hip movement) for 2 min within the perimeter of the force plate; he then stood for 1 min, before performing the second movement (ankle or hip) for another 2 min. The period of the movement cycle was approximately 2 s. During the rest period, subjects sat, and had no posture restrictions. Fig. 1 presents the ankle and hip movements. The circumferences of the thigh and shank were measured at the start of each session and after the subject had stood for 50 min. The subjects then completed a questionnaire. The same pressure was always applied by the measuring tape to the measured area to minimize errors that were caused by traction and the compression of the soft tissue. The circumferences of the thigh and shank were measured at their mid points, and a colored pen was used to mark the measurement site; all measurements were made in triplicate. No subject practiced before the experiment. The order in which each subject performed each of the three movements was randomly assigned.
2.5. Data analysis All analyses were performed in SPSS Release 11.5.0 (SPSS Institute Inc, 2002). First, descriptive statistics were calculated for all of the variables. The following formula (Chester et al., 2002) was used to determine change in circumference.
DC% ¼ fðCA C0 Þ=C0 g 100%; where C0 is the initial circumference (in cm) and CA is the circumference (in cm) at time A. Next, repeated-measures analysis of variance (ANOVA) was performed for each dependent variable to test whether the foot activities or standing duration significantly affected any measure. All subjective ratings were subjected to nonparametric KruskaleWallis analysis. Post hoc multiple-range tests were performed to compare values of relevant variables whenever a factor was found to be statistically significant at the a ¼ 0.05 level.
3. Results Table 1 showed the means and standard deviations of the circumferences of the thigh and shank, measured at the start of the 4 h standing period and after each hour of standing. The circumference of the lower extremity increased steadily during the first hour, and increased slightly or nearly as much after the first hour and after the second hour under all three conditions of motion. An absence of movement was associated with the largest mean increase in thigh circumference (0.55 cm) and the largest average percentage increase in shank circumference (1.26%) over 4 h. The mean changes in thigh circumference (0.28 cm; 0.56%) and shank circumference (0.43 cm; 1.13%) associated with ankle movement and those (0.33 cm; 0.66% and 0.23 cm; 0.60%, respectively) associated with hip movement during a period of prolonged standing were also obtained. The repeated-measures ANOVA results shown in Table 2 revealed that both the leg movement and measurement time after the subject began to stand significantly influenced the difference between the measured thigh circumference and shank circumference. The interaction between leg movement and measurement time was significant for shank circumference but not thigh circumference. To determine which leg movements significantly affected collective foot swelling, a multiple-range test using LSD was performed. Figs. 2and 3 presented the results of such tests. This grouping comparison revealed that ankle movement and hip movement reduced the increase in thigh circumference below that observed without movement, but no significant difference existed between ankle movement and hip movement (Fig. 2). Additionally, the results of the grouping comparison revealed that ankle movement and no movement increased shank circumference more than did hip movement, and that ankle movement and no movement resulted in shank circumferences that did not differ significantly (Fig. 3). Mean changes were compared using LSD multiple-range tests to determine if prolonged standing time significantly affected collective foot swelling alone. The grouping indicated that the percentage changes in thigh and shank circumference during the first hour of standing was more than that during the second, third
Table 2 Summary of factorial analysis of variance (ANOVA) in this study. Performance measure
Thigh circumference Shank circumference **p < 0.01.
Leg movement
Leg movement Measure time
Measure time
F
P
F
P
F
P
13.65 80.79
0.000** 0.000**
32.88 27.00
0.000** 0.000**
1.19 12.67
0.312 0.000**
Mean circumference changes (cm)
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0.6
KruskaleWallis analysis (Table 4). The effects of measurement time on the subjective rating of discomfort of the thigh and shank were significant, and leg movement significantly affected the change in shank discomfort, but not the change in thigh discomfort. A correlation analysis was performed to examine the relationships between subjective discomfort ratings and objective variables that were thought to be related to standing discomfort. A significant positive correlation existed between change in shank circumference and subjective discomfort of the shank (Pearson correlation coefficient, R ¼ 0.55, p < 0.01), but the change in thigh circumference was uncorrelated with subjective discomfort of the thigh at an a of <0.05.
0.5 0.4 0.3 0.2 0.1 0.0
No movement
Hip movement
Ankle movement
4. Discussion Grouping
Mean circumference changes (cm)
Fig. 2. Mean thigh circumference changes and significance grouping as a function of experimental leg movements.
0.6 0.5 0.4 0.3 0.2 0.1 0.0
No movement
Ankle movement
Hip movement
Grouping Fig. 3. Mean shank circumference changes and significance grouping as a function of experimental leg movements.
and fourth hours, and that the differences among the changes in circumferences in the second, third and fourth hours were not significantly different. Each subject rated discomfort in two parts of their lower extremities at the end of each hour of the 4 h testing period. Table 3 showed the discomfort ratings after 50 min under the three conditions on a scale of 1e7, where 7 means “extremely uncomfortable”. The discomfort increased over time from 2.5 to 5.8. The absence of movement during the 4 h testing period caused the most discomfort in the shank (5.8) when ankle movement caused the most discomfort in the thigh (5.0). The variations in the subjective ratings of thigh and shank discomfort were analyzed by the nonparametric
In most industrialized countries, increasing emphasis was being placed on ergonomic interventions to reduce worker discomfort. Since many workers stood for long periods during their work day, interventions to improve worker fitness and the work environment were critical to promoting the health, safety, and comfort of workers. The restriction of blood flow to lower extremities that was caused by long periods of standing had been posited to be related to venous insufficiencies and leg fatigue (Ryan, 1989; Krijnen et al., 1996; Madeleine et al., 1998). Many studies had recorded shank circumference and foot dimensions as indirect measures of leg swelling (Hansen et al., 1998; Madeleine et al., 1998; Cham and Redfern, 2001). The results of this study suggested that leg movements could influence standing comfort, as quantified either subjectively or by changed in leg circumference. Thigh and shank circumferences increased during prolonged standing on a hard surface in a 4 h shift (Table 1). The results revealed some interesting trends: the largest increase in leg circumference was recorded without any movement during the standing period. One possible cause of the larger increased in swelling under this condition than under either of the other two conditions of leg movement were that restricted movement of the lower body allows no muscle activity, causing venous blood pooling. Additionally, both ankle and hip movements inhibited oedema formation in the lower extremities. Similarly, Hansen et al. (1998) found significant differences between the degrees of foot swelling associated with two simulated tasks, and they found that a combination of standing/walking tasks reduced foot swelling by 50% below that associated with standing tasks alone. Additionally, hip movement reduced the increase in mean shank circumference (0.23 cm) that occurs during long periods of standing, but the measurement time had no significant effect when either ankle movement (0.43 cm) or no movement (0.48 cm) was made. Therefore, the data in Fig. 3 revealed that hip movement reduced shank swelling more than did ankle movement or no movement. Work that allowed a large
Table 3 Means and standard deviations of subjective rating of discomfort, and their changes (% change) for three leg movement strategies used during a period of prolonged standing. Without any movement Thigh
Post1 Post2 Post3 Post4 Mean
Ankle movement Shank
Thigh
Hip movement Shank
Thigh
Shank
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
M(SD)
D(D%)
2.5(1.1) 3.4(0.7) 4.2(1.2) 4.6(1.3) 3.7(1.3)
e 0.9(36.0) 1.7(68.0) 2.1(84.0) 1.2(48.0)
3.5(1.4) 4.4(1.5) 5.3(1.3) 5.8(0.9) 4.8(1.5)
e 0.9(25.7) 1.8(51.4) 2.3(65.7) 1.3(37.1)
2.8(1.1) 3.8(1.3) 4.4(1.1) 5.0(1.2) 4.0(1.4)
e 1.0(35.7) 1.6(57.1) 2.2(78.6) 1.2(42.9)
2.7(1.2) 3.4(1.5) 4.0(1.6) 4.9(1.9) 3.8(1.7)
e 0.7(25.9) 1.3(48.1) 2.2(81.5) 1.1(40.7)
2.6(1.0) 3.4(0.8) 4.0(0.8) 4.7(0.9) 3.7(1.2)
e 0.8(30.8) 1.4(53.8) 2.1(80.8) 1.1(42.3)
2.5(1.1) 2.9(1.4) 3.6(1.5) 4.4(1.3) 3.4(1.5)
e 0.4(16.0) 1.1(44.0) 1.9(76.0) 0.9(36.0)
Note. Post1: after 1-h work; Post2: after 2-h work.; Post3: after 3-h work.; Post4: after 4-h work. D: the average difference between before and after experimental tasks; D% ¼ {(PostAPost1)/Post1} 100, Where Post1 is the discomfort rating after 1-h work; PostA is the discomfort rating after 2-h work, 3-h work, and 4-h work, respectively.
Y.-H. Lin et al. / Applied Ergonomics 43 (2012) 1033e1037 Table 4 Summary of subjective discomfort ratings for nonparametric KruskaleWallis analysis. Performance measure
Leg movement Chi-square
Subjective rating of thigh discomforts Subjective rating of shank discomforts
1.80 13.70
Measure time P
Chi-square
P
0.407
42.48
0.000**
0.001**
30.11
0.000**
**p < 0.01.
variation in the activity of the feet and leg might therefore cause the least discomfort. Another important finding was that extensive movement of the ankle and hip while standing might significantly inhibit the formation of oedemas. This study found that the effect of leg movement on standing discomfort or measured of swelling of the lower extremities might be enough to enable the detection of statistically significant difference between the effects of leg movements during the first 2 h of standing. Such movements were expected to cause dynamic squeezing of the foot tissues, including the venous plexus in the plantar and the lymph vessels (Hansen et al., 1998). To obtain objective measures of the effects of prolonged standing, the correlations between these measures and subjective measures was useful (Redfern and Cham, 2000). The significance of the relationships identified between subjective discomfort ratings and objective variables (such as shank circumference) confirmed that discomfort associated with prolonged standing was not only a subjective feeling but also quantifiable using physiological variables. In this study, increased in discomfort were associated with increased in shank circumference. However, a fundamental physiological question remained unanswered since, for example, this study identified no significant relationship between subjective discomfort ratings and changed in thigh circumference that was similar to those found by Hansen et al. (1998) and Cham and Redfern (2001). Additionally, the findings of this study contradicted those of Chester et al. (2002), who suggested that increased calf circumference was associated with higher subjective discomfort. A possible explanation for the lack of a significant relationship between changed in thigh circumference and ratings of discomfort was that sustained tonic muscle contraction in the lower limb without movement condition increased reported discomfort. Since the effectiveness of leg movement in preventing discomfort was confirmed herein, determining whether the workers favored the moving of their legs and whether a change in the duration or frequency of leg movement during standing was favorable, would be of great value. Unfortunately, the data from this study cannot answer that question. Therefore, further studies are needed. One limitation of this study concerned the movement strategies: participants were instructed to ensure that their hip movement elicited knee movement, albeit passively in most cases.
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This condition should be taken into consideration in future research. Another limitation of this study that concerned the applicability of the data to a wide range of industries was the fact that subjects did not wear shoes. While this approach prevents the characteristics of shoes from affecting results, future studies should consider standardizing footwear or making footwear an experimental variable. 5. Conclusions The venous pump mechanism depended upon the phasic activity of muscles in the legs, which helped pump the venous blood back toward the heart. Making various leg movements caused ten subjects in standing work situations in the laboratory to report less discomfort and swelling in their lower extremities. This study suggested that workers should move their legs for a short period following prolonged standing for 30 min, to reduce the discomfort and swelling of lower extremities. References Bridger, R.S., 2009. Introduction to Ergonomics, third ed. Taylor & Francis, NW. Cham, R., Redfern, M.S., 2001. Effect of flooring on standing comfort and fatigue. Hum. Factors 43, 381e391. Chester, M.R., Rys, M.J., Konz, S.A., 2002. Leg swelling, comfort and fatigue when sitting, standing, and sit/standing. Int. J. Ind. Ergon. 29, 289e296. Chiu, M.C., Wang, M.J.J., 2007. Professional footwear evaluation for clinical nurses. Appl. Ergon. 38, 133e141. Cook, J., Branch, T.P., Baranowski, T.J., Hutton, W.C., 1993. The effect of surgical floor mats in prolonged standing: an EMG study of the lumbar paraspinal and anterior tibialis muscles. J. Biomed. Eng. 15, 247e250. Hansen, L., Winkel, J., Jorgensen, K., 1998. Significance of mat and shoe softness during prolonged work in upright position: based on measurements of low back muscle EMG, foot volume changes, discomfort and ground reactions. Appl. Ergon. 29, 217e224. Hasegawa, T., Inoue, K., Tsutsue, O., Kumashiro, M., 2001. Effects of a sit-stand schedule on a light repetitive task. Int. J. Ind. Ergon. 28, 219e224. Kim, J.Y., Stuart-Buttle, C., Marras, W.S., 1994. The effects of mats on back and leg fatigue. Appl. Ergon. 25, 29e34. King, P.M., 2002. A comparison of the effects of floor mats and shoe in-soles on standing fatigue. Appl. Ergon. 33, 477e484. Krijnen, R.M.A., De Boer, E.M., Ader, H.J., Bruynzeel, D.P., 1996. Venous insufficiency in male workers with a standing profession. Part 2: diurnal volume changes of the lower legs. Dermatology 194, 121e126. Madeleine, P., Voigt, M., Arendt-Neilsen, L., 1998. Subjective, physiological and biomedical responses to prolonged manual work performed standing on hard and soft surfaces. Eur. J. Appl. Physiol. 77, 1e9. Marr, S.J., Quine, S., 1993. Shoe concerns and foot problems of wearers of safety footwear. Occup. Med. 43, 73e77. Messing, K., Kilbom, Å., 2001. Standing and very slow walking: foot pain-pressure threshold, subjective pain experience and work activity. Appl. Ergon. 32, 81e90. Redfern, M.S., Chaffin, D.B., 1995. Influence of flooring on standing fatigue. Hum. Factors 37, 570e581. Redfern, M.S., Cham, R., 2000. The influence of flooring on standing comfort and fatigue. AIHA J. 61, 700e708. Ryan, G.A., 1989. The prevalence of musculoskeletal symptoms in supermarket workers. Ergonomics 32, 359e370. SPSS Institute, Inc, 2002. SPSS User’s Guide, Release 11.5.0. Zander, J.E., King, M.P., Ezenwa, B.N., 2004. Influence of flooring conditions on lower leg volume following prolonged standing. Int. J. Ind. Ergon. 34, 279e288. Zhang, L., Drury, C., Wooley, S., 1991. Constrained standing: evaluating the foot/floor interface. Ergonomics 34, 175e192.