Evaluating the biomechanics of an in-between posture to create a multi-posture office environment

Abstract

BACKGROUND:

Prolonged sitting during work is common and has been shown to cause health issues. However, changing working postures has been reported to reduce musculoskeletal issues and impact other health issues; thus, there is a need for an office environment with multiple choices of working postures.

OBJECTIVE:

The purpose of this study was to evaluate changes in body position, body loading, and blood perfusion while in a seated, standing, and new office seating position, termed the in-between position.

METHODS:

Ground reaction forces, joint angles, pelvic tilt, openness angle (angle between the pelvis plane and thorax), and blood perfusion were evaluated for three positions. A motion capture system with markers was used to capture the position of anatomical landmarks. A six-axis force plate was used to collect the ground reaction forces, and a laser doppler perfusion monitor was used to obtain the blood perfusion.

RESULTS:

Data showed that the in-between position articulated the hips, which provided a hip and lumbar position closer to a standing posture than a seated posture. The average vertical ground reaction force in the in-between position was larger than the seated position but significantly smaller than during standing (p < 0.0001). There were no significant differences in anterior/posterior ground reaction forces between the seated and the in-between positions (p = 0.4934). Lastly, blood perfusion increased during the dynamic transitions between positions indicating changes in blood flow.

CONCLUSION:

The in-between position provides benefits of both standing (larger pelvic tilt and increased lumbar lordosis) and sitting (reduction in ground reaction forces).

Keywords

Musculoskeletal diseases hip joint knee joint posture

1. Introduction

Extended periods of time in the seated position are common among office workers. In the United States, studies indicated that most working individuals sat at a workstation for more than four hours a day, while some workers spent as many as eleven hours in a seated position [1, 2]. Such long working hours while in a seated position can pose various health risks such as musculoskeletal disorders and pain in the neck, shoulders, upper and lower back [3]. Maintaining a kyphotic spinal posture (or flexed, slouched position) for prolonged periods as opposed to a lordotic posture has been shown to produce increased pressure in the intervertebral discs, particularly of the lumbar region and contributed to the degeneration of these discs [4]. Extended time in the seated position has also been linked to reduced blood flow and blood pooling in the legs, which is particularly problematic because blood flow is critical to maintaining the health of tissues and mental alertness [5, 6] So, to reduce pain, blood pooling and musculoskeletal disorders, research has suggested that office workers vary their posture throughout the workday [7 –10].

Sit-to-stand desks have been introduced at many workplaces in an attempt to offer another working posture besides the seated position. The goal of the standing desk is to positively influence employee cardiovascular and metabolic health outcomes by decreasing employee sitting time [11, 12]. The musculoskeletal and health benefits of sit-stand desks come from transitioning periodically between the seated and standing postures [13, 14]. However, much like prolonged sitting, prolonged standing has also been shown to have negative health implications. Muscles and joints are subjected to large loads during standing, which can result in fatigue, lower back pain, discomfort in the neck and shoulders, and musculoskeletal disorders [14 –20]. Research has shown that, much like prolonged sitting, prolonged standing can also lead to blood pooling and swelling in the lower legs [10 , 21–23]. Therefore, the authors hypothesized that introducing a different posture that supported working, in addition to the seated and standing positions, would yield different joint angles, different pelvic tilts and lumbar curvatures in comparison to seated and standing positions.

Research has shown that changing one’s posture is important for decreasing health risks, promoting blood flow, and mental alertness [5 , 25]. A multi-posture office environment has the potential to foster some movement and thereby possibly reduce some health risks associated with standard sitting. Due to the discomforts of sitting in a single posture, the necessity for a chair to support multiple postures has also been recognized by the ergonomics community [26]. Various developments and suggestions in chair designs have been made to promote movements while sitting. These include an adjustable back recline, armrests, a lumbar support and a resting feature (tilting of the whole body rearward, yielding a position with elevated feet) [27]. Researchers also tried to incorporate an inclined wedge and blocks in the seat pan to support a lordotic seating posture [28]. Similarly, the use of medial-lateral seat pan tilt has been explored in the office industry [29]. A truly multi-posture office environment requires more than just the seated and standing positions [30].

One of the notable alternative postures suggested by the literature is an elevated, seated position with a forward tilting seat pan [31 –35]. Commercially available modern chairs generally have a seat pan angle of three degrees below horizontal (the buttocks portion of the seat pan is tilted three degrees below horizontal while the occupant is positioned in an upright posture). This rearward tilt in the seat pan was shown to make forward bending tasks difficult [31]. Some researchers tried forward tilting of the seat pan. The forward seat pan tilt produced mixed results, particularly when evaluating if changes occurred with the lumbar spine, which has been used as a metric of back health [32 –34]. A perching posture where the person was seated on a high stool was an alternative suggested in the literature [36]. The person leaned against a seat pan (no back support) while keeping their legs extended and knees straight. The researchers suggested the use of this perching stool may induce movements while working at a desk [36]. Noguchi et. al. tested a variety of positions moving from seated to standing and suggested a range of torso to thigh angles that provided significant differences in muscle activation and ground reaction forces in a lab setting [35]. Even though there were differences in the techniques and reported findings from these prior studies, one thing that was consistent was the attempt to introduce additional postures into the office environment besides standing and the traditional seated position. This was done to help address the challenges seen with working in a single position for a prolonged period of time.

The purpose of this study was to investigate a new “in-between” position. This new working posture falls between the fully seated or fully standing positions. The chair that provided this in-between posture raised and tilted the seat pan forward, which permitted the occupant to keep their knees flexed and feet flat on the floor. The seat pan of the chair was also split into anterior and posterior halves so that the forward tilt of the anterior portion of the seat was larger than the forward tilt of the posterior portion of the seat, a novel feature compared to the forward tilting chairs used in the published literature [33, 35]. The authors’ primary hypothesis was that the in-between position would produce a larger pelvic tilt and therefore larger lumbar lordosis in comparison to a typical seated position. Additionally, this would occur without increased ground reaction forces as compared to the seated position. Moreover, it was hypothesized that the movement from the seated to the in-between position and the movement from the in-between to the standing position would result in a measurable change in blood perfusion in the lower legs. Therefore, the objectives of this work were: 1) to evaluate the differences in joint angles, ground reaction forces, and blood perfusion while in a seated position, a standing position, and a new office seating position, termed the in-between position and 2) to evaluate the joint moments and blood perfusion during the transition from the seated to the in-between position and the transition from the in-between position to the standing position. The moments at each joint correlate to the loading that the joints are subjected to due to the rotational effects of force. These moments are important to consider because the presence of larger joint moments can make the movement task difficult or painful, especially for people with underlying health conditions.

2. Methods

2.1. Force data

A six-axis force plate (Bertec, Colombus, OH, USA) was used to measure ground reaction forces in three directions (superior-inferior or normal force, anterior-posterior, and medial-lateral shear forces) for all test trials. Force data were collected at 100 Hz, and the plate was located under the participant’s feet for all test conditions.

2.2. Motion data

The positions of bony landmarks were identified using passive, reflective markers and an eleven-camera motion capture system with an accuracy to within 1 mm (Qualisys, Gothenburg, Sweden). The markers were attached on the right side of the body and included the 2^nd toe (2^nd metatarsal), ankle (lateral malleolus), knee (lateral epicondyle), greater trochanter, shoulder (glenohumeral joint), left and right anterior superior iliac spines (ASISs), and left and right posterior superior iliac spines (PSISs), as shown in Fig. 1. A marker pod with four markers was attached to the sternum. Two rectangular openings were made in the backrest of the chair used in this study to allow the markers on the PSISs to be visible while in the seated and in-between positions (Fig. 2). The backrest was reinforced to maintain the same support as it had before the holes were cut. Motion data were also collected at 100 Hz and were synchronized with the force data.

Fig. 1

Demonstration of the three different postures: seated posture (left), in-between posture (middle) and standing posture (right). In the in-between posture, the seat pan angle was 5 degrees forward. The markers used for calculations are indicated by the white circles.

Fig. 2

Two equivalent openings were made in the backrest of the chair to allow the markers on PSIS (circled) to be visible while in the seated and in-between postures. This permitted calculation of pelvic tilt. The backrest mesh was reinforced so that the openings did not affect the support of the backrest.

2.3. Blood perfusion

A laser doppler perfusion monitoring system (PF 5010 LDPM Unit, Perimed, Järfälla, Sweden) was used to obtain blood perfusion measurements on the lateral side of the right lower leg at the point of the largest circumference in the gastrocnemius muscle. Perfusion was quantified in perfusion units (PU).

2.4. Experimental protocol

This study was approved by Michigan State University’s Institutional Review Board, and consent was obtained from all participants. Twenty volunteers (ten males and ten females) ranging from 19 to 55 years old, with an average age of 33.6 and standard deviation of 13.37 years participated in the study. None of the volunteers had any history of neck or back pain or injury. A height adjustable table and a new chair design, which supported both seated and in-between positions, was used (Fig. 1). The participants were asked to conduct computer tasks that included re-typing a passage in the computer screen and then highlighting words in that passage with a mouse. Participants performed computer tasks in three positions across a one-hour test period: 1) seated in the chair, 2) seated in the in-between position in the chair, and 3) standing. The in-between position was such that the lower leg was vertical, the torso was vertical, and thigh-to-torso angle was between 118°-122°.The positions of the markers, ground reaction forces, and blood perfusion were collected at two time points: 5 minutes and 10 minutes in each position. The positions of the markers, ground reaction forces, and blood perfusion data were also obtained for the transition from the seated to the in-between position as well as the in-between position to standing.

The participants were positioned in an ergonomic posture by the test assistants at the start of each position, and they were asked to maintain the ergonomic posture throughout testing. In the seated position, the ankle, elbow, and hip joint were all at 90 degrees. In the standing position, the elbow and ankle angles were at 90 degrees and the hip angle at 180 degrees. In the in-between position, the torso and lower leg were situated vertically, while the participant’s thigh-to-torso angle was between 118°-122°.

2.5. Calculation of joint angles

Vectors that contained 3-D positional data from the markers on the bony landmarks were used to compute joint angles (Fig. 3). Joint angles were calculated using the two vectors parallel to the long axes of the body segments on either side of the joint in 3-D space. The cosine of the angle between two vectors was defined as the scalar product of the two vectors divided by the product of magnitudes of each vector. Joint angles were then determined by taking the inverse cosine of the scalar product of the two vectors divided by the product of magnitudes of each vector.

Fig. 3

Five joint angles were calculated. Ankle angle was the angle between foot segment and shank segment. Knee angle was the angle between shank segment and thigh segment. Hip angle was the angle between thigh segment and normal to the pelvis plane. Pelvic tilt was the angle between the pelvis plane and a horizontal plane. The pelvis plane was a plane formed by the right and left anterior-superior iliac spines and posterior-superior iliac spines. Openness angle was the angle between the pelvis plane and thorax.

The ankle angle was defined by the angle between the vectors passing through the foot (lateral malleolus and 2^nd metatarsal) and lower leg (lateral malleolus and lateral epicondyle of the knee). The knee angle was defined by the angle between the vectors passing through the thigh (lateral epicondyle and greater trochanter) and lower leg (lateral malleolus and lateral epicondyle). The hip angle was defined by the angle between the vector passing through the thigh (lateral epicondyle and greater trochanter) and a vector normal to the pelvis plane. The pelvis plane was a plane formed by the right and left anterior-superior iliac spines and posterior-superior iliac spines. Pelvic tilt was computed as the angle between the plane of the pelvis and the horizontal vector (parallel to ground).

The openness angle quantified the relative orientation of the pelvis and the ribcage and was shown to relate to lumbar curvature [37]. The openness angle was calculated by computing the angle between two vectors representing the pelvis and ribcage. The pelvis vector was defined as the vector passing through the midpoint of the two ASIS markers and the midpoint of the two PSIS markers. The ribcage vector was the vector passing through top and bottom markers of the marker pod placed on the sternum.

2.6. Calculation of joint moments

To calculate joint moments during the dynamic transitions (i.e., seated to in-between and in-between to standing), a link-segment model with four links was adopted [38]. The four segments were the HAT (head, arms, and trunk) segment, the thigh segment, the shank segment, and the foot segment (Fig. 4). The ankle, knee, and hip joints were modeled as hinge joints. Motion was only considered in the sagittal plane. Accordingly, force and moment calculations were also conducted in the sagittal plane. The anthropometric parameters, such as masses and relative locations of the centers of gravity of each body segment, were derived from literature [39]. Inverse dynamics were used to calculate the joint moments at the ankle, knee, and hip for the transitions [38]. The ankle moment was the sum of the moment due to the ground reaction force and the moment due to the weight of the feet. The knee moment was the sum of the ankle moment, the moment due to the force transferred at the ankle, and the moment due to the weight of the lower legs. The hip moment was the sum of the moment due to linear acceleration of the HAT segment, the moment due to the angular acceleration of the HAT segment, and the moment due to the weight of the HAT segment.

Fig. 4

(a) Link segment model used to calculate the joint moments. AB is head, arms and trunk (HAT), BC is thigh, CD is Shank, DE is foot segment (b) Free body diagram for foot segment (link DE), CoP is center of pressure and CoM is Center of mass (c) free body diagram for shank segment (link CD) (d) free body diagram for HAT segment (link AB).

2.7. Comfort rating

A 10-point rating scale for comfort was used for all participants [40]. After completing the computer task in each posture, the participants were asked to rate their overall comfort on a scale of 1 to 10. A rating of 1 indicated horrible and 10 was excellent. The rating of 2 and 3 indicated very bad, 4 indicated bad, 5 and 6 indicated okay, 7 indicated good and 8 and 9 indicated very good.

2.8. Statistical analysis

A repeated measures ANOVA was used to compare seated, in-between and standing positions for each of the angles (ankle angle, knee angle, hip angle, pelvic tilt and openness angle), ground reaction forces, and blood perfusion. Post-hoc Tukey tests were used to determine significant differences between specific positions. Paired t-tests were conducted to determine the significant differences in peak joint moments during the seated to in-between motion and the in-between to standing motion. A larger peak moment indicated a larger loading in the joints; therefore, a reduction in the moment was desired, especially for individuals with knee or hip injuries. A p-value<0.05 was considered statistically significant. A Wilcoxon’s signed rank test was performed on the comfort ratings to determine the differences between positions.

3. Results

3.1. Ground reaction forces

The mean vertical ground reaction forces and mean anterior-posterior ground reaction forces for the different positions are presented in Fig. 5. All the ground reaction forces were calculated as a percentage of total body weight for each of the participants. The average vertical ground reaction force was largest for the standing position and was significantly smaller in both the seated and in-between positions (p < 0.0001). The vertical forces for the in-between position were 82.9% smaller than those generated in the standing position (p < 0.0001). The anterior/posterior ground reaction forces (or shear) were small compared to normal ground reaction forces in all positions. The difference in anterior/posterior ground reaction forces between the seated and in-between positions was not statistically significant (p = 0.4934). However, there were significant differences between the anterior-posterior ground reaction forces in the in-between and standing positions (p < 0.0001) as well as between the seated and standing positions (p < 0.0001). The medial-lateral ground reaction forces were less than one percent of body weight in all three positions with no statistical differences. No statistically significant differences in ground reaction forces assessed relative to body weight were observed between males and females.

Fig. 5

Mean vertical and mean anterior-posterior ground reaction forces and standard deviation for three postures. The vertical ground reaction was larger but anterior-posterior ground reaction was smaller in the in-between posture than in seated posture. Significant differences are indicated by *.

3.2. Joint angles

The pelvic tilt angle was positive (above horizontal) at 15.3 degrees in the seated position, then the pelvic tilt value was 6.3 degrees in the in-between position (seated vs in-between: p < 0.0001), and was -8.4 degrees (below horizontal) in the standing position (in-between vs standing: p < 0.0001). These data indicated that the pelvic tilt angle changed by 58.8% when comparing the in-between position to the seated position and the pelvis movement was toward that of the standing position. The knee, hip, and openness angles were largest in the standing position and smallest in the seated position. All the angle magnitudes for the in-between position were between that of seated and standing positions. The p-values indicated that there were statistically significant differences in all pairwise comparisons (p < 0.05) between seated, in-between, and standing positions for all joint angles except for the ankle angle for the comparison of in-between vs standing (p = 0.536). All data were examined for differences between males and females. Only two statistically significant differences were identified. The ankle angle for the standing position was smaller for females (p = 0.015). Similarly, the hip angle for the standing position was also smaller for females (p = 0.035).

3.3. Joint moments

The peak joint moments at the knee and the hip were smaller during the transitions from the in-between position to the standing position compared to the joint moment values that occurred during the transitions from the seated position to the in-between position. Significant differences were seen only in the hip moment (hip: p < 0.0001, knee: p = 0.2734). The hip moment was 42% smaller during the in-between to standing motion compared to seated to in-between motion. The peak joint moment at the ankle joint was larger during the in-between to standing motion compared to the seated to in-between motion (p = 0.0001). No statistically significant differences in joint moments were observed between males and females.

Table 1
Average joint angles in degrees and standard deviation across the subject pool for each position. All the angle values for in-between position were between that of seated and standing position. * indicates means of all three positions were significantly different from each other. ^ψ indicates significant differences only for pairwise comparisons of seated and in-between, and seated and standing

Position Seated In-between Standing

Ankle Angle^ψ 101.2 (5.9) 97.3 (4.6) 93.8 (3.4)

Knee Angle* 101.1 (6.6) 111.1 (5.8) 171.7 (4.3)

Hip Angle* 116.9 (6.2) 123.0 (8.0) 169.8 (4.9)

Pelvic Tilt* 15.3 (6.6) 6.3 (6.6) –8.4 (7.6)

Openness Angle* 96.7 (15.7) 102.1 (14.0) 116.5 (17.1)

Position	Seated	In-between	Standing
Ankle Angle^ψ	101.2 (5.9)	97.3 (4.6)	93.8 (3.4)
Knee Angle*	101.1 (6.6)	111.1 (5.8)	171.7 (4.3)
Hip Angle*	116.9 (6.2)	123.0 (8.0)	169.8 (4.9)
Pelvic Tilt*	15.3 (6.6)	6.3 (6.6)	–8.4 (7.6)
Openness Angle*	96.7 (15.7)	102.1 (14.0)	116.5 (17.1)

3.4. Blood perfusion

The average blood perfusion values are presented in Table 2. There were no statistically significant differences in the average blood perfusion values between the three positions (for seated and in-between, p = 0.6402; for in between and standing, p = 0.5180; for seated and standing, p = 0.1238).

Table 2
Mean blood perfusion and standard deviation values in seated, in-between, and standing positions. Blood perfusion is defined as the concentration of red blood cells times their average velocity and is measured in perfusion units (PU). There were no statistically significant differences in blood perfusion across the three positions

Position Blood Perfusion (PU)

Seated 17.2 (9.5)

In-between 15.6 (11.4)

Standing 13.7 (11.9)

Position	Blood Perfusion (PU)
Seated	17.2 (9.5)
In-between	15.6 (11.4)
Standing	13.7 (11.9)

An example of the time trace for blood perfusion during the transition from seated to in-between position is presented in Fig. 7. Blood perfusion data were collected for the dynamic transitions from the seated to the in-between position and for the in-between to standing position. For both dynamic transitions, blood perfusion increased during the motion. It reached a maximum value and slowly decreased. For some participants, an increased perfusion level was maintained for at least one minute past the movement, which is when the data collection of blood perfusion ended.

Fig. 6

Peak joint moments with standard deviations at the ankle, knee, and hip for the two dynamic motions. Significant differences are indicated by *.

Fig. 7

An example of the blood perfusion during the dynamic movement from the seated to the in-between position for one participant. The blood perfusion values increased to a maximum value during the motion and then, for some participants, decreased to the same value as before the movement within the measurement time period of one minute. For other participants, the blood perfusion values remained elevated up through the conclusion of the one-minute data recording.

3.5. Comfort rating

The overall comfort ratings provided by the 20 participants for the positions are presented in Fig. 8. The comfort rating score ranged from 1 to 10 with 10 being the highest level of comfort. The average seated score was slightly larger than the score for the in-between position (p = 0.252). Both the seated and in-between positions were preferred over the standing position (p < 0.005). The in-between position also had the largest variation in comfort ratings. The Wilcoxon signed ranked test indicated no significant differences in comfort scores between seated and in-between positions (p = 0.252), but there were significant differences in comfort between the seated and standing positions (p < 0.001) and the in-between and standing positions (p = 0.005).

Fig. 8

Box plots of comfort ratings for each of the three postures (10 is excellent). The lower and upper ends of the box represent the interquartile range, whereas the vertical line extensions represent the largest and smallest values, excluding the outliers. The horizontal lines inside the boxes represent mean and the crosses represents median. The mean comfort rating was highest for seated posture and lowest for standing postures. In-between postures had more variation in comfort rating as compared to seated and standing postures.

4. Discussion

The goals of this study were: 1) to evaluate the differences in joint angles, ground reaction forces, and blood perfusion while in a seated position, a standing position, and a new office seating position, termed the in-between position and 2) to evaluate the joint moments and blood perfusion during the transition from the seated to the in-between position and the transition from the in-between position to the standing position. This research study was unique as it evaluated all of these parameters and compared them across three working positions. A robust set of data were collected, and a complete comparative analysis was conducted, permitting a detailed analysis of the biomechanical measures, blood perfusion and the perception of the occupant. Overall, the study found that the in-between position provided different joint angles than the seated position while transmitting smaller loads through legs than standing position. This additional in-between position demonstrated the benefits of standing (larger lumbar lordosis and pelvic tilt) as well as the seated benefits (smaller ground reaction forces). Additionally, no significant differences in shear forces at the feet were identified as a result of the seat pan tilt.

The in-between position provided pelvic orientations and lumbar curvatures closer to the standing position as compared to the seated position. It was interesting to note that the pelvis tilt in the in-between position moved to a point halfway between the pelvic tilt found in the seated and standing positions.

The increased openness angle was another measure that confirmed lumbar articulation was occurring in the in-between position, even though the person was still in the chair. Previous research has shown that a larger openness angle is correlated to an increased lordotic lumbar curvature [37]. Movement in the lumbar spine is a positive, as motion in the spine leads to promotion of nutrient flow in intervertebral discs [41]. Sitting in a lordotic or upright back posture instead of a kyphotic or slouched posture has also been associated with reduced pain in the back and leg region, as well as an increased diaphragm area, thereby providing better lung capacity and airflow [42, 43].

It should be noted that in this study, the anterior/posterior ground reaction forces were not larger in the in-between position compared to sitting. This is in contrast to a previous study where the shear forces were largest in the mid-range forward tilt posture compared to both seated and standing [35]. This prior study by Noguchi et al. evaluated the anterior posterior forces in each of the postures defined by five-degree trunk-thigh angle increments between sitting and standing with the largest anterior-posterior forces during the middle phases. Lack of large shear in the in-between position for this work is attributed to the split seat pan, which did not introduce a larger sloping surface to the buttock region but still allowed the knees to be more inferior. This has implications for future designs and research of office chairs, as this new position provides a more lordotic pelvic posture with larger lumbar curvature and minimizes the shear forces at the feet.

The use of the in-between position could also be beneficial for people with hip and knee pain, as the joint moments when standing from the in-between position demonstrated smaller values in comparison to standing from the seated position [44]. Previous research conducted on sit-stand motion indicated that an increased seat height is recommended for people who suffer from knee and hip pain. [45, 46]. Similarly, use of high stools has also been shown to reduce the joint moments [47]. The hip moment was largest for the seated to in-between motion, and this is likely a function of the control position. The participants had to lean forward in the seat to move the seat into the in-between position, which resulted in a larger moment-arm for the torso weight.

The perfusion value for both sets of transitions increased to a maximum value during the motion and then trended downward. For some participants, the perfusion value dropped to the same value as before movements within the measurement time period of one minute. For other participants, the perfusion value did not return to the initial perfusion value immediately. Rather, the blood perfusion values remained elevated until the conclusion of the data recording. This is consistent with literature, which has also shown subject dependency on perfusion values and recovery time [48]. Furthermore, for workers who cannot stand due to underlying health conditions or experience discomfort in standing, using an in-between position instead of standing can offer an additional working posture, providing an option for postural change which does not currently exist. For healthy workers, the in-between position can also serve as an additional working position.

To summarize, a chair that supports both sitting and an in-between position offers an additional solution for office workers.

4.1. Limitations

For this study, markers were attached to one side of the body only, and the posture was assumed symmetric. This could be considered a limitation of this study; however, the tasks being conducted did not involve asymmetric movements. Additionally, the order of positions was the same for all the participants. The seated position was assumed first, and the standing position was assumed last so that the blood perfusion during transitions from the seated to the in-between and the in-between to the standing positions had the same time effects. While the randomization of the position is unlikely to affect the findings related to the joint angles and joint moments, it could potentially affect the blood perfusion results and comfort ratings. Also, since the seat pan had varying inclination between the anterior and posterior regions, a future study that examines the pressure distribution on the seat pan would be an important complement to the current study. With regard to generalizing the findings of this work across the spectrum of age groups, the authors recommend that additional testing on populations younger than 19 and older than 55 should be conducted to confirm these trends in these other age groups. The authors also acknowledge that this study was conducted in a lab setting and not in an actual working space. Future studies could be of longer duration and within an office setting.

5. Conclusions

The findings from this study suggest that the in-between position comes with many positive benefits. It provided increased pelvic tilt, increased torso openness, and decreased leg loads (compared to standing). The motion to and from the in-between position also provided increased blood perfusion. The joints were subjected to smaller moments while standing from the in-between position as compared to standing from a seated position. Overall, the in-between position was rated more comfortable than standing. The in-between position has the potential to provide health benefits to the office workers by providing another working position.

Ethics statement

This study was approved by Michigan State University Institutional Review Board (number 1788). Consent was obtained from all participants.

Conflict of interest

Teresa Bellingar was employed by Haworth, which provided funding for this study. The other authors have no conflict of interest to report.

Footnotes

Acknowledgments

The authors would like to thank the members of BDRL Lab at Michigan State University.

Funding

The funding for this research work was provided by Haworth.

References

Harrington

, Barreira

, Staiano

, Katzmarzyk

The descriptive epidemiology of sitting among US adults, NHANES 2009/2010. J Sci Med Sport [Internet]. 2014;17(4)371–5. Available from: https://dx-doi-org.web.bisu.edu.cn/10.1016/j.jsams.2013.07.017.

Smith

, Hamer

, Ucci

, Marmot

, Gardner

, Sawyer

, et al. Weekday and weekend patterns of objectively measured sitting, standing, and stepping in a sample of office-based workers: The active buildings study. BMC Public Health. 2015;15(1:1–9.

Singh

, Singh

Musculoskeletal disorders among insurance office employees: A case study. Work. 2019;64, 153–60.

Pynt

, Mackey

, Higgs

Kyphosed seated postures: Extending concepts of postural health beyond the office. J Occup Rehabil. 2008;18(1):35–45.

Perrey

Promoting motor function by exercising the brain. Brain Sci. 2013;3(1):101–22.

Shvartz

, Gaume

, White

, Reibold

Hemodynamic responses during prolonged sitting. J Appl Physiol [Internet]. 1983:54(6):1673–80. Available from: https://doi.org/10.1152/jappl.1983.54.6.1673

Husemann

, Von MacH

, Borsotto

, Zepf

, Scharnbacher

Comparisons of musculoskeletal complaints and data entry between a sitting and a sit-stand workstation paradigm. Hum Factors. 2009;51(3):310–20.

Roelofs

, Straker

The experience of musculoskeletal discomfort amongst bank tellers who just sit, just stand or sit and stand at work. Ergon SA. 2002;14(2):11–29.

Harrison

, Harrison

, Croft

, Harrison

, Troyanovich

Sitting biomechanics part I: Review of the literature. J Manipulative Physiol Ther. 1999;22(9):594–609.

10.

Antle

, Cormier

, Findlay

, Miller

, Côté

Lowerlimb blood flow and mean arterial pressure during standing andseated work: Implications for workplace posture recommendations. Prev Med Reports [Internet]. 2018;10(March):117–22. Available from: https://doi.org/10.1016/j.pmedr.2018.02.016.

11.

Thorp

, Kingwell

, Owen

, Dunstan

Breaking up workplace sitting time with intermittent standing bouts improves fatigue and musculoskeletal discomfort in overweight/obese office workers. Occup Environ Med [Internet]. 2014;71(11):765 LP–771. Available from: https://oem.bmj.com/content/71/11/765.abstract

12.

Healy

, Winkler

EAH

, Owen

, Anuradha

, Dunstan

Replacing sitting time with standing or stepping: Associations with cardio-metabolic risk biomarkers. Eur Heart J. 2015;36(39):2643–9.

13.

Callaghan

, McGill

Low back joint loading and kinematics during standing and unsupported sitting. Ergonomics. 2001;44(3):280–94.

14.

Tissot

, Messing

, Stock

Studying the relationship between low back pain and working postures among those who stand and those who sit most of the working day. Ergonomics. 2009;52(11):1402–18.

15.

Boussenna

, Corlett

, Pheasant

The relation between discomfort and postural loading at the joints. Ergonomics [Internet]. 1982;25(4):315–22. Available from: https://doi.org/10.1080/00140138208924959.

16.

Waters

, Dick

Evidence of Health Risks Associated with Prolonged Standing at Work and Intervention Effectiveness. Rehabil Nurs [Internet]. 2015;40(3):148–65. Available from: https://onlinelibrary-wiley-com-443.web.bisu.edu.cn/doi/abs/10.1002/rnj.166.

17.

Halim

, Omar

, Saman

, Othman

A review on health effects associated with prolonged standing in the industrial workplaces. IJRRAS. 2011;8(1):14–21.

18.

Capodaglio

Occupational risk and prolonged standing work in apparel sales assistants. Int J Ind Ergon [Internet]. 2017;60:53–9. Available from: https://dx-doi-org.web.bisu.edu.cn/10.1016/j.ergon.2016.11.010.

19.

Balasubramanian

, Adalarasu

, Regulapati

Comparing dynamic and stationary standing postures in an assembly task. Int J Ind Ergon [Internet]. 2009;39(5):649–54. Available from: https://dx-doi-org.web.bisu.edu.cn/10.1016/j.ergon.2008.10.017

20.

Gallagher

, Campbell

, Callaghan

The influence of a seatedbreak on prolonged standing induced low back pain development[Internet]. Vol. 57, Ergonomics. Taylor & Francis; 2014. p. 555–62. Available from: https://dx-doi-org.web.bisu.edu.cn/10.1080/00140139.2014.893027.

21.

McCulloch

Health risks associated with prolonged standing. Work. 2002;19:201–5.

22.

Bahk

, Kim

, Jung-Choi

, Jung

, Lee

Relationship between prolonged standing and symptoms of varicose veins and nocturnal leg cramps among women and men. Ergonomics. 2012;55(2):133–9.

23.

Tüchsen

, Hannerz

, Burr

, Krause

Prolonged standing at work and hospitalisation due to varicose veins: A 12 year prospective study of the Danish population. Occup Environ Med. 2005;62(12):847–50.

24.

Dunstan

, Howard

, Healy

, Owen

Too much sitting –A health hazard. Diabetes Res Clin Pract [Internet]. 2012;97(3):368–76. Available from: https://dx-doi-org.web.bisu.edu.cn/10.1016/j.diabres.2012.05.020.

25.

Hamilton , Hamilton

, Zderic

, Theodore

Role of Low Energy Expenditure and Sitting in Obesity, Metabolic. Diabetes. 2007;56(11):2655–67.

26.

Woo

EHC

, White

, Lai

CWK

Ergonomics standards and guidelines for computer workstation design and the impact on users’ health – a review. Ergonomics [Internet]. 2016;59(3):464–75. Available from: https://dx-doi-org.web.bisu.edu.cn/10.1080/00140139.2015.1076528.

27.

Hyeong

J-H

, Roh

J-R

, Park

S-B

, Kim

, Chung

K-R

A trend analysis of dynamic chair and applied technology. J Ergon Soc Korea. 2014;33(4):267–79.

28.

Sheeran

, Hemming

, van Deursen

, Sparkes

Can different seating aids influence a sitting posture in healthy individuals and does gender matter? Cogent Eng. 20185(1).

29.

Kuster

, Bauer

, Baumgartner

Is active sitting on a dynamic office chair controlled by the trunk muscles?

PLoS One [Internet]. 2020;15(11):e024854. Available from: https://dx-doi-org.web.bisu.edu.cn/10.1371/journal.pone.0242854.

30.

Zhao

, Vogel

, Michaud

, Doehler

Service Design Research about Redesign Sedentary Office Guided by New Ergonomics Theory BT – Cross-Cultural Design. Methods, Practice, and Case Studies. In: Rau PLP, editor. Berlin, Heidelberg: Springer Berlin Heidelberg; 2013. p. 175–83.

31.

Mandal

ÅC

Work-chair with Tilting Seat. Ergonomics [Internet]. 1976;19(2):157–64. Available from: https://doi.org/10.1080/00140137608931528.

32.

Bendix

, Biering-Sørensen

Posture of the trunk when sittingon forward inclining seats. Scand J Rehabil Med. 1983;15(4):197–203.

33.

De Carvalho

, Grondin

, Callaghan

The impact of office chair features on lumbar lordosis, intervertebral joint and sacral tilt angles: a radiographic assessment. Ergonomics [Internet]. 2017;60(10):1393–404. Available from: https://dx-doi-org.web.bisu.edu.cn/10.1080/00140139.2016.1265670.

34.

Goonetilleke

, Rao

Forward sloping chair effects on spinal shape in the Hong Kong Chinese and Indian populations. Int J Ind Ergon. 1999;23(1-2):9–21.

35.

Noguchi

, Glinka

, Mayberry

, Noguchi

, Callaghan

Are hybrid sit–stand postures a good compromise between sitting and standing?

Ergonomics [Internet]. 2019;62(6)811–22. Available from: https://.doi.org/10.1080/00140139.2019.1577496.

36.

, Marras

Evaluating the low back biomechanics of threedifferent office workstations: Seated, standing, and perching. Appl Ergon [Internet]. 2016;56:170–8. Available from: https://dx-doi-org.web.bisu.edu.cn/10.1016/j.apergo.2016.04.001.

37.

Leitkam

, Reid Bush

, Li

A methodology for quantifying seatedlumbar curvatures. J Biomech Eng [Internet]. 2011;133(11). Availablefrom: https://doi.org/10.1115/1.4005400.

38.

Sibella

, Galli

, Romei

, Montesano

, Crivellini

Biomechanical analysis of sit-to-stand movement in normal and obese subjects. Clin Biomech. 2003;18(8):745–50.

39.

Winter

Biomechanics and motor control of human movement. John Wiley & Sons;.2009.

40.

Dawes

Do data characteristics change according to the number of scale points used? An experiment using 5-point, 7-point and 10-point scales. Int J Mark Res. 2008;50(1):61–77.

41.

Wilke

, Neef

, Caimi

, Hoogland

, Claes

New In VivoMeasurements of Pressures in the Intervertebral Disc in Daily Life. Spine (Phila Pa 1976) [Internet]. 1999;24(8). Available from: https://journals.lww.com/spinejournal/Fulltext//0/New_In_Vivo_Measurements_of_Pressures_in_the.5.aspx

42.

Lin

, Parthasarathy

, Taylor

, Pucci

, Hendrix

, Makhsous

Effect of Different Sitting Postures on Lung Capacity, ExpiratoryFlow, and Lumbar Lordosis. Arch Phys Med Rehabil [Internet]. 2006;87(4):504–9. Available from: https://www-sciencedirect-com.web.bisu.edu.cn/science/article/pii/S0003999305014723

43.

Williams

, Hawley

, McKenzie

, van Wijmen

A comparison of the effects of two sitting postures on back and referred pain. Spine (Phila Pa 1976) [Internet]. 1991;16(10):1185–1191. Available from: https://doi.org/10.1097/00007632-199110000-00010.

44.

Bahrami

, Riener

, Jabedar-Maralani

, Schmidt

Biomechanical analysis of sit-to-stand transfer in healthy and paraplegic subjects. Clin Biomech. 2000;15(2):123–33.

45.

Burdett

, Habasevich

, Pisciotta

, Simon

. Biomechanical comparison of rising from two types of chairs. Phys Ther. 1985;65(8):1177–83.

46.

Rodosky

, Andriacchi

, Andersson

GBJ

The influence of chair height on lower limb mechanics during rising. J Orthop Res. 1989;7(2):266–71.

47.

Arborelius

ULFP

, Wretenberg

PER

, Lindberg

The effects of armrests and high seat heights on lower-limb joint load and muscular activity during sitting and rising. Ergonomics [Internet]. 1992;35(11):1377–91. Available from: https://doi.org/10.1080/00140139208967399

48.

Manorama

, Baek

, Vorro

, Sikorskii

, Bush

Blood perfusion and transcutaneous oxygen level characterizations in human skin with changes in normal and shear loads – Implications for pressure ulcer formation. Clin Biomech [Internet]. 2010;25(8):823–8. Available from: https://dx-doi-org.web.bisu.edu.cn/10.1016/j.clinbiomech.2010.06.003.