Improved lower extremity blood flow and enhanced cognitive function with blood flow.

Sitting disease is prevalent in today’s society. Western populations spend an average of 8.5 hours/day sedentary. Now a greater proportion of the workforce spends over 6 hours of their day sitting. The result is a population with heightened risk for cardiovascular diseases. Additionally, an increased percentage of the workforce has or is at risk for type 2 diabetes. One of the complications of diabetes is often the development of peripheral neuropathy. Reduced blood flow to the extremities has detrimental effects on nerve health and can result in this serious condition (Wang and Lin 2007). Over the course of prolonged sitting, lower limb muscle inactivity results in reduced blood flow to the lower limb. With significant attenuated blood flow to the lower limb, transmission of input from the superficial mechanoreceptors in the feet and ankles is disrupted, reducing plantar cutaneous sensitivity (Wang and Lin 2007). This suggests that there is a relationship between plantar skin sensitivity and blood flow. As humans we were also not designed to sit for a large proportion of our day, and as a result extended work days can actually decrease productivity. With extended durations in the seated posture, boredom can lead to decreased attention, increased errors and decreased productivity.

The objective of this study was to address two key questions. The first objective was to investigate the physiological and cognitive effects of prolonged sitting (4 hours), and second, to establish whether the introduction of a healthy active sitting solution could mitigate these effects. CoreChair was tested against a traditional office chair while participants performed daily work. We looked at three physiological measures; blood flow to the lower limb, skin sensitivity to the lower leg and foot, and blood pooling in the lower limb. Additionally we were able to assess two cognitive measures; accumulation of correct responses and errors of commission during a sustained attention task.

During testing, participants were seated at a standard office desk and worked on their personal laptop while an external monitor was used to perform the cognitive task. They were instructed to keep their feet on the ground during the session, but were free to move through the hips, trunk and upper body as needed throughout the testing time. To measure this movement, acceleration of their trunk and the chair were measured. Most of the measures were sampled at baseline (time 0), 20 minutes, 1, 2, 3 and 4 hours into the data collection period. The cognitive test was carried out 30 minutes into sitting time and then approximately at hour four. Participants came in for two sessions, one seated on the traditional office chair and one using the CoreChair. Before using the CoreChair, each participant watched an instructional video that outlined how to adjust and sit in the chair properly, how to move in the chair, and how to use the movement if desired.

We found that as the four hour session progressed participants moved to a greater extent (p<0.0001). This was observed in the both of the chairs. Greater movement was captured as increased trunk acceleration, and to a greater extent as an increase in the acceleration of the chair in the CoreChair. Importantly there were differences in the extent of movement between office chair the two chairs. It was observed that participants moved more in the CoreChair in hour two of the session than they did in the traditional chair (p=0.0374).

The three physiological measures designed to capture changes to the lower limb during sitting were blood flow, calf circumference and monofilament tactile measures. Blood flow did not significantly change over the four hours from baseline on both chairs. We expected blood flow to decrease to the lower limb as many other studies have found a reduction with prolonged sitting (Restaino et al. 2015; Restaino et al. 2016; Thosar et al. 2015; Shvartz et al. 1983). We believe that our technique was not sensitive enough to detect a decrease in lower limb blood flow at the level of the superficial femoral artery during this stationary sitting task. Monofilament tactile sensitivity demonstrated an increased threshold (decreased sensitivity) at hour four relative to baseline on both chairs (p=0.0503). Therefore, while our measure was sensitive enough to detect the effects of prolonged sitting, CoreChair was not able to mitigate the decrease in tactile sensitivity at hour four of sitting. This inability to mitigate the effects may be due to the under use of the ChoreChair in the current study. It was notable the movement was only seen to differ in hour two between the to chairs. Differences were seen between the two chairs for heel sensitivity. It was found that the sensitivity of the heel in the CoreChair was lower than in the traditional chair p=0.0064). It is believed that this is due to the greater need to stabilize the body and keep the feet on the ground in the CoreChair; while participants were seated in the CoreChair they may have exerted greater pressure through the heel.

Calf circumference was the third measure observed in the lower limb, it was used to assess differences in blood pooling in the lower limb during prolonged sitting. Calf circumference significantly increased across the four hours (p<0.0001), indicating there is an increase in the pooling of blood in the lower limb with prolonged sitting. In hour three there was a significant difference in the calf pooling between the two chairs (p<0.0001). In the CoreChair trials there was a significantly smaller calf circumference during this hour than when using the traditional office chair indicating that use of CoreChair is promoting more movement of blood from the lower limb, resulting in less pooling. Although we did not measure muscle activity we believe this is due to the increased movement seen during hour two, and the engagement of trunk and lower limb musculature needed to move the chair.

The final two measures were observed to target the ability of CoreChair to alleviate some of the cognitive decline that may be seen during prolonged sitting. First, we needed to assess whether there was in fact a decline in attention, and cognitive ability from baseline to hour four. The cognitive task assigned required participants to refrain from hitting a keyboard key when a specified number appears on screen. We observed a decrease in the number of correct responses (correctly refraining from hitting the key) from baseline to hour four of sitting (p=0.035). In other words, participants were getting worse over the four hours. This did not significantly differ between the two chairs. There was a trend toward an interaction effect whereby there was less decline in the number of correct responses on the CoreChair (p= 0.086). This means, when using CoreChair participants were able to refrain from hitting the key to a larger extent, demonstrating less cognitive decline during the 4 hour sitting session. Given more subjects, there may have been the potential to show that the significantly greater movement in the CoreChair can alleviate cognitive decline during prolonged sitting.

When looking at the errors of commission (not correctly refraining from hitting a key), there was a significant increase from baseline to hour four (p=0.012). Further statistical measures showed that the significant increase in errors of commission was only observed in the traditional chair (p=0.0046), not the CoreChair (p=0.127). Therefore, higher movement in the CoreChair at just one time point may mitigate cognitive decline in attention during long periods of sitting.

Overall, our findings suggest that with minimal, although significant, increased movement in the CoreChair during hour two of the seating session there was evidence of significant changes to both physiological and cognitive effects. We believe that a decline in lower limb blood pooling and mitigation of a decline in cognition measures during prolonged sitting can be attributed to increased movement in CoreChair at hour two. Importantly, we feel that further instructions need to be addressed to the client and/or end user to promote additional movement on the CoreChair during extended periods of sitting. We feel this will help to increase the preliminary physiological and cognitive benefits observed here