Referring to previous population-based studies validating the IPAQ in diverse populations (Craig et al., 2003; Hagströmer et al., 2006), the questionnaire assesses time (frequency and duration) spent on vigorous, moderate-intensity, walking activities, and sitting time in hours over the past seven days. The IPAQ-short form has demonstrated acceptable reliability (Spearman’s ρ = 0.8) and criterion validity across multiple countries and populations.

All yoga interventions were conducted by certified instructors holding RYT-500 (Registered Yoga Teacher) certification with minimum 5 years of teaching experience. Intervention protocols were standardized using detailed written scripts and video demonstrations. Each session was monitored for adherence to prescribed postures, timing, and breathing patterns. Inter-rater reliability for intervention delivery was established through dual observation of 20% of sessions (κ = 0.89).

Over three weeks, participants were requested to do one of the following ‘activities’ over successive weeks: Week 1 – prolonged sitting; Week 2 – pranayama intervention during prolonged sitting; and Week 3 – yoga asana intervention during prolonged sitting. Vascular function was assessed for each of the three conditions including the diameter and blood velocity of the SFA and CCA were measured at the start of the study (0), two, and four hours during sitting using a Doppler ultrasound (Philips, Epiq Elite). Ultrasound machine quality assurance test results fell within manufacturer specifications. Ultrasound was performed by a competent radiologist (see Figure 1).

Prolonged sitting: Participants remained seated in a standardized office chair (back support 90°, feet flat on floor) for four continuous hours. Brief bathroom breaks (≤2 minutes) were permitted when necessary, but participants were instructed to minimize movement and maintain the seated position throughout the session ( Figure 2).

Pranayama intervention: Every hour during the 4-hour sitting period, participants performed a standardized 10-minute pranayama sequence led by a certified yoga instructor: •

Deep breathing (Dirga Pranayama): 3 minutes - slow, controlled breathing with 4-second inhalation, 2-second retention, 6-second exhalation.

Yoga Asana Intervention: Every hour during the 4-hour sitting period, participants performed a standardized 10-minute sequence:

•

Tadasana (Mountain Pose): 1 minute - standing with arms overhead, deep breathing.

All interventions were supervised by qualified instructors and standardized across participants to ensure consistency.

Statistical significance was set at α = 0.05 for all analyses. Given the exploratory nature of this study with multiple outcome measures, we report both statistical significance (p < 0.05) and effect sizes to provide comprehensive interpretation. For multiple comparisons within each vascular measure (diameter, velocity, shear, stress), Bonferroni correction was applied, adjusting the significance threshold to α = 0.0125 (0.05/4) for family-wise error control. Post-hoc analyses for significant main effects used Tukey’s HSD test to control Type I error inflation. All analyses were performed using JASP statistical software version 0.16.2, with both parametric (repeated measures ANOVA) and non-parametric (Friedman’s test) approaches based on normality testing via Shapiro-Wilk test.

Figure 3 illustrates how the results of the CCA reveal that the artery’s width decreases with each set of interventions. In comparison with time, the first and second hours exhibited statistical significance with a p value<0.001, whereas the third and fourth hours do not exhibit statistical significance (p value = 0.020). The yoga asana intervention demonstrated statistical significance (p = 0.014) when compared to the pranayama group and prolonged sitting. Table 2 represents the data of CCA diameter at different time points.

In addition, the yoga asana intervention demonstrated statistical significance when compared to the pranayama intervention and prolonged sitting (p value = 0.017).

In the CCA, a reduction in velocity was observed after the pranayama and yoga asana intervention. However, when it comes to prolonged sitting, there was a decrease in velocity at the start of the study and at two hours, followed by an increase in velocity during the final hour as shown in Figure 4. With CCA velocity, neither time nor blood velocity were statistically significant. Table 3 represents the data of CCA velocity at different time points.

The diameter of the SFA decreased each hour during prolonged sitting and pranayama intervention. However, during the yoga asana intervention, there was a reduction in diameter at the beginning of the study and at 2 hours, but an increase in diameter was observed in the 4 ^th hour, shown in Figure 5. Neither time nor group showed any significance. Hence the group has not demonstrated any substantial response to any intervention. Tables 4 & 5 represents the data of SFA diameter and velocity at different time points respectively.

In the CCA, the shear rate increased each hour during prolonged sitting, whereas it decreased in both the pranayama and yoga asana interventions ( Figure 6). All interventions showed a reduction in stress in CCA ( Figure 7). However, in terms of shear and stress, neither the time nor the group showed any significant difference. Table 6 represents the data of CCA shear and stress at different time points.

Our study investigated acute vascular responses to single-session interventions, which differs from most existing literature examining chronic exercise effects. While studies like Ross and Thomas (2010) ¹⁹ examined long-term yoga effects over 3-6 months, ¹⁹ our findings demonstrate that even acute yoga asana interventions can produce measurable vascular improvements. This aligns with research by Thosar et al. (2015), ²³ who similarly examined acute vascular responses during prolonged sitting interventions. ²³ The immediate vascular benefits observed in our study suggest that yoga asanas may serve as effective ‘micro-breaks’ during prolonged occupational sitting, with potential for cumulative benefits when practiced regularly.

In a study by Pearson and Smart (2017), participants underwent aerobic exercise with an intervention duration ranging from four weeks to six months, with the frequency of sessions varying from daily to two days per week, and the time of exercise sessions ranged from 10 to 60 minutes. The study concluded that aerobic exercise training significantly improved endothelial function. ²¹ As compared to our study, the yoga asana intervention showed improvement in both carotid and superficial femoral artery diameter.

A study conducted by Cortez-Cooper examined the effect of different types of intervention on cardiovascular health. The study included three groups: a strength training group, a combination group that received both strength training and aerobic exercise, and a stretching group. The results showed that the strength training and combination groups experienced significant changes in cardiovascular health markers, including carotid artery pulse pressure. The study also found that carotid artery compliance decreased slightly in the strength training and combination groups and increased in the stretching group. However, the study found no carotid-femoral pulse wave velocity changes in the strength training and combination groups. Overall, the combination of strength training and aerobic exercise may be more effective than stretching alone in improving cardiovascular health. ²² When compared to our study, the yoga asana intervention gave significant changes.

A study by Thosar et al. (2015) involved 12 men participating in two randomized three-hour sitting trials. The first trial was a sitting trial where the subject was seated in one position without interruption The second trial was a sit-walk trial where the subjects walked on treadmills for five minutes at two mph for 30 minutes, 1.5-hour and 2.5-hour intervals during the sitting period. The study assessed the flow mediated dilation (FMD) of the SFA at baseline, one hour, two hours, and three hours in each trial. The results showed that there was no significant decline in the sitting trial in the FMD at each hour from baseline. The mean shear rate also showed a substantial decrease in the baseline across time. The sit-walk trial, however, showed a significant difference in the FMD and mean shear rate compared to the sit trial, indicating that walking during prolonged sitting may benefit arterial health. ²³ As compared to our study, both CA and SFA are measured. In our study all interventions – aside from the prolonged sitting – showed a minor decrease in CA velocity over time. When the seated intervention reached the last four hours, it will rise. Compared to time, the first and second hours exhibit statistical significance with a p value of <0.001, whereas the third and fourth hours exhibit significance but do not exhibit statistical significance (p value = 0.020). There is no significant difference in SFA. But in our study, yoga asana showed effectiveness in both CA and SFA.

When people sit for lengthy periods, their CA shear increases, whereas pranayama and yoga asana interventions showed decreases in CA shear for each hour. In CA shear, both time and group will not show any significance.

Long periods of sitting have been shown to reduce stress in SFA, and yoga asana and pranayama interventions have also been shown to reduce stress over time. Both time and group do not exhibit any significant differences when compared.

The study by Carter et al. (2018) recruited 15 office workers (10 male). The participants sat for hours with two minutes of light intensity treadmill walking every 30 minutes and four hours sitting with an eight-minute light intensity treadmill walking break every 120 minutes. Middle cerebral artery measures were taken, and it was found that there was no significant difference in cardiorespiratory and hemodynamic measures, but a significant main effect was observed in cerebral blood flow. Post hoc analysis revealed a greater change in middle cerebral artery (MCA) during sitting compared to walking, with a considerable reduction in MCA observed in both the sitting and walking conditions. ²⁴ Compared to our study, the diameter significantly decreases in the sitting intervention, but velocity will increase similarly in SFA diameter and velocity decreases during the sitting intervention. Compared to time, the first and second hours exhibit statistical significance with a p value of <0.001, whereas the third and fourth hours demonstrated significance but did not exhibit statistical significance (p value = 0.020). The yoga asana intervention showed significance compared to pranayama and prolonged sitting, though it didn’t reach statistical significance (p-value = 0.014). In contrast, the yoga asana intervention showed significance but not statistical significance when compared to the group in pranayama intervention and prolonged sitting (p value = 0.017). While in CA velocity, neither time nor velocity were significant.

The yoga asana intervention demonstrated improvement in SFA diameter; however, there was no difference between time and group when compared side by side. Each hour of the intervention resulted in a drop in velocity. The time points at the study’s start (0th hour) and at the 2nd hour demonstrate significance (p-value = 0.026). However, while both the 0th and 2nd hours show significance with a p-value of 0.004, they still do not reach statistical significance. The group did not demonstrate any substantial response to any intervention. Hence, it shows that yoga asana will improve vascular function.

The observed improvements in CCA diameter following yoga asana intervention likely result from multiple physiological mechanisms. First, the combination of controlled movement and pranayama breathing activates the parasympathetic nervous system, reducing sympathetic vasoconstriction and promoting vasodilation through enhanced nitric oxide (NO) bioavailability. The rhythmic contraction and relaxation of skeletal muscles during asana practice creates a ‘muscle pump’ effect, enhancing venous return and reducing peripheral vascular resistance.

Second, the postural changes inherent in yoga asanas may counteract the gravitational pooling of blood that occurs during prolonged sitting. Studies have shown that even brief postural changes can restore endothelial function by increasing shear stress on arterial walls, stimulating NO production and improving flow-mediated dilation.

The observed acute improvements suggest that yoga-based micro-breaks could serve as practical occupational health interventions. However, several questions remain: (1) What is the optimal frequency and duration of interventions for sustained benefits? (2) How do individual factors (age, fitness level, cardiovascular risk) modify the response? (3) What are the long-term cardiovascular outcomes of regular yoga micro-break implementation?

Future research should investigate dose-response relationships, compare different types of movement interventions, and examine long-term cardiovascular outcomes in diverse occupational populations. Additionally, mechanistic studies using more sophisticated vascular assessment techniques (e.g., flow-mediated dilation, pulse wave velocity) could provide deeper insights into the physiological pathways involved.