Reference
Buffey AJ, Herring MP, Langley CK, Donnelly AE, Carson BP. The acute effects of interrupting prolonged sitting time in adults with standing and light-intensity walking on biomarkers of cardiometabolic health in adults: a systematic review and meta-analysis. Sports Med. 2022;52(8):1765-1787.
Objectives
To compare breaking up periods of prolonged sitting with either short bouts of standing or light-intensity walking and determine the effects each has on cardiometabolic health markers
Key Takeaway
Light-intensity walking was found to be a superior intervention compared to standing and prolonged sitting. These effects were more pronounced in overweight individuals compared to individuals with frank obesity.
Design
Systematic review of randomized crossover studies, up to August 2021, of standing or walking interruptions to daily sitting
Participants
All participants in the meta-analysis were aged more than 18 years and were predominantly overweight.
Study Medication and Dosage
The included studies all asked participants to break up periods of prolonged sitting during the day by either standing or walking at varying intervals.
None of the studies prescribed the exact same sitting-intervention protocol for participants. The authors write, “There was significant heterogeneity in the design of the included studies.” The frequency of sitting breaks ranged from every 20 minutes to once an hour. The duration of the breaks ranged from 2 minutes to 30 minutes, and the resulting total time of nonsitting ranged from 28 minutes to nearly 3 hours. The light-intensity walking breaks varied from walking on motorized treadmills, down hallways, or along a marked track with no defined walking speed or impact on the individual, nor did the studies account for individual variance in fitness. There was no single approach to prescribing food and drinks to study participants. Only 1 study prescribed a standardized evening meal the day before the study intervention.
Outcome Measures
Variables included within the meta-analysis were: postprandial glucose, insulin, and systolic blood pressure (SBP).
Key Findings
This meta-analysis of 7 studies found that intermittent short breaks of standing led to a significant reduction in postprandial glucose compared to prolonged sitting.
Compared to sitting, standing resulted in a small, statistically significant mean improvement in glucose (∆ = −0.31, 95% CI −0.60, −0.03; z = −2.15, P<0.04).
Compared to standing, walking resulted in a small, statistically significant improvement in glucose (∆ = −0.30, 95% CI −0.52, −0.08; z = −2.64, P<0.009). The effect was heterogeneous (Q8 = 65.14, P<0.001; I2 = 89.3, 95% CI 85.8, 91.9). Begg’s rank correlation (Kendall τ = 0.03, P>0.91) was not statistically significant, but Egger’s regression (intercept = −5.62, SE = 1.61, P≤0.01) suggested possible publication bias.
Significantly larger improvements in glucose were derived from studies of mixed samples of males and females (∆ = −0.52) compared to studies of females only (∆ = 0.09; z = 2.08, P<0.04), and from studies of participants who were classified as overweight (∆ = −0.45) compared to studies of participants with obesity (∆ = 0.09, z = 2.06, P<0.04).
Greater benefit was seen in overweight but not obese men.
Transparency
The authors declared no conflicts of interest.
Practice Implications
Prolonged periods of time spent sitting appear to have a negative impact on health.1 Prolonged sitting (PS) is associated with detrimental effects on cardiovascular, metabolic, and mental health. It is also associated with poor executive function, memory, attention, and visuospatial skills. The latter are important cognitive aspects of work performance, so there is interest in how to use these findings to structure the workplace environment to enhance worker output. Breaking up prolonged sitting with standing or light-intensity exercises at the workplace is recognized as a potential means to reduce these harmful effects.2
Prolonged sitting (PS) is now associated with increased risk of a number of chronic conditions, including ovarian cancer,3 stroke,4 type 2 diabetes,5 and possibly cardiovascular disease (CVD).6
Interruption of prolonged sitting by simply standing for a period of time or engaging in light physical activity has been suggested as a possible way to negate the potential harm.
Several studies have reported improvements in blood sugar control with interruptions of prolonged sitting. This current meta-analysis, by Buffey et al, of data from 7 studies found that both standing and light-intensity walking improve postprandial glucose metabolism compared to prolonged sitting. This is not a novel finding; earlier meta-analyses have shown a similar effect.7,8 Buffey et al’s analysis shows that light-intensity walking elicited a significantly greater attenuation in postprandial glucose compared to prolonged sitting and standing breaks, which supports the findings of previous studies. Light-intensity walking was also shown to significantly improve postprandial insulin compared to prolonged sitting and standing breaks, but intermittent standing bouts showed no significant effect on postprandial insulin compared to prolonged sitting within this meta-analysis.
Thus, the evidence suggests that standing breaks have a small beneficial effect compared to prolonged sitting on glucose metabolism, but walking breaks work slightly better. The mean reduction of postprandial glucose across the 7 studies when standing breaks were compared to prolonged sitting was −9.51% ± 13.95, while light-intensity walking reduced postprandial glucose by −17.01% ± 15.42 (ranging from −55.64% to −3.28%) when compared to prolonged sitting. It shouldn’t be a big surprise that walking lowers blood sugar more than simply standing. This meta-analysis, however, is the first to report a statistically significant mean improvement in postprandial glucose response when interrupting prolonged sitting with standing.
The early research suggesting intermittent standing to break up extended sitting periods created demand for standup desks. This newer idea that walking might be even more effective at alleviating the negative impact of sitting is also of great interest, especially in light of the Covid-19 pandemic, which has relegated many people to working from home, a situation that in many instances has increased their tendency to sit for extended periods uninterrupted.9
The studies included in Buffey et al’s analysis were mostly small. The largest was Yates et al, which enrolled 60 participants,10 followed by the studies from Pulsford et al (n=25)11 and Henson et al (n=22).12 The remaining 4 studies collectively contributed data from 46 individuals (Brocklebank [n=17],13 Bailey et al [n=10],14 Crespo et al [n=9],15 Kerr et al [n=10]16). They were also short-term, lasting only 1 day, and were not designed to measure long-term changes in health outcomes. They do not inform us of what changes occur if a sedentary individual changes their behavior patterns over an extended period.
As with any new area of research, it is important that the findings be closely watched for distortion. In particular, “issues such as the non-publication of negative findings (publication bias), the publication of some outcomes and not others (selective reporting), the reporting of same outcomes multiple times, and the clarity of outcomes reported in separate papers arising from the same study (duplicate publication bias), affect the trustworthiness of the original publications making reviews more challenging and therefore review findings can lead to the overestimation of effects.”17
With the invention and widespread acquisition of wearable electronic accelerometer devices that accurately track and record body activity, data that inform people of healthier activity patterns have become of great interest. People are eager and excited about setting and reaching targeted activity goals. The published studies on prolonged sitting have been limited in size, so combining their findings in meta-analyses provides a possible tool to increase the statistical power to find definitive answers.
Prolonged sitting is now associated with increased risk of a number of chronic conditions, including ovarian cancer, stroke, type 2 diabetes, and possibly cardiovascular disease.
While it is satisfying that the researchers were able to find significant positive associations from their computations, the quality of the initial studies and their wide variations in protocol should dampen our exuberance and certitude of their conclusions.
Clinically these findings appear to be most applicable to those patients who are overweight according to their body mass index (BMI) and sedentary and who have dysglycemia, in which their blood sugar spikes high after eating. We should encourage these people to stand up rather than sit for prolonged periods. It helps more if they walk around, but simply standing is better than just sitting. If we want to extrapolate from these findings, perhaps the most appropriate patient to push these interventions toward would be the overweight type 2 diabetic.18
We know the best way to instill this message to patients is by example. Rather than taking your patient straight from waiting room into your office, make a habit of taking them along on a short walk with you. Even if it is a walk within your building, it will give you an opportunity to mention this concept of breaking up periods of sitting and teach by example: “Come along with me for a short walk. I have to sit all day long, and I feel better if I break up my day with short walks. It gets my blood moving again. And the latest research is suggesting that it helps control blood sugar, by the way.” (Of course, if your facilities allow you to walk them outside, through a forest, well, do so, but that is another lesson and a slightly different topic, but you might hopefully combine both.)
The other advantage of imparting this lesson outside of your office proper is that you can be a bit vague. I find that sitting behind my desk, with my library and filing cabinets to the side, patients expect definitive answers and a specific prescription and dose from me. But for standing and walking interventions, we don’t have a defined prescription yet, at least not from Buffey et al’s current analysis. We can’t answer patients’ simple questions as to how often or how long they should stand or walk. Rather than giving vague answers and admitting that we don’t know yet, you can just show them how you yourself incorporate this concept into your daily routine with them at your side.
While we want to assume that standing and walking will also improve cardiovascular disease, this meta-analysis provides no direct support. The researchers write, “Standing and light-intensity walking both showed no significant difference in SBP [systolic blood pressure] when compared to prolonged sitting and there was no difference in SBP between interventions.”
Nonetheless, these ideas have great appeal to the public and to health practitioners as both standing and walking seem easy and safe to incorporate into one’s regular routine. We should keep in mind, though, that the research is still early and not as solidly substantiated as some might imply. As with all interventions, we first should consider the risks versus benefits. At this point there appears to be little harm to standing up or taking a walk from time to time, while potentially we can imagine significant possible benefit based on these early studies, especially as most everyone will feel a bit better afterwards.
