Sitting, Standing, and Walking: The Effect on Cardiometabolic Markers
By Ellen Feldman, MD
Altru Health System, Grand Forks, ND
Summary Points
- This meta-analysis incorporated seven one-day laboratory studies regarding interrupting prolonged sitting with standing or light-intensity walking. All seven studies measured postprandial glucose levels, four measured postprandial insulin levels, and three measured systolic blood pressure.
- Standing as a break from sitting compared to prolonged sitting was associated with a small effect on reduced postprandial glucose (P < 0.04) and postprandial insulin (P < 0.06) but did not show a significant association with change in systolic blood pressure.
- Light-intensity walking as a break from sitting compared to prolonged sitting was associated with a moderate effect size on reduced postprandial glucose (P < 0.001) and postprandial insulin (P < 0.001) but did not show a significant association with change in systolic blood pressure.
- Light-intensity walking vs. standing (as a break from prolonged sitting) found that light-intensity walking was associated with a small effect size but significant lowering of postprandial glucose (P < 0.0009) and a moderate effect size on postprandial insulin (P < 0.001).
SYNOPSIS: This meta-analysis explores the effects of interrupting sitting with either light-intensity walking or standing and finds that light-intensity walking is associated with the most significant impact on several markers of cardiometabolic health.
SOURCE: Buffey AJ, Herring MP, Langley CK, et al. 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;52:1765-1787.
Sedentary lifestyles are dangerous for health. Defined as any waking behavior expending < 1.5 metabolic equivalent tasks while seated or reclined, prolonged sedentary behavior has been linked to many markers of poor health, including increased waist circumference and increased levels of C-reactive protein.1
Recent studies have found that interruptions of sedentary behavior (also known as sedentary breaks) have an association with a number of health benefits, including improved systolic blood pressure, increased high-density lipoprotein cholesterol, decreased postprandial insulin and glucose, and decreased waist circumference. The relationship between intensity of exercise during a sedentary break and health benefits is not yet defined.2,3
To begin clarifying the association between the type of sedentary break and biomarkers of cardiometabolic health, Buffey et al conducted a comprehensive review and meta-analysis of one-day experimental studies (conducted in lab settings) comparing prolonged sitting in adults with sitting interrupted by standing and sitting interrupted by light-intensity walking. To be eligible for this study, trials needed to include adult males and/or females as participants, measure at least one biomarker of cardiometabolic health, and include prolonged sitting (at least five hours), standing, and light-intensity walking among the study arms. Seven such studies, five from the United Kingdom and two from the United States, were identified for the final review and meta-analysis.
Despite meeting all inclusion criteria, the seven studies were significantly heterogeneous in methodology, including frequency and duration of breaks, the definition of light-intensity walking, meals provided to participants, and measurement techniques for the biomarkers (continuous monitoring vs. periodic blood collection) as well as the biomarkers measured.
Although some of the studies measured factors such as diastolic blood pressure, cholesterol, and triglyceride levels, the biomarkers included in this systematic review and meta-analysis were postprandial glucose, insulin, and systolic blood pressure. These were chosen because each of them was measured in at least three of the included studies, allowing sufficient data for a valid meta-analysis. Specifically, all seven studies measured postprandial glucose, four of the studies measured postprandial insulin, and four of the studies measured systolic blood pressure.
RESULTS
Differences are reported in terms of Cohen’s d, which often is used in social sciences to determine the magnitude or practical significance of an intervention, especially when there are multiple variables or outcomes.4
Cohen’s d is found by calculating the standardized difference between two means (mean of Group A - mean of group B ÷ pooled standard deviation.) In general (and for this study), effect size is defined as small effect: 0.2, medium effect: 0.5, and large effect: 0.8. It is interesting to note that effect size and statistical significance differ. One way to think about this is to consider that effect size reflects the importance or clinical relevance of the result (for example, a medium effect size is a result that should be visible to “the naked eye”) while statistical significance or P value indicates the likelihood of the result occurring by chance.4,5
It also is useful to note that in this study a negative effect size implies an improvement in biomarkers (decrease in value of postprandial glucose, postprandial insulin, and/or systolic blood pressure).
Table 1 summarizes the results.
Table 1. Cardiometabolic Measured Effect Size of Interrupting Sitting |
|||
| Standing vs. Prolonged Sitting | Walking vs. Prolonged Sitting | Walking vs. Standing | |
Postprandial glucose |
Small effect size Cohen’s d = -0.31 (95% CI, -0.60 to -0.03; P < 0.04) |
Moderate effect size Cohen’s d = -0.72 (95% CI, -1.03 to -0.41; P < 0.001) |
Small effect size Cohen’s d = -0.30 (95% CI, -0.52 to -0.08; P < 0.009) |
Postprandial insulin |
Small effect size Cohen’s d = -0.30 (95% CI, -0.60 to -0.01; P < 0.06) |
Moderate to large effect size Cohen’s d = -0.83 (95% CI, -1.18 to -0.48; P <0.001) |
Moderate effect size Cohen’s d = -0.54 (95% CI, -0.75 to -0.33; P < 0.001) |
Systolic blood pressure |
No effect size Cohen’s d = 0.02 (95% CI, -0.13 to 0.16; P > 0.82) |
No effect size Cohen’s d = 0.01 (95% CI, -0.28 to 0.30; P > 0.93) |
No effect size Cohen’s d = 0.14 (95% CI, -0.15 to 0.44; P > 0.34) |
CI: confidence interval |
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Upon analysis of subgroups according to body mass index, it was found that, among the walkers, larger improvements in postprandial glucose were found in normal and overweight participants vs. obese participants (P < 0.04).
COMMENTARY
This ambitious systemic review and meta-analysis of studies looking at markers of health associated with two different types of sedentary breaks (standing and light-intensity walking) adds to a growing knowledge base regarding health benefits of interruptions to a sedentary lifestyle.1-3 Specifically, the results of this study point to advantages of light-intensity walking vs. standing as a break from prolonged sitting.
Although the heterogeneity of the covered studies precluded answering some obvious clinical questions (such as how long a break should last and how often a break should be initiated) it is likely that, with the promising results found here, these are areas for future investigation. However, it is useful to note that, on average, most of the studies interrupted sitting for about 28 minutes.
Additionally, Buffy et al noted that future investigations should standardize methodology and include a consistent mechanism to measure cardiometabolic markers, including but not limited to when and how to measure changes in systolic blood pressure and how to best evaluate changes in levels of glucose and insulin. Another feature of this meta-analysis is that all included studies were limited to one-day laboratory trials. This clearly limits the generalizability of the findings.
However, the potential clinical implications of these findings are significant. Light-intensity walking is a practical intervention that can be implemented in various work environments. Additionally, employers may be attracted to this intervention because of its relatively low cost and ease of implementation.
Even with the noted limitations, this review and meta-analysis has value for the integrative provider working with patients to design wellness plans. The study can serve as a reminder that some of the benefits of exercise do not require a gym, strenuous effort, or even measurable weight loss. Instead, incremental changes in markers of cardiometabolic health can be attained by standing up and amplified even more by light walking.
REFERENCES
- Healy GN, Matthews CE, Dunstan DW, et al. Sedentary time and cardio-metabolic biomarkers in US adults: NHANES 2003-06. Eur Heart J 2011;32:590-597.
- Benatti FB, Ried-Larsen M. The effects of breaking up prolonged sitting time: A review of experimental studies. Med Sci Sports Exerc 2015;47:2053-2061.
- Paterson C, Fryer S, Zieff G, et al. The effects of acute exposure to prolonged sitting, with and without interruption, on vascular function among adults: A meta-analysis. Sports Med 2020;50:1929-1942.
- Glen S. Cohen’s d: Definition, examples, formulas. StatistichsHowTo.com. https://www.statisticshowto.com/probability-and-statistics/statistics-definitions/cohens-d/
- Bradburn S. What is and how to calculate Cohen’s d. Top Tip Bio. https://toptipbio.com/cohens-d...
This meta-analysis explores the effects of interrupting sitting with either light-intensity walking or standing and finds that light-intensity walking is associated with the most significant impact on several markers of cardiometabolic health.
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