Feasibility and behavioral effects of prolonged static and dynamic standing as compared to sitting in older adults with type 2 diabetes mellitus

Diabetes mellitus is highly prevalent in older adults [1] and is expected to reach endemic proportions as it is predicted to increase by 54% from 2015 to 2030 in the United States of America [2]. Over 30% of older adults probably have evidence of pre-diabetic insulin resistance [3]. Type 2 diabetes mellitus (T2DM) in older adults is especially problematic as it impacts both physical and cognitive function [4‐6]. Hence, effective control of T2DM and its sequelae is of utmost importance in this geriatric population.

Sedentary behavior has been strongly associated with the development of diabetes mellitus [7]. Unfortunately, the modern home- and workplace environment promote sedentary behavior. This is further exacerbated by significant barriers to exercise and physical activity in T2DM patients, such as poor tolerance to physical effort, development of pain with physical activity, and lack of motivation [8]. Older adult T2DM patients are more likely to be physically inactive and adherence to an exercise program to meet recommended minimum guidelines appears to be an elusive goal in these patients [9].

Simple intermittent non-exercise interruption of prolonged inactivity during daily life could potentially represent a more feasible target in older adult T2DM patients [10]. For example, even a modest increase in physical activity and reduction in sedentary time may significantly improve health, especially in the most inactive older adults [11]. Upright standing represents the most rudimentary form of physical activity and may have specific metabolic benefits in T2DM. Several studies, mainly conducted in office workers, have shown beneficial effects of desktop standing on metabolic risk factors such as insulin resistance and glycemic excursion [12‐14]. Non-exercise physical activity interventions that can be performed at home while integrating this with routine activities of daily living may provide an attractive means to reduce sedentariness and improve diabetic control in older adult patients with diabetes.

The aim of this study was to examine the feasibility of 4h standing sessions while performing routine desktop activities as a non-exercise physical activity intervention in older adults with T2DM to increase non-exercise activity thermogenesis (NEAT). The primary hypothesis was that 4h standing behind a height-adjustable desk is feasible in an older adult population with T2DM. We also hypothesized that standing while performing weight-shifting movements will lead to additional increase in oxygen uptake as compared to normal more ‘static’ stance. Finally, we explored secondary outcome parameters of net duration of standing time, total movement, rate of musculoskeletal discomfort development and leg swelling, and performance on a cognitive task during the different sessions.

Our findings show that ad libitum four-hour standing is feasible and may have clinical benefits in an older adult type 2 diabetic population. Compared to sitting, oxygen consumption increased during static standing with an additional trend for higher energy expenditure during dynamic standing. These results suggest that standing, as a rudimentary form of non-exercise physical activity, should be further explored as a simple yet effective means to counteract sedentary behavior in this patient population. Moreover, making small weight-shifting movements during standing may be even more beneficial than regular stance. For example, our results also showed that shorter breaks were needed during dynamic compared to static standing. The rate of total musculoskeletal discomfort development was also lower in the dynamic compared to the static standing group.

Increased sedentary behavior in adults is not only associated with T2DM but also with other deleterious health outcomes, such as cancer, cardiovascular disease incidence and increased overall mortality [21]. Changing sedentary behavior to a more physically active lifestyle in older adults remains challenging [22]. For example, despite well-known physical exercise-related health benefits, in general, the older adult population remains sedentary for an average of 9.4-h a day (up to 80% of their waking day) [23]. Diabetic patients engage even 10–20% less frequently in physical activities [24‐26]. These observations indicate a clinically unmet need to promote physical activity in older adult patient populations who need it the most. Given the well-known barriers to exercise participation in older adult patient populations with chronic disorders, a natural first step would be to reduce sedentariness with intermittent non-exercise physical activity. To our knowledge, this is the first study to investigate the feasibility and clinical effects of prolonged desktop standing in rather inactive and overweight patients with T2DM, and therefore may hold clinical and public health relevance.

Energy expenditure of physical activity other than volitional exercise is referred to as non-exercise activity thermogenesis (NEAT) [27]. Previous research found that NEAT is lower in obese people [28]. Standing may be a simple, yet effective, means to increase NEAT and counteract the negative effects of physical inactivity due to prolonged inactivity [29]. Our results are in line with previous studies showing elevated VO₂ consumption rates during (both) standing condition(s) as compared to sitting [30]. Interestingly, compared to the study by Cox et al. we had similar VO₂ values for the seated condition (3.3 ml·kg^− 1·min^− 1), however, our T2DM participants showed higher mean values of VO₂ consumption (4.2 ml·kg^− 1·min^− 1) during regular stance compared to lean the lean and asymptomatic participants in their study (3.6 ml·kg^− 1·min^− 1) [30]. This observation suggests that standing may potentially have even more benefits in an overweight population of older T2DM patients. We also found a trend toward additional higher energy expenditure in our T2DM patients during dynamic standing compared to regular or static standing. As such, use of a dynamic standing desk may be of particular relevance for older overweight adults with T2DM as it increases NEAT without significant side-effects, such as significantly lower discomfort rates [31].

There were no negative effects of standing on cognitive functions, such as executive functions of set shifting and response inhibition as measured by the Trail Making and Stroop tasks, respectively. Most of prior studies on sit-stand, bike and treadmill desks were aimed at reducing sedentary behavior in the work place, especially among office workers. In office workers, it is crucial that such physical activity interventions do not negatively impact a person’s productivity, their efficiency of daily tasks, or general cognitive performance. However, results of these studies showed relatively mixed results with respect to the outcome of these physical activity intervention on cognitive-motor performance or work productivity. For example, Koren et al. [32] introduced a cycloergometer to office workers with the aim of achieving minimum standards for daily physical activity during working hours. These authors found evidence of increased typing time but without other negative cognitive outcomes. Treadmill desk studies revealed a significant reduction in sedentary behavior during working hours [33] but with relatively mixed results in cognitive, fine motor skills and work performance (e.g. [34‐37]). Even though treadmill desks may provide particular benefit to overweight and obese individuals, two recent systematic reviews reported possible detrimental effects on work productivity as well as motor abilities [38, 39]. In contrast, our findings do not show evidence of any detrimental cognitive executive function effects during static or dynamic desktop standing session in our older adult T2DM patient population. Further research is needed to determine whether dynamic types of desktop standing may provide more safe alternatives to increase physical activity in office workers without adverse effects on job productivity.

A limitation of our study was that we did not specifically assess metabolic glycemic measures in our patients. There is existing evidence that simple standing may have beneficial metabolic effects in diabetic populations. For instance, Henson et al. [29] reported reduced postprandial glucose, insulin, and nonesterified fatty acids after 5-min bouts of standing or light walking in postmenopausal women at high risk of T2DM. In a similar attempt in a population of 24 obese older adults with T2DM, Dempsey et al. [40] found attenuated postprandial glucose, insulin, C-peptide, and triglyceride levels after 3-min bouts of light-intensity walking and simple resistance activities. Both studies concluded that these simple behavioral approaches might represent a novel public health intervention aiming at reducing the risk of T2DM and/or improving metabolic profile of such symptomatic individuals [29, 40]. Future clinical trials should be conducted to examine whether our desktop standing interventions may have similar benefits in a population with T2DM, while taking into consideration that dynamic standing is, according to relative VO₂ calculations, approximately two times less energetically demanding as light-intensity walking [40].

An important finding of our study is that prolonged (four-hour) static and dynamic standing is feasible and safe in a rather sedentary and overweight older adult patient population with T2DM. However, three main methodological limitations should be taken into consideration when interpreting the results of the present study. First, the laboratory setting might have enticed our participants to accomplish all requested conditions; therefore, testing in a home environment is necessary to reassess our paradigm and its long-term utilization. Second, patients were randomized to the standing sessions after completion of a sitting session. Therefore, learning effects may affect cognitive outcome measures and could potentially explain the trends toward improved cognitive performance during the standing sessions in our study. However, participants received detailed instructions as well as a test trial in order to mitigate the learning effect prior to starting the baseline (sitting) condition. Other factors such as exercise-level associated arousal may also influence participants’ cognitive performance [41‐43]. Third, the number of subjects was small in our feasibility testing resulting in lack of statistical power. Future phase 2 clinical trials in a larger population are needed to address these important issues. These studies should also include specialized laboratory test (blood glucose, insulin resistance/sensitivity etc.) and further assess metabolic dose-response effects of standing duration taking into consideration also individual baseline physical activity levels. While evaluating the effects of non-exercise regimes (e.g. dynamic standing) on cognitive functioning and work productivity, transition states and thus multiple time-point testing of cognitive abilities should be considered [44].

In conclusion, our study indicates that patients with T2DM are able to perform longer duration standing sessions without any serious side effects. Four hour standing sessions are therefore feasible in older adult rather sedentary and overweight patients with T2DM and, more importantly, can possibly have metabolic benefits on energy expenditure. Standing interventions in patients with T2DM, especially when combined with weight-shifting movements, can represent a novel, barrier-free non-exercise physical activity program, that targets sedentariness and can be easily and safely integrated into daily routines. Further research is needed to assess long-term effects of such standing interventions in the home environment in older adult patients with T2DM.