Active Voice: You Might Want to Sit Down for This!
Gregg Afman, Ed.D., and James A. Betts, Ph.D., FACSM
Gregg Afman, Ed.D., is a professor of kinesiology at Westmont College in Santa Barbara, California. He is a member of ACSM. James A. Betts, Ph.D., FACSM, is a professor of metabolic physiology at the University of Bath in the United Kingdom. Long-standing friends and collaborators, the pair shares interests and collective expertise in nutrition, metabolism, human anatomy and exercise physiology.
This commentary presents some of their thoughts on a recent experiment they conducted together between their two laboratories, which are separated by 5,400 miles. Their paper “The Energy Cost of Sitting versus Standing Naturally in Man” appears in the April 2019 issue of Medicine & Science in Sports & Exercise® (MSSE). Professor Betts also will present their study findings in a free communication/slide session at the ACSM Annual Meeting later this month.
The colloquial phrase “take a load off your feet” reflects the universal recognition that sitting requires less effort than standing. This makes perfect sense when considering the active musculature required in each posture. We were aware of recent campaigns and technologies to promote standing on the basis that prolonged sitting is closely linked to obesity and poor health. Yet, we also were surprised to find that the fundamental difference in energy cost between sitting and standing naturally had never been measured.
Certainly, past laboratory experiments had carefully documented the raw biomechanical advantage of sitting when remaining completely motionless. Yet, natural bodily movements like fidgeting are not usually restricted in daily life. Conversely, field-studies had observed far higher physical activity levels when chairs are withheld, and people are encouraged to walk around while completing their usual daily tasks. However, most strategies reflected in interventions intended to reduce sitting time simply result in subjects standing in one place rather than moving around.
We filled this important gap in understanding by very precisely measuring metabolic rate during sitting and standing – but under purposely uncontrolled conditions, i.e., allowing spontaneous fidgeting to maintain a comfortable posture. The 12 percent difference we report is interesting for several reasons, primarily because this value (under 10 kcal per hour) is less than half of earlier estimates, which included walking. The additional energy expended by simply standing more each day, therefore, is unlikely to result in meaningful weight loss. We note an interesting ancillary observation that carbohydrate oxidation was incredibly stable between these two postures (0.002?1.0 grams per hour), so the increment when standing was supported by relatively greater fat metabolism (1.0?0.4 grams per hour).
Beyond the relative difference between postures, another interesting point to take from our study in the April 2019 issue of MSSE concerns the findings we reported on absolute energy cost. Specifically, our data reveal that sitting and standing naturally are equivalent to MET values (i.e., multiples of resting metabolic rate) of 1.1 and 1.2, respectively. This is relevant given that the 2011 Compendium of Physical Activities estimates values of 1.5 for sitting and 1.8 for standing when fidgeting–notably higher than what we measured.
A subtle, but pertinent, feature of our experimental design was the inclusion of a resting metabolic rate assessment and a lying condition alongside the main sit-stand contrast. This enabled us to normalize the energy cost of each posture for basal metabolic requirements, so that individual differences in observed response would be mainly due to fidgeting rather than the amount of bodily tissues to be supported in each position. In this way, we noticed that the amount of fidgeting in each posture was highly individual between different participants. Upon further analysis, we found correlations suggesting that the individuals who fidgeted more (especially when standing) tended to be those with more active lifestyles and lower resting heart rates. We speculate that this pattern may reflect an underlying predisposition for some of us to try and expend more energy than others. Such differences may be achieved via anything from fidgeting to structured exercise, depending on the availability of opportunities for more meaningful physical activity.
Lastly, although it was very encouraging for us that the mainstream media took a keen interest in our study, we were disappointed that some of the headlines unfortunately misinterpreted the results and recommended to the public that they may as well sit down all day. To be clear, a sedentary lifestyle undoubtedly poses major health risks. Limiting sedentary behaviors such as prolonged sitting is advisable. Our findings show that merely rising from your chair to stand on the spot is still just another sedentary behavior; it takes slightly more to lift yourself above the minimum activity level needed for good health.