Printed with permission from the Cooper Institute
August 15, 2011 07:04 by Karyn Hughes MEd
In the quest to best predict individual daily energy expenditures, scientists have come up with two shoe-based monitors: an embedded accelerometer and pressure sensitive insoles. These two devices produce different metrics that are being used in hopes of best calculating the energy expended by any individual throughout the day. Perhaps you have used a hip accelerometer that not only counted how many steps you took that day, but also estimated your calorie expenditure for the entire day. While the hip accelerometers have been useful monitors for the daily steps we take, they still significantly underestimate the energy costs of standing activities like household tasks, and non weight bearing activities such as cycling. Other attempts to better estimate energy expenditures have included wearing more than one accelerometer or combining them with a heart rate monitor. Unobtrusive devices that can accurately estimate calories burned can be very helpful tools for monitoring and increasing physical activity, resulting in successful weight loss/maintenance and general better health outcomes.
One of the main appeals for the use of the shoe devices is that they are unobtrusive, light weight, easy-to-use, and accurate. Furthermore, a key component in the study of the shoe devices was to develop a posture and activity recognition model. These included sitting, standing, walking, ascending stairs, descending stairs, and cycling. Moreover, the pressure sensitive insoles were included to track range and frequency of foot pressure changes to correlate with the accelerometer data for improved energy expenditure predictions. The study also looked at the plausibility of only needing to provide a pressure sensor in one shoe.
There were 16 participants of varying heights, body mass indexes, and body weights. Participants were not restricted in the way they assumed postures or how they performed activities. The shoe insoles had five pressure sensitive points for the heel, metatarsal bones, and the great toe. The shoe accelerometers and insoles then produced a vector of 1500 measurements or 25 measurements per second.
To compare the shoe devices’ accuracy of energy expenditures during study trials, the rates of oxygen consumption and carbon dioxide production were calculated with the use of a portable respirometry system. The results were very positive. The use of the two devices achieved the needed tracking for activities of daily living that certainly use calories but are not able to be measured accurately with just hip accelerometers or just hear rate monitors because they only measure energy expenditure primarily in the walking postures. The shoe devices were found to be basically “invisible” and may lead to increased use, facilitating the modification of daily activity as needed for weight loss. The results suggest that the use of the shoe devices are at least as accurate or better compared to other, recently proposed methodologies.
Discussion: A key concept in this article is the fact that people need feedback on their lifestyle behaviors (e.g., physical activity) and research clearly shows that behaviors that are monitored in some fashion (diet logs, physical activity logs, pedometers, etc.) lead to successful maintenance of healthy behaviors. For more on this read our previous blog, “Log It to Lose Weight.” Tracking, logging, or monitoring devices help us “self correct” our behaviors and support consistent behavior change that leads to healthier lives. It will be interesting to see if the shoe-based activity monitors studied here enter the marketplace and if so, how affordable they will be for Americans.
1Sazonova, N., Browning, R.C., & Sazonov, E. (2011). Accurate prediction of energy expenditure using a shoe-based activity monitor. Medicine & Science in Sports & Exercise, 43(7), 1312-1321.