Accelerometer Systems
Nina Bondre, Allison Cerutti, Matthew Major, PhD (Faculty Mentor)
Northwestern University Prosthetics-Orthotics Center (NUPOC)
Instrument Description
Advantages
Accelerometers
Clinical Relevance
What is an accelerometer?
How does it work?
A microelectronic-mechanical system (MEMS) produces an output voltage or capacitance
proportional to acceleration.
ActivPAL
• Daily activity separated into periods of
standing, sitting, stepping
• Stepping frequency and estimated
energy expenditure (metabolic
equivalents: METs)
Types of systems:
• Piezoelectric, piezoresistive, or differential capacitance
• Uniaxial, biaxial, or triaxial
How does this relate to gait?
Accelerometers measure acceleration of body segments to which they attach.
• “Whole body”  Attached to waist (approximate whole body center-of-mass location)
• Lower limb  Attached to limb segments (e.g., shin, thigh) or joints (e.g., ankle)
Accelerations are collected and processed to estimate meaningful gait data.
ActivPAL1
• PAL Technologies Ltd. (Glasgow, United Kingdom)
• Attached to thigh with dual-sided adhesive or medical
grade tape
• Continuous data capture up to 14 days
ActivPAL Monitor
Sample Dynaport energy expenditure
report separated by activity type 6
StepWatch Activity Monitor
• Step count and cadence
• Objective justification for K-level
(functional level) assignment
• Estimate service lifetime of device
components
Dynaport MoveMonitor2
• McRoberts (The Hague, The Netherlands)
• Attached to back at L2 with elastic strap
• Continuous data capture up to 7 days
DynaPort Device
StepWatch Activity Monitor3
• OrthoCare Innovations (Oklahoma City, Oklahoma)
• Attached near ankle with strap
• Data capture up 2 months, at one-minute intervals
StepWatch Activity Monitor
G-WALK Device
Device
First Year Cost
Annual Fees
ActivPAL
$1270
(device + docking station &
software)
$148
DynaPort
$1601
(device + software)
$120
G-WALK
Validated Population
Sample G-Studio report: gait
pattern for both legs 4
Sample ActivPal sedentary
vs. upright activity report 5
DynaPort
• Daily activity separated into periods of
standing, sitting, stepping, lying down,
sleep movement
• Estimated energy expenditure (METs)
• Distinguishes intensity of activities (light,
moderate, vigorous, very vigorous)
Able-bodied females
(15-18 yrs)9
Posture + motion during ADLs
(e.g., wash hands, vacuum)
Transitions between sitting,
standing, stepping
Children with Cerebral
Palsy (4-18 yrs)10
Step frequency, ambulation
time
yrs)8
Able-bodied children
(9.9 ± 0.3 yrs)11
Adults with
diabetes13
Transtibial and
transfemoral amputees14
Transfemoral and
transtibial amputees
(47-68 yrs)15
Sample StepWatch “Functional Level
Assessment” report data and partial
step activity data for one day 7
G-WALK
• Gait: Walking speed, cadence, symmetry
index (right-left comparison), stride length,
stance time, swing time, single and double
support times
• Pelvic angles: Sagittal, coronal, and
transverse rotation
• Normative data comparison
Validated Measure
Reported Limitations
N/A
N/A
Accuracy decreased for internal
rotation and sedentary activity
Reduced accuracy during
Ambulation time, standing, treadmill walking & over-ground
transitions, sedentary behavior
running;
not valid for children 4-6 yrs12
Walking speed, cadence, step
time, step length12
N/A
Under- and over-estimated step
time for sound leg and
Step count, step length, mean
prosthetic leg, respectively;
step time, walking speed
Errors in heel strike
identification for analysis of gait
symmetry
Under- or over-estimated steps
during stair climbing
Step count
Able-bodied (24-68 yrs),
with and without casts to
model patients with
diabetic foot ulcers16
Step count
Adults (>55 yrs) with
chronic hemiparetic or
bilateral paretic gait17
Step count
Cost Considerations
Underestimated steps during
Gait: Walking speed, cadence,
bilateral symmetry, stride
Able-bodied young adults
length, stance time, swing
(20-35 yrs)18
time, single and double
support times
Pelvic angles: Sagittal, coronal,
and transverse rotation
stair climbing
N/A
N/A
References
G-WALK4
• BTS Bioengineering Corp. (Brooklyn, NY)
• Positioned at lower back
• Real-time data capture in clinic within 20 meter range
StepWatch Activity
Monitor
Device
Able-bodied (33-53
An instrument used to measure acceleration in up to three planes.
$1995
(device + docking station &
software)
$4500
(device + software)
Potential Considerations
$1200
$250
1. PAL Technologies Ltd (UK). Product Portfolio [Internet]. 2014 [cited 2014 Feb 5]. Available from www.paltech.plus.com/products.htm
2. McRoberts (Netherlands). Dynaport [Internet]. 2014 [cited 2014 Feb 5]. Available from https://www.mcroberts.nl/products
3. Ohio State University (US). OU Medicine: Physical Activity Monitoring [Internet]. 2014 [cited 2014 Feb 5]. Available from http://www.oumedicine.com/pediatrics/department-sections/diabetes-endocrinology/research/pediatricmetabolic-research-program/facilities
4. BTS Bioengineering (Italy). BTS G-Walk [Internet]. 2014 [cited 2014 Feb 5]. Available from http://www.btsbioengineering.com/products/kinematics/bts-g-walk/
5. PAL Technologies Ltd (UK). ActivPal Brochure [Internet]. 2014 [cited 2014 Feb 5]. Available from: www.paltech.plus.com/products.htm
6. McRoberts (Netherlands). Dynaport MoveMonitor [Internet]. 2014 [cited 2014 Feb 5]. Available from https://www.mcroberts.nl/products
7. Orthocare Innovations (US). Stepping beyond K-levels the Functional Level Assessment System [Internet]. 2014 [cited 2014 Feb 5]. Available from http://orthocareinnovations.com/galileo/pdf/GalileoWhitePaper01-10-2011.pdf
8. Grant P, Ryan C, Tigbe W, Granat M. Br J Sports Med. 2006 Dec; 40(12):992-7.
9. Dowd K, Harrington D, Donnelly A. PLoS One. 2012;7(10):e47633.
10. McAloon M, Hutchins S, Twiste M, Jones R, Forchtner S. Prosthet Orthot Int. Epub 2013 Oct 25.
11. Aminian S, Hinckson E. Int J Behav Nutr Phys Act. 2012;9.
12. De Decker E, De Craemer M, Santos-Lozano A, Van Cauwenberghe E, De Bourdeaudhuij. Med Sci Sports Exerc. 2013; 45(10):2002-11.
13. De Bruin E, Hubli M, Hofer P, Wolf P, Murer K, Zijlstra W. J Aging Res. 2012;2012.
14. Houdijk H, Appelman F, Van Velzen J, Van der Woude L, Van Bannekom C. J Rehabil Res Dev. 2008;45(9):1335-42.
15. Coleman KL, Smith DG, Boone DA, Joseph AW, del Aguila MA. J Rehabil Res Dev. 1999 Jan;36(1):8-18.
16. Hartsell H, Fitzpatrick D, Brand R, Frantz R, Saltzman C. J Rehabil Res Dev. 2002 May-Jun;39(3):395-400.
17. Macko RF, Haeuber E, Shaughnessy M, Coleman KL, Boone DA, Smith GV, Silver KH. Med Sci Sports Exerc. 2002 Mar;34(3):394-9.
18. Bugane F, Benedetti MG, Casadio G, Attala S, Biagi F, Manca M, Leardini A. Comput. Methods Programs Biomed. 2012 Oct;108(1):129-37.
Acknowledgements: Poster development supported by the American Academy of Orthotists and Prosthetists Gait Society.