This was a poster made for the University of Michigan Rehabilitation Biomechanics laboratory. As the lead for this reliability study, I had to utilize research and leadership skills in order to complete the task on time. This study was examining the day-to-day and within-day reliability of oxygen consumption and heart rate measurements on healthy subjects.

1. ASSESSING INTRA- AND INTER-SESSION RELIABILITY OF
ENERGY EXPENDITURE MEASURES
Audra Davidson, Jasmine Mirdamadi, Deanna H. Gates
School of Kinesiology, University of Michigan, Ann Arbor, MI, USA
DISCUSSION
• Equipment malfunction has prevented the acquisition of more data
• Total of 7 subjects with collected data for day 1
• Total of 4 subjects with collected data for day 1 and day 2
• Preliminary analysis of net VO2 data (see Figure 3) and steady state
heart rate data (see Figure 4) shows day-to-day differences less than
the minimal detectable change values found by Darter et al.1
INTRODUCTION
• Many studies involve measurement of energy expenditure
parameters and heart rate data on multiple days and in multiple
sessions per day
• Assessment of the reliability of the equipment used to collect
this data is necessary to evaluate if changes in energy
expenditure are due to day-to-day variability or true change
• Other researchers have found that net oxygen consumption
data gives the most reliable energy expenditure measures
between days1
• Consistency of intrasession reliability has not been studied with
this equipment
Purpose
Determine the reliability of the K4B2 COSMED system in
measuring energy expenditure parameters and heart rate data
to determine a value of within-day and day-to-day minimal
detectable change
METHODS
Subjects
• 10 healthy subjects ages 18-65 recruited from University of
Michigan Campus
• No history of major surgeries or health problems
Measurements
• Delsys EMG sensors placed on the following:
• Gluteus medius
• Quadriceps (rectus femoris, vastus medialis, vastus
lateralis)
• Lateral hamstrings
• Medial and lateral gastrocnemius
• Soleus
• Tibialis anterior
• Reflective markers placed on major bony landmarks
• Kinematic data measured using motion capture with 24 infrared
cameras
• Oxygen consumption measured using the K4b2 COSMED
system
Collections
• All collections occurred in the early morning
• Subjects arrived fasted, without having consumed caffeine or having
performed any vigorous physical activity prior to collection
Figure 1. A general timeline of a single collection
0
500
1000
1500
2000
0 500 1000 1500 2000 2500 3000
VO2 (mL/min)
Time (s)
S001 VO2 Day 1
Figure 3. Preliminary analysis of net steady state oxygen consumption data
Statistical Analysis
• Within-day reliability will be calculated by running a 2-way random model
of intraclass coefficient4
• Day-to-day reliability will be calculated by first averaging the three
sessions for each day.3 The same 2-way random model of intraclass
coefficient will be performed on the average values of first- and second-day
averages
• Minimal detectable change values for within- and between-day will be
calculated using the standard error and the calculated ICC2
RESULTS
REFERENCES
[1] Darter, B. J., Rodriguez, K. M., & Wilken, J. M. (2013). Test-retest reliability and minimum detectable
change using the K4b2: oxygen consumption, gait efficiency, and heart rate for healthy adults during
submaximal walking. Research quarterly for exercise and sport, 84(2), 223-231.
[2]Gardinier, E. S., Manal, K., Buchanan, T. S., & Snyder-Mackler, L. (2013). Minimum detectable change for
knee joint contact force estimates using an EMG-driven model. Gait & posture, 38(4), 1051-1053.
[3]Mohammadirad, S., Salavati, M., Takamjani, I. E., Akhbari, B., Sherafat, S., Mazaheri, M. et al. (2012). Intra
and intersession reliability of a postural control protocol in athletes with and without anterior cruciate
ligament reconstruction: a dual-task paradigm. International journal of sports physical therapy, 7(6), 627-636.
[4]Weir, J. P. (2005). Quantifying test-retest reliability using the intraclass correlation coefficient and the
SEM. Journal of strength and conditioning research / National Strength & Conditioning Association, 19(1),
231-240.
1st Seated Rest
Duration:
5 minutes
1st Steady State
Walking
Subject acclimates
to the treadmill
Duration:
13 minutes
2nd Seated Rest
Duration:
5 minutes
2nd Steady State
Walking
Subject is assumed
to be acclimated to
the treadmill
Duration:
8 minutes
3rd Seated Rest
Duration:
5 minutes
3rd Steady State
Walking
Duration:
8 minutes
Figure 2. Example of oxygen consumption data obtained from a collection.
Average Steady State Net VO2 Comparison
Day
Subject
S001 S002 S003 S008
Average Net
VO2
(mL/kg/min)
1 7.80 8.01 8.07 7.60
2 8.69 8.78 7.70 6.62
Day-to-Day Difference
(mL/kg/min)
0.89 0.77 0.36 0.98
Darter et al. MDC
(mL/min/kg)
1.43
Average Steady State Heart Rate Comparison
Day
Subject
S001 S002 S003 S008
Average
Steady State
Heart Rate
(BPM)
1 94.46 96.48 79.00 93.87
2 101.92 100.50 81.65 91.61
Day-to-Day Difference
7.46 4.03 2.66 2.26
Darter et al. MDC
(BPM)
10.00
Figure 4. Preliminary analysis of steady state heart rate data
FUTURE AIMS
• Equipment repair will allow more data collections
• Subjects with data for only their first day (n = 3) will have
second-day data collected
• Additional subjects (n = 3) will have first- and second-day
data collected
• Statistical analysis of all subject data will be performed to yield ICC
values for each measure
• Determination of minimal detectable change values will be performed
on VO2 data and heart rate data, as well as the calculated values of
cost of transport and energy expenditure
• Overall reliability of the equipment will be assessed for use in future
studies