Visual Feedback Monitoring During Exercise in Individuals With Obesity
Phase: NA
Conditions: Obesity
Sponsor: University of Mississippi Medical Center

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Visual Feedback Monitoring During Exercise in Individuals with Obesity 
 
NCT #: NCT04685707 
 
10/11/2021 
 
 
 
 
 
 
 
 
 
 
 
 
 

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Protocol 
Participants visited the laboratory on two occasions at least one day apart. An exercise modality, 
experimental or control, was randomly assigned to each visit. During the experimental exercise, 
participants were instructed to walk on the treadmill following the movement targets displayed on 
the screen. During the control session, participants were instructed to control treadmill speed (ad 
libitum) to meet a specific target heart rate. Each exercise session involved a baseline measurement 
at preferred walking speed (5 minutes) and two seven-minute trials at 60% HRR (HRR 601 HRR 
602, respectively). HRR was calculated as the difference between the estimated maximal heart rate 
and the resting heart rate. Maximal heart rate was estimated using the 220-age formula (Fox III 
and Naughton 1972), and resting heart rate was measured using the heart rate monitor after at least 
four minutes of seated rest at the beginning of the visit. A 3-minute recovery period, during which 
the participant was sitting, followed each exercise trial and baseline trial.  In the first visit, testing 
commenced with the familiarization of walking on the treadmill while selecting a preferred 
walking speed (PWS) which was used for all testing.  
Before starting the exercise, a static calibration step was used to determine the zero position for 
hip flexion, and a dynamic calibration was used to determine the maximum hip flexion at PWS for 
each participant. During dynamic calibration, participants walked on the treadmill at PWS and 
were instructed to ‘lift their knees as high as possible while walking’ to achieve maximum hip 
flexion. This step was used to set the upper and lower limits for the hip flexion target display 
during the experimental condition. The feedback interface was then introduced and explained. 
Participants were introduced to the visual display and were told what movement related 
information was being given by each indicator. After this introduction, participants were allowed 
to practice with the device until the association between the feedback cues and the corresponding 

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movement features was sufficiently clear. Energy expenditure was evaluated from oxygen 
consumption measured during the exercise and recovery using a breath-by-breath portable 
metabolic analyzer (K5, COSMED, Rome, Italy).  
 
Data Analysis 
Average heart rate (HR) was calculated as the average heart rate during the exercise. Heart rate 
error (HRerr) was calculated as the absolute error between the target heart rate (HRtarget) and the 
actual heart rate. Vo2, HRerr, and HR were calculated during steady-state exercise (i.e., 4 – 7 
minutes of the trial). The means across the two trials (HRR 601, HRR 602) were used. The 
percentage of strides that resulted in tibia peak accelerations above 3g during each exercise trial 
was calculated (TPPA%). The mean peak positive acceleration (TPPA) was calculated as the mean 
tibia PPA across all recorded strides for both sides for each trial above 3g. 
 
 
Statistical Analysis 
A paired sample t-test was used to test for differences between exercise modality (experimental 
and control) at each intensity (baseline, HRR 60) for TPPA, TPPA%, HR, HRerr, and VO2. The 
Shapiro-Wilk Test was used to test the normality of the samples. For the tests where normality 
was violated, Wilcoxon Signed Ranks tests were used. Values that were more than 1.5 times the 
interquartile range away from the upper quartile were considered outliers. Cohen’s d was used to 
calculate effect sizes for parametric tests. Z divided by the square root of the sample size (r) was 
used to calculate effect sizes from the Wilcoxon Signed Ranks tests (Fritz et al. 2012). A 
significance level of 0.05 was used for all statistical testing.