Introduction: One of the greatest necessary expenditures of energy during parental care is the need
to carry offspring [1]. Joe Wold and Brendan Truscott understood this struggle when inventing their
patent-pending cross-body sling called “The Life Handle”. The Life Handle was designed with the
intention of making child carrying more comfortable and less stressful on the body, specifically the
upper arm and shoulder. However, there is no previous data or literature quantifying the
biomechanical benefits associated with using the Life Handle for child carrying. Therefore, to better
understand these benefits, surface electromyography (sEMG) readings were acquired and analyzed
from the bicep brachii to detect the percent differences in myoelectric manifestations of muscular
fatigue between using and not using the Life Handle. These methods were developed to test the
hypothesis that the Life Handle reduces the measurable manifestations of fatigue in the bicep brachii
when holding a child.
Materials and Methods: Nine tests of the following procedure approved by the Union College
Human Subjects Review Committee were performed using five female test subjects and four male
test subjects (ages: 19-44). In each test, five sEMG signals were recorded using two Shimmer 3
EMG sensors and six ECG electrodes. Two electrodes were placed directly on the bony prominence
of the participant’s elbow to establish a ground, and the other four were placed on the center of the
bicep brachii approximately 20mm apart. The first signal was the root mean-square of a raw sEMG
obtained as the participant performed a maximum voluntary isometric contraction (MVIC) for the
bicep brachii. This signal was used for normalization. The other four signals for each participant
were obtained while holding a 15lb doll for two seperate 8 minute trials, one with and one without
the aid of the Life Handle. The order of the two separate trials was randomized. For each of the two
separate trials, a five second sEMG signal was recorded at the beginning of the hold and after the
conclusion of eight minutes. In each trial the two signals (pre-hold and post-hold) were imported to
Matlab for processing and analyzing. All signals were sampled at a frequency of 1024 Hz. Each
signal was processed through a bandpass filter and a fast Fourier transform (FFT) was used to extract
the power density spectral (PSD) [2]. From the PSD, the mean and median frequency values of the
pre and post signals were extracted in order to quantify and compare the myoelectric manifestations
of fatigue when using and not using the Life Handle.
Results and Discussion: Significant differences were observed for the mean and median frequency
shift between the pre and post-hold signals obtained from using the Life Handle and those
holding the child traditionally. Figure 1 shows an example of a shift in the frequency range observed
in a trial holding the child traditionally. The average percent difference in the mean
frequency shif
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