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A Comparison of the Effects of Shoulder Muscle Fatigue Caused by Sustained Overhead Activity on Scapulothoracic Kinematics in Younger and Older Populations.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	A Comparison of the Effects of Shoulder Muscle Fatigue Caused by Sustained Overhead Activity on Scapulothoracic Kinematics in Younger and Older Populations./
作者:	Snyder, Jeffrey J.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2019,
面頁冊數:	113 p.
附註:	Source: Dissertations Abstracts International, Volume: 81-03, Section: B.
Contained By:	Dissertations Abstracts International81-03B.
標題:	Biomechanics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13811150
ISBN:	9781085674577

A Comparison of the Effects of Shoulder Muscle Fatigue Caused by Sustained Overhead Activity on Scapulothoracic Kinematics in Younger and Older Populations.
Snyder, Jeffrey J.

A Comparison of the Effects of Shoulder Muscle Fatigue Caused by Sustained Overhead Activity on Scapulothoracic Kinematics in Younger and Older Populations. - Ann Arbor : ProQuest Dissertations & Theses, 2019 - 113 p.

Source: Dissertations Abstracts International, Volume: 81-03, Section: B.

Thesis (Ph.D.)--New York University, 2019.

This item must not be sold to any third party vendors.

Introduction: The population of aging workers is growing exponentially as many industrialized nations are experiencing a demographic shift. Older workers could have additional risk factors when attempting to meet the same physical work demands of their younger coworkers. This includes the static overhead loading that can lead to the occurrence of shoulder musculoskeletal disorders (MSDs). Understanding the effects of fatigue on the younger versus older workforce is essential for the prevention of MSDs. Previous studies on scapulothoracic kinematic changes and their relationship to shoulder MSDs have neither examined the effects of sustained static overhead loading commonly found in the workplace nor any variations that may exist between younger and older populations. However, scapulothoracic kinematic changes have been observed with muscle fatigue in younger populations. The objectives of this study were: 1) to investigate the effect of shoulder muscle fatigue caused by sustained overhead activity on scapulothoracic kinematic changes in order to compare kinematic and time to fatigue differences in younger and older populations; and 2) to determine if the Borg Scale of Perceived Exertion could be used as a prediction tool for the onset of muscle fatigue during a sustained overhead shoulder task.Methods: Sixteen healthy subjects with equal representation of gender and age group (Young: 18-30 years and Older: ≥ 60 years) participated in a sustained overhead fatigue task. Using their dominant arm, measures were collected for scapular kinematics at 90 and 120 degrees of arm elevation before and after the fatigue task, subjective levels of perceived exertion (LPE), electromyography (EMG) median power frequency (MPF) shifts in shoulder muscles before and after the fatigue task and participation time in the fatigue task. Comparisons were made between the age groups for each measure and a correlation analysis between the LPE ratings and the MPF shift in the upper trapezius muscle was also performed.Results: Subjects had a mean age of 25.3 (4.8) years in the Younger and 67.5 (4.3) years in the Older Group. These two groups began their movements with statistically equal baseline kinematics (p = 0.21 for external rotation (ER) at 90°, p = 0.36 for ER at 120°, p = 0.53 for upward rotation (UR) at 90°, p = 0.54 for UR at 120°, p = 0.36 for posterior rotation (PT) at 90° and p = 0.92 for PT at 120°. There was no main effect for age on scapulothoracic rotation (p = 0.65) and there were no differences between age groups for any kinematic measure before and after the fatigue task at either level of arm elevation (p = 0.73 for ER at 90°, p = 0.73 for ER at 120°, p = 0.74 for UR at 90°, p = 0.45 for UR at 120°, p = 0.70 for PT at 90° and p = 0.54 for PT at 120°). Total time to fatigue was 16:13 (06:03) minutes for younger and 29:00 (21:24) for older subjects. While older subjects participated in the fatigue task for 80% longer than younger subjects, the difference was not significant (p = 0.14). When correlating LPE ratings with age combined MPF shifts in the upper trapezius muscle, a strong negative correlation of 0.53 was demonstrated (p = 0.02). The same analysis by separate age groups produced a moderate negative correlation of R2 = 0.40 that was significant (p = 0.05) for the Younger Group and a weak positive correlation of R2 = 0.19 for the Older Group that was not significant (p = 0.34).Discussion: Subjects began their scapulothoracic movements with equal baseline kinematics but no change in their kinematics occurred at the shoulder elevation points within or between either age group subsequent to the fatigue task. The requisite amount of MPF shift (i.e. physiologic muscle fatigue) did not occur in all of the muscles for any subject in either age group. It is believed that this occurred primarily because the work performed by many non-monitored shoulder and trunk muscles to stabilize the arms overhead resulted in the subject's fatigue and LPE report and likely overshadowed the work of the monitored shoulder muscles. Multiple other explanations for the incomplete MPF reductions exist, including the Borg scale perhaps being more appropriate for short-term physical tasks, MPF being more appropriate for contraction levels in excess of 23-30% MVC, and MPF increases occurring due to sarcolemma changes subsequent to temperature increases during long duration muscle contractions. The greater mean participation time of older subjects in the fatigue task supports previous studies using similar low load and sustained activities, but the difference between age groups (29:00 vs. 16:13 min:sec) was not significant. Fatigue perception may also have been influenced by psychological or other-than muscle physiologic factors. Support is provided for alternate metrics to be used in future studies for the assessment of both muscle fatigue and perceived fatigue. Improved metrics will likely reduce data variance and result in greater power in data analysis. Future similar studies are needed and should incorporate these alternate concepts in their methods to more comprehensively assess if scapulothoracic kinematic differences occur between age groups following sustained low-load overhead tasks.

ISBN: 9781085674577Subjects--Topical Terms:

548685
Biomechanics.

A Comparison of the Effects of Shoulder Muscle Fatigue Caused by Sustained Overhead Activity on Scapulothoracic Kinematics in Younger and Older Populations.
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245 1 0 $a A Comparison of the Effects of Shoulder Muscle Fatigue Caused by Sustained Overhead Activity on Scapulothoracic Kinematics in Younger and Older Populations.
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520 $a Introduction: The population of aging workers is growing exponentially as many industrialized nations are experiencing a demographic shift. Older workers could have additional risk factors when attempting to meet the same physical work demands of their younger coworkers. This includes the static overhead loading that can lead to the occurrence of shoulder musculoskeletal disorders (MSDs). Understanding the effects of fatigue on the younger versus older workforce is essential for the prevention of MSDs. Previous studies on scapulothoracic kinematic changes and their relationship to shoulder MSDs have neither examined the effects of sustained static overhead loading commonly found in the workplace nor any variations that may exist between younger and older populations. However, scapulothoracic kinematic changes have been observed with muscle fatigue in younger populations. The objectives of this study were: 1) to investigate the effect of shoulder muscle fatigue caused by sustained overhead activity on scapulothoracic kinematic changes in order to compare kinematic and time to fatigue differences in younger and older populations; and 2) to determine if the Borg Scale of Perceived Exertion could be used as a prediction tool for the onset of muscle fatigue during a sustained overhead shoulder task.Methods: Sixteen healthy subjects with equal representation of gender and age group (Young: 18-30 years and Older: ≥ 60 years) participated in a sustained overhead fatigue task. Using their dominant arm, measures were collected for scapular kinematics at 90 and 120 degrees of arm elevation before and after the fatigue task, subjective levels of perceived exertion (LPE), electromyography (EMG) median power frequency (MPF) shifts in shoulder muscles before and after the fatigue task and participation time in the fatigue task. Comparisons were made between the age groups for each measure and a correlation analysis between the LPE ratings and the MPF shift in the upper trapezius muscle was also performed.Results: Subjects had a mean age of 25.3 (4.8) years in the Younger and 67.5 (4.3) years in the Older Group. These two groups began their movements with statistically equal baseline kinematics (p = 0.21 for external rotation (ER) at 90°, p = 0.36 for ER at 120°, p = 0.53 for upward rotation (UR) at 90°, p = 0.54 for UR at 120°, p = 0.36 for posterior rotation (PT) at 90° and p = 0.92 for PT at 120°. There was no main effect for age on scapulothoracic rotation (p = 0.65) and there were no differences between age groups for any kinematic measure before and after the fatigue task at either level of arm elevation (p = 0.73 for ER at 90°, p = 0.73 for ER at 120°, p = 0.74 for UR at 90°, p = 0.45 for UR at 120°, p = 0.70 for PT at 90° and p = 0.54 for PT at 120°). Total time to fatigue was 16:13 (06:03) minutes for younger and 29:00 (21:24) for older subjects. While older subjects participated in the fatigue task for 80% longer than younger subjects, the difference was not significant (p = 0.14). When correlating LPE ratings with age combined MPF shifts in the upper trapezius muscle, a strong negative correlation of 0.53 was demonstrated (p = 0.02). The same analysis by separate age groups produced a moderate negative correlation of R2 = 0.40 that was significant (p = 0.05) for the Younger Group and a weak positive correlation of R2 = 0.19 for the Older Group that was not significant (p = 0.34).Discussion: Subjects began their scapulothoracic movements with equal baseline kinematics but no change in their kinematics occurred at the shoulder elevation points within or between either age group subsequent to the fatigue task. The requisite amount of MPF shift (i.e. physiologic muscle fatigue) did not occur in all of the muscles for any subject in either age group. It is believed that this occurred primarily because the work performed by many non-monitored shoulder and trunk muscles to stabilize the arms overhead resulted in the subject's fatigue and LPE report and likely overshadowed the work of the monitored shoulder muscles. Multiple other explanations for the incomplete MPF reductions exist, including the Borg scale perhaps being more appropriate for short-term physical tasks, MPF being more appropriate for contraction levels in excess of 23-30% MVC, and MPF increases occurring due to sarcolemma changes subsequent to temperature increases during long duration muscle contractions. The greater mean participation time of older subjects in the fatigue task supports previous studies using similar low load and sustained activities, but the difference between age groups (29:00 vs. 16:13 min:sec) was not significant. Fatigue perception may also have been influenced by psychological or other-than muscle physiologic factors. Support is provided for alternate metrics to be used in future studies for the assessment of both muscle fatigue and perceived fatigue. Improved metrics will likely reduce data variance and result in greater power in data analysis. Future similar studies are needed and should incorporate these alternate concepts in their methods to more comprehensively assess if scapulothoracic kinematic differences occur between age groups following sustained low-load overhead tasks.
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