Affiliations: Faculty of Applied Health Sciences, University of
Waterloo, Waterloo, ON, Canada
Note: [] Address for correspondence: Clark Dickerson, 200 University Ave
W, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON,
N2N 1K5 Canada. Tel.: +1 519 888 4567 x37844; Fax: +1 519 746 6776; E-mail:
[email protected]
Abstract: Despite frequent use in industry, job rotation lacks robust
confirmation as an effective method to limit exposure. This study investigated
two tasks that involved the deltoid muscle. We examined two major factors in
the context of muscle fatigue: the presence of rotation between tasks, and the
order of task rotation if rotation was present. Participants performed four
task combinations (coded AA, AB, BA, BB) of two tasks that were intended to
produce fatigue (A: repetitive shoulder flexion; B: repetitive shoulder
abduction). All tested conditions resulted in lower maximum force production
capability (mean range of 78–88% of original strength), in this order of
decreasing magnitude: BB → AB → BA
→ AA, though differences between successive levels were
not always significant. Specific muscle results supported this progression of
strength decreases. For tasks with different muscular demands (AB and BA), it
was less fatiguing to rotate between them than to only perform the more
demanding task (BB). The order of rotation between tasks (AB vs. BA) did not
influence muscle fatigue indicators. These findings help to assess the
effectiveness of rotating between different tasks in reducing muscular fatigue
or exposure. They also indicated a low apparent influence of task order on
terminal fatigue characteristics for the task combinations evaluated.
