Declines in handgrip rapid strength characteristics, which include rate of force development (RFD), are commonly reported as a consequence of aging. These declines have been shown to have a detrimental effect on the functional performance abilities of older adults. Such an effect may be amplified by a further decrease in handgrip RFD as a result of fatigue. Evidence suggests that carrying a heavy grocery bag can elicit fatigue-induced changes in muscle activity and cardiovascular parameters. It is unclear if carrying a heavy grocery bag will elicit fatigue-induced changes in handgrip RFD. PURPOSE: The purpose of this study was to examine the acute effects of carrying a heavy grocery bag on handgrip RFD in young and older women. METHODS: Ten young (age = 22 ± 3 years) and ten older (71 ± 10 years) healthy women performed a control condition and an experimental condition of grocery bag carrying for 3 minutes. The control condition consisted of quiet resting for 3 minutes in a seated position. This condition was performed first to avoid any potential carry-over effects. After completing the control condition, the participants rested for 20 minutes before completing the experimental condition, which consisted of walking at 3.5 km·h-1 on a treadmill for 3 minutes while carrying a heavy grocery bag (5.3 kg) in the dominant hand. Three handgrip maximal voluntary contraction (MVC) assessments were completed immediately before (pretest) and after (posttest) the control and grocery bag carry conditions to determine the acute effects of each condition on RFD. All handgrip MVCs were performed with the dominant hand using a novel strength testing device. This device consisted of a microcomputer and a load cell that was equipped with two semi-cylindrical handles for gripping. For each MVC, participants sat in an upright position and were instructed to squeeze the handles of the load cell “as hard and fast as possible” for 3-4 seconds. Handgrip RFD at 0-100 milliseconds from contraction onset was calculated and displayed by the device at the conclusion of each MVC and was normalized to body mass. A three-way mixed factorial analysis of variance was used to analyze the RFD data. RESULTS: The grocery bag carry condition elicited a significant decrease in RFD for the older women (pretest = 13.7 ± 3.6 N·s-1·kg-1; posttest = 12.7 ± 3.3 N·s-1·kg-1; P < 0.001) but not for the younger women (pretest = 16.8 ± 2.9 N·s-1·kg-1; posttest = 16.8 ± 2.7 N·s-1·kg-1; P = 0.830). No changes in RFD were observed for either age group from pre- (young = 16.9 ± 3.2 N·s-1·kg-1; older = 13.4 ± 3.3 N·s-1·kg-1) to posttest (young = 16.9 ± 2.7 N·s-1·kg-1; older = 13.5 ± 2.9 N·s-1·kg-1) for the control condition (P = 0.721-0.830). CONCLUSION: We found no significant changes in RFD for the younger women; however, for the older women, a significant decrease in RFD was observed as a result of the grocery bag carry condition. These findings suggest that carrying a heavy grocery bag for 3 minutes may impair the handgrip rapid strength capacities of older women.



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