Gary Kamen1, Christopher A Knight. 1. Department of Exercise Science, University of Massachusetts at Amherst, Amherst, MA 01003-9258, USA. kamen@excsci.umass.edu
Abstract
BACKGROUND: This study evaluated changes in motor unit (MU) firing rates in young and older adults during exercise training. METHODS: Vastus lateralis MU discharge rates were measured in 8 young and 7 older adults. Each participant performed isometric knee extension contractions at 10%, 50%, and 100% of maximal voluntary contraction or effort (MVC) on two separate occasions. Participants then completed a 6-week resistance exercise training protocol. RESULTS: Significant increases in maximal force were observed as early as 1 week after the first baseline testing session, and these were accompanied by increases in the MU discharge rate. Exercise training increased maximal voluntary force by 29% and 36% in the young and older adults, respectively. Motor unit discharge rates at 100% of maximal effort were significantly greater in the young (24.7 pps) than in the older adults (17.8 pps). Furthermore, the young adults also exhibited significantly greater discharge rates at 50% MVC, but there were no differences at the 10% force level. Maximal MU discharge rates increased during the 1-week period separating the two initial testing sessions. After the 6-week training period, maximal MU discharge rates were 15% higher for the young adults and 49% higher for the older adults. No changes in discharge rates were observed for either group at 10% or 50% MVC after exercise training. CONCLUSIONS: The early increase in maximal MU discharge rate with repeated maximal force assessment may comprise an important neural mechanism mediating early, rapid gains in muscular force capability.
BACKGROUND: This study evaluated changes in motor unit (MU) firing rates in young and older adults during exercise training. METHODS: Vastus lateralis MU discharge rates were measured in 8 young and 7 older adults. Each participant performed isometric knee extension contractions at 10%, 50%, and 100% of maximal voluntary contraction or effort (MVC) on two separate occasions. Participants then completed a 6-week resistance exercise training protocol. RESULTS: Significant increases in maximal force were observed as early as 1 week after the first baseline testing session, and these were accompanied by increases in the MU discharge rate. Exercise training increased maximal voluntary force by 29% and 36% in the young and older adults, respectively. Motor unit discharge rates at 100% of maximal effort were significantly greater in the young (24.7 pps) than in the older adults (17.8 pps). Furthermore, the young adults also exhibited significantly greater discharge rates at 50% MVC, but there were no differences at the 10% force level. Maximal MU discharge rates increased during the 1-week period separating the two initial testing sessions. After the 6-week training period, maximal MU discharge rates were 15% higher for the young adults and 49% higher for the older adults. No changes in discharge rates were observed for either group at 10% or 50% MVC after exercise training. CONCLUSIONS: The early increase in maximal MU discharge rate with repeated maximal force assessment may comprise an important neural mechanism mediating early, rapid gains in muscular force capability.
Authors: S M Ling; R A Conwit; L Talbot; M Shermack; J E Wood; E M Dredge; M J Weeks; D R Abernethy; E J Metter Journal: Osteoarthritis Cartilage Date: 2007-05-31 Impact factor: 6.576
Authors: Aner Weiss; Anat Mirelman; Nir Giladi; Lisa L Barnes; David A Bennett; Aron S Buchman; Jeffrey M Hausdorff Journal: J Am Med Dir Assoc Date: 2016-09-01 Impact factor: 4.669