POWER – NEUROMUSCULAR – AGING


4 RESEARCH ARTICLES + 1 GRAPHIC – CLICK ON IMAGE TO ENLARGE


AGE-RELATED CHANGES IN THE RATE OF MUSCLE ACTIVATION AND RAPID FORCE CHARACTERISTICS – 2014

PURPOSE & METHODS
– Investigate the effects of aging on the rate of muscle activation and rapid force characteristics of the plantar flexors
– Plantar flexion peak force (PF), absolute (peak, 50, and 100–200 ms), and relative (10 %, 30 %, and 50 %) rate of force development (RFD), the rapid to maximal force ratio (RFD/PF), and the rate of electromyography rise (RER) were examined during an isometric maximal voluntary contraction (MVC)
(A) Young (age = 22 ± 2 years)
(B) Middle-aged (43 ± 2 years)
(C) Old (69 ± 5 years) men
RESULTS
– The old men exhibited lower PF (30.7 % and 27.6 % lower, respectively) and absolute (24.4–55.1 %) and relative (16.4–28.9 %) RFD values compared to the young and middle-aged men
– RER values were similar between the young and old men
– However, RER values were greater for the middle-aged men when compared to the young and old men for the soleus and the old men for the medial gastrocnemius
– Likewise, RFD/PF ratios were similar between young and old men
– However, these ratios were greater for the middle-aged men at early, but not later, time intervals
– The lower PF and absolute and relative RFD values for the old men may contribute to the increased functional limitations often observed in older adults
– Interestingly, higher rates of muscle activation and greater early RFD/PF ratios in middle-aged men may be a reflection of physiological alterations in the neuromuscular system occurring in the fifth decade.

THE NERVOUS SYSTEM – SARCOPENIA & MUSCLE ATROPHY – 2010


Aagaard P1, Suetta C, Caserotti P, Magnusson SP, Kjaer M.
(1) Aging is characterized by:
– loss of spinal motor neurons (MNs)
– reduced insulin-like growth factor I signaling
– elevated amounts of circulating cytokines
– increased cell oxidative stress
(2) The loss of spinal MNs is paralleled by a reduction in muscle fiber number and size (sarcopenia), resulting in impaired mechanical muscle performance
(3) Maximum muscle strength, power, and rate of force development are decreased with aging, even in highly trained master athletes
(4) Impairment in muscle mechanical function is accompanied and partly caused by an age-related loss in neuromuscular function that comprise changes in maximal MN firing frequency, agonist muscle activation, antagonist muscle coactivation, force steadiness, and spinal inhibitory circuitry
(5) Strength training appears to elicit effective countermeasures in elderly individuals even at a very old age (>80 years) by evoking muscle hypertrophy along with substantial changes in neuromuscular function, respectively


IMPAIRED VOLUNTARY NEUROMUSCULAR ACTIVATION LIMITS MUSCLE POWER IN MOBILITY LIMITED OLDER ADULTS – 2010


David J. Clark, Carolynn Patten, […], and Roger A. Fielding
TEST GROUPS
– MH (aged 40–55 years), OH (aged 70–85 years), and OML (aged 70–85 years)
– We determined the effect of movement velocity on torque and power production in older healthy adults (OH) and older mobility–limited (OML) adults relative to middle-aged healthy adults (MH)
RESULTS
(1) Neuromuscular activation was similar b/n middle-aged and older healthy groups
(2) Differences in torque and power were explained predominantly by muscle size
(3) The older mobility–limited group demonstrated marked impairment of torque, power, and agonist muscle activation, with the greatest deficits occurring at the fastest movement velocities
(4) Agonist muscle activation was found to be strongly associated with torque output
CONCLUSIONS
(1) Similar neuromuscular activation between the middle-aged and older healthy groups indicates that impaired voluntary activation is not an obligatory consequence of aging
(2) However, the finding that the mobility-limited group exhibited impaired activation of the agonist quadriceps and concomitant deficits in torque and power output suggests that neuromuscular activation deficits may contribute to compromised mobility function in older adult


ELITE MALE ATHLETES: AGE-RELATED CHANGES IN PERFORMANCE & MUSCLE – 2008


Faulkner JA1, Davis CS, Mendias CL, Brooks SV.
OBJECTIVE
– Address the degree to which the attainment of the status as an elite athlete in different sports ameliorates the known age-related losses in skeletal muscle structure and function
MAIN OUTCOME MEASUREMENTS
– Strength, power, VO2max, and performance
RESULTS
1. For elite athletes in all sports, as for the general population, age-related muscle atrophy begins at about 50 years of age
2. Despite the loss of muscle mass, elite athletes who maintain an active lifestyle age gracefully with few health problems
3. Conversely, those who lapse into inactivity regress toward general population norms for fitness, weight control, and health problems
4. Elite athletes in the dual and team sports have careers that rarely extend into their 30s
CONCLUSIONS
– Lifelong physical activity does not appear to have any impact on the loss in fiber number
– The loss of fibers can be buffered to some degree by hypertrophy of fibers that remain
– It is surprising that the performance of elite athletes in all sports appears to be impaired before the onset of the fiber loss
– Even with major losses in physical capacity and muscle mass, the performance of elite and masters athletes is remarkable


Comments are closed.