Age-related fatigability of the ankle dorsiflexor muscles during concentric and eccentric contractions. Eur J Appl Physiol
Laboratory of Applied Biology, Université Libre de Bruxelles, 28 avenue P. Héger, CP 168, 1000 Brussels, Belgium. Arbeitsphysiologie
(Impact Factor: 2.19).
07/2007; 100(5):515-25. DOI: 10.1007/s00421-006-0206-9
This study compares the fatigability of the ankle dorsiflexors during five sets of 30 maximal concentric and eccentric contractions in young and elderly adults. The torque produced by the ankle dorsiflexors and the average surface electromyogram (aEMG) of the tibialis anterior were continuously recorded. The contribution of central and peripheral mechanisms to muscle fatigue was tested before, after each set of contractions, and during a 30 min recovery period by the superimposed electrical stimulation method. The compound muscle action potential (M-wave), the mechanical response to single (twitch) and paired (doublet) stimulation, and the postactivation potentiation were also recorded. Compared with young subjects, elderly adults exhibited a greater loss of torque for concentric (50.2 vs. 40.9%; P<0.05) and eccentric (42.1 vs. 27.1%; P < 0.01) contractions. Although young subjects showed a lesser decrease in torque during the eccentric compared with concentric contractions, elderly adults experienced similar fatigability for the two types of contractions despite a comparable depression in the EMG activity of both groups and contraction types (10-20%). As tested by the interpolated-twitch method and aEMG/M-wave ratio, voluntary activation was not altered during either type of contraction or for either age group. During the two fatigue tasks, only elderly adults experienced a decrease in M-wave area (26.4-35.4%; P < 0.05). All together, our results suggest that the fatigue exhibited by both young and elderly adults during maximal concentric and eccentric contractions mainly involved peripheral alterations and that elderly adults may also have experienced a decline in neuromuscular propagation.
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Available from: Geoff Alonzo Power
- "During sustained isometric tasks older adults are often less fatigable than younger adults (Christie et al., 2011) until more advanced ages (Justice et al., 2014), but during constrained velocity (e.g., isokinetic) dynamic tasks older adults exhibit less (Lanza et al., 2004; Rawson, 2010), the same (Callahan et al., 2009; Dalton et al., 2012; Yoon et al., 2013) or more fatigue (Baudry et al., 2007; Callahan et al., 2011). With adult aging there may be a greater dependence on oxidative pathways for energy production (Lanza et al., 2005), perhaps helping to mitigate fatigue "
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ABSTRACT: Older adults are more fatigable than young during dynamic tasks, especially those that involve moderate to fast unconstrained velocity shortening contractions. Rate of torque development (RTD), rate of velocity development (RVD) and rate of neuromuscular activation are time-dependent neuromuscular parameters which have not been explored in relation to age-related differences in fatigability. The purpose was to determine whether these time-dependent measures affect the greater age-related fatigability in peak power during moderately fast and maximal effort shortening plantar flexions. Neuromuscular properties were recorded from 10 old (~78years) and 10 young (~24years) men during 50 maximal-effort unconstrained velocity shortening plantar flexions against a resistance equivalent to 20% maximal voluntary isometric contraction torque. At task termination, peak power, and angular velocity, and torque at peak power were decreased by 30, 18, and 16%, respectively, for the young (p<0.05), and 46, 28, 30% for the old (p<0.05) compared to pre-fatigue values with the old exhibiting greater reductions across all measures (p<0.05). Voluntary RVD and RTD decreased, respectively, by 24 and 26% in the young and by 47 and 40% in the old at task termination, with greater decrements in the old (p<0.05). Rate of neuromuscular activation of the soleus decreased over time for both age groups (~47%; p<0.05), but for the medial gastrocnemius (MG) only the old experienced significant decrements (46%) by task termination. All parameters were correlated strongly with the fatigue-related reduction in peak power (r=0.81-0.94, p<0.05), except for MG and soleus rates of neuromuscular activation (r=0.25-0.30, p>0.10). Fatigue-related declines in voluntary RTD and RVD were both moderately correlated with MG rate of neuromuscular activation (r=0.51-0.52, p<0.05), but exhibited a trend with soleus (r=0.39-0.41, p=0.07-0.09). Thus, time-dependent factors, RVD and RTD, are likely important indicators of intrinsic muscle properties leading to the greater age-related decline in peak power when performing a repetitive dynamic fatigue task, which may be due to greater fatigue-related central impairments for the older men than young.
Available from: Roger Enoka
- "Moreover, the rate of change in muscle length must be similar when comparing the shortening and lengthening phases of a movement due to the influence of movement velocity on central and peripheral afferent feedback, and on the neural activation of muscle (Duchateau and Enoka, 2011). To avoid these confounding factors when comparing muscle activation during the two anisometric contractions, many studies have used isokinetic dynamometers to control the force and joint angular velocity (Aagaard et al., 2000;Amiridis et al., 1996;Babault et al., 2001;Baudry et al., 2007;Beltman et al., 2004;Duclay and Martin, 2005;Duclay et al., 2011;Grabiner and Owings, 2002;Pasquet et al., 2006;Pinniger et al., 2003;Westing et al., 1990). Nonetheless, the strategy employed by the central nervous system (CNS) when resisting the force imposed by a torque motor can differ slightly from that used when lowering an inertial load to match an imposed trajectory (Duchateau and Enoka, 2008). "
Available from: Jia-Hua Lin
- "Callahan, Foulis and Kent-Braun (2009) found that fatigue resistance in the knee extensor muscles was similar among young and older adults during dynamic contractions. Others reported that older adults develop greater fatigue during dynamic contractions (Baudry et al. 2007; Dalton et al. 2010). "
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ABSTRACT: Age may modify the association between occupational physical demand and muscle loading, and ultimately increase the risk of musculoskeletal disorders. The goal of this study was to investigate age-related differences in shoulder muscle fatigue development during a repetitive manual task. Twenty participants in two age groups completed an 80-minute simulated low-intensity assembly task. Electromyographic (EMG) manifestation of muscle fatigue was observed in the upper trapezius, deltoid and infraspinatus muscles in both age groups, and coincided with an increase in the subjective ratings of perceived exertions. Compared with the younger group, older group showed a more monotonic decrease in EMG power frequency in the upper trapezius and deltoid muscles. However, the age-related difference in EMG amplitude was less consistent. Relative rest time of the upper trapezius muscle in the older group was less than the young group throughout the task. The observed patterns of EMG measures suggest that older participants may have disadvantages in fatigue resistance in the upper trapezius and posterior deltoid muscles during the simulated repetitive manual task.
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