Age-related fatigability of the ankle dorsiflexor muscles during concentric and eccentric contractions

ArticleinArbeitsphysiologie 100(5):515-25 · July 2007with19 Reads
DOI: 10.1007/s00421-006-0206-9 · Source: PubMed
Abstract
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.
    • "The greater age-related fatigability reported here is in agreement with previous studies focusing on unconstrained velocity shortening contractions (i.e., maximal-effort contractions against a fixed external load) (Dalton et al., 2015Dalton et al., , 2012 McNeil and Rice, 2007; Petrella et al., 2005) as well as fast isokinetic contractions (Callahan et al., 2011). Age-related slowing of muscular contractile characteristics (Dalton et al., 2012Dalton et al., , 2010), reduced sarcolemma excitability (Baudry et al., 2007; Dalton et al., 2010), more compliant tendons (Magnusson et al., 2008), and higher metabolic cost per contraction (Layec et al., 2014) may contribute to the greater fatigability of the old men. Previously we reported that angular velocity was a critical component for age-related differences in plantar flexor fatigue (Dalton et al., 2010). "
    [Show abstract] [Hide abstract] 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.
    Full-text · Article · Feb 2016
    • "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). "
    [Show abstract] [Hide abstract] ABSTRACT: A number of studies over the last few decades have established that the control strategy employed by the nervous system during lengthening (eccentric) differs from those used during shortening (concentric) and isometric contractions. The purpose of this review is to summarize current knowledge on the neural control of lengthening contractions. After a brief discussion of methodological issues that can confound the comparison between lengthening and shortening actions, the review provides evidence that untrained individuals are usually unable to fully activate their muscles during a maximal lengthening contraction and that motor unit activity during submaximal lengthening actions differs from that during shortening actions. Contrary to common knowledge, however, more recent studies have found that the recruitment order of motor units is similar during submaximal shortening and lengthening contractions, but that discharge rate is systematically lower during lengthening actions. Subsequently, the review examines the mechanisms responsible for the specific control of maximal and submaximal lengthening contractions as reported by recent studies on the modulation of cortical and spinal excitability. As similar modulation has been observed regardless of contraction intensity, it appears that spinal and corticospinal excitability are reduced during lengthening compared with shortening and isometric contractions. Nonetheless, the modulation observed during lengthening contractions is mainly attributable to inhibition at the spinal level.
    Full-text · Article · Jan 2016
    • "Whether and how this agerelated shift toward a greater reliance on torque alters the fatigue and recovery responses have not been explored. Studies that used constrained velocity (i.e., isokinetic) tasks and thus defined fatigue as a loss of torque have reported the same (Laforest et al. 1990; Callahan et al. 2009; Dalton et al. 2012), less (Lanza et al. 2004; Rawson 2010), or more (Baudry et al. 2007; Callahan and Kent-Braun 2011) fatigue in older adults compared with young. Explaining the variability among these studies that used isokinetic tasks, and in comparison with those that have used isotonic tasks, is challenging due to the range of angular velocities tested. "
    [Show abstract] [Hide abstract] ABSTRACT: The underlying factors related to the divergent findings of age-related fatigue for dynamic tasks are not well understood. The purpose here was to investigate age-related fatigability and recovery between a repeated constrained (isokinetic) and an unconstrained velocity (isotonic) task, in which participants performed fatiguing contractions at the velocity (isokinetic) or resistance (isotonic) corresponding with maximal power. To compare between tasks, isotonic torque–power relationships were constructed prior to and following both fatiguing tasks and during short-term recovery. Contractile properties were recorded from 9 old (~75 years) and 11 young (~25 years) men during three testing sessions. In the first session, maximal power was assessed, and sessions 2 and 3 involved an isokinetic or an isotonic concentric fatigue task performed until maximal power was reduced by 40 %. Compared with young, the older men performed the same number of contractions to task failure for the isokinetic task (~45 contractions), but 20 % fewer for the isotonic task (p < 0.05). Regardless of age and task, maximal voluntary isometric contraction strength, angular velocity, and power were reduced by ~30, ~13, and ~25 %, respectively, immediately following task failure, and only isometric torque was not recovered fully by 10 min. In conclusion, older men are more fatigable than the young when performing a repetitive maximal dynamic task at a relative resistance (isotonic) but not an absolute velocity (isokinetic), corresponding to maximal power
    Full-text · Article · May 2015
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