Effects of neuromuscular fatigue on the electromechanical delay of the leg extensors and flexors in young and old men

Conchola, Eric C.; Thompson, Brennan J.; Smith, Doug B.

doi:10.1007/s00421-013-2675-y

Cited by 38 publications

(70 citation statements)

References 56 publications

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“…Differences in electromechanical delay across muscles is a more complicated issue (Corcos et al, 1992;Hug et al, 2011). While studies have shown that the delay may be muscle dependent (Conchola et al, 2013), we were able to achieve sufficiently accurate timing of joint moments and powers without such added complexity. Furthermore, previous studies have used a single electromechanical delay across muscles and subjects and obtained reasonable results (Lloyd and Besier, 2003;Arnold et al, 2013).…”

Section: Electromyography Parameter Optimizationmentioning

confidence: 85%

Muscle-tendon mechanics explain unexpected effects of exoskeleton assistance on metabolic rate during walking

Jackson

Dembia

Delp

et al. 2017

Journal of Experimental Biology

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The goal of this study was to gain insight into how ankle exoskeletons affect the behavior of the plantarflexor muscles during walking. Using data from previous experiments, we performed electromyographydriven simulations of musculoskeletal dynamics to explore how changes in exoskeleton assistance affected plantarflexor muscletendon mechanics, particularly for the soleus. We used a model of muscle energy consumption to estimate individual muscle metabolic rate. As average exoskeleton torque was increased, while no net exoskeleton work was provided, a reduction in tendon recoil led to an increase in positive mechanical work performed by the soleus muscle fibers. As net exoskeleton work was increased, both soleus muscle fiber force and positive mechanical work decreased. Trends in the sum of the metabolic rates of the simulated muscles correlated well with trends in experimentally observed whole-body metabolic rate (R 2 =0.9), providing confidence in our model estimates. Our simulation results suggest that different exoskeleton behaviors can alter the functioning of the muscles and tendons acting at the assisted joint. Furthermore, our results support the idea that the series tendon helps reduce positive work done by the muscle fibers by storing and returning energy elastically. We expect the results from this study to promote the use of electromyography-driven simulations to gain insight into the operation of muscle-tendon units and to guide the design and control of assistive devices.

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Section: Electromyography Parameter Optimizationmentioning

confidence: 85%

Muscle-tendon mechanics explain unexpected effects of exoskeleton assistance on metabolic rate during walking

Jackson

Dembia

Delp

et al. 2017

Journal of Experimental Biology

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“…The process of muscle contraction involves an electromechanical delay (EMD), which is traditionally measured as the time lapse between the onsets of electrical activity and force production . Previous studies demonstrated that EMD is an effective and useful measure for assessing changes associated with muscle fatigue, muscle damage, musculotendinous stiffness, aging, and identification of gender‐related physiological and functional differences . EMD is thought to be influenced by several factors, including propagation of action potentials across the muscle membrane, excitation‐contraction coupling (EC‐C), and stretching of the series elastic component (SEC) .…”

mentioning

confidence: 99%

Effects of neuromuscular fatigue on electromechanical delay of the leg extensors and flexors in young men and women

et al. 2015

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“…There are conflicting reports about the influence of fatiguing exercise on EMD. Some studies have indicated that fatigue imposed by isometric [17], eccentric and concentric isokinetic contractions [34] leads to strength loss, which augments the EMD. However, as demonstrated in ours and other studies [39] neither of the assessed muscles had their EMD compromised by downhill running.…”

Section: Discussionmentioning

confidence: 99%

“…In fact, Conchola et al [17] showed that fatigue induced by intermittent isometric contractions lengthened both the KF and KE EMD. However, this lengthening lasted longer for the KF than for the KE.…”

Section: Introductionmentioning

confidence: 99%

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Moderate intensity and volume downhill run does not impair knee joint stability at early and late phases of quadriceps/hamstrings contraction

Assumpção

Lima

Oliveira

et al. 2014

IES

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BACKGROUND AND OBJECTIVE: Muscle strength imbalance can be an important factor in hamstrings muscle strain. The main purpose of this study was to investigate the effects of downhill running on hamstrings/quadriceps torque (H/Qtorque) and the electromechanical delay (H/QEMD) ratios. METHODS: Fifteen active male individuals performed two maximal voluntary isometric contractions of the knee extensors and knee flexors, from which the maximal muscle torque, EMD and H/Qtorque and H/QEMD ratios were extracted. Thereafter, the participants performed a 30-minute downhill run (−16%) at 70% VO2max. Dependent variables were assessed immediately before, immediately following and 48 hours after the effort. RESULTS: Maximal isometric torque decreased significantly immediately after the downhill run for both the extensors (pre: 271.8 ± 45.9 N·m; post: 235.5 ± 55.7 N·m) and flexors (pre: 112.2 ± 26.3 N·m; post: 97.7 ± 27.2 N·m). No significant difference was identified over time for the EMD of the vastus lateralis and biceps femoris muscles. The H/Qtorque and H/QEMD ratios were not influenced by the downhill run. CONCLUSION: We have demonstrated that moderate intensity and volume downhill run does not impair knee joint stability at early (H/QEMD) and late phases (H/Qtorque) of quadriceps/hamstrings contraction.

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Effects of neuromuscular fatigue on the electromechanical delay of the leg extensors and flexors in young and old men

Cited by 38 publications

References 56 publications

Muscle-tendon mechanics explain unexpected effects of exoskeleton assistance on metabolic rate during walking

Muscle-tendon mechanics explain unexpected effects of exoskeleton assistance on metabolic rate during walking

Effects of neuromuscular fatigue on electromechanical delay of the leg extensors and flexors in young men and women

Moderate intensity and volume downhill run does not impair knee joint stability at early and late phases of quadriceps/hamstrings contraction

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