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James M Wakeling - One of the best experts on this subject based on the ideXlab platform.

  • task dependent Recruitment across ankle extensor muscles and between mechanical demands is driven by the metabolic cost of muscle contraction
    Journal of the Royal Society Interface, 2021
    Co-Authors: Adrian K M Lai, Andrew A Biewener, Taylor J M Dick, James M Wakeling
    Abstract:

    The nervous system is faced with numerous strategies for recruiting a large number of Motor Units within and among muscle synergists to produce and control body movement. This is challenging, considering multiple combinations of Motor Unit Recruitment may result in the same movement. Yet vertebrates are capable of performing a wide range of movement tasks with different mechanical demands. In this study, we used an experimental human cycling paradigm and musculoskeletal simulations to test the theory that a strategy of prioritizing the minimization of the metabolic cost of muscle contraction, which improves mechanical efficiency, governs the Recruitment of Motor Units within a muscle and the coordination among synergist muscles within the limb. Our results support our hypothesis, for which measured muscle activity and model-predicted muscle forces in soleus-the slower but stronger ankle plantarflexor-is favoured over the weaker but faster medial gastrocnemius (MG) to produce plantarflexor force to meet increased load demands. However, for faster-contracting speeds induced by faster-pedalling cadence, the faster MG is favoured. Similar Recruitment patterns were observed for the slow and fast fibres within each muscle. By contrast, a commonly used modelling strategy that minimizes muscle excitations failed to predict force sharing and known physiological Recruitment strategies, such as orderly Motor Unit Recruitment. Our findings illustrate that this common strategy for recruiting Motor Units within muscles and coordination between muscles can explain the control of the plantarflexor muscles across a range of mechanical demands.

  • metabolic cost underlies task dependent variations in Motor Unit Recruitment
    Journal of the Royal Society Interface, 2018
    Co-Authors: Adrian K M Lai, Andrew A Biewener, James M Wakeling
    Abstract:

    Mammalian skeletal muscles are comprised of many Motor Units, each containing a group of muscle fibres that have common contractile properties: these can be broadly categorized as slow and fast twi...

  • Recruitment of faster Motor Units is associated with greater rates of fascicle strain and rapid changes in muscle force during locomotion
    The Journal of Experimental Biology, 2013
    Co-Authors: Sabrina S M Lee, Andrew A Biewener, Maria De Boef Miara, Allison S Arnold, James M Wakeling
    Abstract:

    Animals modulate the power output needed for different locoMotor tasks by changing muscle forces and fascicle strain rates. To generate the necessary forces, appropriate Motor Units must be recruited. Faster Motor Units have faster activation–deactivation rates than slower Motor Units, and they contract at higher strain rates; therefore, Recruitment of faster Motor Units may be advantageous for tasks that involve rapid movements or high rates of work. This study identified Motor Unit Recruitment patterns in the gastrocnemii muscles of goats and examined whether faster Motor Units are recruited when locoMotor speed is increased. The study also examined whether locoMotor tasks that elicit faster (or slower) Motor Units are associated with increased (or decreased) in vivo tendon forces, force rise and relaxation rates, fascicle strains and/or strain rates. Electromyography (EMG), sonomicrometry and muscle-tendon force data were collected from the lateral and medial gastrocnemius muscles of goats during level walking, trotting and galloping and during inclined walking and trotting. EMG signals were analyzed using wavelet and principal component analyses to quantify changes in the EMG frequency spectra across the different locoMotor conditions. Fascicle strain and strain rate were calculated from the sonomicrometric data, and force rise and relaxation rates were determined from the tendon force data. The results of this study showed that faster Motor Units were recruited as goats increased their locoMotor speeds from level walking to galloping. Slow inclined walking elicited EMG intensities similar to those of fast level galloping but different EMG frequency spectra, indicating that Recruitment of the different Motor Unit types depended, in part, on characteristics of the task. For the locoMotor tasks and muscles analyzed here, Recruitment patterns were generally associated with in vivo fascicle strain rates, EMG intensity and tendon force. Together, these data provide new evidence that changes in Motor Unit Recruitment have an underlying mechanical basis, at least for certain locoMotor tasks.

  • Motor Unit Recruitment patterns 2 the influence of myoelectric intensity and muscle fascicle strain rate
    The Journal of Experimental Biology, 2008
    Co-Authors: Emma F Hodsontole, James M Wakeling
    Abstract:

    To effectively meet the force requirements of a given movement an appropriate number and combination of Motor Units must be recruited between and within muscles. Orderly Recruitment of Motor Units has been shown to occur in a wide range of skeletal muscles, however, alternative strategies do occur. Faster Motor Units are better suited to developing force rapidly, and produce higher mechanical power with greater efficiency at faster shortening strain rates than slower Motor Units. As the frequency content of the myoelectric signal is related to the fibre type of the active Motor Units, we hypothesised that, in addition to an association between myoelectric frequency and intensity, there would be a significant association between muscle fascicle shortening strain rate and myoelectric frequency content. Myoelectric and sonomicrometric data were collected from the three ankle extensor muscles of the rat hind limb during walking and running. Myoelectric signals were analysed using wavelet transformation and principal component analysis to give a measure of the signal frequency content. Sonomicrometric signals were analysed to give measures of muscle fascicle strain and strain rate. The relationship between myoelectric frequency and both intensity and muscle fascicle strain rate was found to change across the time course of a stride, with differences also occurring in the strength of the associations between and within muscles. In addition to the orderly Recruitment of Motor Units, a mechanical strategy of Motor Unit Recruitment was therefore identified. Motor Unit Recruitment is therefore a multifactorial phenomenon, which is more complex than typically thought.

  • muscle fibre Recruitment can respond to the mechanics of the muscle contraction
    Journal of the Royal Society Interface, 2006
    Co-Authors: James M Wakeling, Katrin Uehli, Antra I Rozitis
    Abstract:

    This study investigates the Motor Unit Recruitment patterns between and within muscles of the triceps surae during cycling on a stationary ergometer at a range of pedal speeds and resistances. Muscle activity was measured from the soleus (SOL), medial gastrocnemius (MG) and lateral gastrocnemius (LG) using surface electromyography (EMG) and quantified using wavelet and principal component analysis. Muscle fascicle strain rates were quantified using ultrasonography, and the muscle–tendon Unit lengths were calculated from the segmental kinematics. The EMG intensities showed that the body uses the SOL relatively more for the higher-force, lower-velocity contractions than the MG and LG. The EMG spectra showed a shift to higher frequencies at faster muscle fascicle strain rates for MG: these shifts were independent of the level of muscle activity, the locoMotor load and the muscle fascicle strain. These results indicated that a selective Recruitment of the faster Motor Units occurred within the MG muscle in response to the increasing muscle fascicle strain rates. This preferential Recruitment of the faster fibres for the faster tasks indicates that in some circumstances Motor Unit Recruitment during locomotion can match the contractile properties of the muscle fibres to the mechanical demands of the contraction.

Toru Fukubayashi - One of the best experts on this subject based on the ideXlab platform.

  • relationship between quadriceps femoris muscle volume and muscle torque at least 18 months after anterior cruciate ligament reconstruction
    Scandinavian Journal of Medicine & Science in Sports, 2012
    Co-Authors: Yu Konishi, Toshiaki Oda, Satoshi Tsukazaki, Ryuta Kinugasa, Toru Fukubayashi
    Abstract:

    The purpose of this study was to evaluate Motor Unit Recruitment in the quadriceps femoris (QF) after anterior cruciate ligament (ACL) rupture and repair. Subjects included 24 patients at ≥ 18 months after ACL reconstruction and 22 control subjects with no history of knee injury. A series of cross-sectional magnetic resonance images were obtained to compare the QF of patients' injured side with that of their uninjured sides and that of uninjured control subjects. Muscle torque per muscle volume was calculated as isokinetic peak torque divided by QF muscle volume (cm(3)). The mean muscle torque per Unit volume of the injured side of patients was not significantly different from that of the uninjured side or control subjects (one-way ANOVA) Results of the present study were contrary to the results of a previous study that evaluated patients at ≤ 12 months after ACL reconstruction. The present study found that high-threshold Motor Unit Recruitment was restored at ≥ 18 months after ACL reconstruction. Thus, clinicians must develop techniques that increase the Recruitment of high-threshold Motor Units in the QF from the period immediately after the injury until approximately 18 months after ACL reconstruction.

  • relationship between quadriceps femoris muscle volume and muscle torque after anterior cruciate ligament rupture
    Knee Surgery Sports Traumatology Arthroscopy, 2011
    Co-Authors: Yu Konishi, Toshiaki Oda, Satoshi Tsukazaki, Ryuta Kinugasa, Norikazu Hirose, Toru Fukubayashi
    Abstract:

    The purpose of this study was to obtain evidence to support the hypothesis that Motor Unit Recruitment is reduced in the quadriceps femoris (QF) of patients with ACL rupture. We compared muscle torque per Unit volume in the QF from injured and uninjured sides to normal subjects. If high-threshold Motor Unit Recruitment is reduced in patients with ACL rupture, this reduction will theoretically lead to a reduction in muscle torque per Unit volume compared to the control group. The subjects included 22 patients with ACL rupture and 22 subjects with no history of knee injury. To identify the muscle torque per Unit volume, the isokinetic peak torque was divided by QF volume which was obtained by MRI. Tests revealed that the mean muscle torque per Unit volume of the uninjured and injured sides was significantly lower than those of the control group. This study demonstrated that the values of the muscle torque per Unit volume of both injured and uninjured sides of patients with ACL rupture were significantly lower than those of the control group, thereby providing indirect evidence of the hindrance of Motor Unit Recruitment in these patients. The results of the present study also indicate that there may be bilateral QF weakness in patients with ACL rupture. Since persistent QF weakness is a significant barrier to effective rehabilitation in patients with ACL injuries, a better understanding of the underlying mechanisms will allow clinicians and scientists to develop more effective therapeutic strategies for patient rehabilitation.

  • relationship between quadriceps femoris muscle volume and muscle torque after anterior cruciate ligament repair
    Scandinavian Journal of Medicine & Science in Sports, 2007
    Co-Authors: Yu Konishi, K Ikeda, A Nishino, M Sunaga, Y Aihara, Toru Fukubayashi
    Abstract:

    Purpose The purpose of this study was to obtain evidence to support the hypothesis that Motor Unit Recruitment is reduced in the quadriceps femoris (QF) of patients with ACL rupture.

David F Collins - One of the best experts on this subject based on the ideXlab platform.

  • Motor Unit Recruitment when neuromuscular electrical stimulation is applied over a nerve trunk compared with a muscle belly triceps surae
    Journal of Applied Physiology, 2011
    Co-Authors: Austin J Bergquist, Joanna M Clair, David F Collins
    Abstract:

    Neuromuscular electrical stimulation (NMES) can be delivered over a nerve trunk or muscle belly and can generate contractions by activating Motor (peripheral pathway) and sensory (central pathway) axons. In the present experiments, we compared the peripheral and central contributions to plantar flexion contractions evoked by stimulation over the tibial nerve vs. the triceps surae muscles. Generating contractions through central pathways follows Henneman's size principle, whereby low-threshold Motor Units are activated first, and this may have advantages for rehabilitation. Statistical analyses were performed on data from trials in which NMES was delivered to evoke 10-30% maximum voluntary torque 2-3 s into the stimulation (Time(1)). Two patterns of stimulation were delivered: 1) 20 Hz for 8 s; and 2) 20-100-20 Hz for 3-2-3 s. Torque and soleus electromyography were quantified at the beginning (Time(1)) and end (Time(2); 6-7 s into the stimulation) of each stimulation train. H reflexes (central pathway) and M waves (peripheral pathway) were quantified. Motor Unit activity that was not time-locked to each stimulation pulse as an M wave or H reflex ("asynchronous" activity) was also quantified as a second measure of central Recruitment. Torque was not different for stimulation over the nerve or the muscle. In contrast, M waves were approximately five to six times smaller, and H reflexes were approximately two to three times larger during NMES over the nerve vs. the muscle. Asynchronous activity increased by 50% over time, regardless of the stimulation location or pattern, and was largest during NMES over the muscle belly. Compared with NMES over the triceps surae muscles, NMES over the tibial nerve produced contractions with a relatively greater central contribution, and this may help reduce muscle atrophy and fatigue when NMES is used for rehabilitation.

  • Motor Unit Recruitment when neuromuscular electrical stimulation is applied over a nerve trunk compared with a muscle belly triceps surae
    Journal of Applied Physiology, 2011
    Co-Authors: Austin J Bergquist, Joanna M Clair, David F Collins
    Abstract:

    Neuromuscular electrical stimulation (NMES) can be delivered over a nerve trunk or muscle belly and can generate contractions by activating Motor (peripheral pathway) and sensory (central pathway) ...

Yu Konishi - One of the best experts on this subject based on the ideXlab platform.

  • relationship between quadriceps femoris muscle volume and muscle torque at least 18 months after anterior cruciate ligament reconstruction
    Scandinavian Journal of Medicine & Science in Sports, 2012
    Co-Authors: Yu Konishi, Toshiaki Oda, Satoshi Tsukazaki, Ryuta Kinugasa, Toru Fukubayashi
    Abstract:

    The purpose of this study was to evaluate Motor Unit Recruitment in the quadriceps femoris (QF) after anterior cruciate ligament (ACL) rupture and repair. Subjects included 24 patients at ≥ 18 months after ACL reconstruction and 22 control subjects with no history of knee injury. A series of cross-sectional magnetic resonance images were obtained to compare the QF of patients' injured side with that of their uninjured sides and that of uninjured control subjects. Muscle torque per muscle volume was calculated as isokinetic peak torque divided by QF muscle volume (cm(3)). The mean muscle torque per Unit volume of the injured side of patients was not significantly different from that of the uninjured side or control subjects (one-way ANOVA) Results of the present study were contrary to the results of a previous study that evaluated patients at ≤ 12 months after ACL reconstruction. The present study found that high-threshold Motor Unit Recruitment was restored at ≥ 18 months after ACL reconstruction. Thus, clinicians must develop techniques that increase the Recruitment of high-threshold Motor Units in the QF from the period immediately after the injury until approximately 18 months after ACL reconstruction.

  • relationship between quadriceps femoris muscle volume and muscle torque after anterior cruciate ligament rupture
    Knee Surgery Sports Traumatology Arthroscopy, 2011
    Co-Authors: Yu Konishi, Toshiaki Oda, Satoshi Tsukazaki, Ryuta Kinugasa, Norikazu Hirose, Toru Fukubayashi
    Abstract:

    The purpose of this study was to obtain evidence to support the hypothesis that Motor Unit Recruitment is reduced in the quadriceps femoris (QF) of patients with ACL rupture. We compared muscle torque per Unit volume in the QF from injured and uninjured sides to normal subjects. If high-threshold Motor Unit Recruitment is reduced in patients with ACL rupture, this reduction will theoretically lead to a reduction in muscle torque per Unit volume compared to the control group. The subjects included 22 patients with ACL rupture and 22 subjects with no history of knee injury. To identify the muscle torque per Unit volume, the isokinetic peak torque was divided by QF volume which was obtained by MRI. Tests revealed that the mean muscle torque per Unit volume of the uninjured and injured sides was significantly lower than those of the control group. This study demonstrated that the values of the muscle torque per Unit volume of both injured and uninjured sides of patients with ACL rupture were significantly lower than those of the control group, thereby providing indirect evidence of the hindrance of Motor Unit Recruitment in these patients. The results of the present study also indicate that there may be bilateral QF weakness in patients with ACL rupture. Since persistent QF weakness is a significant barrier to effective rehabilitation in patients with ACL injuries, a better understanding of the underlying mechanisms will allow clinicians and scientists to develop more effective therapeutic strategies for patient rehabilitation.

  • relationship between quadriceps femoris muscle volume and muscle torque after anterior cruciate ligament repair
    Scandinavian Journal of Medicine & Science in Sports, 2007
    Co-Authors: Yu Konishi, K Ikeda, A Nishino, M Sunaga, Y Aihara, Toru Fukubayashi
    Abstract:

    Purpose The purpose of this study was to obtain evidence to support the hypothesis that Motor Unit Recruitment is reduced in the quadriceps femoris (QF) of patients with ACL rupture.

Austin J Bergquist - One of the best experts on this subject based on the ideXlab platform.

  • Motor Unit Recruitment when neuromuscular electrical stimulation is applied over a nerve trunk compared with a muscle belly triceps surae
    Journal of Applied Physiology, 2011
    Co-Authors: Austin J Bergquist, Joanna M Clair, David F Collins
    Abstract:

    Neuromuscular electrical stimulation (NMES) can be delivered over a nerve trunk or muscle belly and can generate contractions by activating Motor (peripheral pathway) and sensory (central pathway) axons. In the present experiments, we compared the peripheral and central contributions to plantar flexion contractions evoked by stimulation over the tibial nerve vs. the triceps surae muscles. Generating contractions through central pathways follows Henneman's size principle, whereby low-threshold Motor Units are activated first, and this may have advantages for rehabilitation. Statistical analyses were performed on data from trials in which NMES was delivered to evoke 10-30% maximum voluntary torque 2-3 s into the stimulation (Time(1)). Two patterns of stimulation were delivered: 1) 20 Hz for 8 s; and 2) 20-100-20 Hz for 3-2-3 s. Torque and soleus electromyography were quantified at the beginning (Time(1)) and end (Time(2); 6-7 s into the stimulation) of each stimulation train. H reflexes (central pathway) and M waves (peripheral pathway) were quantified. Motor Unit activity that was not time-locked to each stimulation pulse as an M wave or H reflex ("asynchronous" activity) was also quantified as a second measure of central Recruitment. Torque was not different for stimulation over the nerve or the muscle. In contrast, M waves were approximately five to six times smaller, and H reflexes were approximately two to three times larger during NMES over the nerve vs. the muscle. Asynchronous activity increased by 50% over time, regardless of the stimulation location or pattern, and was largest during NMES over the muscle belly. Compared with NMES over the triceps surae muscles, NMES over the tibial nerve produced contractions with a relatively greater central contribution, and this may help reduce muscle atrophy and fatigue when NMES is used for rehabilitation.

  • Motor Unit Recruitment when neuromuscular electrical stimulation is applied over a nerve trunk compared with a muscle belly triceps surae
    Journal of Applied Physiology, 2011
    Co-Authors: Austin J Bergquist, Joanna M Clair, David F Collins
    Abstract:

    Neuromuscular electrical stimulation (NMES) can be delivered over a nerve trunk or muscle belly and can generate contractions by activating Motor (peripheral pathway) and sensory (central pathway) ...