Counterpoint: Spectral properties of the surface emg do not provide information about motor unit recruitment and muscle fiber type

Farina, Dario

doi:10.1152/japplphysiol.90598.2008a

Cited by 62 publications

(55 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus the efficiency of limb movement was related to the timevarying frequency spectra of the EMG intensities. The frequency components of the EMG intensity spectra can be related to the type of motor units recruited (von Tscharner 2000;Wakeling 2009;Wakeling and Horn 2009;Wakeling and Rozitis 2004), although this has been controversial (Farina 2008;von Tscharner and Nigg 2008). The shifts in EMG frequency may result from the activation-deactivation limitations at the highest cadences, mentioned above (Fig.…”

Section: Discussionmentioning

confidence: 99%

Muscle coordination limits efficiency and power output of human limb movement under a wide range of mechanical demands

Blake

Wakeling

2015

Journal of Neurophysiology

View full text Add to dashboard Cite

Blake OM, Wakeling JM. Muscle coordination limits efficiency and power output of human limb movement under a wide range of mechanical demands. J Neurophysiol 114: 3283-3295, 2015. First published October 7, 2015 doi:10.1152/jn.00765.2015.-This study investigated the influence of cycle frequency and workload on muscle coordination and the ensuing relationship with mechanical efficiency and power output of human limb movement. Eleven trained cyclists completed an array of cycle frequency (cadence)-power output conditions while excitation from 10 leg muscles and power output were recorded. Mechanical efficiency was maximized at increasing cadences for increasing power outputs and corresponded to muscle coordination and muscle fiber type recruitment that minimized both the total muscle excitation across all muscles and the ineffective pedal forces. Also, maximum efficiency was characterized by muscle coordination at the top and bottom of the pedal cycle and progressive excitation through the uniarticulate knee, hip, and ankle muscles. Inefficiencies were characterized by excessive excitation of biarticulate muscles and larger duty cycles. Power output and efficiency were limited by the duration of muscle excitation beyond a critical cadence (120 -140 rpm), with larger duty cycles and disproportionate increases in muscle excitation suggesting deteriorating muscle coordination and limitations of the activation-deactivation capabilities. Most muscles displayed systematic phase shifts of the muscle excitation relative to the pedal cycle that were dependent on cadence and, to a lesser extent, power output. Phase shifts were different for each muscle, thereby altering their mechanical contribution to the pedaling action. This study shows that muscle coordination is a key determinant of mechanical efficiency and power output of limb movement across a wide range of mechanical demands and that the excitation and coordination of the muscles is limited at very high cycle frequencies. electromyography; excitation; power output; cadence; cycling; motor control HUMAN LIMB MOVEMENT IS ACHIEVED through interactions between the neuromuscular and skeletal systems. Movement performance is commonly measured by the resultant mechanical efficiency (ratio of mechanical power output to metabolic power) and power output, both of which are significantly influenced by the coordinated excitation of individual muscles and the coordination of that excitation between muscles Dorel et al. 2012;Samozino et al. 2007;Wakeling et al. 2010). Therefore, investigating movement performance requires a comprehensive understanding of how the individual muscle excitations and the coordination between muscles (muscle coordination) change in response to the demands.Mechanical demands such as workload and movement velocity can be uncoupled during cycling (Wakeling et al. 2006;Wakeling and Horn 2009), making it an appropriate model to investigate the effects of mechanical demands on individual muscle excitation and muscle coordination and the resultant performan...

show abstract

Section: Discussionmentioning

confidence: 99%

Muscle coordination limits efficiency and power output of human limb movement under a wide range of mechanical demands

Blake

Wakeling

2015

Journal of Neurophysiology

View full text Add to dashboard Cite

show abstract

“…The distinction of muscle fibre type from the spectral properties of the EMG signal has been controversial (Farina, 2008;von Tscharner and Nigg, 2008) and poses a limitation to the interpretation of the frequency changes. However, progressive developments in EMG decomposition have made it possible to distinguish faster and slower muscle fibres based on the signal frequency with fast and slow muscle fibres producing high and low EMG frequencies, respectively (Gerdle et al, 1988;Solomonow et al, 1990;Elert et al, 1992;Kupa et al, 1995;von Tscharner, 2000;Wakeling and Rozitis, 2004;Wakeling, 2009;Wakeling and Horn, 2009).…”

Section: Discussionmentioning

confidence: 99%

Early deactivation of slower muscle fibres at high movement frequencies

Blake

Wakeling

2014

Journal of Experimental Biology

View full text Add to dashboard Cite

Animals produce rapid movements using fast cyclical muscle contractions. These types of movements are better suited to faster muscle fibres within muscles of mixed fibre types as they can shorten at faster velocities and achieve higher activation-deactivation rates than their slower counterparts. Preferential recruitment of faster muscle fibres has previously been shown during high velocity contractions. Additionally, muscle deactivation takes longer than activation and therefore may pose a limitation to fast cyclical contractions. It has been speculated that slower fibres may be deactivated before faster fibres to accommodate their longer deactivation time. This study aimed to test whether shifts in muscle fibre recruitment occur with derecruitment of slow fibres before faster fibres at high cycle frequencies. Electromyographic (EMG) signals were collected from the medial gastrocnemius at an extreme range of cycle frequencies and workloads. Wavelets were used to resolve the EMG signals into time and frequency space and the primary sources of variability within the EMG frequency spectra were identified through principal component analysis. Early derecruitment of slower fibres was evident at the end of muscle excitation at higher cycle frequencies, as determined by reduced low-frequency EMG content, and additional slower fibre recruitment was present at the highest cycle frequency. The duration of muscle excitation reached a minimum of about 150 ms and did not change for the three highest cycle frequencies, suggesting a duration limit for the medial gastrocnemius. This study provides further evidence of modifications of muscle fibre recruitment strategies to meet the mechanical demands of movement.

show abstract

“…Lateva, 1988) because we used implanted intramuscular electrodes with inter-electrode distances of ~3-4mm. The association between the low-and high-frequency myoelectric signal contents and activation of slower and faster motor units has recently been challenged for myoelectric signals recorded using surface electrodes in humans (Farina, 2008a;Farina, 2008b) (but see Wakeling, 2009). However, as discussed above, most of the arguments do not apply to myoelectric signals recorded using intramuscular electrodes in an animal model.…”

Section: Wavelet and Principal Components Analysis Of Intramuscular Mmentioning

confidence: 99%

Task dependent activity of motor unit populations in feline ankle extensor muscles

Hodson-Tole

Pantall

Maas

et al. 2012

Journal of Experimental Biology

View full text Add to dashboard Cite

SUMMARYUnderstanding the functional significance of the morphological diversity of mammalian skeletal muscles is limited by technical difficulties of estimating the contribution of motor units with different properties to unconstrained motor behaviours. Recently developed wavelet and principal components analysis of intramuscular myoelectric signals has linked signals with lower and higher frequency contents to the use of slower and faster motor unit populations. In this study we estimated the relative contributions of lower and higher frequency signals of cat ankle extensors (soleus, medial and lateral gastrocnemii, plantaris) during level, downslope and upslope walking and the paw-shake response. This was done using the first two myoelectric signal principal components (PCI, PCII), explaining over 90% of the signal, and an angle , a function of PCI/PCII, indicating the relative contribution of slower and faster motor unit populations. Mean myoelectric frequencies in all walking conditions were lowest for slow soleus (234Hz) and highest for fast gastrocnemii (307 and 330Hz) muscles. Motor unit populations within and across the studied muscles that demonstrated lower myoelectric frequency (suggesting slower populations) were recruited during tasks and movement phases with lower mechanical demands on the ankle extensors -during downslope and level walking and in early walking stance and paw-shake phases. With increasing mechanical demands (upslope walking, mid-phase of paw-shake cycles), motor unit populations generating higher frequency signals (suggesting faster populations) contributed progressively more. We conclude that the myoelectric frequency contents within and between feline ankle extensors vary across studied motor behaviours, with patterns that are generally consistent with muscle fibre-type composition.

show abstract

Counterpoint: Spectral properties of the surface emg do not provide information about motor unit recruitment and muscle fiber type

Cited by 62 publications

References 26 publications

Muscle coordination limits efficiency and power output of human limb movement under a wide range of mechanical demands

Muscle coordination limits efficiency and power output of human limb movement under a wide range of mechanical demands

Early deactivation of slower muscle fibres at high movement frequencies

Task dependent activity of motor unit populations in feline ankle extensor muscles

Contact Info

Product

Resources

About