scholarly journals Contractile function and motor unit firing rates of the human hamstrings

2017 ◽  
Vol 117 (1) ◽  
pp. 243-250 ◽  
Author(s):  
Eric A. Kirk ◽  
Charles L. Rice
Keyword(s):  
Knee Joint ◽  
Motor Unit ◽  
Lower Limb ◽  
Biceps Femoris ◽  
Triceps Surae ◽  
Firing Rates ◽  
Lower Limb Muscles ◽  
Motor Unit Firing ◽  
Limb Muscles ◽  
Length Changes

Neuromuscular properties of the lower limb in health, aging, and disease are well described for major lower limb muscles comprising the quadriceps, triceps surae, and dorsiflexors, with the notable exception of the posterior thigh (hamstrings). The purpose of this study was to further characterize major muscles of the lower limb by comprehensively exploring contractile properties in relation to spinal motor neuron output expressed as motor unit firing rates (MUFRs) in the hamstrings of 11 (26.5 ± 3.8) young men. Maximal isometric voluntary contraction (MVC), voluntary activation, stimulated contractile properties including a force-frequency relationship, and MUFRs from submaximal to maximal voluntary contractile intensities were assessed in the hamstrings. Strength and MUFRs were assessed at two presumably different muscle lengths by varying the knee joint angles (90° and 160°). Knee flexion MVCs were 60–70% greater in the extended position (160°). The frequency required to elicit 50% of maximum tetanic torque was 16–17 Hz. Mean MUFRs at 25–50% MVC were 9–31% less in the biceps femoris compared with the semimembranosus-semitendinosus group. Knee joint angle (muscle length) influenced MUFRs such that mean MUFRs were greater in the shortened (90°) position at 50% and 100% MVC. Compared with previous reports, mean maximal MUFRs in the hamstrings are greater than those in the quadriceps and triceps surae and somewhat less than those in the tibialis anterior. Mean maximal MUFRs in the hamstrings are influenced by changes in knee joint angle, with lower firing rates in the biceps femoris compared with the semimembranosus-semitendinosus muscle group. NEW & NOTEWORTHY We studied motor unit firing rates (MUFRs) at various voluntary contraction intensities in the hamstrings, one of the only major lower limb muscles to have MUFRs affected by muscle length changes. Within the hamstrings muscle-specific differences have greater impact on MUFRs than length changes, with the biceps femoris having reduced neural drive compared with the semimembranosus-semimembranosus. Comparing our results to other lower limb muscles, flexors have inherently higher firing rate compared with extensors.

Motor unit firing frequency of lower limb muscles during an incremental slide board skating test

2017 ◽  
Vol 16 (4) ◽  
pp. 540-551 ◽  
Author(s):  
Tatiane Piucco ◽  
Rodrigo Bini ◽  
Masanori Sakaguchi ◽  
Fernando Diefenthaeler ◽  
Darren Stefanyshyn
Keyword(s):  
Motor Unit ◽  
Lower Limb ◽  
Firing Frequency ◽  
Lower Limb Muscles ◽  
Motor Unit Firing ◽  
Limb Muscles

Cortical Control of Human Motoneuron Firing During Isometric Contraction

1997 ◽  
Vol 77 (6) ◽  
pp. 3401-3405 ◽  
Author(s):  
Stephan Salenius ◽  
Karin Portin ◽  
Matti Kajola ◽  
Riitta Salmelin ◽  
Riitta Hari
Keyword(s):  
Motor Cortex ◽  
Upper Limb ◽  
Isometric Contraction ◽  
Lower Limb ◽  
Biceps Brachii ◽  
Cortical Control ◽  
Lower Limb Muscles ◽  
Cortical Rhythms ◽  
Motor Unit Firing ◽  
Limb Muscles

Salenius, Stephan, Karin Portin, Matti Kajola, Riitta Salmelin, and Riitta Hari. Cortical control of human motoneuron firing during isometric contraction. J. Neurophysiol. 77: 3401–3405, 1997. We recorded whole scalp magnetoencephalographic (MEG) signals simultaneously with the surface electromyogram from upper and lower limb muscles of six healthy right-handed adults during voluntary isometric contraction. The 15- to 33-Hz MEG signals, originating from the anterior bank of the central sulcus, i.e., the primary motor cortex, were coherent with motor unit firing in all subjects and for all muscles. The coherent cortical rhythms originated in the hand motor area for upper limb muscles (1st dorsal interosseus, extensor indicis proprius, and biceps brachii) and close to the foot area for lower limb muscles (flexor hallucis brevis). The sites of origin corresponding to different upper limb muscles did not differ significantly. The cortical signals preceded motor unit firing by 12–53 ms. The lags were shortest for the biceps brachii and increased systematically with increasing corticomuscular distance. We suggest that the motor cortex drives the spinal motoneuronal pool during sustained contractions, with the observed cortical rhythmic activity influencing the timing of efferent commands. The cortical rhythms could be related to motor binding, but the rhythmic output may also serve to optimize motor cortex output during isometric contractions.

Effect of knee joint position on triceps surae motor unit recruitment and firing rates

2019 ◽  
Vol 237 (9) ◽  
pp. 2345-2352 ◽  
Author(s):  
Kalter Hali ◽  
Eric A. Kirk ◽  
Charles L. Rice
Keyword(s):  
Knee Joint ◽  
Motor Unit ◽  
Motor Unit Recruitment ◽  
Triceps Surae ◽  
Joint Position ◽  
Firing Rates

scholarly journals Intra-limb modulations of posterior root-muscle reflexes evoked from the lower-limb muscles during isometric voluntary contractions

2021 ◽  
Author(s):  
Akira Saito ◽  
Kento Nakagawa ◽  
Yohei Masugi ◽  
Kimitaka Nakazawa
Keyword(s):  
Lower Limb ◽  
Motor Evoked Potential ◽  
Biceps Femoris ◽  
Knee Extension ◽  
Spinal Reflex ◽  
Posterior Root ◽  
Lower Limb Muscles ◽  
Limb Muscles ◽  
Voluntary Contractions ◽  
Muscle Reflexes

AbstractAlthough voluntary muscle contraction modulates spinal reflex excitability of contracted muscles and other muscles located at other segments within a limb (i.e., intra-limb modulation), to what extent corticospinal pathways are involved in intra-limb modulation of spinal reflex circuits remains unknown. The purpose of the present study was to identify differences in the involvement of corticospinal pathways in intra-limb modulation of spinal reflex circuits among lower-limb muscles during voluntary contractions. Ten young males performed isometric plantar-flexion, dorsi-flexion, knee extension, and knee flexion at 10% of each maximal torque. Electromyographic activity was recorded from soleus, tibialis anterior, vastus lateralis, and biceps femoris muscles. Motor evoked potentials and posterior root-muscle reflexes during rest and isometric contractions were elicited from the lower-limb muscles using transcranial magnetic stimulation and transcutaneous spinal cord stimulation, respectively. Motor evoked potential and posterior root-muscle reflex amplitudes of soleus during knee extension were significantly increased compared to rest. The motor evoked potential amplitude of biceps femoris during dorsi-flexion was significantly increased, whereas the posterior root-muscle reflex amplitude of biceps femoris during dorsi-flexion was significantly decreased compared to rest. These results suggest that corticospinal and spinal reflex excitabilities of soleus are facilitated during knee extension, whereas intra-limb modulation of biceps femoris during dorsi-flexion appeared to be inverse between corticospinal and spinal reflex circuits.

Effect of ankle joint position on triceps surae motor unit firing rates

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Kalter Hali ◽  
Alexander M. Zero ◽  
Jacob Fanous ◽  
Charles L. Rice
Keyword(s):  
Motor Unit ◽  
Ankle Joint ◽  
Triceps Surae ◽  
Joint Position ◽  
Firing Rates ◽  
Motor Unit Firing

scholarly journals Timing and Modulation of Activity in the Lower Limb Muscles During Indoor Rowing: What Are the Key Muscles to Target in FES-Rowing Protocols?

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1666
Author(s):  
Taian M. Vieira ◽  
Giacinto Luigi Cerone ◽  
Costanza Stocchi ◽  
Morgana Lalli ◽  
Brian Andrews ◽  
...  
Keyword(s):  
Lower Limb ◽  
Tibialis Anterior ◽  
Vastus Lateralis ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Sample Surface ◽  
Recovery Phase ◽  
Lower Limb Muscles ◽  
Limb Muscles ◽  
Stimulation Of

The transcutaneous stimulation of lower limb muscles during indoor rowing (FES Rowing) has led to a new sport and recreation and significantly increased health benefits in paraplegia. Stimulation is often delivered to quadriceps and hamstrings; this muscle selection seems based on intuition and not biomechanics and is likely suboptimal. Here, we sample surface EMGs from 20 elite rowers to assess which, when, and how muscles are activated during indoor rowing. From EMG amplitude we specifically quantified the onset of activation and silencing, the duration of activity and how similarly soleus, gastrocnemius medialis, tibialis anterior, rectus femoris, vastus lateralis and medialis, semitendinosus, and biceps femoris muscles were activated between limbs. Current results revealed that the eight muscles tested were recruited during rowing, at different instants and for different durations. Rectus and biceps femoris were respectively active for the longest and briefest periods. Tibialis anterior was the only muscle recruited within the recovery phase. No side differences in the timing of muscle activity were observed. Regression analysis further revealed similar, bilateral modulation of activity. The relevance of these results in determining which muscles to target during FES Rowing is discussed. Here, we suggest a new strategy based on the stimulation of vasti and soleus during drive and of tibialis anterior during recovery.

Frequency response of vestibular reflexes in neck, back, and lower limb muscles

2013 ◽  
Vol 110 (8) ◽  
pp. 1869-1881 ◽  
Author(s):  
Patrick A. Forbes ◽  
Christopher J. Dakin ◽  
Alistair N. Vardy ◽  
Riender Happee ◽  
Gunter P. Siegmund ◽  
...  
Keyword(s):  
Motor Unit ◽  
Lower Limb ◽  
Dynamic Range ◽  
Erector Spinae ◽  
Medial Gastrocnemius ◽  
Neck Muscle ◽  
Vestibular Reflexes ◽  
Frequency Responses ◽  
Lower Limb Muscles ◽  
Limb Muscles

Vestibular pathways form short-latency disynaptic connections with neck motoneurons, whereas they form longer-latency disynaptic and polysynaptic connections with lower limb motoneurons. We quantified frequency responses of vestibular reflexes in neck, back, and lower limb muscles to explain between-muscle differences. Two hypotheses were evaluated: 1) that muscle-specific motor-unit properties influence the bandwidth of vestibular reflexes; and 2) that frequency responses of vestibular reflexes differ between neck, back, and lower limb muscles because of neural filtering. Subjects were exposed to electrical vestibular stimuli over bandwidths of 0–25 and 0–75 Hz while recording activity in sternocleidomastoid, splenius capitis, erector spinae, soleus, and medial gastrocnemius muscles. Coherence between stimulus and muscle activity revealed markedly larger vestibular reflex bandwidths in neck muscles (0–70 Hz) than back (0–15 Hz) or lower limb muscles (0–20 Hz). In addition, vestibular reflexes in back and lower limb muscles undergo low-pass filtering compared with neck-muscle responses, which span a broader dynamic range. These results suggest that the wider bandwidth of head-neck biomechanics requires a vestibular influence on neck-muscle activation across a larger dynamic range than lower limb muscles. A computational model of vestibular afferents and a motoneuron pool indicates that motor-unit properties are not primary contributors to the bandwidth filtering of vestibular reflexes in different muscles. Instead, our experimental findings suggest that pathway-dependent neural filtering, not captured in our model, contributes to these muscle-specific responses. Furthermore, gain-phase discontinuities in the neck-muscle vestibular reflexes provide evidence of destructive interaction between different reflex components, likely via indirect vestibular-motor pathways.

Sign in / Sign up

Export Citation Format

Share Document