Summary
The EMG response and the mechanical response to 2 degree stretch of the human anterior tibial muscle was studied during contractions ranging from 0% to 80% of maximal voluntary contraction (MVC). The EMG response showed three distinct peaks M1, M2, and M3 with peak latencies of 59 ms, 86 ms, and 120 ms respectively. At low background torques M1 dominated while M2 and M3 were small or absent. M2 and M3 dominated above 40% of MVC and M2 in particular showed “automatic gain compensation”, i.e. it constituted a — more or less — constant proportion of the background EMG for all contraction levels. The ratio between M1 amplitude and background EMG steadily decreased with contraction level. Even though the summed contributions of M1, M2, and M3 to some degree showed automatic gain compensation, this was not the case for the mechanical response to stretch. Between 0% and 30% of MVC the reflex mediated mechanical response increased approximately in proportion to the contraction level, but the reflex mediated mechanical response peaked at 40% of MVC and declined to zero at 80% of MVC. This discrepancy between EMG and mechanical response was explained by a simple model. The regression line between rectified and filtered tibialis anterior EMG and torque was used to predict the mechanical response from the EMG response. At increasing contraction levels the twitch elicited by supramaximal electrical stimulation decreases, and we reduced the predicted mechanical response by the same factor as the twitch. This simple model predicted the mechanical response for all contraction levels, making it possible to assess the “functionality” of reflexes even when accurate measurements of muscle force or intrinsic muscle properties are not possible.
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References
Allum JHJ, Mauritz K-H (1984) Compensation for intrinsic muscle stiffness by short-latency reflexes in human triceps surae muscles. J Neurophysiol 52: 797–818
Bedingham W, Tatton WG (1984) Dependence of EMG responses evoked by imposed wrist displacements on preexisting activity in the stretched muscles. Can J Neurol Sci 11: 272–280
Berardelli A, Hallett M, Kaufman C, Fine E, Berenberg W, Simon SR (1982) Stretch reflexes of triceps surae in normal man. J Neurol Neurosurg Psychiatr 45: 513–525
Crago PE, Houk JC, Hasan Z (1976) Regulatory actions of human stretch reflex. J Neurophysiol 39: 925–935
Hagbarth KE, Hägglund JV, Wallin EU, Young RR (1981) Grouped spindle and electromyographic responses to abrupt wrist extension movements in man. J Physiol (Lond) 312: 81–96
Henneman E, Clamann HP, Gillies JD, Skinner RD (1974) Rank order of motoneurons within a pool: law of combination. J Neurophysiol 37: 1338–1349
Hoffer JA, Andreassen S (1981) Regulation of soleus muscle stiffness in premammillary cats: intrinsic and reflex components. J Neurophysiol 45: 267–285
Houk JC, Singer W, Goldman MR (1970) An evaluation of length and force feedback to soleus muscle of decerebrate cats. J Neurophysiol 33: 784–811
Hultborn H, Wigström H (1980) Motor response with long-latency and maintained duration evoked by activity in Ia afferents. Prog Clin Neurophysiol 8: 99–116
Hunter IW, Kearney RE (1982) Dynamics of human ankle stiffness: variation with mean ankle torque. J Biomech 15: 747–752
Joyce GC, Rack PMH, Westbury DR (1969) The mechanical properties of cat soleus muscle during controlled lengthening and shortening movements. J Physiol (Lond) 204: 461–474
Lee RG, Tatton WG (1975) Motor responses to sudden limb displacements in primates with specific CNS lesions and in human patients with motor system disorders. Can J Neurol Sci 2: 285–293
Marsden CD, Merton PA, Morton HB (1973) Is the human stretch reflex cortical rather than spinal? Lancet I: 759–761
Marsden CD, Merton PA, Morton HB (1976) Servo action in the human thumb. J Physiol (Lond) 257: 1–44
Marsden CD, Rothwell JC, Day BL (1983) Long-latency automatic responses to muscle stretch in man: origin and function. Adv Neurol 39: 509–539
Matthews PBC (1986) Observations on the automatic compensation of reflex gain on varying the preexisting level of motor discharge in man. J Physiol (Lond) 374: 73–90
Matthews PBC (1987) Effect of arm cooling on long-latency reflex responses from the human first dorsal interosseous muscle — evidence for a group I contribution. J Physiol (Lond) 394: 102P
Melvill Jones G, Watt DGD (1971) Observations on the control of stepping and hopping movements in man. J Physiol (Lond) 219: 709–727
Nichols TR, Houk JC (1976) Improvement in linearity and regulation of stiffness that results from actions of stretch reflex. J Neurophysiol 39: 119–142
Rack PMH, Westbury DR (1969) The effects of length and stimulus rate on tension in the isometric cat soleus muscle. J Physiol (Lond) 204: 443–460
Rack PMH, Westbury DR (1974) The short range stiffness of active mammalian muscle and its effect on mechanical properties. J Physiol (Lond) 240: 331–350
Sinkjær T (1988) A quantitative analysis of muscle stiffness: intrinsic and reflex mediated components. Ph.D. thesis, Department of Medical Informatics and Image Analysis, Aalborg University, Denmark
Sinkjær T, Hoffer JA (1987) Blocking the antagonist nerve reduces the amplitude of the short-latency stretch reflex response in triceps surae muscles of cats. Soc Neurosci Abstr 13: 717
Sinkjær T, Toft E, Andreassen S, Hornemann BC (1988) Muscle stiffness in human ankle dorsiflexors: intrinsic and reflex components. J Neurophysiol 60
Woods JJ, Furbush F, Bigland-Ritchie B (1987) Evidence for a fatigue-induced reflex inhibition of motoneuron firing rates. J Neurophysiol 58: 125–137
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Toft, E., Sinkjær, T. & Andreassen, S. Mechanical and electromyographic responses to stretch of the human anterior tibial muscle at different levels of contraction. Exp Brain Res 74, 213–219 (1989). https://doi.org/10.1007/BF00248294
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DOI: https://doi.org/10.1007/BF00248294