Failed Excitability of Spinal Motoneurons Induced by Prolonged Running Exercise

2007 ◽  
Vol 97 (1) ◽  
pp. 596-603 ◽  
Author(s):  
S. Racinais ◽  
O. Girard ◽  
J. P. Micallef ◽  
S. Perrey
Keyword(s):  
Maximal Voluntary Contraction ◽  
Ventilatory Threshold ◽  
Central Fatigue ◽  
Voluntary Contraction ◽  
H Reflex ◽  
Spinal Motoneurons ◽  
Plantar Flexors ◽  
M Wave ◽  
V Wave ◽  
First Time

The main purpose of this study was to investigate the modulations in H-reflex and V-wave responses (spinal loop properties) induced by prolonged locomotion activities. The second purpose was to compare the development of central fatigue between continuous and intermittent running modes. Eleven males randomly performed two 90-min running exercises either continuously (CONT, first ventilatory threshold) or intermittently (INT, 150 s at a velocity 20% higher than that during CONT/30 s of recovery). Neuromuscular tests of the plantar flexors [including M-wave and H-reflex at rest and M-wave and V-wave during maximal voluntary contraction (MVC)] were performed before and 5 and 30 min after the running exercises. During MVC, the torque significantly decreased ( P < 0.05) from preexercise to 5 and 30 min postexercise (−11 and −9%, respectively), as did the RMS/M ratio (−11 and −13%, respectively) and the V/M ratio (−19 and −37%, respectively) for the soleus muscle. At rest, the H/M ratio also decreased significantly ( P < 0.001) from preexercise to 5 and 30 min postexercise (−61 and −55%, respectively). Last, no difference in the alteration of spinal loop properties was noted between CONT and INT. In conclusion, the results regarding H-reflex and V-wave suggest for the first time a modulation in spinal loop properties after prolonged running.

scholarly journals Changes in H reflex and V wave following short-term endurance and strength training

2012 ◽  
Vol 112 (1) ◽  
pp. 54-63 ◽  
Author(s):  
Carolina Vila-Chã ◽  
Deborah Falla ◽  
Miguel Velhote Correia ◽  
Dario Farina
Keyword(s):  
Strength Training ◽  
Endurance Training ◽  
Voluntary Contraction ◽  
H Reflex ◽  
Plantar Flexors ◽  
M Wave ◽  
Task Failure ◽  
Strength Group ◽  
Reflex Excitability ◽  
V Wave

This study examined the effects of 3 wk of either endurance or strength training on plasticity of the neural mechanisms involved in the soleus H reflex and V wave. Twenty-five sedentary healthy subjects were randomized into an endurance group ( n = 13) or strength group ( n = 12). Evoked V-wave, H-reflex, and M-wave recruitment curves, maximal voluntary contraction (MVC), and time-to-task-failure (isometric contraction at 40% MVC) of the plantar flexors were recorded before and after training. Following strength training, MVC of the plantar flexors increased by 14.4 ± 5.2% in the strength group ( P < 0.001), whereas time-to-task-failure was prolonged in the endurance group (22.7 ± 17.1%; P < 0.05). The V wave-to-maximal M wave (V/Mmax) ratio increased significantly (55.1 ± 28.3%; P < 0.001) following strength training, but the maximal H wave-to-maximal M wave (Hmax/Mmax) ratio remained unchanged. Conversely, in the endurance group the V/Mmax ratio was not altered, whereas the Hmax/Mmax ratio increased by 30.8 ± 21.7% ( P < 0.05). The endurance training group also displayed a reduction in the H-reflex excitability threshold while the H-reflex amplitude on the ascending limb of the recruitment curve increased. Strength training only elicited a significant decrease in H-reflex excitability threshold, while H-reflex amplitudes over the ascending limb remained unchanged. These observations indicate that the H-reflex pathway is strongly involved in the enhanced endurance resistance that occurs following endurance training. On the contrary, the improvements in MVC following strength training are likely attributed to increased descending drive and/or modulation in afferents other than Ia afferents.

scholarly journals Short-term resistance training with instability reduces impairment in V wave and H reflex in individuals with Parkinson’s disease

2019 ◽  
Vol 127 (1) ◽  
pp. 89-97 ◽  
Author(s):  
Carla Silva-Batista ◽  
Jumes Leopoldino de Oliveira Lira ◽  
Fabian J. David ◽  
Daniel M. Corcos ◽  
Eugenia Casella Tavares Mattos ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Resistance Training ◽  
Wave Amplitude ◽  
H Reflex ◽  
Plantar Flexors ◽  
Short Term ◽  
M Wave ◽  
Reflex Responses ◽  
V Wave

This study had two objectives: 1) to compare the effects of 3 wk of resistance training (RT) and resistance training with instability (RTI) on evoked reflex responses at rest and during maximal voluntary isometric contraction (MVIC) of individuals with Parkinson’s disease (PD) and 2) to determine the effectiveness of RT and RTI in moving values of evoked reflex responses of individuals with PD toward values of age-matched healthy control subjects (HCs) ( z-score analysis). Ten individuals in the RT group and 10 in the RTI group performed resistance exercises twice a week for 3 wk, but only the RTI group included unstable devices. The HC group ( n = 10) were assessed at pretest only. Evoked reflex responses at rest (H reflex and M wave) and during MVIC [supramaximal M-wave amplitude (Msup) and supramaximal V-wave amplitude (Vsup)] of the plantar flexors were assessed before and after the experimental protocol. From pretraining to posttraining, only RTI increased ratio of maximal H-reflex amplitude to maximal M-wave amplitude at rest (Hmax/Mmax), Msup, Vsup/Msup, and peak torque of the plantar flexors ( P < 0.05). At posttraining, RTI was more effective than RT in increasing resting Hmax and Vsup and in moving these values to those observed in HCs ( P < 0.05). We conclude that short-term RTI is more effective than short-term RT in modulating H-reflex excitability and in increasing efferent neural drive, approaching average values of HCs. Thus short-term RTI may cause positive changes at the spinal and supraspinal levels in individuals with PD. NEW & NOTEWORTHY Maximal H-reflex amplitude (Hmax) at rest and efferent neural drive [i.e., supramaximal V-wave amplitude (Vsup)] to skeletal muscles during maximal contraction are impaired in individuals with Parkinson’s disease. Short-term resistance training with instability was more effective than short-term resistance training alone in increasing Hmax and Vsup of individuals with Parkinson’s disease, reaching the average values of healthy control subjects.

Evoked H-Reflex and V-Wave Responses During Maximal Isometric, Concentric, and Eccentric Muscle Contraction

2005 ◽  
Vol 94 (5) ◽  
pp. 3555-3562 ◽  
Author(s):  
Julien Duclay ◽  
Alain Martin
Keyword(s):  
Plantar Flexion ◽  
Muscle Length ◽  
Eccentric Contraction ◽  
H Reflex ◽  
Plantar Flexors ◽  
M Wave ◽  
Eccentric Muscle Contraction ◽  
Action Type ◽  
V Wave ◽  
Postactivation Depression

This study was designed to investigate the modulations of H-reflex and V-wave responses during passive and maximal active dynamic actions. Experiments were performed on 16 healthy males [age: 24 ± 4 (SD) yr]. Maximal H-reflexes ( Hmax) and M-waves ( MmaxR) were evoked at the same muscle length during passive isometric, shortening and lengthening actions and during maximal voluntary isometric, concentric, and eccentric plantar-flexion. In all contraction types, supra-maximal stimulus intensity was used to evoke the superimposed maximal M wave ( MmaxA) and V wave ( V) of the soleus muscle. At rest, the Hmax/ MmaxR ratio was significantly reduced during lengthening with respect to isometric and shortening actions ( P < 0.05). For each action type, the ratio between H reflex superimposed to the contraction ( Hsup) and MmaxA was not different from Hmax/ MmaxR ratio. When plantar flexors were maximally voluntary activated, the Hsup/ MmaxA ratio was still lower during eccentric contraction as compared with isometric and concentric efforts (0.33 ± 0.03 vs. 0.47 ± 0.02 and 0.50 ± 0.03, P < 0.001), whereas V/ MmaxA ratios were similar for all contraction types (isometric 0.26 ± 0.02; concentric 0.23 ± 0.03, and eccentric 0.24 ± 0.02; P > 0.05). The V/ MmaxA ratio was significantly lower than Hsup/ MmaxA during isometric and concentric MVC ( P < 0.001). No difference was observed between V/ MmaxA and Hsup/ MmaxA ratios during eccentric efforts. The H-reflex modulations, present during lengthening actions, were mainly attributed to presynaptic inhibition of Ia afferents and to homosynaptic postactivation depression. Results on V wave and H reflex suggest that during eccentric MVC, the spinal loop is specifically modulated by the supra-spinal centers and/or neural mechanisms at spinal level.

scholarly journals Exercise tolerance during muscle contractions below and above the critical torque in different muscle groups

2018 ◽  
Vol 43 (2) ◽  
pp. 174-179 ◽  
Author(s):  
Leonardo Henrique Perinotto Abdalla ◽  
Benedito Sérgio Denadai ◽  
Natália Menezes Bassan ◽  
Camila Coelho Greco
Keyword(s):  
Exercise Intensity ◽  
Maximal Voluntary Contraction ◽  
Exercise Tolerance ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Isometric Contractions ◽  
Plantar Flexors ◽  
Significant Difference ◽  
Muscle Groups

The objective of this study was to test the hypotheses that end-test torque (ET) (expressed as % maximal voluntary contraction; MVC) is higher for plantar flexors (PF) than knee extensors (KE) muscles, whereas impulse above ET (IET) is higher for KE than PF. Thus, we expected that exercise tolerance would be longer for KE than PF only during the exercise performed above ET. After the determination of MVC, 40 men performed two 5-min all-out tests to determine ET and IET. Eleven participants performed a further 4 intermittent isometric tests, to exhaustion, at ET + 5% and ET – 5%, and 1 test for KE at the exercise intensity (%MVC) corresponding to ET + 5% of PF. The IET (7243.2 ± 1942.9 vs. 3357.4 ± 1132.3 N·m·s) and ET (84.4 ± 24.8 vs. 73.9 ± 19.5 N·m) were significantly lower in PF compared with KE. The exercise tolerance was significantly longer for PF (300.7 ± 156.7 s) than KE (156.7 ± 104.3 s) at similar %MVC (∼60%), and significantly shorter for PF (300.7 ± 156.7 s) than KE (697.0 ± 243.7 s) at ET + 5% condition. However, no significant difference was observed for ET – 5% condition (KE = 1030.2 ± 495.4 s vs. PF = 1028.3 ± 514.4 s). Thus, the limit of tolerance during submaximal isometric contractions is influenced by absolute MVC only during exercise performed above ET, which seems to be explained by differences on both ET (expressed as %MVC) and IET values.

Fatigue of intermittent submaximal voluntary contractions: central and peripheral factors

1986 ◽  
Vol 61 (2) ◽  
pp. 421-429 ◽  
Author(s):  
B. Bigland-Ritchie ◽  
F. Furbush ◽  
J. J. Woods
Keyword(s):  
No Reduction ◽  
Rest Period ◽  
Central Fatigue ◽  
Voluntary Contraction ◽  
Adductor Pollicis ◽  
M Wave ◽  
Generating Capacity ◽  
Target Force ◽  
Voluntary Contractions ◽  
Muscle Contractile

Central and peripheral factors were studied in fatigue of submaximal intermittent isometric contractions of the human quadriceps and soleus muscles. Subjects made repeated 6 s, 50% maximal voluntary contractions (MVC) followed by 4 s rest until the limit of endurance (Tlim). Periodically, a fatigue test was performed. This included a brief MVC, either a single shock or 8 pulses at 50 Hz during a rest period and a shock superimposed on a target force voluntary contraction. At Tlim, the MVC force had declined by 50%, usually in parallel with the force from stimulation at 50 Hz. The twitches superimposed on the target forces declined more rapidly, disappearing entirely at Tlim. In similar experiments on adductor pollicis, no reduction of the evoked M wave was seen. The results suggest that, during fatigue of quadriceps and adductor pollicis induced by this protocol, no central fatigue was apparent, but some was seen in soleus. Thus the reduced force-generating capacity could result mainly or entirely from failure of the muscle contractile apparatus.

Central and peripheral contributions to fatigue in relation to level of activation during repeated maximal voluntary isometric plantar flexions

2004 ◽  
Vol 96 (1) ◽  
pp. 218-225 ◽  
Author(s):  
Maria M. Nordlund ◽  
Alf Thorstensson ◽  
Andrew G. Cresswell
Keyword(s):  
Presynaptic Inhibition ◽  
Central Fatigue ◽  
H Reflex ◽  
Joint Torque ◽  
Medial Gastrocnemius ◽  
Voluntary Activation ◽  
Peripheral Fatigue ◽  
M Wave ◽  
Postactivation Depression ◽  
Electromyographic Signals

This study aimed to investigate central and peripheral contributions to fatigue during repeated maximal voluntary isometric plantar flexions (MVCs). Changes in joint torque, level of activation (LOA), resting twitch amplitude (RT), electromyographic signals (EMG), and presynaptic inhibition of Ia afferents were investigated during 9 bouts of 10 MVCs. MVCs lasted for 2 s and were separated by 1 s. The interval between bouts was 10 s. Electrical stimulation was applied to the tibial nerve; at rest to evoke RTs, M waves, and two (1.5-s interval) H reflexes; with the soleus EMG at 30% of that during MVC to evoke M waves and two H reflexes; and during MVCs to measure LOA. Over the nine bouts, LOA decreased by 12.6% and RT by 16.2%. EMG root mean square during MVCs remained unchanged for the soleus and tibialis anterior muscles, but it decreased for medial gastrocnemius. Peripheral fatigue (decrease in RT) was positively correlated to LOA, whereas central fatigue (decrease in LOA) was not. Depression of both H reflexes suggests that presynaptic inhibition after the first bout was partly induced by homosynaptic postactivation depression of the Ia terminal. The H-reflex-to-M-wave ratio increased with fatigue in both passive and active states, with no change in the ratio of the second H reflex to the first, thereby indicating a decrease of presynaptic inhibition during fatigue. The results indicate that both central and peripheral mechanisms contributed to the fatigue observed during repeated MVCs and that the development of peripheral fatigue was influenced by the level of voluntary activation and initial plantar flexor torque.

scholarly journals Lifelong strength training mitigates the age-related decline in efferent drive

2016 ◽  
Vol 121 (2) ◽  
pp. 415-423 ◽  
Author(s):  
Runar Unhjem ◽  
Mona Nygård ◽  
Lene T. van den Hoven ◽  
Simranjit K. Sidhu ◽  
Jan Hoff ◽  
...  
Keyword(s):  
Strength Training ◽  
Plantar Flexion ◽  
H Reflex ◽  
Voluntary Activation ◽  
M Wave ◽  
Reflex Amplitude ◽  
Age Related ◽  
Musculus Soleus ◽  
V Wave ◽  
Voluntary Contractions

Recently, we documented age-related attenuation of efferent drive to contracting skeletal muscle. It remains elusive if this indication of reduced muscle strength is present with lifelong strength training. For this purpose, we examined evoked potentials in the calf muscles of 11 [71 ± 4 (SD) yr] strength-trained master athletes (MA) contrasted with 10 (71 ± 4 yr) sedentary (SO) and 11 (73 ± 6 yr) recreationally active (AO) old subjects, as well as 9 (22 ± 2 yr) young controls. As expected, MA had higher leg press maximal strength (MA, 185 ± 32 kg; AO, 128 ± 15 kg; SO, 106 ± 11 kg; young, 147 ± 22 kg, P < 0.01) and rate of force development (MA, 5,588 ± 2,488 N/s; AO, 2,156 ± 1,100 N/s; SO, 2,011 ± 825 N/s; young, 3,663 ± 1,140 N/s, P < 0.05) than the other groups. MA also exhibited higher musculus soleus normalized V waves during maximal voluntary contractions (MVC) [maximal V wave amplitude/maximal M wave during MVC (Vsup/Msup); 0.28 ± 0.15] than AO (0.13 ± 0.06, P < 0.01) and SO (0.11 ± 0.05, P < 0.01), yet lower than young (0.45 ± 0.12, P < 0.01). No differences were apparent between the old groups in H reflex recorded at rest or during MVC [maximal H reflex amplitude/maximal M wave during rest (Hmax/Mmax); maximal H reflex amplitude during MVC/maximal M wave during MVC (Hsup/Msup)], and all were lower ( P < 0.01) than young. MA (34.4 ± 2.1 ms) had shorter ( P < 0.05) H reflex latency compared with AO (36.4 ± 3.7 ms) and SO (37.3 ± 3.2 ms), but longer ( P < 0.01) than young (30.7 ± 2.0 ms). Using interpolated twitch analysis, MA (89 ± 7%) had plantar flexion voluntary activation similar to young (90 ± 6%), and this was higher ( P < 0.05), or tended to be higher ( P = 0.06–0.09), than SO (83 ± 10%) and AO (84 ± 5%). These observations suggest that lifelong strength training has a protective effect against age-related attenuation of efferent drive. In contrast, no beneficial effect seems to derive from habitual recreational activity, indicating that strength training may be particularly beneficial for counteracting age-related loss of neuromuscular function.

Human neuromuscular fatigue is associated with altered Na+-K+-ATPase activity following isometric exercise

2002 ◽  
Vol 92 (4) ◽  
pp. 1585-1593 ◽  
Author(s):  
J. R. Fowles ◽  
H. J. Green ◽  
R. Tupling ◽  
S. O'Brien ◽  
B. D. Roy
Keyword(s):  
Atpase Activity ◽  
Maximal Voluntary Contraction ◽  
Vastus Lateralis ◽  
Isometric Exercise ◽  
Voluntary Contraction ◽  
Neuromuscular Fatigue ◽  
Vastus Lateralis Muscle ◽  
M Wave ◽  
Leg Extension ◽  
Muscle Action Potential

The purpose of this study was to investigate the hypothesis that reductions in Na+-K+- ATPase activity are associated with neuromuscular fatigue following isometric exercise. In control (Con) and exercised (Ex) legs, force and electromyogram were measured in 14 volunteers [age, 23.4 ± 0.7 (SE) yr] before and immediately after (PST0), 1 h after (PST1), and 4 h after (PST4) isometric, single-leg extension exercise at ∼60% of maximal voluntary contraction for 30 min using a 0.5 duty cycle (5-s contraction, 5-s rest). Tissue was obtained from vastus lateralis muscle before exercise in Con and after exercise in both the Con (PST0) and Ex legs (PST0, PST1, PST4), for the measurements of Na+-K+-ATPase activity, as determined by the 3- O-methylfluorescein phosphatase (3- O-MFPase) assay. Voluntary (maximal voluntary contraction) and elicited (10, 20, 50, 100 Hz) force was reduced 30–55% ( P < 0.05) at PST0 and did not recover by PST4. Muscle action potential (M-wave) amplitude and area (measured in the vastus medialis) and 3- O-MFPase activity at PST0-Ex were less than that at PST0-Con ( P < 0.05) by 37, 25, and 38%, respectively. M-wave area at PST1-Ex was also less than that at PST1-Con ( P < 0.05). Changes in 3- O-MFPase activity correlated to changes in M-wave area across all time points ( r = 0.38, P < 0.05, n= 45). These results demonstrate that Na+-K+- ATPase activity is reduced by sustained isometric exercise in humans from that in a matched Con leg and that this reduction in Na+-K+-ATPase activity is associated with loss of excitability as indicated by M-wave alterations.

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