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.

Increased spinal reflex excitability is not associated with neural plasticity underlying the cross-education effect

2006 ◽  
Vol 100 (1) ◽  
pp. 83-90 ◽  
Author(s):  
Olle Lagerquist ◽  
E. Paul Zehr ◽  
David Docherty
Keyword(s):  
Strength Training ◽  
Plantar Flexion ◽  
Exercise Group ◽  
H Reflex ◽  
Spinal Reflex ◽  
Control Group ◽  
M Wave ◽  
Education Effect ◽  
Cross Education ◽  
The Cross

The purpose of this study was to examine the effects of a 5-wk unilateral, isometric strength-training program on plasticity in the spinal Hoffmann (H-) reflex in both the trained and untrained legs. Sixteen participants, 22–42 yr old, were assigned to either a control ( n = 6) or an exercise group ( n = 10). Both groups were tested for plantar flexion maximal voluntary isometric contractions (MVIC) and soleus H-reflex amplitude in both limbs, at the beginning and at the end of a 5-wk interval. Participants in the exercise group showed significantly increased MVIC in both legs after training ( P < 0.05), whereas strength was unchanged in the control group for either leg. Subjects in the exercise group displayed increased ( P < 0.05) H-reflex amplitudes on the ascending limb of the recruitment curve (at an equivalent M wave of 5% of the maximal M wave, HA) only in the trained leg. Maximal H-reflex and M-wave remained unchanged with training. Increased amplitude of HA in the trained limb concurrent with increased strength suggests that spinal mechanisms may underlie the changes in strength, possibly because of increased α-motoneuronal excitability or reduced presynaptic inhibition. Despite a similar increase in strength in the contralateral limb of the exercise group, HA amplitude was unchanged. We conclude that the cross-education effect of strength training may be due to supraspinal to a greater extent than spinal mechanisms.

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.

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 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.

External Resistance Is Imperative for Training-Induced Efferent Neural Drive Enhancement in Older Adults

2020 ◽  
Author(s):  
Runar Unhjem ◽  
Tiril Tøien ◽  
Ann Charlotte Gjertsen Kvellestad ◽  
Thomas Storehaug Øren ◽  
Eivind Wang
Keyword(s):  
Older Adults ◽  
Strength Training ◽  
Plantar Flexion ◽  
Skill Learning ◽  
External Loading ◽  
Control Group ◽  
External Resistance ◽  
Neural Drive ◽  
Age Related ◽  
Heavy Loads

Abstract Strength training performed with heavy loads and maximal intended velocity is documented to enhance efferent neural drive to maximally contracting musculature in older adults. However, it remains unclear whether the neural plasticity following training result from motor skill learning or if external resistance is a prerequisite. To investigate this, we assessed electrically evoked potentials (H-reflex and V-waves normalized to maximal M-wave) and voluntary activation (VA) in 36 older adults (73 ± 4 years) randomized to 3 weeks of plantar flexion strength training, with (maximal strength training [MST]) or without (unloaded ballistic training [UBT]) heavy external loading (90% of one repetition maximum), or a control group. Both training groups aimed to execute the concentric phase of movement as fast and forcefully as possible. The MST group improved maximal voluntary contraction (MVC) and rate of force development (RFD) by 18% ± 13% (p = .001; Hedges g = 0.66) and 35% ± 17% (p &lt; .001; g = 0.94), respectively, and this was different (MVC: p = .013; RFD: p = .001) from the UBT group which exhibited a 7% ± 8% (p = .033; g = 0.32) increase in MVC and a tendency to increase RFD (p = .119; g = 0.22). Concomitant improvements in efferent neural drive (Vmax/Msup ratio: 0.14 ± 0.08 to 0.24 ± 0.20; p = .010) and a tendency towards increased VA (79% ± 9% to 84% ± 5%; p = .098), were only apparent after MST. No changes were observed in Hmax/Mmax ratio for the groups. In conclusion, external loading during exercise training appears to be a prerequisite for efferent neural drive enhancement in older adults. Thus, strength training with heavy loads should be recommended to counteract the typically observed age-related decline in motoneuron firing frequency and recruitment.

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.

Aging does not affect voluntary activation of the ankle dorsiflexors during isometric, concentric, and eccentric contractions

2005 ◽  
Vol 99 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Malgorzata Klass ◽  
Stéphane Baudry ◽  
Jacques Duchateau
Keyword(s):  
Electrical Stimulation ◽  
Compound Muscle Action Potential ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
M Wave ◽  
Mechanical Responses ◽  
Age Related ◽  
Angular Velocities ◽  
General Slowing ◽  
Ankle Dorsiflexors

This study examines the age-related deficit in force of the ankle dorsiflexors during isometric (Iso), concentric (Con), and eccentric (Ecc) contractions. More specifically, the contribution of neural and muscular mechanisms to the loss of voluntary force was investigated in men and women. The torque produced by the dorsiflexors and the surface electromyogram (EMG) from the tibialis anterior and the soleus were recorded during maximal Iso contractions and during Con and Ecc contractions performed at constant angular velocities (5–100°/s). Central activation was tested by the superimposed electrical stimulation method during maximal voluntary contraction and by computing the ratio between voluntary average EMG and compound muscle action potential (M wave) induced by electrical stimulation (average EMG/M wave). Contractile properties of the dorsiflexor muscles were investigated by recording the mechanical responses to single and paired maximal stimuli. The results showed that the age-related deficit in force (collapsed across genders and velocities) was greater for Iso (20.5%; P < 0.05) and Con (38.6%; P < 0.001) contractions compared with Ecc contractions (6.5%; P > 0.05). When the torque produced during Con and Ecc contractions was expressed relative to the maximal Iso torque, it was significantly reduced in Con contractions and increased in Ecc contractions with aging, with the latter effect being more pronounced for women. In both genders, voluntary activation was not significantly impaired in elderly adults and did not differ from young subjects. Similarly, coactivation was not changed with aging. In contrast, the mechanical responses to single and paired stimuli showed a general slowing of the muscle contractile kinetics with a slightly greater effect in women. It is concluded that the force deficit during Con and Iso contractions of the ankle dorsiflexors in advanced age cannot be explained by impaired voluntary activation or changes in coactivation. Instead, this age-related adaptation and the mechanisms that preserve force in Ecc contractions appeared to be located at the muscular level.

scholarly journals Heat acclimation has a protective effect on the central but not peripheral nervous system

2017 ◽  
Vol 123 (4) ◽  
pp. 816-824 ◽  
Author(s):  
Sebastien Racinais ◽  
Mathew G. Wilson ◽  
Nadia Gaoua ◽  
Julien D. Périard
Keyword(s):  
Working Memory ◽  
Executive Function ◽  
Conduction Velocity ◽  
Heat Acclimation ◽  
H Reflex ◽  
Voluntary Activation ◽  
Neural Drive ◽  
M Wave ◽  
Neural Adaptations ◽  
C 50

This study aimed to clarify the pathway mediating hyperthermia-induced alterations in neural drive transmission and determine if heat acclimation protects voluntary muscle activation and cognitive function in hyperthermic humans. Electrically evoked potentials (H reflex and M wave), executive function (special planning and working memory), and maximal voluntary isometric contractions (120 s) were assessed in 14 participants in control conditions [CON, 24°C, 40% relative humidity (RH)] and in a hyperthermic state (HYP, 44–50°C, 50% RH) on consecutive days in a counterbalanced order. Thereafter, participants were passively heat acclimated for 11 days (1 h per day, 48–50°C, 50% RH) before repeating the initial assessments. Heat acclimation decreased rectal temperature in CON (−0.2°C, P < 0.05), but participants were maintained at ~39°C in HYP. Heat acclimation increased the time required to reach 39°C (+9 min), along with sweat rate (+0.7 l/h), and serum extracellular expression of heat shock protein 72 (eHSP72; +20%) in HYP ( P < 0.05). M-wave and H-reflex amplitudes were lower in HYP than CON ( P < 0.05) and were not protected by heat acclimation. Nerve conduction velocity was faster in HYP than CON ( P < 0.05) without being influenced by heat acclimation. These results suggest that peripheral neural drive transmission in the hyperthermic state is primarily affected by axonal conduction velocity rather than synaptic failure. Executive function, voluntary activation, and the ability to sustain torque were impaired in HYP ( P < 0.05). However, despite no perceptual changes ( P > 0.05), heat acclimation restored executive function, while protecting the ability to sustain voluntary activation and torque production during a prolonged contraction in hyperthermia ( P < 0.05). Ultimately, heat acclimation induces beneficial central but not peripheral neural adaptations. NEW & NOTEWORTHY Heat acclimation restores planning accuracy and working memory in hyperthermic humans, together with the supraspinal capacity to sustain motor drive during a sustained maximal voluntary contraction. Electrically evoked potential data (M wave, H reflex) indicate that heat acclimation does not protect against hyperthermia-induced impairments in peripheral neural drive transmission. Heat acclimation induces beneficial central but not peripheral neural adaptations.

Postactivation Depression of the Soleus H Reflex Measured Using Threshold Tracking

2008 ◽  
Vol 100 (6) ◽  
pp. 3275-3284 ◽  
Author(s):  
Penelope A. McNulty ◽  
Stacey K. Jankelowitz ◽  
Tanya M. Wiendels ◽  
David Burke
Keyword(s):  
Plantar Flexion ◽  
H Reflex ◽  
Homosynaptic Depression ◽  
Threshold Tracking ◽  
Nonlinear Input ◽  
The Face ◽  
Reflex Gain ◽  
Afferent Inputs ◽  
Voluntary Contractions ◽  
Postactivation Depression

The interpretation of changes in the soleus H reflex is problematic in the face of reflex gain changes, a nonlinear input/output relationship for the motoneuron pool, and a nonhomogeneous response of different motoneurons to afferent inputs. By altering the stimulus intensity to maintain a constant reflex output, threshold tracking allows a relatively constant population of α-motoneurons to be studied. This approach was used to examine postactivation (“homosynaptic”) depression of the H reflex (HD) in 23 neurologically healthy subjects. The H reflex was elicited by tibial nerve stimulation at 0.05, 0.1, 0.3, 1, and 2 Hz at rest and during voluntary plantar flexion at 2.5, 5, and 10% of maximum. A computerized threshold tracking procedure was used to set the current needed to generate a target H reflex 10% of Mmax. The current needed to produce the target reflex increased with stimulus rate but not significantly beyond 1 Hz. In three subjects, the current needed to produce H reflexes of 5, 10, 15, and 20% Mmax at 0.3, 1, and 2 Hz increased with rate and with the size of the test H reflex. HD was significantly reduced during voluntary contractions. Using threshold tracking, HD was maximal at lower frequencies than previously emphasized, probably because HD is greater the larger the test H reflex. This would reinforce the greater sensitivity of small motoneurons to reflex inputs.

Neural adaptation to resistance training: changes in evoked V-wave and H-reflex responses

2002 ◽  
Vol 92 (6) ◽  
pp. 2309-2318 ◽  
Author(s):  
Per Aagaard ◽  
Erik B. Simonsen ◽  
Jesper L. Andersen ◽  
Peter Magnusson ◽  
Poul Dyhre-Poulsen
Keyword(s):  
Resistance Training ◽  
Muscle Strength ◽  
Muscle Contraction ◽  
Presynaptic Inhibition ◽  
H Reflex ◽  
Neural Adaptation ◽  
Reflex Amplitude ◽  
Reflex Responses ◽  
Adaptation Mechanisms ◽  
V Wave

Combined V-wave and Hoffmann (H) reflex measurements were performed during maximal muscle contraction to examine the neural adaptation mechanisms induced by resistance training. The H-reflex can be used to assess the excitability of spinal α-motoneurons, while also reflecting transmission efficiency (i.e., presynaptic inhibition) in Ia afferent synapses. Furthermore, the V-wave reflects the overall magnitude of efferent motor output from the α-motoneuron pool because of activation from descending central pathways. Fourteen male subjects participated in 14 wk of resistance training that involved heavy weight-lifting exercises for the muscles of the leg. Evoked V-wave, H-reflex, and maximal M-wave (Mmax) responses were recorded before and after training in the soleus muscle during maximal isometric ramp contractions. Maximal isometric, concentric, and eccentric muscle strength was measured by use of isokinetic dynamometry. V-wave amplitude increased ∼50% with training ( P < 0.01) from 3.19 ± 0.43 to 4.86 ± 0.43 mV, or from 0.308 ± 0.048 to 0.478 ± 0.034 when expressed relative to Mmax (± SE). H-reflex amplitude increased ∼20% ( P < 0.05) from 5.37 ± 0.41 to 6.24 ± 0.49 mV, or from 0.514 ± 0.032 to 0.609 ± 0.025 when normalized to Mmax. In contrast, resting H-reflex amplitude remained unchanged with training (0.503 ± 0.059 vs. 0.499 ± 0.063). Likewise, no change occurred in Mmax (10.78 ± 0.86 vs. 10.21 ± 0.66 mV). Maximal muscle strength increased 23–30% ( P < 0.05). In conclusion, increases in evoked V-wave and H-reflex responses were observed during maximal muscle contraction after resistance training. Collectively, the present data suggest that the increase in motoneuronal output induced by resistance training may comprise both supraspinal and spinal adaptation mechanisms (i.e., increased central motor drive, elevated motoneuron excitability, reduced presynaptic inhibition).

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