Neuromuscular fatigue following high versus low-intensity eccentric exercise of biceps brachii muscle

PurposeThis study investigated neuromuscular fatigue following high versus low-intensity eccentric exercise corresponding to the same amount of work.MethodsTen volunteers performed two eccentric exercises of the elbow flexors: a high-intensity versus a low-intensity exercise. Maximal voluntary contraction torque and surface electromyography of the biceps brachii muscle were recorded before, immediately and 48 h after exercises. Maximal voluntary activation level, neural (M-wave) and contractile (muscular twitch) properties of the biceps brachii muscle were analysed using electrical stimulation techniques.ResultsMaximal voluntary contraction torque was significantly (P < 0.01) reduced immediately and 48 h after exercise but the reduction was not different between the two conditions. Electromyography associated with maximal voluntary contraction significantly decreased (P < 0.05) immediately and 48 h after exercise for both conditions while maximal voluntary activation level was only significantly reduced immediately after the high-intensity exercise. Peak twitch alterations were observed immediately and 48 h after exercise for both conditions while M-wave did not change.ConclusionHigh and low-intensity eccentric exercises with the same amount of work induced the same reduction in maximal strength capacities of the biceps brachii muscles. The magnitude of peripheral and central fatigue was very similar in both conditions.     

Intra- and interday reliability of voluntary and electrically stimulated isometric contractions of the quadriceps femoris

The reliability of voluntary and electrically stimulated isometric contractions of m. quadriceps femoris of male participants (n = 10; age 30 ± 8 years; height 1.79 ± 0.05 m; body mass 79.4 ± 8.3 kg) was investigated using ratio limits of agreement (LoA) on a time scale common to examine recovery from muscle damaging exercise. No systematic changes in reliability occurred over time (baseline versus 2, 24, 48, and 72 h). Maximal voluntary contraction (MVC) and interpolated twitch technique (ITT) showed no mean bias (P > 0.05) with 95% LoA of ±12.7 and ±5.4, respectively. Resting twitch and potentiated doublet peak force showed no mean bias (P > 0.05). However, 95% LoA were smaller for the doublet (±13.9) than the twitch (±32.0). Twitch and doublet rates showed similar trends. Ratio of low (20 Hz) to high (50 Hz) frequency forces showed no mean bias (P > 0.05) and 95% LoA of (±9.2). However, there was significant mean bias (P < 0.05) and wider 95% LoA for peak force, contraction and relaxation parameters of the low and high frequency forces. In conclusion, MVC, ITT, potentiated doublet and the ratio of low to high frequency forces are recommended to most reliably examine functional muscle recovery between 2 and 72 h after damaging exercise.     

Adaptive changes in motor control of rhythmic movement after maximal eccentric actions

Effects of an exhaustive eccentric exercise (EE) on the motor control of maximal velocity rhythmic elbow extension/flexion movement (RM) were examined in eight male students. The exhaustive EE consisted of 100 maximal eccentric actions of the elbow flexor muscles. Movement range was 40–170° in EE at an angular velocity of 2 rad s^?1. A directive scaled RM of 60° with visual feedback was performed in a sitting position, with the right forearm fixed to the lever arm in horizontal plane above protractor. Surface electromyographic activity (EMG) was recorded from the biceps brachii (BB) and triceps brachii (TB) muscles. Maximal isokinetic eccentric and concentric tests and RM test were conducted before, after, 0.5 h, 2 days and 7 days after the exercise. Dynamic force production was deteriorated after EE (P < .001), and did not recover fully within 7 days. The delayed recovery phase was characterized by delayed onset of muscle soreness (DOMS) and elevated serum creatine kinase (CK) activity. The RM test revealed a delayed increase of the fatigued BB muscle EMG activity, but the maximal RM velocity could be preserved. The present results emphasize the capacity of the neuromuscular system to compensate for prolonged eccentric-induced contractile failure by optimizing antagonistic muscles coordination in a demanding rhythmic task. The underlying compensatory mechanisms could be related to increased sensitization of small diameter muscle nerve endings.     

History dependence of the electromyogram: Implications for isometric steady-state EMG parameters following a lengthening or shortening contraction

Residual force enhancement (RFE) and force depression (FD) refer to an increased or decreased force following an active lengthening or shortening contraction, respectively, relative to the isometric force produced at the same activation level and muscle length. Our intent was to determine if EMG characteristics differed in the RFE or FD states compared with a purely isometric reference contraction for maximal and submaximal voluntary activation of the adductor pollicis muscle. Quantifying these alterations to EMG in history-dependent states allows for more accurate modeling approaches for movement control in the future. For maximal voluntary contractions (MVC), RFE was 6–15% (P < 0.001) and FD was 12–19% (P < 0.001). The median frequency of the EMG was not different between RFE, FD and isometric reference contractions for the 100% and 40% MVC intensities (P > 0.05). However, root mean square EMG (EMG_RMS) amplitude for the submaximal contractions was higher in the FD and lower in the RFE state, respectively (P < 0.05). For maximal contractions, EMG_RMS was lower for the FD state but was the same for the RFE state compared to the isometric reference contractions (P > 0.05). Neuromuscular efficiency (NME; force/EMG) was lower in the force depressed state and higher in the force enhanced state (P < 0.05) compared to the isometric reference contractions. EMG spectral properties were not altered between the force-enhanced and depressed states relative to the isometric reference contractions, while EMG amplitude measures were.     

Rapid torque development in older female fallers and nonfallers: A comparison across lower-extremity muscles

The objective of this study was to compare reaction time, joint torque, rate of torque development, and magnitude of neuromuscular activation of lower-extremity muscles in elderly female fallers and nonfallers. Participants included 11, elderly, female fallers (71.3 ± 5.4 years) and twelve nonfallers (71.3 ± 6.2 years) who completed a fall risk questionnaire. Then, maximal, voluntary, isometric contractions of the knee and ankle muscles were performed in reaction to a visual cue to determine joint torque, rate of torque development, reaction time, and nervous activation of agonists and antagonists. Results indicated that significantly more fallers reported “dizziness upon rising”, “use of balance altering medications”, “stress or depression”, “not enough sleep”, “arthritis in lower body”, “chronic pain in lower body”, and “tiring easily while walking” (all P < 0.05). Normalized dorsiflexion and plantarflexion strength scores (summation of peak torque, rate of torque development and impulse) were lower in fallers than in nonfallers (P < 0.05). When summed across lower-extremity muscle groups, fallers demonstrated 19% lower peak torque and 29% longer motor time (P < 0.05). In conclusion, comprehensive fall risk screening and prevention programs should address both neuromuscular and non-muscular factors, and, weakness of the ankle dorsiflexors and plantarflexors should be further studied as potential contributors to falls in older adults.     

Ultrasonographic quantification of architectural response in tibialis anterior to neuromuscular electrical stimulation

While muscle contraction in voluntary efforts has been widely investigated, little is known about contraction during neuromuscular electrical stimulation (NMES). The aim of this study was to quantify in vivo muscle architecture of agonist and antagonist muscles at the ankle joint during NMES. Muscle fascicle lengths and pennation angles of the tibialis anterior (TA) and lateral gastrocnemius muscles were assessed via ultrasonography in 8 healthy young males. Measures were obtained during maximal NMES and torque-matched voluntary dorsiflexion contractions. In the TA, NMES induced a shorter fascicle length (67.2 ± 8.1 mm vs 74.6 ± 11.4 mm; p = 0.04) and a greater pennation angle (11.0 ± 2.4° vs 9.3 ± 2.5°; p = 0.03) compared with voluntary torque-matched dorsiflexion contractions. Architectural responses in the antagonist lateral gastrocnemius muscle did not significantly differ from rest or between voluntary and electrically induced contractions (p > 0.05). Contraction of the antagonist muscle was not a contributing factor to a greater fascicle shortening and increased pennation angle in the TA during NMES. TA architectural response during NMES likely arose from the contribution of muscle synergists during voluntary contractions coupled with a potentially localized contractile activity under the stimulation electrodes during NMES induced contractions.     

Knee flexor strength and bicep femoris electromyographical activity is lower in previously strained hamstrings

The aim of this study was to determine if athletes with a history of hamstring strain injury display lower levels of surface EMG (sEMG) activity and median power frequency in the previously injured hamstring muscle during maximal voluntary contractions. Recreational athletes were recruited, 13 with a history of unilateral hamstring strain injury and 15 without prior injury. All athletes undertook isokinetic dynamometry testing of the knee flexors and sEMG assessment of the biceps femoris long head (BF) and medial hamstrings (MHs) during concentric and eccentric contractions at ±180 and ±60° s^?1. The knee flexors on the previously injured limb were weaker at all contraction speeds compared to the uninjured limb (+180° s^?1 p = 0.0036; +60° s^?1 p = 0.0013; ?60° s^?1 p = 0.0007; ?180° s^?1 p = 0.0007) whilst sEMG activity was only lower in the BF during eccentric contractions (?60° s^?1 p = 0.0025; ?180° s^?1 p = 0.0003). There were no between limb differences in MH sEMG activity or median power frequency from either BF or MH in the injured group. The uninjured group showed no between limb differences in any of the tested variables. Secondary analysis comparing the between limb difference in the injured and the uninjured groups, confirmed that previously injured hamstrings were mostly weaker (+180° s^?1 p = 0.2208; +60° s^?1 p = 0.0379; ?60° ^?1 p = 0.0312; ?180° s^?1 p = 0.0110) and that deficits in sEMG were confined to the BF during eccentric contractions (?60° s^?1 p = 0.0542; ?180° s^?1 p = 0.0473). Previously injured hamstrings were weaker and BF sEMG activity was lower than the contralateral uninjured hamstring. This has implications for hamstring strain injury prevention and rehabilitation which should consider altered neural function following hamstring strain injury.     

Repetitive eccentric muscle contractions increase torque unsteadiness in the human triceps brachii

Torque steadiness and low-frequency fatigue (LFF) were examined in the human triceps brachii after concentric or eccentric fatigue protocols. Healthy young males (n = 17) performed either concentric or eccentric elbow extensor contractions until the eccentric maximal voluntary torque decreased to 75% of pre-fatigue for both (concentric and eccentric) protocols. The number of concentric contractions was greater than the number of eccentric contractions needed to induce the same 25% decrease in eccentric MVC torque (52.2 ± 2.9 vs. 41.5 ± 2.1 for the concentric and eccentric protocols, respectively, p < .01). The extent of peripheral fatigue was ～12% greater after the concentric compared to the eccentric protocol (twitch amplitude), whereas LFF (increase in double pulse torque/single pulse torque), was similar across protocols. Steadiness, or the ability for a subject to hold a submaximal isometric contraction, was ～20 % more impaired during the Ecc protocol (p = .052). Similarly, the EMG activity required to hold the torque steady was nearly 20% greater after the eccentric compared to concentric protocol. These findings support that task dependent eccentric contractions preferentially alter CNS control during a precision based steadiness task.     

Spatial reorganisation of muscle activity correlates with change in tangential force variability during isometric contractions

The aim of this study was to quantify the effects of spatial reorganisation of muscle activity on task-related and tangential components of force variability during sustained contractions. Three-dimensional forces were measured from isometric elbow flexion during submaximal contractions (50 s, 5–50% of maximal voluntary contraction (MVC)) and total excursion of the centre of pressure was extracted. Spatial electromyographic (EMG) activity was recorded from the biceps brachii muscle. The centroids of the root mean square (RMS) EMG and normalised mutual information (NMI) maps were computed to assess spatial muscle activity and spatial relationship between EMG and task-related force variability, respectively. Result showed that difference between the position of the centroids at the beginning and at the end of the contraction of the RMS EMG and the NMI maps were different in the medial–lateral direction (P < 0.05), reflecting that muscle regions modulate their activity without necessarily modulating the contribution to the task-related force variability over time. Moreover, this difference between shifts of the centroids was positively correlated with the total excursion of the centre of pressure at the higher levels of contractions (>30% MVC, R² > 0.30, P < 0.05), suggesting that changes in spatial muscle activity could impact on the modulation of tangential forces. Therefore, within-muscle adaptations do not necessarily increase force variability, and this interaction can be quantified by analysing the RMS EMG and the NMI map centroids.     

Assessment of quadriceps muscle weakness in patients after total knee arthroplasty and total hip arthroplasty: Methodological issues

The aim of this exploratory study was to verify whether the evaluation of quadriceps muscle weakness is influenced by the testing modality (isometric vs. isokinetic vs. isoinertial) and by the calculation method (within-subject vs. between-subject comparisons) in patients 4–8 months after total knee arthroplasty (TKA, n = 29) and total hip arthroplasty (THA, n = 30), and in healthy controls (n = 19). Maximal quadriceps strength was evaluated as (1) the maximal voluntary contraction (MVC) torque during an isometric contraction, (2) the peak torque during an isokinetic contraction, and (3) the one repetition maximum (1-RM) load during an isoinertial contraction. Muscle weakness was calculated as the difference between the involved and the uninvolved side (within-subject comparison) and as the difference between the involved side of patients and controls (between-subject comparison). Muscle weakness estimates were not significantly affected by the calculation method (within-subject vs. between-subject; P > 0.05), whereas a significant main effect of testing modality (P < 0.05) was observed. Isometric MVC torque provided smaller weakness estimates than isokinetic peak torque (P = 0.06) and isoinertial 1-RM load (P = 0.008), and the clinical occurrence of weakness (proportion of patients with large strength deficits) was also lower for MVC torque. These results have important implications for the evaluation of quadriceps muscle weakness in TKA and THA patients 4–8 months after surgery.     

Concordance of the location of the innervation zone of the tibialis anterior muscle using voluntary and imposed contractions by electrostimulation

Background: The innervation zone (IZ) corresponds to the location of the neuromuscular junctions. Its location can be determined by using arranged surface linear electrode arrays. Typically, voluntary muscle contractions (VC) are used in this method. However, it also may be necessary to locate the IZ under clinical conditions such as spasticity, in which this type of contraction is difficult to perform. Therefore, contractions imposed by electrostimulation (ES) can be an alternative. There is little background comparing the locations of IZ obtained by two different types of contractions. Objective: Evaluate the concordance between using voluntary and imposed contractions from electrostimulation in order to determine the location of the innervation zone of the tibialis anterior muscle in healthy volunteers. Methods: The tibialis anterior (TA) muscle of sixteen volunteers (men: 8; women: 8; age: 22.1 ± 1.4 years, weight: 61.6 ± 7.5 kg, height: 167.1 ± 7.5 cm) were evaluated using a linear electrode array. The IZ of the TA muscle was located using two types of muscle contractions, voluntary (10% MVC) and imposed contractions by ES. The concordance between both conditions was evaluated using the Bland–Altman method and the concordance correlation coefficient (CCC). The analyses were applied to the absolute and relative positions to the length of an anatomical landmark frame. Results: CCC for absolute position was 0.98 (p < 0.0001, 95% CI [0.98–1.00], and CCC for relative positions also was 0.98 (p < 0.0001, 95% CI [0.97–1.00]). The Bland–Altman analysis for absolute data showed an average difference of −0.63 mm (SD: 4.1). Whereas, for adjusted data, the average difference was −0.20% (SD: 1.2). The power of the results, based on absolute data, was 98%, whereas for relative data, 82%. Conclusion: In healthy volunteers, there was a substantially concordance between the location of the IZ of the TA muscle derived from using contractions imposed by ES and the location derived from using VC.     

Optimal whole-body vibration settings for muscle strength and power enhancement in human knee extensors

This study compared the effects of 6-week whole-body vibration (WBV) training programs with different frequency and peak-to-peak displacement settings on knee extensor muscle strength and power. The underlying mechanisms of the expected gains were also investigated. Thirty-two physically active male subjects were randomly assigned to a high-frequency/high peak-to-peak displacement group (HH; n = 12), a low-frequency/low peak-to-peak displacement group (LL; n = 10) or a sham training group (SHAM; n = 10). Maximal voluntary isometric, concentric and eccentric torque of the knee extensors, maximal voluntary isometric torque of the knee flexors, jump performance, voluntary muscle activation, and contractile properties of the knee extensors were assessed before and after the training period. Significant improvement in knee extensor eccentric voluntary torque (P < 0.01), knee flexor isometric voluntary torque (P < 0.05), and jump performance (P < 0.05) was observed only for HH group. Regardless of the group, knee extensor muscle contractile properties (P < 0.05) were enhanced. No modification was observed for voluntary muscle activation or electrical activity of agonist and antagonist muscles. We concluded that high-frequency/high peak-to-peak displacement was the most effective vibration setting to enhance knee extensor muscle strength and jump performance during a 6-week WBV training program and that these improvements were not mediated by central neural adaptations.     

Bacterial decolorization and degradation of the reactive dye Reactive Red 180 by Citrobacter sp. CK3

A bacterial strain, CK3, with remarkable ability to decolorize the reactive textile dye Reactive Red 180, was isolated from the activated sludge collected from a textile mill. Phenotypic characterization and phylogenetic analysis of the 16S rDNA sequence indicated that the bacterial strain belonged to the genus Citrobacter. Bacterial isolate CK3 showed a strong ability to decolorize various reactive textile dyes, including both azo and anthraquinone dyes. Anaerobic conditions with 4 g l^?1 glucose, pH = 7.0 and 32 °C were considered to be the optimum decolorizing conditions. Citrobacter sp. CK3 grew well in a high concentration of dye (200 mg l^?1), resulting in approximately 95% decolorization extent in 36 h, and could tolerate up to 1000 mg l^?1 of dye. UV–vis analyses and colorless bacterial cells suggested that Citrobacter sp. CK3 exhibited decolorizing activity through biodegradation, rather than inactive surface adsorption. It is the first time that a bacterial strain of Citrobacter sp. has been reported with decolorizing ability against both azo and anthraquinone dyes. High decolorization extent and facile conditions show the potential for this bacterial strain to be used in the biological treatment of dyeing mill effluents.     

The minimum number of contractions required to examine the EMG amplitude versus isometric force relationship for the vastus lateralis and vastus medialis

Studies have demonstrated that the electromyographic (EMG) amplitude versus submaximal isometric force relationship is relatively linear. The purpose of this investigation was to determine the minimum number of contractions required to study this relationship. Eighteen men (mean age = 23 years) performed isometric contractions of the leg extensors at 10–90% of the maximum voluntary contraction (MVC) in 10% increments while surface EMG signals were detected from the vastus lateralis and vastus medialis. Linear regression was used to determine the coefficient of determination, slope coefficient, and y-intercept for each muscle and force combination with successively higher levels included in the model (i.e., 10–30%, … 10–90% MVC). For the slope coefficients, there was a main effect for force combination (P < .001). The pairwise comparisons showed there was no difference from 10–60% through 10–90% MVC. For the y-intercepts, there were main effects for both muscle (vastus lateralis [4.3 μV RMS] > vastus medialis [−3.7 μV RMS]; P = .034) and force combination (P < .001), with similar values shown from 10–50% through 10–90% MVC. The linearity of the absolute EMG amplitude versus isometric force relationship for the vastus lateralis and vastus medialis suggests that investigators may exclude high force contractions from their testing protocol.     

Heavy-intensity aerobic exercise affects the isokinetic torque and functional but not conventional hamstrings:quadriceps ratios

Running exercises are frequently related to muscular injuries, which may be a result of muscular imbalance. The present study aimed to verify the effects of heavy-intensity continuous running exercise on the functional and conventional hamstrings:quadriceps ratios, and also in the knee flexors and extensors EMG activity in active non-athletic individuals. Sixteen active males performed maximal isokinetic concentric and eccentric knee flexions and extensions at 60° s^?1 and 180° s^?1. In another session, the same procedure was conducted after a continuous running exercise at 95% onset of blood lactate accumulation. Torque and electromyographic ratios were calculated from peak torque and integrated electromyographic activity (knee flexor and extensors). Creatine kinase was measured before and 24 h after running exercise. Eccentric torque (knee flexion and extension) decreased significantly after running only at 180° s^?1 (p < 0.05). No differences were found for the conventional torque ratios (p > 0.05), however, the functional torque ratios at 180° s^?1 decreased significantly after running (p < 0.05). No effects on the electromyographic activity and electromyographic ratios were found (p > 0.05). Creatine kinase increased slightly 24 h after running (p < 0.05). Heavy-intensity continuous running exercise decreased knee flexor and extensor eccentric torque, and functional torque ratios under fast velocities (180° s^?1), probably as result of peripheral fatigue.     

Local muscle cooling does not impact expression of mitochondrial-related genes

Recovery that takes place in a cold environment after endurance exercise elevates PGC-1α mRNA whereas ERRα and NRF2 mRNA expression are inhibited. However, the effect of local skeletal muscle cooling on mitochondrial-related gene expression is unknown.PurposeTo determine the impact of local skeletal muscle cooling during recovery from an acute bout of exercise on mitochondrial-related gene expression.MethodsRecreationally-trained male cyclists (n=8, age 25±3 y, height 181±6 cm, weight 79±8 kg, 12.8±3.6% body fat, VO_2peak 4.52±0.88 L·min⁻¹ protocol) completed a 90-min variable intensity cycling protocol followed by 4 h of recovery. During recovery, ice was applied intermittently to one leg (ICE) while the other leg served as a control (CON). Intramuscular temperature was recorded continuously. Muscle biopsies were taken from each vastus lateralis at 4 h post-exercise for the analysis of mitochondrial-related gene expression.ResultsIntramuscular temperature was colder in ICE (26.7±1.1 °C) than CON (35.5±0.1 °C) throughout the 4 h recovery period (p<0.001). There were no differences in expression of PGC-1α, TFAM, NRF1, NRF2, or ERRα mRNA between ICE and CON after the 4 h recovery period.ConclusionLocal muscle cooling after exercise does not impact the expression of mitochondrial biogenesis-related genes compared to recovery from exercise in control conditions. When these data are considered with previous research, the stimuli for cold-induced gene expression alterations may be related to factors other than local muscle temperature. Additionally, different intramuscular temperatures should be examined to determine dose-response of mitochondrial-related gene expression.     

Torque-onset determination: Unintended consequences of the threshold method

Background: Compared with visual torque-onset-detection (TOD), threshold-based TOD produces onset bias, which increases with lower torques or rates of torque development (RTD). Purpose: To compare the effects of differential TOD-bias on common contractile parameters in two torque-disparate groups. Methods: Fifteen boys and 12 men performed maximal, explosive, isometric knee-extensions. Torque and EMG were recorded for each contraction. Best contractions were selected by peak torque (MVC) and peak RTD. Visual-TOD-based torque-time traces, electromechanical delays (EMD), and times to peak RTD (tRTD) were compared with corresponding data derived from fixed 4-N m- and relative 5%MVC-thresholds. Results: The 5%MVC TOD-biases were similar for boys and men, but the corresponding 4-N m-based biases were markedly different (40.3 ± 14.1 vs. 18.4 ± 7.1 ms, respectively; p < 0.001). Boys–men EMD differences were most affected, increasing from 5.0 ms (visual) to 26.9 ms (4 N m; p < 0.01). Men’s visually-based torque kinetics tended to be faster than the boys’ (NS), but the 4-N m-based kinetics erroneously depicted the boys as being much faster to any given %MVC (p < 0.001). Conclusions: When comparing contractile properties of dissimilar groups, e.g., children vs. adults, threshold-based TOD methods can misrepresent reality and lead to erroneous conclusions. Relative-thresholds (e.g., 5% MVC) still introduce error, but group-comparisons are not confounded.     

Quadriceps EMG frequency content following isometric lumbar extension exercise

A relationship exists between muscles of the lumbar spine and those of the lower extremity where the quadriceps become more inhibited after lumbar paraspinal. The purpose of this experiment was to compare surface electromyography (sEMG) total frequency content after lumbar paraspinal fatiguing exercise. Scope: 50 subjects performed fatiguing lumbar extension exercise indexed by downward shifts in median frequency calculated from lumbar paraspinal sEMG signal. Before and after each exercise set we recorded maximal, isometric knee extension torque and quadriceps central activation ratio (QI) using the superimposed burst technique while recording vastus lateralis sEMG. We calculated total frequency content of the sEMG signal (fEMG_TOTAL) as the area of the quadriceps sEMG frequency spectrum. Quadriceps fEMG_TOTAL decreased from baseline following the first and second exercise sets. There was no significant change in quadriceps sEMG median frequency among baseline and post-exercise measures. The change in fEMG_TOTAL was correlated with the change in QI following the first (r = ?0.41, P = 0.003) and second (r = ?0.32, P = 0.02) exercise sets. Conclusion: Quadriceps fEMG_TOTAL decreased following fatiguing lumbar extension exercise, in the absence of a significant change in quadriceps median frequency.     

Examining the reliability of the flexor carpi radialis V-wave at different levels of muscle contraction

This study examined the reliability and scaling of the flexor carpi radialis (FCR) V-wave during submaximal and maximal voluntary muscle contractions (MVC). 23 participants were tested on three separate sessions. For each session, participants performed isometric wrist flexions at five contraction levels (20, 40, 60, 80 and 100 %MVC). When the target contraction level was reached, a supramaximal electrical stimulus was applied to the median nerve in order to elicit an FCR V-wave. Across all participants, the FCR V-wave amplitude, normalized to its superimposed M-wave amplitude, increased from 0.030 ± 0.001 to 0.143 ± 0.015 (P < 0.001) as the muscle contraction increased from 20 to 100 %MVC. Contraction level did not influence the reliability of evoking the FCR V-wave, as the V-wave demonstrated both stability and consistency. With the exception of a single day main effect during the 20 %MVC condition, V:M_sup was not different across days or trials (P > 0.05) indicating measurement stability. High reliability co-efficients (0.827–0.913) at each contraction level signified measurement consistency. This study establishes that FCR V-waves can be reliably evoked during both submaximal and maximal muscle contractions and suggests the possibility for FCR V-wave recordings to be used to document neuromuscular adaptations associated with factors such as training or fatigue.