Neuromechanical Differences between Pronated and Supinated Forearm Positions during Upper-Body Wingate Tests.

Arm-cycling is a versatile exercise modality with applications in both athletic enhancement and rehabilitation, yet the influence of forearm orientation remains understudied. Thus, this study aimed to investigate the impact of forearm position on upper-body arm-cycling Wingate tests. Fourteen adult males (27.3 ± 5.8 years) underwent bilateral assessments of handgrip strength in standing and seated positions, followed by pronated and supinated forward arm-cycling Wingate tests. Electromyography (EMG) was recorded from five upper-extremity muscles, including anterior deltoid, triceps brachii lateral head, biceps brachii, latissimus dorsi, and brachioradialis. Simultaneously, bilateral normal and propulsion forces were measured at the pedal-crank interface. Rate of perceived exertion (RPE), power output, and fatigue index were recorded post-test. The results showed that a pronated forearm position provided significantly (p < 0.05) higher normal and propulsion forces and triceps brachii muscle activation patterns during arm-cycling. No significant difference in RPE was observed between forearm positions (p = 0.17). A positive correlation was found between seated handgrip strength and peak power output during the Wingate test while pronated (dominant: p = 0.01, r = 0.55; non-dominant: p = 0.03, r = 0.49) and supinated (dominant: p = 0.03, r = 0.51; don-dominant: p = 0.04, r = 0.47). Fatigue changed the force and EMG profile during the Wingate test. In conclusion, this study enhances our understanding of forearm position's impact on upper-body Wingate tests. These findings have implications for optimizing training and performance strategies in individuals using arm-cycling for athletic enhancement and rehabilitation.

Two weeks of arm cycling sprint interval training enhances spinal excitability to the biceps brachii.

The present study aimed to investigate whether a 2-wk arm cycling sprint interval training (SIT) program modulated corticospinal pathway excitability in healthy, neurologically intact participants. We employed a pre-post study design with two groups: 1) an experimental SIT group and 2) a nonexercising control group. Transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of corticospinal axons were used at baseline and post-training to provide indices of corticospinal and spinal excitability, respectively. Stimulus-response curves (SRCs) recorded from the biceps brachii were elicited for each stimulation type during two submaximal arm cycling conditions [25 watts (W) and 30% peak power output (PPO)]. All stimulations were delivered during the mid-elbow flexion phase of cycling. Compared with baseline, performance on the time-to-exhaustion (TTE) test at post-testing was improved for members of the SIT group but was not altered for controls, suggesting that SIT improved exercise performance. There were no changes in the area under the curve (AUC) for TMS-elicited SRCs for either group. However, the AUC for TMES-elicited cervicomedullary motor-evoked potential SRCs were significantly larger at post-testing in the SIT group only (25 W: P = 0.012, d = 0.870; 30% PPO: P = 0.016, d = 0.825). This data shows that overall corticospinal excitability is unchanged following SIT, whereas spinal excitability is enhanced. Although the precise mechanisms underlying these findings during arm cycling at post-SIT are unknown, it is suggested that the enhanced spinal excitability may represent a neural adaptation to training.NEW & NOTEWORTHY Two weeks of arm cycling sprint interval training (SIT) improves subsequent aerobic exercise performance and induces changes within the descending corticospinal pathway. Specifically, spinal excitability is enhanced following training, whereas overall corticospinal excitability does not change. These results suggest that the enhanced spinal excitability may represent a neural adaptation to training. Future work is required to discern the precise neurophysiological mechanisms underlying these observations.

Reduced isometric knee extensor force following anodal transcranial direct current stimulation of the ipsilateral motor cortex.

BACKGROUND: The goal of this study was to determine if 10-min of anodal transcranial direct current stimulation (a-tDCS) to the motor cortex (M1) is capable of modulating quadriceps isometric maximal voluntary contraction (MVC) force or fatigue endurance contralateral or ipsilateral to the stimulation site. METHODS: In a randomized, cross-over design, 16 (8 females) individuals underwent two sessions of a-tDCS and two sham tDCS (s-tDCS) sessions targeting the left M1 (all participants were right limb dominant), with testing of either the left (ipsilateral) or right (contralateral) quadriceps. Knee extensor (KE) MVC force was recorded prior to and following the a-tDCS and s-tDCS protocols. Additionally, a repetitive MVC fatiguing protocol (12 MVCs with work-rest ratio of 5:10-s) was completed following each tDCS protocol. RESULTS: There was a significant interaction effect for stimulation condition x leg tested x time [F(1,60) = 7.156, p = 0.010, ηp2 = 0.11], which revealed a significant absolute KE MVC force reduction in the contralateral leg following s-tDCS (p < 0.001, d = 1.2) and in the ipsilateral leg following a-tDCS (p < 0.001, d = 1.09). A significant interaction effect for condition x leg tested [F(1,56) = 8.12, p = 0.006, ηp2 = 0.13], showed a significantly lower ipsilateral quadriceps (to tDCS) relative MVC force with a-tDCS, versus s-tDCS [t(15) = -3.07, p = 0.016, d = -0.77]. There was no significant difference between the relative contralateral quadriceps (to tDCS) MVC force for a-tDCS and s-tDCS. Although there was an overall significant [F(1,56) = 8.36, p < 0.001] 12.1% force decrease between the first and twelfth MVC repetitions, there were no significant main or interaction effects for fatigue index force. CONCLUSION: a-tDCS may be ineffective at increasing maximal force or endurance and instead may be detrimental to quadriceps force production.

Interhemispheric inhibition is different during arm cycling than a position- and intensity-matched tonic contraction.

Task-dependent changes in inhibition may explain why supraspinal excitability is higher during arm cycling than an intensity- and position-matched tonic contraction. The present study investigated whether interhemispheric inhibition (IHI) associated with biceps brachii activity was different during arm cycling, a locomotor output, compared to a tonic contraction. IHI was quantified using an ipsilateral silent period (iSP) evoked via transcranial magnetic stimulation (TMS) of the ipsilateral motor cortex. TMS was delivered at 120% resting motor threshold during the mid-elbow flexion phase of arm cycling (6 o'clock position, made relative to a clock face) and during a position- and intensity-matched tonic contraction. In total, 36 participants took part in the study. However, only 14 participants demonstrated IHI during arm cycling and 10 participants during tonic contraction. Of these participants, eight displayed clear iSPs during arm cycling and tonic contraction. The iSP duration was longer during arm cycling than tonic contraction (p < 0.05), while iSP EMG amplitude and area were not different between tasks (p > 05 for both comparisons). The main finding from this study is that IHI appears to be stronger during arm cycling than an intensity- and position-matched tonic contraction. This does not support previous findings of higher supraspinal excitability during arm cycling.

Endurance-exercise training adaptations in spinal motoneurones: potential functional relevance to locomotor output and assessment in humans.

It is clear from non-human animal work that spinal motoneurones undergo endurance training (chronic) and locomotor (acute) related changes in their electrical properties and thus their ability to fire action potentials in response to synaptic input. The functional implications of these changes, however, are speculative. In humans, data suggests that similar chronic and acute changes in motoneurone excitability may occur, though the work is limited due to technical constraints. To examine the potential influence of chronic changes in human motoneurone excitability on the acute changes that occur during locomotor output, we must develop more sophisticated recording techniques or adapt our current methods. In this review, we briefly discuss chronic and acute changes in motoneurone excitability arising from non-human and human work. We then discuss the potential interaction effects of chronic and acute changes in motoneurone excitability and the potential impact on locomotor output. Finally, we discuss the use of high-density surface electromyogram recordings to examine human motor unit firing patterns and thus, indirectly, motoneurone excitability. The assessment of single motor units from high-density recording is mainly limited to tonic motor outputs and minimally dynamic motor output such as postural sway. Adapting this technology for use during locomotor outputs would allow us to gain a better understanding of the potential functional implications of endurance training-induced changes in human motoneurone excitability on motor output.

Moving forward: methodological considerations for assessing corticospinal excitability during rhythmic motor output in humans.

The use of transcranial magnetic stimulation to assess the excitability of the central nervous system to further understand the neural control of human movement is expansive. The majority of the work performed to-date has assessed corticospinal excitability either at rest or during relatively simple isometric contractions. The results from this work are not easily extrapolated to rhythmic, dynamic motor outputs, given that corticospinal excitability is task-, phase-, intensity-, direction-, and muscle-dependent (Power KE, Lockyer EJ, Forman DA, Button DC. Appl Physiol Nutr Metab 43: 1176-1185, 2018). Assessing corticospinal excitability during rhythmic motor output, however, involves technical challenges that are to be overcome, or at the minimum considered, when attempting to design experiments and interpret the physiological relevance of the results. The purpose of this narrative review is to highlight the research examining corticospinal excitability during a rhythmic motor output and, importantly, to provide recommendations regarding the many factors that must be considered when designing and interpreting findings from studies that involve limb movement. To do so, the majority of work described herein refers to work performed using arm cycling (arm pedaling or arm cranking) as a model of a rhythmic motor output used to examine the neural control of human locomotion.

Interhemispheric inhibition to the biceps brachii during arm cycling.

This is the first demonstration of interhemispheric inhibition (IHI) during a locomotor output, arm cycling. IHI was quantified by assessing the depth of the ipsilateral silent period (iSP) evoked via transcranial magnetic stimulation of the motor cortex. There was a significant reduction in electromyography (EMG) amplitude of the iSP during cycling compared with the control EMG (16.8% ± 17.1%; p < 0.001). Depth and area for measuring the iSP during arm cycling are discussed. Novelty: This is the first study to demonstrate activation of the cortical circuit, interhemispheric inhibition, during a locomotor output.

Modulation of Corticospinal Excitability with Contralateral Arm Cycling.

This is the first study to examine the influence of activity in one limb on corticospinal excitability to the contralateral limb during a locomotor output. Corticospinal and spinal excitability to the biceps brachii of the ipsilateral arm were assessed using transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of corticospinal axons, respectively. Responses were evoked during the mid-elbow extension position of arm cycling across three different cycling tasks: (1) bilateral arm cycling (BL), (2) unilateral, contralateral cycling with the ipsilateral arm moving passively (IP), and (3) unilateral, contralateral cycling with the ipsilateral arm at rest (IR). Each of these three tasks were performed at two cadences: 60 and 90 rpm. TMS-induced motor evoked potential (MEPs) amplitudes were significantly smaller during BL compared to the IP and IR conditions; however, MEP amplitudes were not significantly different between IP and IR. TMES-evoked cervicomedullary MEP (CMEPs) amplitudes followed a similar pattern of task-dependent modulation, with BL having the smallest CMEPs and IR having the largest. In line with our previous findings, MEP amplitudes increased and CMEP amplitudes decreased as the cadence increased from 60 to 90 rpm. We suggest that the higher corticospinal excitability to the ipsilateral limb during the IP and IR conditions was predominantly due to disinhibition at both the cortical and spinal levels.

Changes in muscle activity during the flexion and extension phases of arm cycling as an effect of power output are muscle-specific.

Arm cycling is commonly used in rehabilitation settings for individuals with motor impairments in an attempt to facilitate neural plasticity, potentially leading to enhanced motor function in the affected limb(s). Studies examining the neural control of arm cycling, however, typically cycle using a set cadence and power output. Given the importance of motor output intensity, typically represented by the amplitude of electromyographic (EMG) activity, on neural excitability, surprisingly little is known about how arm muscle activity is modulated using relative workloads. Thus, the objective of this study was to characterize arm muscle activity during arm cycling at different relative workloads. Participants (n = 11) first completed a 10-second maximal arm ergometry sprint to determine peak power output (PPO) followed by 11 randomized trials of 20-second arm cycling bouts ranging from 5-50% of PPO (5% increments) and a standard 25 W workload. All submaximal trials were completed at 60 rpm. Integrated EMG amplitude (iEMG) was assessed from the biceps brachii, brachioradialis, triceps brachii, flexor carpi radialis, extensor carpi radialis and anterior deltoid of the dominant arm. Arm cycling was separated into two phases, flexion and extension, relative to the elbow joint for all comparisons. As expected, iEMG amplitude increased during both phases of cycling for all muscles examined. With the exception of the triceps brachii and extensor carpi radialis, iEMG amplitudes differed between the flexion and extension phases. Finally, there was a linear relationship between iEMG amplitude and the %PPO for all muscles during both elbow flexion and extension.

The effect of 6 weeks of high intensity interval training on myelin biomarkers and demyelination in experimental autoimmune encephalomyelitis model.

Exercise has been shown to increase myelin biomarkers such as klotho and PLP and improve clinical and pathological symptoms using the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS). In the present study, we evaluated whether 6 weeks of high-intensity interval training (HIIT) prior to induction of EAE increase klotho and/or PLP and attenuate the severity of symptoms and/or disease progression in EAE model. Our data demonstrate that HIIT increased klotho and PLP and decreased disability. These proteins are associated with maintaining myelination and further research is required to examine potential clinical relevance.

Neuromuscular Mechanisms Underlying Changes in Force Production during an Attentional Focus Task.

We examined the effects of attentional focus cues on maximal voluntary force output of the elbow flexors and the underlying physiological mechanisms. Eleven males participated in two randomized experimental sessions. In each session, four randomized blocks of three maximal voluntary contractions (MVC) were performed. The blocks consisted of two externally and two internally attentional focus cued blocks. In one of the sessions, corticospinal excitability (CSE) was measured. During the stimulation session transcranial magnetic, transmastoid and Erb's point stimulations were used to induce motor evoked potentials (MEPs), cervicomedullary MEP (CMEPs) and maximal muscle action potential (Mmax), respectively in the biceps brachii. Across both sessions forces were lower (p = 0.024) under the internal (282.4 ± 60.3 N) compared to the external condition (310.7 ± 11.3 N). Muscle co-activation was greater (p = 0.016) under the internal (26.3 ± 11.5%) compared with the external condition (21.5 ± 9.4%). There was no change in CSE. Across both sessions, force measurements were lower (p = 0.033) during the stimulation (279.0 ± 47.1 N) compared with the no-stimulation session (314.1 ± 57.5 N). In conclusion, external focus increased force, likely due to reduced co-activation. Stimulating the corticospinal pathway may confound attentional focus. The stimulations may distract participants from the cues and/or disrupt areas of the cortex responsible for attention and focus.

Corticospinal excitability to the biceps and triceps brachii during forward and backward arm cycling is direction- and phase-dependent.

The purpose of this study was to evaluate corticospinal excitability to the biceps and triceps brachii during forward (FWD) and backward (BWD) arm cycling. Corticospinal and spinal excitability were assessed using transcranial magnetic stimulation and transmastoid electrical stimulation to elicit motor evoked potentials (MEPs) and cervicomedullary evoked potentials (CMEPs), respectively. MEPs and CMEPs were recorded from the biceps and triceps brachii during FWD and BWD arm cycling at 2 positions, 6 and 12 o'clock. The 6 o'clock position corresponded to mid-elbow flexion and extension during FWD and BWD cycling, respectively, while 12 o'clock corresponded to mid-elbow extension and flexion during FWD and BWD cycling, respectively. During the flexion phase, MEP and CMEP amplitudes of the biceps brachii were higher during FWD cycling. However, during the extension phase, MEP and CMEP amplitudes were higher during BWD cycling. For the triceps brachii, MEP amplitudes were higher during FWD cycling regardless of phase. However, CMEP amplitudes were phase-dependent. During the flexion phase, CMEPs of the triceps brachii were higher during FWD cycling compared with BWD, but during the extension phase CMEPs were higher during BWD cycling compared with FWD. The data suggest that corticospinal and spinal excitability to the biceps brachii is phase- and direction-dependent. In the triceps brachii, spinal, but not corticospinal, excitability is phase-dependent when comparing FWD and BWD cycling. Novelty This is the first study to assess corticospinal excitability during FWD and BWD locomotor output. Corticospinal excitability during arm cycling depends on the direction, phase, and muscle being assessed.

Short-interval intracortical inhibition of the biceps brachii in chronic-resistance versus non-resistance-trained individuals.

The purpose of this study was to investigate the effects of chronic resistance training on corticospinal excitability and short intracortical inhibition of the biceps brachii. Eight chronic resistance-trained (RT) and eight non-RT participants completed one experimental session including a total of 30 brief (7 s) elbow flexors isometric contractions at various force outputs [15, 25 and 40% of maximum voluntary contraction (MVC)]. Before the contractions, MVC, maximal compound muscle action potential (Mmax) during 5% MVC and active motor threshold (AMT) at the three various force outputs were recorded. MVC force of the chronic-RT group was 24% higher than the non-RT group (p ≤ 0.001; ω2 = 0.72). The chronic-RT group had lower AMTs at targeted forces of 15 and 25% MVC (p = 0.022 and p = 0.012, respectively) compared to the non-RT group. During 25 and 40% of MVC, the non-RT group exhibited decreased SICI in comparison to the chronic-RT group (p = 0.008; ω2 = 0.35 and p = 0.03; ω2 = 0.21, respectively). However, SICI did not differ between groups at 15% MVC (p = 0.62). In conclusion, chronic resistance training significantly reduces SICI. This suggests the presence of an adaptive process of inhibitory and facilitatory network activation, which may cancel out the SICI, allowing for increased corticomotor drive to the exercised muscle following a long period of resistance training.

Corticospinal-Evoked Responses from the Biceps Brachii during Arm Cycling across Multiple Power Outputs.

Background: We examined corticospinal and spinal excitability across multiple power outputs during arm cycling using a weak and strong stimulus intensity. Methods: We elicited motor evoked potentials (MEPs) and cervicomedullary motor evoked potentials (CMEPs) in the biceps brachii using magnetic stimulation over the motor cortex and electrical stimulation of corticospinal axons during arm cycling at six different power outputs (i.e., 25, 50, 100, 150, 200 and 250 W) and two stimulation intensities (i.e., weak vs. strong). Results: In general, biceps brachii MEP and CMEP amplitudes (normalized to maximal M-wave (Mmax)) followed a similar pattern of modulation with increases in cycling intensity at both stimulation strengths. Specifically, MEP and CMEP amplitudes increased up until ~150 W and ~100 W when the weak and strong stimulations were used, respectively. Further increases in cycling intensity revealed no changes on MEP or CMEP amplitudes for either stimulation strength. Conclusions: In general, MEPs and CMEPs changed in a similar manner, suggesting that increases and subsequent plateaus in overall excitability are likely mediated by spinal factors. Interestingly, however, MEP amplitudes were disproportionately larger than CMEP amplitudes as power output increased, despite being initially matched in amplitude, particularly with strong stimulation. This suggests that supraspinal excitability is enhanced to a larger degree than spinal excitability as the power output of arm cycling increases.

Delayed-Onset Muscle Soreness and Topical Analgesic Alter Corticospinal Excitability of the Biceps Brachii.

INTRODUCTION: The interactive effect of delayed-onset muscle soreness (DOMS) and a topical analgesic on corticospinal excitability was investigated. METHODS: Thirty-two participants completed Experiments A (no DOMS) and B (DOMS). For each experiment, participants were randomly assigned to two groups: 1) topical analgesic gel (topical analgesic, n = 8), or 2) placebo gel (placebo, n = 8) group. Before the application of gel (pregel), as well as 5, 15, 30, and 45 min postgel, motor-evoked potential (MEP) area, latency, and silent period, as well as cervicomedullary MEP and maximal compound motor unit action potential areas and latencies were measured. In addition, pressure-pain threshold (PPT) was measured pre-DOMS and at the same timepoints in experiment B. RESULTS: In experiment A, neither group showed a significant change for any outcome measure. In experiment B, both groups exhibited a significant decrease in PPT from pre-DOMS to pregel. After the application of topical analgesic, but not placebo, there was a significant increase in PPT at 45 min postgel, respectively, compared with pregel and a main effect of time for the silent period to increase compared with pregel. Participants with DOMS had reduced MEP and cervicomedullary MEP areas and increased corticospinal silent periods compared with those who did not have DOMS. CONCLUSIONS: These findings suggest that DOMS reduced corticospinal excitability and after the administration of menthol-based topical analgesic, there was a reduction in pain, which was accompanied by increased corticospinal inhibition.

Short-interval intracortical inhibition to the biceps brachii is present during arm cycling but is not different than a position- and intensity-matched tonic contraction.

We have previously shown that supraspinal excitability is higher during arm cycling than a position- and intensity-matched tonic contraction. The present study sought to determine if short-interval intracortical inhibition (SICI) was present during arm cycling and if so, if the amount of SICI was different from an intensity-matched tonic contraction. SICI was assessed using conditioning stimuli (CS) of 70 and 90% of active motor threshold (AMT) and a test stimulus (TS) of 120% AMT at an interstimulus interval (ISI) of 2.5 ms. SICI was elicited in all participants; on average (i.e., cycling and tonic contraction grouped) test MEP amplitudes were reduced by 64.2% (p < 0.001) and 62.8% (p = 0.001) following conditioning stimuli of 70% and 90% AMT, respectively. There was no significant difference in extent of SICI between tasks (p = 0.360). These data represent the novel finding that SICI is present during arm cycling, a motor output partially mediated by spinal interneuronal networks. The amount of SICI, however, was not different from that during a position- and intensity-matched tonic contraction, suggesting that SICI is not likely a cortical mechanism contributing to higher supraspinal excitability during arm cycling compared to tonic contraction.

Corticospinal Excitability to the Biceps Brachii is Not Different When Arm Cycling at a Self-Selected or Fixed Cadence.

BACKGROUND: The present study compared corticospinal excitability to the biceps brachii muscle during arm cycling at a self-selected and a fixed cadence (SSC and FC, respectively). We hypothesized that corticospinal excitability would not be different between the two conditions. METHODS: The SSC was initially performed and the cycling cadence was recorded every 5 s for one minute. The average cadence of the SSC cycling trial was then used as a target for the FC of cycling that the participants were instructed to maintain. The motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation (TMS) of the motor cortex were recorded from the biceps brachii during each trial of SSC and FC arm cycling. RESULTS: Corticospinal excitability, as assessed via normalized MEP amplitudes (MEPs were made relative to a maximal compound muscle action potential), was not different between groups. CONCLUSIONS: Focusing on maintaining a fixed cadence during arm cycling does not influence corticospinal excitability, as assessed via TMS-evoked MEPs.

Corticospinal excitability, assessed through stimulus response curves, is phase-, task-, and muscle-dependent during arm cycling.

The purpose of the present study was to examine corticospinal excitability to the biceps and triceps brachii during arm cycling and an intensity-matched tonic contraction using stimulus response curves (SRCs) elicited via transcranial magnetic stimulation (TMS). Corticospinal excitability was assessed using TMS elicited motor-evoked potentials (MEPs) at eight different stimulation intensities (85-190% of MEP threshold). MEPs were recorded during arm cycling at two different positions, mid-elbow flexion (6 o'clock relative to a clock face) and mid-elbow extension (12 o'clock relative to a clock face), in addition to an intensity-matched (12 o'clock) tonic contraction. At the 12 o'clock position, the slope of the SRC was significantly lower during arm cycling than the tonic contraction for the biceps brachii (Cycling: 0.64 ± 0.47, Tonic: 1.02 ± 0.38, P < 0.05) but was not different for the triceps brachii (Cycling: 1.33 ± 0.49, Tonic: 1.48 ± 0.43, P = 0.42). Within arm cycling, the SRC slope was significantly greater at the 6 o'clock position than 12 o'clock position for the biceps brachii (6 o'clock: 1.37 ± 0.24, 12 o'clock: 0.64 ± 0.47, P < 0.05) but was not different for the triceps brachii (6 o'clock: 1.11 ± 0.28, 12 o'clock: 1.33 ± 0.49, P = 0.34). These findings demonstrate that corticospinal excitability to the biceps brachii is task-dependent during the extension phase of arm cycling. Neither position nor task influenced corticospinal excitability to the triceps brachii, providing further support that the motor control of locomotor outputs is muscle-specific.

The effect of dominant first dorsal interosseous fatigue on the force production of a contralateral homologous and heterologous muscle.

Crossover and nonlocal muscle fatigue (NLMF) has generally focused on large muscle groups. It is unclear if fatigue of a small muscle can result in NLMF of a larger muscle. The purpose of the present study was to examine the effect of small muscle (first dorsal interosseous; FDI) fatigue on the force and activation of contralateral homologous and larger heterologous muscles (biceps brachii; BB). Fifteen right-handed male subjects performed 3 pre-test index finger abduction or elbow flexion maximum voluntary isometric contractions (MVICs) on the nondominant side. Subsequently, they performed two 100-s index finger abduction MVICs on the dominant side (experimental (fatigue) group) or rested for 5 min (control group). Afterwards, a single MVIC and a 12-repetition MVIC fatiguing protocol were completed with index finger abduction or elbow flexion on the nondominant side. Force and electromyography (EMG) were measured from both sides. The force and EMG (median frequency; MDF) of nonexercised index finger abductors (IFA)/FDI and elbow flexors (EF)/BB significantly decreased after the fatiguing protocol. Compared with the control condition, the nonexercised IFA (12.5% and 5.7%) had significantly greater force and MDF fatigue indexes than the EF (5.2% and 1.7%). There were no significant force differences with the single MVIC test between conditions. The small muscle fatiguing protocol produced NLMF effects on both contralateral homologous and larger heterologous muscles, with the force decrements greater with the homologous muscle.

Quantitative feature analysis of continuous analytic wavelet transforms of electrocardiography and electromyography.

Theoretical and practical advances in time-frequency analysis, in general, and the continuous wavelet transform (CWT), in particular, have increased over the last two decades. Although the Morlet wavelet has been the default choice for wavelet analysis, a new family of analytic wavelets, known as generalized Morse wavelets, which subsume several other analytic wavelet families, have been increasingly employed due to their time and frequency localization benefits and their utility in isolating and extracting quantifiable features in the time-frequency domain. The current paper describes two practical applications of analysing the features obtained from the generalized Morse CWT: (i) electromyography, for isolating important features in muscle bursts during skating, and (ii) electrocardiography, for assessing heart rate variability, which is represented as the ridge of the main transform frequency band. These features are subsequently quantified to facilitate exploration of the underlying physiological processes from which the signals were generated.This article is part of the theme issue 'Redundancy rules: the continuous wavelet transform comes of age'.