Measure Of Neuromuscular Fatigue Research Articles

The effect of hypertonic saline evoked muscle pain on neurophysiological changes and exercise performance in the contralateral limb

Non-local muscle pain may impair endurance performance through neurophysiological mechanisms, but these are relatively unknown. This study examined the effects of muscle pain on neuromuscular and neurophysiological responses in the contralateral limb. On separate visits, nine participants completed an isometric time to task failure (TTF) using the right knee extensors after intramuscular injection of isotonic saline (CTRL) or hypertonic saline (HYP) into the left vastus lateralis. Measures of neuromuscular fatigue were taken before, during and after the TTF using transcranial magnetic stimulation (TMS) and peripheral nerve stimulation. Mean pain intensity was greater in the left leg in HYP (3.3 ± 1.9) compared to CTRL (0.4 ± 0.7; P < 0.001) which was combined with a reduced TTF by 9.8% in HYP (4.54 ± 0.56 min) compared to CTRL (5.07 ± 0.77 min; P = 0.005). Maximum voluntary force was not different between conditions (all P > 0.05). Voluntary activation was lower in HYP compared to CTRL (P = 0.022). No difference was identified between conditions for doublet amplitude (P > 0.05). Furthermore, no difference in MEP·Mmax−1 or the TMS silent period between conditions was observed (all P > 0.05). Non-local pain impairs endurance performance of the contralateral limb. This impairment in performance is likely due to the faster attainment of the sensory tolerance limit from a greater amount of sensory feedback originating from the non-exercising, but painful, left leg.

The effect of elevated muscle pain on neuromuscular fatigue during exercise

PurposeMuscle pain can impair exercise performance but the mechanisms for this are unknown. This study examined the effects of muscle pain on neuromuscular fatigue during an endurance task.MethodsOn separate visits, twelve participants completed an isometric time-to-task failure (TTF) exercise of the right knee extensors at ~ 20% of maximum force following an intramuscular injection of isotonic saline (CTRL) or hypertonic saline (HYP) into the vastus lateralis. Measures of neuromuscular fatigue were taken before, during and after the TTF using transcranial magnetic stimulation (TMS) and peripheral nerve stimulation.ResultsThe mean pain intensity was 57 ± 10 in HYP compared to 38 ± 18 in CTRL (P < 0.001). TTF was reduced in HYP (4.36 ± 0.88 min) compared to CTRL (5.20 ± 0.39 min) (P = 0.003). Maximum voluntary force was 12% lower at minute 1 (P = 0.003) and 11% lower at minute 2 in HYP (P = 0.013) compared to CTRL. Voluntary activation was 4% lower at minute 1 in HYP compared to CTRL (P = 0.006) but not at any other time point (all P > 0.05). The TMS silent period was 9% longer at 100 s during the TTF in HYP compared to CTRL (P = 0.026).ConclusionMuscle pain reduces exercise performance through the excacerbation of neuromuscular fatigue that is central in origin. This appears to be from inhibitory feedback from group III/IV nociceptors which acts to reduce central motor output.

Preseason changes in markers of lower body fatigue and performance in young professional rugby union players

This study investigated the changes in measures of neuromuscular fatigue and physical performance in young professional rugby union players during a preseason training period. Fourteen young (age: 19.1 ± 1.2 years) professional rugby union players participated in the study. Changes in measures of lower body neuromuscular fatigue (countermovement jump (CMJ) mean power, mean force, flight-time) and physical performance (lower body strength, 40 m sprint velocity) were assessed during an 11-week preseason period using magnitude-based inferences. CMJ mean power was likely to very likely decreased during week 2 (−8.1 ± 5.5% to −12.5 ± 6.8%), and likely to almost certainly decreased from weeks 5 to 11 (−10 ± 4.3% to −14.7 ± 6.9%), while CMJ flight-time demonstrated likely to very likely decreases during weeks 2, and weeks 4–6 (−2.41 ± 1% to −3.3 ± 1.3%), and weeks 9–10 (−1.9 ± 0.9% to −2.2 ± 1.5%). Despite this, possible improvements in lower body strength (5.8 ± 2.7%) and very likely improvements in 40 m velocity (5.5 ± 3.6%) were made. Relationships between changes in CMJ metrics and lower body strength or 40 m sprint velocity were trivial or small (<0.22). Increases in lower body strength and 40 m velocity occurred over the course of an 11-week preseason despite the presence of neuromuscular fatigue (as measured by CMJ). The findings of this study question the usefulness of CMJ for monitoring fatigue in the context of strength and sprint velocity development. Future research is needed to ascertain the consequences of negative changes in CMJ in the context of rugby-specific activities to determine the usefulness of this test as a measure of fatigue in this population.

Co-Contraction of Knee Stabilizer Muscles during Sustained Squat Posture (A Yogic Posture) in Athletes

Simultaneous activation of muscles across a joint can be defined as muscle co-contraction. Its purpose is to augment the ligament function in maintenance of joint stability, provide resistance to rotation at a joint, and equalize the pressure distribution at the articular surface. The purpose of this study was to investigate the Co-contraction of selected knee stabilizer muscles as a measure of neuromuscular fatigue in relation to gender, performance and side (left and right) of male (n1=32) and female (n2=18) during sustained squat posture (yogic posture). Squat Posture was performed at an angle of 135o-150o because strength of knee stabilizers (muscles) varies from angle to angle and 135o to 150o is prominent angle range having high consideration for the performance of numerous physical daily routine activities such as walking, running, cycling, stepping and driving including development of fundamental skills for different sports across all ages and sex. Vastus Medialis (VM) and Vastus Lateralis (VL) muscles from the Quadriceps group were the knee stabilizers chosen for recording the EMG simultaneously from both right and left legs as these muscles are considered important for stabilization and protection of patellofemoral joint. The statistical analysis applied were ANOVA with post hoc analysis to determine the influence of fatigue in terms of gender, performance and side (left and right). The results showed significant female dominance behavior over males in coactivation of VM and VL muscles along with bilateral Asymetricity during sustained squat posture. The results of this study would help in better understanding the changes in knee stabilizers activation strategies that can help the clinicians and trainers in planning, execution of rehabilitation related to patellofemoral joint injuries.

Direct and indirect measurement of neuromuscular fatigue in Canadian football players.

This study assessed the effects of a fatiguing game simulation (G-Sim) on the balance of collegiate Canadian football players. The purpose of the study was to evaluate postural control as a potential tool for monitoring neuromuscular fatigue (NMF) in collision-based team sports. Fifteen male Canadian football players were recruited (mean±SD: age 21.8±1.6 years, weight 97.6±14.7 kg). Indirect NMF measures (postural sway and countermovement jump (CMJ)) were performed 24 h before (TBase), immediately before (TPre) and after (TPost), and 24 h (T24) and 48 h after (T48) a Canadian football G-Sim. Peak isometric knee extensor torque of a maximal voluntary contraction (MVC) and electrically evoked tetani at 20 Hz (P20) and 80 Hz (P80) were also recorded as direct NMF measures at TBase, TPre, TPost, and T48. At TPost, we observed significant declines in MVC, P20, and the MVC/P80 ratio (-15.3%, -15.7%, and -12.1%, respectively; n=12) along with reductions in CMJ takeoff velocity and peak power (-6.9% and -6.5%, respectively; n=12) and larger area of the center of pressure trajectory (95.2%; n=10) during a 60-s postural sway task. All variables were no longer different than baseline by T48. Acute neuromuscular impairment in this cohort is likely attributable to alterations in excitation-contraction coupling due to structural damage and central activation failure. Congruency between the direct and indirect measures of NMF suggests monitoring postural sway has the potential to identify both neuromuscular and somatosensory alterations induced by acute game-induced fatigue in collision-based team sports players.

Effect of an Acute Bout of High Intensity Game Simulation Exercise on Direct and Indirect measures of Neuromuscular Fatigue in Canadian Football Players

Effect of an Acute Bout of High Intensity Game Simulation Exercise on Direct and Indirect measures of Neuromuscular Fatigue in Canadian Football Players

Influence of Neuromuscular Fatigue on Accelerometer Load in Elite Australian Football Players

To determine the impact of neuromuscular fatigue (NMF) assessed from variables obtained during a countermovement jump on exercise intensity measured with triaxial accelerometers (load per minute [LPM]) and the association between LPM and measures of running activity in elite Australian Football. Seventeen elite Australian Football players performed the Yo-Yo Intermittent Recovery Test level 2 (Yo-Yo IR2) and provided a baseline measure of NMF (flight time:contraction time [FT:CT]) from a countermovement jump before the season. Weekly samples of FT:CT, coaches' rating of performance (votes), LPM, and percent contribution of the 3 vectors from the accelerometers in addition to high-speed-running meters per minute at >15 km/h and total distance relative to playing time (m/min) from matches were collected. Samples were divided into fatigued and nonfatigued groups based on reductions in FT:CT. Percent contributions of vectors to LPM were assessed to determine the likelihood of a meaningful difference between fatigued and nonfatigued groups. Pearson correlations were calculated to determine relationships between accelerometer vectors and running variables, votes, and Yo-Yo IR2 score. Fatigue reduced the contribution of the vertical vector by (mean ± 90% CI) -5.8% ± 6.1% (86% likely) and the number of practically important correlations. NMF affects the contribution of individual vectors to total LPM, with a likely tendency toward more running at low speed and less acceleration. Fatigue appears to limit the influence of the aerobic and anaerobic qualities assessed via the Yo-Yo IR2 test on LPM and seems implicated in pacing.

Markers of Postmatch Fatigue in Professional Rugby League Players

The aim of the present study was to identify neuromuscular, biochemical, and endocrine markers of fatigue after Rugby League match play. Seventeen elite Rugby League players were monitored for a single match. Peak rate of force development (PRFD), peak power (PP), and peak force (PF) were measured during a countermovement jump (CMJ) on a force plate pre and postmatch play. Saliva and blood samples were collected 24 hours prematch, 30 minutes prematch, 30 minutes postmatch, and then at 24-hour intervals for a period of 120 hours to determine plasma creatine kinase concentration ([CK]) and salivary cortisol concentration ([sCort]). There were significant (p < 0.05) decreases in PRFD and PP up to 24 hours postmatch with PF significantly (p < 0.05) decreased immediately postmatch. The [sCort] significantly (p < 0.05) increased from 24 hours prematch to 30 minutes prematch and up to 24 hours postmatch compared with 24 hours prematch. Plasma [CK] significantly (p < 0.05) increased 30 minutes postmatch with a peak occurring 24 hours postmatch and remained elevated above 24 hours prematch for at least 120 hours postmatch. There were significant (p < 0.05) correlations between the increase in [CK] and reduction in PRFD 30 minutes postmatch and 24 hours postmatch. The [sCort] was significantly (p < 0.05) correlated with the reduction in PF 30 minutes postmatch. Results demonstrate that neuromuscular function is compromised for up to 48 hours after match play. Elevated [CK] despite 120-hour recovery indicate that damage to muscle tissue after Rugby League match play may persist for at least 5 days postmatch. Despite the prolonged presence of elevated [CK] postmatch, strength training 48 hours postmatch may have resulted in a compensatory increase in PRFD supporting the inclusion of strength training during the short-term postmatch recovery period.

Some Unresolved Issues for the Study of Fatigue: The Way Forward

This section of the supplement “Fatigue: A New Frontier” will discuss 3 issues that have significant import for elucidating mechanisms by which fatigue occurs and its evaluation and treatment. These issues are clearly not the only ones that are important for future research or clinical practice, but they are the most prevalent issues raised in the articles of this supplement. They present significant challenges in both research and clinical arenas and offer substantial research opportunity. There exists a body of published data that leave a number of unresolved key issues. These include: 1) What are our best metrics for measuring fatigue? 2) Do the constructs of peripheral and central fatigue advance our understanding of fatigue syndromes or create arbitrary limitations? 3) Will a better understanding of the interactions among immunoregulation and metabolic control of energy production and utilization (and performance and perception) help us derive a comprehensive approach to the management of fatigue? What are the Best Metrics for Measuring Fatigue? Many of the sections of this supplement address the need for valid and reliable instruments for measuring fatigue. The authors identify instruments that were specifically developed for use in some of the disease entities they discuss. For example, the Fatigue Severity Scale has been used to assess fatigue in rheumatic diseases and multiple sclerosis. Whereas in assessing cancer-related fatigue, other self-report instruments have been used, including the Functional Assessment of Cancer Therapy-Fatigue, Cancer Fatigue Scale, and Brief Fatigue Inventory, among others. Self-reports are necessary for assessing fatigue, but many suggest that they are not sufficient. The trend is toward using instruments that are coupled with objective findings. For example, in cancer-related fatigue and the neurological conditions, studies have included measures of neuromuscular fatigue. As discussed in this theme issue, there seems to be a shift in thinking about what is most important in measuring fatigue in the elderly. In particular, the concept of fatigability, which links fatigue with function and thereby assesses the impact fatigue may have on independence, has gained momentum as the measurement of choice. Fatigue measures in the affective/fatigue or pain/fatigue overlap syndromes, such as chronic fatigue syndrome and fibromyalgia (FM), remain reliant on self-reports of symptoms, mood, and behavior. Most authors contributing to this special issue indicate that one of the more significant problems facing clinicians and researchers studying and treating fatigue is reaching agreement on which measures to use for evaluation and treatment outcomes. There has not been consensus on whether fatigue measures should or must include objective measures, or whether they need to be disease specific. There does not seem to be consensus on what the essential components of a fatigue measure need be and whether this would be true for all or most chronic medical conditions, including those that may have significant psychoaffective and biopsychosocial components. This is an opportune time to promote a Consensus Conference designed to explore issues such as how to measure fatigue and what should be included in these measures. Such a conference would also introduce the use of theories and approaches to computer technologies such as item response theory and computerized-adapted training to help assure validity and efficiency in the choice of relevant metrics. One such approach, patient reported outcomes medical information system (PROMIS), has been instrumen