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Daniel Gilfeather, Grant Norte, Christopher D. Ingersoll and Neal R. Glaviano

–reconstructed patients. 7 Poor neuromuscular function of the gluteal muscles has also been related to altered frontal hip and knee plane motion 2 , 3 and decreased subjective knee function. 8 Due to their relationship between gluteal weakness and poor subjective and objective functional measurements, optimizing

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Gregory M. Gutierrez, Nicole D. Jackson, Kristin A. Dorr, Sarah E. Margiotta and Thomas W. Kaminski

Context:

Lateral ankle sprains occur more frequently than any other orthopedic injury. Athletes often report sustaining more injuries late in competition when fatigue is present.

Objective:

To evaluate neuromuscular function of the ankle musculature after fatigue. Design: Experimental, pretest-posttest.

Setting:

Research laboratory.

Participants:

Ten female and 9 male college-aged subjects.

Intervention:

Fatigue was induced via continuous concentric and eccentric muscle actions of the ankle: inversion (INV), eversion (EV), plantar flexion (PF), and dorsiflexion (DF).

Main Outcome Measures:

Peak torque (PT), peak EMG, and median frequency (MF) were calculated prefatigue and postfatigue in the tibialis anterior (TA), peroneus longus (PER), and lateral gastrocnemius (GAS) muscles.

Results:

Main effects were noted for test (P < 0.0125) in all statistical tests performed indicating changes in PT, peak EMG, and MF after fatigue.

Conclusions:

A significant decrease in MF of the PER muscle after PF fatigue and corresponding with a decreased firing rate, may be of importance, especially with regard to the role in countering the violent moment seen with inversion ankle sprains.

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Dean Norris, David Joyce, Jason Siegler, James Clock and Ric Lovell

is a multifactorial construct, a variety of monitoring strategies are often employed within the professional setting, such as markers of muscle damage, neuromuscular function (NF), endocrine responses, immune status, and psychological well-being. 3 , 4 While informative, due to cost and time

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Gregory Roe, Joshua Darrall-Jones, Kevin Till, Padraic Phibbs, Dale Read, Jonathon Weakley and Ben Jones

Purpose:

To evaluate changes in performance of a 6-s cycle-ergometer test (CET) and countermovement jump (CMJ) during a 6-wk training block in professional rugby union players.

Methods:

Twelve young professional rugby union players performed 2 CETs and CMJs on the 1st and 4th mornings of every week before the commencement of daily training during a 6-wk training block. Standardized changes in the highest score of 2 CET and CMJ efforts were assessed using linear mixed modeling and magnitude-based inferences.

Results:

After increases in training load during wk 3 to 5, moderate decreases in CMJ peak and mean power and small decreases in flight time were observed during wk 5 and 6 that were very likely to almost certainly greater than the smallest worthwhile change (SWC), suggesting neuromuscular fatigue. However, only small decreases, possibly greater than the SWC, were observed in CET peak power. Changes in CMJ peak and mean power were moderately greater than in CET peak power during this period, while the difference between flight time and CET peak power was small.

Conclusion:

The greater weekly changes in CMJ metrics in comparison with CET may indicate differences in the capacities of these tests to measure training-induced lower-body neuromuscular fatigue in rugby union players. However, future research is needed to ascertain the specific modes of training that elicit changes in CMJ and CET to determine the efficacy of each test for monitoring neuromuscular function in rugby union players.

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Rich D. Johnston, Tim J. Gabbett, David G. Jenkins and Michael J. Speranza

Purpose:

To assess the impact of different repeated-high-intensity-effort (RHIE) bouts on player activity profiles, skill involvements, and neuromuscular fatigue during small-sided games.

Participants:

22 semiprofessional rugby league players (age 24.0 ± 1.8 y, body mass 95.6 ± 7.4 kg).

Methods:

During 4 testing sessions, they performed RHIE bouts that each differed in the combination of contact and running efforts, followed by a 5-min off-side small-sided game before performing a second bout of RHIE activity and another 5-min small-sided game. Global positioning system microtechnology and video recordings provided information on activity profiles and skill involvements. A countermovement jump and a plyometric push-up assessed changes in lower- and upper-body neuromuscular function after each session.

Results:

After running-dominant RHIE bouts, players maintained running intensities during both games. In the contact-dominant RHIE bouts, reductions in moderate-speed activity were observed from game 1 to game 2 (ES = –0.71 to –1.06). There was also moderately lower disposal efficiency across both games after contact-dominant RHIE activity compared with running-dominant activity (ES = 0.62–1.02). Greater reductions in lower-body fatigue occurred as RHIE bouts became more running dominant (ES = –0.01 to –1.36), whereas upper-body fatigue increased as RHIE bouts became more contact dominant (ES = –0.07 to –1.55).

Conclusions:

Physical contact causes reductions in running intensity and the quality of skill involvements during game-based activities. In addition, the neuromuscular fatigue experienced by players is specific to the activities performed.

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Mitchell Naughton, Joanna Miller and Gary J. Slater

potential to adversely affect neuromuscular function and prolong athletic recovery. It is well known that high-intensity and/or unaccustomed eccentric exercise causes EIMD through exposure to an inappropriate level of mechanical stress. 6 EIMD results in soreness, myofibrillar disruption, and release of

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Dale I. Lovell, Ross Cuneo and Greg C. Gass

This study examined the effect of aerobic training on leg strength, power, and muscle mass in previously sedentary, healthy older men (70–80 yr). Training consisted of 30–45 min of cycle ergometry at 50–70% maximal oxygen consumption (VO2max), 3 times weekly for 16 wk, then 4 wk detraining, or assignment to a nontraining control group (n = 12 both groups). Training increased leg strength, leg power, upper leg muscle mass, and VO2max above pretraining values (21%, 12%, 4%, and 15%, respectively; p < .05). However, all gains were lost after detraining, except for some gain in VO2max. This suggests that cycle ergometry is sufficient stimulus to improve neuromuscular function in older men, but gains are quickly lost with detraining. For the older population cycle ergometry provides the means to not only increase aerobic fitness but also increase leg strength and power and upper leg muscle mass. However, during periods of inactivity neuromuscular gains are quickly lost.

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Gregory Roe, Joshua Darrall-Jones, Kevin Till, Padraic Phibbs, Dale Read, Jonathon Weakley and Ben Jones

This study established the between-days reliability and sensitivity of a countermovement jump (CMJ), plyometric push-up, well-being questionnaire, and whole-blood creatine kinase concentration ([CK]) in elite male youth rugby union players. The study also established the between-days reliability of 1, 2, or 3 CMJs and plyometric-push-up attempts. Twenty-five players completed tests on 2 occasions separated by 5 d (of rest). Between-days typical error, coefficient of variation (CV), and smallest worthwhile change (SWC) were calculated for the well-being questionnaire, [CK], and CMJ and plyometric-push-up metrics (peak/mean power, peak/mean force, height, flight time, and flight-time to contraction-time ratio) for 1 maximal effort or taking the highest score from 2 or 3 maximal efforts. The results suggest that CMJ mean power (2 or 3 attempts), peak force, or mean force and plyometric-push-up mean force (from 2 or 3 attempts) should be used for assessing lower- and upper-body neuromuscular function, respectively, due to both their acceptable reliability (CV < 5%) and good sensitivity (CV < SWC). The well-being questionnaire and [CK] demonstrated between-days CVs >5% (7.1% and 26.1%, respectively) and poor sensitivity (CV > SWC). The findings from this study can be used when interpreting fatigue markers to make an objective decision about a player’s readiness to train or compete.

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Adam S. Lepley, Allison M. Strouse, Hayley M. Ericksen, Kate R. Pfile, Phillip A. Gribble and Brian G. Pietrosimone

Context:

Components of gluteal neuromuscular function, such as strength and corticospinal excitability, could potentially influence alterations in lower extremity biomechanics during jump landing.

Objective:

To determine the relationship between gluteal muscle strength, gluteal corticospinal excitability, and jump-landing biomechanics in healthy women.

Setting:

University laboratory.

Design:

Descriptive laboratory study.

Participants:

37 healthy women (21.08 ± 2.15 y, 164.8 ± 5.9 cm, 65.4 ± 12.0 kg).

Interventions:

Bilateral gluteal strength was assessed through maximal voluntary isometric contractions (MVIC) using an isokinetic dynamometer. Strength was tested in the open chain in prone and side-lying positions for the gluteus maximus and gluteus medius muscles, respectively. Transcranial magnetic stimulation was used to elicit measures of corticospinal excitability. Participants then performed 3 trials of jump landing from a 30-cm box to a distance of 50% of their height, with an immediate rebound to a maximal vertical jump. Each jump-landing trial was video recorded (2-D) and later scored for errors.

Main Outcome Measures:

MVICs normalized to body mass were used to assess strength in the gluteal muscles of the dominant and nondominant limbs. Corticospinal excitability was assessed by means of active motor threshold (AMT) and motor-evoked potentials (MEP) elicited at 120% of AMT. The Landing Error Scoring System (LESS) was used to evaluate jump-landing biomechanics.

Results:

A moderate, positive correlation was found between dominant gluteus maximus MEP and LESS scores (r = .562, P = .029). No other significant correlations were observed for MVIC, AMT, or MEP for the gluteus maximus and gluteus medius, regardless of limb.

Conclusions:

The findings suggest a moderate relationship between dominant gluteus maximus corticospinal excitability and a clinical measure of jump-landing biomechanics. Further research is required to substantiate the findings and expand our understanding of the central nervous system’s role in athletic movement.

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John J. McMahon, Shannon Murphy, Sophie J.E. Rej and Paul Comfort

Purpose:

Gross measures of countermovement-jump (CMJ) performance are commonly used to track maturational changes in neuromuscular function in rugby league (RL). The purpose of this study was to conduct both a gross and a more detailed temporal-phase analysis of the CMJ performances of senior and academy RL players, to provide greater insight into how neuromuscular function differs between these groups.

Methods:

Twenty senior and 14 academy (under-19) male RL players performed 3 maximal-effort CMJs on a force platform, with forward dynamics subsequently employed to allow gross performance measures and entire kinetic– and kinematic–time curves to be compared between groups.

Results:

Jump height (JH), reactive strength index modified, concentric displacement, and relative concentric impulse (C-IMP) were the only gross measures that were greater for senior players (d = 0.58–0.91) than for academy players. The relative force- and displacement–time curves were similar between groups, but the relative power– and velocity–time curves were greater (d = 0.59–0.97) for the senior players at 94–96% and 89–100% of the total movement time, respectively.

Conclusions:

The CMJ distinguished between senior and academy RL players, with seniors demonstrating greater JH through applying a larger C-IMP and thus achieving greater velocity throughout the majority of the concentric phase and at takeoff. Therefore, academy RL players should train to improve triple (ie, ankle, knee, and hip) extension velocity during the CMJ to bring their JH scores in line with those attained by senior players.