Fatigue reduces the complexity of knee extensor torque fluctuations during maximal and submaximal intermittent isometric contractions in man

Pethick, Jamie; Winter, Samantha L.

doi:10.1113/jphysiol.2014.284380

Cited by 18 publications

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“…The position of the cathode was located using a motor point pen (Compex; DJO Global, Guildford, UK), and another Ag/AgCl electrode was placed on that point. The establishment of the appropriate stimulator current (200-s pulse width) was then performed, as described by Pethick et al (42), wherein current was incrementally increased until knee extensor torque and the compound motor unit action potential (M-wave) response to single twitches had plateaued and was verified during stimulation delivered during a contraction at 50% MVC to ensure a maximal M-wave was also evident during an isometric contraction. The stimulator current was then increased to 130% of the current, producing a maximal M-wave.…”

Section: Protocolmentioning

confidence: 99%

“…In the latter case, older adults produce less complex force output during a sustained finger abduction task than young subjects, suggesting that for the same relative force output motor control is diminished in older muscle (59). We have recently extended the loss of complexity hypothesis to acute neuromuscular system changes caused by fatigue in healthy young adults (42). In that study, repeated maximal and submaximal isometric contractions of the knee extensors resulted in the development of neuromuscular fatigue of both central and peripheral origin (i.e., fatigue residing in the central nervous system or the muscle, respectively), assessed using maximal voluntary contractions (MVCs) and supramaximal stimulation of the femoral nerve (42; for review, see Ref.…”

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confidence: 93%

“…As such, the CT represents a critical metabolic (29) and neuromuscular fatigue threshold (8), and consequently, metabolite-mediated peripheral fatigue is thought to be the dominant mechanism of torque losses above CT (7,8). If the fatigue-induced loss of torque complexity (42) is mechanistically coupled to this form of peripheral fatigue, then such a loss should only occur during contractions performed above the CT. Furthermore, if the loss of complexity is related to the magnitude of peripheral fatigue development above CT (rather than simply task duration), then torque complexity should decrease to reach similar values at task failure, regardless of the duration of exercise producing that failure.…”

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confidence: 99%

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Loss of knee extensor torque complexity during fatiguing isometric muscle contractions occurs exclusively above the critical torque

Pethick

Winter

2016

American Journal of Physiology-Regulatory, Integrative and Comp

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134

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The complexity of knee extensor torque time series decreases during fatiguing isometric muscle contractions. We hypothesized that because of peripheral fatigue, this loss of torque complexity would occur exclusively during contractions above the critical torque (CT). Nine healthy participants performed isometric knee extension exercise (6 s of contraction, 4 s of rest) on six occasions for 30 min or to task failure, whichever occurred sooner. Four trials were performed above CT (trials S1-S4, S1 being the lowest intensity), and two were performed below CT (at 50% and 90% of CT). Global, central, and peripheral fatigue were quantified using maximal voluntary contractions (MVCs) with femoral nerve stimulation. The complexity of torque output was determined using approximate entropy (ApEn) and the detrended fluctuation analysis-α scaling exponent (DFA-α). The MVC torque was reduced in trials below CT [by 19 ± 4% (means ± SE) in 90%CT], but complexity did not decrease [ApEn for 90%CT: from 0.82 ± 0.03 to 0.75 ± 0.06, 95% paired-samples confidence intervals (CIs), 95% CI = -0.23, 0.10; DFA-α from 1.36 ± 0.01 to 1.32 ± 0.03, 95% CI -0.12, 0.04]. Above CT, substantial reductions in MVC torque occurred (of 49 ± 8% in S1), and torque complexity was reduced (ApEn for S1: from 0.67 ± 0.06 to 0.14 ± 0.01, 95% CI = -0.72, -0.33; DFA-α from 1.38 ± 0.03 to 1.58 ± 0.01, 95% CI 0.12, 0.29). Thus, in these experiments, the fatigue-induced loss of torque complexity occurred exclusively during contractions performed above the CT.

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Section: Protocolmentioning

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Loss of knee extensor torque complexity during fatiguing isometric muscle contractions occurs exclusively above the critical torque

Pethick

Winter

2016

American Journal of Physiology-Regulatory, Integrative and Comp

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134

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“…There is some supporting evidence of how fatigue may increase the risk of injury. Studies have shown that muscle fatigue reduces the neuromuscular systems adaptability to external perturbations [16], so the athlete may be less able to react to altered loading when landing or changing direction during a game. The neuromuscular and perceptual fatigue created by consecutive days of tournament play can create impairments in sprinting and jumping ability, and biochemical markers of muscle damage and reduced mood states [17], all of which may reduce the athlete's ability to move and land optimally.…”

Section: Relationship Issues 12% (2 Out Of 17)mentioning

confidence: 99%

Retrospective Analysis of Non-Contact ACL Injury Risk: A Case Series Review of Elite Female Athletes

Herrington¹

2017

J Sports Med Ther

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Background: Literature on ACL injury is limited when assessing for the presence and interaction of multiple risk factors simultaneously. Identifying risk factor interaction may increase the impact of prevention programmes to target ACL injury reduction. The aim of this study was to retrospectively assess ACL injured female athletes to identify which modifi able and non-modifi able risk factors were present at the time of injury.Method: Seventeen female athletes who had sustained a non-contact ACL injury were interviewed retrospectively to assess for the presence of reported risk factors for ACL injury.Result: This retrospective analysis ACL injury cases highlighted a number of factors which were present with high frequency across this group of cases. All had non-contact ACL injury occurring during cutting or landing, which suggests a predisposing defi cit in neuromuscular control. This poor neuromuscular control could be exacerbated by the presence of fatigue identifi ed within the cohort. This poor control could be further infl uenced by the fact a majority of athletes had another signifi cant injury in the 12 weeks prior to ACL injury. The restriction to training could have either decreased fatigue resistance, or potentially changed their movement pattern because of the method of injury management undertaken. Conclusion:This case series provides insight into the interaction of risk factors for ACL injury in sportswomen, with the presence of another injury disrupting training, decreasing the athletes work capacity and fatigue resistance, being compounded perceived or actually elevated levels of fatigue, leading to the potential for abhorrent movement patterns and increased injury risk.

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“…13,14 Fatigue can be identified through electromyography (EMG=, in which it is represented as an increased signal amplitude and decreased spectral frequencies. 15 Muscle fatigue can also be quantified as a decrease in power or maximal force measured immediately after a fatiguing contraction.…”

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Relationships Among Vertical Jumping Performance, EMG Activation, and Knee Extensor and Flexor Muscle Strength in Turkish Elite Male Volleyball Players

Şimşek¹,

Kırkaya²,

Güngör³

et al. 2016

Turkiye Klinikleri J Sports Sci

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A AB BS S T TR RA AC CT T O Ob bj je ec ct ti iv ve e: : The aim of this study was to determine the relationship among maximum isokinetic concentric knee torque, muscle activity (EMG) and vertical jumping height of Turkish elite male volleyball players. M Ma at te er ri ia al l a an nd d M Me et th ho od ds s: : Twelve elite male volleyball players were included voluntary in this study. EMG activity was recorded on the vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF) and biceps femoris (BF) muscles of volleyball players during five maximal isokinetic concentric-concentric contractions at 60°/s, 180°/s and 240°/s. Peak anaerobic power output was calculated using vertical jumping heights. A repeated measures analysis of variance (ANOVA) was used to compare torque values in different angular velocities. Pearson's correlation coefficient was used to evaluate the relationship between torque and muscle activation values. The statistical significance level was set at p<0.05. R Re es su ul lt ts s: : The results of this study show that Hamstring/Quadriceps (H:Q) ratios are greatest at an angular velocity of 240°/s. Differences in EMG activity during isokinetic testing were observed between the knee extensor (VL, VM) and flexor muscles (BF) (p<0.05). Repeated maximal isokinetic concentric contractions caused to increase the EMG activity of the knee and flexor muscles (p<0.05). In this study, it is demonstrated that volleyball players produced significantly higher counter movement jumping (CMJ) heights than squat jumping (SJ) heights (10%) (p=0.028). The maximum power of a CMJ was higher than that of an SJ (p=0.000), concentric work (p=0.001) and peak anaerobic power (p=0.020). Additionally, negative correlation was observed between VM, RF and BF muscle activation and isokinetic concentric-concentric torque values. C Co on nc cl lu us si io on n: : It was thus concluded that the muscle activity of the knee extensor and flexor muscles changes with change in isokinetic torque at different angular velocity and repetition.K Ke ey y W Wo or rd ds s: : Muscle activation; torque; isokinetic force Ö ÖZ ZE ET T A Am ma aç ç: : Çalışmanın amacı Türk elit erkek voleybolcuların diz ekstansör ve fleksör kaslarının maksimum konsantrik tork, dikey sıçrama ve kassal aktivasyon (EMG) değerleri arasındaki ilişkileri belirlemektir. G Ge er re eç ç v ve e Y Yö ön nt te em ml le er r: : On iki elit erkek voleybolcu gönüllü olarak çalışmaya dahil edilmiştir. Voleybolcuların vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF) ve biceps femoris (BF) kaslarının kassal aktiviteleri (EMG), 60°/s, 180°/s and 240°/s açısal hızlarda, 5 maksimal izokinetik konsantrik-konsantrik kasılma sırasında kayıt edilmiştir. Zirve anaerobik güç çıktısı, squat sıçrama (SS) ve aktif sıçrama (AS) verileri hesaplanarak oluşturulmuştur. Farklı açısal hızlarda elde edilen tork değerleri tekrarlayan ölçümlerde varyans analizi (ANOVA) ile karşılaştırılmıştır. Tork ve kassal aktivasyon değer-leri arasındaki korelasyonlar Pearson korelasyon kats...

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Fatigue reduces the complexity of knee extensor torque fluctuations during maximal and submaximal intermittent isometric contractions in man

Cited by 18 publications

References 0 publications

Loss of knee extensor torque complexity during fatiguing isometric muscle contractions occurs exclusively above the critical torque

Loss of knee extensor torque complexity during fatiguing isometric muscle contractions occurs exclusively above the critical torque

Retrospective Analysis of Non-Contact ACL Injury Risk: A Case Series Review of Elite Female Athletes

Relationships Among Vertical Jumping Performance, EMG Activation, and Knee Extensor and Flexor Muscle Strength in Turkish Elite Male Volleyball Players

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