Knee extension fatigue attenuates repeated force production of the elbow flexors

Abstract

Non-local muscle fatigue has been demonstrated with unilateral activities, where fatiguing one limb alters opposite limb forces. Fewer studies have examined if non-local fatigue occurs with unrelated muscles. The purpose of this study was to investigate if knee extensors fatigue alters elbow flexors force and electromyography (EMG) activity. Eighteen males completed a control and fatiguing session (randomised). Blood lactate was initially sampled followed by three maximal voluntary contractions (MVC) with the elbow flexors and two with the knee extensors. Thereafter, subjects either sat (control) or performed five sets of bilateral dynamic knee extensions to exhaustion using a load equal to the dominant limb MVC (1-min rest between sets). Immediately afterwards, subjects were assessed for blood lactate and unilateral knee extensors MVC, and after 1 min performed a single unilateral elbow flexor MVC. Two minutes later, subjects performed 12 unilateral elbow flexor MVCs (5 s contraction/10 s rest) followed by a third blood lactate test. Compared to control, knee extensor force dropped by 35% (p < 0.001; ES = 1.6) and blood lactate increased by 18% (p < 0.001; ES = 2.8). Elbow flexor forces were lower after the fatiguing protocol only during the last five MVCs (p < 0.05; ES = ∼ 0.58; ∼ 5%). No changes occurred between conditions in EMG. Elbow flexor forces significantly decreased after knee extensors fatigue. The effect was revealed during the later stages of the repeated MVCs protocol, demonstrating that non-local fatigue may have a stronger effect on repeated rather than on single attempts of maximal force production.

Effect of unilateral knee extensor fatigue on force and balance of the contralateral limb

“…Furthermore, contralateral single MVICs may not be as sensitive to crossover fatigue as repeated fatiguing contractions. Halperin et al (2014b) reported no crossover effects with a single MVIC, but force decrements were found in the last five MVICs of a 12 MVIC (5 s contraction/10 s recovery) repetition protocol. Amann et al (2013) tested the contralateral knee extensors with two different tests following a unilateral fatiguing protocol: an MVIC and a constant load knee extension to failure.…”

“…The effects of fatigue can either be localized or global (Rattey et al 2006). Some research has shown that local fatigue occurring in one limb can result in decreased force production in the homologous muscle (Martin and Rattey 2007;Halperin et al 2014a;Kawamoto et al 2014) as well as in heteronymous muscles (Takahashi et al 2011;Kennedy et al 2013;Halperin et al 2014b) of a non-fatigued limb. This crossover or non-local fatigue effect has been identified for upper (Humphry et al 2004;Halperin et al 2014a, b) and lower limbs (Rattey et al 2006;Martin and Rattey 2007;McLean and Samorezov 2009;Paillard et al 2010;Halperin et al 2014a, b).…”

Acute bouts of upper and lower body static and dynamic stretching increase non-local joint range of motion

“…The lack of change in EMG activity may be related to the insensitivity of the non-linear force-EMG relationship, which is particularly prominent at the high force portion of the EMG-force relationship (Lawrence and De Luca 1983). Furthermore, surface EMG may not be sensitive enough to illustrate small modulations of supraspinal, spinal or muscle excitability (Halperin et al 2014b). For example, Aboodarda et al (2014) reported lower VL EMG, although increased thoracic motor evoked potentials indicated increased spinal excitability following an elbow flexor fatigue protocol (NLMF).…”

“…NLMF is generally attributed to a central nervous system-induced inhibition (Chaouachi et al 2015;da Silva et al 2015;Halperin et al 2014b). Paillard et al (2010) found crossover fatigue affecting postural control during single-leg stance in the contralateral limb following ipsilateral quadriceps femoris fatigue generated either by neuromuscular electrical stimulation or by isometric voluntary muscular contractions.…”

“…The effects of fatigue on non-local muscles other than contralateral limbs have also been investigated. Halperin et al (2014b) reported that a knee extensor fatigue protocol resulted in performance decrements of the elbow flexors. However, in a second study by Halperin et al (2014c), non-local muscle fatigue of unilateral knee extensors and elbow flexors decreased force production and activation with contralateral knee extensors, but not elbow flexors.…”