Evidence of nonlocal muscle fatigue in male youth

Abstract

Evidence for nonlocal muscle fatigue (NLMF) has been inconsistent in adults, with no studies investigating youth. The objective was to examine NLMF in youth. Forty-two young males (age, 10-13 years) were tested for maximal voluntary isometric contraction (MVIC) force of the ipsilateral and contralateral knee extensors at 90° and 120° knee flexion, elbow flexors at 90°, handgrip, knee extensor isokinetic torque (300°·s analyzed at 90° and 120° knee flexion), as well as a unilateral countermovement jump (CMJ) and Y Balance test (YBT). Isokinetic fatigue group (n = 15) had unilateral fatigue induced with 10 sets of 20 repetitions of maximal isokinetic knee extensor contractions at 300°·s. Isometric fatigue group (n = 15) used 10 repetitions of 6-s knee extensor MVIC whereas the control group (n = 12) were not fatigued. There was no significant difference in the response to the isometric- or isokinetic-fatigue intervention protocols. Main time effects indicated that NLMF was evident with the contralateral knee extensor MVIC at 90° (p = 0.008; 8.9%), knee extensor isokinetic torque at 90° (p < 0.001; 11.4%), and 120° (p = 0.05; 5.4%), CMJ (p = 0.02; 11.5%), handgrip (p = 0.06; 4.5%), elbow flexors (p < 0.001; 7.7%), and YBT (p = 0.001; 5.6%). Ipsilateral NLMF deficits occurred with handgrip (p < 0.001; 7.3%), elbow flexors MVICs (p < 0.001; 10.7%), CMJ (p = 0.02; 12.2%), and YBT (p = 0.002; 3.8%). NLMF with similar relative fatigue-induced deficits of fatigued and nonfatigued limbs suggest that youth fatigue is highly dependent upon the extent of activation or inhibition of the nervous system. Coaches of young athletes might consider developing technical motor skills before fatiguing exercise components, which might hinder the proficiency of their performance.

Evidence of homologous and heterologous effects after unilateral leg training in youth

“…This procedure was repeated three times for both the right and left hands with an approximate 1-min rest period and the highest value was recorded for analysis. High reliability of this test in similar pediatric population in our laboratory has been reported elsewhere (Ben Othman et al 2017).…”

“…Three trials separated by an approximate 1min rest interval for each hand were performed, and the maximum score for each hand was recorded. Excellent MVIC handgrip strength reliability measurements in children in our laboratory have been reported elsewhere (Ben Othman et al 2017).…”

“…Unilateral elbow flexors (EF) MVIC EF MVIC strength of both arms was measured using a calibrated hand held dynamometer (Microfet 2; Hoggan Health Industries Inc., Draper, Utah, USA) as previously described (Ben Othman et al 2017). The hand-held dynamometer was placed between the flexor aspect of the wrist and the lever of elbow flexion machine to ensure an isometric contraction.…”

“…MVIC handgrip strength (kg) was measured using a calibrated hand dynamometer (Takei, Tokyo, Japan) as previously described (Ben Othman et al 2017). Participants stood comfortably with the arm adducted at approximately 45°.…”

A Meta-analysis of Non-local Heterologous Muscle Fatigue

“…According to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) 46 guidelines, 30 full-text publications were thoroughly read and once the inclusion criteria were applied, a total of 6 publications were included for analysis ( Figure 1). There were 27 full-text publications excluded from the analysis; 5 examining contralateral homologous effects; 5,7,9-10,13 , 13 examining NLMF but did not include data for proper ES calculation nor variables of interest; 15,[18][19][20][22][23][24][26][27][28][29][30]34 8 studies that did not examine NLMF (e.g., coactivation, tremor, concurrent contraction, stretching, training intervention); [16][17]21,25,[31][32][33]47 and 1 study which was the review by Halperin, Chapman, and Behm. 1…”