Purpose: Several studies analyzed muscle activity after pre-fatigue due to co-contraction, but the effects of
antagonist contraction on agonist muscle performance are still incompletely known.
The purpose is to determine if a previous workout of an antagonist muscle can affect muscular fatigue appearance during
the subsequent agonist muscle performance.
Methods: Surface EMG was used to estimate biceps brachii muscle fatigue during isometric contraction executed after
previous contractions of the antagonist muscle. Eight expert male body-builders performed five series of isometric
contractions (30 s) alternatively according to the agonist and antagonist protocols.
Results: Within each repetition, for both biceps brachii muscles and experimental protocols, data showed a progressive
fatigue, but no continuous quantitative decreasing trend of the median frequency of the spectrum along the five
repetitions. Contraction time explained 1-91% (r2 values) of the reduction of mean activation frequency along the 30 s
(agonistic protocol); 0.7-92% for antagonistic protocol. The decrement in median frequency was only partially time–
related. A repeated measures Anova found significant differences between subjects (p<0.0001), protocols (antagonistic
greater than agonistic, p=0.03), while between sides (p=0.93) and repetitions (p=0.50), and for all interactions no
significant differences were found.
Conclusion: The present results did not confirm that the antagonistic pre-fatiguing can delay the fatigue appearance during
agonistic performance (isometric tasks). Accordingly, the antagonistic protocol does not seem to be functional in
improving the upper arm performance from a fatigue point of view, at least in trained subjects.