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Regional changes in muscle activity do not underlie the repeated bout effect in the human gastrocnemius muscle
Author(s) -
Pincheira Patricio A.,
MartinezValdes Eduardo,
GuzmanVenegas Rodrigo,
Falla Deborah,
Garrido Marta I.,
Cresswell Andrew G.,
Lichtwark Glen A.
Publication year - 2021
Publication title -
scandinavian journal of medicine and science in sports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.575
H-Index - 115
eISSN - 1600-0838
pISSN - 0905-7188
DOI - 10.1111/sms.13912
Subject(s) - gastrocnemius muscle , medicine , eccentric exercise , delayed onset muscle soreness , heel , muscle fatigue , hyperalgesia , eccentric , skeletal muscle , repeated measures design , anesthesia , physical medicine and rehabilitation , anatomy , electromyography , muscle damage , nociception , statistics , physics , receptor , mathematics , quantum mechanics
The repeated bout effect (RBE) confers protection following exercise‐induced muscle damage. Typical signs of this protective effect are significantly less muscle soreness and faster recovery of strength after the second bout. The aim of this study was to compare regional changes in medial gastrocnemius (MG) muscle activity and mechanical hyperalgesia after repeated bouts of eccentric exercise. Twelve healthy male participants performed two bouts of eccentric heel drop exercise (separated by 7 days) while wearing a vest equivalent to 20% of their body weight. High‐density MG electromyographic amplitude maps and topographical pressure pain sensitivity maps were created before, two hours (2H), and two days (2D) after both exercise bouts. Statistical parametric mapping was used to identify RBE effects on muscle activity and mechanical hyperalgesia, using pixel‐level statistics when comparing maps. The results revealed a RBE, as a lower strength loss (17% less; P < .01) and less soreness (50% less; P < .01) were found after the second bout. However, different muscle regions were activated 2H and 2D after the initial bout but not following the repeated bout. Further, no overall changes in EMG distribution or mechanical hyperalgesia were found between bouts. These results indicate that muscle activation is unevenly distributed during the initial bout, possibly to maintain muscle function during localized mechanical fatigue. However, this does not reflect a strategy to confer protection during the repeated bout by activating undamaged/non‐fatigued muscle areas.