Electromyographic (EMG) and torque changes in triceps surae following repeated submaximal eccentric contractions

• Published in: Journal of science and medicine in sport Vol. 5; no. 4; p. 110
• Main Authors: Nottle, C, Sacco, P
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2002
• ISSN: 1440-2440; 1878-1861
• DOI: 10.1016/S1440-2440(02)80236-5

Although eccentric exercise is known to result in delayed-onset muscle soreness, muscle damage and strength loss, its impact on EMG activity is less clear. Voluntary EMG and compound muscle action potential (M-wave) responses were studied in twelve subjects (age 28.2 plus or minus 2.4 years) following 60-minutes of backward downhill walking (1.5m/hr at -15%) leading with the left leg (exercised limb). Pre- and post-walk (0.5, 24, 48, 72 and 96 hours) responses for maximal voluntary EMG and M-wave of soleus (sEMG, sM-wave) and gastrocnemius (gEMG, gM-wave), isometric maximal voluntary plantarflexion (VT) and stimulated peak twitch (T sub(0)) torque were examined for both limbs. For the exercised limb, a repeated measures ANOVA with simple (to baseline) comparisons revealed significant (p<0.05) decreases in T sub(0) at 0.5 hours, VT at 0.5-72 hours, sEMG and gEMG at 48 hours, and increases for sEMG and gEMG at 0.5 hours post walk. No significant differences were recorded for sM- or gM-wave for either limb, or any variable of the non-exercised limb post walk. Since M-wave responses were unaffected by eccentric exercise, strength losses were a result of changes within the exercised muscles, while the EMG changes observed reflect alterations in the pattern of muscle activation.