Beneficial effects of serial contractions on muscle performance after a brief period of rest

• Published in: European journal of applied physiology Vol. 114; no. 8; pp. 1657 - 1665
• Main Authors: Green, Lara A., Parro, Justin J., Gabriel, David A.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2014; Springer Nature B.V
• Subjects: Adenosine triphosphatase; Adult; Athletic Performance; Biomedical and Life Sciences; Biomedicine; Electromyography; Evoked Potentials, Motor; Exercise; Human Physiology; Humans; Isometric Contraction; Male; Muscle Fatigue; Muscle function; Muscle Strength; Muscle, Skeletal - physiology; Occupational Medicine/Industrial Medicine; Original Article; Rest; Skin Temperature; Sports Medicine; Velocity; Isometric dorsiflexion force; Antagonist co-activation; Tibialis anterior; Surface electromyography; Muscle coordination; Warm-up effect
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-014-2896-8

Purpose The study investigated potential mechanisms underlying the beneficial effects of performing serial contractions for increasing muscle performance. Methods Thirteen men performed maximal isometric dorsiflexion contractions to a limited amount of fatigue. The recovery pattern was monitored over 15 min. Force, surface electromyography (sEMG) of the agonist and antagonist, and skin temperature were observed. Evoked potentials were elicited. Results Force decreased to 206 ± 40 N and recovered to 243 ± 55 N (102 % of initial value). While full recovery is noteworthy, it was not significant ( p  = 0.24). Surface EMG root-mean-square (RMS) amplitude did not fully recover: tibialis anterior (219 ± 46 versus 242 ± 63 μV, 91 %) and soleus (13 ± 5 versus 16 ± 6 μV, 82 %). The result was an 11 % decrease in the co-activation ratio during recovery. Tibialis anterior and soleus mean power frequency (MPF) “over-recovered” to 117 % (144 ± 25 versus 124 ± 27 Hz) and 118 % (80 ± 14 versus 68 ± 11 Hz) of initial value, respectively. Peak rate of force development (RFD) during recovery was 146 % of initial (743 ± 246 versus 509 ± 271 N). Skin temperature increased 0.6 °C over the test session. Potentiation was not present during recovery, as assessed by twitch force. Conclusions The return of force to initial values, rather than a persistent decrement was a result of several mechanisms operating simultaneously. The sEMG data indicate an increase in conduction velocity, while an increase in peak RFD suggests contraction-induced facilitation of ATPase pump activity. However, alterations in muscle coordination were observed as a reduction in antagonist co-activity.