title: Residual force enhancement following shortening is speed-dependent.
abstract: The steady-state isometric force following active muscle shortening or lengthening is smaller (force depression; FD) or greater (residual force enhancement; RFE) than a purely isometric contraction at the corresponding length. The mechanisms underlying these phenomena are not explained within the context of the cross-bridge theory and are rarely studied in concert. Previous studies have shown RFE to be speed-independent. In the present study, we investigated if RFE preceded by active shortening is time-dependent by electrically evoking RFE in the human adductor pollicis muscle. The results shown that a slow stretch following FD fully re-established RFE compared to higher speeds of stretch. The mechanism(s) responsible for the recovery of RFE following a preceding shortening contraction (FD) might be associated with the recovery of cross-bridge based force and/or the re-engagement of a passive structural element (titin). Voluntary interaction with one's environment involves highly coordinated shortening and lengthening muscle contractions. Therefore comprehending these history-dependent muscle properties in the context of movement control is paramount in understanding the behavior of in vivo motor control.
authors: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada.
authors: Rafael
authors: R
authors: Fortuna
authors: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada.|Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, Ontario, Canada.
authors: Geoffrey A
authors: GA
authors: Power
authors: Department of Biomechanics in Sports, Faculty of Sport and Health Sciences, Technische Universität München, Munich, Germany.
authors: Esther
authors: E
authors: Mende
authors: Department of Biomechanics in Sports, Faculty of Sport and Health Sciences, Technische Universität München, Munich, Germany.
authors: Wolfgang
authors: W
authors: Seiberl
authors: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada.
authors: Walter
authors: W
authors: Herzog
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D055595:Mechanical Phenomena; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology*; D055815:Young Adult