Review Non-uniform muscle adaptations to eccentric exercise and the implications for training and sport Nosratollah Hedayatpour a , Deborah Falla b,c,⇑ a Department of Physical Education and Sport Sciences, University of Bojnord, Bojnord, Iran b Pain Clinic, Center for Anesthesiology, Emergency and Intensive Care Medicine, University Hospital Göttingen, Göttingen, Germany c Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology (BFNT) Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany article info Article history: Received 20 September 2011 Received in revised form 10 November 2011 Accepted 14 November 2011 Available online xxxx Keywords: Eccentric exercise EMG DOMS Training abstract Due to the variations in morphological and architectural characteristics of fibers within a skeletal muscle, regions of a muscle may be differently affected by eccentric exercise. Although eccentric exercise may be beneficial for increasing muscle mass and can be beneficial for the treatment of tendinopathies, the non- uniform effect of eccentric exercise results in regional muscle damage and as a consequence, non- uniform changes in muscle activation. This regional muscle weakness can contribute to muscle strength imbalances and may potentially alter the load distribution on joint structures, increasing the risk of injury. In this brief review, the non-uniform effects of eccentric exercise are reviewed and their implications for training and sport are considered. Ó 2011 Elsevier Ltd. All rights reserved. Contents 1. Introduction .......................................................................................................... 00 1.1. Non-uniform activation of muscle regions during exercise ............................................................... 00 1.2. Non-uniform muscle adaptations to training .......................................................................... 00 1.3. Non-uniform muscle adaptations to eccentric exercise .................................................................. 00 1.4. Consequences for training and sport ................................................................................. 00 2. Conclusion ........................................................................................................... 00 Acknowledgement ..................................................................................................... 00 References ........................................................................................................... 00 1. Introduction Structural and functional muscle adaptations occur in response to training and the nature of the exercise determines the type of adaptation. For example, an increase in aerobic metabolism and consequently enhanced respiratory capacity occurs in skeletal muscles following long term endurance training (Hamel et al., 1986). On the contrary, heavy resistance exercise increases neural inputs to motor neurons (Semmler et al., 2004) and also induces changes in the ionic membrane permeability of muscle fibers, which in turn stimulates an increase in gene expression and pro- tein synthesis, and the development of cellular hypertrophy of muscle fibers (Cureton et al., 1988; Goldspink et al., 1992; Shoepe et al., 2003). In particular, high load eccentric exercise is commonly used by weight lifters and body-builders to increase muscle size and maximum force capacity. Moreover, many movements in various sports, such as jumping, landing, and abrupt changes of direction, requires eccentric contractions and therefore eccentric exercises are commonly incorporated into training regimes. How- ever, eccentric exercise is also associated with muscle fiber dam- age, pain, reduced fiber excitability and initial muscle weakness (Felici et al., 1997; Fridén and Lieber, 1992; Sbriccoli et al., 2001; Semmler et al., 2007; Hedayatpour et al., 2009), which may delay or inhibit neuromuscular responses at injured sites (Semmler 1050-6411/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jelekin.2011.11.010 ⇑ Corresponding author at: Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology (BFNT) Göttingen, Bernstein Center for Compu- tational Neuroscience, University Medical Center Göttingen, Georg-August Univer- sity, Von-Siebold-Str. 4, 37075 Göttingen, Germany. Tel.: +49 (0) 551 3920109; fax: +49 (0) 551 3920110. E-mail address: deborah.falla@bccn.uni-goettingen.de (D. Falla). Journal of Electromyography and Kinesiology xxx (2011) xxx–xxx Contents lists available at SciVerse ScienceDirect Journal of Electromyography and Kinesiology journal homepage: www.elsevier.com/locate/jelekin Please cite this article in press as: Hedayatpour N, Falla D. Non-uniform muscle adaptations to eccentric exercise and the implications for training and sport. J Electromyogr Kinesiol (2011), doi:10.1016/j.jelekin.2011.11.010