Resistance Exercise Biology
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Resistance Exercise Biology Manipulation of Resistance Exercise Programme Variables Determines the Responses of Cellular and Molecular Signalling Pathways Barry A. Spiering, William J. Kraemer, Jeffrey M. Anderson, Lawrence E. Armstrong, Bradley C. Nindl, Jeff S. Volek and Carl M. Maresh Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, Connecticut, USA
Abstract
Recent advances in molecular biology have elucidated some of the mechanisms that regulate skeletal muscle growth. Logically, muscle physiologists have applied these innovations to the study of resistance exercise (RE), as RE represents the most potent natural stimulus for growth in adult skeletal muscle. However, as this molecular-based line of research progresses to investigations in humans, scientists must appreciate the fundamental principles of RE to effectively design such experiments. Therefore, we present herein an updated paradigm of RE biology that integrates fundamental RE principles with the current knowledge of muscle cellular and molecular signalling. RE invokes a sequential cascade consisting of: (i) muscle activation; (ii) signalling events arising from mechanical deformation of muscle fibres, hormones, and immune/inflammatory responses; (iii) protein synthesis due to increased transcription and translation; and (iv) muscle fibre hypertrophy. In this paradigm, RE is considered an ‘upstream’ signal that determines specific downstream events. Therefore, manipulation of the acute RE programme variables (i.e. exercise choice, load, volume, rest period lengths, and exercise order) alters the unique ‘fingerprint’ of the RE stimulus and subsequently modifies the downstream cellular and molecular responses.
Recent advances in molecular biology have elucidated some of the mechanisms that regulate muscle growth. This progress has opened many avenues in the study of resistance exercise (RE)induced hypertrophy and enhanced understanding of this complex phenomenon. However, as this line of research progresses to in vivo RE models, investigators must not overlook the fundamental principles of RE. Without an appropriate RE stimulus, downstream signalling leading to muscle growth will be suboptimal. Therefore, the purpose of this article is to acquaint the reader with the fundamental princi-
ples of RE and place this information in context of cellular and molecular events. Our intent is that this conceptual paradigm (figure 1) will bridge the gap between molecular biology and RE theory to foster future research into the mechanisms of RE-induced muscle growth. 1. Cascade of Events Induced by Resistance Exercise RE-induced muscle growth is a complex phenomenon that depends on numerous physiological systems and signalling pathways. Muscle growth
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a Upstream
Non-modifiable factors (e.g. genotype, age, gender)
Modifiable factors (e.g. exercise, nutrition, training status)
mechanical deformation of muscle fibres, hormones,
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