Building Muscle: Meshing Science with Practice
Although questions about building muscles still outnumber answers, scientists are gradually learning more about how changes in muscle mass and functional capacity take place.
Building muscles is obviously something of great interest to athletes and all those who help athletes attempt to reach their maximal performance potential. It has been known for centuries that progressively overloading muscle tissue causes it to increase its functional capacity, strength, and often – but not always – its mass. Yet some people increase strength and mass much faster than others, an observation of great practical and scientific interest. What differences in physiology or biochemistry allow some people to adapt quickly? Can these biological advantages be enjoyed by other athletes through training, nutrition, and dietary supplements? What combination of training intensity, duration, and type adds strength and mass most effectively? What are the signaling pathways within muscle cells that promote hypertrophy and strength gain in response to strength training?
Although questions about building muscles still outnumber answers, scientists are gradually learning more about how changes in muscle mass and functional capacity take place. The picture that is emerging is both complex from a scientific perspective and helpful from a practical standpoint. To understand the complexity, it is important to keep in mind that regardless of the sport, athletes are exposed to a variety of different types of training, including endurance/aerobic training, sprint/anaerobic training, strength training, and flexibility training. In other words, athletes are exposed to a variety of different types of training stimuli, all of which provoke hundreds, if not thousands, of different signals within the body. These signals involve virtually every physiological system: neural, hormonal, cardiovascular, and immune systems in addition to cellular signals in muscles, tendons, cartilage, blood vessels, elastic tissue surrounding muscle, and satellite cells adjacent to muscle cells.
Hundreds of genes and proteins are involved in the hypertrophy of muscle cells, making it highly unlikely that any one pathway can account for the increase in muscle mass and force production that accompanies strength training. An increase in the cross-sectional area of a single muscle cell requires substantial changes across three categories of intracellular proteins: contractile proteins (e.g., actin, myosin, and their many protein constituents), structural proteins (e.g., titin, dystrophin, integrins, and others too numerous to mention), and regulatory proteins (e.g., protein kinases, transcription/translation factors, calcium-trafficking proteins, and many others.)
While the complexity of muscle hypertrophy may be overwhelming, the practical off- shoot is that overloading muscles during training sparks a wide cascade of signals not only within muscle cells but throughout the body that coordinate to increase the number of sarcomeres in parallel (sarcomeres being the smallest contractile units within muscle cells.) Consuming high-quality protein soon after strength training helps accelerate the gain in muscle mass by stimulating muscle protein synthesis and prolonging the duration of net positive protein balance. In some people, ingesting creatine augments muscle hypertrophy, perhaps by increasing the activation of muscle satellite cells, an essential element in how muscle cells hypertrophy.
Emerging research will undoubtedly shed light on how strength training programs can be optimized to provoke the greatest responses in strength and mass. For example, how much rest between sets of strength exercises will optimize strength gains? Is one-minute rest sufficient or does a longer rest period provide a greater opportunity to maximize the signals associated with building muscle? What is the optimal combination of sets and reps to build strength? Is that different from the combination required to maximize mass? Should strength-training exercise purposefully damage muscle tissue to stimulate the proliferation and integration of satellite cells? If so, how much damage is enough? How can strength training be designed to enhance the well-known neural contributions to rapid strength gain? How can diet and supplements best contribute to gains in strength and mass?
These and other important questions will eventually be answered, although it will take many years to do so. Coaches and athletes are constantly refining their training techniques and scientists continue to study how muscles respond to different types of training. Educational efforts that combine these common interests will help scientists refine their experimental approaches and help sports health practitioners and athletes alter their training and nutrition practices based upon emerging science. That is the goal of the conference, Building Muscle: Challenging Current Dogma, to be held in Chicago during the spring of 2010.
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