Micro Tears and Hypertrophy – Separating Fact from Fiction
The fitness industry is filled with myths and misconceptions, and one that has persisted for years is the belief that micro tears in muscles are the driving force behind muscle growth (hypertrophy). Many gym goers and even some fitness professionals have accepted this idea as gospel, attributing the soreness experienced after a workout to microscopic tears in muscle fibres.
Understanding Muscle Hypertrophy:
Muscle hypertrophy, the process of muscle growth, is a complex physiological response to different forms of mechanical stress or tension (i.e. resistance training). The two primary forms of hypertrophy are myofibrillar hypertrophy, which involves an increase in the number and size of muscle myofibrils, and sarcoplasmic hypertrophy, which involves an increase in the volume of the fluid and non-contractile elements within the muscle fibre or cell.
Quick anatomy:
Muscles are made up of long muscle fibres or cells. Each fibre is made up of bundles of myofibrils and these myofibrils contain the contractile units (sarcomeres) which allow muscles to lengthen, shorten and importantly exert force. In myofibrillar hypertrophy, myofibrils split and then grow, giving us more contractile units and the ability to exert greater force. So, while the number of myofibrils can vary, the number of muscles fibres remains relatively constant.
The Myth of Micro Tears:
The micro tears hypothesis posits that during intense resistance training, muscle fibres experience tiny tears or damage, triggering the body to repair and rebuild these fibres, leading to muscle growth.
The first problem with this theory is that there is no evidence to suggest mechanical tension causes micro tears. Strenuous exercise can cause microscopic muscle damage; however, this is chemically mediated (not ‘tearing’ and a whole topic of its own) and occurs in the days follow exercise. If you say, “well hang on, we’re just splitting hairs between ‘tearing’ and ‘damage’, you still need some form of muscle break down to trigger growth”; then that leads to the second problem. Yes, the body will repair damaged structures, but repair and growth are separate pathways, they share some mediators and elements but they are undoubtedly separate.
So, while it may be true that resistance training can lead to structural damage in muscle fibres, the idea this is the main driver of hypertrophy is at best oversimplified. The body will repair and rebuild damaged structures; however, the theory that this will absolutely lead to hypertrophy has been debunked. In short, the types of stresses which may lead to micro-trauma could also trigger hypertrophy; however, you can equally have muscle growth without damage and damage without muscle growth.
Scientific Perspective:
To support this, research has shown that the relationship between muscle damage and hypertrophy is more nuanced than the micro tears myth suggests. Studies indicate that muscle damage does not consistently correlate with muscle growth. For example, studies have shown that eccentric (lengthening) contractions, which are often associated with increased muscle damage, don't always result in greater hypertrophy compared to concentric (shortening) contractions.
Triggers for hypertrophy:
Several factors contribute to muscle hypertrophy. Key mechanisms include:
Mechanical Tension: This refers to the force exerted on muscle fibres during physical activity. Mechanical tension is considered a primary driver of hypertrophy and occurs during both isotonic and isometric muscle contractions.
Metabolic Stress: The accumulation of metabolites such as lactate during resistance training is postulated as another contributor to muscle growth. Often associated with mechanical tension, metabolic stress triggers anabolic processes that stimulate hypertrophy.
Cellular Signalling: Resistance training activates signalling pathways within muscle cells, including mTOR (mammalian target of rapamycin), which plays a crucial role in protein synthesis and muscle growth.
Conclusion:
While the myth of micro tears being a key trigger of hypertrophy has been pervasive, the scientific understanding of muscle growth is more complex. Muscle damage should perhaps be seen as more of a passenger in the hypertrophic process rather than the driver, with microscopic damage a by-product of strenuous exercise rather than a direct and necessary consequence of the mechanical tension behind hypertrophic responses.
If you are looking to increase muscle mass it is important to remember proper programming, nutrition, and recovery are paramount in achieving your goals. As we continue to learn more about the intricacies of muscle physiology, it's important to remain informed and move beyond fitness myths and fads.
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