Damage to skeletal muscle occurs in a number of conditions like muscle rupture or cell necrosis (Cervellin, Comelli, & Lippi, 2010). Resistance exercise-induced skeletal muscle damage is devoid of necrosis (cell-death) and although microscopic in nature, is crucial for muscle hypertrophy (increase in muscle size). The intensity and volume in combination with overload associated with resistance training is responsible for the micro-ruptures in the muscle structure. This leads to muscle adaptation which causes growth and hypertrophy in the long run – giving the individual a muscular look (Howatson & van Someren, 2008).
However, in the short term, resistance training-induced muscle damage is responsible for oedema (fluid accumulation), short-term decrease in muscle strength and soreness. A number of ways to control these short-term ‘side-effects’ of resistance training have been suggested – one of these is supplementing with branched-chain amino acids (BCAAs).
How Does Muscle Damage Cause Hypertrophy?
In general, disruption of muscle structure is said to occur in two stages – primary and secondary (Howatson & van Someren, 2008). Primary damage is thought to occur either in response to metabolic or mechanical stimuli – metabolic damage is due to severe hypoxia (lack of oxygen) to working muscles such as occurs in death of a part of heart muscle due to narrowing of coronary arteries. Mechanical stimuli on the other hand are due to overloading of muscles such as associated with resistance training. This is characterized by breakdown of muscle cell membranes and spilling of muscle proteins into blood plasma. These muscle proteins – creatine kinase (CK), lactate dehydrogenase (LDH), myoglobin and myosin heavy chain (MHC) – are thus used as biochemical markers to judge the degree of muscle disruption as well recovery from an intense workout session (Mathur, Sheel, Road, & Reid, 2010). Furthermore, these markers are also said to be associated with delayed onset muscle soreness (DOMS). Thus, more the muscle damage more is the muscle soreness.
Resistance training associated micro-rupture of this such nature is essential for muscle adaptation, improved muscle protein turnover and hypertrophy (Koh & Pizza, 2009).
The degree of muscle damage is highly influenced by both intensity and volume of training. Intense and higher-volume training sessions cause higher degree of disruption of muscle membranes, increased membrane permeability and higher levels of above mentioned markers in blood. Not surprising then this kind of training is associated with more muscle hypertrophy compared to low or moderate-intensity/volume resistance training sessions (Hurley et al., 1995; Serrao et al., 2003).
What Are Branched-Chain Amino Acids and How Do They Help in Muscle Breakdown?
As we all know, amino acids are building blocks of proteins and that proteins are important in maintaining and building lean muscle mass. Of the 20 essential amino acids however, an elite group of amino acids called the branched-chain amino acids (BCAAs) – leucine, isoleucine and valine – seem to play a bigger role in both repair and hypertrophy of resistance trained muscles. How they do so is discussed in the following sections.
Effectiveness of Branched-Chain Amino Acids
Researchers have reported that BCCAs are effective in repairing muscle damage associated with resistance training (Nosaka, Sacco, & Mawatari, 2006; Shimomura et al., 2006).
Actions by which BCCAs have an anabolic effect are:
• Promoting muscle sacromerogenesis – stimulation of protein translation and thereby laying down of new muscle protein – (Nicastro et al., 2011)
• Suppression of oxidation of muscle protein – suppressing breakdown of existing muscle protein (Zanchi, Nicastro, & Lancha, Jr., 2008)
• Increased BCCA oxidation – providing a crucial source of energy for improved muscle contraction (Harris, Joshi, Jeoung, & Obayashi, 2005; Hutson, Sweatt, & Lanoue, 2005)
Furthermore, supplementation with BCAAs also protects against future muscle damage and plays an indirect yet significant role in hypertrophy of muscles (Zanchi & Lancha, Jr., 2008). Interestingly enough, these changes in muscle morphology occur in spite of the fact that BCCAs do not seem to increase muscle strength (Sharp & Pearson, 2010; da Luz, Nicastro, Zanchi, Chaves, & Lancha, Jr., 2011).
Although little is known about the benefits that BCCAs afford in increasing muscle function or strength, it is a well known fact that decrease in muscle soreness post-workout enables the individual to go in for another high quality workout. This is what has been termed as the ‘Repeat Bout Effect’.
To conclude, BCCAs provide a prophylactic effect against the side-effects of micro-rupture of muscle due to resistance training and therefore helps subsequent workouts to be better – this in long term will ensure deposition of new muscle protein and bigger muscles!
In a nutshell, if you’ve been hitting the weights regularly but not seeing much muscle gain, BCCAs may be the biggest missing link in your nutrition strategy.
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