As a whole and across the world, scientists are examining to an unbelievable extent the major factors that direct, begin and sustain the building of muscle protein. On the exercise side, heavy resistance training that incorporates heavy weights, high volume and lots of muscle involved will most certainly do the trick from a muscle building perspective. In other words, if your idea of workout to build muscle is 20 min on an elliptical followed by a 15-20 minute circuit of weight exercise, you won't see results. Performing a bunch of curls or hitting just the muscle groups you see in the mirror won't get it done either. The "visible body part workout" as we call it won't hack it if you really want to pack on muscle. Think squats, deadlift, leg press, barbell chest and back exercises.
On the nutrition side, a number of factors are important. For starters, optimal calories is key. Building muscle not only requires a great big influx of energy (calories) to complete the workouts, but the cellular process itself requires a good bit of energy as well. In other words, don't focus entirely on protein intake, but instead focus on providing an excellent balance of carbs, fat and protein. THEN, you have earned the right to specifically on indivdidual nutrients.
At this point, it has become clear that providing your body with adequate amounts of leucine is important. In fact, many scientists feel this factor is THE most important factor. Certainly, studies have shown that when leucine is provided the rates and extent to which muscle protein synthesis begins and occurs is dependent upon leucine delivery.
For example, research from the University of Illinois examined the impact of a meal containing four grams of leucine (Norton, Layman et al. 2009). In response to the leucine ingestion, assessments were made regarding the time course of changes in muscle protein synthesis as well as the stimulation of key proteins association with the translation of muscle proteins. Blood levels of leucine increased after approximately 45 minutes after ingestion and remained elevated for up to three hours after the meal was consumed. Peak values of leucine, however, occurred after 45 to 90 minutes after ingestion. Most importantly, when blood levels of leucine were elevated, they correlated with the stimulation of key proteins such as ribosomal protein p70 S6 kinase, eukaryotic initiation factor 4E binding protein 1 and overall muscle protein synthesis. Even greater support was provided with a second study by this group that compared meals containing different amounts of whey and wheat protein. Clearly, augmenting your supplementation regimen with a leucine-rich BCAA product such as ProSource's Mega BCAA can help you get the physique results you might not be seeing.
Norton, L. E., D. K. Layman, P. Bunpo, T. G. Anthony, D. V. Brana and P. J. Garlick (2009). "The leucine content of a complete meal directs peak activation but not duration of skeletal muscle protein synthesis and mammalian target of rapamycin signaling in rats." J Nutr 139(6): 1103-1109.