What you call mass gaining is called hypertrophy (hy-PER-truh-fee) in sports science literature.

Broadly speaking there are two types of hypertrophy you can develop: athletic (sport-specific) hypertrophy and bodybuilding hypertrophy. Both make your muscles visibly bigger. You see athletic hypertrophy in elite American football players, MMA athletes, powerlifters, track sprinters, and Olympic weightlifters, to name just a few sports. Athletic hypertrophy increases muscle cross section size, which in turn increases your capacity to generate force. Bodybuilding hypertrophy makes you look even bigger, but at the cost of speed and capacity to exert force - you will be less athletic. However, no one denies that Ahnold looked great back in the day.

Here is Bompa's general prescription for athletic hypertrophy in chapter 12 of Periodization Training in Sport (2015):

> ... training for sport-specific hypertrophy requires heavy loads with minimal rest and high number of sets to increase the density (thickness) of, and amount of protein in, the prime movers. This way, hypertrophy training for sports is long lasting because the increase in muscle size is based on the increase in strength.

That means lifting a weight eight to fourteen times exhaustively (i.e., a fifteenth rep would be impossible), taking a very short break, and then repeating that set to exhaustion. It's psychologically taxing and can be dangerous (Dorian Yates worked out only 45 minutes a day, three times a week, but they were extremely taxing workouts and he freely admits using anabolic steroids to do this). Before really taxing yourself, master the lifting techniques and build up core strength (Stuart McGill) and flexibility. Endurance work also prepares you by improving your ability to recover between sets.

Bompa goes on to describe two phases of hypertrophy training in order to simplify program design. The first "uses various bodybuilding techniques to optimize muscle exhaustion and growth", and the second "refers to sport-specific hypertrophy", which depends on the activity you want the larger muscles for.

Athletic hypertrophy training should be restricted to less than two macrocycles a year, or less than ten weeks total. The rest of the year should be spent training in specific sports or improving your general physical preparedness. Generally a year-long or biannual training period starts with prehab/rehab/general physical preparedness, moves on to hypertrophy, moves from there on to maximum strength training, and finishes with the bulk of the athlete's time spent doing specialized strength training (for power, power-endurance, or muscular endurance of short, medium, or long duration) and sport-specific drills.

All this muscular training is yin to the yang of energy systems training, which is trained concurrently and has its own set of prescriptions, depending on what physiological adaptations you desire.

Note that athletic hypertrophy does not make you very strong - you need maximum strength training for that effect, which has a different prescription. See in particular Bompa, Zatsiorsky, or Siff for advice about maximum strength training.

As for protein, the Academy of Nutrition and Dietetics (formerly the American Dietetic Association), the American College of Sports Medicine, and Dieticians of Canada have for years submitted a joint position paper on nutrition for sports that recommended a daily consumption of no more than 1.5 grams protein per kilogram of body mass for weightlifters. Bompa cites other sources who indicate as much as 2.0 grams protein per kilogram body mass can benefit some athletes, but that is not the consensus position.