Not all muscle fibres are created equal. Some are made up of slow-twitch fibres that are laced with lots of capillaries to supply them with oxygen, and are mainly used in aerobic, endurance activities such as running.
Other muscles are made up of fast-twitch fibres which have fewer capillaries and convert stored glycogen into glucose to fuel explosive, anaerobic movements such as jumping or lifting heavy weights. It’s these fast-twitch fibres that have the greatest potential for growth, which is why power sportsmen such as sprinters and weightlifters tend to be bulkier than endurance athletes such as marathon runners.
The number of fast-twitch and slow-twitch fibres you have is determined at birth by your genes. This explains why some people pack on muscle easily while others struggle to add weight. But even classic ectomorph (skinny) guys can bulk up with the right training and nutrition – it will just take a bit more work.
The muscle grows when you put sufficient stress on it to create microscopic tears in the muscle fibres which, if you give them sufficient rest and amino acids from protein-rich foods, will heal bigger and stronger than they were before. This process is known as hypertrophy. Once the muscle has healed, it is more resistant to stress, so you need to attack it with bigger weights in order to repeat the damage/repair process that will make it grow again. That’s why you need to subject your muscles to progressive overload or, in other words, keep lifting bigger and bigger weights.
Top 6 exercises for getting bigger pecs
BENCH PRESSES
INCLINE DUMBBELL PRESSES
CABLE CROSSOVERS
DUMBBELL PULLOVERS
INCLINE DUMBBELL FLYES
CHEST ROUTINE
Bench Presses: 3 warm-ups; 3 sets; 8-10 reps
Incline Dumbbell Presses: 1 warm-up; 3 sets; 10-12 reps
Cable Crossovers: 1 warm-up; 3 sets; 10-12 reps
Dumbbell Pullovers: 3 sets; 10-12 reps
Incline Dumbbell Flyes: 3 sets; 6-10 reps