If you have read PTP, then you have your answer as to why such a phenomenon occurs, ie. volume and working to failure. Personally, I have found that my musculature has become more hard and compact. More definition too, without altering my eating. Once I began cycling in RKC, I have noticed hypertrophy in my back, shoulders, glutes and traps because of the way my clothes have fit. My girlfriend and family have told me that my body has changed. Tighter and more "streamlined". The muscle I have gained in the areas listed are not visible in clothes. At a recent doctors visit, my weight has actually increased, despite a rigorous job and now including running in the workout mix. I can only attribute that gain in weight to PTP and RKC cycles. I do no auxillary exercises and have not changed eating habits. I am still gaining strength. More muscle density perhaps?
Read PTP. Follow PTP. And you'll be a believer, Comrade. My strength has sky-rocketed - yet I haven't put on an ounce of weight. My muscular definition has improved tremendously - the muscle gained from PTP is solid, dense, most of all, functional - no, not the kinda "fluff" you get from those health-and-fitness mag workouts. As Pavel said, your physique will be built along the lines of the statue of Hercules - broad shoulders with just hint of pecs. Back muscles standing out in bold relief. Wiry arms, rugged forearm. A cut-up midsection and strong legs - without a hint of Squat-induced chafing. Ah, the result of PTP and RKC. Steel-cabled tendons and ligaments. More or less a wiry and "hard" physique. Don't worry if you still can't grasp the concepts of PTP - your not alone. I'm not sure if it's just me or if it's 'cos I'm just plain dumb, but I took quite some time to grasp the concepts and theories of PTP. Hope this helps. Power to you - Kian.
Don't forget variables like density--funny story about my father
Remember that your training methods have a profound effect on whether you develop muscles which are small & hard, or big & soft. My father, who was a boxer & wrestler in his youth, was once challenged at a beach by a bodybuilder who said, "I'm so strong, I bet I can throw you right into the sea." My father was a small man, 5'6" and 145 lbs, but his muscles were like stone. The two combatants locked up, and my father dug his thumb into the BB's bicep, which was so soft that the thumb dug right in. The BB let out a howl & started hopping around, clutching his wounded arm with his other hand. (As it turned out, nothing was seriously damaged except his pride).
Another case-in-point is my friend John from high school who was always small & thin, but unnaturally strong. (If he'd taken up lifting instead of smoking, I bet he'd have been famous by now--maybe even olympic material).
The point is, strength-density (the abount of force you can develop per unit volume) varies wildly from person to person, and is probably the result of many factors (genetics in John's case, training methods in my father's case). When Pavel says you won't gain muscle, I'm sure what he means is you won't get visibly larger. I've been doing snatches and c&j's for a measly month, and I can already feel my mucles getting harder.
Gaining strength without size is a function of neurological improvments and volume. PTP and related powerlifting programs use heavy weights but reps between 2-5 (not to failure) and few sets, but frequent training.
The HIT programs use failure and higher reps and an infrequent training schedule. This is why soreness is continuous. Your body rests long enough to be damaged again by the lift. Training the same lift more frequently and with the above PTP guidlines will virtually eliminate soreness and provide strength.
Also read in Power to the People the difference between sarcoplasmic hypertrophy and myofibril hypertrophy.
Myofibril hypertrophy is the way to go!!
Hope this answers the question.