Q:

Optimal volume (sets/reps) per week?

After training for about a year now, I am noticing I gained some muscle (not sure how much, but I'd say under 5kg/10lbs). So I would not say I am a beginner, but I'd like to add on at least 5/10lbs of muscle.
I go about 3-4 times per week to the gym, a session for every major muscle group (back, chest, legs and a session for all the rest). So far I am doing about 20 sets per major muscle groups, 8-10 for the smaller groups. 
Recently I stumbled over a bunch of internet resources that suggest maybe going for less volume, and when I googled "optimal number of sets per muscle group per week" I found articles which point to 60-120 reps/week for large muscles and 30-60 reps/week for smaller ones. Considering that my sets are usually 8-12 reps (15-20 sometimes), I am doing around 20*10 = 200 reps/weeks for the major muscles and 8*10=80 reps/week for smaller ones. It looks excessive, but it's about one solid hour of workout where I rest very little (no more than a minute) betweek sets. 
My question is very simple: what is the optimal number of sets/reps per week to maximize muscle gain (knowing that I am taking enough proteins) ? Is there anything on the scientific litterature to indicate or estimate that number ? What's your number from practices and what's your balance of intensity (weight) and volume (set-rep quantity) for that number ?
Thanks.

A:

Optimal is different from people to people and I can hardly find credible scientific literature. They usually extrapolate from couple of hundreds people experiments, questionable training experience (people with sedentary lifestyle can improve a lot just with better eating and suboptimal training), etc. If there would be a one-regimen-fits-all, no coach would be needed.
It doesn't matter what training regimen works for others. Just don't get injured. With a busted knee your squat 1RM is exactly 0 kg.
The rule of thumb is you should
 - train as much and as frequently as possible
 - with good form
 - with high intensity to failure or beyond failure with repeating just
   the easier parts of an exercise. The easy part is usually the
   negative, e.g. when you descend from a pull up, so you step up to a
   stool and just practice the negative
 - add weekly variety to the intensity:volume ratio (I'd recommend to see Juggernaut Method, that one worked for me the best.)
Now, what I noticed the recovery is the key. When you are young, doing reps in a rush, bad form, training frequently can be all ok, but as you get older or collected your first busted joints you realise working in a recovered is more important than working heavy.
Unfortunately there is no generic rule. I know some people who can deadlift 200kg+, but training with isometric exercises (timed static muscle contractions) only. Some people does Heavy Duty HIT with super slow movements and dead strong with low volumes. Some do low weight 10x10 sets… Some of us do 100 pull up every day, but just 10 at a time (e.g. if you work from home), not until failure, so they can train every day. These regimens can all be perfect for some.
If nothing helps, I'd recommend to try the Juggernaut Method, which is a twister variation of 5-3-1. It incorporates hypertrophy training and strength training. There are bunch of videos on Youtube, and the spreadsheet that calculates the whole 16-week “macrocycle” can be handy.

