This is a pretty legitimate question. Unfortunately there is no true answer. Only speculation, trial and error, a little bro-science, some real science, and a lot of arguing.
This was posted as a weekly tip on one of my frequented Facebook pages and it almost immediately received some heated responses. Some slightly agreed but had their own input. Others didn't agree and specified why. Others just didn't agree at all and were very colorful with their opinions.
The advice broke down like this;
Train 3 days a week for beginners.
4 days minimum for optimum weight training.
2 days a week for maintenance.
I can buy that. But there were many that didn't. Mostly citing their own experiences. Which is fine. But that doesn't hold up well to those that have trained many a athlete or client and have seen what works on a grand scale.
Heres essentially my 2 cents. Ive been doing this for a while so take it for what its worth. Ill start with one of my favorite quotes- "If you want to do something well then do it everyday." Dan John said that. And it holds especially true to sport training but this tip only addressed weight training.
Before I say anything about this it really needs to be understood what else if anything is the client doing. Also training age and strength levels are a huge part. So that plays into my response quite a bit.
Strength levels have a massive impact on training volume
and intensity due to the resources required to perform work with heavier
loads. I.e. one of my athletes is a near 600lb squatter. 80% for him is
massively different than the majority who are about 400lbs or less. So
trying to train regularly in that range takes some extra considerations.
Which throws the challenge that training him as he was any other
athlete could and likely will be detrimental. Not to knock on the girls
but their strength levels are much lower but this means their training
loads are lighter and through the years Ive noticed their capacity is
relatively higher than the guys.All that equals to the girls actually
getting a higher volume of work. But that is usually a case by case
basis. So take that for what its worth.
Training age is also a consideration. With younger athletes and athletes that have a young training age i.e. they have just recently started training despite actual age. In my experience younger athletes respond well to constant work depending on intensity. Repetition is key. High volume sets that don't necessarily need to be high intensity. This is especially true when motor patterns are the issue. A great example is some athlete I have that have the 'baby huey complex'. They're just too damn big and never bothered to build the muscle systems to handle their frame at such a young age. This is usually accompanied by a slouching posture, horrible flexibility, and poor motor movements. With these guys I would make them do the same warmup every day and then before even lifting or training perform certain patterns (overhead squats were pretty common) before EVERY SINGLE workout. They hated it but the results were outstanding. Also, to go back to training day volume, we trained a minimum 5 days a week. So if you are working with a client/athlete with, say, poor hip movement and flexibility make them perform specific exercises on their own regularly and test them during their sessions. This is in a scenario if you only see this particular client/athlete once or twice a week.
Type of training. I've spoken with many powerlifters who favor a once to twice a week approach to max effort training. I.e. lifting to near maximal capability or 100%. Thats per lift. In other words they may have a heavy bench day and another day a heavy squat day. Then add in 2-3 extra days of dynamic or speed work. Olympic lifters on the other hand I have been hard pressed to find any that didn't train 5+ times a week in their lifts and above all else, squatting. For sports the workload in the gym drops to 2-4 days a week depending on the event. But it's still no where near what I dedicated lifter or bodybuilder may put in. Obviously they are spending more time practicing their craft than worrying about how much weight they can move.
Personally my amount of training days in the weight room depend on what time of the year it is. Off-season I'll grind out up to 7 days a week and throw in some double sessions. Pre-season that drops to about 4-6 days. In-season we're looking at 2 to 3. Maybe 1 depending how beat up I am from the previous game. Thats rugby season. Track season I find even with high volume throwing I can still get 4-6 in with no real issues in regards to recovery or over training. Mind you I've been training a long time. Almost 18yrs now. I'm also not particularly strong for my size. But I'm running into the issue of age. Things don't heal as quick as they used to. Getting older is a bitch.
So after all that then how many days should you in fact train weekly? Mostly I believe that is up to the individual. It really can be a case by case basis since everyone handles their training workload differently.
Need help? My advice is 1-2 days a week will help maintain. This is helpful during a grueling season or if time is at a premium so efforts are directed towards training elsewhere. 3 days is likely the minimum I would recommend for building up. Whether strength or otherwise. I might agree with the 4 day plan but truthfully I prefer the 5 or 6 day split to really build up quickly. For newbies to help enforce motor recruitment I don't really follow the notion that 3 days is best. We're trying to build some good habits and 3-5 hours a week is far from optimum.