One of the first and most common questions I get asked by new clients and athletes is "How often should I train?". Sometimes it's phrased a little differently; "If I can only train X times a week what should I do?" To save us both some time I'll set out my answer here, but spoiler alert - you may not like my advice! While reading, keep in mind your training goals, your sport and your lifestyle. All 3 will influence which path you take and which answer applies most to you.
How often should you train?
As always, my get out of jail card is - IT DEPENDS. People, goals, needs and wants are so individual that to give one definitive answer would be lying to you. Instead, I'll try to encompass as many people and training goals as possible within the following fictional scenarios. Hopefully you can identify with one or more of them and take what is useful to your own situation...
(*If you're already an elite or pro athlete and you don't do any training outside of your sport, well done! You've got by on raw talent and genetics. That may not last so I'd get to work identifying gaps and fill them quick!*)
You have to know what you want to train before you can start. What areas are you lacking? How do you stack up against team mates and the competition?
The time poor amateur/sub-elite athlete that;
A) needs to get stronger
B) needs to be faster
C) is coming back from injury
A) research shows that in order to get stronger, you need to perform exercises that require a lot of load relative to your maximum ability. That is to say that you should use loads that you can only do for around 3-6 repetitions, resting ~3mins between each set. You should do somewhere between 8 and 14 sets per muscle group (not of each exercise!) and train that movement of muscle groups 2-3 times per week (Rhea et al., 2003).
In reality, your history with strength training will dictate whether these fixed guidelines work. For someone totally new to resistance training, you can probably make just as much progress doing less work - 3-6reps x 5-8 sets per muscle group/movement, resting 2-3mins between sets and doing only 1-2 sessions per week.
If you've already been training properly for a while, you might need the higher volume (reps x sets x exercises) AND the higher frequency (number of sessions per week). Essentially, the more advanced you are in regards to strength training, the more training it will take to get you stronger.
When I begin coaching an athlete that is weak (relative to their past or to the standards of their sport) the first question I need answering is; what is your strength training history. My basic guidelines are: under 6 months? one session per week is ok. Between 6 months and 2 years? You'll do better on 2 strength sessions per week. Over 2 years of organised strength training? 3-4 sessions per week will likely give you the best return.
Want to see what those training weeks might look like? Read this post.
B) Max strength and max speed training are different ends of the same continuum (see diagram). Training for power and speed requires sub-maximal loads to be moved fast. This means using a load that you are capable of doing multiple reps with, but only doing a few reps really fast (put simply!). For example you might only use your body weight to perform box jumps. You're capable of doing quite a lot of these but if you only do a few of them really fast and explosively you will get better at expressing force against the ground rapidly.
You're intention to move the weight (or yourself) very fast is what enhances your brain/muscle connection and makes you quicker in that movement. Due to this higher demand on the central nervous system (CNS) the speed and power sessions are often more fatiguing than endurance sessions for example and so require a lot of rest before another session of the same work. Initially you may only need one speed session per week but as you begin to adapt to the stimulus and it's fatiguing effects, you can likely add another.
Some sports require more high end speed than others so just being faster isn't always the only thing you need to train. In most cases you'll need to work a speed session around your strength session(s) and your sport training.
To be frank, I rarely train speed and power in an athlete that hasn't performed some strength training first. Strength (your ability to produce force), largely impacts you ability to produce force quickly - your power.
Once into a speed/power phase however, the decision for training frequency is influenced by how many other qualities you still need to train. For example, when working with a track cyclist I will typically use one strength-speed session per week in the build up to the racing season but also maintain one strength session. In season that may drop to one session per week that is equally split between strength and more speed-strength. In a sport such as karate where max speed is even more of a priority I may use 2 speed sessions per week. At this point the athletes are still doing 3-5 sport skill training sessions per week too. The sessions themselves will look very different. In only very specific speed based sports might the frequency of training sessions exceed this - possibly sprinting for example.
To see what a speed session for karate athletes looks like, read THIS post.
C) Coming back from injury is tough. Time away from your sport often means little or no training was done and can mean that every single fitness quality has suffered. If you can see this as an opportunity to get better, you'll return to full capacity far quicker.
Just because you're not in pain anymore, doesn't mean you are out of the woods yet. Many tissues can take months, if not years, to totally remodel and be back to 100%. Also, you shouldn't ignore that getting injured likely means that something was wrong in the first place - whether you were too weak, too un-fit or too slow or maybe you just have bio-mechanical flaws that you should fix.
I highly recommend identifying the reason(s) you got injured and figuring out which camp that falls into - strength, speed, 'fitness' or poor bio-mechanics/motor control etc. This will now become your main priority - ensuring you don't repeat the mistakes of the past. That will, in turn, give you some insight into how you need to train.
Poor bio-mechanics and or poor motor control - by which I mean specifically a misalignment of joints causing undesirable force vectors (you are a bit wonky and it makes things hurty). This could be statically (think knock-knees - passive valgus) or during motion (knee's drop in only when moving - active valgus). This kind of thing will take A LOT of frequency to fix. Daily or even twice daily working on consciously altering the alignment or motion of joints. This kind of thing is where you - the athlete - are given homework by a physio or coach. Stuff that doesn't require a lot of loading but hundreds of repetitions over weeks and months to re-train the brain and hold limbs and joints in the correct place. Typically you could do this stuff as part of every warm up for every training session, or as a totally separate session each morning and/or evening. It can seem monotonous and dull but so is being injured.
Strength - see point A
Speed - see point B
'Fitness' - yes, it's in quotation marks. Fitness doesn't really mean anything
specific until we give it a technical and physiological definition. There are many aspects to 'fitness' but I'll focus on aerobic and anaerobic fitness here for now.
Aerobic fitness refers to the slowest form of energy production, that requires oxygen to occur and thus takes longer to form ATP for energy and movement. This 'slowness' means we aren't able to produce as much force as quickly as the anaerobic system which is a quicker and shorter pathway. For most sports we need a bit of both. Aerobic has had a bad rep for a while but undeservedly so. The aerobic qualities we need allow us to train harder and recover better when using the anaerobic pathways and so shouldn't be totally neglected. The aerobic system is pretty easy to develop and improvements last quite a while.
Anaerobic energy production doesn't last as long each time we use it or exhaust it. It's also more sensitive to change so we must train it a bit more frequently than the aerobic. Any sprint efforts lasting between 6 and 45seconds will develop this system, as will longer duration resistance training efforts - think of a set of squats lasting 45-60sec!
With my clients and athletes that need more aerobic fitness I'll plan it as a separate session - one which they don't need me to be present for. It will typically still use intervals of longer durations and the very occasional steady state jog/cycle/swim.
If an athlete needs more anaerobic conditioning it could fit into 2 camps. Power capacity; the ability to produce high levels of force and speed repeatedly (think boxing/karate/rugby) in which case modified strongman training, ball throws/slams, jumps, battle ropes or barbell complexes would be useful. It could be more energy system based using mid-range intervals of 30-40sec where a watt bike or rowing machine is ideal.
So what's the answer? How often should you do S&C training???
If you're just starting out with resistance and strength training, you can get stronger and better doing only 1 session per week. Unfortunately it won't be long until you need more frequent stimulus and a bigger dose of the heavy stuff.
For most people in sub-elite sport, you could get away with sacrificing a little time in your sport for a bit of strength training. Especially if your sport training isn't really skill focused and is more just habit. Your sport is priority, yes, but if you've identified gaps holding your performance back, give it the time it needs to change. In a really general sense, I suggest 2 sessions of S&C per week to the average amateur athlete. If your goal is strength, then the programmes need to reflect that. Strength should be the bulk of the work in each session but you could also finish a session with anaerobic conditioning work in small volumes.
If power and speed are your weak areas, dedicating a session per week to this is really important. Do it when you're at your freshest and focus on the speed of execution not how much you're lifting. Even then you could end each session with some strength work if you want to maintain it, or give it a separate session all together if it needs it.
For fitness, whether aerobic or anaerobic, ask yourself first "am I getting this stimulus in my sport?" If not, by all means add another session in. If you are, maybe you really need strength work more than you think...
When returning from injury, your main focus has to be NOT GETTING INJURED AGAIN! Fix what's not optimal. If you move like Bambi on ice - frequency of focused motor control training could be your path to safety (e.g. landing or hopping drills, or scapular motion exercises). Don't forget that once you've improved how you move, you HAVE to get strong there too in order to stay injury free.
Going back to my original answer - IT DEPENDS. Not all training is the same, and not all results last as long as the other. This is where knowing about how to plan and periodise phases of training comes into its own. You may require 3 sessions per week out of season but when competing or tapering only 1 or 2. Your lifestyle and the stress levels it brings will all influence how well you can recover from training too. A more hectic lifestyle may mean 3 sessions per week is unrealistic or even detrimental to performance. If you're a pro and the only things you do are eat, sleep, train (repeat) then you can likely manage 4-5 training sessions each week as well as your sports training.
Be sensible, be realistic, and try things out. Not getting stronger on one well planned strength session per week? Try two. Not getting faster even though you're doing a great speed session every week? Are you recovering? Spending too much time on aerobic fitness? Or maybe you actually need higher strength levels before you apply them quickly. Without assessing, you're just guessing.
Rhea, M. R., Alvar, B. A., Burkett, L. N., & Ball, S. D. (2003). A meta-analysis to determine the dose response for strength development. Medicine and science in sports and exercise, 35(3), 456-464.