How often can you train a bodypart, muscle group or movement pattern?
Well that depends on quite a few different factors. How long have you been training? What are you training for? How strong are you? How is your recovery ability? Are you healthy or injured? What other physical activities do you engage in? What have you been doing in your workouts lately?
Let's address each of those and show why they are so important in determining this.
How long have you been training?
If you are a beginner you will always do full body workouts three days per week, no questions asked. If you are an intermediate you may switch to upper/lower splits and train four days per week or still three days, just spreading your two upper and two lower workouts over 9 days instead of 7. If you are advanced you may stick with this plan or perhaps do two upper and one lower workout per week. Or maybe you may do a pushing workout, a lower body workout and a pushing workout, or some variation of that.
What are you training for?
If it's mass, full body workouts work great. Then again so are upper/lower splits and even bodypart splits. If it's fat loss the usual inclination is to do full body workouts with exercises that burn the most calories. But this approach only works for a short time and is often flawed. The reason? If you are trying to lose fat, you are probably doing intervals and/or steady state cardio a few days per week. Add three days of squatting and lunging on top of another 3-4 days of riding the bike or sprinting and your knees will be screaming in no time.
I think the full body workouts are great to kick start a fat loss workout for beginners or intermediates and even certain advanced guys but eventually, and this may only take 3-4 weeks to happen, your knees will be shot. Unless, of course you are doing your intervals and weight training on the same day. Then you have a little longer to recover but the sheer volume is still the same and will lead to breakdown sooner or later. One option is to alternate one month periods of full body workouts with splits in the quest to uncover your abs.
How strong are you?
If you are very strong, and by that I mean strong for what your body can handle naturally, full body workouts are not really an option. If you can bench press over 300 pounds and squat over 400, there is no way it is healthy or smart to press or squat more than twice per week, for any length of time. Maybe you can do it and make great progress, but only for short periods of time. I do it on occasion when I am coming back from a layoff or as a change of pace but you simply can not EVER do this year round. Actually that is a statement for all lifters, beginners to advanced; you can not do full body workouts year round.
How is your recovery ability?
If your muscles ache and joints hurt after training you may need less frequency. Maybe you recovery incredibly well. Then you might need more.
Are you healthy or injured?
If you are healthy you can get away with pressing or squatting more frequently. But what if you are forty and have been training for over twenty years and your shoulders feel terrible. Guess what my friend? You're doing bodypart splits. You almost have no choice. Pressing twice a week is tough on healthy shoulders if you are strong and have a lot of years under your belt. But on bum shoulders, it's a nightmare. In a situation like this you would have to do one of the following two options:
Monday- Chest & Biceps
Wednesday- Legs, Abs, Calves
Friday- Back & Triceps
If your shoulders are really smoked and you need to relegate all shoulder irritation to just one day you may have to do chest and back on Monday and just biceps and triceps on Friday. That would give the shoulder more time to rest each week.
What other physical activities do you engage in?
If you play a sport or run sprints a few days a week, you probably can't recover from more than one lower body workout every 5-7 days. Now again, if you are a weak beginner you probably can. If you are an intermediate you would probably do best on 5 days and advanced guys would do better on 7, sometimes going heavy every 14.
What have you been doing in your workouts lately?
Usually the best thing to do in your next program is the opposite of what you have been doing for the last few months. I know this isn't the most scientific approach but in many cases it happens to be the truth.
As you can see, there is no cut and dried answer when it comes to determining the optimal training frequency or split. No split is optimal all the time. The best split is the one that addresses all of the concerns addressed above and even that will need to be changed eventually.
Ask yourself those questions and plan accordingly. Remember, failing to plan is planning to fail.