First, I would like to start with "everyone can achieve their different goals with a different method!"
OK, I feel better, its like a disclaimer. NOW!
The old split routine would be the "typical" bodybuilding method of training chest and triceps on International Chest Day (Monday for the newbies). Then moving on to back and biceps, etc, etc. Each body part gets their respective day of the week. In this method, you would only work chest (or anything for that matter) once a week.
For a newbie, that is trying to get used to a routine and needs some structure this method works perfectly and will provide results. If you need proof, look at any bodybuilder that has dedicated themselves to this method. They are living proof this works.
OK, moving on.
I train in unorthodox ways and don't always have strongman implements to use. I have had a day where I was in a hotel, near a machine, and worked a specific muscle group. It is 100% better than just sitting around sulking that you can't do what you usually do.
I get most of my cardio from lifting heavy things and carrying them. Or lifting a little lighter and doing high reps.
I also train more of a full body method, push and pull, than the split. My goals are different though, so it works for me. I also throw in event style training so its another day of work for multiple body parts. Its not usual in a strongman event to have just one muscle group used.
Now, take crossfitters, powerlifters, bodybuilders, strongmen. All are very different with different goals and different methods to get there. But one thing is for certain, the consistency of training is the number one way to succeed.
To get the most out of your routine and the ability to get stronger/better, you need to recover from the training session and do it again. The workouts break the muscle down and the resting builds it back stronger than before. If you do not rest, you are not getting stronger.
Finally, the entire purpose of this article. HOW LONG TO REST! The old split method says 7 days. I would argue for the majority of the population that is TOO LONG!
A body part needs 1 day to recover (just from being worked). Based on how heavy you lift you add time. So add another 24 hours to recovery for every 1000lbs lifted during working sets. WARM-UPs don't count!
So, if you did deadlift Monday and your working sets consisted of 200lbs lifted 5 times for 5 sets; then you would be able to deadlift again on Saturday. But this is just for COMPLETE recovery. Most can be well enough to work again by Thursday. Though you would make this a lighter day since you are not 100% recovered.
This will provide 2 days of work and 5 days of muscle building for this posterior chain in 1 week instead of being fully recovered by Saturday and just sitting around until Monday to do it again.
You are missing opportunities for growth with the split method. Now, if you are lifting SUPER heavy and deadlifting like Eddie Hall, then you may take 2 weeks to recover for another heavy day. The calculations should help you understand where you are in the gains process and how much you can handle. It is by no means the truth for all lifters and everyone's body is different and responds in different ways.
*Please do not start a routine/method without consulting a doctor. This is my opinion on the split method and its rest period when the weights used by the follower is not heavy enough to necessitate a full week recovery. Also you cannot recover properly without a good diet to feed the muscle growth or supplement for your missing pieces in the diet.