QuestionSo when building muscle, is it better to do sit-ups one day and then none the next day to give them a chance to rest and develop properly?
When training, you need to keep in mind that you have two types of muscles: fast-twitch muscles for speed and slow-twitch muscles for endurance. A well-rounded routine will work on both sets.
First, you need to determine which set of muscles you want to develop. You want to select exercises that mimic the movements you use in your sport or activity. Building strong arms isn't going to help a cyclist much, though all areas should not be neglected.
Next, you need to determine a base-line of how much weight to use. The may take several days of experimenting. What you are looking for is a weight that you can lift 12 times in a row in good form, where you are straining a bit on the 12th repetition. If you can't get to 10 repetitions, take some weight off. If getting to 12 is easy, add a bit more weight. You will be making adjustments as you progress.
Next you need to determine the amount of training you desire. An athlete will want to work harder than someone wanting general strength improvement. If there are more areas you want to train than you can reasonably do in a day, split the work out between days, such as biceps and calves one day and abdominal and quadriceps another day. I'm going to assume you have two sets of muscles to train in the following.
Day One (Strength): Your goal is to work your muscles to exhaustion without losing good form. Do a set of 12 repetitions and then move to your next muscle group. When you are done exercising each muscle group, repeat the entire set. If you have the time, do a third set. Don't be surprise that you can't do as many repetitions on the second or third sets.
In strength training, it is possible to do only one set and get the effect needed, but you must get your muscles fully exhausted by the end of the repetitions. Too many people overdo it when they try for only one set and end up with sloppy form and injuries by the end of the repetitions. While breaking the routine up into sets of 12 is a bit longer, it does minimize the potential for injury.
Day Two (Speed and Endurance): Move to your second set of exercises, but this time lighten the load by about 25%. Your goal is to to as many repetitions as you can as quickly as you can, but still keeping good form. This is building your speed and endurance. If you have time, do a second set after all muscles have been exercised to exhaustion.
Since you are not using your first set of muscles, they are getting a light rest.
Day Three (Speed and Endurance): Going back to your first set of exercises, again use the lighter load and do as many repetitions as you can as quickly as you can without losing good form. If you have time, do a second set.
Day Four (Strength): Returning to the second set of exercises, use the same rules as day one.
Day Five (Improvement): Using the first set of exercises, add 10% more weight. Concentrate on keeping good form. Do only one set and don't worry if you don't make it to twelve repetitions.
Rest two days and on the following week reverse the sets of exercises. Start with set two.
I like this particular routine because it keeps a regular schedule and yet allows days of rest between exercises. It also varies the pattern and because the exercises are split in two, it doesn't take a lot of time.
Trainers may chose a different schedule, but you will find most are similar in nature. For example, they will make the strength building days with a weight machine but the speed and endurance days will be doing your actual sport. Variation in the type of training and which muscles are being trained are very important.
Modifications for Non-Athletes:
If you aren't training for athletics, you can take it at an easier pace. You need only do one or perhaps two sets of repetitions each day you exercise.
Do days 1, 3, and 5 and rest in between. Days 1 and 5 will be the first set of exercises and day 3 will be the second set. On the following week reverse the order. Days 1 and 5 will be the second set of exercises and day 3 will be the first set.
Even with the slower schedule you will be surprised at how well you will improve.