Without knowing your goals, your training plan, the time you spend in the gym, the workload you put in the gym, it's going to be difficult to prescribe anything that will 100% work. However, there are a few principles you can go by:
- Set both short term and long term goals and work to beat them.
- Well rounded programs include strength, hypertrophy, conditioning, and mobility. If you compete in a sport, then skill work also applies.
- There's several types of strength: the ability to move objects over distance (force), the ability to move those objects quickly (power), and the ability to resist movement (isometric).
- Your body needs enough rest to rebuild muscle, but can do a lot more work than you think.
- If you feel like you've been hit by a Mack truck, and your strength is going backwards, you need more rest.
- If you are progressing toward your goals, keep doing what you are doing.
- Your body is amazingly adaptive. It can handle physical labor on top of a training program.
If you are running a beginner program like Starting Strength, StrongLifts, or AFP, you will eventually hit a wall where it feels you are going backwards. That's normal, and the programs all have ways of dealing with it to squeak out a few more quick gains. After that, you will need a program that moves a bit slower and is more flexible. More importantly, it allows you to do more things. Also, if you are fresh into the beginner program, you will have a lot more nervous energy that you can burn off--but if it starts interfering with your strength portion, you might have to taper.
Evaluate your program and goals
Take stock of what you are doing, what you want to do, and what is missing. We all have goals. They can be aesthetic like wanting to get big and ripped, or they can be more easily measured like I want to bench my body weight 5 times. If you are getting stronger, but running out of breath going up stairs, you may want to consider conditioning work.
- Your body usually does fine with conditioning work even on off days. Vary the intensity depending on how you feel. 30 minutes of low heart rate walking can do wonders for active recovery and getting rid of DOMS.
- You can always work on mobility, and there is always something that is a bit tighter than it needs to be.
- You can work on accessory exercises like curls, chin-ups, etc. However, if your main work is suffering because of this extra work, you may need to cut it out.
As to major muscle groups that can take a pounding and come back for more, any of your core muscles are game. That includes your abs, back, obliques. You could do planks every day without affecting your your main lifts--as long as you don't do them right before the main lifts. If you are running Starting Strength or StrongLifts, they don't have any curls and they tell you that pull-ups are way better, blah, blah, blah. As a heavy guy, I'm still working on being able to do one pull-up, and the strain it puts on my tendons is a bit much. Adding curls once a week for 3 sets of 10 can help strengthen the tendons and balance your strength in your arms so you don't get elbow tendinitis (or you can correct it if you already have it). That's just a tidbit I recently discovered, and it helps a lot.
