It is often said that it is easy to train untrained muscles. How easy?
That is said in the context of strength training. Basically if you start with an empty bar and increased 5 lbs every week you would be able to continue that pace for a few months. Depending on the size of the muscle group some will be able to maintain the pace longer than others. That fact is what Starting Strength or Strong Lifts are built around.
Another part of that fact is the process of getting better technique which helps you lift more weight. Many times beginner gains happen as much from learning technique as they do just getting stronger. The technique effect is also what helps someone who is already strong get stronger at a completely new movement relatively quickly.
All muscle groups are easily trainable, but the larger the muscle the more it can be trained. For example, you won't be able to put the same weight over your head as you can squat.
So what about ellipticals?
Ellipticals are designed to train your cardiovascular system. You will enjoy going from gasping for breath after a relatively short period of time on the elliptical to being able to maintain a very respectable pace for a long time.
Both cardio and strength are important factors in being fit. Both are worthwhile efforts. However, cardio doesn't fix your posture or help you move better when you are getting up and down.
What's the least level of strength needed to get a bit bigger?
This question needs some parameters, so I will tell you what they are and you can fill in the blanks:
- How much bigger are you wanting to get?
- How strong are you now?
- How do you eat now?
- How much sex do you get regularly (affects testosterone levels which in turn affect natural HGH release)
- Do you have self destructive habits? (binge drinking, staying up all night playing video games, etc.)
If you want to add size then you have to get stronger than you are now. You also have to have a bit of endurance with that strength. If you can do reps in the 8-12 rep range for most of your strength work, and do them at a relatively slow tempo you will be able to add size with even relatively low weights.
Just keep in mind that it's kind of like tanning. If you tan for 15 minutes a day, you will get darker than you are now, but eventually you won't get any darker. You will need to increase your time in the sun if you want to be darker than 15 minutes gave you. The same goes for building size. Increasing your bench press by 50 lbs (easy with beginner gains) will give you more size on your arms and shoulders, but if you aren't happy with that size you will need to go heavier.
Cardio will help you lose fat, and move blood around your body much better. However, it doesn't really provide the type of resistance needed to make you gain any size. Also remember that exercise is specific. Strengthening your upper body doesn't make your lower body grow any more than the reverse is true. Some exercises release the most natural anabolic hormones like squats and deadlifts, but they are used on the muscles that had the most work. Squatting won't give you a bigger chest any more than benching will give you bigger quads. There is always a cause and effect.