I'm in the gym monday - friday, usually first thing in the morning. I'm currently finishing an 18 week program. The first 6 are spent with low weight, high reps. The next 6 are in the mid range. The final 6 (where I'm currently) are high weight, low reps. If I feel up to it, and I rarely do, I'll go in on saturday for dedicated cardio (vs. warm-up cardio on normal days).
Monday/Thursday, chest and back. Tuesday, shoulders. Wednesday, legs. Friday, bi's and tri's. I go to the gym for everything because there's no way I could afford all the weights I'd need at home. Even if I amortized the cost over a few years, I still wouldn't break even. Plus, I enjoy seeing what other people are doing at the gym. Not in a creepy way! New exercises, new techniques, etc. And it's a good way to get advice from the pros.
Once I'm done with my 18 weeks, I'll take a full week off to thoroughly recover and then go back to it. My goal is 250lbs. At that point, I'll switch over to a cutting routine to shed the excess poundage. Lather, rinse, repeat until I'm... haven't decided the stopping point yet.
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