Body Weight as Resistance

Q: I would like to know can a person build muscle just using their body weight as resistance? The reason I ask this question is that I have a Nordictrack Ultralift home gym - this home gym uses your body weight as resistance (the resistance ranges from 3-120% of the users weight.) I read that your muscles do not have eyes so they don't pick and choose what resistance is best for them in order to grow. Muscles just know stress and they adjust accordingly, but if this is true then why do many magazines and personal trainers promote free weights more than any other resistance devices?

A: Response to first question: "Yes."

Reply to second sentence: "I'm sorry to hear that!"

And, to answer the rest: "Okay, this is actually a huge question that involves many variables. Let me just touch upon a couple issues - if you require more information consider a phone consultation with me. If you are concerned specifically with muscle hypertrophy, generally submaximal intensities (70-85% 1RM) are used which allows 6-12 reps for most people on most exercises - see Brad Schoenfeld's review: Repetitions and Muscle Hypertrophy in Str. Cond. J., 22(6), 2000. Now, that's not to say that you cannot achieve substantial hypertrophy outside that range because you can as evident in both strength/power as well as some endurance events. I am a fan, though, of closed-chain movements (in simple terms, exercises which require you to move your body around an object like squats, chin-ups, dips, etc.) If your machine allows me to do these movements at a resistance of 3-120% bodyweight, then my progress will be limited since I can easily handle 1.5-2 times my bodyweight on these exercises! However, it may be quite suitable for a beginner. I do agree that your muscles do not have eyes and that they will adjust to stress, but it's all relative. Is the stress enough for that particular individual? That's where free weights may offer an advantage."