Thanks for the advice but I'm trying to put on muscle and gain some mass/weight. Are you sure that you don't need to work your muscles to failure?
I was always taught that you should barely be able to finish the last reps in your sets and really struggle to do them. I had a personal training session years back and he told me this is the only way you'll see results, by really pushing your body to the limit.
That philosophy is really more of a way to build strength. Same is true of forced reps. The problem that you run into with this "exhaustion" technique is that it is actually a form of overtraining that doesn't really trigger muscle build-up.
You don't have to lift to you max capacity and exhaustion to add muscle. Muscle building takes time and it's more the repetition of exercise over time alternated with periods of rest/low-intensity that triggers your body to add more muscle capacity and to store more carbohydrate in the muscle tissue.
Also keep in mind that you're building strength in your connective tissue (in the muscle, as well as with your tendons and ligaments) which is an even slower process. So, overexertion puts you at risk for connective tissue injury.
My guess is that you're probably going to see more results by going to alternating routines that stress your body with variety. This is called periodization.
Here's something you might try to see if it changes your workout- do 2 weeks of alternating cycles:
Weeks 1-2: do your usual 3 x 16 type weight set. Lower your weights and use these two weeks to push yourself in cardio. This sets a base weight level that your body will adjust to very quickly.
Weeks 3-4: Go lighter on your cardio and do weight routines that vary the weight and number of reps.
First, find your max capacity- the highest weight that you can complete 1 rep on.
Weight option 1:
- Increase your sets to 4 sets.
- In your first two sets, do a full set of 12-16 reps at about 60-70% of your max capacity.
- In your last 2 sets, do a short set of 6 reps at about 80-90% of your max capacity.
Weight option 2:
- Do your normal 3 set routine but start with a first set of 60-70% in your first set of 12-16 reps.
- In your second set, increase the weight by 10-20% and do 8-10 reps.
- In your last set, increase the weight to 80-90% of your max and do 6-8 reps.
What sometimes happens is that your body adapts to doing the same weight in sets of 3 times the same number of reps. Your maintain tone, but don't add bulk. The findings coming out of some of the exercise capacity research is saying that the body needs to be pushed harder in variable and constantly changing exercise alternated with periods of rest/recovery. So, when doing the treadmill, using the "hill" setting is more effective than using the constant setting. And in weight lifting, varying the weight and number of reps will push your body to adapt by stressing both the fast twitch and slow twitch fibers.
If you're interested in reading more about the theory behind this, here's a couple of articles from the American College of Sports Medicine that talks about periodization and overtraining:
Periodization (page 12):
http://www.acsm.org/AM/Template.cfm...EMPLATE=/CM/ContentDisplay.cfm&CONTENTID=1273
Overtraining:
http://www.acsm.org/AM/Template.cfm...emplate=/CM/ContentDisplay.cfm&ContentID=8647