Would you take on a second job working additional 40 hours a week if it paid you 9% of your first job? So if you worked 40 hours for $1,000 would you work 40 more for 90 bucks extra? That’s pretty close to the bargain you are making when you go beyond one set of exercise. In fact, in some cases it’s a lot worse.
We asked eight middle-aged men to do some experimentation with bench press and leg press variations and the data showed that there is a reduction in intensity when performing additional sets. On bench presses with 50% of bodyweight it was startling. When performing only one set to failure the lifters could average 2,257 lbs/min of intensity but only 1,629 and 1,455 when they did two or three sets to failure. Unless you are an endurance athlete of some type who specifically needs to build endurance power, there doesn’t appear to be a reason to sacrifice so much intensity just to do more bench press sets. Nothing we tested beat the peak intensity of doing one set. (Well, SCT beat it but let’s stick to conventional, full-range training right now.)
Things were slightly less obvious when we tested leg presses using 100% of bodyweight. Two variations delivered slightly more intensity than one set to failure. Three sets to failure and a 3-minute timed set were 9% and 17.6% higher intensity. However, the trainees had to perform 120% and 102% more reps in order to get those improvements. Thus, my analogy of working a second full-time job for 9% of your first job. It’s a lot of work for a little gain. I suspect (but never tested) that if the trainees were allowed to use more than bodyweight on the leg press that the results for one set to failure would be more like the bench press – the clear winner.
One thing is for sure, doing one set to failure is not a stupid way to train. I would recommend it to anyone training conventionally. It might not be best for a guy training for an endurance event that requires power, but how many of those guys are there? One set to failure has the added benefit of making it easy to keep track of intensity numbers; weight x reps divided by minutes and you have a good benchmark to try to beat next time. Progressive intensity is the key to steady progress.