Get Results with a Single Set?!
As a fitness professional, I feel that it is my responsibility to be knowledgeable and familiar with all schools of thought so I can better serve and educate my clients. So I’m currently reading The 4-Hour Body: An Uncommon Guide to Rapid Fat Loss, Incredible Sex and Becoming Superhuman by Timothy Ferriss. Most of you are probably already familiar with this book or have already read it considering it is a best-seller from 2010. I know… I’m late to the party, but being formally educated, it took me a while to set aside my disposition and indulge myself in the outlandish guidance and information that is being provided to the health and fitness community.
Among several topics in this book, is the claim that in order build muscle:
“The exercises should be performed for one set each and no more. The objective is to fail, to reach the point where you can no longer move the weight, at 7-10 reps at a 5/5 cadence (5 seconds up and 5 seconds down.)” 
Did I mention that each workout consists of just two primary lifts?! Wow that sounds like a great deal to me. So it’s possible to get huge with less than 30min of gym time per week?
For the past 40 years there has actually been much debate among researchers on whether 1 set of an exercise really does elicits the same results as performing multiple sets.
Most exercisers perform anywhere between 1-4 sets of each exercise with the average being 3. One study found that 2-3 sets produced 40% higher increases in muscle hypertrophy and 46% higher increases in strength regardless of the training status of the subjects or the length of the training program versus performing only 1 set .
While, another recommends that appreciably the same muscular strength and endurance adaptations can be attained by performing a single set of approx. 8-12 repetitions to momentary muscular failure, at a repetition duration that maintains muscular tension throughout the entire range of motion, for most major muscle groups once or twice each week. 
My advice in making sense of this contradictory information- refer to your goal and current training status. Because truthfully, both methods work, but each one is better suited for different situations.
Single sets suit beginner lifters well because of the initial neural adaptations that take place compared to those who are more advanced. However, the effectiveness of a single set is highly dependent on intensity. In other words, it is necessary that a single set be performed to muscular failure, which is defined as the point during a set when muscles can no longer produce necessary force to concentrically lift a given load .
Training to failure appears to activate a greater number of motor units, within the muscle fiber. When an exerciser becomes fatigued during a lift, progressively more motor units are recruited from the muscle in attempt to continue activity. Continuing to train under these high stress conditions heightens the buildup of metabolites, which in turn increases the anabolic hormonal environment. In essence, performing a set to failure stimulates hypertrophy by accumulating just enough metabolic byproducts that tell your muscles to grow. So if muscle growth, or hypertrophy is your goal, single sets may suffice for a time.
Additional situations in which single sets can be beneficial is with smaller muscle groups (biceps, triceps,calves, etc), simple exercises (with dumbbells, machines, or body-weight), and situations in which you are crunched for time. You can easily get a total body workout in 15-20min when you are performing single sets.
One important fact to consider is that although performing single sets to failure appears to show muscle building benefits in a fraction of the time, it also increases the potential for excessive soreness and overtraining that can lead to injury if used too frequently and not enough recovery time is given . It is suggested that single sets to failure be used periodically and/or limited within an exercise program.
Multi-sets suit intermediate/advanced lifters and athletes well because they require a more sustainable method to make continuous gains. Multi-sets do not require achieving muscular failure, therefore allowing the body to partake in more frequent activity and skill acquisition.
Multi- sets also provide alternative modes of progression for moving out of a plateau. Muscles respond to progression, meaning you have to continue to challenge them to build strength. That’s why you may stop making gains after months of doing the same exercises using the same weights. Unlike novice lifters, who can get away with doing 1 set to failure and increase weight each workout, advanced level lifters must depend on adding additional reps and sets to push their progress when the weight won’t go up each training session and more volume is required. In fact, evidence exists that to maximize hypertrophy, volume should be progressively increased over a given periodized cycle followed by a brief taper or cessation from training. This ensures optimal super-compensation from the body and increased results .
Overall, you may benefit from only a single set of each exercise if you use a weight that is truly challenging for you, but to maximize your potential gains you will benefit from the additional challenge of doing multiple sets. Not to mention, doing multiple sets will increase your caloric burn and if weight loss is part o f your goal then multiple sets is the way to go. I’ll end by saying that there is not clear cut protocol for building muscle. You cannot hack the human body because the body will always adapt and require continuous variation. As coaching legend, Dan John, says often about fitness, “everything works…for about six weeks.”
4. Izquierdo M1, Ibañez J, González-Badillo JJ, Häkkinen K, Ratamess NA, Kraemer WJ, French DN, Eslava J, Altadill A, Asiain X, Gorostiaga EM. Differential effects of strength training leading to failure versus not to failure on hormonal response, strength, and muscle power gains. J Appl Physiol 100::1647-56, 2006.