Learn about the impact of rest periods and training to failure, to help you train better and maximize your time in the gym.
How Varying Intensity Techniques Can Lead To New Muscle Growth
Read Part 1: Intensity Is Everything: Part 1
“I think I’m gonna throw up!” My young training client said in a panicked voice as he was gasping for air. He had just finished a brutally hard set of squats. I couldn’t help but laugh because not more than 5 minutes ago he had bet me that he trains legs harder than anyone I’ve ever met. I could tell by the sickly look on his face that he knew had lost that bet.
We were only 4 sets into the workout but we had been working at a blistering pace. On the last set I literally had to drag him to the upright position. “I am not used to taking so little rest between sets and I’ve definitely never taken squats to failure before.” He said. We made it though one more set before he went to the bathroom to revisit his pre-workout meal.
I actually see this happen a lot. New clients always brag to me about how hard they train but once we get into the workout you’d think that it was their first day. It is not always that they do not train intensely on their own but rather they do not vary their training enough. Too many bodybuilders find a training style that they prefer and very rarely stray from it.
The human body is extremely adaptive, and if it is not challenged with new stimulus it will not continue to change. In part one, I discussed the importance of varying the volume and load of your workouts while not overtraining. To put together a plan that constantly challenges you with new forms of high intensity training there are other factors that must also be addressed and controlled.
Rest periods between sets are something that most bodybuilders rarely change. As with rep ranges and the number of sets used during training, most lifters find what they like best and tend to stay within that comfort zone. Rest periods are yet another tool that can be used to raise the intensity of your training.
The amount of rest taken in between sets is directly related to how much energy will be available to your muscles when the next set begins. It takes about 3 minutes after a set for muscles to recover nearly 100% of ATP (adenosine tri-phosphate) and CP (creatine phosphate), which are the two primary energy sources for a working muscle.
This will allow near maximum weights to be used for nearly every set. This is why strength and power athletes take very long rest periods between sets. Taking long rest periods with heavy loads should be incorporated into every bodybuilder’s routine as this will help with the ultimate goal of progressive overload.
Shorter rest periods between 60-90 seconds, will allow for approximately 85-90% recovery of ATP and CP . Short rest periods have been shown to have a greater impact on growth hormone levels than long rest periods. Keeping breaks short works great when training for hypertrophy with moderate to light loads for high reps and more volume. Studies show the most dramatic increases in growth hormone with sets that are at least 10 reps combined with rest periods between 45- 60 seconds. 
Shorter rest periods also have the advantage of allowing more volume in a workout with less duration. Growth hormone and testosterone levels peak 60-90 minutes into training and fall quickly thereafter. If exercise continues too far beyond this point hormone levels can fall below normal resting levels and can actually remain lower for a few days. [3, 4]
I am not an advocate of looking at the clock with a dead stare until my next set, but too often I see bodybuilders take rest periods that are all over the place. Too much talking and texting is most often the culprit. There is no need to change for Facebook status to “Blasting Bi’s and Tri’s” right in the middle of your workout.
It is not acceptable for football or basketball players to text or talk on the phone during practice, so why should bodybuilding be any different? All of these are distractions that will rob you of your focus and intensity. There is no need to break out the stop watch, but appropriate timing between your sets will require paying attention and focusing on the task at hand. Leave the distractions in the locker room and your training will skyrocket to a new level of intensity.
Although failure is a little different than the other forms of intensity discussed here, I feel it needs to be addressed. When training to the point of momentary muscular failure heavy or light loads can still be used. It is simply continuing a set to the point where another rep cannot be completed with good form without assistance from a spotter. When most people think of really intense training, the first thing that usually comes to mind is lots of sets to failure.
This is why whenever the topic of training intensity is discussed, failure training is often the point of emphasis. Just like the other forms of increasing intensity, training to failure has been a very heated topic in the bodybuilding community for decades. Many advocates of training to failure feel that a set not taken to failure is a wasted set. Detractors of failure training avoid taking any sets to failure for fear that it will lead to overtraining. Both groups have valid concerns that need to be addressed.
The rational for training to failure is that during a set, as some motor units fatigue and drop out, other motor units must be recruited for continued activity. The problem with this rational is that, by this rational, one could simply be able to exercise to failure with very light resistances and produce large gains in hypertrophy and strength.
As discussed earlier, this is not true, it is well known that heavy to moderate loads must be placed on muscles to achieve maximum hypertrophy.  Training to the point of failure has been shown in many studies to produce gains that are superior compared to when sets are terminated early. Although training to failure has been shown to be more effective, stopping sets just short of failure can also produce large amounts of growth.
This is because overload is the primary determinant for muscle growth, not failure. Continually lifting heavier resistances for all different rep ranges will overload muscles and force adaptations. This is easier said than done as anyone that has lifted weights for many years knows. Increases in strength are not always steadily moving up at a constant pace rather increases seem to ebb and flow. This is one of the reason why taking sets to failure is effective.
At some point in training, optimal gains are produced by taking sets to the point of momentary muscular failure.  Failure also may be the best way to increase the intensity of a workout. Once a training session begins, testosterone and growth hormone (GH) levels will increase within the first few minutes.
How high levels of both hormones go is directly related to the intensity of training. Intensity of exercise is the primary determinant for how much GH your body will secrete, while duration and volume have little to do with GH secretion . For this reason, training to failure can be a great way to increase the intensity your training and to take advantage of the increased anabolic hormone release.
One disadvantage of training to failure is that it is very taxing on the central nervous system. The nervous system is responsible for activating motor units during exercise. Although muscle tissue may be able to recover from taking many sets to failure, the nervous system will not. Some programs that call for all working sets to be taken to failure will definitely lead to overtraining.
Workouts must contain both sets to failure and sets close to failure along with periods of time where no sets are taken to failure. Many of the benefits of failure training can be had by taking a set very close the point of failure. Stopping a set 1-2 reps just short of failure will allow for sufficient fiber stimulation while sparing a lot of stress on the nervous system.
One thing to note is that high intensity overtraining has a much different affect than high volume resistance overtraining. The main difference between the two causes of overtraining is the effect it has on the endocrine system. With high intensity overtraining, catecholamines, which are the fight or flight hormones, actually show an increased response to training. Also, while volume related overtraining will cause a decrease in testosterone levels, intensity related overtraining will leave testosterone levels unaffected. 
The ultimate goal of any training program is to push as hard as possible while not overtraining. Bodybuilders are always tip toeing on the brink of overtraining and it seems that if that line is crossed the effects will be less detrimental if more intensity and less volume is used.
Putting It All Together
These intensity boosting techniques are different from those such as drop sets and supersets. Although those are great intensity boosting techniques and should definitely be used from time to time, principles of load, volume, rest periods, and failure must be adjusted in your weight training to ensure constant and steady growth for years.
These aspects of training are not independent of each other, and if one is adjusted all other must be adjusted accordingly. There is a reason nobody sprints a marathon. Appropriate levels of intensity will vary greatly from person to person depending on genetics, diet, and whether or not steroids are involved. Those who have made the choice to be natural bodybuilders have chosen a difficult road.
Natural bodybuilders must be more conscious of every single one of these points since drugs will not make up for the flaws within their training. Be sure to take a hard look at the intensity level of your own training. In my experience, most lifters convince themselves that they are training more intensely than they actually are. Many people have no problem going from set to set with very little rest periods.
Many people have no problem lifting heavy weights or doing a lot of sets. You’ll find though, that very few people have the determination to strive to be great in every aspect of the word intensity. Doing so takes a level of planning and pain that most are not willing to go through.
My young training client returned from the restroom looking pale as a ghost. Sweat was still dripping off of him. I expected him to say that he was going to head on home. Instead he looked at me with a smile and said, “Man, what a great workout. I need to do this every week. So what’s next?” I knew then that this kid was going to do just fine at his show.
Read Part 1: Intensity Is Everything: Part 1
1. National Academy of Sports Medicine, Optimum Performance Training for the Health and Fitness Professional: Course Manuel, 2008, 332p.
2. Baechle, T. R., Earle, R. W., Essentials of Strength Training and Conditioning, 2008, 58p.
3. Garret, W. E., Kirkendall, D. T., Exercise and Sport Science, 2000, 152p.
4. Kreider, R. B., Fry, A. C., O�Toole, M. L., Overtraining in Sport, 1998, 153p.
5. Frohlich, M., Pruess, P., Current Results of Strength Training Research: An Empirical and Theoretical Approach, 2005, 80p.
6. Fleck, S., Kraemer, W., Designing Resistance Training Programs, 1997, 20p.
7. McArdle, W. D., Katch, F. I., Katch, V. L., Essesntials of Exercise Physiology, 2006, 410-411p.
8. Chandler, T. J., Brown, L. E., Conditioning For Strength and Human Performance, 2007, 119p.