Has anyone experimented with the different rest periods? What was the difference you noticed?
Longer Interset Rest Periods Enhance Muscle Strength and Hypertrophy in Resistance-Trained Men
PDF | The purpose of this study was to investigate the effects of short rest intervals normally associated with hypertrophy-type training versus long... | Find, read and cite all the research you need on ResearchGate
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Dr Brad Schoenfield's is one of the Hypertrophy Gurus.
This study determined...
"...That longer rest periods promote greater increases in muscle strength and hypertrophy ...
So, you can increase muscle mass with longer rest periods between sets.
However, in other research and anecdotal data (based on the Bodybuilding Protocol) have demonstrated that shorter rest periods are more effective for increasing muscle mass.
The downside is that when implementing this method, Power and Maximum Strength drop through the floor like a rock.
The Three Hypertrophy Mechanisms
In another piece of research, Shoenfield determined optimally increasing muscle occurs when these three mechanism are employed.
1) Mechanical Tension
Maximum Strength Training with heavy loads and long rest periods.
2) Muscle Damage
This is produce by. at time, pushing an exercise to failure or close to it.
It also occurs when a full range loaded movement is performed; like Full Squats or Dumbbell Bench Presses. Both place the muscles in a loaded stretch in the bottom part of the movement.
3) Metabolic Stress
This is another term for "The Pump", which is the primary mechanism for hypertrophy.
When moderate to high repetitions are performed, there is an increase in lactate, which produces an anabolic effect.
As Arnold said, "You don't grow without the burn".
"The Pump"
When moderate to high repetitions are performed, the heart pumps blood to the muscles (Arterial Blood Flow).
However, the muscle contraction restricts blood back to the heart (Venous Blood Flow).
The blood is trapped in the muscle, literally balloon it up.
Short Rest Periods
Performing short rest periods of 30 to 60 seconds keep most of the blood trapped in the muscles, increasing lactate.
Thus, with each set, the muscle swells in size.
It is similar to blowing up a balloon. With each breath you blow into the balloon, the larger it get.
Occlusion Training
The underlying mechanism of why Occlusion Training works for increasing muscle mass is that it restrict venous blood flow to a greater degree than the traditional moderate to high repetition protocol. Talk about a burn.
Summary
Schoenfield's research is contradictory, which makes it confusing.
However, what we know is that one of the primary factors for increasing muscle mass is by increasing Lactate.
Based on the anecdotal data of bodybuilders over decades and research on how lactate triggers an anabolic response, it appears that increasing muscle mass is optimized when rest periods between set are short; 30 to 60 seconds between sets.
The downside is that muscle mass is increased at the expense of Power and Maximum Strength.
Longer Rest period increase muscle mass but appear to be somewhat less effective than short rest periods.
The same is true for Hypertrophy Cluster Set Training, that I am a proponent of.
However, the Longer Rest Periods and Cluster Sets come in a close second; increasing muscle mass as well as maintaining and/or increasing Power and Maximum Strength.
Practical Experience
One of the best method of learning is being your own lab rat.