Momentary Muscle Failure
Momentary Muscle Failure (MMF) is the point at which no more reps can be performed, with perfect form, due to complete acute exhaustion of the muscles required to complete additional repetitions. This article will further define MMF and discuss its importance in making gains in strength and power. We will also discuss muscle fatigue and the impact of intentionally holding back a few repetitions during a set.
PURPOSE OF FAILURE
Taking a set to the point where the responsible muscles are so exhausted that they can perform no more perfect reps is referred to as Momentary Muscle Failure, and taking a set to this extent produces physiological adaptations. These adaptations include an increase in mitochondrial density, increased motor pool activation, increased ATP-CP recovery rate, improved actin-myosin activation, increased hormone release with increased cell-site receptivity. There are also physiological benefits to pushing yourself to MMF, including stress relief, improved mental toughness, and increased mental capacity for harder work that will result in additional physiological adaptations.
Here’s the basic truth. If you give your best effort and push yourself to perform as many perfect reps as physically possible, your body will adapt so that the next time it is exposed to a similar challenge it will be able to perform better. The body does not understand why it is being pushed so hard, it only understands that it must adapt to the environment, so it evolves. If you do not push yourself as hard as you can, your body will not feel the need to improve because it can already perform what has been demanded of it.
When discussing MMF, it is vital to acknowledge that perfect reps are part of the definition. To push yourself to the point where no additional reps are possible without the “perfect reps” clause would lead to sloppy, unsafe, counterproductive reps at the end of the set. When the muscles can no longer hold proper form and can no longer move the weight under control, if additional reps are required, something must change to make it possible. The first thing that happens is cheating. Momentum and gravity are used to help out. Next, the form breaks down and the body changes its position to get more reps. Lastly, tendons and ligaments become strained to squeeze out whatever is left. None of these post-MMF techniques yield meaningful adaptations. They often result in injury, or reinforce bad habits that will ultimately inhibit progress. Bottom line, if you need to break form, use momentum or gravity to perform additional reps, you have already reached MMF and additional reps may lead to injury, so stop.
Using Momentary Muscle Failure to produce physiological adaptations must be methodical and intentional in order to prevent injury. It is best to experience MMF initially on machines using the upper body. This allows for a gradual mental adaptation to the intensity of MMF. Once you are mentally capable of pushing your upper body to MMF on machines, try it with free weights and begin using machines on the lower body. The more exercises you take to MMF, the lower the total volume of the workout will become. Multiple sets to MMF are still recommended for maximal gains in hypertrophy that results from volume and time under tension, but not redundant sets.
Example: Instead of performing multiple sets of bench press where only the final set goes to MMF, try performing a single set with more weight to MMF, and follow up with a cable chest fly to MMF for more time under tension and a variation. Remember that MMF is momentary, so if you rest for a minute or two, you will be able to keep going. Use this to your advantage and be intentional about work-rest ratios during MMF multi-set protocols.
Muscle Fatigue is the point at which the muscles are fatigued but have not reached momentary muscle failure. Think of it as leaving 1 or 2 reps in the tank. This is used most during multiple set protocols where intensity is measured by volume, not by sets to MMF. Multiple sets performed to fatigue instead of failure allow for more time under tension which leads to hypertrophy, increased motor pool coordination, and less demand on the mind. Gains may not be as significant as MMF, but improvements can still occur.
From a psychological standpoint, it’s unrealistic to push every set to MMF for the rest of your life, so workouts within an annual training regimen should include sets to fatigue. This gives you a mental break. Muscle Fatigue also keeps you further away from potential injury than MMF. Often with sets to MMF, you may be doing well, performing perfect reps, and then during a rep you feel like you hit a wall and form breaks down and momentum is used to finish that rep. I would not count that rep, but the point is that MMF often puts you in this position, muscle fatigue does not. Once you think you’re close to MMF, you hold back and stop, rest, and come back for another safe round of muscle fatigue. If you are looking to get a little stronger but not interested in maximizing potential, then muscle fatigue is fine year round.
Taking exercises to Momentary Muscle Failure forces your body to adapt and overcome. Muscle Fatigue does too, but not as efficiently. Be intentional about how far you plan to push the set and listen to your body. Be strict on your form and only count perfect reps. Cheating after MMF will only lead to bad habits and injuries. Check out my other article on Advanced Overload Techniques for some ideas on how to use MMF even more efficiently.