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Issue 9

Table of Contents

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Towards an improved understanding of proximity to failure in resistance training and its influence on skeletal muscle hypertrophy, neuromuscular fatigue, muscle damage and perceived discomfort: a scoping review

Dr. Joe Camoratto PT, DPT

Key takeaways:
  • There is no scientific consensus on what proximity to failure means
  • Training to failure seems to be no better than not training to failure regarding muscle hypertrophy
  • Training to failure can accumulate negative short term results like increased neuromuscular fatigue and increased recovery time

 

In the scientific world, there are few things more important than definitions. It’s not glamorous, but being on the same page when trudging through the minutia of our reality can be the difference between having a productive conversation and one that is in two separate languages about three separate topics. Let’s start by taking a step back to look at some of the heavy hitters when it comes to things that are poorly defined yet heavily studied:

  • Pain
  • Injury
  • Fatigue

 

Things that are readily talked about in our career fields that simply dont have a consensus. With the paper we are reviewing today, we add a new candidate!

Proximity to failure

Now if you’re not big in the strength and conditioning world, this phrase may be foreign for you, but it’s easy enough to understand, despite it being poorly defined (I think). How close are you to being unable to perform another repetition during resistance training?

Easy enough right?

One of the primary objectives for this review was to “summarize key definitions for set failure in resistance training used throughout the literature.” Why do we need to define proximity to failure in the first place? The other goal of this scoping review was to “review the current evidence for the role of proximity to failure on physiological adaptations and short term responses to resistance training.”

Basically what happens to the body in the short and long term when we broach failure in the context of resistance training. When building programs for athletes, proximity to failure can also be read as intensity, which is one of the main training variables we need to focus on. So any additional information that we can get our understanding on about this training variable is just going to help move the knowledge needle forward.

We know a great deal about the training variable king: volume. Jacob Templar was nice enough to write about it in the last research review. Check it out if you haven’t read it yet. Here is a short excerpt that is pertinent to our current conversation:

When all factors are equal in resistance training programs literature consistently reports that those who perform more volume see improved muscle mass. While there are benefits to ensuring that the total intensity is adequate, volume is still the king. Thus far, most adjustments to training variables to achieve the maximal effect revolves around maximizing the amount of volume an individual performs.

Considering that lean body mass is an important aspect of morbidity and mortality, learning how to farm more muscle should be an interest of ours. Let’s flip back to proximity to failure. We know that as we near failure “there is a progressive increase in recruitment of higher threshold motor units that exposes type II muscle fibers to mechanical tension which is the key stimulus for myofibrillar protein synthesis and subsequently muscle hypertrophy.”

We also know that “proximity to failure during resistance training influences short term physiological responses including neuromuscular fatigue and muscle damage which can impair contractile function during and subsequent to resistance training.” In layman’s terms, how close we get to failure can influence how much volume we can tolerate in the remainder of that training session and others for days after that session. To bring it all together, knowing how close is close enough to failure is a good thing to know for muscle hypertrophy.

Which brings us back to the problem of consensus for proximity to failure in the literature. This scoping review defined the different types of proximity to failure for us:

  • Momentary muscular failure: “When an individual attempts but cannot complete a final repetition.”
  • Volitional Failure: “When an individual perceives they have reached the prescribed set termination criteria.”
  • Repetition Maximum: “Typically required participants to first complete a repetition maximum test, which involved determination of a load that results in a given number of repetitions”

 

There are nuances to each definition. Some studies put clarifiers onto momentary muscular failure like “each participant failed to follow the given tempo” or “he was unable to lift the barbell after lowering it” as well as “proper form” being necessary for some studies, but that is a pandora’s box in and of itself.

Volitional failure gets squirrely when we start to introduce subjectivity into the mix. If proximity to failure means “I’m done when I feel like I’m done rather than when my body stops responding” then the variability of actual proximity to failure will depend on the unique constitution of the participant. Finally, repetition maximum lends itself to the flaws introduced by the ever adapting human organism. The authors warn about things like “learning effects” (increases in strength and/or performance due to improved motor control and familiarization with a given protocol). The problem with truth (as best as we can find it) depends on consensus regarding study design and in this case, definitions.

So with this mish mash of definitions, let’s zoom in on the outcomes we want to study in the context of proximity to failure.

  • Muscle hypertrophy
  • Neuromuscular fatigue
  • Muscle Damage
  • Perceived discomfort

 

Muscle Hypertrophy

Even though there is no consensus on the definition of proximity to failure, it seems that no matter how you define it, you need not get all the way to failure to reap the benefits of resistance training. You can just come close. How close? Who knows.

“Although current literature suggests resistance training performed to momentary muscular failure is not superior to non failure resistance training for muscle hypertrophy, and that achieving a closer proximity to failure does not always promote greater muscle hypertrophy, it it unclear how far from momentary muscular failure resistance training sets should be terminated to theoretically maximize muscle hypertrophy.”

Neuromuscular Fatigue, Muscle Damage and Perceived Discomfort

These were defined as “short term responses to resistance training” and the authors spent a good bit of article space talking about how all of these take a negative hit when training to failure. Why does that matter? Well if the overarching goal is to stimulate muscle hypertrophy, being a try hard basically wears you out with no added benefit for the extra effort. In fact, there is likely a net negative in the overall goal of muscle hypertrophy due to reaching failure.

“A recent meta analysis found a greater decrease in mechanical measures (jump height, lifting velocity, power, isometric strength) of neuromuscular fatigue and a simultaneous increase in metabolic response (blood lactate) and higher muscle damage after resistance training performed to set failure versus non failure.”

The authors also suggest that going to failure extends the recovery time and may impact the short term responses due to impaired neural drive secondary to neuromuscular fatigue. This can suppress muscle fiber recruitment, force production, mechanical tension and muscle hypertrophy. To linger on the increased time to recover, we could relate this back to the king of variable: volume.

One of the overarching themes here is that training to failure essentially will leave less able to tolerate more volume, both inter and intrasession. “Increasing the time course for recovery of neuromuscular function post resistance training could limit the volume and/or frequency of subsequent resistance training, and higher ratings of perceived discomfort may negatively influence long term adherence to resistance training, both of which may negatively impact long term muscle hypertrophy.”

At the end of this paper, the authors do a great job of unwinding all of the understanding about the issues with training to failure by saying that sometimes, it’s ok to train to failure. Their justification is this: training to failure has no negative effect on muscle hypertrophy, just make sure to not forget about the neuromuscular fatigue that comes along with it. It seems that however you skin this cat that is proximity to failure, training to failure is not as desirable as not training to failure, wherever that may land you. 

 

References:

 

Age related muscle anabolic resistance: inevitable or preventable

Dr. Joe Camoratto PT, DPT

Key takeaways:
  • Anabolic resistance is a problem that affects a quickly growing portion of the population
  • We can manage it with resistance training and protein intake manipulation
  • It seems that a protein intake of 1.6g/kg/day to 2.2 g/kg/day maximizes muscle hypertrophy and strength gains in resistance trained adults

 

There is a wave coming. A wave of old people. Specifically people over 60 years old. It’s estimated that by 2050, over 11% of the global population will be over 60 years old, and the population of over 80 year olds is projected to triple. Why rattle off all of these geriatric statistics? Because we need to be cognizant of their needs as they (and we) get older. The second paper we are looking at today deals in age related losses: Age related muscle anabolic resistance: inevitable or preventable?”

Due to so many of us lasting so much longer than before, there are certain aspects of aging that are quite common, that seem to be based on things that we can control better than we once thought. The topics that this paper hits on hard are sarcopenia, frailty and dynapenia. Frailty made an appearance in an earlier research review (number 4 to be exact). Its defined as “a state of increased vulnerability due to age-related decline and dysfunction across multiple physiologic systems.” Sarcopenia on the other hand is “the age-related loss of skeletal muscle mass, strength and physical performance.” Finally, dynapenia is simply defined as “age related strength loss.”

All three of these together paint a picture that isn’t one that a lot of people want to look at, but we really need to. Humans lose an average of over 0.5%, 1-2% and 3% of muscle mass per year after 40, 50 and 60 years old, respectively. That doesn’t even take into account strength loss, which happens even more rapidly than muscle mass loss.

Anabolic resistance is thought to be the main driver in each one of these age related losses, and it is defined as “the resistance of skeletal muscle to anabolic stimuli.” The mechanism for loss of muscle mass is when there is more muscle protein breakdown than muscle protein synthesis. This is referred to as negative net muscle protein balance. The two things that mainly stimulate muscle protein synthesis are ingestion of protein and resistance training. To kick things off in the protein ingestion aspect of this paper, insulin and its effects come into play as aging occurs. Due to older adults being less sensitive to the anabolic impact of insulin on muscle, the muscle protein synthesis is reduced.

Why are they less sensitive? It seems that age takes a toll on a few important things like endothelial vasodilation which leads to a blunted muscle protein synthesis response of skeletal muscle to insulin. There is also resistance to the function of insulin called the antiproteolytic effect, which keeps protein from being broken down. While insulin may have decreased effects over the years, anabolic resistance in and of itself has a more nuanced origin. It seems that anabolic resistance itself may be more from a mix of things like increased inactivity, low grade inflammation and/or increasing obesity.

“The development of anabolic resistance is no ineluctable consequence of growing older. Moreover, this lack of certainty suggests the possibility of prevention or treatment by implementation of concurrent training and nutrition based interventions.”

Increased inactivity can contribute to skeletal muscle atrophy and this loss of muscle mass is associated with a reduced sensitivity to protein ingestion. Things like volitional inactivity, injury, surgery or immobilization can all contribute to this atrophy, and it’s this atrophy that decreases the ability for muscle mass to serve metabolically. We can see how this vicious cycle of aging, becoming more sedentary, skeletal muscle atrophy and increased sensitivity to anabolic stimuli can perpetuate sarcopenia, dynapenia and frailty as well as anabolic resistance.

“The sustained effects of an energy dense/nutrient poor diet and a physically inactive lifestyle can exacerbate the predisposition to chronic diseases in advanced age. This sets the stage for sarcopenic obesity, where continued decreases in lean mass and increases in fat mass are accompanied by increased insulin resistance, oxidative stress, and chronic low grade inflammation.”

The cycle continues with the introduction of obesity, as obesity is linked with decreased levels of physical activity, increased risk for adiposity based chronic diseases and may also lead to impaired muscle metabolism and function. With decreased levels of physical activity secondary to obesity comes decreased sensitivity of the muscles to ingested protein.

The cycle continues even further with ectopic obesity, or obesity in places that it shouldn’t be, like the liver and skeletal muscle, which are two big insulin activity sites. So there is a lot that can go wrong here, and a lot of things that seem to contribute to anabolic resistance. What are some things that can be done to decrease the effects of anabolic resistance so this second review is not all doom and gloom?

The key hides in reflecting on the two big contributors to muscle protein synthesis. Resistance training and protein intake. Due to age-related changes in strength being a stronger predictor of age-related disability and mortality, the focus seems to be on increasing muscle strength over increasing muscle mass, even though both are important.

“The increase and/or preservation of muscle mass serves to protect metabolic function, while the pursuit of strength increase and/or maintenance can protect neuromuscular function and prolong physical independence in older adults.”

The authors were kind enough to give us an example program from another systematic review to get a glimpse of what might be a good evidence based program in relation to sarcopenia and dynapenia. “Subjects >65 years who met standard diagnostics for frailty, resistance training at a frequency of 1–6 sessions per week, 1–3 sets of 6–15 repetitions, and intensity of 30%–70% of 1-repetition maximum increased maximal strength by 6.6%–37%, muscle mass by 3.4%–7.5%, muscle power by 8.2%, and functional capacity by 4.7%–58.1%.”

The other aspect of overcoming anabolic resistance and sarcopenia is protein intake. It seems that a protein intake of 1.6g/kg/day to 2.2 g/kg/day maximizes muscle hypertrophy and strength gains in resistance trained adults. This is an easy enough equation to use in the clinic or gym when trying to pick the low hanging fruit.

And remember:

BW (in kg) x 1.6 = ___ g protein/day

BW (in kg) x 2.2 = ___ g protein/day

“It is therefore possible that this intake level should be the minimum to be maintained through older age, alongside regular resistance-type exercise, if the goal is to maximize sensitivity to anabolic stimuli and preserve muscle mass.”

To break this down into a per meal number, 0.4g/kg – 0.6g/kg of protein per meal (with 2.5-2.8g leucine) every 3-4 hours seems to be ideal. Don’t let the timing fool you thought. It’s much more important to just hit the total daily protein goal rather than focus on the timing, if people are having trouble hitting that total protein number. Why would getting this amount of protein be difficult? Well a typical American only eats 50-60g per day, and most of that is at dinner. Imagine needing to double that intake (or more) just to hit the minimum, when historically you didn’t eat that much protein.

Then take into consideration that protein has a satiating effect (don’t feel as hungry as quickly after eating) and you have a challenge on your hands. One easy recommendation is to be heavier in breakfast and lunch with protein, as those seem to be, on average, very light protein wise for the American population.

Getting in a protein shake or some other form of easy protein right before bed can be helpful as well “particularly in the post exercise period, where an approximately 40g – 48g dose augments the overnight muscle anabolic response in skeletal muscle.”

The final suggestion from this paper comes in the form of supplementation. Their biggest recommendation is that creatine monohydrate should be considered due to the vast and consistent evidence for its role in enhancing muscle size, strength and power.”

“A meta-analysis by Devries and Phillips examined the effects of creatine on older subjects in studies lasting at least 6 weeks, and concluded that creatine enhanced gains in muscle mass, strength, and functional performance over resistance training alone.”

To sum things up, anabolic resistance is a problem that we have a pretty good ability to manage with resistance training, dietary changes and body composition management.

“Despite inevitable degrees of uncertainty, evidence indicates that the onset and progression of anabolic resistance can be significantly delayed or mitigated by lifestyle habits that simultaneously facilitate exercise, body fat level, and protein/nutrient intake (and/or supplementation) conducive to this goal.”

 

 

References:
  1. Aragon et al Kevin D Tipton, Brad J Schoenfeld, Age-related muscle anabolic resistance: inevitable or preventable?, Nutrition Reviews, Volume 81, Issue 4, April 2023, Pages 441–454, https://doi.org/10.1093/nutrit/nuac062