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Influence of Resistance Training Proximity‐to‐Failure on Skeletal Muscle Hypertrophy: A Systematic Review with Meta‐analysis

Refalo, M.C., Helms, E.R., Trexler, E.T., Hamilton, D.L. and Fyfe, J.J., 2023. Influence of resistance training proximity-to-failure on skeletal muscle hypertrophy: a systematic review with meta-analysis. Sports Medicine, 53(3), pp.649-665

In today’s letter

• Overview of how proximity to failure affects muscle size

• 3 clinical tips

• Resources to check out to further your knowledge about muscle growth

• Meme of the week

• Rapid Results =

1. No proof that exercising until muscle failure is better than stopping short for muscle growth

2. Theoretically, closer proximity to muscle failure, as indicated by higher velocity loss thresholds, leads to non-linear increases in muscle hypertrophy.

3. Whether you push to muscle failure or not, the amount of weight lifted or relative load doesn't significantly affect muscle growth during resistance training 

• Professional takeaway =

It seems like having a few reps in reserve for the first sets & the go to failure on the last one is the best way do drive hypertrophy (muscle size)

Definitions

• Sub-group analysis = A statistical method used in research to examine and compare specific sub-groups within a larger population or dataset. It helps researchers understand how different segments of the population may respond differently to a particular variable or intervention.

• Velocity loss = In the context of sports or fitness training, velocity loss refers to the reduction in the speed at which a movement is performed during a set of exercises. It is often used to gauge fatigue and training intensity, with a higher velocity loss indicating greater fatigue

Aim of the study

“To review the literature and determine how training to failure affects muscle growth. This Systematic Review & meta-analysis grouped studies into 3 themes”

• Theme 1: Research comparing groups doing resistance training until they can't continue with the repetitions (reps to failure) with groups that stop short of this point.

• Theme 2: Studies comparing groups performing resistance training to set failure (defined as anything other than the definition of momentary muscular failure) to non-failure groups 

• Theme 3: Studies exploring the idea of different levels of nearing failure during resistance training by applying various thresholds for how much they can slow down or terminate their sets. (velocity loss)

Click here for a video explaining velocity loss is more detail (6min):

Click here for video demonstrating velocity loss training(20sec):

Did you know?

Resistance training is widely known to promote muscle growth by changing the structure of the tissue.

Several factors influence how effectively this happens:

1. Total exercise volume

2. Amount of weight lifted

3. Training frequency

4. The speed of each repetition.

One particularly important concept is “proximity-to-failure,” which refers to how close you get to complete muscle fatigue during a set.

The challenge is that research on this topic is complicated as there’s no consistent way to define or measure proximity-to-failure. This inconsistency makes it difficult for scientists and coaches to fully understand how it influences muscle growth or to offer clear, practical guidance on how to apply it in training programs.

Non the less, that is exactly what we are aiming to do with this breakdown 😉

One thing that is good to mention,

Is that a few studies suggest that higher velocity loss (typically more than 25%) during resistance training might be more effective for stimulating muscle growth compared to lower velocity loss of 25% or less.

However, the difference between training with 20–25% velocity loss and training with more than 25% loss seems to be minimal, which, as always, means that the relationship isn’t straightforward or perfectly linear.

The problem becomes even more complex when you consider that there’s still no universally accepted definition of what “failure” means in the scientific literature.

Methods

This systematic review and meta-analysis that analysed 15 eligible studies.

The researchers aimed to answer three main questions.

First, they wanted to determine whether training to failure versus stopping short of failure had different effects on muscle hypertrophy (five studies were included for this).

Second, they examined how different levels of velocity loss during training influenced muscle growth (four studies were included).

Finally, they looked at muscle hypertrophy outcomes in resistance training performed to momentary muscular failure, as defined in six studies.

Comparison of Training to Failure vs. Non-Failure

In total, nine studies compared two common approaches to resistance training:

Performing repetitions until you can’t complete another rep (set failure) versus stopping before that point (non-failure).

These studies measured muscle growth across various muscle groups.

Of the nine, five defined failure specifically as “momentary muscular failure” and were grouped under Theme A, while the remaining four used different definitions of set failure and were grouped under Theme B.

Five of the studies made sure that both the failure and non-failure groups performed the same total work, while three did not.

In terms of training intensity, five studies used heavy loads, more than 50% of a person’s maximum weight, while two used lighter loads of 50% or less.

In Theme A, 4 out of the 5 studies found no significant difference in muscle growth between training to failure and stopping just short of it. Similarly, in Theme B, no major differences were found between the two approaches.

Another six studies (Theme C) looked at resistance training in people who were already trained.

These studies compared performing repetitions quickly until a large loss in speed occurred (more than 25%) versus performing repetitions at a moderate speed (20–25% velocity loss).

In five of these six studies, muscle growth occurred under both conditions, but there were no significant differences between the two.

Impact of Training Volume, Load, and Velocity Loss on Muscle Growth

When it comes to how training volume, relative load, and the definition of failure influence muscle hypertrophy, Theme A showed that there was no meaningful difference between training to momentary muscular failure and stopping just before that point.

The observed differences were statistically and practically insignificant.

Looking more closely at the role of velocity loss, the researchers found a statistically significant relationship between higher velocity loss and greater muscle hypertrophy.

In other words, when participants experienced a larger drop in repetition speed—indicating greater fatigue—they tended to show a higher increase in muscle size.

Defining Training Failure and Its Influence on Results

As I eluded previously, one of the biggest challenges in this area of research is the lack of agreement on what “failure” means.

Because studies use different definitions, comparing results can be difficult.

Previous analyses found no difference between training to failure and non-failure training, but in this review, when all studies were considered together regardless of definition, there appeared to be a small advantage for training to failure in promoting muscle growth.

However, when the authors separated the studies based on how they defined failure, two important findings made an appearance.

1. Training to momentary muscular failure didn’t show a clear advantage over stopping just before that point.

2. Simply getting closer to failure didn’t always translate to more muscle growth.

The authors also discussed the effect of total training volume on proximity-to-failure and muscle hypertrophy.

They proposed that the total number of sets performed per muscle group per week might have a greater impact on muscle growth than the total amount of weight lifted.

In fact, seven of the nine studies in this category had identical weekly set volumes across groups, which may explain the lack of large differences in hypertrophy.

Role of Total Training Volume and Relative Load in Muscle Hypertrophy

The effect of relative load (how heavy the weights are compared to an individual’s maximum) had some interesting outcomes

The researchers noted that participants had a harder time estimating how close they were to failure when lifting lighter weights. This is likely because lighter loads often feel more uncomfortable, making it harder to recognise the point at which true fatigue sets in

As a result, when training with lighter weights, it may be beneficial to push closer to muscle failure to make sure the muscle fibers are fully activated.

Velocity Loss

When looking into different velocity loss thresholds, the review found that greater losses in repetition speed (more than 25%) tended to produce better muscle growth compared to smaller losses (25% or less).

Similarly, when athletes trained with velocity losses between 20% and 50% ( an indication that they were getting closer to failure) their muscles generally grew more.

However, this relationship wasn’t perfectly linear.

It’s also worth noting that people can experience the same amount of velocity loss while being at different levels of proximity-to-failure, so this measure isn’t a perfect indicator.

In short, while training closer to failure or at higher velocity losses can support muscle growth, it doesn’t guarantee it.

3 Clinical Tips

1. Focus on Training Volume
Aim for consistent weekly set volume rather than training to exhaustion, as total work drives muscle growth more than reaching failure.

2. Match Effort to Load
With lighter weights, work closer to failure; with heavier loads, stopping 1–2 reps short is usually enough for similar benefits.

3. Use Speed as a Fatigue Guide
A noticeable slowing of movement (20–40% velocity loss) signals effective effort without needing to train to full failure

Top Resources to Check Out

And learn more about muscle growth

1. Muscle hypertrophy fully explained (E-book) - LINK

2. An visual explanation of what hypertrophy is

Meme of The Week

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