Is Training to Failure Enough?

Welcome to the Training Takeaway Newsletter by Data Driven Strength! Zac Robinson here.

The proximity to failure of a set seems to influence the stimulus for muscle growth. However, this concept is usually discussed in the context of full range of motion (ROM) training. With the findings of a recent preprint by Larsen and colleagues, it may be time to revise the way we define proximity to failure - potentially taking into account the ROM in which momentary failure occurs.

Study Overview:

The study by Larsen and colleagues employed a unique study design. 23 untrained participants had their lower limbs randomized into one of two conditions:

1. Full ROM Failure - each set was performed until the participant could not complete a “full” calf raise (i.e., maximal plantarflexion)
2. Partial ROM Failure - each set was performed until the participant could not complete a “partial” calf raise (i.e., maximal dorsiflexion)

The participants trained the Smith machine standing calf raise twice a week for 10 weeks, with 3-4 sets per session per limb. Measurements were taken 1 week before and after the intervention and averaged, such that a single observation per participant contributed to the analysis.

Results:

The authors found that growth of the medial gastrocnemius meaningfully favored the partial ROM failure condition (0.62 mm [95% CrI: 0.21 ,1.0]). Importantly, this estimate had a 99.8% probability of exceeding zero (i.e., no difference between conditions) and I calculated an 88.6% probability of exceeding their typical error of measurement achieved at baseline. I’d expect these probabilities to be even higher if all ultrasound scans were included in their statistical models, rather than taking the average. Thus, I think there is very likely something going on here that is worth considering.

From a practical perspective, it's tough to know which of the following uncontrolled factors are leading to this difference between conditions:

1. Greater total training volume due to the additional partial repetitions
2. Greater exposure to the lengthened position of the muscle
3. Greater relative stimulus of a close proximity to “true” failure

All of these are reasonable explanations, and all likely contribute to some degree, but how this study inspires a potential reframing of the concept of proximity to failure is what I find most interesting. Typically, we define proximity to failure as the number of repetitions in reserve (RIR) relative to the point in which a given task cannot be completed despite maximal effort to do so - or what we can call momentary failure. However, this study questions the appropriate definition of “the task”. If we are unable to perform additional full ROM reps but have plenty of partial reps in the tank (particularly in the lengthened position of a muscle), it may be worth continuing the set to get to a “true” failure point in which the implement cannot be moved at all. In this way, proximity to failure may be best viewed as the percentage of force capacity that is remaining at the limiting joint angle of the muscle:

Conceptually, these additional partial repetitions would provide some stimulus due to a combination of the i) additional training volume, ii) if applicable, greater exposure to the lengthened position of a muscle, and iii) potentially greater relative stimulus of reps performed in close proximity to “true” failure. From an ecological validity perspective, I find this a compelling approach to increase the stimulus per set with minimal additional time investment. Of course, it’s worth considering the potential downstream implications of this approach. In theory, these additional repetitions will come with fatigue and may potentially impair your ability to psychologically gauge your proximity to failure due to the increased perception of discomfort. That said, I always view these types of concerns as IF / THEN statements. IF you find your ability to tolerate a given amount of training volume is meaningfully impaired, THEN it may be worth considering making an adjustment. Similarly, IF you find that psychological ability to train progressively for the rest of your session is negatively impacted, THEN you may want to reserve this approach for later in the session or only some exercises.

Ultimately, more work is needed to tease out exactly what is going on here (e.g., does this play out in other muscles?), but as a first step - I think this a very intriguing concept that may further expand how we think about proximity to failure and ultimately inform our training prescriptions.

In the meantime, I think there are 3 major scenarios where performing your sets to partial ROM failure makes sense:

1. If the exercise is very challenging in the shortened position (e.g., most back training)
2. You’re short on time
3. You’re looking for easy ways to increase the dosage of training for stubborn areas

Takeaway:

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