When it comes to resistance training, the majority of hardcore lifters believe that you need to train muscle to failure, to achieve most. If don’t go to failure (or beyond) on each set, you aren’t doing your best. This is what they think. The purported benefits of all-out training aren’t relegated to gym rats; similar sentiments have also been echoed by exercise scientists, furthering claims that working to momentary muscular failure is crucial to maximize growth. But in spite of this notion being widely accepted as fact, evidence stays equivocal as to just how hard you really need to train for optimal gains.
The intensity of effort expended during a set can be estimated by how close you come to reaching muscular failure, which can be defined as the point where your muscles aren’t able to complete another full repetition without assistance.
The rationale for taking an all-out approach is predicated on the belief that it elicits recruitment of all available fibres in the target muscle. Full recruitment of all fibres is crucial for maximal hypertrophy; if you don’t recruit a fibre, it has no impetus to grow. But while fatiguing contractions have been shown to lead to a corresponding increase in surface EMG activity during low-load training, the impact diminishes with the use of progressively heavier loads.
What’s the reason? Fast-twitch fibres – the strongest, most powerful muscle fibres – are recruited almost instantly when lifting very heavy loads, because high levels of force are needed from the onset of the set. This is in contrast to light-load training, where engagement of the strongest fibres (type IIx) is delayed because extensive force isn’t initially needed to lift the weight. As a light-load set becomes more fatiguing, additional fibers are then engaged to maintain force output. Based on this information, it seems the necessity to train to failure is much less relevant when using heavy loads. One study also examined whether runners should use light weights or heavy barbells to get most optimal results.
It’s also been speculated that training to failure augments muscular growth by increasing metabolic stress. There’s ample evidence that the build-up of metabolites—breakdown products from energy production—improves the anabolic response to resistance training. It’s seems logical that continuing a set to the point of fatigue will necessarily heighten energy demands, and therefore lead to a greater metabolite accumulation. This seemingly supports a beneficial effect of pushing your sets to the max. Nevertheless, it’s not clear whether the additional metabolic stress produced during an all-out set results in a meaningfully greater accretion of muscle proteins, in comparison with a set stopped short of failure. It’s conceivable that there’s a threshold for metabolic stress beyond which no further beneficial effects are realized.
There’s surprisingly few studies investigating the hypertrophic effects over time of going to failure, in comparison with training with lesser intensities of effort. An often-cited study in support of failure training compared muscle growth in recreationally trained men doing a multiple-set protocol of 10 reps with 60 seconds rest between sets. Workouts included the lat pull-down, shoulder press and leg extension. The wrinkle here was that one group carried out all sets continuously to failure, while the other group had a 30-second rest at the mid-point of each set.
As you’d probably expect, the group training to failure gained significantly more muscle over the course of the 12-week study than the group taking a break during sets. While the outcomes are interesting, they in no way replicate traditional non-failure training protocols where sets are stopped a rep or two from fatigue. What one could say is the study shows it’s detrimental to stop training for a half-minute in the middle of a moderate-rep set; not an earth-shattering finding.
A recent study sought to compare the results of working to failure in a more traditional resistance-training setting. Twenty-eight untrained young men carried out four sets of arm curls at 85% of their one-repetition maximum (1RM). Participants were randomized either to carry out sets to failure using a 2-second concentric and 2-second eccentric action, or to stop about two reps prior to failure while employing either rapid shortening (explosive concentric and 2-second eccentric action) or stretch-shortening (explosive action on both concentric and eccentric movements). After 12 weeks, the average gain in biceps muscle cross-sectional area was about 11 % for all participants combined, but no significant differences were obvious between groups.
A key point to remember here is that participants trained with heavy loads equating to a 6RM. It therefore one could suggest that training to failure becomes less important when using heavy weights, which is in line with the before mentioned research on muscle activation. The study did have a potential confounding issue: the non-failure groups actually carried out a single set to failure at the end of every week to determine loading for the subsequent week. Whether this had a significant impact on results is anyone’s guess. It’s essential to understand that regular training to failure over the long term does have a potential downside. Namely, it increases the risk of overtraining and psychological burnout.
Another study discovered that resting levels of anabolic hormones (IGF-1 and testosterone) were decreased in a group of physically active men when they consistently worked to failure over the course of a 16-week resistance-training program. A reduction in resting anabolic hormonal levels is indicative of an overtrained state, suggesting a negative impact of repeatedly going all-out on every set.
Based on the limited research, the benefits of training to failure seem to depend on the magnitude of load lifted. With heavy loads (say, above 80% of your 1RM), there doesn’t seem to be much need to carry out every possible rep of a set; you’ll achieve most, if not all, muscular benefits even by stopping a rep or so prior to failure. On the other hand, when utilizing loads lighter than 80% of your 1RM, it’s safe to say that at least some sets should be carried out to failure, given the clear relationship between the proximity to failure and muscle activation during low-load training. What’s important is that you avoid the temptation to go all-out all the time, because this increases the potential for systemic overtraining. Maybe the best strategy is to periodize how often you go to failure. In this way, you’ll maximize muscular adaptations while avoiding the negative complications of an overtrained state.