A new study compared how different loads, different exercises, and different levels of proximity to failure affect muscle fatigue, perceived heaviness, and metabolic stress after a strength workout. The takeaway is simple: there’s no universal ‘right’ approach—which is great news if you dread failure like the plague.

What exactly was studied

Researchers compared different variations of strength training: different loads on the bar, different exercises, and different numbers of reps left ‘in the tank’ before failure (known as RIR—reps in reserve). They looked at three things: how the muscles and nervous system fatigue right after the workout and in the following days, how heavy the set feels subjectively, and what kind of metabolic response the load produces—that burning sensation and buildup of metabolic byproducts in the muscle.

The idea is that a workout isn’t just ‘lifted the bar’—it’s a combination of several variables that load the body in different ways. Change just one of them, and the body’s whole response shifts.

Why ‘to failure’ isn’t the gold standard

The fitness industry has long sold the idea that if you didn’t collapse under the bar, you didn’t really work. In reality, different levels of proximity to failure produce different fatigue and different recovery. A set stopped a couple reps short of the limit loads the muscle differently than a set taken all the way to failure—and the body recovers from each at a different pace.

This means training to failure isn’t automatically ‘more effective.’ It’s simply different in its physiological cost. And for someone training three or four times a week while juggling a job, kids, and leftover sleep, the accumulated fatigue from constant failure sets can end up costing more than the apparent benefit.

Different exercises, different ‘price tags’

Another key point: even at the same proximity to failure, different exercises tax the body unequally. Heavy multi-joint movements typically demand a longer nervous system recovery than isolated machine exercises. Worth factoring into your weekly planning—if you just ground out a heavy deadlift to the limit, don’t expect your body to be ready for explosive work the next day.

How to apply this in the gym

The practical takeaway is simple: proximity to failure is a tool, not a badge of effort. It makes sense to keep some sets at 1-3 reps in reserve—this lets you maintain technique quality, avoid piling up excess fatigue, and train more often. Save true failure for select, purposeful sets rather than turning it into a habit for every single set.

Pay attention to how you feel: if the burn and heaviness in your muscles linger longer than usual after a workout, and the next session feels like a slog, that’s a signal the volume or proximity to failure was too much for your current recovery capacity.

Source: PubMed / J Sports Sci