Do You Need to Train to Failure? What Research Reveals About Intensity

The "no pain, no gain" mentality runs deep in fitness culture. Many people believe that unless you're grinding every set until you physically can't complete another rep, you're leaving gains on the table.

But is training to complete failure actually necessary? And could it be slowing your progress?

What the Research Shows

Scientists compared two approaches to resistance training: training to momentary muscular failure (pushing until you physically cannot complete another rep) versus a "reps in reserve" (RIR) approach (stopping a few reps short of failure).

At the end of the study, both groups experienced similar muscle growth.

Pushing every set to absolute failure wasn't required to build muscle. Stopping a few reps before failure produced comparable results.

However, there was an important difference worth noting:

The failure group experienced significantly more muscle fatigue, which meant longer recovery times and a higher risk of burnout.

Meanwhile, the group that stopped short of failure recovered faster and maintained higher training quality over time.

The Recovery Problem

Training to failure creates significant fatigue—not just in the muscle you're training, but systemically. This fatigue has consequences:

Reduced training quality. If you're exhausted from failure training on Monday, your Wednesday workout suffers. You can't train as hard when you're still recovering.

Accumulated stress. Training to failure on every set, every workout, every week creates mounting fatigue that can lead to overtraining and burnout.

Injury risk. Form tends to break down at failure. Grinding out reps with compromised technique increases injury risk.

Diminished returns. The muscle growth from that final failure rep may not be worth the recovery cost it imposes.

The failure group in the study grew similar muscle but paid a higher recovery tax for it.

The Practical Approach

Based on this research, here's how to train effectively:

Push yourself hard—but leave 1 to 2 reps in the tank on most sets. This means your rep speed should slow down, and you should strain on your final reps, but you could have completed one or two more if forced.

Use failure strategically, not constantly. Occasional failure sets can be useful, especially for testing your limits or on isolation exercises. But failure on every set of every workout is unnecessary.

Maintain good form throughout. If your form is breaking down, you've gone too far. The quality of each rep matters.

Know what failure feels like. To use reps in reserve effectively, you need to calibrate your sense of how close you are to failure. Periodically take sets to actual failure (with appropriate safety precautions) to maintain accurate self-assessment.

How to Gauge Reps in Reserve

Knowing how many reps you have "in the tank" requires practice. Signs that you're approaching failure:

Rep speed slows significantly. When reps start taking noticeably longer, you're getting close to failure.

Strain becomes intense. You should feel like you're working hard on your final reps, even if you could technically do one or two more.

Form starts to shift. Subtle technique changes often precede failure. When you notice form degrading, stop the set.

A good guideline: if you're unsure whether you could complete another rep, you're probably at or near failure. Stopping there provides most of the stimulus without the full recovery cost.

When Failure Makes Sense

Training to failure isn't always wrong. It can be appropriate in certain situations:

Machine exercises. Safer for failure because you can't get stuck under a weight.

Isolation exercises. Bicep curls or lateral raises pose less systemic fatigue than compound movements taken to failure.

Final sets of an exercise. If you're doing multiple sets, taking the last set closer to failure is reasonable.

Periodically for calibration. Occasional failure sets help you understand your true limits so your "reps in reserve" estimates stay accurate.

Deload weeks approaching. If you have a lighter week coming up, pushing harder before the recovery break can be appropriate.

Avoid consistently training to failure on:

• Heavy compound movements (squats, deadlifts, bench press)
• Every set of every exercise
• When recovery is compromised (poor sleep, high stress)

The Quality Focus

Shifting away from constant failure training lets you focus on what actually drives growth: quality work over time.

Consistency matters more than any single workout. If training to failure on Monday means you skip Wednesday, you've lost more than you gained. Sustainable training that you can maintain week after week produces better long-term results than occasional heroic efforts followed by forced recovery.

The Bottom Line

Training to complete failure isn't necessary for muscle growth. Research shows that stopping 1-2 reps short of failure produces similar results while allowing faster recovery and better training quality over time.

Push yourself hard. The last few reps of each set should be challenging. But grinding every set until you can't move is unnecessary and potentially counterproductive.

Use failure strategically—for calibration, on safer exercises, or during peak training phases. But for most of your training, leaving a rep or two in reserve gives you the stimulus you need without the excessive fatigue that impairs subsequent workouts.

Use the AFT Calculator to track your strength progress, and remember that sustainable training consistency—not single-workout intensity—drives long-term improvement on events like the MDL and HRP.