The concept of training intensity is one of the most debated topics in resistance training, especially for those seeking to maximize muscle growth. Many lifters and coaches advocate for pushing every set to the limit, a technique known as “lifting until failure.” While often seen as a sign of effort, its effectiveness and necessity are frequently questioned by scientific evidence. Understanding the nuances of intensity is necessary to build a sustainable and productive training plan. This article clarifies whether training to failure is beneficial or detrimental to long-term gains.
Defining Training to Failure
In resistance training, “training to failure” means reaching a point where no further repetitions can be completed. This concept is broken down into two states: technical failure and mechanical failure.
Technical Failure
Technical failure occurs when you can no longer perform a repetition with the correct form, even if the muscle still has strength left. This breakdown often involves using momentum or other muscle groups to complete the movement, signaling the need to stop the set.
Mechanical Failure
Mechanical failure is the point where the targeted muscle is physically incapable of contracting to lift the weight through the full range of motion. The muscle simply cannot generate the force needed for another concentric (lifting) action. Training intensity is often quantified using the Reps in Reserve (RIR) scale, where zero RIR (0 RIR) indicates the set was taken precisely to mechanical failure.
Muscle Growth and the Necessity of Failure
Muscle growth, or hypertrophy, is driven by high mechanical tension, which requires the recruitment of maximum motor units. Motor unit recruitment increases as a set progresses and the muscle fatigues. It is commonly believed that reaching failure is the only way to ensure all high-threshold motor units are engaged, maximizing the growth stimulus.
Current research suggests that training to failure may not be necessary for optimal muscle gains. Studies comparing training at 0 RIR (failure) with training at 1 to 3 RIR (near failure) show similar increases in muscle size and strength when total training volume is matched. Stopping just short of failure appears sufficient to recruit the necessary muscle fibers.
Training to failure generates high acute fatigue, which limits the total effective training volume performed across a workout or week. This elevated fatigue may reduce performance in subsequent sessions, potentially hindering long-term progress. While failure provides a strong stimulus, the recovery cost can outweigh the marginal benefit of the last repetition.
Practical Considerations and Injury Risk
Applying training to failure depends heavily on the specific exercise. It is discouraged to take heavy, multi-joint, compound movements like squats, deadlifts, or overhead presses to mechanical failure. Reaching failure on these exercises increases the risk of technical breakdown and injury, as stabilizing muscles fail under a heavy load. Even technical failure should be avoided, as practicing with poor form reinforces unsafe movement patterns.
Training to failure is better suited for low-skill, single-joint, or isolation exercises, such as bicep curls, triceps extensions, or lateral raises. These movements involve lighter weight and less complex coordination, making the consequences of failure much lower. The frequency of training to failure also affects recovery, as it induces a high degree of central nervous system (CNS) fatigue. This CNS fatigue can persist for a significant time and negatively impact the quality of subsequent workouts.
Monitoring Intensity Without Reaching Failure
For most lifters, a more sustainable approach is to manage intensity using the Reps in Reserve (RIR) or Rate of Perceived Exertion (RPE) systems. The RIR scale estimates how many repetitions you could have performed before reaching failure. For instance, stopping a set at 2 RIR means you ended the set knowing you could have completed two more repetitions with good form.
RPE is a related scale, typically ranging from 1 to 10, where 10 represents maximum effort or 0 RIR. Training consistently in the range of 1 to 3 RIR (RPE of 7 to 9) allows for a high training stimulus that maximizes motor unit recruitment. This avoids the disproportionate recovery demands of constant failure. This strategic submaximal effort facilitates greater total volume over time, which drives long-term muscle development. Lifters can use RIR and RPE to auto-regulate effort based on daily readiness, ensuring productive sessions while minimizing burnout and injury risk.