The stiff, aching sensation that arrives a day or two after a challenging workout is often seen as a definitive sign of success. This discomfort, known as Delayed Onset Muscle Soreness (DOMS), has become a commonly accepted measure of an effective training session. The belief is simple: if your muscles are not profoundly sore, then the workout was not hard enough to stimulate growth. Understanding the science behind DOMS and muscle growth, or hypertrophy, reveals that this connection is not as straightforward as many assume.
Debunking the Soreness Myth
The short answer to the question of whether you are still building muscle without soreness is a clear yes. Soreness is a poor metric for gauging the success of a resistance training session aimed at increasing muscle size. While intense DOMS often follows a particularly strenuous or novel workout, the intensity of this soreness has a weak correlation with long-term muscle gain.
Muscle soreness is a side effect of training, not the goal. Excessive soreness can be counterproductive, as it may reduce muscle activation and force capacity in subsequent workouts, potentially hindering long-term progress.
As a person continues with a consistent training routine, the body undergoes a rapid adaptation process known as the repeated-bout effect. This adaptation causes a significant reduction in the severity of DOMS, even if the training intensity remains high and the muscle continues to grow. An experienced lifter who consistently challenges their muscles may rarely experience significant soreness, yet they continue to see progress because their body has adapted to the training stimulus.
The True Triggers of Muscle Hypertrophy
Muscle hypertrophy is primarily driven by three distinct mechanisms that signal the muscle to increase protein synthesis and grow larger. The first and most influential mechanism is mechanical tension, which is the physical force placed upon the muscle fibers. This tension is best generated by lifting heavy loads and performing movements through a full range of motion, with consistent increases in weight, repetitions, or volume over time—a principle known as progressive overload.
The second mechanism is metabolic stress, often experienced as the “pump” or burning sensation in the muscle during high-repetition sets. This stress involves the accumulation of metabolic byproducts, like lactate, which cause cell swelling and can trigger anabolic signaling pathways. This swelling creates pressure on the muscle cell membranes, signaling a need for adaptation and growth.
The third mechanism is muscle damage, which refers to the microscopic tears and structural disruption to the muscle fibers caused by intense exercise. While this damage is one component of the growth process, research suggests it may only be a weak contributor compared to mechanical tension. Focusing purely on causing damage to maximize soreness is unnecessary, as the most effective training programs incorporate elements that stimulate all three mechanisms without requiring debilitating pain.
What Causes Delayed Onset Muscle Soreness (DOMS)?
Delayed Onset Muscle Soreness is a phenomenon that typically peaks between 24 and 72 hours after unaccustomed or strenuous physical activity. The underlying cause is not the buildup of lactic acid, which clears from the muscles quickly, but rather a sequence of physiological events. DOMS is most strongly associated with exercise that involves eccentric muscle contractions, where the muscle lengthens while under tension, such as the lowering phase of a squat or bicep curl.
This type of action creates microtrauma, or small-scale damage, to the muscle fibers and surrounding connective tissue. In response to this mechanical damage, the body initiates an inflammatory process. Immune cells migrate to the area, and fluid shifts occur, leading to temporary swelling within the muscle tissue. This localized edema and the presence of inflammatory byproducts irritate the free nerve endings, which the brain interprets as the dull, aching pain characteristic of DOMS. The presence of DOMS is primarily a sign that the body was subjected to a novel stimulus, not an absolute prerequisite for hypertrophy.