The question of whether stretching a muscle sore from a previous workout can enhance muscle growth is a common point of confusion for many who exercise. The soreness felt a day or two after a challenging session is known as Delayed Onset Muscle Soreness (DOMS). While DOMS often feels like a sign of a good workout, its relationship with muscle size gain, or hypertrophy, is not a simple direct link. Understanding the biology of soreness and growth is necessary to determine if stretching is a tool for building muscle or simply temporary comfort.
Understanding Muscle Soreness
Delayed Onset Muscle Soreness (DOMS) is the tenderness, stiffness, and aching sensation that typically begins 12 to 24 hours after intense exercise, peaking between 24 and 72 hours later. This state is primarily triggered by training involving a high degree of eccentric contractions, where the muscle fibers lengthen while under tension.
Mechanical stress causes micro-tears, or micro-trauma, within the muscle fibers and surrounding connective tissue. The body responds to this micro-trauma with a localized inflammatory process, which is the actual source of the delayed pain. DOMS is not caused by lactic acid buildup, but rather by the subsequent inflammatory cascade. DOMS is a symptom of muscle damage and the resulting repair process.
How Muscles Achieve Growth (Hypertrophy)
Skeletal muscle hypertrophy, the increase in muscle fiber size, is an adaptation driven by three main mechanistic stimuli. The first is mechanical tension, achieved by lifting heavy loads and generating force across the muscle, which activates signaling pathways, such as the mTORC1 pathway, promoting new muscle protein synthesis. The second mechanism is metabolic stress, often referred to as “the pump,” which results from metabolite accumulation during high-volume training, creating a cell swelling environment that signals an anabolic response. The third mechanism is muscle damage, the micro-trauma that leads to DOMS, which serves as a necessary stimulus for the muscle to repair itself stronger and larger. The repair process involves an increase in muscle protein synthesis, resulting in an increase in the cross-sectional area of the muscle fiber. Without mechanical tension and sufficient metabolic stress, muscle damage alone primarily leads to repair without significant growth.
Stretching Sore Muscles and Hypertrophy
When a muscle is already sore from exercise-induced micro-trauma, applying a stretch does not enhance the signaling pathways for hypertrophy. Gentle stretching of damaged tissue does not generate the high, sustained mechanical tension required to maximize the mTORC1 pathway for growth. The act of stretching a sore muscle is primarily a palliative measure that addresses the perception of tightness, not a potent anabolic stimulus.
Research on a concept known as stretch-mediated hypertrophy suggests that stretching can stimulate growth, but this requires specific, intense, and prolonged protocols. These methods often involve heavy, weighted stretching or long-duration static holds (sometimes for 30 minutes or more per session) that create a high level of mechanical tension, distinct from a typical post-workout stretch for soreness. Applying this aggressive stretching to a muscle compromised by DOMS may be counterproductive. Introducing further mechanical stress to inflamed tissue can delay the natural repair process, potentially prolonging soreness and recovery time. Therefore, stretching is not a direct or effective means to promote greater muscle growth for the average person experiencing typical DOMS.
The Role of Stretching in Recovery and Mobility
While stretching sore muscles does not promote hypertrophy, it offers well-documented benefits related to recovery and muscle function.
Mobility and Flexibility
The primary physical benefit of stretching is an increase in the joint’s range of motion (ROM) and overall flexibility. Maintaining or improving flexibility is crucial for performance and reducing the risk of injury in subsequent workouts.
Temporary Relief and Circulation
Stretching can provide temporary relief from the stiffness and tightness associated with DOMS by increasing blood flow to the affected area. This improved circulation helps deliver nutrients required for repair and may assist in the removal of metabolic byproducts.
Types of Stretching
When dealing with soreness, dynamic stretching, which involves movement like leg swings or arm circles, can be a form of active recovery that promotes blood flow without overstressing the tissue. Static stretching, where a position is held for a period, is best used gently after a workout to reduce muscle tension, but it has not been shown to reduce the severity or duration of DOMS itself.