Debunking Fitness Myths: Stretching
Dating back to the early 1980s, the practice of static stretching before exercise was widely believed to prevent or reduce the risk of injury, and to promote performance. Thirty years later and after volumes of research, confusion still exists whether it offers potential benefits before exercise. From a logical perspective, tissue stiffness and a lack in range of motion (ROM) both contribute to injury, and static stretching is correlated with both a reduction in tissue stiffness and an improved ROM. While this statement may speak to the benefits of static stretching, we must remember that “correlation” does not imply “causation” (i.e., that static stretching does reduce injury). More recently, studies investigating the effects of static versus dynamic stretching on force and power production have almost all consistently demonstrated significant reductions in muscle strength and power production following static stretching versus dynamic stretching (Sekir, et al., Scandinavian Journal of Medicine & Science, 2010; Rossi, et al., Human Movement, 2010). In fact, a meta-analysis of 350 studies reviewed by the Centers for Disease Control found no evidence that linked static stretching before exercise with reduced risk of injury.
As training philosophies continue to shift from muscle isolation towards whole-body integration, it draws attention to whether muscles should be “turned off” (inhibited) or “turned on” (activated) during the pre-exercise or warm-up phase. Traditional static stretching subscribes to Autogenic Inhibition to achieve increased tissue extensibility, relying upon the activation of Golgi Tendon Organs (GTO) after 7 to 10 seconds of holding an isometric stretch at the point of tension. This activation inhibits muscle spindle activity, turning off neural and muscle activity to promote connective tissue elongation. However, if movement requires muscle activation, then why consider turning off muscles before exercise? Additionally, after approximately 5 seconds of developing a stretch tension, muscles may experience decreased localized blood flow and therefore some ischemia (due to reduced O2), potentially increasing lactate manufacture and accumulation that may induce faster muscle fatigue. On the other hand, arguments made in support of static stretching before exercise make some valid points:
- Static stretching can lower blood cortisol levels that usually spike during early exercise – cortisol blunts testosterone action and may potentially reduce muscle growth.
- Is whole-body dynamic movement appropriate for new or de-conditioned individuals who lack adequate levels of stability and mobility initially?
While the body’s chronic adaptations to the stress of exercises will, over time, reduce our cortisol responses, the argument over appropriateness is quite valid. Consequently, practitioners should consider utilizing different stretching modalities specific to the conditioning level and needs of their clients or athletes (e.g., myofascial release and static stretching before exercise in new exercisers; myofascial release and dynamic movement in conditioned individuals; myofascial release and ballistic movements in explosive athletes).
The post-exercise component of the workout is aimed at improving tissue extensibility, thus should include myofascial release, static stretching and even some PNF stretching. Another widely-held belief is that stretching post-exercise will prevent muscle soreness related to DOMS (delayed onset of muscle soreness). Unfortunately, while not quite true as the micro-trauma to muscle tissue has already occurred during exercise, it does reduce the magnitude of muscle discomfort and may also accelerate tissue recovery.
Regardless of what stretching modality one follows, a common mistake made by many is the lack of attention to differentiating between mono-articulate (one joint) muscles and bi-articulate (two joint) muscles. What many perceive to be extension within the muscle tissue may in fact only be movement of the joint (e.g., lying hamstring stretch where the pelvis rotates posteriorly as the hamstrings are stretched). Fitness professionals aiming to improve tissue extensibility must stabilize or immobilize one end while moving the other end or move both ends in opposite directions to achieve results.
Fascial training, while not new, but often neglected in stretching is gaining popularity and deservingly so. Once we recognize the fact that most soft tissue injuries are related to connective tissue (fascia) and not muscle tissue, then modalities such as myofascial release gain relevance. A myofascial net (considered more than just shrink wrap around the body) envelops our body and contains nerve and blood vessels, along with over 10 times the number of sensory receptors found in muscle. Consequently, this tissue is highly active and subject to trauma and impingement due to overuse, underuse, or even poor posture that impairs nerve activity and localized blood flow, creating local ischemia, pain (acute or chronic, and in the immediate or other areas) and loss of muscle function. A stretching program should always include myofascial release both before and after to reduce tightness and promote normal function, especially in problematic areas (e.g., hip flexors / IT band, calf complex). Additionally, the warm-up phase should also include some fascial training to properly prepare the body for activity. Fascial elasticity explains how this tissue can store and return energy during cyclical movement patterns where loading and unloading occur quickly (e.g., walking, running) and contribute to strength and power output (even controlled bouncing movements can build elasticity and improve performance). Fascial training responds effectively to variety opposed to repetition by changing loading angles, tempo and even load, and is best trained using whole-body movements that activate our myofascial chains.