Stretching the muscles before physical activity or sports has long been a commonplace among athletes and exercisers. Stretching loosens the muscle, increases blood flow and is thought to reduce injury and condition the muscle for better performance. Research has now shown that while stretching before some activities is beneficial, before many others, it is detrimental. Before plyometric activities (exercises such as jumping and quick explosive movements under minimal resistance), for example, stretching has been shown to have a synergistic effect and reduce the risk of injury by protecting the joints. This can be translated into benefits in other applications where sudden quick (plyometric-like) movements make the joints vulnerable, such as soccer, football, agility drills etc. However, in instances such as weight training, jogging, cycling, and activities where movements are slightly more controlled, stretching actually makes the muscles more vulnerable to injury. Not only that, stretching before weight training actually decreases strength and performance. For weight training purposes, alternative stretching techniques where antagonistic muscles are stretched and post workout stretching of the target muscle are a much better choice.
Stretching pre-workout has the effect of relieving tension from the muscle and joint and elongating the muscle cells. While stretching feels good and does in fact increase blood flow to the muscle, the fact that it loosens the muscle makes it unstable, and an unstable muscle is a muscle more vulnerable to injury. Also, research has shown that stretching a muscle pre-weight training has a profound negative effect on strength and stability. A 2013 study from Department of Kinesiology and Health Science at Stephen F. Austin State University in Nacogdoches, Texas measured the one repetition maximum lift on squats of a group of young men. Results were gathered at two different times, one after stretching the legs pre-lift and one with just a dynamic warm up of the muscles. Their goal was to determine not only the one repetition maximum squat, but also the athletes’ perceived stability during the lift. What they found was that after stretching, one repetition max decreased by 8.36% compared to when they warmed up but did not stretch. This is not unlike the act of relieving tension on a rubber band. A tight rubber band is tense and loaded with energy, whereas a loose rubber band has much less potential energy and is capable of much less force. Similarly, perceived stability in the lift decreased by 23% after stretching. There is also evidence that stretching pre-workout causes athletes to fatigue quicker. Stretching itself has some similar effects to training the muscle in that it causes tension and slight muscle damage under high tension. For this reason, the act of stretching itself fatigues the muscle and decreases the time until the muscle is fully fatigued.
For many of the same reasons stretching the target muscle is detrimental, stretching the antagonistic (or opposite) muscle to what you are training before and during training has benefits. For instance, if you are about to train your biceps, stretching the triceps will reduce the tension on the triceps and place more focus on the biceps, allowing them to bear more of the load. A tight triceps opposite a biceps will have a counterbalance effect much like that of a seesaw. As the biceps pulls one way, a tight triceps will affect the movement of the biceps and take some emphasis away from the targeted muscle. Stretching the antagonistic muscle first will place more emphasis on the target muscle and also, activate more muscle cells as the amount of support and guidance lent by the triceps is reduced, forcing the biceps to bear more of the load. This mechanism of action is even more pronounced for larger muscle groups like chest versus back muscles.
After the workout is completed and the muscle is fatigued, pumped with blood and loaded with lactic acid, this is now a great time to stretch it. No further movement is required from the muscle and the fact that it is pumped with blood increases the effectiveness of the stretching by further expanding the inner tension on the muscle cells. Stretching post workout cycles blood in and out of the muscle and in turn alleviates the buildup of lactic acid. Not only that, since stretching itself fatigues the muscle and is similar to a workout, stretching post workout can actually increase the rate of muscle hypertrophy (muscle growth) and speed up recovery. Stretching a fatigued, weak and blood engorged muscle activates more muscle satellite cells and fully exhausts whatever life the muscles have left in them, leading to more growth and more complete recovery.
Stretching will continue to be a big part of all athletics and training routines. It is important to know when to do it and how to do it for your particular application. For weight training purposes, pre-workout stretching both weakens and fatigues the muscle and makes them more vulnerable to injury. Stretching the antagonistic muscle before and during a workout helps place more focus on the target muscle, while stretching the muscle post-workout has a number of benefits as well. Try just a light warm-up of the target muscle pre-workout next training session and incorporating these stretching techniques into your regimen. You will be stronger, less prone to injury and will grow faster as well.