There’s an abundance of evidence showing that static stretching weakens muscles, making it the last thing you want to do as part of your warm-up.
A new study using technology that tested the degree of mechanical muscle signal during contraction following stretching found that peak force decreased significantly from pre-test measures. Researchers found that after stretching, force output decreased and stayed depressed for a two-hour recovery period after stretching, indicating the negative effects on performance are not short-lived.
Electromyographic data, a measure of the electrical potential of the muscle, was also gathered. Stretching didn’t change these results, indicating that neither the neuromuscular efficiency or motor unit of the muscle is hindered by stretching. Rather, it’s thought that the connective tissue and muscle fibers are lengthened resulting in decreased force production.
A second study found that static stretching of the quads and hamstrings decreases the hamstring-to-quadriceps ratio. This ratio is essential for speed and power production of the lower body because the hamstring works to stabilize the knee and help control the powerful leg motion that is generated by the quadriceps. A modified strength ratio from a muscle imbalance or improper rehabilitation of the hamstring after injury has shown to increase injury risk 17-fold.
The take away is twofold:
1) Do a dynamic warm-up to prepare for peak training or sports performance.
2) Save static stretching for post-workout or off days.