How do long, intense static stretching sessions affect strength, muscle thickness, and range of motion?
There is plenty of research on static stretching, most of it looks at stretches for a duration of 5 minutes or less. Some research on long-lasting stretching (LLS) has resulted in hypertrophy and increases in maximal strength in animals and humans. Warneke and his team hypothesized that LLS at a higher intensity will create enough mechanical tension to lead to muscle hypertrophy and increased strength in humans. In this study, they increased the intensity of the stretch and duration to an hour a day every day. They also measured muscle thickness with MRI (magnetic resonance imaging) in addition to sonography because MRI is the gold standard in precision and reliability when assessing hypertrophy.
Forty-five people participated. Those in the intervention group passively and intensely stretched their plantar flexors for an hour a day (6 sets of 10-minute reps) for 6 weeks.