When the researchers retested the participants at the end of the programme, they found that the training group had significantly improved their score on the sit and reach test, a standard test of flexibility, while the control group showed no improvement.
While this study does have limitations - all the subjects were over 60, they had no training history, and the sit and reach test measures just one area of flexibility - it is nonetheless significant. Indeed, subsequent studies have duplicated these results across a much wider range of flexibility tests.
Researchers have thus concluded that resistance exercises performed through a full range of motion promote increased flexibility.
If you think about the sports that use weight training as a major part of their conditioning program (athletics, rugby, American Football), that should really come as no surprise. These are all sports that demand a combination of strength, power, speed, flexibility and coordination - if the weight training made these athletes stiff and injury prone, they would not be able to perform at such high levels.
