Does the Expectancy on the Static Stretching Effect Interfere With Strength-Endurance Performance?

Bertolaccini, AL, da Silva, AA, Teixeira, EL, Schoenfeld, BJ, and de Salles Painelli, V. Does the expectancy on the static stretching effect interfere with strength-endurance performance? J Strength Cond Res 35(9): 2439-2443, 2021-Static stretching (SS) may interfere with strength performance. Such interference, however, may be partially attributed to the subjects' or researcher's expectancy about the SS effects. We aimed to examine whether the manipulation of subjects' expectancy of SS on force production could influence strength-endurance during unilateral knee extension exercise. Eighteen strength-trained men were randomly divided into positively biased (PB; N = 9) or negatively biased (N = 9) groups on the possible effects of SS on performance. Subjects' total number of repetitions and total volume of exercise were assessed during strength-endurance tests (4 sets performed to failure at 70% of 1 repetition maximum) performed under 2 different conditions on separate days: Control-no stretching (CON); or SS. Static stretching consisted of 3 sets of 3 stretching exercises, lasting 30 seconds each. Data were analyzed using mixed models. Neither the total number of repetitions nor the total volume was significantly different between the CON and SS conditions, nor for type of bias (all p > 0.05). However, the number of repetitions in the last set of exercise was greater during SS compared with CON for the PB group (p = 0.01). Although previous negative or positive information about SS did not interfere with the total number of repetitions and total volume of exercise, previous positive information about SS improved performance in the last set of exercise. Expectancy therefore may have played a partial role influencing strength-endurance in previous studies.