Responses to static stretching are dependent on stretch intensity and duration

Summary

Information regarding the effects of stretching intensity on the joint torque–angle response is scarce. The present study examined the effects of three static stretching protocols with different intensities and durations on the passive knee extension torque–angle response of seventeen male participants (age ± SD: 23·9 ± 3·6 years, height: 177·0 ± 7·2 cm, BMI: 22·47 ± 1·95 kg·m²). The stretching intensity was determined according to the maximal tolerable torque of the first repetition: fifty per cent (P50), seventy‐five per cent (P75) and the maximum intensity without pain (P100). Five repetitions were performed for each protocol. The stretch duration of each repetition was 90, 135 and 180 s for P100, P75 and P50, respectively. The rest period between repetitions was 30 s. Passive torque at a given angle, angle, stress relaxation, area under the curve, surface electromyography activity and visual analogue scale score were compared. The significant (P<0·05) results found were as follows: (i) the P50 and P75 did not increase the angle and passive peak torque outcomes, despite more time under stretch; (ii) only the P100 increased the angle and passive peak torque outcomes; (iii) the perception of stretching intensity mainly changed depending on knee angle changes, and not passive torque; (iv) the P50 induced a higher passive torque decrease; (v) when protocols were compared for the same time under stretch, the torque decrease was similar; (vi) the change in torque–angle curve shape was different depending on the stretching protocol. In conclusion, higher stretch duration seems to be a crucial factor for passive torque decrease and higher stretch intensity for maximum angle increase.