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 · m(2)). 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.
Keywords: angle; flexibility; hamstring; time under stretch; torque.
© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.