Acute Effect of Constant Torque and Angle Stretching on Range of Motion, Muscle Passive Properties, and Stretch Discomfort Perception

Abstract

The aim of the present study was to compare the acute effects of constant torque (CT) and constant angle (CA) stretching exercises on the maximum range of motion (ROMmax), passive stiffness (PS), and ROM corresponding to the first sensation of tightness in the posterior thigh (FSTROM). Twenty-three sedentary men (age, 19-33 years) went through 1 familiarization session and afterward proceeded randomly to both CA and CT treatment stretching conditions, on separate days. An isokinetic dynamometer was used to analyze hamstring muscles during passive knee extension. The subjects performed 4 stretches of 30 seconds each with a 15-second interval between them. In the CA stretching, the subject reached a certain ROM (95% of ROMmax), and the angle was kept constant. However, in the CT stretching exercise, the volunteer reached a certain resistance torque (corresponding to 95% of ROMmax) and it was kept constant. The results showed an increase in ROMmax for both CA and CT (p < 0.001), but the increase was greater for CT than for CA (CA vs. CT in poststretching, p = 0.002). Although the PS decreased for both CA and CT (p < 0.001), the decrease was greater for CT than for CA (CA vs. CT in poststretching, p = 0.002). The FSTROM increased for both CA and CT, but the increase for CT was greater than that for CA (CA vs. CT in poststretching, p = 0.003). The greater increase in ROMmax for the CT stretch may be explained by greater changes in the biomechanical properties of the muscle-tendon unit and stretch tolerance, as indicated by the results of PS and FSTROM.

Acute effects of constant torque and constant angle stretching on the muscle and tendon tissue properties

“…Similar to results from previous studies that used CA (Herda et al 2011, 2014; Cabido et al 2014; Konrad et al 2016) and CT (Herda et al 2011, 2014; Cabido et al 2014; Morse et al 2008; Kato et al 2010) stretching protocols, RoM increased following both CA and CT stretching. However, when looking at those studies that made a direct comparison of the effects of the two stretching modalities on RoM (Herda et al 2011, 2014; Cabido et al 2014), some differences arise.…”

“…However, when looking at those studies that made a direct comparison of the effects of the two stretching modalities on RoM (Herda et al 2011, 2014; Cabido et al 2014), some differences arise. For example, Herda et al (2011, 2014) found no difference in the effects of CA and CT stretching on the RoM, while both Cabido et al (2014) and our results showed a significantly greater improvement in RoM following CT stretching. This was further supported by Yeh et al (2007), who compared CA and CT stretching in stroke patients with ankle hypertonia and also found a higher RoM gain in CT stretching compared to CA stretching.…”

“…During the CA stretching exercise, the subjects were asked to regulate the motor of the dynamometer with a remote control to get into a dorsiflexion (stretching) position corresponding to 95% of the maximum RoM (Cabido et al 2014) determined during the RoM measurement, with the help of visual feedback. This position was held for 30 s. For the CT stretching, the subjects were asked to regulate the dynamometer to reach the individual PRT corresponding to 95% of the maximum RoM (Cabido et al 2014). The torque values were provided on a monitor in front of the subjects, and whenever the torque curve decreased by 2 Nm (marked as a line), the volunteer increased the dorsiflexion angle to maintain CT.…”

“…Concerning stretching intensities/modalities, only a few studies (Herda et al 2011, 2014; Cabido et al 2014) have compared the effects of constant angle (CA) stretching (the position is held at a constant joint angle) and constant torque (CT) stretching (where the torque during the stretching is held constant by increasing the joint angle). When a joint is held at a constant angle, passive torque will decrease due to the viscoelastic behavior of the muscle–tendon structure (Magnusson et al 1996).…”

“…However, other parameters such as maximum voluntary contraction (MVC) (Herda et al 2011), RoM, and PRT (Herda et al 2011, 2014) are similarly affected. Cabido et al (2014) reported that muscle–tendon stiffness and RoM were influenced by both CA and CT stretching; however, greater reductions in muscle–tendon stiffness and greater increases in RoM were observed following CT stretching compared to CA stretching.…”