Abstract
PurposeStatic stretching induces acute structural changes of the muscle–tendon unit (MTU) that are related to the intensity or duration of stretching. It has been reported that stretching with a constant torque (CT) leads to greater joint range of motion changes than stretching with a constant angle (CA). Whether or not this difference is due to different structural changes of the MTUs of the lower leg and ankle plantar flexors is not known. Therefore, the purpose of this study was to compare the acute effects of single CA and CT stretching on various muscle and tendon mechanical properties.MethodSeventeen young, healthy volunteers were tested on two separate days using either CT or CA stretching (4 × 30 s each). Before and after stretching, dorsiflexion range of motion (RoM), passive resistive torque (PRT), and maximum voluntary contraction (MVC) were measured with a dynamometer. Ultrasonography of the medial gastrocnemius (GM) muscle–tendon junction (MTJ) displacement allowed us to determine the length changes in the tendon and muscle, respectively, and hence to calculate their stiffness.ResultsMaximum dorsiflexion increased while PRT, muscle–tendon stiffness, and muscle stiffness decreased following both CA and CT stretching. There was a greater increase in RoM following CT stretching compared to CA stretching. Moreover, the decline in PRT was greater during CT stretching compared to CA stretching. As expected, several functional adaptations (RoM, PRT) were different between CT and CA stretching due to the higher intensity of CT stretching. However, no structural differences in the adaptations to the stretching modalities could be detected.ConclusionWe suggest that the different functional adaptations between CA and CT stretching are the consequence of different adaptations in the perception of stretch and pain.
Highlights
Stretching is commonly performed before sports participation
With regard to static stretching, the increased range of motion (RoM) following a single exercise can be explained by a decrease in overall muscle–tendon stiffness (Kay et al 2015; Konrad et al 2016) and passive resistive torque (PRT) (Nakamura et al 2013; Konrad et al 2016)
The constant torque (CT) stretching resulted in a significantly greater increase in RoM compared to the constant angle (CA) stretching
Summary
Stretching is commonly performed before sports participation. There is some evidence that a single stretching exercise, in addition to a warm-up, can reduce the occurrence of muscle strain; this does not prevent overuseEur J Appl Physiol (2017) 117:1649–1656 injuries (McHugh and Cosgrave 2010). While Kay and Blazevich (2009), Kay et al (2015), and Konrad et al (2016) reported a decrease in stiffness of the muscle component, Kubo et al (2001) and Kato et al (2010) reported decreased tendon stiffness. These controversial results may be explained by the different stretching durations or intensities utilized
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