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Muscle-tendon structure and dimensions in adults and children.
成人与儿童肌腱的结构和大小
Abstract
Muscle performance is closely related to the architecture and dimensions of the muscle-tendon unit and the effect of maturation on these architectural characteristics in humans is currently unknown. This study determined whether there are differences in musculo-tendinous architecture between adults and children of both sexes. Fascicle length and pennation angle 肌纤维与肌腱所成角度 were measures from ultrasound images at three sites along the length of the vastus intermedius, vastus lateralis, vastis medialis and rectus femoris muscles. Muscle volume and muscle-tendon length were measured from magnetic resonance images. Muscle physiological cross-sectional area (PCSA) was calculated as the ratio of muscle volume to optimum fascicle length. Fascicle length was greater in the adult groups than in children but pennation angle did not differ between groups between adults and children for any quadriceps muscle. Quadriceps volume and PCSA of each muscle were greater in adults than children but the relative proportion of each head to the total quadriceps volume was similar in all groups. However, the difference in PCSA between adult and children was greater than the difference in fascicle length. It is concluded that the fascicle, muscle and tendon lengthen proportionally during maturation, thus the muscle-tendon stiffness and excursion range are likely to be similar in children and adults but the relatively greater increase in PCSA than fascicle length indicates that adult muscles are better designed for force production than children’s muscles.
Muscle and tendon length
The length of each quadriceps femoris head muscle was measured from the MRIs. The proximal tendon and its origin could not be clearly identified from the MRIs for any of the muscles. Therefore, the tendon length for each muscle was calculated as the difference between length of the entire MTU and muscle length. The length of MTU was estimated based on the distance between the bony landmarks typically considered as the origin and insertion of each muscle. The origins of the VI, VL and VM muscles extend along the linea aspera, with the most proximal attachment point being at the level of the greater trochanter, which we considered to be the origin of these three muscles. The RF MTU originates at the anterior inferior iliac spine. The insertion of the MTU of all muscles was the superior border of the patella. These landmarks were identified from the MRIs and the distance between them considered as the length of the respective MTU.
Maximal voluntary contraction. Isometric plantar flexion and dorsiflexion maximal voluntary contraction (MVC) torque was recorded while the subject was prone with the knees fully extended and the tested foot (left foot) strapped to the footplate of a dynamometer. The plantar flexion MVCs were used to assess muscle strength, whereas dorsiflexion MVCs were used to quantify antagonistic muscle coactivation and enable the assessment of gastrocnemius (GS) tendon mechanical properties (see below). To emulate the ankle joint angle during the postural tests, all MVC measurements were taken at 0° ankle angle (the foot at 90° with respect to the lower leg axis). The subjects were asked to gradually develop torque and maintain MVC for 3 s. A short series of three to four warm-up submaximal contractions were carried out at the beginning of the protocol. During all tests, visual and verbal feedback was employed to motivate the subjects.
Muscle-tendon structure and dimensions in adults and children.
成人与儿童肌腱的结构和大小
Abstract
Muscle performance is closely related to the architecture and dimensions of the muscle-tendon unit and the effect of maturation on these architectural characteristics in humans is currently unknown. This study determined whether there are differences in musculo-tendinous architecture between adults and children of both sexes. Fascicle length and pennation angle 肌纤维与肌腱所成角度 were measures from ultrasound images at three sites along the length of the vastus intermedius, vastus lateralis, vastis medialis and rectus femoris muscles. Muscle volume and muscle-tendon length were measured from magnetic resonance images. Muscle physiological cross-sectional area (PCSA) was calculated as the ratio of muscle volume to optimum fascicle length. Fascicle length was greater in the adult groups than in children but pennation angle did not differ between groups between adults and children for any quadriceps muscle. Quadriceps volume and PCSA of each muscle were greater in adults than children but the relative proportion of each head to the total quadriceps volume was similar in all groups. However, the difference in PCSA between adult and children was greater than the difference in fascicle length. It is concluded that the fascicle, muscle and tendon lengthen proportionally during maturation, thus the muscle-tendon stiffness and excursion range are likely to be similar in children and adults but the relatively greater increase in PCSA than fascicle length indicates that adult muscles are better designed for force production than children’s muscles.
Muscle and tendon length
The length of each quadriceps femoris head muscle was measured from the MRIs. The proximal tendon and its origin could not be clearly identified from the MRIs for any of the muscles. Therefore, the tendon length for each muscle was calculated as the difference between length of the entire MTU and muscle length. The length of MTU was estimated based on the distance between the bony landmarks typically considered as the origin and insertion of each muscle. The origins of the VI, VL and VM muscles extend along the linea aspera, with the most proximal attachment point being at the level of the greater trochanter, which we considered to be the origin of these three muscles. The RF MTU originates at the anterior inferior iliac spine. The insertion of the MTU of all muscles was the superior border of the patella. These landmarks were identified from the MRIs and the distance between them considered as the length of the respective MTU.
Maximal voluntary contraction. Isometric plantar flexion and dorsiflexion maximal voluntary contraction (MVC) torque was recorded while the subject was prone with the knees fully extended and the tested foot (left foot) strapped to the footplate of a dynamometer. The plantar flexion MVCs were used to assess muscle strength, whereas dorsiflexion MVCs were used to quantify antagonistic muscle coactivation and enable the assessment of gastrocnemius (GS) tendon mechanical properties (see below). To emulate the ankle joint angle during the postural tests, all MVC measurements were taken at 0° ankle angle (the foot at 90° with respect to the lower leg axis). The subjects were asked to gradually develop torque and maintain MVC for 3 s. A short series of three to four warm-up submaximal contractions were carried out at the beginning of the protocol. During all tests, visual and verbal feedback was employed to motivate the subjects.
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