King Grub
2013-05-10, 14:30
Muscle hypertrophy in response to resistance training has been reported to occur nonuniformly along the length of the muscle. The purpose of the present study was to examine whether the regional difference in muscle hypertrophy induced by a training intervention corresponds to the regional difference in muscle activation in the training session.
METHODS:
Twelve young men participated in a training intervention program for the elbow extensors with a multi-joint resistance exercise for 12 weeks (three days per week). Before and after the intervention, cross-sectional areas (CSAs) of the triceps brachii along its length were measured with magnetic resonance (MR) images. A series of transverse relaxation time (T2)-weighted MR images were recorded before and immediately after the first session of training intervention. The T2 was calculated for each pixel within the triceps brachii. In the images recorded after the session, the number of pixels with a T2 greater than the threshold (mean + 1SD of T2 before the session) was expressed as the ratio to the whole number of pixels within the muscle, and used as an index of muscle activation (%activated area).
RESULTS:
The %activated area of the triceps brachii in the first session was significantly higher in the middle regions than that in the most proximal region. Similarly, the relative change in CSA induced by the training intervention was also significantly greater in the middle regions than the most proximal region.
CONCLUSION:
The results suggest that nonuniform muscle hypertrophy after training intervention is due to the region-specific muscle activation during the training session.
Med Sci Sports Exerc. 2013 May 7. Nonuniform Muscle Hypertrophy: Its Relation to Muscle Activation in Training Session.
http://journals.lww.com/acsm-msse/Abstract/publishahead/Nonuniform_Muscle_Hypertrophy___Its_Relation_to.98 351.aspx
METHODS:
Twelve young men participated in a training intervention program for the elbow extensors with a multi-joint resistance exercise for 12 weeks (three days per week). Before and after the intervention, cross-sectional areas (CSAs) of the triceps brachii along its length were measured with magnetic resonance (MR) images. A series of transverse relaxation time (T2)-weighted MR images were recorded before and immediately after the first session of training intervention. The T2 was calculated for each pixel within the triceps brachii. In the images recorded after the session, the number of pixels with a T2 greater than the threshold (mean + 1SD of T2 before the session) was expressed as the ratio to the whole number of pixels within the muscle, and used as an index of muscle activation (%activated area).
RESULTS:
The %activated area of the triceps brachii in the first session was significantly higher in the middle regions than that in the most proximal region. Similarly, the relative change in CSA induced by the training intervention was also significantly greater in the middle regions than the most proximal region.
CONCLUSION:
The results suggest that nonuniform muscle hypertrophy after training intervention is due to the region-specific muscle activation during the training session.
Med Sci Sports Exerc. 2013 May 7. Nonuniform Muscle Hypertrophy: Its Relation to Muscle Activation in Training Session.
http://journals.lww.com/acsm-msse/Abstract/publishahead/Nonuniform_Muscle_Hypertrophy___Its_Relation_to.98 351.aspx