An ultrastructural study of the stretch-induced hypertrophy of skeletal muscle

Abstract

The teres minor muscle of the adult chicken was studied ultrastructurally following tonic stretch-induced hypertrophy. The contralateral control muscle fibres showed compact myofibrils and proliferation of normal Z-bands. Myofibrils of the hypertrophied muscle however, showed Z-band alterations as Z-band expansions and Z-band streaming. Thus Z-band is a highly responsive structure to tonic stretch. Since a number of neuromuscular conditions display Z-band anomalies, the latter occurring in response to a variety of metabolic and physiologic stimuli, including tonic stretch as shown here, represents a non-specific phenomenon.

Stretch training induces unequal adaptation in muscle fascicles and thickness in medial and lateral gastrocnemii

“…This is the first study in humans to suggest hypertrophic adaptation as a result of stretch training, although in animal stretching studies, muscle growth is common . From resistance training, muscle growth is initiated through muscle damage at the sarcomeres triggering a cascade of cellular signaling events which culminates in greater protein production and incorporation into Z line material . Through this process, streaming widens the Z line, encourages focal thickening and expansion, and in this study might have increased muscle thickness along with fascicle length.…”

“…From resistance training, muscle growth is initiated through muscle damage at the sarcomeres triggering a cascade of cellular signaling events which culminates in greater protein production and incorporation into Z line material . Through this process, streaming widens the Z line, encourages focal thickening and expansion, and in this study might have increased muscle thickness along with fascicle length. Although not previously used in stretch training studies but a regular practice in resistance training where hypertrophy is the desired result, ingestion of amino acids is known to increase protein synthesis .…”

Gain and loss of functional locomotor recovery following contusive spinal cord injury in the adult rat.

“…5) Most importantly, the hindlimb muscles of SR animals revealed significant atrophy (Table 4). Stretch-induced hypertrophy is a reasonable result of daily stretch in our model (Khan, 1986;Kelley, 1996). Atrophy in SR animals' hindlimb muscle was likely a result of decreased weight-supported stepping during in-cage activity due to stretch induced loss of locomotor function.…”