Abstract
BackgroundEccentric exercises have been used in physical training, injury prevention, and rehabilitation programs. The systematic use of eccentric training promotes specific morphological adaptations on skeletal muscles. However, synergistic muscles, such as the triceps surae components, might display different structural adaptations due to differences in architecture, function, and load sharing. Therefore, the purpose of this study was to determine the effects of an eccentric training program on the triceps surae (GM, gastrocnemius medialis; GL, gastrocnemius lateralis; and SO, soleus) muscle architecture.MethodsTwenty healthy male subjects (26 ± 4 years) underwent a 4-week control period followed by a 12-week eccentric training program. Muscle architecture [fascicle length (FL), pennation angle (PA), and muscle thickness (MT)] of GM, GL, and SO was evaluated every 4 weeks by ultrasonography.ResultsFascicle lengths (GM: 13.2%; GL: 8.8%; SO: 21%) and MT (GM: 14.9%; GL: 15.3%; SO: 19.1%) increased from pre- to post-training, whereas PAs remained similar. GM and SO FL and MT increased up to the 8th training week, whereas GL FL increased up to the 4th week. SO displayed the highest, and GL the smallest gains in FL post-training.ConclusionAll three synergistic plantar flexor muscles increased FL and MT with eccentric training. MT increased similarly among the synergistic muscles, while the muscle with the shortest FL at baseline (SO) showed the greatest increase in FL.
Highlights
Muscle architecture has an important role in skeletal muscle force production (Fukunaga et al, 1997; Lieber and Fridén, 2000)
Considering the conflicting results regarding eccentric training adaptations of the triceps surae muscles, the limited information on architectural adaptations of the individual triceps surae muscles, and the lack of longitudinal, time-dependent adaptations of muscles subjected to eccentric training programs, the purpose of this study was to determine the effects of a 12-week eccentric training program on the architecture of the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and shortest Fascicle length (FL) at baseline (SO) muscles
Participants were excluded if (1) they were enrolled in any lower limb strength training program within 6 months of this study; (2) they had any musculoskeletal injury of the lower and/or the upper limbs; (3) they had any contra-indications for maximal effort contractions; (4) they had any difficulty in understanding and/or executing the testing and training protocols at the isokinetic dynamometer; or if (5) they missed two or more of the training sessions
Summary
Muscle architecture (i.e., the geometrical arrangement by which muscle fibers are organized with respect to a muscle’s line of action) has an important role in skeletal muscle force production (Fukunaga et al, 1997; Lieber and Fridén, 2000). Fascicle length (FL) is associated with the serial sarcomere number, which has a direct impact on the fiber/muscle shortening velocity and excursion (Edman et al, 1985; Lieber and Fridén, 2000; Blazevich, 2006). The systematic use of eccentric training promotes specific morphological adaptations on skeletal muscles. Synergistic muscles, such as the triceps surae components, might display different structural adaptations due to differences in architecture, function, and load sharing. The purpose of this study was to determine the effects of an eccentric training program on the triceps surae (GM, gastrocnemius medialis; GL, gastrocnemius lateralis; and SO, soleus) muscle architecture
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