Adaptations in skeletal muscle following strength training

Abstract

Five men were studied before and after 7 wk of isokinetic strength training to determine its effects on muscle enzyme activities and fiber composition. One of the subject's legs was trained using 10 repeated 6-s maximal work bouts, while the other leg performed repeated 30-s maximal knee extension exercise. The total work accomplished by each leg was constant. Training 4 times/wk achieved similar gains in peak torque for both legs at the training velocity (3.14 rad/s) and at slower speeds. Fatigability of the knee extensor muscles, as measured by a 60-s exercise test, was similar in both legs after training. Biopsy specimens showed significant changes in the % of the muscle area composed of type I and IIa fibers as a result of both strength training programs. In terms of muscle enzymes, only the 30 s exercise program resulted in elevated glycolytic, ATP-CP and mitochondrial activities. Despite these changes, none of the parameters measured were found to be related to the gains in either muscle strength or fatigability during maximal isokinetic contractions.

The Influence of Velocity-Specific Resistance Training on the In Vivo Torque-Velocity Relationship and the Cross-Sectional Area of Quadriceps Femoris

“…The 5-6% increase in knee extensor cross-sectional area in consistent with other reports of change following 5 or 6 weeks of heavy resistance training (14, 24). Coyle et al (7) and Costill et al (6) have reported significantly increased cross-sectional area of type II fibers only following 6 and 7 weeks of training the knee extensors at 5.24 and 3.1 4 rad/sec, respectively. In contrast, MacDougall et al (15) have reported increased cross-sectional area of both type I and type II fibers following heavy resistance (slow velocity) training.…”

“…More specifically, increased areas of type II muscle fibers have been reported (6,7) following training of the knee extensors at 3.14 and 5.24 radlsec. However, these results are not confidently offered as explanation for the enhanced performance and there is evidence to suggest that much of the training effect may be mediated by neurological adaptation (5,7,11,21).…”

Avaliação funcional em idosas: uma proposta metodológica

“…O ATP-CP é predominante em atividades musculares intensas e em ações de curta duração 22 . Além disso, a literatura apóia a ideía de melhoras no CMJ em relação ao 1RM 23 , sentar e levantar e foot up and go após seis semanas de treinamento de força e revelam que a melhora do desempenho das variáveis analisadas pode estar relacionada a fatores neurais (padrão de recrutamento, taxa de disparo e sincronização das unidades motoras) 2 e morfológicos (aumento da área de secção transversa e espessura muscular). De fato, nas semanas iniciais de treinamento de força, a ativação neural é predominante em relação aos fatores morfológicos [24][25][26][27] .…”

Structure and biomechanics of skeletal muscle

“…Genellikle lif türlerinin genetik olarak kararlı olduğu kabul edilir [32,33]. Ortalama bir popülasyonda kas liflerinin yaklaĢık %50-55'i tür I, yaklaĢık %30-35'i tür IIA ve yaklaĢık %15'i tür IIB'den oluĢur fakat bu yüzdeler bireysel farklılıklara göre değiĢir.…”