Effects of fatigue and training on sarcoplasmic reticulum Ca2+ regulation in human skeletal muscle

Jia L. Li, Xiao N. Wang, Steve F. Fraser, Michael F. Carey, Tim V. Wrigley, Michael J. McKenna
2002 Journal of applied physiology  
Effects of fatigue and training on sarcoplasmic reticulum Ca 2ϩ regulation in human skeletal muscle. Little is known about fatigue and training effects on sarcoplasmic reticulum (SR) function in human muscle, and we therefore investigated this in eight untrained controls (UT), eight endurance-trained (ET), and eight resistance-trained athletes (RT). Muscle biopsies (vastus lateralis) taken at rest and after 50 maximal quadriceps contractions (180°/s, 0.5 Hz) were analyzed for fiber composition,
more » ... fiber composition, metabolites and maximal SR Ca 2ϩ release, Ca 2ϩ uptake, and Ca 2ϩ -ATPase activity. Fatigue reduced (P Ͻ 0.05) Ca 2ϩ release (42.1 Ϯ 3.8%, 43.4 Ϯ 3.9%, 31.3 Ϯ 6.1%), Ca 2ϩ uptake (43.0 Ϯ 5.2%, 34.1 Ϯ 4.6%, 28.4 Ϯ 2.8%), and Ca 2ϩ -ATPase activity (38.6 Ϯ 4.2%, 48.5 Ϯ 5.7%, 29.6 Ϯ 5.0%), in UT, RT, and ET, respectively. These decreases were correlated with fatigability and with type II fiber proportion (P Ͻ 0.05). Resting SR measures were correlated with type II proportion (r Ն 0.51, P Ͻ 0.05). ET had lower resting Ca 2ϩ release, Ca 2ϩ uptake, and Ca 2ϩ -ATPase (P Ͻ 0.05) than UT and RT (P Ͻ 0.05), probably because of their lower type II proportion; only minor effects were found in RT. Thus SR function is markedly depressed with fatigue in controls and in athletes, is dependent on fiber type, and appears to be minimally affected by chronic training status. calcium release; calcium uptake; calcium-ATPase; fiber type; exercise
doi:10.1152/japplphysiol.00643.2000 pmid:11842021 fatcat:lvn73jy7vbb2bgonh4pp3xyspu