title: Alterations in sarcoplasmic reticulum function in female vastus lateralis with eccentric exercise.
abstract: This study examined the alterations in sarcoplasmic reticulum (SR) Ca2+ sequestration function in homogenates during eccentric exercise and recovery and following additional eccentric exercise, and correlated these alterations with changes in force output. Eight healthy, untrained females, aged 20-25 years, cycled for a total of 60 min on an eccentric cycle ergometer (30 min at 66+/-3% VO2 peak and 30 min at 76+/-3% VO2 peak, determined during concentric exercise). Biopsies (extracted from the vastus lateralis) were taken before and after the exercise as well as on days 2, 6 and prior to and following identical exercise on day 14. Ca2+-uptake (nmol/min/mg protein) was unaffected (p > 0.05) following the first session of eccentric exercise; however, by day 2 a depression in uptake (p < 0.05) was observed which persisted throughout the remainder of the experiment. Maximal Ca2+-ATPase activity (nmol/min/mg protein) was elevated (p < 0.05) immediately following the first exercise session, remained elevated through day 2 and returned to pre-exercise levels by day 6 of recovery and increased again by day 14. No changes in either Ca2+-ATPase activity or Ca2+-uptake were observed with exercise on day 14. Both eccentric sessions, performed on days 0 and 14, resulted in similar depressions in force (p < 0.05) immediately following exercise. By day 2 force had recovered to pre-exercise levels. The results demonstrate that a prolonged alteration in SR Ca2+-uptake occurs following eccentric work that is unaccompanied by parallel changes in either SR Ca2+-ATPase activity or mechanical performance.
authors.affiliation: Department of Kinesiology, University of Waterloo, Ontario, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Enns
authors.forename: H
authors.initials: H
authors.lastname: Green
authors.forename: R
authors.initials: R
authors.lastname: Tupling
authors.forename: M
authors.initials: M
authors.lastname: Burnett
authors.forename: S
authors.initials: S
authors.lastname: Grant
authors.forename: D
authors.initials: D
authors.lastname: Ranney
mesh_terms: D000328:Adult; D002118:Calcium / Q000378:metabolism; D004558:Electric Stimulation; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D009043:Motor Activity / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010101:Oxygen Consumption; D011930:Reaction Time; D012519:Sarcoplasmic Reticulum / Q000502:physiology*; D013997:Time Factors
chemical_list: D002118:Calcium