The addition of sarcomeres in series(sarcomerogenesis)in skeletal muscle has increasingly fascinated exercise scientists in recent years due to its potential to positively impact performance.1,2 In their new review ar...The addition of sarcomeres in series(sarcomerogenesis)in skeletal muscle has increasingly fascinated exercise scientists in recent years due to its potential to positively impact performance.1,2 In their new review article,Triggering sarcomerogenesis:Examining key stimuli and the role attributed to eccentric training—Historical,systematic,and meta-analytic review,Blazevich et al.3 provide a commendable overview of the history behind this area of research from the 1600s to present.展开更多
We thank Power et al.1 for their interest in our review2 and for contributing to this important scientific discussion.We welcome their commentary and acknowledge the merit of continuing to scrutinize and refine interp...We thank Power et al.1 for their interest in our review2 and for contributing to this important scientific discussion.We welcome their commentary and acknowledge the merit of continuing to scrutinize and refine interpretations in this evolving field.Given that much research time and financial investment is being given to the study of the effects of eccentric training in both athletic and clinical contexts,it is incumbent on our field to demonstrate whether eccentric contractions are a key(or the key)stimulus for sarcomerogenesis(increases in serial sarcomere number(SSN)).展开更多
Sarcomerogenesis,the addition of serial sarcomeres in skeletal muscle myofibrils and fibres,is a natural occurrence during growth and maturation of animals,including humans.However,the detailed mechanisms that allow f...Sarcomerogenesis,the addition of serial sarcomeres in skeletal muscle myofibrils and fibres,is a natural occurrence during growth and maturation of animals,including humans.However,the detailed mechanisms that allow for sarcomerogenesis are not fully understood.In some diseases,such as cerebral palsy in children,sarcomerogenesis appears to be inhibited or at least reduced,1,2 often causing severe restrictions in muscle and joint function.展开更多
Background:This paper aimed to systematically review the literature regarding the effects of resistance training(RT)performed at longer-muscle length(LML)versus shorter-muscle length(SML)on proxy measurements for long...Background:This paper aimed to systematically review the literature regarding the effects of resistance training(RT)performed at longer-muscle length(LML)versus shorter-muscle length(SML)on proxy measurements for longitudinal hypertrophy.Methods:We included studies that satisfied the following criteria:(1)be a resistance training intervention with a comparison of LML vs SML-RT;(2)assess both fascicle length(FL)and muscle size pre-and post-intervention;(3)involve healthy adults aged≥18 years;(4)be published in an English-language journal,and;(5)have a minimum training intervention duration of 4 weeks.Three databases were searched in February 2024(Google Scholar,PubMed/Medline,Scopus)for relevant articles,alongside'forward'and'backward'citation searching of articles included and additions via authors'personal knowledge.The results of studies were described narratively,compared,and contrasted.Eight studies met the inclusion criteria,totaling a sample size of 120.Results:Our results suggest that both muscle size and fascicle length increases may be greater following LML-RT versus SML-RT,suggesting LML-RT may lead to greater longitudinal hypertrophy than SML-RT.Notably,evidence is largely mixed;no studies to date have attempted to estimate serial sarcomere number changes from LML versus SML-RT,and all but one study used linear extrapolation methods to estimate FL,which has questionable validity.Therefore,the structural adaptations underlying hypertrophy from LML-RT remain undetermined.Conclusion:In conclusion,results suggest that LML-RT may be superior to SML-RT for inducing muscle hypertrophy and,more specifically,longitudinal growth,though evidence is mixed.展开更多
Background:Eccentric exercise increases muscle fascicle lengths;however,the mechanisms behind this adaptation are still unknown.This study aimed to determine whether biceps femoris long head(BFlh)fascicle length incre...Background:Eccentric exercise increases muscle fascicle lengths;however,the mechanisms behind this adaptation are still unknown.This study aimed to determine whether biceps femoris long head(BFlh)fascicle length increases in response to 3 weeks of eccentric exercise training are the result of an in-series addition of sarcomeres within the muscle fibers.Methods:Ten recreationally active participants(age=27±3 years;mass=70±14 kg;height=174±9 cm;mean±SD)completed 3 weeks of Nordic hamstring exercise(NHE)training on a custom exercise device that was instrumented with load cells.We collected in vivo sarcomere and muscle fascicle images of the BFlh in 2 regions(central and distal)by using microendoscopy and 3 dimension ultrasonography.We then estimated sarcomere length,sarcomere number,and fascicle length before and after the training intervention.Results:Eccentric knee flexion strength increased after the training(15%;p<0.001;η_(p)^(2)=0.75).Further,we found a significant increase in fascicle length(21%;p<0.001;η_(p)^(2)=0.81)and sarcomere length(17%;p<0.001;ηp2=0.90)in the distal but not in the central portion of the muscle.The estimated number of sarcomeres in series did not change in either region.Conclusion:Fascicle length adaptations appear to be heterogeneous in the BFlh in response to 3 weeks of NHE training.An increase in sarcomere length,rather than the addition of sarcomeres in series,appears to underlie increases in fascicle length in the distal region of the BFlh.The mechanism driving regional increases in fascicle and sarcomere length remains unknown,but we speculate that it may be driven by regional changes in the pas sive tension of muscle or connective tis sue adaptations.展开更多
文摘The addition of sarcomeres in series(sarcomerogenesis)in skeletal muscle has increasingly fascinated exercise scientists in recent years due to its potential to positively impact performance.1,2 In their new review article,Triggering sarcomerogenesis:Examining key stimuli and the role attributed to eccentric training—Historical,systematic,and meta-analytic review,Blazevich et al.3 provide a commendable overview of the history behind this area of research from the 1600s to present.
文摘We thank Power et al.1 for their interest in our review2 and for contributing to this important scientific discussion.We welcome their commentary and acknowledge the merit of continuing to scrutinize and refine interpretations in this evolving field.Given that much research time and financial investment is being given to the study of the effects of eccentric training in both athletic and clinical contexts,it is incumbent on our field to demonstrate whether eccentric contractions are a key(or the key)stimulus for sarcomerogenesis(increases in serial sarcomere number(SSN)).
文摘Sarcomerogenesis,the addition of serial sarcomeres in skeletal muscle myofibrils and fibres,is a natural occurrence during growth and maturation of animals,including humans.However,the detailed mechanisms that allow for sarcomerogenesis are not fully understood.In some diseases,such as cerebral palsy in children,sarcomerogenesis appears to be inhibited or at least reduced,1,2 often causing severe restrictions in muscle and joint function.
文摘Background:This paper aimed to systematically review the literature regarding the effects of resistance training(RT)performed at longer-muscle length(LML)versus shorter-muscle length(SML)on proxy measurements for longitudinal hypertrophy.Methods:We included studies that satisfied the following criteria:(1)be a resistance training intervention with a comparison of LML vs SML-RT;(2)assess both fascicle length(FL)and muscle size pre-and post-intervention;(3)involve healthy adults aged≥18 years;(4)be published in an English-language journal,and;(5)have a minimum training intervention duration of 4 weeks.Three databases were searched in February 2024(Google Scholar,PubMed/Medline,Scopus)for relevant articles,alongside'forward'and'backward'citation searching of articles included and additions via authors'personal knowledge.The results of studies were described narratively,compared,and contrasted.Eight studies met the inclusion criteria,totaling a sample size of 120.Results:Our results suggest that both muscle size and fascicle length increases may be greater following LML-RT versus SML-RT,suggesting LML-RT may lead to greater longitudinal hypertrophy than SML-RT.Notably,evidence is largely mixed;no studies to date have attempted to estimate serial sarcomere number changes from LML versus SML-RT,and all but one study used linear extrapolation methods to estimate FL,which has questionable validity.Therefore,the structural adaptations underlying hypertrophy from LML-RT remain undetermined.Conclusion:In conclusion,results suggest that LML-RT may be superior to SML-RT for inducing muscle hypertrophy and,more specifically,longitudinal growth,though evidence is mixed.
基金partially funded by a Company of Biologists Travelling Fellowshippartially subsidized by a grant funded by the Australian Research Council(Linkage program)in partnership with the Australian Sports Commission(LP140100260)。
文摘Background:Eccentric exercise increases muscle fascicle lengths;however,the mechanisms behind this adaptation are still unknown.This study aimed to determine whether biceps femoris long head(BFlh)fascicle length increases in response to 3 weeks of eccentric exercise training are the result of an in-series addition of sarcomeres within the muscle fibers.Methods:Ten recreationally active participants(age=27±3 years;mass=70±14 kg;height=174±9 cm;mean±SD)completed 3 weeks of Nordic hamstring exercise(NHE)training on a custom exercise device that was instrumented with load cells.We collected in vivo sarcomere and muscle fascicle images of the BFlh in 2 regions(central and distal)by using microendoscopy and 3 dimension ultrasonography.We then estimated sarcomere length,sarcomere number,and fascicle length before and after the training intervention.Results:Eccentric knee flexion strength increased after the training(15%;p<0.001;η_(p)^(2)=0.75).Further,we found a significant increase in fascicle length(21%;p<0.001;η_(p)^(2)=0.81)and sarcomere length(17%;p<0.001;ηp2=0.90)in the distal but not in the central portion of the muscle.The estimated number of sarcomeres in series did not change in either region.Conclusion:Fascicle length adaptations appear to be heterogeneous in the BFlh in response to 3 weeks of NHE training.An increase in sarcomere length,rather than the addition of sarcomeres in series,appears to underlie increases in fascicle length in the distal region of the BFlh.The mechanism driving regional increases in fascicle and sarcomere length remains unknown,but we speculate that it may be driven by regional changes in the pas sive tension of muscle or connective tis sue adaptations.
