Long-term endurance training or physical activity has been confirmed not only to improve physical performance, but to bring about an obvious beneficial effect on human health; however, the mechanism of this effect is ...Long-term endurance training or physical activity has been confirmed not only to improve physical performance, but to bring about an obvious beneficial effect on human health; however, the mechanism of this effect is not clear. The most studied health adaptations in skeletal muscle response to endurance exercise are increased muscle glycogen level and insulin sensitivity, fiber type transformation toward oxidative myofibers, and increased mitochondrial content/function. Mitochondria are dynamic organelles in eukaryotic cells critical in physical performance and disease occurrence. The mitochondrial life cycle spans biogenesis, maintenance, and clearance. Exercise training may promote each of these processes and confer positive impacts on skeletal muscle contractile and metabolic functions. This review focused on the regulation of these processes by endurance exercise and discussed its potential benefits in health and disease. We presented evidence suggesting that exercise training potentiates not only the biogenesis of mitochondria but also the removal of old and unhealthy mitochondria through mitochondrial quality control.展开更多
Background: Although handgrip strength is a biomarker for morbidity/mor-tality, there is lack of evidence on the effects of resistance training on handgrip strength in healthy adults of all ages. Objective: The aim of...Background: Although handgrip strength is a biomarker for morbidity/mor-tality, there is lack of evidence on the effects of resistance training on handgrip strength in healthy adults of all ages. Objective: The aim of this systematic review was to assess the impact of resistance training on handgrip strength in healthy adults. Methods: Five databases/search engines were searched. Studies comparing different types of resistance exercise interventions versus a non-exercised control group on handgrip strength were included. The available data did not allow us to conduct the pre-planned meta-analyses;therefore, only descriptive statistics were performed to summarize the data. Results: Twenty studies (17 randomized and three non-randomized controlled trials) were included, most of which were conducted in older adults. Twelve studies reported no significant difference in the change in handgrip strength between the resistance training and control groups. Two studies showed increases in handgrip strength in the resistance training group compared with the control group. Other studies included results for multi-training groups or left/right hands and found increasing handgrip strength compared to controls, but only in one training group or one hand. Overall, the randomized and non-ran-domized clinical trials presented moderate risk of bias. Conclusions: Due to the lack of low risk-of-bias randomized controlled trials of young and middle-aged adults, different training protocols, and small sample sizes, the existing evidence appears insufficient to support resistance training for increasing handgrip strength in healthy adults. Future studies may seek to discern the optimal way to develop and employ resistance training to improve hand-grip strength.展开更多
The purpose of this study was to determine whether the training responses observed with low-load resistance exercise to volitional fatigue translates into significant muscle hypertrophy, and compare that response to h...The purpose of this study was to determine whether the training responses observed with low-load resistance exercise to volitional fatigue translates into significant muscle hypertrophy, and compare that response to high-load resistance training. Nine previously untrained men (aged 25 [SD 3] years at the beginning of the study, standing height 1.73 [SD 0.07] m, body mass 68.9 [SD 8.1] kg) completed 6-week of high load-resistance training (HL-RT) (75% of one repeti-tion maximal [1RM], 3-sets, 3x/wk) followed by 12 months of detraining. Following this, subjects completed 6 weeks of low load-resistance training (LL-RT) to volitional fatigue (30% 1 RM, 4 sets, 3x/wk). Increases (p 0.05) in magnetic resonance imaging-measured triceps brachii and pectorals major muscle cross-sectional areas were similar for both HL-RT (11.9% and 17.6%, respectively) and LL-RT (9.8% and 21.1%, respectively). In addition, both groups increased (p 0.05) 1RM and maximal elbow extension strength following training;however, the percent increases in 1RM (8.6% vs. 21.0%) and elbow extension strength (6.5% vs. 13.9%) were significantly (p 0.05) lower with LL-RT. Both protocols elicited similar increases in muscle cross-sectional area, however differences were observed in strength. An explanation of the smaller relative increases in strength may be due to the fact that detraining after HL-RT did not cause strength values to return to baseline levels thereby producing smaller changes in strength. In addition, the results may also suggest that the consistent practice of lifting a heavy load is necessary to maximize gains in muscular strength of the trained movement. These results demonstrate that significant muscle hypertrophy can occur without high-load resistance training and suggests that the focus on percentage of external load as the important deciding factor on muscle hypertrophy is too simplistic and inappropriate.展开更多
Purpose The purpose of this study was to examine the influence of muscle length and fatigue on maximal force,submaximal force steadiness,and electromyographic(EMG)activity of the biceps brachii.Methods Force and EMG r...Purpose The purpose of this study was to examine the influence of muscle length and fatigue on maximal force,submaximal force steadiness,and electromyographic(EMG)activity of the biceps brachii.Methods Force and EMG responses were measured before and after a fatigue protocol consisting of maximal intermit-tent contractions of the elbow flexors until task failure(n=20).The protocol was performed on two separate occasions in a randomized order.During one visit,the elbow joint was at 90°(EF90)and for the other,it was extended to 120°(EF120).Results The results show a large effect size for greater force loss following fatigue at long muscle length(P=0.067,n^(2)_(p)=0.166).The fatigue-based decreases in force steadiness were not different between muscle lengths(P=0.502,n^(2)_(p)=0.024).Force steadiness was lower at long muscle length before and after fatigue(P<0.01,d=0.691).Following fatigue,muscle excitation decreased and increased during maximal and submaximal force tasks,respectively,yet there were no length-dependent EMG responses.Conclusions The novel findings show fatigue at long muscle length likely affects force loss to a greater degree than fatigue-based decreases in force steadiness.These data show lower elbow flexion force steadiness when the biceps brachii is in a lengthened position.展开更多
Thousands of resting state functional magnetic resonance imaging(RS-f MRI)articles have been published on brain disorders.For precise localization of abnormal brain activity,a voxel-level comparison is needed.Because ...Thousands of resting state functional magnetic resonance imaging(RS-f MRI)articles have been published on brain disorders.For precise localization of abnormal brain activity,a voxel-level comparison is needed.Because of the large number of voxels in the brain,multiple comparison correction(MCC)must be performed to reduce false positive rates,and a smaller P value(usually including either liberal or stringent MCC)is widely recommended[1].展开更多
基金supported by research grants from the Natural Sciences Foundation of China(31110103919,81370454,31200894,31000523,30771048,30470837,31071040,and 30270638)Tianjin Municipal Sci-tech-innovation Base Project(10KJPT024)+1 种基金General Administration of Sport of China Basic Project(10B058)National Sci-tech Support Project(2012BAK21B03)
文摘Long-term endurance training or physical activity has been confirmed not only to improve physical performance, but to bring about an obvious beneficial effect on human health; however, the mechanism of this effect is not clear. The most studied health adaptations in skeletal muscle response to endurance exercise are increased muscle glycogen level and insulin sensitivity, fiber type transformation toward oxidative myofibers, and increased mitochondrial content/function. Mitochondria are dynamic organelles in eukaryotic cells critical in physical performance and disease occurrence. The mitochondrial life cycle spans biogenesis, maintenance, and clearance. Exercise training may promote each of these processes and confer positive impacts on skeletal muscle contractile and metabolic functions. This review focused on the regulation of these processes by endurance exercise and discussed its potential benefits in health and disease. We presented evidence suggesting that exercise training potentiates not only the biogenesis of mitochondria but also the removal of old and unhealthy mitochondria through mitochondrial quality control.
文摘Background: Although handgrip strength is a biomarker for morbidity/mor-tality, there is lack of evidence on the effects of resistance training on handgrip strength in healthy adults of all ages. Objective: The aim of this systematic review was to assess the impact of resistance training on handgrip strength in healthy adults. Methods: Five databases/search engines were searched. Studies comparing different types of resistance exercise interventions versus a non-exercised control group on handgrip strength were included. The available data did not allow us to conduct the pre-planned meta-analyses;therefore, only descriptive statistics were performed to summarize the data. Results: Twenty studies (17 randomized and three non-randomized controlled trials) were included, most of which were conducted in older adults. Twelve studies reported no significant difference in the change in handgrip strength between the resistance training and control groups. Two studies showed increases in handgrip strength in the resistance training group compared with the control group. Other studies included results for multi-training groups or left/right hands and found increasing handgrip strength compared to controls, but only in one training group or one hand. Overall, the randomized and non-ran-domized clinical trials presented moderate risk of bias. Conclusions: Due to the lack of low risk-of-bias randomized controlled trials of young and middle-aged adults, different training protocols, and small sample sizes, the existing evidence appears insufficient to support resistance training for increasing handgrip strength in healthy adults. Future studies may seek to discern the optimal way to develop and employ resistance training to improve hand-grip strength.
文摘The purpose of this study was to determine whether the training responses observed with low-load resistance exercise to volitional fatigue translates into significant muscle hypertrophy, and compare that response to high-load resistance training. Nine previously untrained men (aged 25 [SD 3] years at the beginning of the study, standing height 1.73 [SD 0.07] m, body mass 68.9 [SD 8.1] kg) completed 6-week of high load-resistance training (HL-RT) (75% of one repeti-tion maximal [1RM], 3-sets, 3x/wk) followed by 12 months of detraining. Following this, subjects completed 6 weeks of low load-resistance training (LL-RT) to volitional fatigue (30% 1 RM, 4 sets, 3x/wk). Increases (p 0.05) in magnetic resonance imaging-measured triceps brachii and pectorals major muscle cross-sectional areas were similar for both HL-RT (11.9% and 17.6%, respectively) and LL-RT (9.8% and 21.1%, respectively). In addition, both groups increased (p 0.05) 1RM and maximal elbow extension strength following training;however, the percent increases in 1RM (8.6% vs. 21.0%) and elbow extension strength (6.5% vs. 13.9%) were significantly (p 0.05) lower with LL-RT. Both protocols elicited similar increases in muscle cross-sectional area, however differences were observed in strength. An explanation of the smaller relative increases in strength may be due to the fact that detraining after HL-RT did not cause strength values to return to baseline levels thereby producing smaller changes in strength. In addition, the results may also suggest that the consistent practice of lifting a heavy load is necessary to maximize gains in muscular strength of the trained movement. These results demonstrate that significant muscle hypertrophy can occur without high-load resistance training and suggests that the focus on percentage of external load as the important deciding factor on muscle hypertrophy is too simplistic and inappropriate.
文摘Purpose The purpose of this study was to examine the influence of muscle length and fatigue on maximal force,submaximal force steadiness,and electromyographic(EMG)activity of the biceps brachii.Methods Force and EMG responses were measured before and after a fatigue protocol consisting of maximal intermit-tent contractions of the elbow flexors until task failure(n=20).The protocol was performed on two separate occasions in a randomized order.During one visit,the elbow joint was at 90°(EF90)and for the other,it was extended to 120°(EF120).Results The results show a large effect size for greater force loss following fatigue at long muscle length(P=0.067,n^(2)_(p)=0.166).The fatigue-based decreases in force steadiness were not different between muscle lengths(P=0.502,n^(2)_(p)=0.024).Force steadiness was lower at long muscle length before and after fatigue(P<0.01,d=0.691).Following fatigue,muscle excitation decreased and increased during maximal and submaximal force tasks,respectively,yet there were no length-dependent EMG responses.Conclusions The novel findings show fatigue at long muscle length likely affects force loss to a greater degree than fatigue-based decreases in force steadiness.These data show lower elbow flexion force steadiness when the biceps brachii is in a lengthened position.
基金the National Natural Science Foundation of China(81520108016,81661148045,and 31471084 to Yu-Feng Zang81671774 and 81630031 to Chao-Gan Yan+11 种基金81571228 to Tao Wu61571047 to Xia Wu81701664 to Jian Wang,81471654 to Biao Huang81701671 to Wei-Guo Liu82001898 to Xi-Ze Jia81771820,81371519 and 81571654 to Wei Luo)Henry G Leong Endowed Professorship in Neurology to Shu-Leong Ho and Shirley YY Pang,BRC for Mental Health at South London and Maudsley NHS Foundation Trust and by the Sackler Institute to Grainne McAlonan,NIH(2R01AG006457 to Fay B.Horak1RC4NS073008-01 and P50NS062684 to Tara Madhyastha)NINDS Intramural Research Program to Mark HallettStart-up Funds for Leading Talents at Beijing Normal UniversityNational Basic Science Data Center‘‘Chinese Data-sharing Warehouse for In-vivo Imaging Brain”(NBSDC-DB-15)to Xi-Nian ZuoGrant NU20-04-00294 of the Agency for Health Research,Czech Republic to Lenka Krajcovicova and Irena Rektorova。
文摘Thousands of resting state functional magnetic resonance imaging(RS-f MRI)articles have been published on brain disorders.For precise localization of abnormal brain activity,a voxel-level comparison is needed.Because of the large number of voxels in the brain,multiple comparison correction(MCC)must be performed to reduce false positive rates,and a smaller P value(usually including either liberal or stringent MCC)is widely recommended[1].
