Space travel since the 1960s has led to a number of physiological alterations to homeostasis in astronauts. Extensive variation in the pattern of responses observed has led a concerted effort to develop countermeasure...Space travel since the 1960s has led to a number of physiological alterations to homeostasis in astronauts. Extensive variation in the pattern of responses observed has led a concerted effort to develop countermeasures to overcome such changes and restore homeostasis, and thus “health” is defined as more “Earth-like”. These adaptations to a space environment by a species which evolved and normally exists in the 1 g environment, the geomagnetic field, and background radiation of Earth are viewed as threats to health as defined by the conditions of Earth. Exposure to space can lead to alterations in genomic stability and epigenetic signatures, alterations which could redefine “health” and responses to risks for loss of health for those who will return to Earth. In contrast, in the future individuals born in non-Earth space environments will likely develop an integrated metabolic set point defined by those conditions. They will thus be shaped by both the local environments, and space-associated genomic/epigenomic alterations to their parents. Therefore, such an altered set point for those born and raised in non-Earth space environments will potentially have physiological and molecular consequences which may lead to either new evolutionary adaptation, or to compromise of long term health due to drastically altered set points for integrated physiologic function which is at odds with the evolutionary history of humans. The implications of the two options will be critical for defining “health” in altered environments encountered during space ventures, as well as providing insights into the regulation of human integrity at the physiological level. Therefore, the definition of “health” is dependent on the boundary conditions surrounding development and maturation, and is a dynamic concept.展开更多
With the Rio Olympics just a few months past,we remember the excitement,the incredible performances,and the controversies.As happens so often,the Olympic Games focus attention not only on athletic achievements but als...With the Rio Olympics just a few months past,we remember the excitement,the incredible performances,and the controversies.As happens so often,the Olympic Games focus attention not only on athletic achievements but also on how athletes may reach ever-increasing levels of performance.Doping,medical展开更多
Objective:We reviewed and appraised the existing evidence of in vivo manifestations of residual force enhancement in human skeletal muscles and assessed,through a meta-analysis,the effect of an immediate history of ec...Objective:We reviewed and appraised the existing evidence of in vivo manifestations of residual force enhancement in human skeletal muscles and assessed,through a meta-analysis,the effect of an immediate history of eccentric contraction on the subsequent torque capacity of voluntary and electrically evoked muscle contractions.Methods:Our search was conducted from database inception to May 2020.Descriptive information was extracted from,and quality was assessed for,45 studies.Meta-analyses and metaregressions were used to analyze residual torque enhancement and its dependence on the angular amplitude of the preceding eccentric contraction.Results:Procedures varied across studies with regards to muscle group tested,angular stretch amplitude,randomization of contractions,time window analyzed,and verbal command.Torque capacity in isometric(constant muscle tendon unit length and joint angle)contractions preceded by an eccentric contraction was typically greater compared to purely isometric contractions,and this effect was greater for electrically evoked muscle contractions than voluntary contractions.Residual torque enhancement differed across muscle groups for the voluntary contractions,with a significant enhancement in torque observed for the adductor pollicis,ankle dorsiflexors,ankle plantar flexors,and knee extensors,but not for the elbow and knee flexors.Meta-regressions revealed that the angular amplitude of the eccentric contraction(normalized to the respective joints full range of motion)was not associated with the residual torque enhancement observed.Conclusion:There is evidence of residual torque enhancement for most,but not all,muscle groups,and residual torque enhancement is greater for electrically evoked than for voluntary contractions.Contrary to our hypothesis,and contrary to generally accepted findings on isolated muscle preparations,residual torque enhancement in voluntary and electrically evoked contractions does not seem to depend on the angular amplitude of the preceding eccentric contraction.展开更多
Hybrid journals are journals that provide both of 2 common publication options:(a)the traditional approach,where either institutions pay for a subscription or readers purchase individual articles(free of charge for th...Hybrid journals are journals that provide both of 2 common publication options:(a)the traditional approach,where either institutions pay for a subscription or readers purchase individual articles(free of charge for the submitting author);and(b)open access,where articles are accessible without a subscription and free of charge for the reader(the submitting author typically pays an article processing charge).Hybrid journals earn a fixed amount of money from subscriptions,and they earn additional income from the article processing charges associated with their open access option.A hybrid journal can increase its income by publishing a greater number of open access articles.展开更多
Purpose:This study aimed to examine the reliability and validity of load-velocity(L-V)relationship variables obtained through the 2-point method using different load combinations and velocity variables.Methods:Twenty ...Purpose:This study aimed to examine the reliability and validity of load-velocity(L-V)relationship variables obtained through the 2-point method using different load combinations and velocity variables.Methods:Twenty men performed 2 identical sessions consisting of 2 countermovement jumps against 4 external loads(20 kg,40 kg,60 kg,and80 kg)and a heavy squat against a load linked to a mean velocity(MV)of 0.55 m/s(load_(0.55)).The L-V relationship variables(load-axis intercept(L_(0)),velocity-axis intercept(v_(0)),and area under the L-V relationship line(A_(line)))were obtained using 3 velocity variables(MV,mean propulsive velocity(MPV),and peak velocity)by the multiple-point method including(20-40-60-80-load_(0.55))and excluding(20-40-60-80)the heavy squat,as well as from their respective 2-point methods(20-load_(0.55)and 20-80).Results:The L-V relationship variables were obtained with an acceptable reliability(coefncient of variation(CV)≤7.30%;intra-class correlation coefficient>0.63).The reliability of L_(0)and v_(0)was comparable for both methods(CV_(ratio)(calculated as higher value/lower value):1.11-1.12),but the multiple-point method provided Al_(ine)with a greater reliability(CV_(ratio)=1.26).The use of a heavy squat provided the L-V relationship variables with a comparable or higher reliability than the use of a heavy countermovement jump load(CV_(ratio):1.06-1.19).The peak velocity provided the load-velocity relationship variables with the greatest reliability(CV_(ratio):1.15-1.86)followed by the MV(CV_(ratio):1.07-1.18),and finally the MPV.The 2-point methods only revealed an acceptable validity for the MV and MPV(effect size≤0.19;Pearson s product-moment correlation coefficient≥0.96;Lin's concordance correlation coefficient≥0.94).Conclusion:The 2-point method obtained from a heavy squat load and MV or MPV is a quick,safe,and reliable procedure to evaluate the lower-body maximal neuromuscular capacities through the L-V relationship.展开更多
This review summarizes research discoveries within 4 areas of exercise immunology that have received the most attention from investigators :(1) acute and chronic effects of exercise on the immune system,(2) clinical b...This review summarizes research discoveries within 4 areas of exercise immunology that have received the most attention from investigators :(1) acute and chronic effects of exercise on the immune system,(2) clinical benefits of the exercise—immune relationship,(3) nutritional influen?ces on the immune response to exercise, and(4) the effect of exercise on immunosenescence. These scientific discoveries can be organized into distinctive time periods: 1900-1979, which focused on exercise-induced changes in basic immune cell counts and function; 1980-1989, during which seminal papers were published with evidence that heavy exertion was associated with transient immune dysfunction, elevated inflammatory biomarkers,and increased risk of upper respiratory tract infections; 1990-2009, when additional focus areas were added to the field of exercise immunology including the interactive effect of nutrition, effects on the aging immune system, and inflammatory cytokines; and 2010 to the present, when technological advances in mass spectrometry allowed system biology approaches(i.e., metabolomics, proteomics, lipidomics, and microbiome characterization) to be applied to exercise immunology studies. The future of exercise irmmunology will take advantage of these technologies to provide new insights on the interactions between exercise, nutrition, and immune function, with application down to the person?alized level. Additionally, these methodologies will improve mechanistic understanding of how exercise-induced immune perturbations reduce the risk of common chronic diseases.展开更多
Concussion,or mild traumatic brain injury,incidence rates have reached epidemic levels and impaired postural control is a cardinal symptom.The purpose of this review is to provide an overview of the linear and non-lin...Concussion,or mild traumatic brain injury,incidence rates have reached epidemic levels and impaired postural control is a cardinal symptom.The purpose of this review is to provide an overview of the linear and non-linear assessments of post-concussion postural control.The current acute evaluation for concussion utilizes the subjective balance error scoring system(BESS) to assess postural control.While the sensitivity of the overall test battery is high,the sensitivity of the BESS is unacceptably low and,with repeat administration,is unable to accurately identify recovery.Sophisticated measures of postural control,utilizing traditional linear assessments,have identified impairments in postural control well beyond BESS recovery.Both assessments of quiet stance and gait have identified lingering impairments for at least 1 month post-concussion.Recently,the application of non-linear metrics to concussion recovery have begun to receive limited attention with the most commonly utilized metric being approximate entropy(Ap En).Ap En,most commonly in the medial-lateral plane,has successfully identified impaired postural control in the acute post-concussion timeframe even when linear assessments of instrumented measures are equivalent to healthy pre-injury values;unfortunately these studies have not gone beyond the acute phase of recovery.One study has identified lingering deficits in postural control,utilizing Shannon and Renyi entropy metrics,which persist at least through clinical recovery and return to participation.Finally,limited evidence from two studies suggest that individuals with a previous history of a single concussion,even months or years prior,may display altered Ap En metrics.Overall,non-linear metrics provide a fertile area for future study to further the understanding of postural control impairments acutely post-concussion and address the current challenge of sensitive identification of recovery.展开更多
It is well acknowledged that muscles that are elongated while activated(i.e.,eccentric muscle action)are stronger and require less energy(per unit of force)than muscles that are shortening(i.e.,concentric contraction)...It is well acknowledged that muscles that are elongated while activated(i.e.,eccentric muscle action)are stronger and require less energy(per unit of force)than muscles that are shortening(i.e.,concentric contraction)or that remain at a constant length(i.e.,isometric contraction).Although the cross-bridge theory of muscle contraction provides a good explanation for the increase in force in active muscle lengthening,it does not explain the residual increase in force following active lengthening(residual force enhancement),or except with additional assumptions,the reduced metabolic requirement of muscle during and following active stretch.Aside from the cross-bridge theory,2 other primary explanations for the mechanical properties of actively stretched muscles have emerged:(1)the so-called sarcomere length nonuniformity theory and(2)the engagement of a passive structural element theory.In this article,these theories are discussed,and it is shown that the last of these—the engagement of a passive structural element in eccentric muscle action—offers a simple and complete explanation for many hitherto unexplained observations in actively lengthening muscle.Although by no means fully proven,the theory has great appeal for its simplicity and beauty,and even if over time it is shown to be wrong,it nevertheless forms a useful framework for direct hypothesis testing.展开更多
In many countries,sedentary lifestyle has led to a number of epidemic health problems,including obesity,metabolic syndrome,and associated comorbidities.Countries have performed self-evaluations of the fitness status o...In many countries,sedentary lifestyle has led to a number of epidemic health problems,including obesity,metabolic syndrome,and associated comorbidities.Countries have performed self-evaluations of the fitness status of their people:children,young adults,and the elderly.Policies for increased school-based physical education,and financial展开更多
Several decades of research in the area of exercise immunology have shown that the immune system is highly responsive to acute and chronic exercise training.Moderate exercise bouts enhance immunosurveillance and when ...Several decades of research in the area of exercise immunology have shown that the immune system is highly responsive to acute and chronic exercise training.Moderate exercise bouts enhance immunosurveillance and when repeated over time mediate multiple health benefits.Most of the studies prior to 2010 relied on a few targeted outcomes related to immune function.During the past decade,technologic advances have created opportunities for a multi-omics and systems biology approach to exercise immunology.This article provides an overview of metabolomics,lipidomics,and proteomics as they pertain to exercise immunology,with a focus on immunometabolism.This review also summarizes how the composition and diversity of the gut microbiota can be influenced by exercise,with applications to human health and immunity.Exercise-induced improvements in immune function may play a critical role in countering immunosenescence and the development of chronic diseases,and emerging omics technologies will more clearly define the underlying mechanisms.This review summarizes what is currently known regarding a multi-omics approach to exercise immunology and provides future directions for investigators.展开更多
Purpose: The aim of this study was to compare mechanical muscle function in the eccentric/concentric phases of vertical bilateral jumping in anterior cruciate ligament-reconstructed(ACLR), elite(ELITE), and adolescent...Purpose: The aim of this study was to compare mechanical muscle function in the eccentric/concentric phases of vertical bilateral jumping in anterior cruciate ligament-reconstructed(ACLR), elite(ELITE), and adolescent(ADOL) alpine ski racers and ski cross athletes.Methods: Alpine ski racers/ski crossers(ACLR: n = 12, age = 26.7 § 3.8 years; ELITE: n = 12, age = 23.9 § 3.0 years; ADOL: n = 12, age = 17.8§ 0.7 years; females: n = 6 per group, males: n = 6 per group) performed 5 maximal countermovement jumps(CMJs) and 5 squat jumps. The ground reaction forces for each limb were analyzed using dual force plate recording to obtain body center of mass(BCM) velocity, displacement,and power. The eccentric deceleration(ECC) and concentric phases were determined from BCM velocity. CMJ net concentric and ECC impulses were calculated(body mass normalized) along with the peak and mean BCM power and maximal vertical jump height. CMJ lower limb stiffness(LLS) was determined by the slope of the ground reaction forces vs. the BCM displacement curve over the ECC phase. Concentric and ECC asymmetry indices were calculated for each leg, and the left vs. right LLS was compared. Outcome measures(reported as mean § SD) calculated as a 5-jump mean were normalized to body mass and compared using an analysis of variance.Results: No between-group differences were found for peak and mean power or jump heights. There were no group differences for LLS or net concentric phase impulse, but the net ECC impulse was lower in the ADOL group compared with ELITE skiers(ADOL: 1.33 § 0.32 Ns/kg;ELITE: 1.59 § 0.16 Ns/kg; p < 0.05). Although no group differences were found for ECC asymmetry indices, a group ￡ limb interaction was found for LLS(p < 0.01), which was systematically higher in the right vs. the left limb of ADOL skiers(right: 54.1 § 17.9 N/m/kg; left: 48.7 §15.7 N/m/kg; p < 0.01).Conclusion: ADOL skiers demonstrated decreased ECC impulse and systematic right limb dominance in LLS compared with ACLR and ELITE skiers. The implication of these findings for injury and performance are unknown, but further investigation into these potential relationships is warranted.展开更多
I entered my first running race(a 60-m sprint)when I was 6years old,and have run and competed ever since for the past 55years.When I was 19 years old,I entered the Physical Education program at the Federal Technical I...I entered my first running race(a 60-m sprint)when I was 6years old,and have run and competed ever since for the past 55years.When I was 19 years old,I entered the Physical Education program at the Federal Technical Institute in Zurich,where I became exposed to running and running injury research,and although I have never researched running myself,through展开更多
In their recent papers in the Journal of Sport and Health Science on hamstring injuries in sprinting,^(1,2)and their corresponding commentaries on each other's research,3,4Yu et al.and Liu et al.proposed different...In their recent papers in the Journal of Sport and Health Science on hamstring injuries in sprinting,^(1,2)and their corresponding commentaries on each other's research,3,4Yu et al.and Liu et al.proposed different views of the mechanisms of muscle injuries in general,and hamstring injuries in sprinting specifically.While Yu et al.^(1,3)argued that muscle injuries are primarily,if not exclusively,caused by muscle strain magnitude in eccentric contractions,and thus hamstring injuries occur primarily展开更多
Maintaining leanness and a physically active lifestyle during adulthood reduces systemic inflammation,an underlying factor in multiple chronic diseases.The anti-inflammatory influence of near-daily physical activity i...Maintaining leanness and a physically active lifestyle during adulthood reduces systemic inflammation,an underlying factor in multiple chronic diseases.The anti-inflammatory influence of near-daily physical activity in lowering C-reactive protein,total blood leukocytes,interleukin -6,and other inflammatory cytokines may play a key role in lowering risk of cardiovascular disease,certain types of cancer,type 2 diabetes,sarcopenia,and dementia.Moderate exercise training causes favorable perturbations in immunity and a reduction in incidence of upper respiratory tract infection(URTI).During each bout of moderate exercise,an enhanced recirculation of immunoglobulins,neutrophils,and natural killer cells occurs that persists for up to 3-h post-exercise.This exercise-induced surge in immune cells from the innate immune system is transient but improves overall surveillance against pathogens.As moderate exercise continues on a near-daily basis for 12—15 weeks,the number of symptoms days with URTI is decreased 25%—50%compared to randomized sedentary controls.Epidemiologic and animal studies support this inverse relationship between URTI risk and increased physical activity.展开更多
Physical inactivity is a well-established risk factor for chronic diseases,such as cardiovascular disease,cancer,and diabetes mellitus.There is a growing awareness that physical inactivity should also be regarded as a...Physical inactivity is a well-established risk factor for chronic diseases,such as cardiovascular disease,cancer,and diabetes mellitus.There is a growing awareness that physical inactivity should also be regarded as a risk factor for acute respiratory infections(ARIs).ARIs,such as the common cold,influenza,pneumonia,and coronavirus disease 2019(COVID-19),are among the most pervasive diseases on earth and cause widespread morbidity and mortality.Evidence in support of the linkage between ARIs and physical inactivity has been strengthened during the COVID-19 pandemic because of increased scientific scrutiny.Large-scale studies have consistently reported that the risk for severe COVID-19 outcomes is elevated in cohorts with low physical activity and/or physical fitness,even after adjusting for other risk factors.The lowered risk for severe COVID-19 and other ARIs in physically active groups is attributed to exercise-induced immunoprotective effects,including enhanced surveillance of key immune cells and reduced chronic inflammation.Scientific consensus groups,including those who submitted the Physical Activity Guidelines for Americans,have not yet given this area of research the respect that is due.It is time to add“reduced risk for ARIs”to the“Exercise is Medicine”list of physical activity-related health benefits.展开更多
文摘Space travel since the 1960s has led to a number of physiological alterations to homeostasis in astronauts. Extensive variation in the pattern of responses observed has led a concerted effort to develop countermeasures to overcome such changes and restore homeostasis, and thus “health” is defined as more “Earth-like”. These adaptations to a space environment by a species which evolved and normally exists in the 1 g environment, the geomagnetic field, and background radiation of Earth are viewed as threats to health as defined by the conditions of Earth. Exposure to space can lead to alterations in genomic stability and epigenetic signatures, alterations which could redefine “health” and responses to risks for loss of health for those who will return to Earth. In contrast, in the future individuals born in non-Earth space environments will likely develop an integrated metabolic set point defined by those conditions. They will thus be shaped by both the local environments, and space-associated genomic/epigenomic alterations to their parents. Therefore, such an altered set point for those born and raised in non-Earth space environments will potentially have physiological and molecular consequences which may lead to either new evolutionary adaptation, or to compromise of long term health due to drastically altered set points for integrated physiologic function which is at odds with the evolutionary history of humans. The implications of the two options will be critical for defining “health” in altered environments encountered during space ventures, as well as providing insights into the regulation of human integrity at the physiological level. Therefore, the definition of “health” is dependent on the boundary conditions surrounding development and maturation, and is a dynamic concept.
文摘With the Rio Olympics just a few months past,we remember the excitement,the incredible performances,and the controversies.As happens so often,the Olympic Games focus attention not only on athletic achievements but also on how athletes may reach ever-increasing levels of performance.Doping,medical
文摘Objective:We reviewed and appraised the existing evidence of in vivo manifestations of residual force enhancement in human skeletal muscles and assessed,through a meta-analysis,the effect of an immediate history of eccentric contraction on the subsequent torque capacity of voluntary and electrically evoked muscle contractions.Methods:Our search was conducted from database inception to May 2020.Descriptive information was extracted from,and quality was assessed for,45 studies.Meta-analyses and metaregressions were used to analyze residual torque enhancement and its dependence on the angular amplitude of the preceding eccentric contraction.Results:Procedures varied across studies with regards to muscle group tested,angular stretch amplitude,randomization of contractions,time window analyzed,and verbal command.Torque capacity in isometric(constant muscle tendon unit length and joint angle)contractions preceded by an eccentric contraction was typically greater compared to purely isometric contractions,and this effect was greater for electrically evoked muscle contractions than voluntary contractions.Residual torque enhancement differed across muscle groups for the voluntary contractions,with a significant enhancement in torque observed for the adductor pollicis,ankle dorsiflexors,ankle plantar flexors,and knee extensors,but not for the elbow and knee flexors.Meta-regressions revealed that the angular amplitude of the eccentric contraction(normalized to the respective joints full range of motion)was not associated with the residual torque enhancement observed.Conclusion:There is evidence of residual torque enhancement for most,but not all,muscle groups,and residual torque enhancement is greater for electrically evoked than for voluntary contractions.Contrary to our hypothesis,and contrary to generally accepted findings on isolated muscle preparations,residual torque enhancement in voluntary and electrically evoked contractions does not seem to depend on the angular amplitude of the preceding eccentric contraction.
文摘Hybrid journals are journals that provide both of 2 common publication options:(a)the traditional approach,where either institutions pay for a subscription or readers purchase individual articles(free of charge for the submitting author);and(b)open access,where articles are accessible without a subscription and free of charge for the reader(the submitting author typically pays an article processing charge).Hybrid journals earn a fixed amount of money from subscriptions,and they earn additional income from the article processing charges associated with their open access option.A hybrid journal can increase its income by publishing a greater number of open access articles.
文摘Purpose:This study aimed to examine the reliability and validity of load-velocity(L-V)relationship variables obtained through the 2-point method using different load combinations and velocity variables.Methods:Twenty men performed 2 identical sessions consisting of 2 countermovement jumps against 4 external loads(20 kg,40 kg,60 kg,and80 kg)and a heavy squat against a load linked to a mean velocity(MV)of 0.55 m/s(load_(0.55)).The L-V relationship variables(load-axis intercept(L_(0)),velocity-axis intercept(v_(0)),and area under the L-V relationship line(A_(line)))were obtained using 3 velocity variables(MV,mean propulsive velocity(MPV),and peak velocity)by the multiple-point method including(20-40-60-80-load_(0.55))and excluding(20-40-60-80)the heavy squat,as well as from their respective 2-point methods(20-load_(0.55)and 20-80).Results:The L-V relationship variables were obtained with an acceptable reliability(coefncient of variation(CV)≤7.30%;intra-class correlation coefficient>0.63).The reliability of L_(0)and v_(0)was comparable for both methods(CV_(ratio)(calculated as higher value/lower value):1.11-1.12),but the multiple-point method provided Al_(ine)with a greater reliability(CV_(ratio)=1.26).The use of a heavy squat provided the L-V relationship variables with a comparable or higher reliability than the use of a heavy countermovement jump load(CV_(ratio):1.06-1.19).The peak velocity provided the load-velocity relationship variables with the greatest reliability(CV_(ratio):1.15-1.86)followed by the MV(CV_(ratio):1.07-1.18),and finally the MPV.The 2-point methods only revealed an acceptable validity for the MV and MPV(effect size≤0.19;Pearson s product-moment correlation coefficient≥0.96;Lin's concordance correlation coefficient≥0.94).Conclusion:The 2-point method obtained from a heavy squat load and MV or MPV is a quick,safe,and reliable procedure to evaluate the lower-body maximal neuromuscular capacities through the L-V relationship.
文摘This review summarizes research discoveries within 4 areas of exercise immunology that have received the most attention from investigators :(1) acute and chronic effects of exercise on the immune system,(2) clinical benefits of the exercise—immune relationship,(3) nutritional influen?ces on the immune response to exercise, and(4) the effect of exercise on immunosenescence. These scientific discoveries can be organized into distinctive time periods: 1900-1979, which focused on exercise-induced changes in basic immune cell counts and function; 1980-1989, during which seminal papers were published with evidence that heavy exertion was associated with transient immune dysfunction, elevated inflammatory biomarkers,and increased risk of upper respiratory tract infections; 1990-2009, when additional focus areas were added to the field of exercise immunology including the interactive effect of nutrition, effects on the aging immune system, and inflammatory cytokines; and 2010 to the present, when technological advances in mass spectrometry allowed system biology approaches(i.e., metabolomics, proteomics, lipidomics, and microbiome characterization) to be applied to exercise immunology studies. The future of exercise irmmunology will take advantage of these technologies to provide new insights on the interactions between exercise, nutrition, and immune function, with application down to the person?alized level. Additionally, these methodologies will improve mechanistic understanding of how exercise-induced immune perturbations reduce the risk of common chronic diseases.
文摘Concussion,or mild traumatic brain injury,incidence rates have reached epidemic levels and impaired postural control is a cardinal symptom.The purpose of this review is to provide an overview of the linear and non-linear assessments of post-concussion postural control.The current acute evaluation for concussion utilizes the subjective balance error scoring system(BESS) to assess postural control.While the sensitivity of the overall test battery is high,the sensitivity of the BESS is unacceptably low and,with repeat administration,is unable to accurately identify recovery.Sophisticated measures of postural control,utilizing traditional linear assessments,have identified impairments in postural control well beyond BESS recovery.Both assessments of quiet stance and gait have identified lingering impairments for at least 1 month post-concussion.Recently,the application of non-linear metrics to concussion recovery have begun to receive limited attention with the most commonly utilized metric being approximate entropy(Ap En).Ap En,most commonly in the medial-lateral plane,has successfully identified impaired postural control in the acute post-concussion timeframe even when linear assessments of instrumented measures are equivalent to healthy pre-injury values;unfortunately these studies have not gone beyond the acute phase of recovery.One study has identified lingering deficits in postural control,utilizing Shannon and Renyi entropy metrics,which persist at least through clinical recovery and return to participation.Finally,limited evidence from two studies suggest that individuals with a previous history of a single concussion,even months or years prior,may display altered Ap En metrics.Overall,non-linear metrics provide a fertile area for future study to further the understanding of postural control impairments acutely post-concussion and address the current challenge of sensitive identification of recovery.
文摘It is well acknowledged that muscles that are elongated while activated(i.e.,eccentric muscle action)are stronger and require less energy(per unit of force)than muscles that are shortening(i.e.,concentric contraction)or that remain at a constant length(i.e.,isometric contraction).Although the cross-bridge theory of muscle contraction provides a good explanation for the increase in force in active muscle lengthening,it does not explain the residual increase in force following active lengthening(residual force enhancement),or except with additional assumptions,the reduced metabolic requirement of muscle during and following active stretch.Aside from the cross-bridge theory,2 other primary explanations for the mechanical properties of actively stretched muscles have emerged:(1)the so-called sarcomere length nonuniformity theory and(2)the engagement of a passive structural element theory.In this article,these theories are discussed,and it is shown that the last of these—the engagement of a passive structural element in eccentric muscle action—offers a simple and complete explanation for many hitherto unexplained observations in actively lengthening muscle.Although by no means fully proven,the theory has great appeal for its simplicity and beauty,and even if over time it is shown to be wrong,it nevertheless forms a useful framework for direct hypothesis testing.
文摘In many countries,sedentary lifestyle has led to a number of epidemic health problems,including obesity,metabolic syndrome,and associated comorbidities.Countries have performed self-evaluations of the fitness status of their people:children,young adults,and the elderly.Policies for increased school-based physical education,and financial
基金supported by an operating grant to Dr.Charles Rice from the Natural Sciences and Engineering Research Council of Canada (NSERC)supported by the Canadian Institutes of Health Research (CIHR)+1 种基金the Michael Smith Foundation for Health Research (MSFHR)supported by Alberta Innovates Health Solutions (AIHS)
文摘Several decades of research in the area of exercise immunology have shown that the immune system is highly responsive to acute and chronic exercise training.Moderate exercise bouts enhance immunosurveillance and when repeated over time mediate multiple health benefits.Most of the studies prior to 2010 relied on a few targeted outcomes related to immune function.During the past decade,technologic advances have created opportunities for a multi-omics and systems biology approach to exercise immunology.This article provides an overview of metabolomics,lipidomics,and proteomics as they pertain to exercise immunology,with a focus on immunometabolism.This review also summarizes how the composition and diversity of the gut microbiota can be influenced by exercise,with applications to human health and immunity.Exercise-induced improvements in immune function may play a critical role in countering immunosenescence and the development of chronic diseases,and emerging omics technologies will more clearly define the underlying mechanisms.This review summarizes what is currently known regarding a multi-omics approach to exercise immunology and provides future directions for investigators.
基金the Killam Foundation provided funding for this research
文摘Purpose: The aim of this study was to compare mechanical muscle function in the eccentric/concentric phases of vertical bilateral jumping in anterior cruciate ligament-reconstructed(ACLR), elite(ELITE), and adolescent(ADOL) alpine ski racers and ski cross athletes.Methods: Alpine ski racers/ski crossers(ACLR: n = 12, age = 26.7 § 3.8 years; ELITE: n = 12, age = 23.9 § 3.0 years; ADOL: n = 12, age = 17.8§ 0.7 years; females: n = 6 per group, males: n = 6 per group) performed 5 maximal countermovement jumps(CMJs) and 5 squat jumps. The ground reaction forces for each limb were analyzed using dual force plate recording to obtain body center of mass(BCM) velocity, displacement,and power. The eccentric deceleration(ECC) and concentric phases were determined from BCM velocity. CMJ net concentric and ECC impulses were calculated(body mass normalized) along with the peak and mean BCM power and maximal vertical jump height. CMJ lower limb stiffness(LLS) was determined by the slope of the ground reaction forces vs. the BCM displacement curve over the ECC phase. Concentric and ECC asymmetry indices were calculated for each leg, and the left vs. right LLS was compared. Outcome measures(reported as mean § SD) calculated as a 5-jump mean were normalized to body mass and compared using an analysis of variance.Results: No between-group differences were found for peak and mean power or jump heights. There were no group differences for LLS or net concentric phase impulse, but the net ECC impulse was lower in the ADOL group compared with ELITE skiers(ADOL: 1.33 § 0.32 Ns/kg;ELITE: 1.59 § 0.16 Ns/kg; p < 0.05). Although no group differences were found for ECC asymmetry indices, a group ￡ limb interaction was found for LLS(p < 0.01), which was systematically higher in the right vs. the left limb of ADOL skiers(right: 54.1 § 17.9 N/m/kg; left: 48.7 §15.7 N/m/kg; p < 0.01).Conclusion: ADOL skiers demonstrated decreased ECC impulse and systematic right limb dominance in LLS compared with ACLR and ELITE skiers. The implication of these findings for injury and performance are unknown, but further investigation into these potential relationships is warranted.
文摘I entered my first running race(a 60-m sprint)when I was 6years old,and have run and competed ever since for the past 55years.When I was 19 years old,I entered the Physical Education program at the Federal Technical Institute in Zurich,where I became exposed to running and running injury research,and although I have never researched running myself,through
文摘In their recent papers in the Journal of Sport and Health Science on hamstring injuries in sprinting,^(1,2)and their corresponding commentaries on each other's research,3,4Yu et al.and Liu et al.proposed different views of the mechanisms of muscle injuries in general,and hamstring injuries in sprinting specifically.While Yu et al.^(1,3)argued that muscle injuries are primarily,if not exclusively,caused by muscle strain magnitude in eccentric contractions,and thus hamstring injuries occur primarily
文摘Maintaining leanness and a physically active lifestyle during adulthood reduces systemic inflammation,an underlying factor in multiple chronic diseases.The anti-inflammatory influence of near-daily physical activity in lowering C-reactive protein,total blood leukocytes,interleukin -6,and other inflammatory cytokines may play a key role in lowering risk of cardiovascular disease,certain types of cancer,type 2 diabetes,sarcopenia,and dementia.Moderate exercise training causes favorable perturbations in immunity and a reduction in incidence of upper respiratory tract infection(URTI).During each bout of moderate exercise,an enhanced recirculation of immunoglobulins,neutrophils,and natural killer cells occurs that persists for up to 3-h post-exercise.This exercise-induced surge in immune cells from the innate immune system is transient but improves overall surveillance against pathogens.As moderate exercise continues on a near-daily basis for 12—15 weeks,the number of symptoms days with URTI is decreased 25%—50%compared to randomized sedentary controls.Epidemiologic and animal studies support this inverse relationship between URTI risk and increased physical activity.
文摘Physical inactivity is a well-established risk factor for chronic diseases,such as cardiovascular disease,cancer,and diabetes mellitus.There is a growing awareness that physical inactivity should also be regarded as a risk factor for acute respiratory infections(ARIs).ARIs,such as the common cold,influenza,pneumonia,and coronavirus disease 2019(COVID-19),are among the most pervasive diseases on earth and cause widespread morbidity and mortality.Evidence in support of the linkage between ARIs and physical inactivity has been strengthened during the COVID-19 pandemic because of increased scientific scrutiny.Large-scale studies have consistently reported that the risk for severe COVID-19 outcomes is elevated in cohorts with low physical activity and/or physical fitness,even after adjusting for other risk factors.The lowered risk for severe COVID-19 and other ARIs in physically active groups is attributed to exercise-induced immunoprotective effects,including enhanced surveillance of key immune cells and reduced chronic inflammation.Scientific consensus groups,including those who submitted the Physical Activity Guidelines for Americans,have not yet given this area of research the respect that is due.It is time to add“reduced risk for ARIs”to the“Exercise is Medicine”list of physical activity-related health benefits.
