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Chronic training status affects muscle excitation of the vastus lateralis during repeated contractions

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运动医学与健康科学(英文) 2023年第1期5卷 42-49页

作者： Sunggun Jeon Stephanie A.Sontag Trent J.Herda Michael A.Trevino Applied Neuromuscular Physiology laboratory Department of KinesiologyApplied Healthand RecreationOklahoma State UniversityStillwaterOKUSA Neuromechanics laboratory Department of HealthSportand Exercise SciencesThe University of KansasLawrenceKSUSA

This study examined electromyographic amplitude(EMGRMS)-force relationships during repeated submaximal knee extensor muscle actions among chronic aerobically-(AT),resistance-trained(RT),and sedentary(SED)*** adults(5/group)attempted 20 isometric trapezoidal muscle actions at 50%of maximal *** electromyography(EMG)was recorded from vastus lateralis(VL)during the muscle *** the first and last successfully completed contractions,linear regression models were fit to the log-transformed EMGRMS-force relationships during the linearly increasing and decreasing segments,and the b terms(slope)and a terms(antilog of y-intercept)were *** was averaged during steady *** the AT completed all 20 muscle *** the first contraction,the b terms for RT(1.3010.197)were greater than AT(0.9100.123;p?0.008)and SED(0.9120.162;p?0.008)during the linearly increasing segment,and in comparison to the linearly decreasing segment(1.0180.139;p?0.014),*** the last contraction,the b terms for RT were greater than AT during the linearly increasing(RT?1.3730.353;AT?0.8830.129;p?0.018)and decreasing(RT?1.5260.328;AT?0.9700.223;p?0.010)*** addition,the b terms for SED increased from the linearly increasing(0.9680.144)to decreasing segment(1.2680.126;p?0.015).There were no training,segment,or contraction differences for the a *** during steady force increased from the first-([64.0851.68]μV)to last-contraction([86.7349.55]μV;p?0.001)collapsed across training *** b terms differentiated the rate of change for EMGRMS with increments in force among training groups,indicating greater muscle excitation to the motoneuron pool was necessary for the RT than AT during the linearly increasing and decreasing segments of a repetitive task.

关键词： Electromyography Fatigue Isometric trapezoidal muscle action Motor unit control properties Natural log-transformed model Vastus lateralis

Comparing dynamical systems concepts and techniques for biomechanical analysis

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Journal of Sport and Health Science 2016年第1期5卷 3-13页

作者： Richard E.A.van Emmerik Scott W.Ducharme Avelino C.Amado Joseph Hamill Motor Control laboratory Department of Kinesiology University of Massachusetts Amherst Amherst MA 01003 USA Biomechanics Laboratories Department of Kinesiology University of Massachusetts Amherst Amherst MA 01003 USA

Traditional biomechanical analyses of human movement are generally derived from linear *** these methods can be useful in many situations,they do not describe behaviors in human systems that are predominately *** this reason,nonlinear analysis methods based on a dynamical systems approach have become more prevalent in recent *** analysis techniques have provided new insights into how systems(1) maintain pattern stability,(2) transition into new states,and(3) are governed by short-and long-term(fractal) correlational processes at different spatio-temporal *** different aspects of system dynamics are typically investigated using concepts related to variability,stability,complexity,and *** purpose of this paper is to compare and contrast these different concepts and demonstrate that,although related,these terms represent fundamentally different aspects of system *** particular,we argue that variability should not uniformly be equated with stability or complexity of *** addition,current dynamic stability measures based on nonlinear analysis methods(such as the finite maximal Lyapunov exponent) can reveal local instabilities in movement dynamics,but the degree to which these local instabilities relate to global postural and gait stability and the ability to resist external perturbations remains to be ***,systematic studies are needed to relate observed reductions in complexity with aging and disease to the adaptive capabilities of the movement system and how complexity changes as a function of different task constraints.

关键词： Adaptability Complexity Dynamical systems Nonlinear dynamics Stability Variability

Hypoxic training methods for improving endurance exercise performance

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Journal of Sport and Health Science 2015年第4期4卷 325-332页

作者： Jacob A. Sinex Robert E Chapman School of Public Health Department of Kinesiology Human Performance Laboratory Indiana University Bloomington IN 47401 USA

Endurance athletic performance is highly related to a number of fiactors that can be altered through altitude and hypoxic training including increases in erythrocyte volume, maximal aerobic exercise capacity, capillary density, and economy. Physiological adaptations in response to acute and chronic exposure to hypoxic environments are well documented and range from short-term detrimental effects to longer-term adaptations that can improve performance at altitude and in sea-level competitions. Many altitude and hypoxic training protocols have been developed, employing various combinations of living and training at sea-level, low, moderate, and high altitudes and utilizing natural and artificial altitudes, with varying degrees of effectiveness. Several factors have been identified that are associated with individual responses to hypoxic training, and techniques for identifying those athletes most likely to benefit from hypoxic trairdng continue to be investigated. Exposure to sufficiently high altitude （2000-3000 m） for more than 12 h/day, while training at lower altitudes, for a minimum of 21 days is recommended. Timing of altitude training related to competition remains under debate, although general recommendations can be considered.

关键词： Altitude Hypoxia Performance Training

Cardiac remodeling and physical training post myocardial infarction

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World Journal of Cardiology 2015年第2期7卷 52-64页

作者： Michael A Garza Emily A Wason John Q Zhang laboratory of Cardiovascular Research Department of Health Kinesiologyand Nutrition University of Texas at San Antonio

After myocardial infarction(MI), the heart undergoes extensive myocardial remodeling through the accumulation of fibrous tissue in both the infarcted and noninfarcted myocardium, which distorts tissue structure, increases tissue stiffness, and accounts for ventricular dysfunction. There is growing clinical consensus that exercise training may beneficially alter the course of post-MI myocardial remodeling and improve cardiac function. This review summarizes the present state of knowledge regarding the effect of post-MI exercise training on infarcted hearts. Due to the degree of difficulty to study a viable human heart at both protein and molecular levels, most of the detailed studies have been performed by using animal models. Although there are some negative reports indicating that post-MI exercise may further cause deterioration of the wounded hearts, a growing body of research from both human and animal experiments demonstrates that post-MI exercise may beneficially alter the course of wound healing and improve cardiac function. Furthermore, the improved function is likely due to exercise training-induced mitigation of reninangiotensin-aldosterone system, improved balance between matrix metalloproteinase-1 and tissue inhibitor of matrix metalloproteinase-1, favorable myosin heavy chain isoform switch, diminished oxidative stress, enhanced antioxidant capacity, improved mitochondrial calcium handling, and boosted myocardial angiogenesis. Additionally, meta-analyses revealed that exercise-based cardiac rehabilitation has proven to be effective, and remains one of the least expensive therapies for both the prevention and treatment of cardiovascular disease, and prevents re-infarction.

关键词： Post-myocardial infarction Exercise training Myocardial remodeling Angiotensin Ⅱ Fibrosis

Joint Contact Forces with Changes in Running Stride Length and Midsole Stiffness

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Journal of Science in Sport and Exercise 2020年第1期2卷 69-76页

作者： Joshua M.Thomas WBrent Edwards Timothy R.Derrick Department of Health Wellnessand SportUniversity of DubuqueDubuqueIA 52001USA Human Performance laboratory Faculty of KinesiologyUniversity of CalgaryCalgaryAB T2N 1N4Canada Department of kinesiology Iowa State University111L Forker BuildingAmesIA 50011USA

The purpose of this study was to determine if lower extremity joint loading was influenced by stride length or shoe midsole *** subjects completed 10 trials of overground running at an average speed of 4.43 m/s in each of three condi-tions:normal running,running with a stride length(SL)reduced by 10%of normal,and running with a cushioned midsole stiffness(i.e.,mechanical impact reduction of 13.7-10.9 g).Reaction forces calculated from inverse dynamics were summed with muscle forces estimated from a musculoskeletal model using static optimization to obtain joint contact forces at the hip,knee and ankle *** components of the contact forces[axial,anterior-posterior,and medial-lateral(ML)]were examined using parametric statistics(α=0.05).Reducing stride length resulted in significant decreases in absolute peak ankle contact forces in the axial direction(normal:-14.5±1.5 BW;reduced SL:-14.0±1.6 BW)and the ML direction(normal:0.67±0.23 BW;reduced SL:0.61±0.21 BW).Reducing stride length also reduced the peak absolute axial forces at the knee(normal:-10.6±1.3 BW;reduced SL:-9.8±1.2 BW)and the hip(normal:-7.26±2.24 BW;reduced SL:-6.75±2.10 BW).The cushioned shoe did not statistically reduce the peak absolute contact forces from the normal stride condition at any of the *** hoc stress analysis suggested that the observed changes in anterior hip force would increase stress more than any of the other statistically significant *** in stride length appear to decrease some joint contact variables but cushioning in the heel region of the shoe does not.

关键词： Gait Injury Compressive force Shear force Cushioning Strain

Ad libitum water consumption prevents exercise-associated hyponatremia and protects against dehydration in soldiers performing a 40-km route-march

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Military Medical Research 2019年第3期6卷 201-207页

作者： Heinrich WNolte Kim Nolte Tamara Hew-Butler Movement Physiology Research laboratory School of PhysiologyFaculty of Health SciencesUniversity of the WitwatersrandJohannesburgSouth Africa Division Biokinetics and Sport Science Department of PhysiologyUniversity of PretoriaPretoriaSouth Africa Division of kinesiology Wayne State UniversityDetroitMIUSA.

Background: It remains unclear if ad libitum water drinking, as a hydration strategy, prevents exercise-associated hyponatremia(EAH) during prolonged exercise. The aim of this study was to determine the incidence of EAH within the broader context of fluid regulation among soldiers performing a 40-km route-march ingesting water ad ***: Twenty-eight healthy male soldiers participated in this observational trial. Pre-and post-exercise body mass, blood and urine samples were collected. Blood samples were assessed for serum sodium([Na+]), glucose, creatinine, urea nitrogen(BUN), plasma osmolality, creatine kinase(CK), and plasma arginine vasopressin(AVP) concentrations. Plasma volume(PV) was calculated using hematocrit and hemoglobin. Urine samples were analyzed for osmolality and (Na+)Water intake was assessed by weighing bottles before, during and after the march. The mean relative humidity was 55.7%(21.9–94.3%) and the mean dry bulb temperature was 27.1°C(19.5°C-37.0°C) during the ***: Twenty-five soldiers(72±10 kg)(Mean±SD) completed the march in 09:11±00:43(hr:min). Participants consumed 736±259 ml/h of water and lost 2.8±0.9 kg(4.0%±1.4%, P<0.05) of body mass. Significant(pre-march vs. post-march;P<0.05) decreases in serum [Na+](141 mmol/L vs. 136 mmol/L), plasma osmolality(303 m Osmol/kg H2O vs. 298 m Osmol/kg H2O), and serum creatinine(111 μmol/L vs. 101 μmol/L) and urine [Na+](168 mmol/L vs. 142 mmol/L), as well as significant increases in plasma AVP(2 pg/ml vs. 11 pg/ml), plasma CK(1423 U/L vs. 3894 U/L) and urine osmolality(1035 m Osmol/kg H2O vs. 1097 m Osmol/kg H2O) were found. The soldier(72 kg) with the lowest postexercise sodium level completed the march in 08:38. He drank 800 ml/h, lost 2% body mass, and demonstrated(prepost) increases in plasma osmolality(294–314 m Osmol/kg H2O), BUN(20–30 mg/dl), AVP(2–16 pg/ml) and PV(41%). His urine osmolality decreased from 1114 m Osmol/kg H2O to 1110 m Osmol/kg H2O. No participants finished

关键词： Serum sodium concentration Exercise-associated hyponatremia Arginine vasopressin Fluid balance Electrolyte balance Military

Sport and health are global issues

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Journal of Sport and Health Science 2012年第1期1卷 4-4页

作者： Walter Herzog Human Performance laboratory Faculty of KinesiologyUniversity of Calgary

One of the mandates I tried to embrace when I was president of the International Society of Biomechanics(2007-2009) was to foster,encourage,and bring to the limelight,the research activities from countries that were underrepresented internationally.I realized that such underrepresentation was often the result of barriers between scientific communities that had evolved historically,based on background,language, scientific method,financial support etc.,barriers that could easily be overcome by personal contacts,acknowledgement

关键词： encourage contacts overcome foster barriers evolve

Coactivation Does Not Contribute to Fatigue-Induced Decreases in Isokinetic Forearm Flexion and Extension Torque

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Journal of Science in Sport and Exercise 2023年第4期5卷 314-321页

作者： Tyler J.Neltner John Paul V.Anders Robert W.Smith Jocelyn E.Arnett Joshua L.Keller Terry J.Housh Richard J.Schmidt Glen O.Johnson Department of Nutrition and Health Sciences University of Nebraska-LincolnLincolnNE 68510USA Integrative laboratory of Exercise and Applied Physiology(iLEAP) Department of HealthKinesiology and SportUniversity of South AlabamaMobileAL 36688USA

Purpose The present study examined the effects of a reciprocal,slow velocity forearm flexion and extension task on fatigue-induced changes in isokinetic torque,agonist and antagonist muscle activation,and coactivation ratios at slow and moderate *** Nine women(mean±SD:age=21.0±1.7 years;body mass=68.1±8.2 kg;height=167.4±7.2 cm)completed pre-testing for forearm flexion and extension isokinetic peak torque at 60 and 180°/s,a fatiguing task of 50 maximal,recip-rocal,isokinetic muscle actions at 60°/s,and *** amplitude(AMP)of the electromyographic(EMG)signals from the biceps and triceps were simultaneously *** and EMG AMP were normalized to the corresponding values from the pre-testing peak torque *** measures ANOVAs and pairwise comparisons were used to identify mean changes in torque,EMG AMP,and coactivation *** The torque analyses indicated significant decreases from pre-to post-testing for forearm flexion(14.1%±5.0%;P0.05)from pre-to post-testing for either velocity or *** The torque responses were velocity-specific,with greater fatigability exhibited for forearm extension versus flexion at 60°/s,but no differences at 180°/*** parallel EMG AMP responses between the agonist and antagonist muscles for both velocities supported the lack of fatigue-induced changes in coactivation ***,our results demonstrated that fatigue-induced decreases in torque were not attributable to increases in antagonist activation or coactivation.

关键词： Coactivation Isokinetic Fatigue Forearm flexion Extension

Examining Gait Patterns after Total Knee Arthroplasty Using Parameterization and Principal Component Analysis

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Open Journal of Orthopedics 2013年第2期3卷 156-163页

作者： Kevin E. Roy Victoria L. Chester Chris A. McGibbon Andrew and Marjorie McCain Human Performance laboratory Faculty of Kinesiology University of New Brunswick Fredericton Canada

The use of parameterization in assessing gait waveforms has been widely accepted, although it is recognized that this approach excludes the majority of information contained in the waveform. Waveform analysis techniques, such as principal component analysis (PCA), have gained popularity in recent years as a more effective approach to extracting important information from human movement waveforms, but are more challenging to interpret. Few studies have compared these two different approaches to determine which yields the most relevant information. This study compared the kinematic patterns during gait of six total knee arthroplasty (TKA) subjects (10 TKA knees), to a group of 10 age-matched asymptomatic control subjects (19 control knees). An eight-camera Vicon M-cam system was used to track movement and compute joint angles. Group differences in parameterization (max and min peaks) values and principal component scores were tested using one-way ANOVA and Kruskal-Wallis tests. Using parameterization, the TKA group was characterized by reduced hip extension, increased hip flexion, increased anterior pelvic tilt, increased trunk tilt, and reduced sagittal ankle angles compared to the control group. Waveform analysis, by means of PCA, showed-magnitude shifts in sagittal ankle waveforms between groups, rather than solely reporting differences in peaks. Waveform analysis also indicated a significant shift in the magnitude of the entire waveform for hip angles, pelvic tilt, and trunk tilt, indicating no change in range of motion between groups, but rather a change in the way in which range of motion is achieved at the hip. This study has identified several gait variables that were significantly different between the TKA and control groups. Our results suggest that waveform analysis is effective at identifying magnitude shifts as sources of variability between groups, which would not necessarily be analyzed using conventional parameterization techniques unless one knew a pr

关键词： Total Knee Arthroplasty (TKA) Principal Component Analysis (PCA) Parameterization Gait Analysis