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1.
Artigo em Inglês | MEDLINE | ID: mdl-34979052

RESUMO

Women exhibit an attenuated exercise pressor reflex (EPR) when compared to men. The influence of sex-specific mechanisms related to the EPR and performance fatigability remain to be fully elucidated. The purpose was to determine the impact of oxygenation and metabolic efficiency on sex-specific performance fatigability and increases in mean arterial pressure (MAP) resulting from a fatiguing isometric handgrip (IHG). Twenty-four adults volunteered to perform an IHG at 25% at maximal voluntary isometric contractions (MVICs). Pre- and posttest MVICs were conducted to quantify performance fatigability. MAP was collected at 3 timepoints. A near-infrared spectroscopy device was attached to the forearm to derive the following signals: oxy[haem], deoxy[haem], total[haem], and diff[haem]. These values were normalized and examined across time in 5% segments of time-to-task-failure. Metabolic efficiency was defined as the ratio force:deoxy[haem]. During the IHG, there was a decline in oxy[haem] for the men (b = -0.075), whereas the women demonstrated an increase (b = 0.117). For the men, the diff[haem] tracked the mean oxy[haem] response, but there was no change for the women. The men exhibited greater declines in metabolic efficiency, yet there were no sex differences in PF (46.6 ± 9.7% vs. 45.5 ± 14.2%). For relative MAP, the men (24.5 ± 15.1%) exhibited a greater (p = .03) increase than the women (11.0 ± 17.6%). These results indicated the EPR was more prominent for the men, perhaps due to differences in mechanical stimuli and a lack of ability to maintain metabolic efficiency. However, these physiological differences did not induce a sex difference in performance fatigability.

2.
High Alt Med Biol ; 2021 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-34936812

RESUMO

Rivera, Paola M., Chris E. Proppe, Esther Beltran, and Ethan C. Hill. Acute effects of local ischemic hypoxia and systemic hypoxemia on neuromuscular and cognitive function. High Alt Med Biol. 00:000-000, 2021. Background: The application of blood flow restriction (BFR) induces local ischemic hypoxia within the muscle(s) distal to the restriction device. Systemic hypoxemia via oxygen or barometric pressure manipulation achieves whole-body hypoxia and thus may be a more potent exercise adjunct than BFR. Therefore, the purpose of this study was to examine the acute effects of local ischemic hypoxia versus systemic hypoxemia on maximal voluntary isometric contraction (MVIC) torque, electromyographic amplitude (EMG AMP), EMG mean power frequency (MPF), and cognition. Materials and Methods: Twelve recreationally trained women (mean age ± standard deviation = 21 ± 1.6 years) performed 75 submaximal (1 × 30, 3 × 15) unilateral leg extension muscle actions under normoxia, local ischemic hypoxia, and systemic hypoxemia. Before and immediately after the 75 repetitions, MVIC muscle actions were performed, and surface EMG was simultaneously assessed from the vastus lateralis. Cognitive function was assessed immediately after each exercise using the Automated Neuropsychological Assessment Metrics (ANAM). Separate repeated-measures analyses of variance (ANOVAs) were performed to examine changes in MVIC, reaction time, EMG AMP, and EMG MPF responses during the MVIC muscle actions. Results: There were no significant (p = 0.21-0.953) Condition × Time interactions for MVIC, EMG AMP, or EMG MPF but a significant (p < 0.001-0.005) main effect for the Time collapsed across Condition for MVIC torque (pretest 238.8 ± 19.5, posttest 212.7 ± 20.1 Nm) and EMG MPF (88.5% ± 1.4% of pretest). There were no significant (p = 0.503) differences in reaction time among Conditions. Conclusions: The findings of the present study suggest that all three conditions elicited comparable acute changes in performance as assessed by MVIC torque that were associated with no changes in muscle activation but decrease in action potential conduction velocity. Therefore, the application of local ischemic hypoxia or systemic hypoxemia during low-load resistance exercise can be used to elicit similar acute physiological responses and not adversely affect cognitive function relative to nonhypoxic conditions.

3.
Curr Res Physiol ; 4: 209-215, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34746840

RESUMO

Purpose: The present study examined acute normobaric hypoxic exposure on the number of repetitions to failure, electromyographic (EMG) repetition duration (Time), EMG root mean square (RMS) and EMG mean power frequency (MPF) during biceps brachii (BB) dynamic constant external resistance (DCER) exercise. Methods: Thirteen subjects performed two sets of fatiguing DCER arm curl repetitions to failure at 70% of their one repetition maximum under normoxic (NH), moderate hypoxia FiO2 = 15% (MH) and severe hypoxia FiO2 = 13% (SH). Electromyography of the BB was analyzed for EMG Time, EMG RMS, and EMG MPF. Repetitions were selected as 25%, 50%, 75%, and 100% of total repetitions (%Fail) completed. Pulse oximetry (SpO2) was measured pre-and post-fatigue. Results: There was no significant three-way (Condition x Set x %Fail) or two-way (Condition x Set) interaction for any variable. The number of repetitions to failure significantly decreased from (mean ± SEM) 18.2 ± 1.4 to 9.5 ± 1.0 with each Set. In addition, EMG Time increased (25% < 50%<75% < 100%), EMG RMS decreased (50% > 75%>100%), and EMG MPF decreased (75% > 100%) as a result of fatiguing exercise. SpO2 was lower during MH (Δ5.3%) and SH (Δ9.2%) compared to NH and as a result of fatiguing exercise increased only in MH (Δ2.1%) and SH (Δ5.7%). Conclusion: The changes in BB EMG variables indicated exercise caused myoelectric manifestations of fatigue, however, acute moderate or severe hypoxia had no additional influence on the rate of fatigue development or neuromuscular parameters.

4.
Eur J Appl Physiol ; 121(12): 3313-3321, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34432149

RESUMO

PURPOSE: Literature is conflicted on whether electromechanical delay durations decrease following resistance training programs. Therefore, the aim of this study is to examine the contributions and durations of the electrochemical (EMDE-M) and mechanical (EMDM-F) components to the overall electromechanical delay (EMDE-F) during step isometric muscle actions following 4-weeks of structured, multi-joint, lower-body variable resistance training (VRT) program. METHODS: Twelve men performed 4-weeks of VRT leg press training utilizing combination of steel plates (80% total load) and elastic bands (20% total load). Training consisted of 3 sets of 10 repetitions at a 10 repetition maximum load, 3 day week-1 for 4-weeks. EMDE-M, EMDM-F, and EMDE-F was measured at Baseline, Week-2, and Week-4 during voluntary step isometric muscle actions (20, 40, 60, 80, and 100% of maximal voluntary isometric contraction) from the vastus lateralis using electromyographic, mechanomyographic, and force signals. RESULTS: The EMDE-M, EMDM-F, and EMDE-F exhibited decreases in duration following 4-weeks of VRT. In addition, EMDE-M contributed significantly less (42-47%) than EMDM-F (53-58%) to the total duration of EMDE-F across the 4-weeks of VRT. CONCLUSIONS: These findings indicated that a structured, VRT program utilizing multi-joint exercise was sufficient to induce decreases in the electrochemical and mechanical processes associated with step isometric muscle contractions. In addition, the utilization of the electromyographic, mechanomyographic, and force signals were capable of quantifying electrochemical and mechanical component changes associated with voluntary muscle contraction. Thus, EMDE-M, EMDM-F, and EMDE-F can be useful in quantifying physiological changes in athletic, clinical, and applied research interventions.

5.
Clin Physiol Funct Imaging ; 41(5): 452-460, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34192417

RESUMO

The purpose of the present study was to examine the acute changes in muscle swelling (as assessed by muscle thickness and echo intensity) and muscle blood flow associated with an acute bout of low-load blood flow restriction (LLBFR) and low-load non-blood flow restriction (LL) exercise. Twenty women (mean ± SD; 22 ± 2years) volunteered to perform an acute exercise bout that consisted of 75 (1 × 30, 3 × 15) isokinetic, reciprocal, concentric-only, submaximal (30% of peak torque), forearm flexion and extension muscle actions. Pretest, immediately after (posttest), and 5-min after (recovery) completing the 75 repetitions, muscle thickness and echo intensity were assessed from the biceps brachii and triceps brachii muscles and muscle blood flow was assessed from the brachial artery. There were no between group differences for any of the dependent variables, but there were significant simple and main effects for muscle and time. Biceps and triceps brachii muscle thickness increased from pretest (2.13 ± 0.39 cm and 1.88 ± 0.40 cm, respectively) to posttest (2.58 ± 0.49 cm and 2.17 ± 0.43 cm, respectively) for both muscles and remained elevated for the biceps brachii (2.53 ± 0.43 cm), but partially returned to pretest levels for the triceps brachii (2.06 ± 0.41 cm). Echo intensity and muscle blood flow increased from pretest (98.0 ± 13.6 Au and 94.5 ± 31.6 ml min-1 , respectively) to posttest (109.2 ± 16.9 Au and 312.2 ± 106.5 ml min-1 , respectively) and pretest to recovery (110.1 ± 18.3 Au and 206.7 ± 92.9 ml min-1 , respectively) and remained elevated for echo intensity, but partially returned to pretest levels for muscle blood flow. The findings of the present study indicated that LLBFR and LL elicited comparable acute responses as a result of reciprocal, concentric-only, forearm flexion and extension muscle actions.


Assuntos
Braço , Músculo Esquelético , Edema , Exercício Físico , Feminino , Humanos , Músculo Esquelético/diagnóstico por imagem , Torque
6.
Int J Paleopathol ; 33: 209-219, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33984628

RESUMO

OBJECTIVE: The current study evaluates the feasibility of using clinical cranial computed tomography (CT) scans for assessing the presence and morphology of porous cranial lesions (cribra orbitalia, porotic hyperostosis). METHODS: Observers (n = 4) conducted three independent evaluations of porous cranial lesions based on photographs, 2-D CT, and 3-D CT scans of archaeological crania. Evaluations of the crania from each viewing scenario were compared to findings from direct macroscopic observation. MATERIALS: Twenty-two complete adult crania from the Peruvian sites of Pachacamac and Chicama. RESULTS: We found that lesion visibility differed by location: vault lesions with porosity larger than the resolution of the CT scan were identifiable across all viewing scenarios, but orbital lesions were identifiable only when extensive porosity was accompanied by widening of the inter-trabecular spaces. Lesions in stages of advanced remodeling were not visible on CT. CONCLUSIONS: Paleopathological criteria applied to head CTs from clinical cases of suspected cranial fracture can reliably identify moderate to severe porous cranial lesions in living individuals. SIGNIFICANCE: This validation study opens the door to broader study of porous cranial lesions in living individuals that can address open questions about the causes and consequences of these commonly reported skeletal indicators of stress. LIMITATIONS: Performance of all viewing scenarios was evaluated relative to assessment data from direct observation of skeletal remains, but direct observation is itself subject to error. SUGGESTIONS FOR FURTHER RESEARCH: The increasing resolution of routine CTs makes it increasingly possible to explore skeletal lesions in clinical contexts.


Assuntos
Hiperostose , Órbita , Humanos , Porosidade , Crânio/diagnóstico por imagem , Tomografia Computadorizada por Raios X
7.
Eur J Appl Physiol ; 121(5): 1473-1485, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33638690

RESUMO

PURPOSE: The purpose of this investigation was to examine the individual and composite patterns of responses and time-course of changes in muscle size, strength, and edema throughout a 4 week low-load blood flow restriction (LLBFR) resistance training intervention. METHODS: Twenty recreationally active women (mean ± SD; 23 ± 3 years) participated in this investigation and were randomly assigned to 4 weeks (3/week) of LLBFR (n = 10) or control (n = 10) group. Resistance training consisted of 75 reciprocal isokinetic forearm flexion-extension muscle actions performed at 30% of peak torque. Strength and ultrasound-based assessments were determined at each training session. RESULTS: There were quadratic increases for composite muscle thickness (R2 = 0.998), concentric peak torque (R2 = 0.962), and maximal voluntary isometric contraction (MVIC) torque (R2 = 0.980) data for the LLBFR group. For muscle thickness, seven of ten subjects exceeded the minimal difference (MD) of 0.16 cm during the very early phase (laboratory visits 1-7) of the intervention compared to three of ten subjects that exceeded MD for either concentric peak torque (3.7 Nm) or MVIC (2.2 Nm) during this same time period. There was a linear increase for composite echo intensity (r2 = 0.563) as a result of LLBFR resistance training, but eight of ten subjects never exceeded the MD of 14.2 Au. CONCLUSIONS: These findings suggested that the increases in muscle thickness for the LLBFR group were not associated with edema and changes in echo intensity should be examined on a subject-by-subject basis. Furthermore, LLBFR forearm flexion-extension resistance training elicited real increases in muscle size during the very early phase of training that occurred prior to real increases in muscle strength.


Assuntos
Braço/irrigação sanguínea , Braço/fisiologia , Força Muscular/fisiologia , Músculo Esquelético/irrigação sanguínea , Músculo Esquelético/fisiologia , Treinamento de Força/métodos , Braço/anatomia & histologia , Edema/fisiopatologia , Feminino , Humanos , Contração Isométrica/fisiologia , Músculo Esquelético/anatomia & histologia , Torque , Adulto Jovem
8.
J Strength Cond Res ; 35(1): 33-40, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33332803

RESUMO

ABSTRACT: Hill, EC, Housh, TJ, Smith, CM, Keller, JL, Schmidt, RJ, and Johnson, GO. High- vs. low-intensity fatiguing eccentric exercise on muscle thickness, strength, and blood flow. J Strength Cond Res 35(1): 33-40, 2021-The purpose of this investigation was to examine the acute effects of equal volumes of fatiguing high- vs. low-intensity eccentric muscle actions on changes in muscle thickness, echo intensity, muscle blood flow, and adipose thickness. Eighteen men (mean ± SD = 23.2 ± 3.0 years) performed eccentric peak torque (PT) and maximal voluntary isometric contraction (MVIC) trials before (pretest), immediately after (posttest), and 5 minutes after (recovery) performing randomly ordered fatiguing eccentric, isokinetic (180°·s-1) muscle actions of the elbow flexors at 40% (72 repetitions) or 80% (36 repetitions) of eccentric PT. Muscle thickness, exercise-induced edema, muscle blood flow, and adipose thickness were also assessed via ultrasound at pretest, posttest, and recovery. There were no intensity-specific effects on the patterns of responses for eccentric PT, MVIC, muscle thickness, echo intensity, muscle blood flow, or adipose thickness. There were, however, effects across time that decreased from pretest to posttest and from pretest to recovery for eccentric PT (21.5 and 13.0%), MVIC (14.6 and 5.8%), and adipose thickness (10.0 and 6.0%), but increased for muscle thickness (7.6 and 5.9%), echo intensity (13.7 and 9.9%), and muscle blood flow (129.6 and 90.1%) (collapsed across 40 and 80%). These findings indicated that when matched for exercise volume, there were no intensity-related effects on the increases in muscle thickness, echo intensity, muscle blood flow, or the decreases in eccentric PT, MVIC, and adipose thickness after fatiguing eccentric muscle actions. Therefore, exercise volume, independent of exercise intensity and number of repetitions, may be a mediating factor of muscle fatigue and performance during eccentric muscle actions.


Assuntos
Fadiga Muscular , Músculo Esquelético , Exercício Físico , Humanos , Contração Isométrica , Masculino , Contração Muscular , Força Muscular , Músculo Esquelético/diagnóstico por imagem , Torque
9.
J Sport Health Sci ; 9(6): 628-633, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33308813

RESUMO

PURPOSE: The purposes of the present study were: (1) to determine whether the physical working capacity at the fatigue threshold (PWCFT) model that has been used for estimating the onset of neuromuscular fatigue in the vastus lateralis (VL) during incremental treadmill running could also be applied to the vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) muscles; and (2) if applicable, to compare the running velocities associated with the PWCFT among these muscles. METHODS: Eleven subjects (age 21.7 ± 1.8 years) performed an incremental treadmill test to exhaustion with electromyographic signals recorded from the VL, VM, BF, and ST. RESULTS: The results indicated there were no significant (p > 0.05) mean differences in the running velocities associated with the PWCFT for the VL (14.4 ± 2.0 km/h), VM (14.3 ± 1.9 km/h), BF (13.8 ± 1.8 km/h), and ST (14.7 ± 2.3 km/h). In addition, there were significant inter-correlations (r = 0.68-0.88) among running velocities associated with the PWCFT of each muscle. Individual results also indicated that 9 of the 11 subjects exhibited identical PWCFT values for at least 3 of the 4 muscles, but there were no uniform patterns for any intra-individual differences. CONCLUSION: The findings of the present study suggested that the PWCFT test is a viable method to identify neuromuscular fatigue in the quadriceps and hamstrings during incremental treadmill exercise and results in consistent PWCFT values among these muscles.


Assuntos
Teste de Esforço/métodos , Músculos Isquiossurais/fisiologia , Fadiga Muscular , Músculo Quadríceps/fisiologia , Eletromiografia , Feminino , Humanos , Masculino , Troca Gasosa Pulmonar , Corrida/fisiologia , Adulto Jovem
10.
Am J Phys Anthropol ; 173(4): 721-733, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32869279

RESUMO

OBJECTIVES: Cribra orbitalia (CO) and porotic hyperostosis (PH) are porous cranial lesions (PCLs) classically associated with iron-deficiency anemia in bioarchaeological contexts. However, recent studies indicate a need to reassess the interpretation of PCLs. This study addresses the potential health correlates of PCLs in a contemporary sample by examining relationships between the known cause of death (COD) and PCL presence/absence. METHODS: This study includes a sample of 461 juvenile individuals (6 months to 15 years of age) who underwent examination at the University of New Mexico's Office of the Medical Investigator between 2011 and 2019. The information available for each individual includes their sex, age at death, and their COD and manner of death. RESULTS: Odds ratio of having CO (OR = 3.92, p < .01) or PH (OR = 2.86, p = .02) lesions are increased in individuals with respiratory infections. Individuals with heart conditions have increased odds of having CO (OR = 3.52, p = .03) lesions, but not PH. CONCLUSION: Individuals with respiratory infection are more likely to have CO and/or PH. CO appears to have a greater range of health correlates than PH does, as indicated by the heart condition results. However, individuals with congenital heart defects are at higher risk for respiratory infections, so bony alterations in cases of heart conditions may be due to respiratory illness. Since respiratory infection remains a leading cause of mortality today, CO and PH in bioarchaeological contexts should be considered as potential indicators of respiratory infections in the past.


Assuntos
Hiperostose , Órbita/patologia , Infecções Respiratórias , Adolescente , Causas de Morte , Criança , Pré-Escolar , Feminino , Humanos , Hiperostose/complicações , Hiperostose/diagnóstico por imagem , Hiperostose/epidemiologia , Hiperostose/patologia , Lactente , Masculino , New Mexico , Órbita/diagnóstico por imagem , Paleopatologia , Infecções Respiratórias/complicações , Infecções Respiratórias/epidemiologia , Estresse Fisiológico , Tomografia Computadorizada por Raios X
11.
J Musculoskelet Neuronal Interact ; 20(3): 325-331, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32877969

RESUMO

OBJECTIVES: This study examined performance fatigability and the patterns of neuromuscular responses for electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) during bilateral (BL) and unilateral (UL) maximal, isokinetic leg extensions. METHODS: Peak torque for each repetition and EMG and MMG signals from the non-dominant vastus lateralis were recorded in 11 men during 50 BL and UL maximal, concentric, isokinetic leg extensions at 60o·s-1 that were performed on separate days. Separate repeated measures ANOVAs were performed to examine the normalized isokinetic torque and neuromuscular parameters. RESULTS: Normalized isokinetic peak torque demonstrated a significant Conditions by Repetition interaction (p<0.001, η2p= 0.594). There were no interactions, but significant main effects for Repetition with increases in EMG AMP (p<0.001; η2p=0.255) and decreases in EMG MPF (p<0.001; η2p=0.650), MMG AMP (p<0.001; η2p=0.402), and MMG MPF (p<0.001; η2p=0.796). In addition, EMG MPF and MMG AMP demonstrated main effects for Condition (p=0.031; η2p=0.387 and p=0.002; η2p=0.64, respectively) with the BL exhibiting greater values than UL leg extensions for both parameters. CONCLUSIONS: The current findings indicated greater performance fatigability during UL versus BL leg extensions, but similar patterns of neuromuscular responses consistent with the Muscle Wisdom Hypothesis.


Assuntos
Fadiga Muscular/fisiologia , Força Muscular/fisiologia , Eletrofisiologia/métodos , Humanos , Perna (Membro) , Masculino , Adulto Jovem
12.
J Hum Evol ; 146: 102855, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32781348

RESUMO

In 2010, a hominin right humerus fragment (KNM-RU 58330) was surface collected in a small gully at Nyamita North in the Late Pleistocene Wasiriya Beds of Rusinga Island, Kenya. A combination of stratigraphic and geochronological evidence suggests the specimen is likely between ∼49 and 36 ka in age. The associated fauna is diverse and dominated by semiarid grassland taxa. The small sample of associated Middle Stone Age artifacts includes Levallois flakes, cores, and retouched points. The 139 mm humeral fragment preserves the shaft from distal to the lesser tubercle to 14 mm below the distal end of the weakly projecting deltoid tuberosity. Key morphological features include a narrow and weakly marked pectoralis major insertion and a distinctive medial bend in the diaphysis at the deltoid insertion. This bend is unusual among recent human humeri but occurs in a few Late Pleistocene humeri. The dimensions of the distal end of the fragment predict a length of 317.9 ± 16.4 mm based on recent samples of African ancestry. A novel method of predicting humeral length from the distance between the middle of the pectoralis major and the bottom of the deltoid insertion predicts a length of 317.3 mm ± 17.6 mm. Cross-sectional geometry at the midshaft shows a relatively high percentage of cortical bone and a moderate degree of flattening of the shaft. The Nyamita humerus is anatomically modern in its morphology and adds to the small sample of hominins from the Late Pleistocene associated with Middle Stone Age artifacts known from East Africa. It may sample a population closely related to the people of the out-of-Africa migration.


Assuntos
Fósseis/anatomia & histologia , Úmero/anatomia & histologia , Humanos , Quênia , Paleontologia
13.
Sci Adv ; 6(23): eaba3245, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32537504

RESUMO

Maize is a cultigen of global economic importance, but when it first became a staple grain in the Americas, was unknown and contested. Here, we report direct isotopic dietary evidence from 52 radiocarbon-dated human skeletons from two remarkably well-preserved rock-shelter contexts in the Maya Mountains of Belize spanning the past 10,000 years. Individuals dating before ~4700 calendar years before present (cal B.P.) show no clear evidence for the consumption of maize. Evidence for substantial maize consumption (~30% of total diet) appears in some individuals between 4700 and 4000 cal B.P. Isotopic evidence after 4000 cal B.P. indicates that maize became a persistently used staple grain comparable in dietary significance to later maize agriculturalists in the region (>70% of total diet). These data provide the earliest definitive evidence for maize as a staple grain in the Americas.

14.
Phys Ther Sport ; 43: 1-7, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32035361

RESUMO

OBJECTIVES: Little is known regarding the variables or mechanisms mediating cross-education as a result of resistance training. Therefore, the purpose of the present study was to examine the effects of low-load eccentric-only blood flow restriction (Ecc-BFR) and low-load concentric-only BFR (Con-BFR) on indices of cross-education. DESIGN: Thirty-six women were randomly assigned to 4-wks of unilateral resistance training with Ecc-BFR (n = 12), Con-BFR (n = 12) or control (no intervention, n = 12) group. Eccentric peak torque, concentric peak torque, maximal voluntary isometric contraction torque, muscle thickness, and muscle activation were assessed from the contralateral, untrained arm. RESULTS: Muscle strength (collapsed across mode) increased from 0-wk to 2-wks (4.9%) and 4-wks (13.0%) for Ecc-BFR only. There were increases in muscle activation (collapsed across mode and group) regardless of training modality, but there were no changes in muscle size for any of the conditions. CONCLUSIONS: The findings of the present study indicated that low-load Ecc-BFR increased muscle strength. The increases in muscle strength as a result of Ecc-BFR were not mode-specific. Thus, low-load Ecc-BFR provides a unique alternative to maintain muscle function in an untrained limb that may have application during limb immobilization and rehabilitation practices.


Assuntos
Força Muscular , Fluxo Sanguíneo Regional , Treinamento de Força/métodos , Extremidade Superior/irrigação sanguínea , Artéria Braquial/diagnóstico por imagem , Feminino , Humanos , Contração Isométrica , Músculo Esquelético/diagnóstico por imagem , Torque , Ultrassonografia , Extremidade Superior/diagnóstico por imagem , Adulto Jovem
15.
Am J Phys Anthropol ; 172(4): 682-697, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32057097

RESUMO

OBJECTIVES: This study examines long bone diaphyseal rigidity and shape of hunter-gatherers at Roonka to make inferences about subsistence strategies and mobility of inhabitants of semi-arid southeastern Australia. Roonka is a cemetery site adjacent to the Lower Murray River, which contains over 200 individuals buried throughout the Holocene. Archaeological evidence indicates that populations living near this river corridor employed mobile, risk averse foraging strategies. METHODS: This prediction of lifestyle was tested by comparing the cross-sectional geometric properties of the humerus, radius, ulna, femur, tibia, and fibula of individuals from Roonka to samples of varying subsistence strategies. Bilateral asymmetry of the upper limb bones was also examined. RESULTS: Roonka males and females have moderately high lower limb diaphyseal rigidity and shape. In the upper limb, females have low rigidity and bilateral asymmetry while males have moderately high rigidity and bilateral asymmetry. This pattern is similar to other foraging groups from Australia and southern Africa that have behaviorally adapted to arid and semi-arid environments. DISCUSSION: Lower limb results suggest that populations in the Lower Murray River Valley had relatively elevated foraging mobility. Upper limb rigidity and bilateral asymmetry indicate a sexual division of labor at Roonka. Females resemble other samples that had mixed subsistence strategies that involved hunting, gathering, and processing tasks. Males display a pattern similar to groups that preferentially hunted large game, but that supplemented this source with smaller game and riverine resources.


Assuntos
Osso e Ossos/anatomia & histologia , Diáfises/anatomia & histologia , /estatística & dados numéricos , Anatomia Transversal , Antropologia Física , Comportamento Apetitivo , Fenômenos Biomecânicos/fisiologia , Feminino , História Antiga , Humanos , Masculino , Austrália do Sul
16.
J Electromyogr Kinesiol ; 50: 102367, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31711012

RESUMO

The purpose of this study was to compare isokinetic peak torque and the patterns of responses for electromyographic (EMG) and mechanomyographic (MMG), amplitude (AMP) and mean power frequency (MPF) for bilateral (BL) versus unilateral (UL), maximal, isokinetic leg extensions. Eleven recreationally trained women (Mean ±â€¯SD: age 22.9 ±â€¯0.9 yrs; body mass 60.5 ±â€¯10.1 kg; height 167.2 ±â€¯6.4 cm) performed 50 maximal, BL and UL isokinetic leg extensions at 60°â€¯s-1 on separate days. Electromyographic and MMG signals from the vastus lateralis of the nondominant leg were recorded. Five separate 2 (Condition [BL and UL]) × 10 (Repetitions [5-50]) repeated measures ANOVAs were performed to examine normalized EMG AMP, EMG MPF, MMG AMP, MMG MPF, and isokinetic torque. The results indicated no significant interactions or main effects for EMG AMP and MMG AMP. There were significant interactions for normalized isokinetic peak torque (p < 0.001, η2p = 0.493) and MMG MPF (p = 0.003, η2p = 0.234). For EMG MPF, there was no significant interaction, but significant main effects for Condition (p = 0.003, η2p = 0.607) and Repetitions (p < 0.001, η2p = 0.805). The current findings demonstrated greater performance fatigability for UL than BL leg extensions. Both modalities exhibited similar patterns of neuromuscular responses that were consistent with the Muscular Wisdom hypothesis.


Assuntos
Perna (Membro)/fisiologia , Fadiga Muscular , Músculo Esquelético/fisiologia , Adulto , Testes Diagnósticos de Rotina , Feminino , Lateralidade Funcional , Humanos , Contração Muscular , Torque
17.
Eur J Appl Physiol ; 120(2): 425-441, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31848703

RESUMO

PURPOSE: Low-load venous blood flow restriction resistance training (RT + BFR) has been demonstrated to increase muscle strength to a greater degree than low-load non-BFR resistance training (RT) during isotonic training, but no previous investigations have examined RT + BFR versus RT during isokinetic training. The purpose of the present study was to examine the effects of 4 weeks of isokinetic low-load RT + BFR versus low-load RT on indices of muscle strength, muscle size, and neural adaptations. METHODS: Thirty women (mean ± SD; 22 ± 2 years) participated in this investigation and were randomly assigned to 4 weeks of either RT + BFR (n = 10), RT (n = 10), or control (n = 10) group. Resistance training consisted of 75 reciprocal forearm flexion-extension isokinetic muscle actions of the forearm flexors performed at a velocity of 120°s-1. RESULTS: Concentric peak torque increased to a greater extent for RT + BFR after 4 weeks (36.9%) compared to RT (25.8%), but there were similar increases in isometric torque (23.3-42.1%). For both RT + BFR and RT, there were similar increases in muscle cross-sectional area and muscle thickness of the biceps brachii after 2 weeks (11.3-14.3% and 12.4-12.9%, respectively) and 4 weeks (18.7-21.9% and 19.0-20.0%, respectively). There were similar increases in mechanomyographic amplitude, mechanomyographic mean power frequency, and electromyographic mean power frequency, but no changes in electromyographic amplitude for all conditions (including control). CONCLUSIONS: These findings indicated that low-load RT + BFR elicited greater increases in concentric strength than low-load RT, but elicited comparable increases in isometric strength and muscle size. There were also no differences in any of the EMG and MMG responses among conditions.


Assuntos
Velocidade do Fluxo Sanguíneo , Contração Isométrica/fisiologia , Músculo Esquelético/irrigação sanguínea , Músculo Esquelético/crescimento & desenvolvimento , Treinamento de Força/métodos , Feminino , Humanos , Adulto Jovem
18.
J Funct Morphol Kinesiol ; 5(1)2020 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-33467220

RESUMO

Previous studies have demonstrated that ayurvedic ingredients exhibit ergogenic (performance enhancing) properties, however, no previous studies have examined the ergogenic potential of Asparagus racemosus. The purpose of the present study was to examine the ergogenic efficacy of supplementation with 500 mg·d-1 of A. racemosus during bench press training. Eighteen recreationally trained men (mean ± SD; age = 20.4 ± 0.5 yrs; height = 179.7 ± 1.5 cm; weight = 84.7 ± 5.7 kg) were randomly assigned either 500 mg·d-1 of A. racemosus (n = 10) or placebo (n = 8). An overlapping sample of 10 participants were used to determine test-retest reliability. Pre- and post-training testing included bench press with one repetition maximum (1RM) and repetitions to failure at 70% of pre-training 1RM. The participants performed two sets of bench press to failure three times a week for eight weeks. Independent t-tests, Analyses of covariance (ANCOVA), and regression analyses were used to analyze the dependent variables. The results demonstrated greater mean percentage (14.3 ± 7.7% vs. 7.8 ± 4.5%; p = 0.048) and individual (80% vs. 50%) increases in 1RM, mean (17.5 ± 2.2 repetitions vs. 15.2 ± 2.2 repetitions; p = 0.044) and individual (80% vs. 38%) increases in repetitions to failure, and a greater rate of increase in training loads for the Asparagus racemosus group than the placebo group. In conjunction with bench press training, supplementation with A. racemosus provided ergogenic benefits compared to placebo.

19.
J Strength Cond Res ; 2019 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-31860532

RESUMO

Keller, JL, Housh, TJ, Hill, EC, Smith, CM, Schmidt, RJ, and Johnson, GO. Are there sex-specific neuromuscular or force responses to fatiguing isometric muscle actions anchored to a high perceptual intensity? J Strength Cond Res XX(X): 000-000, 2019-The purpose of this study was to use the ratings of perceived exertion (RPE) clamp model to examine sex-specific changes in neuromuscular responses and force after a sustained isometric leg extension muscle action anchored to RPE = 8. Twenty adults (10 men and 10 women) performed sustained, isometric leg extension muscle actions at RPE = 8. Electromyographic (EMG) and mechanomyographic signals were recorded from the dominant leg. Neuromuscular and force values resulting from the sustained muscle action were normalized to pretest maximal voluntary isometric contractions (MVICs). The level of significance set for the study was p ≤ 0.05. The pretest MVIC was significantly (p < 0.001) greater (averaged across sex) than posttest MVIC force (55.5 ± 10.0 vs. 47.6 ± 11.1 kg). There was a significant (p < 0.01) decrease from pretest (95.4 ± 7.7 Hz) to posttest (76.2 ± 5.9 Hz) in EMG mean power frequency (MPF) for the men. The normalized force (averaged across sex) decreased significantly (p < 0.001) from the initial timepoint (57.1 ± 16.4%) to the final timepoint (44.3 ± 15.7%) of the sustained muscle action. Normalized EMG MPF (averaged across sex) decreased significantly (p = 0.001) from the initial timepoint (96.4 ± 17.5%) to final timepoint (87.8 ± 18.1%). The men and women exhibited similar fatigue-induced changes in force and neuromuscular parameters; therefore, these findings did not indicate different sex-specific responses after the fatiguing task anchored to a high perception of exertion. The force corresponding to RPE = 8 did not match the anticipated value; so, RPE and percentages of MVIC cannot be used interchangeably, and sustained isometric muscle actions anchored to RPE may elicit unique neuromuscular adaptations.

20.
Eur J Appl Physiol ; 119(10): 2363-2373, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31473805

RESUMO

PURPOSE: Unaccustomed exercise can result in delayed onset muscle soreness (DOMS), particularly as a result of the eccentric phase of the muscle contraction. Resistance training combined with venous blood flow restriction (vBFR) may attenuate DOMS, but the available information in this regard is conflicting. Therefore, the purpose of this study was to examine the effects of low-load eccentric vBFR (Ecc-vBFR) and concentric vBFR (Con-vBFR) resistance training on indices of DOMS. METHODS: Twenty-five previously untrained women completed seven days of either Ecc-vBFR (n = 12) or Con-vBFR (n = 13) forearm flexion resistance training at a velocity of 120° s-1 on an isokinetic dynamometer. The Ecc-vBFR group used a training load that corresponded to 30% of eccentric peak torque and the Con-vBFR group used a training load that corresponded to 30% of concentric peak torque. RESULTS: There were no differences between Ecc-vBFR and Con-vBFR at any of the seven training sessions on any of the indices of DOMS. There were no decreases in the maximal voluntary isometric contraction torque which increased at days 6 and 7. Similarly, there were no changes in perceived muscle soreness, pain pressure threshold, elbow joint angle, or edema (as assessed by echo intensity via ultrasound) across the seven training sessions. CONCLUSIONS: The Ecc-vBFR and Con-vBFR low-load training protocols were not associated with DOMS and there were no differences between protocols when performed using the same relative training intensity. These findings suggested that both unaccustomed eccentric and concentric low-load training did not result in DOMS when combined with vBFR.


Assuntos
Precondicionamento Isquêmico/métodos , Músculo Esquelético/fisiologia , Mialgia/prevenção & controle , Treinamento de Força/métodos , Feminino , Humanos , Precondicionamento Isquêmico/efeitos adversos , Contração Muscular , Músculo Esquelético/irrigação sanguínea , Mialgia/etiologia , Tempo de Reação , Treinamento de Força/efeitos adversos , Adulto Jovem
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