Propulsive forces and muscle activation during gait: comparisons between premenopausal and postmenopausal midlife women.

OBJECTIVE: The aim of this study was to investigate whether there is a reduction in propulsive force during gait in postmenopausal women compared with premenopausal women. METHODS: Forty-four women (21 premenopausal and 23 postmenopausal women) aged 40 to 55 years were selected. The ability to reach peak propulsive forces was assessed during the step execution test. The test was performed at the usual speed on 2 nonconsecutive days, with two attempts per day, using a force platform. Four temporal parameters were defined and calculated: initiation phase, preparation phase, swing phase, and total time. Peak force (anteroposterior and vertical) and time to reach peak force were obtained in both preparation and swing phases. The rate of force development was defined as peak force divided by time to reach peak force. RESULTS: The postmenopausal women group presented a longer time in the preparation phase (540.6 ± 77 ms vs 482.5 ± 93 ms, P = 0.024) and consequently a longer total time in the step execution test (1,191 ± 106.4 ms vs 1,129 ± 114.3 ms, P = 0.045). There were differences between the groups for the rate of force development in the anteroposterior (postmenopausal women, 142.5 ± 38.1 N/s vs premenopausal women, 174.7 ± 70.5 N/s; P = 0.022) and vertical directions in the preparation phase (postmenopausal women, 102.7 ± 62.3 N/s vs premenopausal women, 145.3 ± 71 N/s; P = 0.012). No significant differences ( P > 0.05) were found in force, time to peak force, and rate of force development during the swing phase. In addition, there were no observed differences in surface electromyography of the medial and lateral gastrocnemius muscles during the preparation phase and swing phase of the step execution test between the two groups. CONCLUSIONS: Postmenopausal women exhibited lower ability to generate propulsive force rapidly (rates of force development) in both the anteroposterior and vertical directions during the preparation phase of gait compared with premenopausal women. This indicates that postmenopausal women experience a reduction in propulsive force during gait.

Effect of Fatigue and Graded Running on Kinematics and Kinetics Parameters in Triathletes.

This study aimed to evaluate the effect of cycling-induced fatigue on subsequent running with different ground inclinations on triathletes. Twenty male triathletes ran on a treadmill at individual speeds, on three inclines: level (0%), 7% uphill (7%), and 7% downhill (-7%). Subsequently, the athletes performed an incremental ramp-to-exhaustion (RTE) protocol on an ergometric bicycle until task failure and repeated the running protocol (POST-RTE). During running and cycling was monitored perceived exertion (RPE) and heart rate (HR). Plantar pressure distribution, peak plantar pressure, total foot area, and ground contact time were measured by an in-shoe sensor. Analysis of variance showed that HR (p=0.001; η2=0.63) and RPE (p=0.001; η2=0.82 large effect) were higher in POST-RTE, without interactions between slopes and fatigue. The heel load showed difference between 0 and 7% and 7 and -7% (p=0.001; η 2=0.44 large effect) with higher value in -7%. The midfoot showed differences between 0 and -7% with higher value in 0% (p=0.03; η 2=0.15 small effect). The contact time showed interactions between fatigue and slopes with a higher value in POST-RTE. Coaches should be aware that training on the uphill and downhill surfaces can alter the plantar load on different foot parts.

Lateral and functional asymmetries in the lower limbs of college-level female handball players

Abstract Aim: The present study aimed to screen for differences in isokinetic peak torque, hamstrings-to-quadriceps ratio, and proprioception within the lower limbs of female handball athletes. Methods: Twelve college-level female handball athletes with no previous experience with resistance training performed five maximal isokinetic contractions of the knee extensors and knee flexors to determine isokinetic peak torque and hamstring-to-quadriceps ratios. Proprioception was determined by assessing passive position sense on an isokinetic dynamometer. Results: The athletes presented significantly greater (p < 0.01) knee extensors isometric peak torque for the jumping limb (144.9 ± 23.1) when compared to the non-jumping limb (132.9 ± 21.5). The Hamstrings-to-quadriceps ratio was below 0.6 for both limbs, being significantly greater (p < 0.01) for the non-jumping limb (0.56 ± 0.08) when compared to the jumping limb (0.50 ± 0.08). Conclusion: Female handball athletes that do not engage in resistance training can experience functional bilateral asymmetries in the knee extensors and knee-joint instability, as assessed by the hamstrings-to-quadriceps ratio due to the asymmetric characteristics of handball. Regular strength training might correct such asymmetries and instabilities.

Renoprotection Induced by Aerobic Training Is Dependent on Nitric Oxide Bioavailability in Obese Zucker Rats.

Aerobic training (AT) promotes several health benefits that may attenuate the progression of obesity associated diabetes. Since AT is an important nitric oxide (NO-) inducer mediating kidney-healthy phenotype, the present study is aimed at investigating the effects of AT on metabolic parameters, morphological, redox balance, inflammatory profile, and vasoactive peptides in the kidney of obese-diabetic Zucker rats receiving L-NAME (N(omega)-nitro-L-arginine methyl ester). Forty male Zucker rats (6 wk old) were assigned into four groups (n = 10, each): sedentary lean rats (CTL-Lean), sedentary obese rats (CTL-Obese), AT trained obese rats without blocking nitric oxide synthase (NOS) (Obese+AT), and obese-trained with NOS block (Obese+AT+L-NAME). AT groups ran 60 min in the maximal lactate steady state (MLSS), five days/wk/8 wk. Obese+AT rats improved glycemic homeostasis, SBP, aerobic capacity, renal mitochondria integrity, redox balance, inflammatory profile (e.g., TNF-α, CRP, IL-10, IL-4, and IL-17a), and molecules related to renal NO- metabolism (klotho/FGF23 axis, vasoactive peptides, renal histology, and reduced proteinuria). However, none of these positive outcomes were observed in CTL-Obese and Obese+AT+L-NAME (p < 0.0001) groups. Although Obese+AT+L-NAME lowered BP (compared with CTL-Obese; p < 0.0001), renal damage was observed after AT intervention. Furthermore, AT training under conditions of low NO- concentration increased signaling pathways associated with ACE-2/ANG1-7/MASr. We conclude that AT represents an important nonpharmacological intervention to improve kidney function in obese Zucker rats. However, these renal and metabolic benefits promoted by AT are dependent on NO- bioavailability and its underlying regulatory mechanisms.

10 semanas de treinamento de força melhoram quais capacidades físicas em adolescentes fisicamente ativos? / 10 weeks of strength training improve what physical capabilities in physically active adolescents?

o estudo teve como objetivo verificar as adaptações geradas pelo treinamento de força (TF) nos parâmetros neuromusculares e na composição corporal de adolescentes. A amostra foi composta por 10 adolescentes do sexo masculino (16,4 ± 1,0 anos), o protocolo de treinamento de força teve duração de 10 semanas com 3 sessões semanais, divididos em treinos A e B. Para comparação do desempenho, foram avaliadas variáveis antropométricas e composição corporal (estatura, peso, índice de massa corporal e percentual de gordura), bem como, neuromusculares, por meio da resistência muscular de membros superiores (teste de flexão de braços), força explosiva de membros inferiores (teste de salto horizontal), flexibilidade (teste de sentar e alcançar), e força muscular (supino, puxada e leg press 45º). Para comparar os resultados pré e pós intervenção foram utilizadas as diferenças de médias estandardizadas e seus respectivos intervalos de confiança (IC= 90%) e as probabilidades (maior/similar/menor). Foram encontrados aumentos substanciais entre os períodos pré e pós intervenção, para a resistência muscular localizada de membros superiores (92/7/1, Likely), um impacto benéfico de força no supino (86/11/2, Likely), puxada (82/15/3, Likely) e leg press 45° (84/14/2, Likely), e redução em média de 3% na gordura corporal. Os resultados contribuem para uma reflexão crítica em relação ao incentivo a prática de TF em adolescentes, pois com supervisão adequada, planejamento, individualização das cargas de treino e educação técnica correta de cada exercício, os riscos foram suprimidos e os benefícios amplificados.(AU)

Our aim was to investigate the adaptations caused by strength training (ST) in neuromuscular parameters and body composition of adolescents. The sample consisted of 10 male adolescents (16.4 ± 1.0 years) and the strength training protocol lasted 10 weeks with 3 weekly sessions, divided into training sessions A and B. Anthropometric variables and body composition (height, weight, body mass index and percentage of fat) as well as neuromuscular performance (upper limb endurance strength, horizontal jump height, flexibility and muscle strength in bench-press, lat pull-down and 45º leg press exercises). Pre- and post-intervention results were compared using standardized mean differences and their respective confidence intervals (CI = 90%) and likelihood (greater / similar / lower). Substantial increases were found between the pre- and post-intervention periods for upper-limb muscle endurance (92/7/1, Likely) and bench press (86/11/2, Likely), lat pull-down (82 / 15/3, Likely) and leg press (84/14/2, Likely) strength, while a beneficial reduction of 3% in body fat was observed. The results contribute to a critical reflection regarding the incentive to practice ST in adolescents. With proper supervision, planning, individualization of training loads and correct technical education of each exercise, the potential risks were suppressed and the benefits amplified.(AU)

Neuromuscular profile of Handball players during a short-term condensed competition in Brazil / Perfil neuromuscular de atletas de handebol durante curta competição no Brasil

Abstract The aim of this study was to assess the neuromuscular profile of handball (TH) players during a short-term condensed competition. Nine TH athletes (age: 23 ± 3 years; height: 176.2 ± 10.5 cm; mass: 75.3 ± 8.6 kg) played 5 handball matches in 5 consecutive days and had exercise-induced muscle damage (EIMD) markers such as soreness (SOR), thigh circumference (CIR), knee range of motion (ROM) and countermovement jump height (CMJ) collected before the first match and at the end of each day of competition. Changes over time in these markers were analyzed. Significant changes were found for all EIMD markers assessed. CMJ significantly decreased at the fourth day of competition when compared to baseline (0.41 ± 0.03 m vs. 0.45 ± 0.02 m). ROM decreased on the first day of competition and remained stable until the last day of competition (baseline: 126.5 ± 7.2º; 1st day: 115.8 ± 5.9º; 2nd day: 115 ± 7º; 3rd day: 113.9 ± 8.8º; 4th day: 114.4 ± 8.6º). SOR and CIR were increased at the second day of competition and remained altered thereafter. It was concluded that the characteristics of short-term condensed competition have led TH athletes to significant EIMD. If not avoided, EIMD might lead to reductions in performance in the most important (final) matches.

Resumo O objetivo do presente estudo foi medir o perfil neuromuscular de jogadores de handebol durante uma competição em formato de jogos. Nove jogadores de handebol (idade: 23 ± 3 anos; estatura: 176,2 ± 10,5 cm; massa: 75,3 ± 8,6 kg) jogaram cinco partidas da modalidade em cinco dias consecutivos e tiveram marcadores de DM [como percepção subjetiva de dor (PSD), circunferência da coxa (CIR), amplitude de movimento do joelho (ADM) e altura de salto com contra-movimento (AS)] coletados antes da primeira partida e ao final de cada dia de competição. Mudanças ao longo do tempo nesses marcadores foram analisadas. Alterações significantes foram encontradas para todos os marcadores de DM coletados. A AS diminuiu significantemente durante o quarto dia de competição, quando comparado ao valor basal (0,41 ± 0,03 m vs. 0,45 ± 0,02 m). A ADM diminuiu após o primeiro dia de competição e permaneceu comprometida até o último dia (basal: 126,5 ± 7,2º; 1o dia: 115,8 ± 5,9º; 2o dia: 115 ± 7º; 3odia: 113,9 ± 8,8º; 4o dia: 114,4 ± 8,6º). A PSD e a CIR apresentaram aumento durante o segundo dia de competição e permaneceram alteradas até o final da mesma. Concluímos que a característica condensada das competições de handebol no Brasil leva a um quadro de DM significante. Se não evitado, o DM pode levar a comprometimentos no desempenho nas partidas mais importantes da competição (finais).

Influência da fadiga no equilíbrio do pé de apoio de jogadores de futebol / Influence of fatigue on balance of foot support of football players

O objetivo do presente estudo foi investigar a influencia da fadiga no equilíbrio do pé de apoio no momento do chute em jogadores de futebol. Participaram desta pesquisa 19 atletas de futebol divididos em dois grupos: grupo exaustão (GEX) que realizou um esforço com carga incremental até a exaustão em esteira rolante, e o grupo controle (GCE) realizou um esforço leve-constante de forma continua em esteira rolante. Antes e após os protocolos foram avaliados parâmetros de equilíbrio estático em apoio unipodal, utilizando uma plataforma de força. O GEX apresentou aumento da área de deslocamento do centro de pressão (COP) (p < 0,05) após exaustão, tanto para o pé direito como para o esquerdo. A velocidade máxima de deslocamento do centro de pressão ântero-posterior da perna direita do GEX aumentou significantemente (p < 0,05) após a exaustão em relação aos valores de repouso. A fadiga pode diminuir a capacidade de equilíbrio do pé de apoio em jogadores de futebol. Principalmente no apoio com o pé que não é o usual de apoio para o chute.

The aim of this study was to investigate the influence of fatigue on the balance of the support leg kick in soccer players. 19 soccer players were divided randomly into two groups: group exhauston (GEX), underwent an effort with incremental load at exhaustion on a treadmill, and the control group (GCE) underwent effort with constant lower load. Parameters of static balance in single support (one foot) were evaluated before and after the protocols, using a force platform (AMTI OR6-5). The GEX showed enlargement of the displacement of center of pressure (COP) (p < 0.05) after exhaustion, for the right foot. The maximum displacement of the antero posterior center of pressure of the right leg of the GEX incresead significantly (p < 0.05) after exhaustion in relation to resting values. In conclusion, fatigue can impair the ability to keep balance for the support leg in soccer players. Mainly on support to the foot that is not the usual support for the kick.