Quantitative MRI of Vastus Medialis, Vastus Lateralis and Gluteus Medius Muscle Workload after Squat Exercise: Comparison Between Squatting with Hip Adduction and Hip Abduction

The aim of the present study was to evaluate the use MRI to quantify the workload of gluteus medius (GM), vastus medialis (VM) and vastus lateralis (VL) muscles in different types of squat exercises. Fourteen female volunteers were evaluated, average age of 22 +/- 2 years, sedentary, without clinical symptoms, and without history of previous lower limb injuries. Quantitative MRI was used to analyze VM, VL and GM muscles before and after squat exercise, squat associated with isometric hip adduction and squat associated with isometric hip abduction. Multi echo images were acquired to calculate the transversal relaxation times (T2) before and after exercise. Mixed Effects Model statistical analysis was used to compare images before and after the exercise (Delta T2) to normalize the variability between subjects. Imaging post processing was performed in Matlab software. GM muscle was the least active during the squat associated with isometric hip adduction and VM the least active during the squat associated with isometric hip abduction, while VL was the most active during squat associated with isometric hip adduction. Our data suggests that isometric hip adduction during the squat does not increase the workload of VM, but decreases the GM muscle workload. Squat associated with isometric hip abduction does not increase VL workload.

The effect of hip abduction on the EMG activity of vastus medialis obliquus, vastus lateralis longus and vastus lateralis obliquus in healthy subjects

Abstract Study design Controlled laboratory study. Objectives The purposes of this paper were to investigate (d) whether vastus medialis obliquus (VMO), vastus lateralis longus (VLL) and vastus lateralis obliquus (VLO) EMG activity can be influenced by hip abduction performed by healthy subjects. Background Some clinicians contraindicate hip abduction for patellofemoral patients (with) based on the premise that hip abduction could facilitate the VLL muscle activation leading to a VLL and VMO imbalance Methods and measures Twenty-one clinically healthy subjects were involved in the study, 10 women and 11 men (aged X = 23.3 ± 2.9). The EMG signals were collected using a computerized EMG VIKING II, with 8 channels and three pairs of surface electrodes. EMG activity was obtained from MVIC knee extension at 90° of flexion in a seated position and MVIC hip abduction at 0° and 30° with patients in side-lying position with the knee in full extension. The data were normalized in the MVIC knee extension at 50° of flexion in a seated position, and were submitted to ANOVA test with subsequent application of the Bonferroni multiple comparisons analysis test. The level of significance was defined as p ≤ 0.05. Results The VLO muscle demonstrated a similar pattern to the VMO muscle showing higher EMG activity in MVIC knee extension at 90° of flexion compared with MVIC hip abduction at 0° and 30° of abduction for male (p < 0.0007) and MVIC hip abduction at 0° of abduction for female subjects (p < 0.02196). There were no statistically significant differences in the VLL EMG activity among the three sets of exercises tested. Conclusion The results showed that no selective EMG activation was observed when comparison was made between the VMO, VLL and VLO muscles while performing MVIC hip abduction at 0° and 30° of abduction and MVIC knee extension at 90° of flexion in both male and female subjects. Our findings demonstrate that hip abduction do not facilitated VLL and VLO activity in relation to the VMO, however, this study included only healthy subjects performing maximum voluntary isometric contraction contractions, therefore much remains to be discovered by future research

Effects of strength and power training on neuromuscular variables in older adults

The purpose of this study was to compare the neuromuscular adaptations produced by strength-training (ST) and power-training (PT) regimens in older individuals. Participants were balanced by quadriceps cross-sectional area (CSA) and leg-press 1-repetition maximum and randomly assigned to an ST group (n = 14; 63.6 +/- 4.0 yr, 79.7 +/- 17.2 kg, and 163.9 +/- 9.8 cm), a PT group (n = 16; 64.9 +/- 3.9 yr. 63.9 +/- 11.9 kg, and 157.4 +/- 7.7 cm), or a control group (n = 13; 63.0 +/- 4.0 yr, 67.2 +/- 10.8 kg, and 159.8 +/- 6.8 cm). ST and PT were equally effective in increasing (a) maximum dynamic and isometric strength (p < .05), (b) increasing quadriceps muscle CSA (p < .05), and (c) decreasing electrical mechanical delay of the vastus lateralis muscle (p < .05). There were no significant changes in neuromuscular activation after training. The novel finding of the current study is that PT seems to be an attractive alternative to regular ST to maintain and improve muscle mass.

Phylogenetic relationships of rock-wallabies, Petrogale (Marsupialia: Macropodidae) and their biogeographic history within Australia

The rock-wallaby genus Petrogale comprises a group of habitat-specialist macropodids endemic to Australia. Their restriction to rocky outcrops, with infrequent interpopulation dispersal, has been suggested as the cause of their recent and rapid diversification. Molecular phylogenetic relationships within and among species of Petrogale were analysed using mitochondrial (cytochrome oxidase c subunit 1, cytochrome b. NADH dehydrogenase subunit 2) and nuclear (omega-globin intron, breast and ovarian cancer susceptibility gene) sequence data with representatives that encompassed the morphological and chromosomal variation within the genus, including for the first time both Petrogale concinna and Petrogale purpureicollis. Four distinct lineages were identified, (1) the brachyotis group, (2) Petrogale persephone, (3) Petrogale xanthopus and (4) the lateralis-penicillata group. Three of these lineages include taxa with the ancestral karyotype (2n = 22). Paraphyletic relationships within the brachyotis group indicate the need for a focused phylogeographic study. There was support for P. purpureicollis being reinstated as a full species and P. concinna being placed within Petrogale rather than in the monotypic genus Peradorcas. Bayesian analyses of divergence times suggest that episodes of diversification commenced in the late Miocene-Pliocene and continued throughout the Pleistocene. Ancestral state reconstructions suggest that Petrogale originated in a mesic environment and dispersed into more arid environments, events that correlate with the timing of radiations in other arid zone vertebrate taxa across Australia. Crown Copyright (C) 2011 Published by Elsevier Inc. All rights reserved.

Reduced muscle carnosine content in type 2, but not in type 1 diabetic patients

Carnosine is present in high concentrations in skeletal muscle where it contributes to acid buffering and functions also as a natural protector against oxidative and carbonyl stress. Animal studies have shown an anti-diabetic effect of carnosine supplementation. High carnosinase activity, the carnosine degrading enzyme in serum, is a risk factor for diabetic complications in humans. The aim of the present study was to compare the muscle carnosine concentration in diabetic subjects to the level in non-diabetics. Type 1 and 2 diabetic patients and matched healthy controls (total n = 58) were included in the study. Muscle carnosine content was evaluated by proton magnetic resonance spectroscopy (3 Tesla) in soleus and gastrocnemius. Significantly lower carnosine content (-45%) in gastrocnemius muscle, but not in soleus, was shown in type 2 diabetic patients compared with controls. No differences were observed in type 1 diabetic patients. Type II diabetic patients display a reduced muscular carnosine content. A reduction in muscle carnosine concentration may be partially associated with defective mechanisms against oxidative, glycative and carbonyl stress in muscle.

Beta-alanine (Carnosyn (TM)) supplementation in elderly subjects (60-80 years): effects on muscle carnosine content and physical capacity

The aim of this study was to investigate the effects of beta-alanine supplementation on exercise capacity and the muscle carnosine content in elderly subjects. Eighteen healthy elderly subjects (60-80 years, 10 female and 4 male) were randomly assigned to receive either beta-alanine (BA, n = 12) or placebo (PL, n = 6) for 12 weeks. The BA group received 3.2 g of beta-alanine per day (2 x 800 mg sustained-release Carnosyn (TM) tablets, given 2 times per day). The PL group received 2 x (2 x 800 mg) of a matched placebo. At baseline (PRE) and after 12 weeks (POST-12) of supplementation, assessments were made of the muscle carnosine content, anaerobic exercise capacity, muscle function, quality of life, physical activity and food intake. A significant increase in the muscle carnosine content of the gastrocnemius muscle was shown in the BA group (+85.4%) when compared with the PL group (+7.2%) (p = 0.004; ES: 1.21). The time-to-exhaustion in the constant-load submaximal test (i.e., TLIM) was significantly improved (p = 0.05; ES: 1.71) in the BA group (+36.5%) versus the PL group (+8.6%). Similarly, time-to-exhaustion in the incremental test was also significantly increased (p = 0.04; ES 1.03) following beta-alanine supplementation (+12.2%) when compared with placebo (+0.1%). Significant positive correlations were also shown between the relative change in the muscle carnosine content and the relative change in the time-to-exhaustion in the TLIM test (r = 0.62; p = 0.01) and in the incremental test (r = 0.48; p = 0.02). In summary, the current data indicate for the first time, that beta-alanine supplementation is effective in increasing the muscle carnosine content in healthy elderly subjects, with subsequent improvement in their exercise capacity.

Multivariate analysis in the maximum strength performance

This study performed an exploratory analysis of the anthropometrical and morphological muscle variables related to the one-repetition maximum (1RM) performance. In addition, the capacity of these variables to predict the force production was analyzed. 50 active males were submitted to the experimental procedures: vastus lateralis muscle biopsy, quadriceps magnetic resonance imaging, body mass assessment and 1RM test in the leg-press exercise. K-means cluster analysis was performed after obtaining the body mass, sum of the left and right quadriceps muscle cross-sectional area (Sigma CSA), percentage of the type II fibers and the 1RM performance. The number of clusters was defined a priori and then were labeled as high strength performance (HSP1RM) group and low strength performance (LSP1RM) group. Stepwise multiple regressions were performed by means of body mass, Sigma CSA, percentage of the type II fibers and clusters as predictors' variables and 1RM performance as response variable. The clusters mean +/- SD were: 292.8 +/- 52.1 kg, 84.7 +/- 17.9 kg, 19249.7 +/- 1645.5 mm(2) and 50.8 +/- 7.2% for the HSP1RM and 254.0 +/- 51.1 kg, 69.2 +/- 8.1 kg, 15483.1 +/- 1 104.8 mm(2) and 51.7 +/- 6.2 %, for the LSP1RM in the 1RM, body mass, Sigma CSA and muscle fiber type II percentage, respectively. The most important variable in the clusters division was the Sigma CSA. In addition, the Sigma CSA and muscle fiber type II percentage explained the variance in the 1RM performance (Adj R-2 = 0.35, p = 0.0001) for all participants and for the LSP1RM (Adj R-2 = 0.25, p = 0.002). For the HSP1RM, only the Sigma CSA was entered in the model and showed the highest capacity to explain the variance in the 1RM performance (Adj R-2 = 0.38, p = 0.01). As a conclusion, the muscle CSA was the most relevant variable to predict force production in individuals with no strength training background.

Distribuição do nervo ibular comum em fetos de equinos e descrição anatômica de pontos para bloqueio anestésico

Analisou-se a distribuição do nervo fibular comum em 30 fetos de equinos, sem raça definida, provenientes do acervo do Laboratório de Anatomia Animal da Faculdade de Medicina Veterinária da Universidade Federal de Uberlândia, que foram injetados e conservados em solução aquosa de formaldeído a 10%. Contatou-se que o referido nervo deriva do isquiático, divide-se em nervos fibulares superficial e profundo, distribuindo-se para os músculos extensores lateral e longo do dedo, fibular terceiro e tibial cranial. Traçando-se uma linha imaginária na região médio-lateral da tuberosidade do osso tíbia, o nervo fibular comum pode ser bloqueado em sua parte proximal, no terço caudal, entre o tendão de inserção do músculo bíceps femoral e a face lateral do músculo gastrocnêmio lateral (terço médio); e o nervo fibular profundo, na parte proximal da tíbia, crânio-distalmente ao fibular comum. O bloqueio do nervo fibular superficial pode ser realizado em duas regiões da tíbia: na proximal, considerando-se a linha imaginária, distalmente ao ponto citado para o fibular comum e caudalmente ao descrito para o fibular profundo; e na distal, na face lateral da articulação tíbio-társica, entre os tendões de inserção dos músculos extensores lateral e longo do dedo.

Análise eletromiográfica dos músculos da coxa no exercício agachamento afundo até a exaustão

O agachamento afundo possui um posicionamento dos membros inferiores diferencial em relação ao agachamento padrão, necessitando de maiores esclarecimentos acerca das participações dos músculos envolvidos. O objetivo foi analisar a atividade eletromiográfica dos músculos vastus lateralis (VL), vastus medialis (VM), bíceps femoris (BF) e semitendinosus (ST) durante a execução do agachamento afundo até à exaustão com o membro inferior posicionado frontalmente e posteriormente. Participaram do estudo nove mulheres ativas com média (DP) de idade de 22 (3,4) anos e massa corporal 60,3 (4,1) kg. O agachamento afundo foi dividido em duas etapas, diferindo apenas o posicionamento do membro inferior dominante (randomizado). Os sinais eletromiográficos foram captados utilizando um eletromiógrafo e analisados os valores "root mean square" (RMS) na fase concêntrica. Os resultados indicaram um aumento significativo do RMS em função do tempo para o membro inferior posicionado frontalmente e posteriormente (p< 0,001). No membro posicionado frontalmente, o aumento do RMS correspondeu a 50% para o VL, 54% para o VM e 48% para o BF. O membro posicionado posteriormente apresentou um aumento de 75% para o VL, 113% para o VM, 62% para o BF e 48% para o ST. O RMS também foi significativamente maior no músculo VM em relação ao ST no membro inferior posicionado anteriormente (p = 0,03) e em relação ao ST e BF no membro inferior posicionado posteriormente (p = 0,02). Não ocorreu interação significativa entre o efeito do tempo e músculo na atividade eletromiográfica. O RMS normalizado não apresentou diferenças estatisticamente significativas no que se refere ao posicionamento do membro inferior dominante. A atividade muscular foi semelhante em ambos os posicionamentos do membro inferior, apresentando maior aumento de ativação dos músculos VL e VM em relação ao BF e ST.