Variable, but not free-weight, resistance back squat exercise potentiates jump performance following a comprehensive task-specific warm-up

Studies examining acute, high-speed movement performance enhancement following intense muscular contractions (frequently called "post-activation potentiation"; PAP) often impose a limited warm-up, compromizing external validity. In the present study, the effects on countermovement vertical jump (CMJ) performance of back squat exercises performed with or without elastic bands during warm-up were compared. After familiarization, fifteen active men visited the laboratory on two occasions under randomized, counterbalanced experimental squat warm-up conditions: (a) free-weight resistance (FWR) and (b) variable resistance (VR). After completing a comprehensive task-specific warm-up, three maximal CMJs were performed followed by three back squat repetitions completed at 85% of 1-RM using either FWR or VR Three CMJs were then performed 30 seconds, 4 minutes, 8 minutes, and 12 minutes later. During CMJ trials, hip, knee, and ankle joint kinematics, ground reaction force data and vastus medialis, vastus lateralis, and gluteus maximus electromyograms (EMG) were recorded simultaneously using 3D motion analysis, force platform, and EMG techniques, respectively. No change in any variable occurred after FWR (P > 0.05). Significant increases (P < 0.05) were detected at all time points following VR in CMJ height (5.3%-6.5%), peak power (4.4%-5.9%), rate of force development (12.9%-19.1%), peak concentric knee angular velocity (3.1%-4.1%), and mean concentric vastus lateralis EMG activity (27.5%-33.4%). The lack of effect of the free-weight conditioning contractions suggests that the comprehensive task-specific warm-up routine mitigated any further performance augmentation. However, the improved CMJ performance following the use of elastic bands is indicative that specific alterations in force-time properties of warm-up exercises may further improve performance

Melatonin Promotes Oligodendroglial Maturation of Injured White Matter in Neonatal Rats

OBJECTIVE:To investigate the effects of melatonin treatment in a rat model of white matter damage (WMD) in the developing brain. Additionally, we aim to delineate the cellular mechanisms of melatonin effect on the oligodendroglial cell lineage. METHODS:A unilateral ligation of the uterine artery in pregnant rat at the embryonic day 17 induces fetal hypoxia and subsequent growth restriction (GR) in neonatal pups. GR and control pups received a daily intra-peritoneal injection of melatonin from birth to post-natal day (P) 3. RESULTS:Melatonin administration was associated with a dramatic decrease in microglial activation and astroglial reaction compared to untreated GR pups. At P14, melatonin prevented white matter myelination defects with an increased number of mature oligodendrocytes (APC-immunoreactive) in treated GR pups. Conversely, melatonin was not found to be associated with an increased density of total oligodendrocytes (Olig2-immunoreactive), suggesting that melatonin is able to promote oligodendrocyte maturation but not proliferation. These effects appear to be melatonin-receptor dependent and were reproduced in vitro. INTERPRETATION:These data suggest that melatonin has a strong protective effect on developing damaged white matter through decreased microglial activation and oligodendroglial maturation leading to a normalization of the myelination process. Consequently, melatonin should be a considered as an effective neuroprotective candidate not only in perinatal brain damage but also in inflammatory and demyelinating diseases observed in adults

Regional fat mobilization and training type on sedentary, premenopausal overweight and obese women.

OBJECTIVE: Little is known about the influence of different training types on relative fat mobilization with exercise. The purpose of this study was to analyze the changes induced by aerobic training (AT), resistance (RT) or a combination of both (AT+RT) on total fat mass (TFM) and regional fat mass (RFM). Further, the relative contribution of different regions, upper limbs (UL), lower limbs (LL), and trunk (Tr), were compared. DESIGN AND METHODS: Forty-five overweight and premenopausal women were randomized in either AT, RT or AT+RT. All training groups exercised for the same duration (60 min), 3 times per week for 5 months. Body composition was estimated using dual energy X-ray absorptiometry. RESULTS: TFM decreased significantly in all groups (-4.6 ± 1.9 kg; -3.8 ± 2.6 kg, and -4.7 ± 3.0 kg in AT, RT, and AT+RT groups respectively; P &lt; 0.001). The relative contribution of FM into each segment changed significantly: TrFM represented 46.6% ± 5.8% of TFM at baseline and reduced to 43.1% ± 5.5% (P &lt; 0.001); LLFM was 39.7% ± 5.8% vs. 41.6% ± 5.7% (P &lt; 0.01); ULFM was 11.3% ± 1.3% vs. 12.2% ± 1.4% (P &lt; 0.01). CONCLUSION: Training type did not influence changes of TFM and RFM. Fat mobilization came predominantly from Tr in all training protocols. These findings suggest that overweight and obese women can reduce TFM and RFM, independently of training type

Reprodutibilidade do teste de 1-RM em indivíduos com doença arterial obstrutiva periférica Reproducibility of the 1-RM test in individuals with peripheral obstructive arterial disease

INTRODUÇÃO: Indivíduos com doença arterial obstrutiva periférica (DAOP) apresentam atrofia muscular e redução da força de membros inferiores que, por sua vez, estão associadas às limitações na capacidade funcional. Consequentemente, a mensuração da força muscular pode ser útil na identificação dos níveis de força muscular e para monitorar as alterações na força em programas de intervenção. OBJETIVO: Analisar a reprodutibilidade do teste de uma repetição máxima (1-RM) em indivíduos com DAOP. Métodos: Fizeram parte da amostra 26 indivíduos com DAOP e sintomas de claudicação intermitente. Os indivíduos realizaram quatro sessões de teste de 1-RM no exercício extensão de joelhos unilateral, no membro com maior índice tornozelo-braço (ITB) e no membro com menor ITB. RESULTADOS: A força máxima aumentou significantemente da primeira para a segunda sessão de teste nos dois membros (4,1 ± 14,3% na perna com menor ITB e 5,9 ± 13,1% na perna com maior ITB). A análise dos limites de concordância revelou que, nos dois membros, as maiores diferenças médias e os maiores limites de concordância foram observados quando comparadas as sessões 1 e 2. CONCLUSÃO: A medida acurada da força máxima usando o teste de 1-RM, no exercício extensão de joelhos, em indivíduos com DAOP e sintomas de claudicação intermitente, é obtida quando duas sessões de testes de 1-RM são realizadas.<br>INTRODUCTION: Patients with peripheral obstructive arterial disease (PAD) present muscle atrophy and reduced strength in the legs which have been associated with impairment in physical function. Consequently, the assessment of leg strength can be useful for identifying muscle weakness and analyzing the efficacy of intervention programs for patients with PAD. OBJECTIVE: To assess the reliability of the 1-RM test in patients with PAD. Methods: The sample was composed of twenty-six patients with PAD and symptoms of mild intermittent claudication. Patients performed the 1-RM tests in the knee extension exercise in the leg with lower ankle brachial index (ABI) and in the leg with higher ABI. This protocol was repeated in four sessions to assess the reliability of the maximum strength measurements. RESULTS: Maximal strength increased significantly from session 1 to session 2 in both legs (4.1 ± 14.3% in the leg with lower ABI and 5.9 ± 13.1% in the leg with higher ABI). The analysis of agreement revealed that higher bias and higher limits of agreement were observed in both legs when sessions 1 and 2 were compared. CONCLUSION: Reliable assessment of strength using 1-RM test in knee extension exercise in patients with PAD and symptoms of intermittent claudication is obtained when 2 test sessions are performed