Moderate intensity and volume downhill run does not impair knee joint stability at early and late phases of quadriceps/hamstrings contraction

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeito agudo de diferentes intensidades de exercícios com pesos sobre o volume e a contração voluntária máxima isométrica, em idosas treinadas

The prescription of strength training intensity (ST) by maximum repetition (RM) is characterized by a decrease in the number of repetitions in multiple series. Some studies have shown that reductions in the intensity of exercise can optimize the volume of training with similar acute neuromuscular behaviors. The objective of the study was to investigate the acute effect of two different ST intensities on the training volume, maximum voluntary contraction (MVC) and rate of force development (RFD) in elderly women. The study included eight trained women (66.7 ± 6.7 years; 7.6 ± 17.8 kg; 159 cm; 29.33 ± 5.80 kg/m²). They underwent to three experimental conditions: two different intensities of ST (100% and 80% of 15-RM) on a chair for Leg Extension and a control condition. In the condition to 100% of 15 RM, all participants performed three sets to the concentric muscle fatigue, whereas in the condition to 80% involved the use of two sets of 15 repetitions and only the third to the concentric muscle fatigue. The order of experimental conditions was randomized. The MVC and RFD were determined on the basis of the isometric forcetime curve analysis which was obtained by a force transducer fixed on the unit Bonnet Chair, in the pre and after four and ten minutes for each experimental conditions. The total volume was calculated by multiplying the number of repetitions in three sets by the load in kg. Descriptive statistical analysis procedures were employed (mean ± standard deviation) in addition to two-way ANOVA. The level of significance was set at p <0.05. It was neither main effect of moment or condition, nor condition x moment interaction for MVC and RFD. For the total volume, no significant difference was noted between the conditions (100 and 80% of 15-RM). For sustainability of ...(Complete abstract click electronic access below)

Influência do alongamento prévio no pico de torque e na taxa de força em exercício de contração isométrica

The objective of this study was to investigate the influence of previous active static stretch on the isometric peak torque (PT) and rate of force development (RFD) measured from different time intervals from the beginning of muscle contraction. Participated of this study 15 male individuals, apparently healthy, with ages between 18 and 25 years, without regular physical activity practice. The individuals were submitted in different days to the following tests: 1) Familiarization session to the isokinetic dynamometer; 2) Two maximal isometric concentric contractions for knee extensors in isokinetic dynamometer to determine PT and RFD (Control), and; 3) Two active static stretching exercises for the dominant leg extensors (10 x 30 s for each exercise, with 20 s of rest). After the stretching, the isokinetic test was repeated (Post-Stretching). The conditions 2 and 3 were performed in random order. The RFD was considered as the mean slope of the moment-time curve at time intervals of 0-30, 0-50 and 0-100ms relative to the beginning of muscle contraction. It was verified significant reduction for both maximal RFD and PT after the stretching (p < 0.05). At intervals of 0- 30ms, 0-50ms and 0-100ms, the RFD at the conditions with stretching was similar to the RFD without stretching (p > 0.05). At intervals of 0-150ms and 0-200ms, the RFD obtained at the contraction without stretching was significantly higher that that obtained at the contraction with stretching (p < 0.05). It can be concluded that the static stretching, performed with duration of 600 s diminish isometric PT, maximal RFD and RFD measured at late phase (> 100 ms) of muscle contraction.

Efeitos do treinamento isocinético e isométrico sobre a taxa de desenvolvimento de força máxima

The objective of the present study was to compare the effects of a high speed isokinetic training (180°.s-1) and an isometric training (75°) on the maximum rate of force development (RFDmax) measured in the isokinetic and isometric modes. Twenty seven male non active subjects participated of this study (Mean + SD = body mass 78.6 + 14.1 kg; stature 175.1 + 8.9 cm; age 22.6 + 3.8 years). They were randomly divided into three groups: Control (GC); Isokinetic training (GISOC) and; Isometric training (GISOM). The subjects were submitted in different days to the following pre training protocols: 1) Familiarization to the isokinetic dynamometer tests; 2) Five maximum concentric isokinetic contractions of the knee extensors (180°.s-1) to access the maximum concentric torque (TMC) and the concentric RFDmax; 3) Two maximum isometric contractions of the knee extensors (75°) to access the maximum isometric torque (TMI) and the isometric RFDmax. The same tests were repeated after the training period, but without the familiarization session. Eighteen training sessions were performed (3 times per week). The GISOC performed the entire training whit concentric isokinetic contractions whit the speed of 180°.s-1. The GISOM performed the entire training whit isometric contractions whit the angle between the thigh end the leg being 75° (0° = full knee extension). TMI, TMC, concentric RFDmax, isometric RFDmax values of the GC was not different between pre and post training. GISOM increased only the TMI and the GSIOC increased the TMC, concentric RFDmax and isometric RFDmax. Furthermore, the GISOC had a higher percentage increase of the isometric RFDmax than the isokinetic RFDmax. Based on these results, it is possible to conclude that the increase in maximum strength corresponded to the training specificity theory, unlike to the RFDmax. Thus the use of isometric contraction ...(Complete abstract click electronic access below)

Efeito da idade e de diferentes intensidades sobre o desempenho muscular de membros superiores e inferiores em mulheres

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A simple observation concerning contraction mappings

In this short note we show that the results obtained by Walter in [4] remain valid if we change the metric by another metric. Furthermore, if we use the norm jjT; given in [3], Theorem B in[4] remains valid.

Mast cell concentration and skin wound contraction in rats treated with Brazilian pepper essential oil (Schinus terebinthifolius Raddi)

PURPOSE: To evaluate wound contraction and the concentration of mast cells in skin wounds treated with 5% BPT essential oil-based ointment in rats. METHODS: Twenty rats, male, of adult age, were submitted to skin surgery on the right (RA) and left antimeres (LA) of the thoracic region. They were divided into two groups: control (RA - wounds receiving daily topical application of vaseline and lanolin) and treated (LA - wounds treated daily with the topical ointment). The skin region with wounds were collected at days 4, 7, 14 and 21 after surgery. Those were fixed in 10% formaldehyde and later processed for paraffin embedding. Sections were obtained and stained by H.E for histopathology analysis. The degree of epithelial contraction was measured and mast cell concentration were also evaluated. RESULTS: The treated group showed higher mast cell concentrations (p<0.05) associated with increased contraction at day 7 and 14 respectively. CONCLUSION: Ointment containing 5% Brazilian pepper tree oil increases mast cell concentration and promotes skin wound contraction in rats.

Influence of neuromuscular fatigue on co-contraction between vastus medialis and vastus lateralis during isometric contractions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Eccentric torque-producing capacity is influenced by muscle length in older healthy adults

Considering the importance of muscle strength to functional capacity in the elderly, the study investigated the effects of age on isokinetic performance and torque production as a function of muscle length. Eleven younger (24.2±2.9years) and seventeen older men (62.7±2.5years) were subjected to concentric and eccentric isokinetic knee extension/flexion at 60°.s-1 and 120°.s-1 through a functional range of motion. The older group presented lower peak torque (Nm) than the young group for both isokinetic contraction types (age effect, p<0.001). Peak torque deficits in the older group were near 30% and 29% for concentric and eccentric contraction, respectively. Concentric peak torque was lower at 120.s-1 than at 60.s-1 for both groups (angular velocity effect, p<0.001). Eccentric knee extension torque was the only exercise tested that showed an interaction effect between age and muscle length (p<0.001), which suggested different torque responses to the muscle length between groups. Compared with the young group, the eccentric knee extension torque was 22% to 56% lower in the older group, with the deficits being lower in the shortened muscle length (22-27%) and higher (33-56%) in stretched muscle length. In older men, the production of eccentric knee strength seems to be muscle length-dependent. At more stretched positions, older subjects lose the capacity to generate eccentric knee extension torque. More studies are needed to assess the mechanisms involved in eccentric strength preservation with aging and its relationship with muscle length.