Effect of unilateral and bilateral resistance exercise on maximal voluntary strength,total volume of load lifted,and perceptual and metabolic responses

The present study investigated the effect of unilateral and bilateral resistance exercise (RE) on maximal voluntary strength, total volume of load lifted (TVLL), rating of perceived exertion (RPE) and blood lactate concentration of resistance-trained males. Twelve healthy men were assessed for the leg extension one-repetition maximum (1RM) strength using bilateral and unilateral contractions. Following this assessment, an RE session (3 sets of repetitions to failure) was conducted with bilateral and unilateral (both limbs) contractions using a load of 50% 1RM. The TVLL was calculated by the product of the number of repetitions and the load lifted per repetition. RPE and blood lactate were measured before, during and after each set. Session RPE was measured 30 minutes after RE sessions. There was a significant difference in the bilateral (120.0±11.9) and unilateral (135.0±20.2 kg) 1RM strength (p < 0.05). The TVLL was similar between both RE sessions. Although the repetitions decreased with each successive set, the total number of repetitions completed in the bilateral protocol (48) was superior to the unilateral (40) protocol (p < 0.05). In both bouts, RPE increased with each subsequent set whilst blood lactate increased after set 1 and thereafter remained stable (p < 0.05). The RPE and lactate responses were not significantly different between both sessions. In conclusion, a bilateral deficit in leg extension strength was confirmed, but the TVLL was similar between both RE sessions when exercising to voluntary fatigue. This outcome could be attributed to the number of repetitions completed in the unilateral RE bout. The equal TVLL would also explain the similar perceptual and metabolic responses across each RE session.     

Damage by <Emphasis Type="Italic">Tibraca limbativentris</Emphasis> Stål (Pentatomidae) to Upland Rice Cultivated in Amazon Rainforest Region (Brazil) at Different Growth Stages

In this study, we evaluated the damage caused in the field by Tibraca limbativentris Stål adults at different levels of infestation (0, 1, 2, and 4 stink bugs) per three rice plants during three growth stages (V8, V13, and R4 stages) of upland rice cultivated in southwestern of Pará State, Amazon Rainforest region, Brazil. Heading time (panicle exertion) was affected by T. limbativentris infestations mainly in the vegetative stage and the whiteheads percentage in treatments ranged from 18.2 to 38%. The dead hearts percentages varied between 0 and 21.5%, and the mean number of primary branches (ramifications) ranged from 5.9?±?0.4 to 12.3?±?0.2. The number of empty spikelets was only affected in infestations with four insects/three plants, while the quantity of filled grains per panicle was affected only when infestations occurred during the vegetative stage. The total number of spikelets (filled?+?empty) per panicle decreased significantly in all phenological stages, and the percentage of damage ranged from 17 to 44% among treatments. Based on the proportion of damage observed, we suggest doubling the number of insects presently used as action threshold to 2 and 4 stink bugs per 15 stalks sampled for the vegetative stage, and of 1 or 2 stink bugs per 15 stalks sampled at the beginning of reproductive stage (R3/R4). Also, the field should be monitored during the entire vegetative stage, since most damage was observed in this phenological stage.     

Concurrent validity of an OMNI rating of perceived exertion scale for bench stepping exercise

To develop and validate a modified OMNI rating of perceived exertion (RPE) scale for use during bench stepping exercise (OMNI-BS). Thirty women (age: 19.8 ± 1.8 years) undertook 2 experimental trials, separated by 7 days. Concurrent validity was established by examining the relation between physiological criterion variables, oxygen consumption (VO2), and heart rate (HR), with the concurrent variable, RPE from OMNI-BS, during 2 trials in which the intensity increased linearly (test 1) and intermittently (test 2). The first test consisted of 3-minute stages. Subjects stepped up and down on the bench at 120 b·min(-1). The test was terminated owing to subject fatigue. Exercise intensity increased as bench height increased every 3 minutes. The second test consisted of three 3-minute exercise bouts that reproduced exercise stage 1 (low intensity), stage 3 (moderate intensity), and stage 5 (high intensity) performed in the first test. The order of these 3 exercise bouts was counterbalanced. Intraclass correlation analysis from experimental trials indicated a strong positive association between RPE and VO2 (r = 0.96 and r = 0.95) and HR (r = 0.95 and r = 0.95). Concurrent validity for the OMNI-BS RPE scale was established for women performing bench stepping exercise.     

Abrupt species loss of the Amazonian dung beetle in pastures adjacent to species-rich forests

Anthropogenic disturbances, such as conversion of forests to pastures, are considered one of the major causes of Amazonian biodiversity loss. Pastures are hostile environments for forest species that are not adapted to the adverse conditions of open areas. The aim of this study was to analyze the effects of forest replacement by cattle pastures in the north-eastern part of the Amazonian rainforest using dung beetles (Scarabaeidae: Scarabaeinae) as indicators. Therefore, we determined edge effects and differences in dung beetle species richness, composition, and abundance between forest and neighbouring cattle pastures. A total of 6723 individuals of 63 species of dung beetle were collected. In comparison to forests, adjacent pastures were sharply less rich and abundant in dung beetles. The forests had 6604 individuals and 59 species, while the pastures had 119 individuals and 12 species. The replacement of forests by pastures results in an increase of dung beetle species turnover. Only 12% of dung beetle species were shared by both forest and pasture environments. We highlight that most Amazonian dung beetles are forest species sensitive to abrupt human-driven modification of habitats and are only moderately affected by edge effects.