A brief review: factors affecting the length of the rest interval between resistance exercise sets

Research has indicated that multiple sets are superior to single sets for maximal strength development. However, whether maximal strength gains are achieved may depend on the ability to sustain a consistent number of repetitions over consecutive sets. A key factor that determines the ability to sustain repetitions is the length of rest interval between sets. The length of the rest interval is commonly prescribed based on the training goal, but may vary based on several other factors. The purpose of this review was to discuss these factors in the context of different training goals. When training for muscular strength, the magnitude of the load lifted is a key determinant of the rest interval prescribed between sets. For loads less than 90% of 1 repetition maximum, 3-5 minutes rest between sets allows for greater strength increases through the maintenance of training intensity. However, when testing for maximal strength, 1-2 minutes rest between sets might be sufficient between repeated attempts. When training for muscular power, a minimum of 3 minutes rest should be prescribed between sets of repeated maximal effort movements (e.g., plyometric jumps). When training for muscular hypertrophy, consecutive sets should be performed prior to when full recovery has taken place. Shorter rest intervals of 30-60 seconds between sets have been associated with higher acute increases in growth hormone, which may contribute to the hypertrophic effect. When training for muscular endurance, an ideal strategy might be to perform resistance exercises in a circuit, with shorter rest intervals (e.g., 30 seconds) between exercises that involve dissimilar muscle groups, and longer rest intervals (e.g., 3 minutes) between exercises that involve similar muscle groups. In summary, the length of the rest interval between sets is only 1 component of a resistance exercise program directed toward different training goals. Prescribing the appropriate rest interval does not ensure a desired outcome if other components such as intensity and volume are not prescribed appropriately.     

Group formation and anemone use in captively reared anemonefish (<Emphasis Type="Italic">Amphiprion frenatus</Emphasis>)

We studied group formation and anemone use in captively reared anemonefish Amphiprion frenatus. Four small fish (23–32 mm total length) were simultaneously released into a central area of the aquaria (ca. 160 l) that was divided in half with an anemone placed on each half, with the opportunity to settle on either side. Four-day trials were conducted for analyzing settlement patterns. Because of the monogamous mating system, we predicted that small fish should settle in pairs. However, all four small fish settled on the same side in 7 of 14 replicates, which was a higher than expected value under random settlement.     

Gramicidin-D-stimulated influx of monovalent cations into plant roots

Summary Gramicidin D and nigericin were found to stimulate K⁺ influx into oat roots. Valinomycin and nonactin had little effect on K⁺ influx. The region of the root most sensitive to gramicidin was the elongation zone. Monocot roots were more sensitive to gramicidin than dicot roots. At 0.2 mM KCl, gramicidin stimulated K⁺ influx by 4- to 8fold over a 30-min absorption period. Although a gramicidin response is detectable within one minute, maximum stimulation occurred after a slight (approximately 2-min) lag period. The gramicidin effect was much greater at 0.2 mM KCl than at 20 mM KCl. Respiratory inhibitors reduced the gramicidin-stimulated K⁺ influx by 50–80%. The results are discussed in terms of possible mechanisms of action of the various ionophores on ion transport in roots.This work was supported by National Science Foundation Grants GB-5549 and GB-12674 and by the Illinois Agriculture Experiment Station.     

Specific suppression of insulin sensitivity in growth hormone receptor gene‐disrupted (GHR‐KO) mice attenuates phenotypic features of slow aging

In addition to their extended lifespans, slow‐aging growth hormone receptor/binding protein gene‐disrupted (knockout) (GHR‐KO) mice are hypoinsulinemic and highly sensitive to the action of insulin. It has been proposed that this insulin sensitivity is important for their longevity and increased healthspan. We tested whether this insulin sensitivity of the GHR‐KO mouse is necessary for its retarded aging by abrogating that sensitivity with a transgenic alteration that improves development and secretory function of pancreatic β‐cells by expressing Igf‐1 under the rat insulin promoter 1 (RIP::IGF‐1). The RIP::IGF‐1 transgene increased circulating insulin content in GHR‐KO mice, and thusly fully normalized their insulin sensitivity, without affecting the proliferation of any non‐β‐cell cell types. Multiple (nonsurvivorship) longevity‐associated physiological and endocrinological characteristics of these mice (namely beneficial blood glucose regulatory control, altered metabolism, and preservation of memory capabilities) were partially or completely normalized, thus supporting the causal role of insulin sensitivity for the decelerated senescence of GHR‐KO mice. We conclude that a delayed onset and/or decreased pace of aging can be hormonally regulated.     

Transcriptome analyses suggest a disturbance of iron homeostasis in soybean leaves during white mould disease establishment

Sclerotinia sclerotiorum is a serious pathogen of numerous crops around the world. The major virulence factor of this pathogen is oxalic acid (OA). Mutants that cannot produce OA do not cause disease, and plants that express enzymes that degrade OA, such as oxalate oxidase (OxO), are very resistant to S. sclerotiorum. To examine the effect of OA on plants, we infiltrated soybean leaves with 5 mm OA and examined the gene expression changes at 2 h post‐infiltration. By comparing the gene expression levels between leaves of a transgenic soybean carrying an OxO gene (OxO) and its parent AC Colibri (AC) infiltrated with OA (pH 2.4) or water (pH 2.4 or 5.5), we were able to compare the effects of OA dependent or independent of its pH. Gene expression by microarray analysis identified 2390 genes that showed changes in expression, as determined using an overall F‐test P‐value cut‐off of 0.001. The additional requirement that at least one pairwise t‐test false discovery rate (FDR)‐corrected P value should be less than 0.001 reduced the list of the most highly significant differentially expressed genes to 1054. Independent of pH, OA altered the expression levels of 78 genes, with ferritin showing the strongest induction by OA. The combination of OA plus its low pH caused 1045 genes (99% of all significant genes) to be differentially expressed, with many of the up‐regulated genes being related to basal defence, such as genes of the phenylpropanoid pathway and various cytochrome P450s. RNA‐seq was also conducted on four samples: OxO and AC genotypes infiltrated with either OA pH 2.4 or water pH 2.4. The RNA‐seq analysis also identified ferritin paralogues as being strongly induced by OA. As the expression of ferritin, a gene that encodes for an iron storage protein, is induced by free iron, these results suggest that S. sclerotiorum benefits from the ability of OA to free iron from plant proteins, as this induces host cell death, and also allows the uptake and assimilation of the iron for its own metabolic needs.     

Bubbles: A Many-Sided Project

Abstract

Seed to Civilization/The Story of Man's Food by Charles B. Heiser, Jr., W. H. Freeman and Co., 660 Market Street, San Francisco, Calif. 94104, 1973, 243pp., references and index, $7.50. Reviewed by Robert C. Hayden

A Guide to the National Parks/Their Landscape and Geology by William H. Matthews III, Doubleday/Natural History Press, Garden City, New York, 1973, 529pp., selected readings, glossary and index, $5.95. Reviewed by Robert C. Hayden

Wandering Lands and Animals by Edwin H. Colbert, E. P. Dutton, 201 Park Avenue South, New York, N.Y. 10003, 1973, 32pp., bibliography, glossary and index, $12.50. Reviewed by Robert C. Hayden

Astronomy in Color by Peter Lancester Brown, The MacMillan Co., 866 Third Avenue, New York, N.Y. 10022, 1972, 265pp., appendices, glossary and index, $4.95. Reviewed by Robert C. Hayden

The Facts of Flight by Jerry Grey, a Franklin Institute book, Westminster Press, Philadelphia, Penn., 1973, 135pp., glossary and index. Reviewed by Robert C. Hayden

Zoos are News/Conservation or Extinction? by Cyril Bracegirdle, Abelard-Schuman Ltd., 257 Park Avenue South, New York, N.Y. 10010, 1973, 176pp., index, $5.95. Reviewed by Robert C. Hayden     

Baltic amber Ibaliidae (Hymenoptera: Cynipoidea): a new genus with implications for the phylogeny and historical biogeography of the family

Abstract. The first definitive ibaliid wasp (Cynipoidea: Ibaliidae) is described and illustrated from a female preserved in middle Eocene (Lutetian) Baltic amber. Archaeibalia succinica Liu & Engel gen. et sp.n. is distinct from all other members of the family, cladistically placed as sister to all other Ibaliidae, and classified in its own subfamily, Archaeibaliinae Liu & Engel subfam.n. The genus was putatively a parasitoid of wood‐boring insects in hardwood trees. Given that the species is exceptionally rare in Baltic amber (a single individual) despite a habitat that would have placed it in immediate proximity with resin flows, the host of A. succinica was probably not living in the ‘Baltic amber tree’. The historical biogeography and evolution of ibaliids is reconsidered based on the present paleontological evidence.