Monday, November 14, 2016

EXTENDED REST BETWEEN WEIGHT-LIFTING SETS COULD HELP MUSCLES GROWTH

Researchers from the University of Birmingham have found that extended rest intervals between sets of weight-lifting could help with muscle growth.



The findings, published in Experimental Physiology, go against the conventional belief that favours shorter periods of rest. The study highlights that short rest intervals may actually impair the processes that control muscle growth.


16 males completed resistance exercises interspersed by either one minute or five minutes of rest. Muscle biopsies were obtained at 0, 4, 24 and 28 hours post-exercise and analysed to determine myofibrillar protein synthesis (MPS) and intercellular signalling.
In the early part of recovery, the increase in MPS from resting levels was two-fold greater in those with longer rest periods. They saw a 152% increase, versus 76% increase in those with short rest intervals.




Dr Leigh Breen, from the University of Birmingham, explained, "With short rests of one minute, though the hormonal response is superior, the actual muscle response is blunted. If you're looking for maximised muscle growth with your training programme, a slightly longer interval between sets may provide a better chance of having the muscle response you're looking for."
The team recommend that novices starting out on weight training programs should take sufficient rest, of at least 2-3 minutes, between weight lifting sets.
Dr Breen added, "Over time, they may need to find ways to push beyond the plateau of muscle building that commonly occurs, and so may gradually decrease their rest periods. For experienced lifters, it's possible that they may not experience the same blunted muscle building response to short rest intervals, particularly if they have trained this way for a prolonged period and adapted to this unique metabolic stress. Nonetheless, similar recommendations of 2-3 minutes between sets should help to ensure maximal muscle growth in well trained individuals."
The research team are currently following up the investigation with a longer term study to see effects over a number of months, and further research into how individuals can maximise their training outcomes by manipulating variables, such a rest, in their training.



Journal Reference:
  1. James McKendry, Alberto Pérez-López, Michael McLeod, Dan Luo, R. Dent, Benoit Smeuninx, Jinglei Yu, Angela. E. Taylor, Andrew Philp, Leigh Breen. Short inter-set rest blunts resistance exercise-induced increases in myofibrillar protein synthesis and intracellular signaling in young malesExperimental Physiology, 2016; DOI: 10.1113/EP085647

Sunday, November 13, 2016

HOW HIGH-PROTEIN DIETS CAUSE WEIGHT LOSS

A common end-product of digested protein -- phenylalanine -- triggers hormones that make rodents feel less hungry and leads to weight loss, according to a new study presented at the Society for Endocrinology annual conference in Brighton.




A better understanding of the mechanism by which protein diets cause weight loss could lead to the development of drugs and diets that tackle the growing obesity epidemic.




Hormones drive our appetite by telling us when we are hungry, and when we are full. Ghrelin is a hormone that tells us when we are hungry. In contrast, high levels of the hormone GLP-1 tell us when we have had enough food and tell our bodies to stop eating. Understanding the mechanisms by which hormones affect our feeding patterns may help identify new ways of treating or preventing obesity. Previous studies have shown that protein-rich diets encourage weight loss by making people feel fuller, though these diets are difficult to adhere to and the mechanisms by which this happens is unknown.

In this study, researchers Mariana Norton and Amin Alamshah from Imperial College London ran a number of experiments on both mice and rats. In the first experiment, they gave 10 rats and mice a single dose of phenylalanine, a chemical produced in the gut when our body breaks down protein-rich foods, such as beef, fish, milk and eggs. In the second experiment, diet-induced obese mice, which are typically used as a model of human obesity, were given phenylalanine repeatedly over seven days. Both experiments compared their results to the same number of rodents that were not given phenylalanine.




The researchers found that the single-dose of phenylalanine reduced food intake, increased levels of GLP-1 and decreased levels of ghrelin. Repeated administration also caused weight loss in the obese mice. The researchers also observed that the rats were moving around more, which might encourage them to lose weight.

To understand the mechanisms by which phenylalanine might be stimulating these hormones, the researchers carried out a final experiment by studying gut cells in a petri dish. They found that phenylalanine interacted with a receptor called the calcium sensing receptor (CaSR), and that it was CaSR in turn causing levels of GLP-1 to increase and appetite to decrease.

"Our work is the first to demonstrate that activating CaSR can suppress appetite," said lead author of the study Mariana Norton. "It highlights the potential use of phenylalanine or other molecules which stimulate CaSR -- like drugs or food components -- to prevent or treat obesity."

According to Miss Norton, the precise mechanisms by which phenylalanine suppresses appetite and body weight still need to be determined, and there are likely to be additional mechanisms which are also involved in the beneficial effects of a high protein diet.

The researcher's next steps will be to establish whether phenylalanine can produce the same effects in humans as in mice, and to further confirm the importance of CaSR in our response to protein-rich foods.




The study L- Phenylalanine modulates gut hormone release, and suppresses food intake in rodents via the Calcium Sensing Receptor will be presented by Miss Mariana Norton at the Society for Endocrinology BES 2016 Conference in Brighton.

The Society for Endocrinology BES 2016 Conference is held 7-9 November 2016 in Brighton, UK. The Conference brings together the best of basic science, translation research, clinical investigation and clinical practice. 


The Society for Endocrinology is a UK- based membership organisation representing a global community of scientists, clinicians and nurses who work with hormones. Further information can be found at www.endocrinology.org

Materials provided by Society for Endocrinology