Physiology - Effects of Moderate

Physiology - Effects of Moderate Exercise on Metabolic Responses and Respiratory Exchange Ratio (RER)

"Effects of Moderate Exercise on Metabolic Responses and Respiratory Exchange Ratios (RER)."

The purpose of this study (Kaoru et al. 109) was to determine if a significant relationship exists between metabolic responses, in this case respiratory exchange ratios (RER), and exercise duration. The aim is to discover the level of exercise required in order to combat insulin resistance, which can be a significant problem for individuals who require such treatment. Insulin resistance must be counteracted by increasing the utilization of fatty acids in the blood stream as well as in adipose tissue (109). While the authors admitted that endurance-level exercise has been positively correlated with increased utilization rates, there has been less evidence to support the notion that variable amounts of exercise could have a similar effect.

The hypothesis of the study is that fatty acids are available for energy even following short-term exercise (109). In other words, the authors designed this study to test the notion that fatty acid utilization could be increased even following lower levels of physical exertion and exercise. If this proved to be the case, then it would open up an incredible wealth of exercise methods and regiments for counteracting insulin resistance.

The subject in the study included nine individuals who were untrained, and yet still healthy. Of the nine, two were women and the remaining seven were men. The mean age was 23 and the mean BMI score was 20.6 (110). Participants were directed to come to the study after an overnight fast. After some initial blood work and measurements were taken, the participants each took part in thirty minutes of moderate exercise to achieve a heart rate of roughly 120 beats per minute. After the exercise trial, further measurements were taken and subsequent blood work also taken (110).

The results of the study were relatively straightforward. The mean RER was 0.89, with a mean heart rate of 115 beats per minute. The blood tests revealed that, on average, plasma glucose (PG) and plasma immunoreactive insulin (IRI) decreased after the test. Simultaneously, plasma free fatty acid (FFA) levels actually increased (112). In this study, then, moderate exercise for thirty minutes actually increased fatty acid utilization. This means that some benefit can be discerned toward fighting insulin resistance with only light to moderate exercise at shortened intervals. The authors of the study did concede that the dominant metabolic substrate was still carbohydrates, but that the low-level exercise regimen nonetheless had a positive effect on fatty acid utilization (113).

The implications and conclusion of these results are evident, as the authors concluded. Insulin resistance can be lowered even when the subject only utilizes a short-term, repetitive, regular, and low intensity exercise regimen (113). The potential applications for patients who have difficulty managing their insulin levels are obvious should the results of this study stand up to verification.

Part Two: Critique

This critique consists of a reasoned evaluation of the scientific merit of the study summarized above, "Effects of Moderate Exercise on Metabolic Responses and Respiratory Exchange Ration (RER)" by Kaoru et al. This author determined in the course of evaluating that study that while the authors' rationale and hypothesis for the study were justified and verifiable, the execution of the study -- or at least the presentation of that execution in the published paper -- lacked some of the scientific rigor that would make the study truly worthwhile.

The rationale for the study contained scientific merit. The introduction of the study explains that combating insulin resistance can be a significant health problem. Therefore, understanding the ways in which insulin resistance can be counteracted is critical toward developing strategies to help individuals with insulin resistance issues. Kaoru et al. explain that increasing fatty acid utilization fights insulin resistance, and that exercise is known to increase utilization (109). The question mark, as the authors explain, is how much exercise and at what level is required in order to facilitate fatty acid utilization. Therefore the rationale for designing a study to probe this question was well founded.

The hypothesis of the study was similarly well-structured. As already mentioned, the study was designed to test the hypothesis that fatty acids are available for utilization in the body even following short-term exercise at low levels of intensity (109). This is a positive hypothesis, one that is designed to demonstrate a conclusion the authors are interested in finding. The study could have, in theory, been designed in an opposite fashion on the assumption that low levels of exercise will not increase fatty acid utilization. Nonetheless, the hypothesis was thoughtfully reasoned and conformed to the rationale of the study. The proposed study seemed, at first brush, to be adequate toward the intended goal.

The methods and design of the study, however, unfortunately demonstrated some inadequacies that test the scientific merit of the study. Most glaringly, the population size selected for the study was limited to nine individuals. While their collective characteristics were appropriate for the tests, the limitations in size could produce any number of complications for the results perhaps by unintentionally skewing the data set. No explicit reason was provided for the selection of such a limited population; this evaluation is left to wonder if budgetary constraints or an unmentioned variable had a hand in limiting the study's scope to a sample of only nine individuals. Additionally, little to no information was provided regarding the controls placed on the study or the statistical analysis methods employed. Readers have no basis to develop an informed conclusion regarding the scientific merit of the study's design and implementation.

The results of the study were presented in a relatively easy to understand manner. The authors may have benefited from a better format or more clearly worded descriptions, but overall the results were quite comprehensible and thorough. The results of all of the tests that were run, as well as accompanying graphs, were included. All of these results demonstrated the fact that fatty acid utilization does occur, albeit in limited amounts, even during low to moderate intensity exercise regimens (112-113).