Resistance training has been unparalleled as a mechanism to alter body composition configuration. Elevated post-exercise oxygen consumption has been linked to the longest elevated levels following intense resistance training. This form of exercise trumps high-intensity-interval training, endurance training, and other types of exercise stimuli in producing favorable body composition. It’s been long thought that an increased oxygen consumption following a period of oxygen debt would increase metabolic rate since oxygen is a common contributor to the chemical reactions that release energy to perform work. Although this is true in theory, it appears that the response to resistance training isn’t as predictable as once believed. It’s now become apparent that the weight-loss response to resistance exercise is not static, but dynamic and fluid. The response differs according to an individual’s genetic risk for obesity.
Researchers used a one-year randomized exercise intervention study, which is more structured and reliable than previous studies based on self-reported activity level. The exercise program included supervised, high-intensity resistance training and moderate impact weight-bearing exercise for 75 minutes, 3 days/week for 12 months. Strength was assessed every six-to-eight weeks to maintain intensity and increase the load. The participation percentage was 77.3% of the time on average, totaling to 2.3 days/week out of a possible 3 days/week. The results were an increase in strength, reduction in body fat percentage, and a higher % of soft tissue mass. Several differences existed, signifying inter-variability of phenotype expression changes according to the genetic predisposition for higher levels of fat mass. The association of exercise with phenotype change is strongest amongst those individuals with low genetic risk for obesity.
The subsequent results of resistance training adaptation following loaded exercise remains due to a complex interaction of several single nucleotide polymorphisms (SNP). It’s theorized that exercise will change the way that these genes are expressed. Since a majority of identified BMI-associated genes are found within the hypothalamus, it’s fair to consider that regulation or maintenance of body weight can be related to the role of the hypothalamus as well. The hypothalamus is a regulator of many bodily systems and regularly modifies the electrolyte and fluid balance, body temperature, blood pressure, and body weight. It’s no surprise that more functions of the hypothalamus can be tied directly to variables that affect weight loss or gain.
The strengths of the research are that researchers used a supervised, randomized exercise intervention that was of adequate length. This contrasted previous researcher which used only self-reporting assessments on physical activity. Researchers measured phenotypical measurements of body composition before and after the intervention. This helped assess the impact and degree of adaptation in response to the training regimen. Lastly, control of environmental variance through randomized intervention helped detect the genetic effects of the program.
This paper represents a detailed summation of the information processed in exercise physiology. The paper touches slightly on the mechanisms of the transduction signal hypothesis, phenotype alteration from gene expression, and the complex interactions that lead to adaptation. A theme for the entire paper has been that the mechanisms and the pathways that adaptations stem from are universal while the degree of alteration and the stimulus that activates the pathway can be varied. Another excellent reminder that one size does not fit all, and that individual modifications can be expected and must be measured to understand their personal expressions of genes and their roles in phenotype alteration. Going forward, health professionals must recognize this unique quality of all individuals and honor their pre-determined genetic make-up. The attention to detail, and assumption that not everything will work by the books, will provide the health professional with a greater understanding of the individual and how to properly conduct their exercise program.