The gut microbiome forms a large part of the total human microbiota, which has been shown in recent years to play a crucial role in the health of the human body (1). Its content consists of more than 2,000 bacterial strains, of which 90% are represented by strains of Bacteroidetes and Firmicutes (1). The gut microbiota begins to form before birth. Several studies have confirmed the presence of specific strains of bacteria in the meconium (2). There is a relationship between the oral microbiota of the mother and the placental microbiota (3). Therefore, for example, women with heavy periodontitis have a higher risk of adverse pregnancy outcomes, such as preterm birth and low birth weight (3).
The method of birth also affects the development and composition of the gut microbiota (2). With a cesarean section, there is no natural delivery of the vaginal and intestinal microbiota from the mother. The gut microbiome of these newborns differs in composition; instead of the genera Bifidobacterium and Lactobacillus, there is a significant proportion of the phylum Proteobacteria (4). As a result, babies born in this way take several months to acquire a normal gut microbiome. Furthermore, children born by cesarean section are much more likely to develop allergies, autoimmune diseases, asthma, and a generally poorer resistance of the human body to pathogens (5).
Several essential functions have been assigned to the gut microbiome (6). These functions include fermentation of microbiota-accessible carbohydrates into absorbable metabolites, formation of signaling molecules, protection against pathogens, the strengthening of the intestinal barrier, and production of vitamins (7–11). Most of these functions are closely connected to human physiology. For example, short fatty acids production (SCFA) is the main source of energy for intestinal epithelial cells and can make up as much as 6–10% of daily calorie intake (7). Furthermore, it can also reduce the occurrence of fat in the blood and energy storage in the adipose tissue through activation of AMPK (AMPK – activated protein kinase) which is involved in the regulation of fatty acids (12). It can also decrease inflammatory reactions in the body and has an anti-cancerous effect, and can thereby contribute to the suppression of cancer cells (13,14).
The role played by physical activity (PA) in human health has been known for a long time. There are countless benefits of PA, for example reducing the risk of chronic diseases, helping to manage weight, improving mental health, strengthening muscle and bones, improving sleep quality, lowering blood pressure, and maintaining blood sugar level. There is a difference between the benefits of each type of physical activity. Resistance or strength training, which is the main subject of this systematic review, has the following benefits: reversing muscle loss, recharging resting metabolism, reducing body fat, facilitating physical function, resisting type 2 diabetes, improving cardiovascular health (resting blood pressure, blood lipid profiles, vascular condition), increasing bone mineral density, enhancing mental health and reversing aging factors (15–23).
The relationship between the gut microbiota and physical activity was first examined in animal samples and later in humans. These studies highlighted the ability of PA to modify the composition of the gut microbiome(1,24). According to current sources, regular physical activity increases the diversity of the intestinal microbiota and the number of beneficial bacteria, particularly those that produce SCFA. Physical activity also leads to better intestinal blood flow and improved intestinal motility, thereby accelerating digestion passage through the intestinal tract and thereby serving to prevent constipation and associated problems (25). There have already been several systematic reviews focusing on the effect of exercise and physical activity on the gut microbiome, though none have focused exclusively on the effect of resistance training or strength training (26–31). Of the published reviews, the systematic review by Ramos et al. (2022) focused on the effects of PA on the gut microbiome of older adults, Bonomini – Gnutzmann et al. (2022) summarized the effect of intensity and duration on gut microbiota in humans, Dorelli et al. (2021) described the influence of PA on gut microbiota composition independently of diet, Cataldi et al. (2022) devoted their attention to the difference between the effect of PA on the gut microbiome in healthy and unhealthy subjects, and Zheng et al. (2022) collected knowledge about the influence of physical exercise on obesity and type 2 diabetes. There have also been other reviews that focused on the overall effect of PA and that either used only specific study designs or also included animal studies (26,30).
The main aim of this rapid review is to summarize the results of human studies that examine the effect of resistance/strength training on the gut microbiome of a healthy or unhealthy population to understand whether resistance training has the potential to positively modulate the gut microbiome.