Cross-Talk Between Physical Activity, Diet, Gut Microbiota and Skeletal Muscle ^†

Abstract

Dietary nutrients are crucial for human health and the survival of gut microbes. Diet plays a central role in gut microbiota, as microbes rely on ingested nutrients for biological functions. Research highlights the connection between gut microbiota and exercise. Moderate and intense exercise are common in endurance training. Studies suggest gut microbiota may influence athlete health and performance. Athletes should consider dietary strategies like protein supplements, carbohydrate loading, probiotics, and prebiotics. The diverse gut microbiome of elite athletes produces key metabolites like short-chain fatty acids. A gut–muscle axis may exist, influencing muscle quality and gut biodiversity. This work summarizes current knowledge on diet, exercise, gut microbiota, and skeletal muscle.

1. Introduction

It is currently well established that various microbial communities coexist within the human body, including bacteria, archaea, fungi, and even viruses. Most of these microorganisms reside in the human gastrointestinal tract and are collectively referred to as the gut microbiota [1]. The composition of the gut bacteria can be influenced by various factors, including genetics, age, environment, diet, and lifestyle [2]. Remarkably, diet is regarded as one of the most important factors affecting the gut microbiota, with a complex and bidirectional relationship between both of them [3]. The time it takes to complete a given distance is a common definition of performance in endurance exercises, so athletes attempt to maximize their average speed during the defined distance to complete, but human body limitations always limit the performance [4]. For many years, researchers have been trying to identify the physiological factors limiting performance in endurance exercises and ways to overcome them [4]. Exercise performance is affected by the depletion of energy substrates in the body, the accumulation of metabolites such as blood lactate and urea nitrogen, skeletal muscle metabolism, and neurotransmitter-mediated changes in motivation to exercise in the brain [5]. On the other hand, raising the training load, for example, by increasing the amount of time spent exercising or intensity of physical activity, could have a detrimental impact on the digestive tract and result in symptoms including nausea, vomiting, colic, flatulence, or stomach pain diarrhea. Given this, a few typical physiological exercise-related reactions that compromise the integrity and functionality of the gastrointestinal (GI) tract include “gastrointestinal syndrome induced by exercise” [6]. It is estimated that 70% of athletes have this illness, occurring between 1.5 and 3 times more frequently in competitive athletes than in amateur ones [6].

This work aimed to understand the relationship between gut microbiota, diet, physical exercise, and muscle.

2. Materials and Methods

We used the Google Scholar, Scopus, PubMed, Web of Science, and Science Direct databases to identify scientific papers within the subject of this overview. We used the following keywords: “Diet and Gut microbiota”, “Physical activity and microbial diversity”, “Gut-muscle axis”, “Skeletal muscle and microflora”, and “Human”. The interconnection between the gut microbiota, diet, physical activity, and muscle was the main topic of all 13 included papers.

3. Results and Discussion

The main findings identified in the reviewed papers are given in Table 1.

Table 1. Summary of the main studies identified within the subject of this paper.

Diet	Study	Population	Duration	Physical Activity	Effect on Muscle	Effect on Gut Microbiota	Reference
Gavage with E. rectale, Fructus Arctii extract, Agaricus blazei, polysaccharieds galactooligosaccharides, and curcumin	Animal	50 male and ICR mice, pathogen-free, weighing 18–22 g, were used.	Dietary intervention: 4 weeks. Physical activity (weightless swimming): daily for 2 weeks.	Exercise performance was assessed through exhaustive swimming with 5% tail loading.	↑ muscle glycogen, endurance, and strength in groups receiving E. rectale and Curcumin, Fructus Arctii, galactooligosaccharides	The abundance of bacteria like E. rectale and Veillonella was influenced by different dietary interventions	Wang et al., 2024 [5]
High-protein diets (HPDs)	Human	Athletes: moderate to high-intensity exercises. Older Adults: typically over 70.	Athletes: Probiotic supplementation for 14 weeks. Older Adults: 10-week HPD (1.3 g/kg/day)	Athletes: Regular, intense, or prolonged exercise with strength training. Older Adults: Physical deterioration affects function.	Athletes: ↑ muscle mass and improved recovery; Older Adults: enhanced strength and mass	Promote beneficial bacteria (Bifidobacterium, Akkermansia); aging ↓ microbiota diversity, leading to protein synthesis disorders in skeletal muscle	Cai et al., 2021 [7]
Not specified	Human	32 previously sedentary normal-weight or obese adults.	6 weeks (+ 6-week washout period).	Endurance exercise.	Not specified	↑ Faecalibacterium and ↓ Bacteroides in normal-weight subjects; opposite trend in obese individuals	Cella et al., 2021 [8]
Polyphenol-rich foods or supplements (e.g., pomegranate polyphenols).	Human	Athletes, or individuals engaged in physical activity.	No specific study duration mentioned.	Involved in sports practices.	Polyphenols may help ↓ muscle fatigue and weakness by ↓ oxidative stress, inflammation due to their antioxidant properties	Polyphenols promote the ↑ of Lactobacilli, Bifidobacteria, Akkermansia, and Faecalibacterium prausnitzii	Zeppa et al., 2019 [9]
Mediterranean diet (MD): plant-rich diets with carbohydrates +vegetable/fruit intake.	Human	Healthy adults, patients with IBD, cyclists, runners.	Exercise programs of at least 12 weeks.	Aerobic exercise + resistance training, with moderate to vigorous intensity.	Not specified	↑ Prevotella, Faecalibacterium, and overall microbial diversity; changes linked to training duration and intensity	Bonomini- Gnutzmann et al., 2022 [10]
High-fat diet (HFD)	Animal	Rats	5 weeks.	Voluntary wheel running	Indirect improvement due to enhanced gut microbiota, better metabolic regulation	Modulated gut composition, ↑ butyrate production, changes in cecumsize.	Campaniello et al., 2022 [11]
No specific diet (with/without Supplementation of whey protein).	Human	Adults (participants, aged 18–40 years)	8 weeks.	Aerobic training + resistance training (3 times a week for 8 weeks)	Not specified	Increasing viral species: ↑ Lactococcus phage. ↑ TMAO (linked to inflammation and CVD).	Cronin et al., 2018 [12]
Standard AIN-93M diet. High-fat and high-fructose (HFF). Chia seed +oil.	Animal	48 male Wistar rats (aged 21–23 days at the start).	12 weeks.	Not specified	↓ HSP60 expression (only in chia seed short treatment) ↓ AMPK ↓ GPx	Not specified	Marineli et al., 2015 [13]

↑: increase; ↓: decrease; IBD: Inflammatory Bowel Diseases; ICR: Institute of Cancer Research; TMAO: Trimethylamine N-oxide; CVD: Cardiovascular Disease; HSP: Heat Shock Protein; AMPK: Energy Metabolism; GPx: Glutathione Peroxidase.

In Table 1, the authors studied the effect of the different types of diets, including the HFD, MD, and HPD, on gut microbiota and muscle performance, both during exercise and non-exercise conditions, with varying exercise intensities and durations. These outcomes strength the idea that both diet and exercise reinforce gut health, reducing inflammation and improving insulin resistance, key factors for balanced metabolic health. Diets rich in protein, polyphenols, and complex carbohydrates (e.g., Mediterranean diet) support better muscle performance by improving muscle recovery, strength, and endurance and reducing muscle fatigue. Conversely, imbalanced diets (e.g., the HFF diet) may disrupt this balance, leading to adverse effects: raising inflammation markers, disrupting metabolism, and deteriorating antioxidant defenses. These insights highlight the critical role of well-balanced nutrition in improving exercise performance and microbiota health.

4. Conclusions

Each healthy individual possesses distinct gut microbiota, and the composition of healthy gut microbiota varies from person to person. Diet significantly influences the variations in microbial composition regarding richness and diversity. Engaging in physical exercise at the levels recommended by the World Health Organization (WHO) enhances fitness and quality of life through various mechanisms, likely involving changes in gut microbiota. Through a variety of processes, the gut microbiota has a significant impact on the quality and function of skeletal muscle, for example, reduction in insulin resistance and enhancement of mitochondrial function as well as reduction in inflammation. However, existing research on the relationship between gut microbiota, diet, muscle, and physical activity is limited. Further studies are recommended for a deeper understanding.