In the midst of clustering, we recognized 4 primary teams, from which we highlighted probably the most related 18 subjects.
We current the 18 subjects based on the next 4 facets: the variety of publications within the cluster (the dimensions of the subject), the distribution of the publications primarily based on publication date, the quotation influence of the publications, and the evaluation of the journal rank of publications inside every matter.
The 18 subjects are the next:
Soccer and physiology
Muscle physiology: alkalosis and acidosis
Muscle mass acquire and dietary supplementation
Fluid stability and hydration
Dietary consumption and diet data
Willpower of vitality want of athletes
Bone well being, feminine athlete triad
Physique weight administration
Dietary Methods and human skeletal muscle
Dietary supplementation of nitrates
Oxidative stress and dietary complement use
Dietary complement use and doping
Oxidative stress, irritation, and dietary antioxidants
Train adaptation and dietary methods
Scientometric traits of subjects
The scale distribution of subjects
Based mostly on absolutely the and relative measurement of the subjects, which might be primarily based on the variety of publications belonging to a cluster, we will get an perception into the importance of the explored subjects and analysis traits in sport diet science. These information are displayed in Fig. 3., which, moreover the variety of publications in every cluster, additionally reveals their composition by way of the core publications recognized by means of the focused search in addition to of the publications citing, and people cited by the core pattern. When it comes to weight (measurement), probably the most dominant matter, with ca. 300 publications, is ‘muscle energy enhancement and dietary supplementation’, adopted by subjects with about 200–250 publications: ‘carbohydrate metabolism’, ‘oxidative stress and dietary complement use’, ‘train adaptation and dietary methods’, ‘dietary supplementation of nitrates’, ‘dietary methods and human skeletal muscle’. This group is intently adopted by the subject of ‘bone well being, feminine athlete triad’, ‘dietary consumption and diet data’, and ‘dedication of vitality want of athletes’, with about 200 publications. The group with 100–150 publications is led by the subjects of ‘fluid stability and hydration’, and ‘physique weight administration’, furthermore, right here belong the themes of ‘soccer and physiology’, additionally the ‘hydration technique’, in addition to ‘dietary complement use and doping’. Within the 50–100 vary, the dominant subjects with nearly 100 publications are ‘muscle physiology: alkalosis and acidosis’, ‘oxidative stress, irritation and dietary antioxidants’, additionally right here belong the smaller however well-defined subjects of ‘intestine microbiota’ and ‘celiac illness’. The total measurement of the subjects tremendously correlates with their position and significance within the core pattern; that’s, measurement rating additionally displays the extent to which the cluster is of ‘sport physiological’ nature.
Chronological distribution of subjects
The distribution by publication date of the publications belonging to the recognized subjects, or, to place it one other approach, the chronological distribution of every cluster facilitates the evaluation of the traits and relevance of every matter, of their ‘standard’ or ‘winding down’ nature. The distribution of the dimensions of the subjects is summarized in Fig. 4., which reveals the variety of paperwork belonging to every matter ranging from 2010. Based mostly on this, the development graphs within the desk present an summary of the chronological dynamics of the subjects. The development graphs attest that every matter reveals a rising tendency (that’s, increasingly more articles appeared on the given matter up to now decade), every cluster is at its most measurement within the final examined yr (2018). The variations between the subjects seem within the traits and sample of the rise. In keeping with the latter, with a bit of simplification, we observe two forms of enhance: (1) the subject will increase steadily from the start or center of the examined decade, (2) after a relative ‘stagnation’, the subject reveals a rising slope in the previous couple of years. Sort (1), a gradual enhance is probably the most attribute of the subjects ‘muscle physiology: alkalosis and acidosis’, ‘dietary methods and human skeletal muscle’, ‘train adaptation and dietary methods’. Sort (2), sudden enhance with a extra average rising slope, unfold over the past 4-5 years, seems in relation with the subjects ‘soccer and physiology’, ‘vitality consumption and diet data’, ‘dietary methods and human skeletal muscle’, ‘fluid stability and hydration’, ‘hydration technique’, ‘oxidative stress and dietary complement use’, ‘dietary complement use and doping’, ‘oxidative stress, irritation and dietary antioxidants’. Within the case of subjects with a Sort (2) the slope is rising and usually peaking within the final 2 years, these are the next: ‘muscle energy enhancement and dietary supplementation’, ‘dedication of vitality want of athletes’, ‘physique weight administration’, ‘intestine microbiota’, and ‘celiac illness’. A ‘distinctive’ cluster, with a considerably completely different sample from the 2 primary varieties is the ‘carbohydrate metabolism’, which, together with some fluctuations, reveals a gradual output within the matter (additionally with a slight enhance); one other is ‘bone well being and feminine athlete triad’, which additionally reveals a gradual output with a rising slope within the final examined yr.
Quotation influence of subjects and journal ranks
Aside from chronological traits, the relevance and scientific significance of subjects may be investigated by means of using the next two teams of scientometric indicators: (1) the quotation measures (of the publications) of particular person subjects, and (2) the status or rank of publication venues, i.e., journals. Quotation measures present details about the scientific influence exerted by publications inside a subject, thought-about as a basic proxy to the relevance of subjects for sport diet science.
As an alternative of the uncooked quotation quantity, correcting for the field- and age-related variations, publications are characterised by their place within the quotation distribution inside the specific analysis subject, i.e. with the quotation percentile. The clusters with the most important influence are these whose common, that’s, the attribute worth of the related articles is located closest to 100. These with a median above the worth of 75 may be thought-about to have a excessive basic quotation influence (they belong to probably the most cited, 25%, quotation quartile). Based mostly on this, virtually all of the recognized clusters fall into the excessive quotation measure vary, each by way of their median and of the bulk (minimal 50%) of their publications. The subjects with the most important influence are the ‘dietary methods and human skeletal muscle’ and ‘dietary supplementation of nitrates’. A equally excessive composite influence is proven by the subjects of ‘soccer and physiology’, ‘carbohydrate metabolism’, ‘bone well being and feminine athlete triad’, ‘physique weight administration’, and ‘intestine microbiota’ (Fig. 5).
The rank of publications, on this case, refers back to the rank and recognition of the publishing journals, with the latter representing, by way of the subjects, the standard of information transferred in them. To explain the rank and the standard of the data content material of subjects, we utilized the quotation quartile system. The premise of the strategy is the classification of publications into 4 high quality courses based on the rank of the publishing journal. The so-called Q1 journals belong to the higher 25% of the journal rank of the sector, Q2 journals belong to the higher 25–50% quartile, Q3 journals are within the decrease 25–50%, and This autumn, within the backside 25%. Determine 6. reveals the distribution of the articles of the recognized clusters among the many 4 courses for every theme. On this case, additionally, we will state that the majority clusters embrace publications of top quality, inasmuch as on common, 50% of their publications are ranked Q1, and the vast majority of the remainder of the publications belong to Q2, which can be thought-about a passable high quality rank. ‘Carbohydrate metabolism’, ‘dietary methods and human skeletal muscle’, ‘dietary supplementation of nitrates’ stand out (Fig. 6).
Within the subsequent step of our methodological course of, we utilized the scientometric evaluation of subjects, for which we chosen the 4 most vital subjects and offered their inner construction by way of key thematic relations primarily based on our textual content mining and core doc methodologies. We illustrated the conceptual community of subjects with a dendrogram, and we analyzed the 4 subjects primarily based on their interconnections from the facets of sport diet, sport physiology, sort of sport, dietary dietary supplements, and efficiency diagnostics. The gathering of the 18 subjects and their core papers are in Further file 1. Utilizing a complicated bibliometric methodology, we obtained the so-called core papers for every analysis matter, probably the most consultant publications within the cluster (see Further file 1).
Description of the dietary methods and human skeletal muscle cluster
This matter focuses on the connection between sport efficiency and the metabolic pathways of skeletal muscle cells. Its most frequent problem is the position of PGC-1 alpha transcriptional regulation particularly within the relation to mitochondrial biogenesis, citrate synthesis, endurance efficiency, phosphocreatine because the creatine substrate of efficiency enhancement, the relation of insulin, free fatty acids and fatigue, protein and carbohydrates (initially fructose), and likewise in relation to vitality expenditure and regeneration. Relying on the kind of the examined sport, endurance coaching stands out, however high-intensity interval coaching can be current with nearly the identical frequency. Of the organic parts, the position of P38 MAPK protein kinase is price emphasizing (Fig. 7).
Description of the dietary supplementation of nitrates matter
The advanced (sport-) physiological focus of the subject is on the relation community of blood circulation, oxidative metabolism and nitrogen metabolism and supplementation (in relation to sport actions). Its main subjects are oxygen consumption (associated to the idea of effectivity), fatigue, inorganic nitrate substrate associated to vascular operate, the stimulus-muscle contraction connection, vegetarianism, the enzyme that produces nitrogen oxide substrate, the relation community of hypertension and vasodilatation, irritation and beta-alanine, and bloodstream. Relying on the kind of bodily exercise, this matter is characterised by endurance coaching, particularly, associated to oxidative stress and its biomarkers. The idea of diving response additionally emerged primarily associated to oxygen uptake and consumption and extra barely to respiratory management. Inside additional substrata, sodium nitrite and with decrease frequency, creatine-nitrate appeared. Concerning indices, using the VO2 efficiency indicator was related (Fig. 8).
Description of the carbohydrate metabolism matter
From a sport physiological viewpoint, this matter additionally revolves across the enchancment of skeletal muscle operate, primarily within the relation to carbohydrate metabolism. Its pivotal ideas and points are lipid oxidation throughout train metabolism processes, nitrogen stability (particularly after consuming), lean physique mass (enhance), cardio capability associated largely to fatigue and endurance coaching, glycemic index, muscle glycogen, and endurance coaching (and carbohydrate absorption). The latter is attribute of the kind of the examined sport and within the phrases of department of sport, biking (timed coaching) and working emerged. Within the case of the examined substrates, dietary dietary supplements and biologically energetic parts, the position of lipid oxidation (timed biking), and – much less incessantly – catecholamine (working), sport drinks (biking) and fructose (endurance coaching), and creatine kinase emerged (Fig. 9).
Description of the muscle mass acquire and dietary supplementation matter
The central subjects of this cluster are the elements of muscle mass acquire and strengthening. An important questions of those subjects – that the research give attention to – are the affiliation between muscle restoration and accidents, muscle energy, anaerobe threshold, anaerobe capability, cardiorespiratory endurance, and lean physique mass. Categorized by the kind of sport train the 2 main subjects are resistance train and high-intensity train associated largely to cardiorespiratory endurance. The subject of dietary complement use can be vital on this cluster. Proteins are a very powerful and nitrogen oxides, nitrates and creatine are additionally appreciable among the many research on substrates and dietary dietary supplements that play an essential position in muscle mass acquire and efficiency enhancement. Carnosine and beta-alanine have a comparatively smaller significance on this matter. On this cluster, electromyography is a frequent analysis methodology (Fig. 10).
Vitamins and substrates that appeared within the clusters
Among the many macronutrients, proteins and carbohydrates appeared probably the most incessantly within the subjects. These two vitamins had been studied based on their basic position in diet and likewise as ergogenic vitamins in sport diet. The position of proteins and amino acids had been assessed within the ‘muscle mass acquire and dietary supplementation’ and the ‘oxidative stress, irritation, and dietary antioxidants’ clusters. Within the carbohydrate metabolism cluster – extra particularly – glucose performs a serious position within the ‘soccer and physiology’ and fructose within the ‘dietary methods and human skeletal muscle’ clusters. Concerning additional vitamins and substrates, beta-alanine, creatine, caffeine, nitrates, and sodium seems incessantly within the analysed publications. The impact of beta-alanine was studied within the ‘muscle physiology: alkalosis and acidosis’, ‘train adaptation and dietary methods’ and the ‘muscle mass acquire and dietary supplementation’ clusters. The position of nitrates was assessed within the ‘dietary supplementation of nitrates’ and within the ‘oxidative stress and dietary complement use’ clusters. In addition to the nitrates, caffeine was additionally analysed in these two latter clusters. Moreover, the subject on the impact of caffeine had a serious position within the ‘dedication of vitality want of athletes’ and ‘muscle physiology: alkalosis and acidosis’ clusters. The impact of creatine was studied within the ‘physique weight administration’, ‘muscle mass acquire and dietary supplementation’ clusters. The pre- and probiotics had been solely assessed within the ‘intestine microbiota’ cluster. The position of omega-3 fatty acids was analysed as stress and inflammatory marker within the ‘oxidative stress and dietary complement use’ cluster (Desk 1).