A quantitative approach for assessing significant improvements in elite sprint performance: has IGF-1 entered the arena?

Association of rs35767 polymorphism in the IGF1 gene with athletic performance in power and endurance sports: A meta-analysis

BACKGROUND

Sport performance is a multifactorial phenotype dependent on the interaction of multiple genetic and non-genetic factors. More than 200 polymorphisms have been associated with athletic performance. The single nucleotide polymorphism (SNP) rs35767, located in the regulatory region of the IGF1 gene, influences its expression and has been associated with sports-related phenotypes. We aimed to perform a meta-analysis to evaluate the association between the rs35767 polymorphism of the IGF1 gene and athletic performance in power and endurance sports.

METHODS

Literature has been retrieved from PubMed, Web of Science, Scopus, Embase, and Sport Discus databases until October 2023. This study was designed according to the PRISMA statement. Different models were tested, and heterogeneity was evaluated.

RESULTS

Three studies were included in this meta-analysis. Statistically significant differences were highlighted for the frequency of the minor allele when comparing all athletes and controls (p < 0.001; OR = 1.74; 95 % CI = 1.26-2.40), endurance athletes and controls (p = 0.016; OR = 1.87; 95 % CI = 1.12-3.1) and power sport athletes and controls (p = 0.007; OR = 1.62; 95 % CI = 1.14-2.31). No statistically significant difference was found between the power and endurance groups. According to data analysis, the recessive model is the most suitable genetic model.

CONCLUSIONS

This metanalysis supports the role of the minor allele of the rs35767 polymorphism of the IGF1 gene as favoring an athlete's performance in endurance and power sports.

Insulin-Like Growth Factor-1 (IGF-1) and Its Monitoring in Medical Diagnostic and in Sports

Insulin-like growth factor-1 (IGF-1) is the principal mediator of growth hormone (GH), plays a crucial role in promoting cell growth and differentiation in childhood and continues to have an anabolic effect in adults. IGF-1 is part of a wide network of growth factors, receptors and binding proteins involved in mediating cellular proliferation, differentiation and apoptosis. Bioavailability of IGF-1 is affected by insulin-like growth factor binding proteins (IGFBPs) which bind IGF-1 in circulation with an affinity equal to or greater than that of the IGF-1 receptor (IGF-1R). The six IGFBPs serve as carrier proteins and bind approximately 98% of all circulating IGF-1. Other proteins known to bind IGF-1 include ten IGFBP-related proteins (IGFBP-rPs), albeit with lower affinities than the IGFBPs. IGF-1 expression levels vary in a number of clinical conditions suggesting it has the potential to provide crucial information as to the state of an individual’s health. IGF-1 is also a popular doping agent in sport and has featured in many high-profile doping cases in recent years. However, the existence of IGFBPs significantly reduces the levels of immunoreactive IGF-1 in samples, requiring multiple pre-treatment steps that reduce reproducibility and complicates interpretation of IGF-1 assay results. Here we provide an overview of the IGF network of growth factors, their receptors and the entirety of the extended family of IGFBPs, IGFBP-rPs, E peptides as well as recombinant IGF-1 and their derivatives. We also discuss issues related to the detection and quantification of bioavailable IGF-1.

An improvement index to quantify the evolution of performance in field events

The mean of the top 25 performances in 8 men's and 5 women's field events since the 1890s showed that performances increased dramatically after the Second World War II and subsequently plateaued during the late twentieth century. A performance improvement index, developed on the basis of work done, was set to 100% in 1948. The underlying rise found in all events was modelled using an exponential function with a superposition of steps and linear changes to account for the introduction of rule changes, drugs testing and the introduction of new technologies. The performance improvement index in throwing events increased to 140.9% compared with 125.8% in jumping events, and women's performance improvement always exceeded that of men's. Around half of all events were shown to have reached 99.9% of their predicted limit with a majority reaching it within the next 25 years. It was concluded that performance will only change in the future if an intervention takes place: this could be the emergence of a new technology, a rule change or a new athlete population.

An improvement index to quantify the evolution of performance in running

Improvements in track and field sports have been attributed to factors such as population increase, drugs and new technologies, but previous research has found it difficult to distinguish the contributions from specific influences. Here it is shown how this is possible by means of a performance improvement index based on useful work done combined with modelling of the annual top 25 performances. The index was set to 100 in 1948 and showed that, by 2012, it had increased in running events to between 110.5 and 146.7 (men's 100 m and marathon). Underlying global effects accounted for the majority of all improvements (16.2 to 46.7) with smaller influences attributable to an influx of African runners (3.6 to 9.3), and a 4-year oscillation that arose from staging of the Olympic Games (±0.2 to ±0.6). Performance decreased with the introduction of compulsory random drug testing (-0.9 to -3.9) the World Anti-Doping Agency (WADA; -0.5 to -2.5) and fully automated timing (-0.6 to -2.5). Changes in elite sporting performance since the 1890s are attributable to societal changes caused by the industrial revolution and globalisation superimposed on millennia of human evolution.