Purpose To examine whether two consecutive soccer matches would affect skin temperature (t _sk) measured via infrared thermography (IRT) in under-20 (U-20) soccer athletes, as well as verify whether the t _sk changes would be different between regions of interest. Methods A cross sectional study. Ten under-20 soccer athletes [age 19.0 ± 1.0 years; height 181.3 ± 6.6 cm; body fat percentage (BF%) 9.0 ± 1.8%, body surface area 1.9 m² and \(\dot{V}\)O_2max 56.4 ± 3.2 ml min⁻¹ kg⁻¹]. Skin thermal responses obtained by IRT and creatine kinase concentration (CK) were evaluated in response to two soccer matches with 3 days of recovery between each match. Results The t _sk increased (≅1.0 °C) 24 h after the first match in all studied regions of interest (ROIs), returning to near pre-match values 48 h after the first match. However, after playing the second match, the t _sk increased even more (≅1.5 °C) 24 h after in all the considered ROIs, not returning to pre-match values 48 h after. Regarding CK analysis, its course during the experiment was similar to t _sk, with high values 24 h after (first match 763.8 ± 294.5 U/L; second match 784.1 ± 298.8 U/L) and recovering 48 h after (first match 526.4 ± 289.7 U/L; second match 672.2 ± 285.0 U/L) both matches. However, when the two matches are compared, CK showed a higher value 48 h after the second match in comparison to first match (P = 0.002). The t _sk and CK were moderately correlated in all ROIs analyzed, with higher correlation in the anterior right leg (r = 0.425) and anterior left leg (r = 0.428). Conclusion The t _sk of lower limbs as well as CK markedly change in response to two consecutive matches separated by an interval of 3 days. There is indication of the highest inflammatory response after the second match, which was preceded by just a 3-day recovery. In addition, a general increase was obtained in thighs and legs in anterior and posterior views.

The purpose of this study is to analyze the relationship between lower limbs skin temperature (Tsk) recorded by infrared thermography and creatine kinase (CK) response following an official soccer game. A professional soccer player, from the first division Brazilian League, defender, 27 years and 183 cm of height was analyzed. Measures of Tsk with a thermal camera and blood CK concentrations were obtained 24 hr before (24H-PRE), 24 (24H-POST) and 48 hr (48H-POST) after an official match. The results showed that CK values were 193 U/L 24 hr before, rising to 1,083 U/L 24 hr after the game and 414 U/L 48 hr after the game. Anterior thigh Tsk was 31.5°C, 33.8°C, and 31.8°C in the moments 24H-PRE, 24H-POST, and 48H-POST, respectively. Similarly, anterior leg presented temperature of 31.2°C, 33.3°C, and 31.5°C at the same moments. Qualitative analysis of the thermograms showed that whole lower limbs are much warmer 24 hr after the match and certain areas as the right anterior thigh, the left anterior leg, both anterior ankles, and both posterior thighs have not fully recovered their initial Tsk 48 hr after the match. The results of this study indicate that participation in a professional soccer match can lead to significant increases in Tsk values measured by IRT 24 hr after the match. Considering this variable as an indicator of muscular damage, it could help in the process of training control, being part of an injury prevention program in professional soccer clubs.

Classically, genetic association studies have attempted to assess genetic polymorphisms related to human physiology and physical performance. However, the heterogeneity of some findings drives the research to replicate, validate, and confirmation as essential aspects for ensuring their applicability in sports sciences. Genetic distance matrix and molecular variance analyses may offer an alternative approach to comparing athletes’ genomes with those from public databases. Thus, we performed a complete sequencing of 44 genomes from male Brazilian first-division soccer players under 20 years of age (U20_BFDSC). The performance-related SNP genotypes were obtained from players and from the “1000 Genomes” database (European, African, American, East Asian, and South Asian). Surprisingly, U20_BFDSC performance-related genotypes had significantly larger F_ST levels (p < 0.00001) than African populations, although studies using ancestry markers have shown an important similarity between Brazilian and African populations (12–24%). U20_BFDSC were genetically similar to professional athletes, showing the intense genetic selection pressure likely to occur before this maturation stage. Our study highlighted that performance-related genes might undergo selective pressure due to physical performance and environmental, cognitive, and sociocultural factors. This replicative study suggests that molecular variance and Wright’s statistics can yield novel conclusions in exercise science.

Genetic factors demonstrate influence on the components of athletic performance, but also on the activation and resolution of inflammation, muscle tissue immunity and other phenotypes. Titin (TTN) is a giant sarcomere protein that plays an essential role in muscle contraction with actin and myosin filaments. Its polymorphism may contribute to the inter-individual variation in the structural and functional properties of the muscle and tendon and its response to mechanical load, which may imply susceptibility to muscle injury. The identification of genes that may influence the levels of molecules involved in the sarcomeric structure can help to elucidate the factors and mechanisms related to muscle damage and consequent inflammatory process. The aim of the present study was to investigate the association of a TTN polymorphism, TTN-AS1 (RS1001238), with inflammation-related phenotypes in soccer players after a training session with predominance of eccentric actions. The sample consisted of 47 under-20 men's soccer players belonging to clubs in the first division of Brazilian soccer. Blood samples were collected before, 24, and 48 hours after the training session to evaluate the inflammatory responses (hematological neutrophil analysis, high sensitivity quantitative protein (CRP), tumor necrosis factor (TNFα)), muscle damage (creatine kinase (CK)), and insulin-like growth factor 1 (IGF-1). It was observed that individuals with the CC genotype for the TTN-AS1 Polymorphism (RS1001238) showed greater inflammatory responses (p<0.01) in relation to the TT and TC genotypes, with greater damage verified by CK (p<0.01) concentrations, TTN-AS1 (RS1001238) phenotypes and its possible structural alterations in skeletal striated muscle sarcomeres.

The aim of the study was to evaluate the responses of insulin-like growth factor 1 (IGF-1), C-reactive protein (CRP), IGF-1/CRP ratio, and skin temperature (Tsk) of the lower limbs (LL) of under-20 elite soccer athletes to a non-contact team sport activity circuit throughout 48h. Thirty elite soccer athletes (19.0 ± 1.0 years, 74.3 ± 7.13 kg, 10.3 ± 2.2 %F, 178.1 ± 6.6 cm, 56.3 ± 3.1 mL.kg^-1.min^-1) were submitted to a team sport activity circuit with intermittent exercises, jumps, direction shifts, accelerations and decelerations. Plasma concentrations of IGF-1 and CRP were evaluated pre-training session (baseline), and immediately after, and at 3, 24 and 48h following exercise. While the Tsk of the LL was evaluated at baseline, and at 24 and 48h following exercise. Plasma IGF-1 concentrations were greater immediately after, 24 and 48h after the circuit compared to 3h (p< 0.05; ES= 0.66, 0.72 and 0.70, respectively). CRP values did not change throughout the study (p> 0.05). When verifying the IGF-1/CRP ratio, the values at 3h after the activity circuit were lower than those presented in baseline, and immediately after, 24 and 48h after the exercises (p< 0.05; ES= 0.53, 0.65, 0.56 and 0.57, respectively). The hot and neutral zones increased the number of pixels at 24 and 48h after the activity circuit, while the cold zone showed an opposite behavior (p< 0.05). Changes in the values of blood biomarkers and Tsk of the LL suggest that there is possibly an active tissue repair process throughout 48h following exercise.