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BACKGROUND: Extensive evidence supports the benefits of high-intensity intermittent training (HIIT) for endurance athletes. Additionally, the importance of neuromuscular characteristics and body composition in determining running economy and, thereby running performance, have been widely documented. Previous studies performing HIIT interventions have focused on single sports, such as swimming, running or cycling, but not on multiple-event such as triathlon. AIM: This study aimed to determine the effect of a 5-week HIIT-based running programme on body composition and muscular performance parameters in triathletes. METHODS: Thirteen triathletes were matched into two groups, experimental group (EG) and control group (CG). The CG was asked to maintain their training routines, whilst the EG modified their running plans (HIIT-based) but maintained their swimming and cycling routines. Body composition, vertical jump, stretch-shortening cycle utilization (SSC) and sprint ability were performed before (pretest) and after (posttest) the intervention period. RESULTS: No significant differences between groups were found at pretest. At posttest, the EG obtained higher values in countermovement jump (p = 0.005, ES > 0.7) and SSC (p = 0.017, ES > 0.7), with lower times (p = 0.001, ES > 0.7) in sprint. Body composition parameters remained unchanged in both groups (p ≽ 0.05, ES < 0.4). CONCLUSION: These preliminary results show that a HIIT-based running plan may induce improvements superior to the plan performed by the CG, in jumping, sprinting ability and SSC, without impairing body composition parameters. Thus, this study highlights the effectiveness of HIIT-based training programme for improving explosive muscular power and the rebound capabilities of the athletes. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the changes in body mass and myoglobinuria concentration in recreational runners during a marathon in a warm environment, and the relation of these changes to muscle fatigue. We recruited 138 amateur runners (114 men and 24 women) for the study. Before the race, leg muscle power output was measured during a countermovement jump on a force platform, body weight was measured, and a urine sample was obtained. Within 3 min of race completion (28 °C; 46% relative humidity), the runners repeated the countermovement jump, body weight was measured again, and a second urine sample was obtained. Myoglobin concentration was determined in the urine samples. After the race, mean body mass reduction was 2.2% ± 1.2%. Fifty-five runners (40% of the total) reduced their body mass by less than 2%, and 10 runners (7.2%) reduced their body mass by more than 4%. Only 3 runners increased their body mass after the marathon. Mean leg muscle power reduction was 16% ± 10%. Twenty-four runners reduced their muscle power by over 30%. No myoglobin was detected in the prerace urine specimens, whereas postrace urinary myoglobin concentration increased to 3.5 ± 9.5 μg·mL-1 ( p < 0.05). Muscle power change after the marathon significantly correlated with postrace urine myoglobin concentration ( r = -0.55; p < 0.001), but not with body mass change ( r = -0.08; p = 0.35). After a marathon in a warm environment, interindividual variability in body mass change was high, but only 7% of the runners reduced their body mass by more than 4%. The correlation between myoglobinuria and muscle power change suggests that muscle fatigue is associated with muscle breakdown. [ABSTRACT FROM AUTHOR]

Abstract: There is increasing evidence regarding the association between mitochondrial DNA (mtDNA) and aerobic capacity; however, whether mtDNA haplogroups are associated with the status of being an elite endurance athlete is more controversial. We compared the frequency distribution of mtDNA haplogroups among the following groups of Spanish (Caucasian) men: 102 elite endurance athletes (professional road cyclists, endurance runners), 51 elite power athletes (jumpers, throwers and sprinters), and 478 non-athletic controls. We observed a significant difference between endurance athletes and controls (Fisher exact test=17.89, P =0.015; Bonferroni''s significant threshold=0.017), yet not between power athletes and controls (Fisher exact test=47.99, P =0.381) or between endurance and power athletes (Fisher exact test=5.53, P =0.597). We observed that the V haplogroup was overrepresented in endurance athletes (15.7%) compared with controls (7.5%) (odds ratio: 2.284; 95% confidence interval: 1.237, 4.322). In conclusion, our findings overall support the idea that mtDNA variations could be among the numerous contributors to the status of being an elite endurance athlete, whereas no association was found with elite power athletic status. [Copyright &y& Elsevier]

Background: The genetic profile that is needed to define an endurance athlete has been studied during recent years. The main objective of this work is to approach for the first time the study of genetic variants in liver-metabolizing genes and their role in endurance performance by comparing the allelic and genotypic frequencies in elite endurance athletes to the non-athlete population. Methods: Genotypic and allelic frequencies were determined in 123 elite endurance athletes (75 professional road cyclists and 48 endurance elite runners) and 122 male non-athlete subjects (sedentary). Genotyping of cytochrome P450 family 2 subfamily D member 6 (CYP2D6 rs3892097), glutathione-S transferase mu isoform 1 (GSTM1), glutathione S-transferase pi (GSTP rs1695) and glutathione S-transferase theta (GSTT) genes was performed by polymerase chain reaction (PCR). The combination of the polymorphisms for the "optimal" polygenic profile has been quantified using the genotype score (GS). Results: Statistical differences were found in the genetic distributions between elite endurance athletes and non-athletes in CYP2D6 (p < 0.001) and GSTT (p = 0.014) genes. The binary logistic regression model showed a favourable OR (odds ratio) of being an elite endurance runner against a professional road cyclist (OR: 2.403, 95% CI: 1.213–4.760 (p = 0.002)) in the polymorphisms studied. Conclusions: Genotypic distribution of liver-metabolizing genes in elite endurance athletes is different to non-athlete subjects, with a favourable gene profile in elite endurance athletes in terms of detoxification capacity. [ABSTRACT FROM AUTHOR]