The aim of this study was to investigate the prevalence of the ACTN3 rs1815739 polymorphism and to study its association with athletes’ level of competition and lower-extremity power.
Time-of-flight mass spectrometry (TOFMS) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) techniques were employed to identify the ACTN3 rs1815739 genotypes and allele frequencies in 108 elite sprinters and 206 untrained controls. Questionnaires were then used to assess subjects’ 100 m sprint, standing jump (SJ) and standing triple jump (STJ) personal best record.
(1) The RR, RX and XX genotype distribution of the ACTN3 rs1815739 polymorphism is 42.6%, 49.1%, 8.3%, respectively. R and X alleles frequency is 67.1% and 32.9%, respectively, which comply with Hardy Weinberg equilibrium (HWE) through Chi-square (χ 2) tests (χ 2 = 0.661; df = 2; P = 0.718). (2) Significant differences were found in R allele frequency between the elite sprinter group and controls. (3) The athletes’ 100 m sprint, SJ, and STJ personal best records were better in those with RR and RX than XX genotype. A significant association was observed between the R alleles and 100 m sprint, SJ, and STJ results of male and female athletes.
The present results indicate that ACTN3 rs1815739 polymorphism has a significant association with speed and lower-extremity power in sprint/power athletes.
Self-confidence is one of the most important conditions needed for athletes to succeed. The way in which the self-confidence of athletes may be improved is an eternal topic in training and competition. This study aimed to examine whether unconscious goal priming can improve athletes’ explicit and implicit self-confidence through three experiments. Experiment 1 was aimed at exploring the effect of unconscious goal priming on athletes’ self-confidence. For the purpose of this experiment, 120 athletes were randomly divided into a priming group and a control group. Experiment 2 was aimed at examining the training effect of unconscious goal priming on athletes’ self-confidence and for the purpose of this experiment 16 rhythmic gymnastics athletes were selected as subjects. Experiment 3 was aimed at checking the replication of the training effect of unconscious goal priming on athletes’ self-confidence employing 16 judo athletes as subjects. The results indicated that unconscious goal priming improved athletes’ explicit self-confidence but not implicit self-confidence, while unconscious goal priming intervention improved both athletes’ explicit and implicit self-confidence. These results provide an economical and convenient alternative for improving athletes’ self-confidence.
Ski mountaineering is held at moderate altitude and harsh atmospheric conditions. Acute hypoxia increases sympathetic activity. However, this specific autonomic modulation, combined with very-high-intensity exercise, has not been studied. We aimed to investigate the effects of a competitive micro-cycle on heart rate variability (HRV). Nine male (23.0 ± 1.5 years) and four female (23.5 ± 1.3 years) elite ski mountaineers participated in the Spanish Championships, composed by sprint, individual and vertical races. RR intervals were recorded every morning in supine (8 min) and orthostatic (6 min) positions before, during, and after the Championships. HRV time-domain, frequency-domain, and non-linear indices were calculated using 5-min windows. Total score of fatigue (TSF), session rate of perceived exertion (s-RPE), and individual racing performances were assessed. Lower supine mean RR in the vertical race evidenced HRV imbalance (P = 0.032), whereas decreased supine LF spectral power showed vagal tone recovery within a 24-h interval (P = 0.013). A parasympathetic rebound was also revealed by the mean RR 48 h after the vertical race (P = 0.017). Performance correlated positively with supine mean HR (P = 0.013), and inversely with the standing-supine difference of heart rate (HRor-su) (P = 0.005). TSF was related positively with overall performance (P = 0.015), and negatively with supine mean RR (P = 0.036). Intense exercise at moderate altitude exacerbates the physiological stress leading to parasympathetic withdrawal and increased sympathetic activity that can be restored after 24–48-h recovery. HRV analysis and perceptual measurements can be valuable in monitoring stress–recovery balance during multi-race events.
The aim of the present study was to investigate the effect of caffeine on vertical jumping height in rested condition and after a heavy strength training session. Six well-trained young males with experience in jump and strength training were included in this double-blinded, randomised study with cross-over design. Caffeine (3 mg/kg body weight) or placebo were ingested 45 min prior to the jump tests. Jumping was performed on a force platform and vertical jumping height was calculated. After a standardized warm up, participants performed jumping series consisting of three maximal jumps with 30 s rest between jumps followed by five maximal jumps with 7 s rest between jumps. The participants performed a heavy strength training of the leg muscles (leg press: 3 × 15 reps) and the jumping series was repeated immediately after (30 s), and after 5 min and 15 min recovery. Caffeine increased the maximal vertical counter movement jump height (P ≤ 0.05) and mean value of the 5-jump sequence prior to the strength training. Caffeine increased jump height by 2.2 cm ± 0.5 cm at the first jump. Blood lactate after the strength training increased to 6.97 ± 1.20 and 7.77 ± 0.54 mmol/L in PLA and CAF, respectively (P = 0.19). The jump height was reduced by 8 cm after the strength training. There were no differences in jump height after ingestion of caffeine or placebo immediately after the strength training session or in the recovery period, but blood lactate in the recovery period was higher in CAF compared to PLA (ANOVA; P < 0.05). Conclusion: Caffeine increased the vertical jump height in the resting state. However, after a maximal effort strength training session the positive effect of caffeine was no longer significant.
Improvements in D′ (the fatigability constant for running) subsequent to training interventions remain elusive. High-intensity interval training (HIIT) within the severe intensity domain for short durations (< 2-min) have been theorized to improve D′. The purpose of the present study was to assess this in a group of moderately trained individuals.
Eighteen participants completed graded exercise testing (GXT), 40-m sprint testing and a 3-min all-out test (3MT) for running to determine key mechanistic and physiological parameters. Participants were randomly assigned into one of two groups based on intensity prescription (G140% = 140% of critical speed [CS]), or time intervals (G90-s = 90-s) to complete a twice-weekly training intervention for 6-weeks followed by re-assessment.
No between-group differences were present either prior to or following the intervention. Substantial and meaningful improvements were detected during the post-intervention period for both groups for VO2max (G140%: + 7.60%; G90-s: + 11.67%), speed evoking VO2max (sVO2max; G140%: + 4.33%; G90-s: + 2.92%), gas exchange threshold (GET; G140%: + 12.02%; G90-s: + 20.52%), speed evoking GET (sGET; G140%: + 4.17%; G90-s: + 7.92%), CS (G140%: M = 0.62 m/s; G90-s: M = 0.46 m/s), D′ (G140%: M = − 56.34 m; G90-s: M = − 18.36 m), FI% (G140% M = − 6.75%; G90-s: M = − 4.38%) and maximal distance (G140%: M = 49.67 m; G90-s: M = 58.38 m).
The prescribed intensities and durations were insufficient to elicit improvements in D′. Improvements in D′ may be dependent on very short-duration intervals (i.e. < 60 to 90-s) at speeds exceeding 140% CS but below maximal sprint speed.
The aim of the study was to establish the optimum variable resistance (VR) intensity for loaded countermovement jump (LCMJ) to induce post-activation potentiation (PAP).
Eleven male athletes (age 23 ± 2.3 years, height 1.77 ± 0.05 m, body mass 73.7 ± 9.0 kg) attended one familiarization and four testing sessions. Subjects performed their own pre-competition warm up before performing two countermovement jumps (CMJ) for baseline measure. Subsequently, they performed 2 × 3 unloaded (UCMJ) or loaded CMJ (LCMJ) with one of the three VR intensities, Orange (6.7 ± 0.6 kg), Red (14.0 ± 0.9 kg) and Blue (24.0 ± 1.4 kg), in random order, before performing two more CMJ for post-test measure. Each testing session was separated by at least 48 h.
There was significant increase in jump height in all conditions (P < 0.05), but no significant difference in change in jump height between conditions (P > 0.05). There were small to moderate effect when comparing Orange and the other conditions. Peak force and velocity increased in Red (P < 0.05) and Orange (P < 0.05), respectively. Change in jump height was significantly correlated to change in peak velocity (r = 0.46, P = 0.002) and peak power (r = 0.46, P = 0.002).
The findings of the study showed that UCMJ and LCMJ were effective in improving jump height acutely, and an intensity level of about 10% body weight contributed by VR seems to be the optimum resistance level.
The purpose of this investigation was to use the RPE clamp protocol to examine sex-related differences in performance fatigability and neuromuscular responses as the result of a sustained isometric leg extension muscle action anchored to RPE = 2. Twenty adults (10 men, 10 women) performed sustained muscle actions at RPE = 2 for 5-min. Maximal voluntary isometric contractions (MVIC) were performed prior to and following the sustained muscle actions. Neuromuscular (electromyographic and mechanomyographic) parameters and force were recorded, and the values were normalized to respective MVICs and calculated every 5% across the 5-min work bout. Femoral artery blood flow (FABF) was assessed at pretest, immediately posttest, and 5-min posttest. Polynomial regression was used to define the individual and composite normalized neuromuscular and force versus time relationships during the sustained muscle action. Mixed factorial ANOVAs were used to examine differences in performance fatigability and blood flow. For performance fatigability, the men (62.4 ± 14.4 kg–43.1 ± 11.5 kg) exhibited a significantly (P < 0.05) greater decrease pretest to posttest in MVIC than the women (44.1 ± 4.8 kg vs. 38.1 ± 6.1 kg). There were different fatigue-induced neuromuscular patterns of responses between the men and women across time. For blood flow responses, however, there was no sex-related difference, but pretest (283.3 ± 70.8 mL/min) was significantly (P < 0.05) less than immediately posttest (424.5 ± 133.5 mL/min) and 5-min posttest (324.4 ± 78.3 mL/min). Thus, men demonstrated a greater degree of performance fatigability than the women, which was independent of differences in FABF. Factors such as the neuromuscular system and muscle morphology likely contributed to the difference in performance fatigability.
Two-thirds of sudden cardiac deaths are attributable to underlying cardiovascular conditions in young collegiate athletes. A 12-lead exercise stress test is a screening tool that can detect these abnormalities that may predispose collegiate athletes to sudden cardiac death, and can ensure athletes meet the physical demands of training and competition. The purpose of this study was to evaluate the electrocardiographic (ECG) characteristics of Division II collegiate athletes using the Seattle Criteria.
Fifty two athletes (males = 26; females = 26) of various ethnicities (Caucasian = 65%, Latino/Hispanic = 20%, and African American = 15%); from soccer (27%), tennis (17%), basketball (15%), softball (14%), cross country (9%), volleyball (6%), football (6%), and swimming (6%) completed cardiovascular screening with resting and exercise 12-lead ECG analysis. ECG abnormalities and anthropometrics were compared across race, gender, and sports using an ANOVA. Chi-square analysis was used to test for differences in the frequency of ECG findings across gender, race, and sports.
Although sport was not a predictor for an abnormal ECG, 73% of the athletes presented with athletes’ heart configuration, which was significantly higher in males than females (P = 0.02). The highest occurrence of these adaptations was observed in 100% of Latino/Hispanic athletes, compared to 75% of African American and 64% of Caucasian athletes.
With newer and more sensitive ECG screening criteria, the prevalence of false-positive tests is declining. Future research should focus on advancing the sensitivity and specificity of ECG interpretation in more diverse athletic populations regarding race and gender. The increasing incidence of sudden cardiac death in collegiate athletes warrants future research that evaluates the impact of implementing the 12-lead ECG as a standard screening tool for collegiate athletes.