Acute resistance exercise reduces heart rate complexity and increases QTc interval

Acute resistance exercise (RE) has been shown to reduce cardiac vagal control. Whether this would in turn affect QTc interval (an index of ventricular depolarization/repolarization) or heart rate complexity is not known. Heart rate variability (HRV), heart rate complexity (SampEn), and QT interval (rate corrected using Bazett, Fridericia, Hodges, and Framingham) were measured before and 5 min after an acute RE bout in twelve healthy young men. Normalized high frequency power of HRV (an index of cardiac parasympathetic modulation; HF (nu)), and SampEn were reduced following RE (p < 0.05). Bazett corrected QTc interval increased following RE (p < 0.05). Change in HF (nu) from rest to recovery was correlated with both change in SampEn (r = 0.51, p < 0.05) and change in QTc interval for each method of correction (r = - 0.67 to - 0.70, p < 0.05). Acute RE reduced HF spectral power of HRV and this was related to both reduced heart rate complexity and increased QTc length. Thus, during recovery from acute RE, there is prolongation of depolarization and repolarization of the ventricles concomitant with reduced cardiac irregularity, and this may be related to a reduction in cardiac vagal control.     

Effects of training periodization on cardiac autonomic modulation and endogenous stress markers in volleyball players

We investigated the effects of selective loads of periodization model (SLPM) on autonomic modulation of heart rate variability (HRV) and endogenous stress markers before and after a competition period in volleyball players (N=32). The experimental protocol for the evaluation of HRV consisted of using spectral analysis of time series composed of the R–R intervals derived from electrocardiogram obtained in the supine position and during the tilt test. Stress marker levels were determined by quantifying the plasma concentration of endogenous catecholamines, cortisol and free testosterone. The results showed no changes between the levels of HRV before and after a competition period. In contrast, the quantification of the plasma concentration of endogenous stress markers revealed reductions in the levels of total catecholamines, noradrenaline and cortisol. These changes were accompanied by increases in the concentration of free testosterone and in the testosterone/cortisol ratio. In conclusion, our results demonstrate that the SLPM did not change the cardiac autonomic modulation of HRV, but promoted beneficial adaptations in athletes, including positive changes in the plasma concentration of the endogenous stress markers. The absence of changes in HRV indicates that there is no direct relationship between cardiac autonomic modulation and endogenous stress markers in the present study.     

Neuromuscular and functional responses in professional soccer players during pre-season: implications for injury prevention

Objective

The purpose of this investigation was to assess the muscular strength of the knee extensors and flexors muscles, agility and functionality between dominant leg (DL) vs. non-dominant leg (NDL) of professional soccer players during pre-season.

Methods

Twenty-two healthy male professional soccer players (25.1?±?3.8 years; 182.1?±?5.9 cm; 79.3?±?5.4 kg; body fat 14.6?±?3.8%) from a club of the Brazilian second-division soccer league participated in this study. All soccer players underwent three tests to assess strength, power, and physical performance with an interval of 48 h inter-sessions. During the first assessment session, isokinetic tests were performed in which athletes performed maximal isokinetic concentric and eccentric contractions, as well as maximal isometric contractions. In the second and third assessment sessions, single leg step down and agility tests were performed, respectively.

Results

Maximum voluntary isometric contraction (MVIC) results showed a significant difference (p?<?0.04) between DL compared to the NDL for absolute and relative values. But, the isokinetic variables of knee extensors at 60°/s (total work and power) were significantly higher (p?<?0.03) in NDL. Pearson’s correlation was found to be significant between MVIC and single leg step down (SLSD) test for DL (r?=?0.70, p?=?0.0001) and NDL (r?=?0.58; p?=?0.002).

Conclusion

The results confirm that DL shows greater isometric strength than NDL. However, NDL revealed an increase in the total work and power output in professional soccer players. Furthermore, the SLSD test is recommended because it proved to be a good method for evaluating muscle strength by a positive correlation with MVIC.

     

The C allele in NOS3 -786 T/C polymorphism is associated with elite soccer player's status

The NOS3-786 T/C polymorphism (rs2070744) is a candidate to explain individual variations in sports related phenotypes. We determined the genotype and allele frequency of NOS3-786 T/C in a group of 60 male professional elite soccer players. Their results were compared with those of 100 world-class endurance athletes, 53 elite power athletes, and 100 sedentary, healthy men (controls) of the same Caucasian (Spanish) origin. There were significant differences in genotype frequencies between soccer players, controls, endurance and power elite athletes (all P ≤ 0.02). These results were confirmed when we analysed allelic frequencies (all P<0.01). The likelihood of having the C allele was higher in soccer players compared with (i) controls [odds ratio (OR), 2.165, 95% confidence interval (CI): 1.362-3.441], (ii) endurance athletes (OR: 1.879, 95%CI: 1.184-2.984), and (iii) power athletes (OR: 4.032, 95%CI: 2.307-7.047). In conclusion, the -786C allele is associated with the status of being an elite soccer player, compared with non-athletic controls and also with elite endurance and power athletes. More research is needed in other groups of elite soccer players in order to replicate the results of the present study.     

High levels of C‐reactive protein are associated with reduced vagal modulation and low physical activity in young adults

The purpose of this study was to examine the relationship between cardiac autonomic control derived from heart rate variability (HRV), high‐sensitivity C‐reactive protein (hs‐CRP) and physical activity (PA) levels measured using accelerometers. A total of 80 healthy university students volunteered to participate in this study (20.56 ± 0.82 years, 1.36 ± 1.5 mg/L of hs‐CRP). The participants were divided into groups based on tertiles of hs‐CRP. Analysis of covariance adjusted to PA was used to assess group differences in HRV. Associations between hs‐CRP, HRV indices and PA were analyzed using Pearson's correlation. The participants at the highest tertile of hs‐CRP (tertile 3) had lower cardiac vagal modulation (SDNN, tertile 1=78.05 ± 5.9,tertile 2=82.43 ± 5.9,tertile 3=56.03 ± 6.1; SD1, tertile 1=61.27 ± 5.3, tertile 2=62.93 ± 5.4, tertile 3=40.03 ± 5.5). In addition, vagal indices were inversely correlated with hs‐CRP but positively correlated with PA (SDNN r=?0.320, SD1 r=?0.377; SDNN r=0.304, SD1 r=0.299; P<0.05). Furthermore, the most physically active subjects had lower levels of hs‐CRP and the highest levels of vagal modulation.     

Qt dispersion in soccer players during exercise testing

Screening for cardiac health should involve relevant parameters or indices that are easy and inexpensive to obtain. Various cardiac adaptation mechanisms develop during regular exercise that are affected by many factors, and these are reflected on a surface electrocardiogram. QT dispersion has been considered a surrogate for heterogeneity of repolarization, leading to ventricular arrhythmias. We compared QT parameters between athletes and sedentary subjects. A total of 225 men were assessed, comprising a group of professional soccer players and sedentaries. Each subject underwent supine 12-lead electrocardiographic examinations and exercise testing by ergospirometry. QT parameters were taken at rest and at peak exercise. Peak oxygen consumption was considerably higher in the athletes than in the controls (59.3 +/- 5.6 vs. 44.3 +/- 2.4 ml/kg/min, mean +/- SD, p < 0.001). QT parameters at rest: There were significant differences in heart-rate-corrected rest maximal QT duration (413.9 +/- 50.5 vs. 445.3 +/- 45.7 ms, p < 0.001) and in heart-rate-corrected rest minimum QT duration (380.5 +/- 51.2 vs. 409.5 +/- 46.7 ms, p < 0.001). QT parameters at peak exercise: maximal QT duration at peak exercise (253.9 +/- 20.8 vs. 261.7 +/- 26.2, p = 0.02), QT dispersion at peak exercise (25.2 +/- 9.1 vs. 29.5 +/- 15.8 ms, p = 0.04), heart-rate-corrected QT dispersion at peak exercise (44.6 +/- 16.4 vs. 52.6 +/- 28.3 ms, p = 0.03) differed significantly between professional soccer players and controls. QT dispersion and corrected QT dispersion at peak exercise are lower in athletes than in controls. Athletes and other subjects identified with a long QT interval should be examined at regular intervals.     

Cardiac and autonomic adaptations to a wheelchair hockey match in athletes with muscular dystrophy

Muscular dystrophies (MD), such as Duchenne’s MD (DMD), appear in childhood and progressively lead to respiratory and/or heart failure. Exercise-based therapy may be helpful, but the cardiac and autonomic adaptations to sport activities are poorly studied in MD patients. Heart rate (HR) was measured in 30 players (all males, 28±6 [m±SD] years) with different forms of MD (divided into 2 groups according to pathology severity): (a) before, (b) during and (c) immediately after a wheelchair hockey match. In addition, HR variability (HRV) indexes RMSSD, SD1, LF, HF and LF/HF ratio were measured before and during the game in a subgroup of 9 DMD athletes. A sinus tachycardia was found in all MD athletes before the game (114±13 bpm in DMD, 113±18 bpm in other muscular dystrophies, OMD). In both DMD and OMD groups HR increased significantly from pre-game to game and decreased during recovery. During the game, HR was higher in the OMD compared to the DMD group. The subgroup of DMD athletes evidenced an almost normal parasympathetic withdrawal and altered sympathetic adaptations to exercise. Sinus tachycardia affects MD patients independently from MD form. However, the residual autonomic modulation allows the athletes to adapt to the energetic demands of wheelchair hockey.     

Plantar pressure asymmetry and risk of stress injuries in the foot of young soccer players

BackgroundAsymmetries in the magnitude of plantar pressure are considered a risk factor for stress fracture of the fifth metatarsal in soccer athletes.ObjectiveTo investigate the presence of plantar pressure asymmetries among young soccer athletes.DesignObservational.SettingLaboratory.ParticipantsThirty young adolescents divided into a soccer player group (n = 15) or a matched control group (n = 15).Main outcome measuresMean plantar pressure was determined for seven different regions of the foot. Data were compared between the preferred and non-preferred foot, and between the groups, during barefoot standing on a pressure mat system.ResultsHigher pressure was found in the hallux, 5th metatarsal and medial rearfoot of the non-preferred foot in the young soccer players. These asymmetries were not observed in the control group. Magnitudes of plantar pressure did not differ between the groups.ConclusionYoung soccer players present asymmetries in plantar pressure in the hallux, 5th metatarsal and medial rearfoot, with higher pressure observed in the non-preferred foot.     

Heart rate variability during night sleep and after awakening in overtrained athletes

PURPOSE: This study was conducted to test the hypothesis of autonomic imbalance in overtrained athletes during sleep and after awakening with analyses of heart rate variability (HRV) and nocturnal urine stress hormones. METHODS: We examined 12 athletes diagnosed to be severely overtrained (OA, 6 men and 6 women, mean age (+/-SD) 25 +/- 7 yr) and 12 control athletes (CA, 6 men and 6 women, mean age 24 +/- 5 yr). Overtraining diagnosis was further supported by higher perceived stress in OA than in CA (24.8 +/- 10.8 vs 15.3 +/- 5.5, P < 0.05). HRV was analyzed with time and frequency domain methods from RR intervals (RRI) recorded during sleep and after awakening. Nocturnal urine stress hormones were analyzed by liquid chromatography. RESULTS: No differences were found in HRV or stress hormones during night sleep. After awakening, the standard deviation of RRI (84 +/- 31 vs 116 +/- 41 ms, P < 0.05) and low-frequency power of RRI (2153 +/- 2232 vs 4286 +/- 2904 ms, P < 0.05) were lower in OA than in CA. From sleep to after awakening, the coefficient of variation of RRI decreased more in OA than in CA (from 11.8 +/- 3.3 to 7.7 +/- 2.5%, P < 0.001 vs from 11.9 +/- 1.8 to 10.0 +/- 2.5%, P < 0.01, respectively, interaction P < 0.05). CONCLUSION: The present findings suggest that in OA, cardiac autonomic modulation is at the level of control athletes during sleep, but the parasympathetic cardiac modulation is slightly diminished after awakening. Further investigations should concentrate on autonomic responses to different challenges, such as awakening in the present study.     

No evidence of impaired neurocognitive performance in collegiate soccer players

A high incidence of cerebral concussion has been reported among soccer players. We studied whether long-term or chronic neuropsychological dysfunction was present in collegiate soccer players. Two hundred forty subjects from a National Collegiate Athletic Association division I institution were stratified into three groups: soccer athletes (91), nonsoccer athletes (96 women's field hockey, women's lacrosse, and baseball players), and controls (53 college students). Subjects completed a concussion history questionnaire and underwent preseason baseline neuropsychological testing before the start of either the freshman or sophomore year. Data were collected on the results of six neuropsychological tests and from a concussion history questionnaire for number of previous concussions, Scholastic Aptitude Test results, and exposure to soccer and heading. Despite an average of 15.3 seasons of soccer exposure and a higher prevalence of previous concussions, the soccer athletes did not demonstrate impaired neurocognitive function or scholastic aptitude when compared with the nonsoccer athletes or the student nonathletes. Additionally, there was no significant relationship between a history of soccer-related concussion and either neurocognitive performance or scholastic aptitude. Neither participation in soccer nor a history of soccer-related concussions was associated with impaired performance of neurocognitive function in high-level United States soccer players.     

Effectiveness of a neuromuscular and proprioceptive training program in preventing anterior cruciate ligament injuries in female athletes: 2-year follow-up

BACKGROUND: Among female athletes it has not been established whether a neuromuscular and proprioceptive sports-specific training program will consistently reduce the incidence of anterior cruciate ligament injuries. PURPOSE: To determine whether a neuromuscular and proprioceptive performance program was effective in decreasing the incidence of anterior cruciate ligament injury within a select population of competitive female youth soccer players. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: In 2000, 1041 female subjects from 52 teams received a sports-specific training intervention in a prospective non-randomized trial. The control group consisted of the remaining 1905 female soccer players from 95 teams participating in the same league who were age and skill matched. In the 2001 season, 844 female athletes from 45 teams were enrolled in the study, with 1913 female athletes (from 112 teams) serving as the age- and skill-matched controls. All subjects were female soccer players between the ages of 14 and 18 and participated in either their traditional warm-up or a sports-specific training intervention before athletic activity over a 2-year period. The intervention consisted of education, stretching, strengthening, plyometrics, and sports-specific agility drills designed to replace the traditional warm-up. RESULTS: During the 2000 season, there was an 88% decrease in anterior cruciate ligament injury in the enrolled subjects compared to the control group. In year 2, during the 2001 season, there was a 74% reduction in anterior cruciate ligament tears in the intervention group compared to the age- and skill-matched controls. CONCLUSION: Using a neuromuscular training program may have a direct benefit in decreasing the number of anterior cruciate ligament injuries in female soccer players.     

军队离退休干部高血压病患者心率变异性与QT离散度五年前后对比分析

目的　探讨军队离退休干部高血压病患者QTd和HRV的变化规律。方法　利用 2 4h动态心电图 (Holter) ,分析HRV时域指标和QTd的五年前后的变化。结果　 5年后HRV时域指标明显降低 (P <0 .0 5 ) ;QTd则明显增加 (P <0 .0 5 )。相关性分析提示QTd和HRV指标之间有相关关系。结论　HRV和QTd检测是判定老年高血压病患者自主神经功能损害程度及预测预后的较有价值的无创性检测手段     

Age and heart rate variability after soccer games

To observe the effect of age on the changes in heart rate variability (HRV) of adult amateur athletes after playing a soccer game, 20 male were divided into two groups: middle-aged (n = 10, 35-55 years) and aged (n = 10, 56-75 years). Before and after 2-hour soccer games, HRV and blood pressure were recorded. In both groups heart rate increased greatly after exercise (73.1 ± 14.8 bpm vs 102.6 ± 16.2 bpm, p < 0.01 and 71.1 ± 8.6 bpm vs 89.9 ± 15.5 bpm, p < 0.01). In the middle-aged group, systolic blood pressure (SBP) did not change (124.0 ± 12.0 mmHg vs 118.9 ± 11.7 mmHg), while the mean standard deviation of the N-N intervals (SDNN), square root of the mean squared differences of successive N-N intervals (RMSSD), total power (TP), low frequency (LF) power, and high frequency (HF) power changed significantly (p < 0.05); in the aged group SBP decreased from 147.2 ± 23.7 mmHg to 127.7 ± 24.7 mmHg (p < 0.01), but SDNN, RMSSD, TP, LF, and HF did not change. It seems that in aged people the accommodation capability of the autonomic nervous system is different from that in middle-aged people.     

Prolonged neuropsychological impairments following a first concussion in female university soccer athletes.

OBJECTIVE: Although research is accumulating on the cognitive sequelae from sports-related concussions in men, little to nothing is known about the prolonged cognitive outcome after a concussion in women. This point is important because recent evidence suggests that female athletes are at greater risk of sustaining a concussion. DESIGN: We assessed cognitive functioning after a first concussion in female soccer players, 6 to 8 months after their injury. The first-time concussed athletes were compared with a group of age-matched teammates who had never experienced a concussion. SETTING AND PARTICIPANTS: A total of 22 female university-level soccer players participated in the study. MAIN OUTCOME MEASUREMENTS: Paper-and-pencil and computerized tasks were used to assess different neuropsychological functions. RESULTS: Short- and long-term verbal memory, attention, and simple reaction time were normal. In contrast, compared with the control group, the concussed athletes were significantly slower on tasks that required decision making (complex reaction time), inhibition and flexibility (Stroop), and planning (Tour of London task). CONCLUSIONS: The results of this study suggest that cognitive functions related to cognitive processing speed are most vulnerable to a sports-related concussion and are still impaired for a half year after injury in university-level female soccer players.     

ACTN3 genotype in professional soccer players

The authors studied the frequency distribution of alpha-actinin-3 (ACTN3) R577X genotypes in 60 top-level professional soccer players. The results were compared with those of 52 elite endurance athletes and 123 sedentary controls. The per cent distribution of RR and RX genotypes in soccer players (48.3% and 36.7%) was significantly higher and lower, respectively, than controls (28.5% and 53.7%) and endurance athletes (26.5% and 52%) (p = 0.041). Although there are notable exceptions, elite soccer players tend to have the sprint/power ACTN3 genotype.     

Physiological and performance adaptations to an in-season soccer camp in the heat: associations with heart rate and heart rate variability

The aim of the present study was to examine the associations between adaptive responses to an in‐season soccer training camp in the heat and changes in submaximal exercising heart rate (HRex, 5‐min run at 9 km/h), postexercise HR recovery (HRR) and HR variability (HRV). Fifteen well‐trained but non‐heat‐acclimatized male adult players performed a training week in Qatar (34.6 ± 1.9°C wet bulb globe temperature). HRex, HRR, HRV (i.e. the standard deviation of instantaneous beat‐to‐beat R–R interval variability measured from Poincaré plots SD1, a vagal‐related index), creatine kinase (CK) activity, plasma volume (PV) changes, and post‐5‐min run rate of perceived exertion (RPE) were collected at six occasions in temperate environmental conditions (22°C). Players also performed the yo‐yo intermittent recovery test level 1 (Yo‐Yo IR1) in the same environmental conditions (22°C), both at the beginning and at the end of the training week. Throughout the intervention, HRex and HRV showed decreasing (P < 0.001) and increasing (P < 0.001) trends, respectively, while HRR remained unaffected (P = 0.84). Changes in HRex [?0.52, 90% confidence limits (?0.64; ?0.38), P < 0.001] and SD1 [0.35 (0.19; 0.49), P < 0.001] were correlated with those in PV. There was no change in RPE (P = 0.92), while CK varied according to training contents (P < 0.001), without association with HR‐derived measures. Yo‐Yo IR1 performance increased by 7 ± 9% (P = 0.009), which was correlated with changes in HRex [?0.64 (?0.84; ?0.28), P = 0.01]. In conclusion, we found that an in‐season soccer training camp in the heat can significantly improve PV and soccer‐specific physical performance; both of which are associated with changes in HRex during a 5‐min submaximal run.     

Injury history as a risk factor for incident injury in youth soccer

Objectives: To determine if athletes with a self reported history of previous injury have a higher incident injury rate than athletes without a self reported injury history.

Methods: A prospective cohort study of Classic League soccer players playing at the level under 12 through under 18. Injury history forms were mailed to all registering Classic League soccer players in the North Carolina Youth Soccer Association during 1997–2000 (n = 7000); 1483 (19%) returned the baseline questionnaire and were followed up for injuries.

Results: There were 5139 player-seasons of follow up and an estimated 171 957 athlete-exposures. More than half self reported an injury history (59.7%). Overall, the unadjusted incidence rate was 4.6 (95% confidence interval (CI) 4.3 to 4.9) incident injuries per 1000 athlete-exposures. Multivariate generalised Poisson regression modelling indicated that players with one previous injury had a twofold greater risk of incident injury (IRR = 2.6; 95% CI 2.0 to 3.3), and those with two or more previous injuries had a threefold greater risk of incident injury (IRR = 3.0; 95% CI 2.3 to 3.8) compared with athletes with no previous injuries.

Conclusions: Injury history was associated with an increased injury rate. This suggests that, even in these youth soccer players, those with an injury history may be at higher risk.

     

Neuromuscular and athletic performance following core strength training in elite youth soccer: Role of instability

Cross‐sectional studies revealed that inclusion of unstable elements in core‐strengthening exercises produced increases in trunk muscle activity and thus potential extra stimuli to induce more pronounced performance enhancements in youth athletes. Thus, the purpose of the study was to investigate changes in neuromuscular and athletic performance following core strength training performed on unstable (CSTU) compared with stable surfaces (CSTS) in youth soccer players. Thirty‐nine male elite soccer players (age: 17 ± 1 years) were assigned to two groups performing a progressive core strength‐training program for 9 weeks (2–3 times/week) in addition to regular in‐season soccer training. CSTS group conducted core exercises on stable (i.e., floor, bench) and CSTU group on unstable (e.g., Thera‐Band® Stability Trainer, Togu© Swiss ball) surfaces. Measurements included tests for assessing trunk muscle strength/activation, countermovement jump height, sprint time, agility time, and kicking performance. Statistical analysis revealed significant main effects of test (pre vs post) for trunk extensor strength (5%, P < 0.05, d = 0.86), 10–20‐m sprint time (3%, P < 0.05, d = 2.56), and kicking performance (1%, P < 0.01, d = 1.28). No significant Group × test interactions were observed for any variable. In conclusion, trunk muscle strength, sprint, and kicking performance improved following CSTU and CSTS when conducted in combination with regular soccer training.     

Anthropometric and fitness profiles of elite players in two football codes

BACKGROUND: The aims were to describe anthropometric and performance characteristics of elite players in two football codes and explore the differences between them. METHODS: Data were compared by means of "t"-tests. Subjects: subjects were 19 professional soccer players and 33 inter-county Gaelic football players. Settings: measurements were made on members of a Premier League soccer team throughout their regular season, whilst the Gaelic footballers were members of the Mayo squad preparing for the 1999 All-Ireland championship. RESULTS: The variability in stature was significantly greater in the soccer players compared to the Gaelic footballers (p<0.01). Performances in the 10-m and 30-m sprints, and in vertical jump were superior in the soccer group compared to the Gaelic footballers (p<0.01). CONCLUSIONS: The intra-group variability on the anthropometric and performance measures of the soccer players is likely to be due to the specificity of positional roles. The combined groups could be described as lean and muscular with a reasonably high level of capacity in all areas of physical performance. Anaerobic characteristics of the professional soccer players were superior to those of Gaelic football players. It is concluded that anthropometric and performance assessment of elite footballers using mean values masks the heterogeneity evident within the football codes.