The ACTN3 R577X (rs1815739) genotype has been associated with
athletic status and muscle phenotypes, although not consistently. Our objective
was to conduct a meta-analysis of the published literature on athletic status
and investigate its associations with physical capability in several new
population-based studies. Relevant data were extracted from studies in the
literature, comparing genotype frequencies between controls and sprint/power and
endurance athletes. For life course physical capability, data were used from two
studies of adolescents and seven studies in the Healthy Ageing across the Life
Course (HALCyon) collaborative research program, involving individuals aged
between 53 and 90+ years. We found evidence from the published literature
to support the hypothesis that in Europeans the RR genotype is more common among
sprint/power athletes compared with their controls. There is currently no
evidence that the X allele is advantageous to endurance athleticism. We found no
association between R577X and grip strength (P = 0.09,
n = 7,672 in males; P =
0.90, n = 7,839 in females), standing balance, timed get
up and go, or chair rises in our studies of physical capability. The
ACTN3 R577X genotype is associated with sprint/power
athletic status in Europeans, but does not appear to be associated with
objective measures of physical capability in the general population. Hum Mutat
32:1–11, 2011. © 2011 Wiley-Liss, Inc.
ACTN3; Actinin-3; athlete; aging; SNP; grip strength
The ACTN3 R577X polymorphism (rs1815739) is a strong candidate to influence elite athletic performance. Yet, controversy exists in the literature owing to between-studies differences in the ethnic background and sample size of the cohorts, the latter being usually low, which makes comparisons difficult. In this case:control genetic study we determined the association between elite athletic status and the ACTN3 R577X polymorphism within three cohorts of European Caucasian men, i.e. Spanish, Polish and Russian [633 cases (278 elite endurance and 355 power athletes), and 808 non-athletic controls]. The odds ratio (OR) of a power athlete harbouring the XX versus the RR genotype compared with sedentary controls was 0.54 [95% confidence interval (CI): 0.34–0.48; P = 0.006]. We also observed that the OR of an endurance athlete having the XX versus the RR genotype compared with power athletes was 1.88 (95%CI: 1.07–3.31; P = 0.028). In endurance athletes, the OR of a “world-class” competitor having the XX genotype versus the RR+RX genotype was 3.74 (95%CI: 1.08–12.94; P = 0.038) compared with those of a lower (“national”) competition level. No association (P>0.1) was noted between the ACTN3 R577X polymorphism and competition level (world-class versus national-level) in power athletes. Our data provide comprehensive support for the influence of the ACTN3 R577X polymorphism on elite athletic performance.
Ability of athletes in speed or endurance contests somehow is determined by inherited muscle fiber types. One of the important genes involved in sport genetics is ACTN3 that is located on chromosome 11q13-q14 and encodes α-actinin-3, which belongs to highly conserved family of α-actinin proteins. Genetic analysis of α-actinin-3 gene has showed a polymorphism R577X (rs1815739), which results in premature stop codon and leads to non functional α-actnin-3 protein. ACTN3 genotype can contribute to the performance in elite and endurance activities.
R577X polymorphism replaces arginine by stop codon. Individuals homozygous for R577 have full copy of α-actinin-3 and elite and power sprint athletes show significantly higher frequency of 577R allele. In the other hand, some studies represented that X allele have high level of frequency in endurance athletes. However, this data remains controversial Since there is no information about the frequency of ACTN3 genotype in our population therefore as the first step it is essential to determine the genetic background of Iranian population. The objective of this study was to genotype normal Iranian individuals to determine the prevalence of each allele in our population.
We used PCR-RFLP method for genotyping 210 normal individuals.
Total of 210 Iranian normal individuals for distribution of R577X and R alleles were genotyped. The different genotypes were as follow; 24% RR (50/210), 65%RX (136/210) and 11%XX (24/210), with allelic distribution of 0.56 and 0.44 for 577R and 577X alleles of ACTN3.
This allelic distribution for Iranian's is more close to Caucasian population, which is concurrent with the route of ancient human's migration from Iran Plateau toward Europe.
Our results showed no different patterns of allelic distribution among female and males, which was the same in other studies too, although some differences has been reported in the studies on athletes population.
Sport Genetics; ACTN3; Iran
Genetic polymorphism is suggested to be associated with human physical performance. The angiotensin I-converting enzyme insertion/deletion (ACE I/D) polymorphism and the α-actinin-3 gene (ACTN3) R577X polymorphism have been most widely studied for such association analysis. However, the findings are frequently heterogeneous. We aim to summarize the associations of ACE I/D and ACTN3 R577X with sport performance by means of meta-analysis.
We systematically reviewed and quantitatively summarized published studies, until October 31, 2012, on relationship between ACE/ACTN3 genetic polymorphisms and sports performance, respectively.
A total of 366 articles on ACE and 88 articles on ACTN3 were achieved by literature search. A significant association was found for ACE II genotype compared to D allele carriage (DD+ID) with increased possibility of physical performance (OR, 1.23; 95% CI, 1.05–1.45). With respect to sport discipline, the II genotype was found to be associated with performance in endurance athletes (OR, 1.35; 95% CI, 1.17–1.55). On the other hand, no significant association was observed for ACTN3 RR genotype as compared to X allele carriage (XX+RX) (OR, 1.03; 95% CI, 0.92–1.15). However, when restricted the analyses to power events, a significant association was observed (OR, 1.21; 95% CI, 1.03–1.42).
Our results provide more solid evidence for the associations between ACE II genotype and endurance events and between ACTN3 R allele and power events. The findings suggest that the genetic profiles might influence human physical performance.
Alpha-actinins are an ancient family of actin-binding proteins that play structural and regulatory roles in cytoskeletal organization. In skeletal muscle, α-actinin-3 protein is an important structural component of the Z disc, where it anchors actin thin filaments, helping to maintain the myofibrillar array. A common nonsense polymorphism in codon 577 of the ACTN3 gene (R577X) results in α-actinin-3 deficiency in XX homozygotes. Based on knowledge about the role of ACTN3 R557X polymorphism in skeletal muscle function, we postulated that the genetic polymorphism of ACTN3 could also improve sprint and power ability.
We compared genotypic and allelic frequencies of the ACTN3 R557X polymorphism in two groups of men of the same Caucasian descent: 158 power-orientated athletes and 254 volunteers not involved in competitive sport.
The genotype distribution in the group of power-oriented athletes showed significant differences (P=0.008) compared to controls. However, among the investigated subgroups of athletes, only the difference of ACTN3 R577X genotype between sprinters and controls reached statistical significance (P=0.041). The frequencies of the ACTN3 577X allele (30.69% vs. 40.35%; P=0.005) were significantly different in all athletes compared to controls.
Our results support the hypothesis that the ACTN3 577XX allele may have some beneficial effect on sprint-power performance, because the ACTN3 XX genotype is significantly reduced in Polish power-oriented athletes compared to controls. This finding seems to be in agreement with previously reported case-control studies. However, ACTN3 polymorphism as a genetic marker for sport talent identification should be interpreted with great caution.
α-actinin-3; genotype; power-orientated athletes
Previous reports have shown a lower proportion of the ACTN3 X/X genotype (R577X nonsense polymorphism) in sprint-related athletes compared to the general population, possibly attributed to impairment of muscle function related to α-actinin-3 deficiency. In the present study, we examined the frequency of the X/X genotype in both Black and White elite-level bodybuilders and strength athletes in comparison to the general population. A reference population of 668 Whites (363 men and 305 women) and 208 Blacks (98 men and 110 women) was genotyped for the ACTN3 R577X polymorphism. Strength athletes (52 white and 23 black; 4 women) consisting predominantly of world class and locally competitive bodybuilders, and elite powerlifters were recruited and similarly genotyped. Significantly lower X/X genotype frequencies were observed in the athletes (6.7%) vs controls (16.3%; P = 0.005). The X/X genotype was significantly lower in White athletes (9.7%) vs controls (19.9%; P = 0.018). No black athletes (0%) were observed with the X/X genotype, though this finding only approached statistical significance vs controls (4.8%; P = 0.10). The results indicate that the ACTN3 R577X nonsense allele (X) is under-represented in elite strength athletes, consistent with previous reports indicating that α-actinin-3 deficiency appears to impair muscle performance.
skeletal muscle; polymorphism; muscle strength
Human physical performance is notably reduced with ageing. Although the effects of ageing are often compounded by disuse, the study of master athletes provides an opportunity for investigating the effects of ageing per se. It is often held that sprinting is more affected than endurance performance. However, past analyses of master athletic world record data have yielded opposite observations. We argue here that our understanding of these data improves by considering how, biomechanically, metabolic power is related to athletic performance. In line with earlier studies, our analysis showed that running speed declines with age in a more pronounced way for endurance events than for sprinting events, confirming former studies. However, when assessing the metabolic power required to achieve the running world records, sprint and endurance events show a relatively uniform decline with age across the different events. This study has reconciled formerly conflicting scientific results and improves our understanding of the ageing process. However, it is unclear as to which are the governing mechanisms that cause the different systems in our body, responsible for sprinting and for endurance performance, to be affected by ageing in a remarkably uniform way.
master athletes; veteran athletes; maximum performance; sport; exercise
The muscle protein α‐actinin‐3 (ACTN3) is normally thought to be expressed in type II muscle fibres and to be necessary for high‐power, high‐velocity muscle contractions, such as those typically seen in speed/power athletes. The authors report the case of a Spanish elite long jumper (two times Olympian, personal best of 8.26 m) whose genotype for the ACTN3 gene is 577XX (ACTN3 deficient). These data suggest that there might be notable exceptions to the concept that ACTN3 is the “gene for speed”.
A common nonsense polymorphism in the ACTN3 gene results in the absence of α-actinin-3 in XX individuals. The wild type allele has been associated with power athlete status and an increased force output in numeral studies, though the mechanisms by which these effects occur are unclear. Recent findings in the Actn3−/− (KO) mouse suggest a shift towards ‘slow’ metabolic and contractile characteristics of fast muscle fibers lacking α-actinin-3. Skinned single fibers from the quadriceps muscle of three men with spinal cord injury (SCI) were tested regarding peak force, unloaded shortening velocity, force-velocity relationship, passive tension and calcium sensitivity. The SCI condition induces an ‘equal environment condition’ what makes these subjects ideal to study the role of α-actinin-3 on fiber type expression and single muscle fiber contractile properties. Genotyping for ACTN3 revealed that the three subjects were XX, RX and RR carriers, respectively. The XX carrier’s biopsy was the only one that presented type I fibers with a complete lack of type IIx fibers. Properties of hybrid type IIa/IIx fibers were compared between the three subjects. Absence of α-actinin-3 resulted in less stiff type IIa/IIx fibers. The heterozygote (RX) exhibited the highest fiber diameter (0.121±0.005 mm) and CSA (0.012±0.001 mm2) and, as a consequence, the highest peak force (2.11±0.14 mN). Normalized peak force was similar in all three subjects (P = 0.75). Unloaded shortening velocity was highest in R-allele carriers (P<0.001). No difference was found in calcium sensitivity. The preservation of type I fibers and the absence of type IIx fibers in the XX individual indicate a restricted transformation of the muscle fiber composition to type II fibers in response to long-term muscle disuse. Lack of α-actinin-3 may decrease unloaded shortening velocity and increase fiber elasticity.
Two mature elite Sambo wrestlers were studied during a 22-day pre-European Championship period, during which they were to lose weight and maintain their top physical performance characteristics. During this time the athletes underwent intensive training coupled with a hypocaloric diet. Both lost approximately 8% of their initial body weight, while maintaining their pre-weight loss maximum oxygen uptake, anaerobic threshold and maximum isometric strength. These variables therefore increased when expressed relative to the lower body weight. Isometric endurance and short-term sprinting ability, however, were compromised by the weight-loss regimen, decreasing by up to 7% and 13% respectively. Following a well-planned weight-reduction programme coupled with serious training, aerobic power and isometric strength were unaffected and/or improved, but prolonged anaerobic exercise performance was impaired.
Several age-related traits are associated with shorter telomeres, the structures that cap the end of linear chromosomes. A common polymorphism near the telomere maintenance gene TERT has been associated with several cancers, but relationships with other ageing traits such as physical capability have not been reported.
As part of the Healthy Ageing across the Life Course (HALCyon) collaborative research programme, men and women aged between 44 and 90 years from 9 UK cohorts were genotyped for the single nucleotide polymorphism (SNP) rs401681. We then investigated relationships between the SNP and 30 age-related phenotypes, including cognitive and physical capability, blood lipid levels and lung function, pooling within-study genotypic effects in meta-analyses.
No significant associations were found between the SNP and any of the cognitive performance tests (e.g. pooled beta per T allele for word recall z-score=0.02, 95% CI: -0.01- 0.04, p-value=0.12, n=18,737), physical performance tests (e.g. pooled beta for grip strength=-0.02, 95% CI:-0.045- 0.006, p-value=0.14, n=11,711), blood pressure, lung function or blood test measures. Similarly, no differences in observations were found when considering follow-up measures of cognitive or physical performance after adjusting for its measure at an earlier assessment.
The lack of associations between SNP rs401681 and a wide range of age-related phenotypes investigated in this large multi-cohort study suggests that whilst this SNP may be associated with cancer, it is not an important contributor to other markers of ageing.
Aging; ageing; middle-aged; telomere; cognition; physical
Several age-related traits are associated with shorter telomeres, the structures that cap the end of linear chromosomes. A common polymorphism near the telomere maintenance gene TERT has been associated with several cancers, but relationships with other aging traits such as physical capability have not been reported. As part of the Healthy Ageing across the Life Course (HALCyon) collaborative research programme, men and women aged between 44 and 90 years from nine UK cohorts were genotyped for the single-nucleotide polymorphism (SNP) rs401681. We then investigated relationships between the SNP and 30 age-related phenotypes, including cognitive and physical capability, blood lipid levels and lung function, pooling within-study genotypic effects in meta-analyses. No significant associations were found between the SNP and any of the cognitive performance tests (e.g. pooled beta per T allele for word recall z-score = 0.02, 95% CI: −0.01 to 0.04, P-value = 0.12, n = 18 737), physical performance tests (e.g. pooled beta for grip strength = −0.02, 95% CI: −0.045 to 0.006, P-value = 0.14, n = 11 711), blood pressure, lung function or blood test measures. Similarly, no differences in observations were found when considering follow-up measures of cognitive or physical performance after adjusting for its measure at an earlier assessment. The lack of associations between SNP rs401681 and a wide range of age-related phenotypes investigated in this large multicohort study suggests that while this SNP may be associated with cancer, it is not an important contributor to other markers of aging.
aging; cognition; middle-aged; physical; telomere
Good bone and joint health is essential for the physical tasks of daily living and poorer indicators of physical capability in older adults have been associated with increased mortality rates. Genetic variants of indicators of bone and joint health may be associated with measures of physical capability.
As part of the Healthy Ageing across the Life Course (HALCyon) programme, men and women aged between 52 and 90 + years from six UK cohorts were genotyped for a polymorphism associated with serum calcium (rs1801725, CASR), two polymorphisms associated with bone mineral density (BMD) (rs2941740, ESR1 and rs9594759, RANKL) and one associated with osteoarthritis risk rs3815148 (COG5). Meta-analysis was used to pool within-study effects of the associations between each of the polymorphisms and measures of physical capability: grip strength, timed walk or get up and go, chair rises and standing balance.
Few important associations were observed among the several tests. We found that carriers of the serum calcium-raising allele had poorer grip strength compared with non-carriers (pooled p = 0.05, n = 11,239) after adjusting for age and sex. Inconsistent results were observed for the two variants associated with BMD and we found no evidence for an association between rs3815148 (COG5) and any of the physical capability measures.
Our findings suggest elevated serum calcium levels may lead to lower grip strength, though this requires further replication. Our results do not provide evidence for a substantial influence of these variants in ESR1, RANKL and COG5 on physical capability in older adults.
► We examined associations between bone-related genotypes and physical capability. ► We conducted a meta-analysis on 12,836 middle-age adults. ► We found CASR may be associated with grip strength. ► No substantial support for specific bone mineral density variants and physical capability.
BMD, bone mineral density; OA, osteoarthritis; BMI, body mass index; SNP, single nucleotide polymorphism; CaPS, Caerphilly Prospective Study; ELSA, English Longitudinal Study of Ageing; HAS, Hertfordshire Ageing Study; HCS, Hertfordshire Cohort Study; LBC1921, The Lothian Birth Cohort 1921; NSHD, National Survey of Health and Development; HWE, Hardy–Weinberg equilibrium; WHR, waist–hip ratio; GWAS, genome-wide association studies; Aging; Grip strength; Calcium; Bone mineral density; Osteoarthritis
Exercise phenotypes have played a key role for ensuring survival over human evolution. We speculated that some genetic variants that influence exercise phenotypes could be associated with exceptional survival (i.e. reaching ≥100years of age). Owing to its effects on muscle structure/function, a potential candidate is the Arg(R)577Ter(X) polymorphism (rs1815739) in ACTN3, the structural gene encoding the skeletal muscle protein α-actinin-3. We compared the ACTN3 R577X genotype/allele frequencies between the following groups of ethnically-matched (Spanish) individuals: centenarians (cases, n = 64; 57 female; age range: 100–108 years), young healthy controls (n = 283, 67 females, 216 males; 21±2 years), and humans who are at the two end-points of exercise capacity phenotypes, i.e. muscle endurance (50 male professional road cyclists) and muscle power (63 male jumpers/sprinters). Although there were no differences in genotype/allele frequencies between centenarians (RR:28.8%; RX:47.5%; XX:23.7%), and controls (RR:31.8%; RX:49.8%; XX:18.4%) or endurance athletes (RR:28.0%; RX:46%; XX:26.0%), we observed a significantly higher frequency of the X allele (P = 0.019) and XX genotype (P = 0.011) in centenarians compared with power athletes (RR:47.6%; RX:36.5%;XX:15.9%). Notably, the frequency of the null XX (α-actinin-3 deficient) genotype in centenarians was the highest ever reported in non-athletic Caucasian populations. In conclusion, despite there were no significant differences with the younger, control population, overall the ACTN3 genotype of centenarians resembles that of world-class elite endurance athletes and differs from that of elite power athletes. Our preliminary data would suggest a certain ‘survival’ advantage brought about by α-actinin-3 deficiency and the ‘endurance’/oxidative muscle phenotype that is commonly associated with this condition.
Physical performance measures are widely used to assess physical function, providing information about physiological and biomechanical aspects of motor performance. However they do not provide insight into the attentional and visual demands for motor performance. A figure-of-eight sprint test was therefore developed to measure the attentional and visual demands for repeated-sprint performance. The aims of the study were: 1) to assess test-retest reliability of the figure-of-eight sprint test, and 2) to study the attentional and visual demands for sprint performance in a non-fatigued and fatigued condition.
Twenty-seven healthy athletes were included in the study. To determine test-retest reliability, a subgroup of 19 athletes performed the figure-of-eight sprint test twice. The figure-of-eight sprint test consisted of nine 30-second sprints. The sprint test consisted of three test parts: sprinting without any restriction, with an attention-demanding task, and with restricted vision. Increases in sprint times with the attention-demanding task or restricted vision are reflective of the attentional and visual demands for sprinting. Intraclass correlation coefficients (ICCs) and mean difference between test and retest with 95% confidence limits (CL) were used to assess test-retest reliability. Repeated-measures ANOVA were used for comparisons between the sprint times and fatigue measurements of the test parts in both a non-fatigued and fatigued condition.
The figure-of-eight sprint test showed good test-retest reliability, with ICCs ranging from 0.75 to 0.94 (95% CL: 0.40-0.98). Zero lay within the 95% CL of the mean differences, indicating that no bias existed between sprint performance at test and retest. Sprint times during the test parts with attention-demanding task (P = 0.01) and restricted vision (P < 0.001) increased significantly compared to the base measurement. Furthermore the sprint times and fatigue measurements increased significantly in fatigued condition. There was a significant interaction effect between test part and level of fatigue (P = 0.03).
High ICCs and the absence of systematic variation indicate good test-retest reliability of the figure-of-eight sprint test. The attentional and visual demands for sprint performance, in both a non-fatigued and fatigued condition, can be measured in healthy team-sport athletes with the figure-of-eight sprint test.
To employ retrospective trend analysis in an attempt to provide a layered description of the relative contribution (per credential) of clinical athletic trainers (those without terminal degrees) to authoring scientific literature in the Journal of Athletic Training (JAT). From these data, our secondary purpose was to evaluate trends relative to changes in journal policy and increased educational rigor or professional limitations over the past decade, discussing how they may affect the potential for clinical athletic trainers to contribute to JAT.
Exploratory study design with trend analysis.
Data collection and analysis included a trend evaluation of the credentials of clinical athletic trainer authors in JAT and the teams (by credential) of authorship to determine the credentials of authors who published in JAT.
Longitudinal tabulation of JAT author credentials from 1995 through 2007.
We noted increases in the absolute number of research articles per volume and the number of authors per article and a decrease in the relative percentage of authors who were athletic trainers. The results also suggested that the bachelor of science degree (BS-ATC, representative of clinical athletic trainers without advanced degrees) and Doctor of Medicine (MD) credential may be underrepresented in JAT authorship.
Postgraduate research training may facilitate scientific article contribution by athletic trainers. Continued evolution in the athletic training evidence-based medicine movement should foster research-based mentorship during education. Cultivating collaborations between clinical athletic trainers and research teams may also promote outcomes assessment trials, which will benefit athletic training practices.
research engagement educational models; evidence-based medicine; athletic training research mentorship; athletic training research investigation; author analysis; publication analysis
Elite endurance athletes typically have larger arteries contributing to greater skeletal muscle blood flow, oxygen and nutrient delivery and improved physical performance. Few studies have examined structural and functional properties of arteries in power athletes.
To compare the size and vasoreactivity of the brachial artery of elite power athletes to age-matched controls. It was hypothesized brachial artery diameters of athletes would be larger, have less vasodilation in response to cuff occlusion, but more constriction after a cold pressor test than age-matched controls.
Eight elite power athletes (age = 23±2 years) and ten controls (age = 22±1 yrs) were studied. High-resolution ultrasonography was used to assess brachial artery diameters at rest and following 5 minutes of forearm occlusion (Brachial Artery Flow Mediated Dilation = BAFMD) and a cold pressor test (CPT). Basic fitness measures included a handgrip test and 3-minute step test.
Brachial arteries of athletes were larger (Athletes 5.39±1.51 vs. Controls: 3.73±0.71 mm, p<0.05), had greater vasodilatory (BAFMD%: Athletes: 8.21±1.78 vs. Controls: 5.69±1.56%) and constrictor (CPT %: Athletes: -2.95±1.07 vs. Controls: −1.20±0.48%) responses, compared to controls. Vascular operating range (VOR = Peak dilation+Peak Constriction) was also greater in athletes (VOR: Athletes: 0.55±0.15 vs. Controls: 0.25±0.18 mm, p<0.05). Athletes had superior handgrip strength (Athletes: 55.92±17.06 vs. Controls: 36.77±17.06 kg, p<0.05) but similar heart rate responses at peak (Athletes: 123±16 vs. Controls: 130±25 bpm, p>0.05) and 1 minute recovery (Athletes: 88±21 vs. Controls: 98±26 bpm, p>0.05) following the step test.
Elite power athletes have larger brachial arteries, and greater vasoreactivity (greater vasodilatory and constrictor responses) than age-matched controls, contributing to a significantly greater VOR. These data extend the existence of an ‘athlete’s artery’ as previously shown for elite endurance athletes to elite power athletes, and presents a hypothetical explanation for the functional significance of the ‘power athlete’s artery’.
Objectives—To investigate the associations between natural selection to sports at a young age, continuity of physical activity, and occurrence of coronary heart disease.
Design—Prospective cohort study.
Participants—Former top level male athletes participating at a young age (1920–1965) in different types of sport (endurance (n = 166), power speed (n = 235), "other" (n = 834)) and controls healthy at the age of 20 years (n = 743).
Main outcome measures—Data on the occurrence of coronary heart disease were obtained from death certificates, three nationwide registers, and questionnaire studies in 1985 and 1995, and data on later physical activity were obtained from the questionnaires.
Results—In 1985 all groups of former athletes were more physically active than controls (p<0.001). Despite similar total volumes of physical activity, compared with power speed athletes, former endurance athletes participated more often in vigorous activity (p = 0.006) and had less coronary heart disease (adjusted odds ratio 0.34, 95% confidence interval 0.17 to 0.73; p = 0.004). In 1985 and 1995, both endurance and other athletes had less coronary heart disease than controls. From 1986 to 1995, the incidence of new coronary heart disease was lower among those who participated in vigorous physical activity in 1985.
Conclusions—Both a previous aptitude for endurance athletic events and continuity of vigorous physical activity seem to be associated with protection against coronary heart disease, but an aptitude for power speed events does not give protection against coronary heart disease.
Key Words: coronary heart disease; fitness; genetic selection; physical activity
As a result of inconsistencies in reported findings, controversy exists regarding the effectiveness of balance training for improving functional performance and neuromuscular control. Thus, its practical benefit in athletic training remains inconclusive. Our objective was to evaluate the effectiveness of training interventions in enhancing neuromuscular control and functional performance.
Two independent reviewers performed a literature search in Cochrane Bone, Joint and Muscle Trauma Group Register and Cochrane Controlled Trials Register, MEDLINE, EMBASE, PEDro (Physiotherapy Evidence Database), and SCOPUS.
Randomized controlled trials and controlled trials without randomization with healthy and physically active participants aged up to 40 years old were considered for inclusion. Outcomes of interest were postural control, muscle strength, agility, jump performance, sprint performance, muscle reflex activity, rate of force development, reaction time, and electromyography.
Data of interest were methodologic assessment, training intervention, outcome, timing of the outcome assessment, and results. Standardized mean differences and 95% confidence intervals were calculated when data were sufficient.
In total, 20 randomized clinical trials met the inclusion criteria. Balance training was effective in improving postural sway and functional balance when compared with untrained control participants. Larger effect sizes were shown for training programs of longer duration. Although controversial findings were reported for jumping performance, agility, and neuromuscular control, there are indications for the effectiveness of balance training in these outcomes. When compared with plyometric or strength training, conflicting results or no effects of balance training were reported for strength improvements and changes in sprint performance.
We conclude that balance training can be effective for postural and neuromuscular control improvements. However, as a result of the low methodologic quality and training differences, further research is strongly recommended.
methodologic quality assessment; postural control; motor control
Social support has been identified repeatedly in the literature as being beneficial to individuals suffering from injury or illness. Because of the frequent interaction between athletic trainers and student athletes, the athletic trainer is in a unique position to provide a variety of social support to the athlete. The purpose of the study was (1) to identify the degree to which athletes actually receive each of eight types of social support; (2) to identify the types of social support athletes need or expect to receive from staff and student athletic trainers; and (3) to compare the athletes' satisfaction with the quality of the support received from athletic training staff and students.
Design and Setting:
A questionnaire was used to collect data for this study. It was administered at a Division I university.
Eighty-five student-athletes at a Division I university.
The survey consisted of 24 questions that used a five-point Likert rating scale.
There was no significant difference in the amount of social support received by athletes from staff and student athletic trainers, in athletes' expectations of staff and student athletic trainers with regard to provision of social support, or in the athletes' level of satisfaction with staff and student athletic trainers' provision of social support.
Examined collectively, the findings indicate that athletes do not differentiate between staff and student athletic trainers with regard to the provision of social support. However, finding that athletes do not differentiate between staff and student athletic trainers in this area is significant in itself and has implications for athletic training education programs.
sport psychology; psychology of injury
While intermittent hypoxic training (IHT) has been reported to evoke cellular responses via hypoxia inducible factors (HIFs) but without substantial performance benefits in endurance athletes, we hypothesized that repeated sprint training in hypoxia could enhance repeated sprint ability (RSA) performed in normoxia via improved glycolysis and O2 utilization. 40 trained subjects completed 8 cycling repeated sprint sessions in hypoxia (RSH, 3000 m) or normoxia (RSN, 485 m). Before (Pre-) and after (Post-) training, muscular levels of selected mRNAs were analyzed from resting muscle biopsies and RSA tested until exhaustion (10-s sprint, work-to-rest ratio 1∶2) with muscle perfusion assessed by near-infrared spectroscopy. From Pre- to Post-, the average power output of all sprints in RSA was increased (p<0.01) to the same extent (6% vs 7%, NS) in RSH and in RSN but the number of sprints to exhaustion was increased in RSH (9.4±4.8 vs. 13.0±6.2 sprints, p<0.01) but not in RSN (9.3±4.2 vs. 8.9±3.5). mRNA concentrations of HIF-1α (+55%), carbonic anhydrase III (+35%) and monocarboxylate transporter-4 (+20%) were augmented (p<0.05) whereas mitochondrial transcription factor A (−40%), peroxisome proliferator-activated receptor gamma coactivator 1α (−23%) and monocarboxylate transporter-1 (−36%) were decreased (p<0.01) in RSH only. Besides, the changes in total hemoglobin variations (Δ[tHb]) during sprints throughout RSA test increased to a greater extent (p<0.01) in RSH. Our findings show larger improvement in repeated sprint performance in RSH than in RSN with significant molecular adaptations and larger blood perfusion variations in active muscles.
To provide the reader with an overview of the many causes of sudden cardiac death in young athletes and to present various strategies for preparticipation cardiovascular screening.
A MEDLINE search using the phrase sudden cardiac death and the key word athlete for the years 1980 to 2000.
Sudden cardiac death is a rare event in athletics. More than 20 different causes have been described, but most cases result from a few distinct entities. Most afflicted athletes have no symptoms before death. Many attempts have been made to detect those at risk for sudden cardiac death before athletic participation. At this time, a thorough history and physical examination are the most efficient screening methods for detecting cardiovascular abnormalities. Studies show that the current status of preparticipation cardiovascular screening of high school and college athletes nationwide is poor.
Conclusions and Recommendations:
The use of diagnostic tests to screen for cardiovascular abnormalities is ineffective and inefficient. The most prudent and effective methods of preparticipation screening for cardiovascular abnormalities at this time are a history and physical examination in accordance with the American Heart Association guidelines. Athletic trainers must ensure that their institutions comply with these minimum standards.
sudden cardiac death; hypertrophic cardiomyopathy; preparticipation athletic evaluation; coronary artery anomalies
The aim of this study was to determine the association between the rs6552828 polymorphism in acyl coenzyme A synthetase (ACSL1) and elite endurance athletic status. We studied 82 Caucasian (Spanish) World/Olympic-class endurance male athletes, and a group of sex and ethnically matched healthy young adults (controls, n = 197). The analyses were replicated in a cohort of a different ethnic origin (Chinese of the Han ethnic group), composed of elite endurance athletes (runners) [cases, n = 241 (128 male)] and healthy sedentary adults [controls, n = 504 (267 male)]. In the Spanish cohort, genotype (P = 0.591) and minor allele (A) frequencies were similar in cases and controls (P = 0.978). In the Chinese cohort, genotype (P = 0.973) and minor allele (G) frequencies were comparable in female endurance athletes and sedentary controls (P = 0.881), whereas in males the frequency of the G allele was higher in endurance athletes (0.40) compared with their controls (0.32, P = 0.040). The odds ratio (95%CI) for an elite endurance Chinese athlete to carry the G allele compared with ethnically matched controls was 1.381 (1.015–1.880) (P-value = 0.04). Our findings suggest that the ACSL1 gene polymorphism rs6552828 is not associated with elite endurance athletic status in Caucasians, yet a marginal association seems to exist for the Chinese (Han) male population.
A premature stop codon in ACTN3 resulting in α-actinin-3 deficiency (the ACTN3 577XX genotype) is common in humans and reduces strength, muscle mass, and fast-twitch fiber diameter, but increases the metabolic efficiency of skeletal muscle. Linkage disequilibrium data suggest that the ACTN3 R577X allele has undergone positive selection during human evolution. The allele has been hypothesized to be adaptive in environments with scarce resources where efficient muscle metabolism would be selected. Here we test this hypothesis by using recently developed comparative methods that account for evolutionary relatedness and gene flow among populations. We find evidence that the ACTN3 577XX genotype evolved in association with the global latitudinal gradient. Our results suggest that environmental variables related to latitudinal variation, such as species richness and mean annual temperature, may have influenced the adaptive evolution of ACTN3 577XX during recent human history.
To investigate the associations of body mass index (BMI) and grip strength with objective measures of physical performance (chair rise time, walking speed and balance) including an assessment of sex differences and non-linearity.
Cross-sectional data from eight UK cohort studies (total N = 16 444) participating in the Healthy Ageing across the Life Course (HALCyon) research programme, ranging in age from 50 to 90+ years at the time of physical capability assessment, were used. Regression models were fitted within each study and meta-analysis methods used to pool regression coefficients across studies and to assess the extent of heterogeneity between studies.
Higher BMI was associated with poorer performance on chair rise (N = 10 773), walking speed (N = 9 761) and standing balance (N = 13 921) tests. Higher BMI was associated with stronger grip strength in men only. Stronger grip strength was associated with better performance on all tests with a tendency for the associations to be stronger in women than men; for example, walking speed was higher by 0.43 cm/s (0.14, 0.71) more per kg in women than men. Both BMI and grip strength remained independently related with performance after mutual adjustment, but there was no evidence of effect modification. Both BMI and grip strength exhibited non-linear relations with performance; those in the lowest fifth of grip strength and highest fifth of BMI having particularly poor performance. Findings were similar when waist circumference was examined in place of BMI.
Older men and women with weak muscle strength and high BMI have considerably poorer performance than others and associations were observed even in the youngest cohort (age 53). Although causality cannot be inferred from observational cross-sectional studies, our findings suggest the likely benefit of early assessment and interventions to reduce fat mass and improve muscle strength in the prevention of future functional limitations.