ACE ID genotype affects blood creatine kinase response to eccentric exercise

Association Between Total Genotype Score and Muscle Injuries in Top-Level Football Players: a Pilot Study

BACKGROUND

Recently, genetic predisposition to injury has become a popular area of research and the association between a few single nucleotide polymorphisms (SNPs) and the susceptibility to develop musculoskeletal injuries has been shown. This pilot study aimed to investigate the combined effect of common gene polymorphisms previously associated with muscle injuries in Italian soccer players.

RESULTS

A total of 64 Italian male top football players (age 23.1 ± 5.5 years; stature 180.2 ± 7.4 cm; weight 73.0 ± 7.9 kg) were genotyped for four gene polymorphisms [ACE I/D (rs4341), ACTN3 c.1729C > T (rs1815739), COL5A1 C > T (rs2722) and MCT1 c.1470A > T (rs1049434)]. Muscle injuries were gathered for 10 years (2009-2019). Buccal swabs were used to obtain genomic DNA, and the PCR method was used to genotype the samples. The combined influence of the four polymorphisms studied was calculated using a total genotype score (TGS: from 0 to 100 arbitrary units; a.u.). A genotype score (GS) of 2 was assigned to the "protective" genotype for injuries, a GS of 1 was assigned to the heterozygous genotype while a GS of 0 was assigned to the "worst" genotype. The distribution of genotype frequencies in the ACE I/D (rs4341), ACTN3 c.1729C > T (rs1815739) and MCT1 c.1470A > T (rs1049434) polymorphisms was different between non-injured and injured football players (p = 0.001; p = 0.016 and p = 0.005, respectively). The incidence of muscle injuries was significantly different among the ACE I/D (rs4341), ACTN3 c.1729C > T (rs1815739) and COL5A1 C > T (rs2722) genotype groups, showing a lower incidence of injuries in the "protective" genotype than "worse" genotype (ACE, p < 0.001; ACTN3, p = 0.005) or intermediate genotype (COL5A1, p = 0.029). The mean TGS in non-injured football players (63.7 ± 13.0 a.u.) was different from that of injured football players (42.5 ± 12.5 a.u., p < 0.001). There was a TGS cut-off point (56.2 a.u.) to discriminate non-injured from injured football players. Players with a TGS beyond this cut-off had an odds ratio of 3.5 (95%CI 1.8-6.8; p < 0.001) to suffer an injury when compared with players with lower TGS.

CONCLUSIONS

These preliminary data suggest that carrying a high number of "protective" gene variants could influence an individual's susceptibility to developing muscle injuries in football. Adapting the training load parameters to the athletes' genetic profile represents today the new frontier of the methodology of training.

A Pilot Study on the Prediction of Non-Contact Muscle Injuries Based on ACTN3 R577X and ACE I/D Polymorphisms in Professional Soccer Athletes

Muscle injuries are among the main reasons for medical leavings of soccer athletes, being a major concern within professional teams and their prevention associated with sport success. Several factors are associated with a greater predisposition to injury, and genetic background is increasingly being investigated. The aim of this study was to analyze whether ACTN3 R577X and ACE I/D polymorphisms are predictors of the incidence and severity of muscle injury in professional soccer athletes from Brazil, individually and in association. Eighty-three professional athletes from the first and second divisions of the Brazilian Championship were evaluated regarding the polymorphisms through blood samples. Nighty-nine muscle injuries were identified during the seasons of 2018, 2019 and 2020 and categorized according to severity. ACTN3 XX individuals had a higher frequency of severe injuries compared to the RX and RR genotypes (p = 0.001), and in the dominant model (compared to RX+RR), with p < 0.001. The trend p-value test showed an increased number of injuries/season following the order XX > RX > RR (p = 0.045). Those with the ACE II genotype had almost 2 fold the number of injuries per season compared to those with the ID+DD genotypes (p = 0.03). Logistic regression showed that the polymorphisms are predictors of the development of severe injury (ACTN3 R577X model with p = 0.004, R2: 0.259; ACE I/D model with p = 0.045, R2: 0.163), where ACTN3 XX individuals were more likely to suffer from severe injury (OR: 5.141, 95% CI: 1.472-17.961, p = 0.010). The combination of the ACTN3 577X allele and the ACE II genotype showed an increased number of injuries per season, enhanced by 100% (1.682 injuries/season versus 0.868 injuries/season, p = 0.016). Our findings suggest that both polymorphisms ACTN3 R577X and ACE I/D (and their interaction) are associated with the susceptibility and severity of non-contact muscle injury in soccer players.

Genetic polymorphisms in CYP19A1 and ESR1 are associated with serum CK activity after prolonged running in men

This study aimed to clarify 1) the influence of genetic polymorphisms in the cytochrome P450 aromatase gene (CYP19A1) on circulating estradiol levels in men and 2) whether estrogen-related genetic polymorphisms, such as the CYP19A1 rs936306 and estrogen receptor-α (ESR1) rs2234693 polymorphisms, predict exercise-induced muscle damage. Serum estradiol levels were examined in young men (n = 167). In a different cohort, serum creatine kinase (CK) activity, an index of skeletal muscle membrane disruption, was analyzed in a 2-days ultramarathon race: baseline, after the first day, and after the second day (114 males and 25 females). Genetic polymorphisms in CYP19A1 rs936306 C/T and ESR1 rs2234693 T/C were analyzed using the TaqMan SNP genotyping assay. Male subjects with the TT genotype of the CYP19A1 polymorphism exhibited significantly higher serum estradiol levels than the C allele carriers. Male runners had significantly higher post-race serum CK activity than female runners. The change in the CK activity during the ultramarathon race was significantly lower in male subjects with the CYP19A1 TT genotype than in those with the CC+CT genotypes, and was correlated with the number of C alleles in ESR1 rs2234693 in male subjects. Furthermore, the genotype scores of these two polymorphisms were significantly correlated with changes in serum CK activity during race (r = ‒0.279, P = 0.003). The results of this study suggest that genetic polymorphisms in CYP19A1 rs936306 influence serum estradiol levels in men, and genetic polymorphisms in CYP19A1 and ESR1 are associated with serum CK activity in men.

Risk factors and future directions for preventing and diagnosing exertional rhabdomyolysis

Exertional rhabdomyolysis may occur when an individual is subjected to strenuous physical exercise. It is occasionally associated with myoglobinuria (i.e. "cola-colored" urine) alongside muscle pain and weakness. The pathophysiology of exertional rhabdomyolysis involves striated muscle damage and the release of cellular components into extracellular fluid and bloodstream. This can cause acute renal failure, electrolyte abnormalities, arrhythmias and potentially death. Exertional rhabdomyolysis is observed in high-performance athletes who are subjected to intense, repetitive and/or prolonged exercise but is also observed in untrained individuals and highly trained or elite groups of military personnel. Several risk factors have been reported to increase the likelihood of the condition in athletes, including: viral infection, drug and alcohol abuse, exercise in intensely hot and humid environments, genetic polymorphisms (e.g. sickle cell trait and McArdle disease) and epigenetic modifications. This article reviews several of these risk factors and proposes screening protocols to identify individual susceptibility to exertional rhabdomyolysis as well as the relevance of proteomics for the evaluation of potential biomarkers of muscle damage.

Polymorphism of the angiotensin converting enzyme gene (ACE-I/D) differentiates the aerobic and speed performance of football players

BACKGROUND

The aim was to evaluate the distribution of ACE-I/D polymorphisms on Brazilian football players performance in aerobic capacity, strength, and speed tests.

METHODS

The participants in this study were 212 Brazilian first division male football players genotyped in DD, ID. or II. Genotyping of DNA from leucocytes was performed using polymerase chain reaction and restriction fragment length polymorphism methods. We evaluated speed using a 30-m sprint test with speed measured at 10 m (V10), 20 m (V20), and 30 m (V30); muscular strength using counter-movement-jump and squat jump tests; and aerobic endurance using the Yo-Yo endurance test. The athletes were ranked in ascending order according to their performance in each test and divided into quartiles: first quartile (0-25%, Weak), second (25-50%, Normal), third (50-75%, Good), and fourth (75-100%, Excellent); these were clustered according to genotype frequency.

RESULTS

We identified significant differences in the V20 test values and in the aerobic capacity test. Higher frequencies of the ACE-DD genotype were observed in the Excellent performance group in the V20. In the aerobic capacity test, higher frequencies of the ACE-II genotype were observed in Excellent and Good performance groups.

CONCLUSIONS

Players with higher performance in anaerobic and aerobic tests are ACE-DD and ACE-II genotypes, respectively.

Effects of uphill high-intensity interval exercise on muscle damage and exercise performance during recovery

BACKGROUND

Active recovery is believed to offer positive benefits related to exercise by improving recovery and potentially managing several symptoms following strenuous exercise. The current study aimed to verify the effects of a session of low-volume and uphill high-intensity interval exercise on muscle soreness and exercise performance within the recovery period after an exercise-induced muscle damage protocol.

METHODS

Thirty-one young physically active subjects completed two identical test sessions following an exercise-induced muscle damage protocol, separated by a three-week period, in which they performed uphill high-intensity interval exercise or a passive recovery. The uphill high-intensity interval exercise consisted of four bouts of 30 seconds at maximum velocity, interspersed by 4 minutes of passive rest on an uphill treadmill. Rating of perceived exertion, muscle soreness, serum concentration of Creatine Kinase, muscle circumference, countermovement jump, sprint time, and 1 repetition maximum strength of quadriceps femoris were measured. The assessments were made for four consecutive days, before the exercise-induced muscle damage protocol and 24, 48, and 72 hours afterwards.

RESULTS

A significant effect of time was found for all the outcome measures, but there were no significant differences between groups either in pain perception, muscle damage variables, nor in performance outcome measures at any point of time (P>0.05).

CONCLUSIONS

Uphill high-intensity interval exercise performed after an exercise-induced muscle damage protocol does not exacerbate muscle soreness or worsens exercise performance in comparison with passive recovery.

Polygenic Profile and Exercise-Induced Muscle Damage by a Competitive Half-Ironman

Del Coso, J, Salinero, JJ, Lara, B, Gallo-Salazar, C, Areces, F, Herrero, D, and Puente, C. Polygenic profile and exercise-induced muscle damage by a competitive half-ironman. J Strength Cond Res 34(5): 1400-1408, 2020-To date, it is still unknown why some individuals develop higher levels of muscle damage than other individuals, despite participating in exercise with comparable levels of physical intensity. The aim of this investigation was to analyze 7 single-nucleotide polymorphisms (SNPs) that are candidates to explain individual variations in the level of muscle damage attained during a half-ironman competition. Using the model of Williams and Folland (2, 1, and 0 points for optimal, intermediate, and suboptimal genotype), we determined the total genotype score from the accumulated combination of 7 SNPs (ACE = 287bp Ins/Del; ACTN3 = p.R577X; creatine kinase, muscle type = NcoI; insulin-like growth factor 2 = C13790G; interleukin-6 = 174G>C; myosin light chain kinase = C37885A; and tumor necrosis factor-α = 308G>A) in 22 experienced triathletes. Before and after the race, a sample of venous blood was obtained to measure serum markers of muscle damage. Two groups of triathletes were established according to their postcompetition serum CK concentration: low CK responders (n = 10; 377 ± 86 U·L) vs. high CK responders (n = 12; 709 ± 136 U·L). At the end of the race, low CK responders had lower serum myoglobin concentrations (384 ± 243 vs. 597 ± 293 ng·ml, p = 0.04). Although the groups were similar in age, anthropometric characteristics, and training habits, total genotype score was higher in low CK responders than in high CK responders (7.7 ± 1.1 vs. 5.5 ± 1.1 point, p < 0.01). A favorable polygenic profile can contribute to reducing the level of muscle damage developed during endurance exercise.

Pathophysiology of exercise-induced muscle damage and its structural, functional, metabolic, and clinical consequences

Extreme or unaccustomed eccentric exercise can cause exercise-induced muscle damage, characterized by structural changes involving sarcomere, cytoskeletal, and membrane damage, with an increased permeability of sarcolemma for proteins. From a functional point of view, disrupted force transmission, altered calcium homeostasis, disruption of excitation-contraction coupling, as well as metabolic changes bring about loss of strength. Importantly, the trauma also invokes an inflammatory response and clinically presents itself by swelling, decreased range of motion, increased passive tension, soreness, and a transient decrease in insulin sensitivity. While being damaging and influencing heavily the ability to perform repeated bouts of exercise, changes produced by exercise-induced muscle damage seem to play a crucial role in myofibrillar adaptation. Additionally, eccentric exercise yields greater hypertrophy than isometric or concentric contractions and requires less in terms of metabolic energy and cardiovascular stress, making it especially suitable for the elderly and people with chronic diseases. This review focuses on our current knowledge of the mechanisms underlying exercise-induced muscle damage, their dependence on genetic background, as well as their consequences at the structural, functional, metabolic, and clinical level. A comprehensive understanding of these is a prerequisite for proper inclusion of eccentric training in health promotion, rehabilitation, and performance enhancement.

Myostatin A55T Genotype is Associated with Strength Recovery Following Exercise-Induced Muscle Damage

Myostatin A55T genotype is one of the candidates showing inter-individual variation in skeletal muscle phenotypes. The aim of this study was to investigate the effect of the myostatin A55T genotype on markers of muscle damage after eccentric exercise. Forty-eight young, healthy male college students (age = 24.8 ± 2.2 years, height = 176.7 ± 5.3 cm, weight = 73.7 ± 8.3 kg) were enrolled in this study, and muscle damage was induced through 50 reps of maximal eccentric muscle contraction. As markers of muscle damage, maximal isometric strength (MIS), muscle soreness, creatine kinase (CK), and aspartate transaminase (AST) were measured. Myostatin A55T genotypes were classified into homozygous myostatin A55T allele (AA, n = 34, 72%), heterozygous myostatin A55T allele (AT, n = 13, 26%), and homozygous mutant carriers (TT, n = 1, 2%). After eccentric exercise, the subjects with heterozygous for AT showed markedly quicker MIS recovery compared to the AA group (p = 0.042). However, there were no significant variations in muscle soreness (p = 0.379), CK (p = 0.955), and AST (p = 0.706) among the groups. These results suggest that AT in myostatin A55T genotype may be associated with quicker strength recovery following exercise-induced muscle damage.

Angiotensin converting enzyme: A review on expression profile and its association with human disorders with special focus on SARS-CoV-2 infection

Angiotensin-converting enzyme (ACE) and its homologue, ACE2, have been mostly associated with hypertensive disorder. However, recent pandemia of SARS-CoV-2 has put these proteins at the center of attention, as this virus has been shown to exploit ACE2 protein to enter cells. Clear difference in the response of affected patients to this virus has urged researchers to find the molecular basis and pathophysiology of the cell response to this virus. Different levels of expression and function of ACE proteins, underlying disorders, consumption of certain medications and the existence of certain genomic variants within ACE genes are possible explanations for the observed difference in the response of individuals to the SARS-CoV-2 infection. In the current review, we discuss the putative mechanisms for this observation.

Eccentric Muscle Contractions: Risks and Benefits

Eccentric contractions, characterized by the lengthening of the muscle-tendon complex, present several unique features compared with other types of contractions, which may lead to unique adaptations. Due to its specific physiological and mechanical properties, there is an increasing interest in employing eccentric muscle work for rehabilitation and clinical purposes. However, unaccustomed eccentric exercise is known to cause muscle damage and delayed pain, commonly defined as “Delayed-Onset Muscular Soreness” (DOMS). To date, the most useful preventive strategy to avoid these adverse effects consists of repeating sessions involving submaximal eccentric contractions whose intensity is progressively increased over the training. Despite an increased number of investigations focusing on the eccentric contraction, a significant gap still remains in our understanding of the cellular and molecular mechanisms underlying the initial damage response and subsequent adaptations to eccentric exercise. Yet, unraveling the molecular basis of exercise-related muscle damage and soreness might help uncover the mechanistic basis of pathological conditions as myalgia or neuromuscular diseases. In addition, a better insight into the mechanisms governing eccentric training adaptations should provide invaluable information for designing therapeutic interventions and identifying potential therapeutic targets.

Perspectives on Exertional Rhabdomyolysis

Exertional (exercise-induced) rhabdomyolysis is a potentially life threatening condition that has been the subject of research, intense discussion, and media attention. The causes of rhabdomyolysis are numerous and can include direct muscle injury, unaccustomed exercise, ischemia, extreme temperatures, electrolyte abnormalities, endocrinologic conditions, genetic disorders, autoimmune disorders, infections, drugs, toxins, and venoms. The objective of this article is to review the literature on exertional rhabdomyolysis, identify precipitating factors, and examine the role of the dietary supplement creatine monohydrate. PubMed and SPORTDiscus databases were searched using the terms rhabdomyolysis, muscle damage, creatine, creatine supplementation, creatine monohydrate, and phosphocreatine. Additionally, the references of papers identified through this search were examined for relevant studies. A meta-analysis was not performed. Although the prevalence of rhabdomyolysis is low, instances still occur where exercise is improperly prescribed or used as punishment, or incomplete medical history is taken, and exertional rhabdomyolysis occurs. Creatine monohydrate does not appear to be a precipitating factor for exertional rhabdomyolysis. Healthcare professionals should be able to recognize the basic signs of exertional rhabdomyolysis so prompt treatment can be administered. For the risk of rhabdomyolysis to remain low, exercise testing and prescription must be properly conducted based on professional standards.

Using blood lactate concentration to predict muscle damage and jump performance response to maximal stretch-shortening cycle exercise

BACKGROUND

It is well known that eccentric muscle contractions induce delayed onset muscle soreness (DOMS) and exertional rhabdomyolysis (ERB), both of which are related to high blood levels of muscle damage markers after exercise. Creatine kinase (CK) is, together with some other markers (i.e. myoglobin, α-actin, skeletal troponin), widely used in determination of muscle damage. Moreover, DOMS after eccentric exercise has been shown to be associated with altered blood lactate concentration after subsequent submaximal or maximal cycling exercise. However, it is unknown whether blood lactate can predict muscle damage levels after maximal stretch-shortening cycle (SSC) exercise, as due to the differences in types of contractions between the eccentric and SSC protocol. Additionally, we determined the association between blood lactate concentration and CMJ performance after such a protocol.

METHODS

Forty-three healthy, physically active young men completed a plyometric training session consisting of maximal countermovement jumps (CMJ) to failure. The blood creatine kinase (CK), myoglobin (Mb) and aspartate aminotransferase (AST) samples were taken pre- and 48 hours post-exercise. Blood lactate concentration was determined directly post-exercise.

RESULTS

There was a significant correlation between blood lactate concentration (post) and blood CK (P=0.027), Mb (P=0.007) and AST (P=0.024) (48 hours post), which means that higher blood lactate concentration is associated with higher muscle damage values after exercise. No correlation was found between blood lactate concentration (post) and performance loss which was expressed by the decrease in maximum CMJ height 5 minutes post-exercise.

CONCLUSIONS

Blood lactate concentration could be used as a predictor of muscle damage levels after maximal SSC exercise, which supports the results found in other studies, although after eccentric exercise. However, it cannot predict acute performance loss in jump height.

Aqua Cycling Does Not Affect Recovery of Performance, Damage Markers, and Sensation of Pain

Wahl, P, Sanno, M, Ellenberg, K, Frick, H, Böhm, E, Haiduck, B, Goldmann, J-P, Achtzehn, S, Brüggemann, G-P, Mester, J, and Bloch, W. Aqua cycling does not affect recovery of performance, damage markers, and sensation of pain. J Strength Cond Res 31(1): 162-170, 2017-To examine the effects of aqua cycling (AC) vs. passive recovery (P) on performance, markers of muscle damage, delayed onset of muscle soreness (DOMS), and the persons perceived physical state (PEPS) after 300 countermovement jumps (CMJs). Twenty male participants completed 300 CMJs. Afterward, they were randomly assigned to either the P group or the AC group, the latter performing 30 minutes of AC. Before, directly after the 300 CMJs, after the recovery session, and up to 72 hours post, performance of leg extensor muscles, damage markers, the PEPS, and DOMS were measured. Jumping height during 300 CMJs significantly decreased in both groups (AC: 13.4% and P: 14.6%). Maximal isometric strength (AC: 21% and P: 22%) and dynamic fatigue test (AC: 35% and P: 39%) of leg extensor muscles showed significant decreases in both groups. Myoglobin, creatine kinase, and lactate dehydrogenase significantly increased over time in both groups. Each of the 4 dimensions of the PEPS and DOMS showed significant changes over time. However, no significant differences between both groups were found for any of the parameters. Coaches and athletes should be aware that vertical jumping-induced fatigue decreases the ability to generate maximal isometric and submaximal dynamic force for more than 3 days after training. A single 30-minute session of AC was not able to attenuate the effects on muscular performance, markers of muscle damage, DOMS, or the PEPS compared with passive rest.

Optimum polygenic profile to resist exertional rhabdomyolysis during a marathon

Purpose

Exertional rhabdomyolysis can occur in individuals performing various types of exercise but it is unclear why some individuals develop this condition while others do not. Previous investigations have determined the role of several single nucleotide polymorphisms (SNPs) to explain inter-individual variability of serum creatine kinase (CK) concentrations after exertional muscle damage. However, there has been no research about the interrelationship among these SNPs. The purpose of this investigation was to analyze seven SNPs that are candidates for explaining individual variations of CK response after a marathon competition (ACE = 287bp Ins/Del, ACTN3 = p.R577X, CKMM = NcoI, IGF2 = C13790G, IL6 = 174G>C, MLCK = C37885A, TNFα = 308G>A).

Methods

Using Williams and Folland’s model, we determined the total genotype score from the accumulated combination of these seven SNPs for marathoners with a low CK response (n = 36; serum CK <400 U·L^-1) vs. marathoners with a high CK response (n = 31; serum CK ≥400 U·L^-1).

Results

At the end of the race, low CK responders had lower serum CK (290±65 vs. 733±405 U·L^-1; P<0.01) and myoglobin concentrations (443±328 vs. 1009±971 ng·mL^-1, P<0.01) than high CK responders. Although the groups were similar in age, anthropometric characteristics, running experience and training habits, total genotype score was higher in low CK responders than in high CK responders (5.2±1.4 vs. 4.4±1.7 point, P = 0.02).

Conclusion

Marathoners with a lower CK response after the race had a more favorable polygenic profile than runners with high serum CK concentrations. This might suggest a significant role of genetic polymorphisms in the levels of exertional muscle damage and rhabdomyolysis. Yet other SNPs, in addition to exercise training, might also play a role in the values of CK after damaging exercise.

Exertional rhabdomyolysis: physiological response or manifestation of an underlying myopathy?

Exertional rhabdomyolysis is characterised by muscle breakdown associated with strenuous exercise or normal exercise under extreme circumstances. Key features are severe muscle pain and sudden transient elevation of serum creatine kinase (CK) levels with or without associated myoglobinuria. Mild cases may remain unnoticed or undiagnosed. Exertional rhabdomyolysis is well described among athletes and military personnel, but may occur in anybody exposed to unaccustomed exercise. In contrast, exertional rhabdomyolysis may be the first manifestation of a genetic muscle disease that lowers the exercise threshold for developing muscle breakdown. Repeated episodes of exertional rhabdomyolysis should raise the suspicion of such an underlying disorder, in particular in individuals in whom the severity of the rhabdomyolysis episodes exceeds the expected response to the exercise performed. The present review aims to provide a practical guideline for the acute management and postepisode counselling of patients with exertional rhabdomyolysis, with a particular emphasis on when to suspect an underlying genetic disorder. The pathophysiology and its clinical features are reviewed, emphasising four main stepwise approaches: (1) the clinical significance of an acute episode, (2) risks of renal impairment, (3) clinical indicators of an underlying genetic disorders and (4) when and how to recommence sport activity following an acute episode of rhabdomyolysis. Genetic backgrounds that appear to be associated with both enhanced athletic performance and increased rhabdomyolysis risk are briefly reviewed.

Genetic variation and exercise-induced muscle damage: implications for athletic performance, injury and ageing

Prolonged unaccustomed exercise involving muscle lengthening (eccentric) actions can result in ultrastructural muscle disruption, impaired excitation-contraction coupling, inflammation and muscle protein degradation. This process is associated with delayed onset muscle soreness and is referred to as exercise-induced muscle damage. Although a certain amount of muscle damage may be necessary for adaptation to occur, excessive damage or inadequate recovery from exercise-induced muscle damage can increase injury risk, particularly in older individuals, who experience more damage and require longer to recover from muscle damaging exercise than younger adults. Furthermore, it is apparent that inter-individual variation exists in the response to exercise-induced muscle damage, and there is evidence that genetic variability may play a key role. Although this area of research is in its infancy, certain gene variations, or polymorphisms have been associated with exercise-induced muscle damage (i.e. individuals with certain genotypes experience greater muscle damage, and require longer recovery, following strenuous exercise). These polymorphisms include ACTN3 (R577X, rs1815739), TNF (-308 G>A, rs1800629), IL6 (-174 G>C, rs1800795), and IGF2 (ApaI, 17200 G>A, rs680). Knowing how someone is likely to respond to a particular type of exercise could help coaches/practitioners individualise the exercise training of their athletes/patients, thus maximising recovery and adaptation, while reducing overload-associated injury risk. The purpose of this review is to provide a critical analysis of the literature concerning gene polymorphisms associated with exercise-induced muscle damage, both in young and older individuals, and to highlight the potential mechanisms underpinning these associations, thus providing a better understanding of exercise-induced muscle damage.

The relationship of creatine kinase variability with body composition and muscle damage markers following eccentric muscle contractions

[Purpose]

The purpose of the study was to investigate the relationship between CK variability and body composition and muscle damage markers following eccentric exercise.

[Methods]

Total 119 healthy male subjects were recruited to perform 50 eccentric contractions consisted of 2 sets of 25 contractions. Then, blood creatine kinase (CK) activity was analyzed to divide into three groups based on their CK activity levels. Maximum isometric strength (MIS), muscle soreness (SOR) and body composition data were obtained before and after exercise.

[Results]

The results showed that high CK responders had a significant decrease in MIS (p<0.001) and greater SOR (p<0.01) following eccentric exercise compared to low CK responders. Percent body fat was also higher in high responders compared to low responders (p=0.014). Peak CK activity was significantly correlated with MIS and SOR but no correlation with % body fat, muscle mass, and body mass index.

[Conclusion]

CK variability following eccentric exercise is closely related to MIS and SOR and % body fat may be a potent factor for CK variability.

Rhabdomyolysis: a genetic perspective

Rhabdomyolysis (RM) is a clinical emergency characterized by fulminant skeletal muscle damage and release of intracellular muscle components into the blood stream leading to myoglobinuria and, in severe cases, acute renal failure. Apart from trauma, a wide range of causes have been reported including drug abuse and infections. Underlying genetic disorders are also a cause of RM and can often pose a diagnostic challenge, considering their marked heterogeneity and comparative rarity.

In this paper we review the range of rare genetic defects known to be associated with RM. Each gene has been reviewed for the following: clinical phenotype, typical triggers for RM and recommended diagnostic approach. The purpose of this review is to highlight the most important features associated with specific genetic defects in order to aid the diagnosis of patients presenting with hereditary causes of recurrent RM.

Association of Angiotensin Converting Enzyme I/D and α-actinin-3 R577X Genotypes with Growth Factors and Physical Fitness in Korean Children

This study analyzed the differences in aerobic and anaerobic exercise ability and growth-related indicators, depending on the polymorphism of the ACE and the ACTN3 genes, to understand the genetic influence of exercise ability in the growth process of children. The subjects of the study consisted of elementary school students (n=856, age 10.32±0.07 yr). The anthropometric parameters, physical fitness and growth factors were compared among groups of the ACE I/D or the ACTN3 R577X polymorphisms. There were no significant differences between the anthropometric parameters, physical fitness and growth factors for the ACE gene ID or the ACTN3 gene R577X polymorphism. However, the DD type of ACE gene was highest in the side step test (p<0.05), and the DD type was significantly higher than the II+ID type (p<0.05) in the early bone age. The combined group of the ACE gene II+ID and the ACTN3 gene XX type significantly showed lower early bone age (p< 0.05). This study did not find any individual or compounding effects of the polymorphism in the ACE I/D or the ACTN3 R577X polymorphisms on the anthropometric parameters, physical fitness and growth factors of Korean children. However, the exercise experience and the DD type of the ACE gene may affect the early maturity of the bones.

Genetic polymorphisms associated with exertional rhabdomyolysis

Exertional rhabdomyolysis (ER) occurs in young, otherwise healthy, individuals principally during strenuous exercise, athletic, and military training. Although many risk factors have been offered, it is unclear why some individuals develop ER when participating in comparable levels of physical exertion under identical environmental conditions and others do not. This study investigated possible genetic polymorphisms that might help explain ER. DNA samples derived from a laboratory-based study of persons who had never experienced an episode of ER (controls) and clinical ER cases referred for testing over the past several years were analyzed for single nucleotide polymorphisms (SNPs) in candidate genes. These included angiotensin I converting enzyme (ACE), α-actinin-3 (ACTN3), creatine kinase muscle isoform (CKMM), heat shock protein A1B (HSPA1B), interleukin 6 (IL6), myosin light chain kinase (MYLK), adenosine monophosphate deaminase 1 (AMPD1), and sickle cell trait (HbS). Population included 134 controls and 47 ER cases. The majority of ER cases were men (n = 42/47, 89.4 %); the five women with ER were Caucasian. Eighteen African Americans (56.3 %) were ER cases. Three SNPs were associated with ER: CKMM Ncol, ACTN3 R577X, and MYLK C37885A. ER cases were 3.1 times more likely to have the GG genotype of CKMM (odds ratio/OR = 3.1, confidence interval/CI 1.33-7.10), 3.0 times for the XX genotype of ACTN3 SNP (OR = 2.97, CI 1.30-3.37), and 5.7 times for an A allele of MYLK (OR = 21.35, CI 2.60-12.30). All persons with HbS were also ER cases. Three distinct polymorphisms were associated with ER. Further work will be required to replicate these findings and determine the mechanism(s) whereby these variants might confer susceptibility.

Rhabdomyolysis in the US Active Duty Army, 2004-2006

PURPOSE

Rhabdomyolysis (RM) is a skeletal muscle disorder resulting in severe cellular injury caused by vigorous physical activity and other systemic etiologies. RM is associated with significant morbidity, such as acute renal failure, and can be fatal. RM that occurs in the US Active Duty Army (ADA) results in time lost from training, deployment, and combat. We sought to systemically describe the epidemiology of ADA clinical RM by quantifying RM in terms of absolute numbers, examine rate trends, and identify soldiers at elevated risk.

METHODS

We used data from the Total Army Injury and Health Outcomes Database to calculate yearly RM rates in the overall ADA, as well as adjusted RM rates within soldier subpopulations for 2003-2006.

RESULTS

During this period, the absolute numbers of clinically diagnosed ADA RM ranged between 382 and 419 cases per year. Annual rates were 7-8 per 10,000, which is 300%-400% higher than the estimated US civilian population (2 per 10,000). In soldiers with a history of a prior heat injury, RM rates climbed to 52-86 per 10,000, a 7- to 11-fold increase. Increased RM rates were seen in soldiers who are male, African American, younger, less educated, and with a shorter length of service. Approximately 8% of yearly ADA RM cases resulted in acute renal failure, an estimate lower than that for the US civilian population.

CONCLUSIONS

Our findings suggest that rates of RM are higher in the ADA than in the US civilian population. Rates remained fairly stable; however, relative to other ADA soldiers, those with prior heat injury, who are African American, or who have a length of service of less than 90 d are at the highest risk for RM development.

Creatine-kinase- and exercise-related muscle damage implications for muscle performance and recovery

The appearance of creatine kinase (CK) in blood has been generally considered to be an indirect marker of muscle damage, particularly for diagnosis of medical conditions such as myocardial infarction, muscular dystrophy, and cerebral diseases. However, there is controversy in the literature concerning its validity in reflecting muscle damage as a consequence of level and intensity of physical exercise. Nonmodifiable factors, for example, ethnicity, age, and gender, can also affect enzyme tissue activity and subsequent CK serum levels. The extent of effect suggests that acceptable upper limits of normal CK levels may need to be reset to recognise the impact of these factors. There is a need for standardisation of protocols and stronger guidelines which would facilitate greater scientific integrity. The purpose of this paper is to examine current evidence and opinion relating to the release of CK from skeletal muscle in response to physical activity and examine if elevated concentrations are a health concern.

Muscle fatigue experienced during maximal eccentric exercise is predictive of the plasma creatine kinase (CK) response

Unaccustomed eccentric exercise may cause skeletal muscle damage with an increase in plasma creatine kinase (CK) activity. Although the wide variability among individuals in CK response to standardized lengthening contractions has been well described, the reasons underlying this phenomenon have not yet been understood. Therefore, this study investigated a possible correlation of the changes in muscle damage indirect markers after an eccentric exercise with the decline in muscle performance during the exercise. Twenty-seven healthy untrained male subjects performed three sets of 30 maximal isokinetic eccentric contractions of the knee extensors. The muscular work was recorded using an isokinetic dynamometer to assess muscle fatigue by means of various fatigue indices. Plasma CK activity, muscle soreness, and stiffness were measured before (pre) and one day after (post) exercise. The eccentric exercise bout induced significant changes of the three muscle damage indirect markers. Large inter-subject variability was observed for all criteria measured. More interestingly, the log (CK(post) /CK(pre)) and muscle stiffness appeared to be closely correlated with the relative work decrease (r = 0.84, r(2)  = 0.70 and r = 0.75, r(2)  = 0.56, respectively). This is the first study to propose that the muscle fatigue profile during maximal eccentric protocol could predict the magnitude of the symptoms associated with muscle damage in humans.

The ACE gene and human performance: 12 years on

Some 12 years ago, a polymorphism of the angiotensin I-converting enzyme (ACE) gene became the first genetic element shown to impact substantially on human physical performance. The renin-angiotensin system (RAS) exists not just as an endocrine regulator, but also within local tissue and cells, where it serves a variety of functions. Functional genetic polymorphic variants have been identified for most components of RAS, of which the best known and studied is a polymorphism of the ACE gene. The ACE insertion/deletion (I/D) polymorphism has been associated with improvements in performance and exercise duration in a variety of populations. The I allele has been consistently demonstrated to be associated with endurance-orientated events, notably, in triathlons. Meanwhile, the D allele is associated with strength- and power-orientated performance, and has been found in significant excess among elite swimmers. Exceptions to these associations do exist, and are discussed. In theory, associations with ACE genotype may be due to functional variants in nearby loci, and/or related genetic polymorphism such as the angiotensin receptor, growth hormone and bradykinin genes. Studies of growth hormone gene variants have not shown significant associations with performance in studies involving both triathletes and military recruits. The angiotensin type-1 receptor has two functional polymorphisms that have not been shown to be associated with performance, although studies of hypoxic ascent have yielded conflicting results. ACE genotype influences bradykinin levels, and a common gene variant in the bradykinin 2 receptor exists. The high kinin activity haplotye has been associated with increased endurance performance at an Olympic level, and similar results of metabolic efficiency have been demonstrated in triathletes. Whilst the ACE genotype is associated with overall performance ability, at a single organ level, the ACE genotype and related polymorphism have significant associations. In cardiac muscle, ACE genotype has associations with left ventricular mass changes in response to stimulus, in both the health and diseased states. The D allele is associated with an exaggerated response to training, and the I allele with the lowest cardiac growth response. In light of the I-allele association with endurance performance, it seems likely that other regulatory mechanisms exist. Similarly in skeletal muscle, the D allele is associated with greater strength gains in response to training, in both healthy individuals and chronic disease states. As in overall performance, those genetic polymorphisms related to the ACE genotype, such as the bradykinin 2 gene, also influence skeletal muscle strength. Finally, the ACE genotype may influence metabolic efficiency, and elite mountaineers have demonstrated an excess of I alleles and I/I genotype frequency in comparison to controls. Interestingly, this was not seen in amateur climbers. Corroboratory evidence exists among high-altitude settlements in both South America and India, where the I allele exists in greater frequency in those who migrated from the lowlands. Unfortunately, if the ACE genotype does influence metabolic efficiency, associations with peak maximal oxygen consumption have yet to be rigorously demonstrated. The ACE genotype is an important but single factor in the determinant of sporting phenotype. Much of the mechanisms underlying this remain unexplored despite 12 years of research.

Molecular genetic studies of gene identification for sarcopenia

Sarcopenia, which is characterized by a progressive decrease of skeletal muscle mass and function with aging, is closely related to several common diseases (such as cardiovascular and airway diseases) and functional impairment/disability. Strong genetic determination has been reported for muscle mass and muscle strength, two most commonly recognized and studied risk phenotypes for sarcopenia, with heritability ranging from 30 to 85% for muscle strength and 45-90% for muscle mass. Sarcopenia has been the subject of increasing genetic research over the past decade. This review is designed to comprehensively summarize the most important and representative molecular genetic studies designed to identify genetic factors associated with sarcopenia. We have methodically reviewed whole-genome linkage studies in humans, quantitative trait loci mapping in animal models, candidate gene association studies, newly reported genome-wide association studies, DNA microarrays and microRNA studies of sarcopenia or related skeletal muscle phenotypes. The major results of each study are tabulated for easy comparison and reference. The findings of representative studies are discussed with respect to their influence on our present understanding of the genetics of sarcopenia. This is a comprehensive review of molecular genetic studies of gene identification for sarcopenia, and an overarching theme for this review is that the currently accumulating results are tentative and occasionally inconsistent and should be interpreted with caution pending further investigation. Consequently, this overview should enhance recognition of the need to validate/replicate the genetic variants underlying sarcopenia in large human cohorts and animal. We believe that further progress in understanding the genetic etiology of sarcopenia will provide valuable insights into important fundamental biological mechanisms underlying muscle physiology that will ultimately lead to improved ability to recognize individuals at risk for developing sarcopenia and our ability to treat this debilitating condition.

Does the ACE I/D polymorphism, alone or in combination with the ACTN3 R577X polymorphism, influence muscle power phenotypes in young, non-athletic adults?

We investigated the association of the angiotensin converting enzyme gene (ACE) insertion/deletion (I/D) polymorphism, alone or in combination with the α-actinin-3 gene (ACTN3) R577X polymorphism, with jumping (vertical squat and counter-movement jump tests) and sprint ability (30 m dash) in non-athletic, healthy young adults [N = 281 (214 male), mean (SD) age 21 (2) years]. We did not observe any effect of the ACE I/D polymorphism on study phenotypes. We repeated the analyses separately in men and women and the results did not materially change. Likewise, the mean estimates of the study phenotypes were similar in subjects with the genotype combinations ACE II + ID and ACTN3 XX or ACE DD and ACTN3 RR + RX. We found no association between the ACE DD and ACTN3 RR + RX genotype combination and performance (≥90th of the sex-specific percentile). In summary, though the ACE I/D polymorphism is a strong candidate to modulate some exercise-related phenotypes or athletic performance status, this polymorphism, alone or in combination with the ACTN3 R577X polymorphism, does not seem to exert a major influence in the muscle 'explosive' power of young healthy adults, as assessed during multi-joint exercise tests.

Relationship between serum creatine kinase activity following exercise-induced muscle damage and muscle fibre composition

In this study, we examined the relationship between serum creatine kinase activity following exercise-induced muscle damage and muscle fibre composition. Seventeen untrained males volunteered and underwent a .[Vdot]O2max test, Wingate test, and an exercise-induced muscle damage protocol. Muscle soreness and blood samples were recorded before, immediately after, and 24, 48, 72, and 96 h after exercise. Biopsy samples from the vastus lateralis were collected one week after exercise-induced muscle damage and were assessed for muscle fibre composition. There was no significant relationship (P > 0.05) between muscle fibre composition and creatine kinase activity. A significant positive correlation (P < 0.05) was observed between soreness 48 h after exercise and type II and IIb fibres, and a significant negative correlation (P < 0.05) was observed between soreness 48 h after exercise and type I muscle fibres. Significant positive correlations were observed between soreness 48 h after exercise and the fatigue index, relative average power, and relative anaerobic capacity. Our results suggest that creatine kinase activity following exercise-induced muscle damage may not be related to muscle fibre proportions, and higher post-exercise muscular pain may be related to a predominance of type II muscle fibres and higher anaerobic capabilities.

CCL2 and CCR2 polymorphisms are associated with markers of exercise-induced skeletal muscle damage

Novel eccentric (lengthening contraction) exercise typically results in muscle damage, which manifests as prolonged muscle dysfunction, delayed onset muscle soreness, and leakage of muscle proteins into circulation. There is a large degree of variability in the damage response of individuals to eccentric exercise, with higher responders at risk for potentially fatal rhabdomyolysis. We hypothesized that single nucleotide polymorphisms (SNPs) in chemokine ligand 2 ( CCL2) and its receptor chemokine receptor 2 ( CCR2) associate with the high degrees of variability in the muscle damage response. We based this hypothesis on CCL2's roles in macrophage and satellite cell signaling in injured muscle. DNA was obtained from 157 untrained men and women following maximal eccentric exercise. Strength loss, soreness, serum creatine kinase (CK), and myoglobin levels before and during recovery from a single exercise bout were tested for association with 16 SNPs in CCL2 and CCR2. The rare alleles for rs768539 and rs3918358 (CCR2) were significantly ( P < 0.05) associated with lower preexercise strength in men, whereas CCL2 SNPs (rs13900, rs1024611, and rs1860189) and CCR2 (rs1799865) were associated with altered preexercise CK levels in women. During recovery, the rs3917878 genotype ( CCL2) was associated with attenuated strength recovery in men and an elevated CK response in women. CCR2 variants were associated with slower strength recovery in women (rs3918358) and elevated soreness (rs1799865) across all subjects. In summary, we found that SNPs in CCL2 and CCR2 are associated with exercise-induced muscle damage and that the presence of certain variants may result in an exaggerated damage response to strenuous exercise.

IL6 (-174) and TNFA (-308) promoter polymorphisms are associated with systemic creatine kinase response to eccentric exercise

Exertional rhabdomyolysis is a complex and poorly understood entity. The inflammatory system has an important role in muscle injury and repair. Serum creatine kinase (CK) is often used as systemic biomarker representing muscle damage. Considerable variation exists in CK response between different subjects. Genetic elements may act as predisposition factors for exertional rhabdomyolysis. Based on their biological activity, we hypothesized that in healthy subjects IL6 G-174C and TNFA G-308A promoter polymorphisms would be associated with CK response to exercise. We determined serum CK activity pre- and post-maximal eccentric contractions of the elbow flexor muscles. IL6 G-174C and TNFA G-308A genotypes were analyzed for possible relationship with changes in serum CK activity. IL6 G-174C genotype was associated with CK activity in a dose-dependent fashion. Subjects with one or more of the -174C allele had a greater increase and higher peak CK values than subjects homozygous for the G allele (mean +/- SE U/L: GG, 2,604 +/- 821; GC, 7,592 +/- 1,111; CC, 8,403 +/- 3,849, ANOVA P = 0.0003 for GG + GC genotypes versus CC genotype, P = 0.0005 for linear trend). IL6-174CC genotype was associated with a greater than threefold increased risk of massive CK response (adjusted odds ratio 3.29, 95% confidence interval 1.27-7.85, P = 0.009). A milder association (P = 0.06) was noted between TNFA G-308A genotype and CK activity. In conclusion, we found a strong association of the IL6 G-174C genotype with systemic CK response to strenuous exercise. Data suggest that homozygosity for the IL6-174C allele is a clinically important risk factor for exercise-induced muscle injury, further supporting the central role of cytokines in the reactive inflammatory process of muscle damage and repair.