Gediminas Mamkus

The decrease in electrically evoked force production is delayed by a previous bout of stretch–shortening cycle exercise

Aim:  Unaccustomed physical exercise with a large eccentric component is accompanied by muscle damage and impaired contractile function, especially at low stimulation frequencies. A repeated bout of eccentric exercise results in less damage and improved recovery of contractile function. Here we test the hypotheses that (1) a prior stretch–shortening cycle (SSC) exercise protects against impaired muscle function during a subsequent bout of SSC exercise and (2) the protection during exercise is transient and becomes less effective as the exercise progresses.

Cooling leg muscles affects dynamics of indirect indicators of skeletal muscle damage

Objectives: To determine the effect of leg immersion in cold water after stretch-shortening exercise (SSE) on the time-course of indirect indicators of exercise-induced muscle damage (EIMD). Methods: Twenty healthy untrained men twice performed SSE consisting of 100 drop jumps (DJs) from 0.75 m height performed with maximal intensity with an interval of 20 s between the jumps. DJs were performed with counter-movement to 90 degrees angle in the knee and with immediate maximal rebounds. After SSE the subjects legs immediately, as well as after 4 h, 8 h and 24 h, were immersed into a bath filled with water at 15 ± 1 ◦ C. Quadriceps muscle voluntary contraction force (MVCF) and force evoked by electrostimulation (ESF) at different frequencies and at different muscle length, jump height (H), muscle soreness and creatine kinase (CK) activity in the blood were measured before SSE, immediately after SSE and within 72 h of recovery. Results: After stretch-shortening exercise MVCF, ESF and H were significantly ( P< 0.001) decreased and were not restored even after 72 h in the group that did not receive the cooling. Within 24-48 h after SSE the subjects felt great muscle pain and CK activity in their blood was increased ( P< 0.001). The cooling significantly accelerated the disappearance of all these indicators, except for low-frequency fatigue, but only within 24-72 h after SSE. Conclusion: Cold water immersion after SSE accelerates the disappearance of the majority of indirect indicators of EIMD.

Personality Traits and Exercise Capacity in Male Athletes and Non-Athletes:

To investigate the relationships between personality traits and athletic capacity, this study compared a sample of 376 young adult men (169 athletes, 207 non-athletes; M age = 23.8 yr., SD = 3.9). 26 lab-based exercise capacity parameters were measured, as well as the Big Five major personality traits using the NEO Five-Factor Inventory. The results indicated that athletes scored higher than non-athletes for Conscientiousness but scores were not statistically different between groups for other personality traits. Team sport athletes scored higher on Extraversion than endurance athletes. All the personality traits were associated with some of the exercise capacity indices; however, these correlations were rather weak (rs < .2).

Effect of the time of day on central and peripheral fatigue during 2-min maximal voluntary contractions in persons with multiple sclerosis: gender differences

There is a lack of data on fatigue changes within 24h among patients with multiple sclerosis. The purpose of this study was to evaluate the effect of time of day on central and peripheral fatigue during a continuous 2-min maximal voluntary contraction of the quadriceps muscle in women and men with multiple sclerosis (MS). We studied age-matched MS patients (range, 40-50years). The inclusion criteria for patients were: a Kurtzke Expanded Disability Status score and a Fatigue Severity Scale score. We found a significant gender difference in central activation ratio (CAR) in the evening. At the end of the 2-min maximal voluntary contraction (MVC), the voluntary torque decreased by about 65% in men and women with MS in both the morning and evening. We also observed that, in women, CAR decreased markedly during the first 30s in the evening test. The most interesting finding of our study is that central fatigue increased, whereas peripheral fatigue decreased markedly in the evening only in women. It remains unclear why womens central fatigue is greater in the evening than in the morning.

P-87 Acvr1b rs2854464 is associated with quantitative measures of strength/power in lithuanian athletes and controls

Genetic variation is known to account for a large portion of the variation in muscle mass and strength/power in humans. However, few polymorphisms have been conclusively linked with these phenotypes. The myostatin signalling pathway is a source of potential candidates due to its involvement in muscle growth. Variation in myostatin itself has been shown to relate to muscle mass in humans; however, myostatin variation is rare in humans. Other studies have related variation in ACVR1B, a component of the myostatin signalling pathway, to strength/power phenotypes or to athlete status. However, this work still needs replication in large well phenotyped cohorts containing elite athletes. This study aims to replicate previous studies on the relationship between variation in the ACVR1B (rs2854464) G/A polymorphism and strength/power related phenotypes in well phenotyped Lithuanian athletes and controls. Participants DNA samples were from the GELAK cohort. This is comprised of 407 Lithuanians: 84 endurance athletes (END), 126 sprint-strength-power (SSP) and 197 controls (CON). Phenotypes related to stature (height, body mass, BMI), strength (isokinetic peak torque in left and right legs at 30 degrees per second), power (Wingate) and speed (30 m sprint). Genotypes were determined using bespoke RFLPs. Genotype distributions were compared by Chi squared. Odds ratios are reported as mean (lower to upper 95% confidence limits). Associations were established using GLM-ANOVA in Minitab. All GLM analyses were corrected for athlete group and age in months. The control sample was in Hardy-Weinberg equilibrium. Allele frequencies were similar to those reported in 1000 Genomes database. ACVR1B rs2854464 genotype distributions differed between SSP v END (p = 0.015) groups only. AA homozygotes were 2.16 (1.22 to 3.81) times more likely to be END than SSP (p = 0.007). After correction for age and athlete group, ACVR1B rs2854464 variation associated with body mass (p = 0.042, V = 1.36%), BMI (p = 0.016, V = 1.76%) and Wingate total anaerobic work (p = 0.021, V = 1.72%) but not with height, isokinetic peak torque, Wingate peak power or 30 m sprint speed. In all significant relationships, AA homozygotes were significantly weaker than GA heterozygotes. Variation in ACVR1B rs2854464 differs between endurance and strength athletes. It also relates to body mass and quantitative measurements of muscle function. However, in contrast to previous work, carriers of the A-allele are less likely to be strength/power athletes and even after correction for age and athlete group, carriers of the A-allele are still likely to have lower body mass and have lower capacity for anaerobic work. References Windelinckx, et al. (2011) Comprehensive fine mapping of chr12q12-14 and follow-up replication identify activin receptor 1B (ACVR1B) as a muscle strength gene. Eur J Hum Gen 19:208–215. Voisin, et al. (2016) ACVR1B rs2854464 Is Associated with Sprint/Power Athletic Status in a Large Cohort of Europeans but Not Brazilians. PLoS One 11(6):e0156316.