Genetic variation of maximal velocity and EMG activity

There is a scarcity of studies on genetic variation of essential components of neuromuscular performance, such as maximal velocity and EMG activity during maximal effort. Using the twin model and comparing intrapair differences between monozygotic (MZ) and dizygotic (DZ) twins, we derived for these neuromuscular components heritability estimates (h2), signifying the phenotypic variance due to genetic differences. A group of forty healthy male twins, 10 MZ and 10 DZ pairs, aged 21.5 ± 2.4 and 21.0 ± 2.1 yr, respectively, performed dynamic elbow flexion to assess maximal velocity, and maximal isometric contraction to assess EMG activity of the biceps brachii muscle. Intrapair differences for maximal velocity in MZ and DZ twins were 0.22 ± 0.04 and 0.55 ± 0.17 m·s-1, and intrapair correlations were 0.95 and 0.54, respectively; h2 for maximal velocity was 0.84. Likewise, intrapair differences for EMG activity during maximal isometric contraction were 0.061 ± 0.03 in MZ and 0.176 ± 0.08 mV in DZ; the respective intrapair correlations were 0.93 and 0.46, and h2 was 0.85. In conclusion, maximal velocity of the upper limb, using a simple movement of a single joint and EMG activity during maximal isometric contraction, seems to be highly heritable characteristics in humans. © Georg Thieme Verlag KG Stuttgart

Heritability in Neuromuscular Coordination: Implications for Motor Control Strategies

Purpose: The aim of this study was to assess the relative power of genetic and environmental contribution to the variation observed in neuromuscular coordination. Methods: Using the twin model and comparing intrapair differences between monozygotic (MZ) and dizygotic (DZ) twins, we derived heritability estimates (h2). Forty healthy male twins, 10 MZ and 10 DZ pairs, aged 21.5 ± 2.4 and 21 ± 2.1 yr, respectively, performed a series of elbow flexions in one degree of freedom with different velocities attempting to accurately reach a target. Neuromuscular coordination was evaluated for both accuracy and economy of movement and assessed by kinematics and EMG activity. Results: The heritability in movement accuracy as assessed by the displacement from the target at 70% maximal velocity was 0.87. The accuracy at 30% and 50% of maximal velocity showed that the intrapair variation of MZ twins did not differ significantly from that of DZ twins. High heritability indexes of 0.85 and 0.73 were found for neuromuscular coordination as expressed by movement economy, assessed by the relative EMG activity of biceps long head at 70% and 50% of maximal velocity; no genetic dependence was found for low velocities. Conclusions: In this study, heredity accounted for most of the existing differences in neuromuscular coordination in fast movements. This implies that movement strategies, which are organized in the CNS and control fast movements, are also strongly genetically dependent

Heritability of proprioceptive senses

Heritability studies using the twin model have provided the basis to disentangle genetic and environmental factors that contribute to severa.complex human traits. However, the relative importance of these factors to individual differences in proprioception is largely unknown despite the fact that proprioceptive senses are of great importance, allowing us to respond to stimuli stemming from the space around us and react to altering circumstances. Hence, a total of 44 healthy male twins (11 MZ and 11 DZ pairs), 19-28 yr old, were examined for movement, position, and force sense at the elbow joint, and their heritability estimates wer.computed. Results showed that genetic factors explained 1) 72 and 76% of the total variance of movement sense at the start and the end of the movement, respectively, 2) 60 to 77% of the total variance of position sense, depending on the angle of elbow flexion and whether forearm positioning was active or passive, and 3) 73 and 70% of the total variance of the force sense at 90 and 60° of elbow flexion, respectively. It is concluded that proprioception assessed by these conscious sensations is to a substantial degree genetically dependent, with heritability indexes ranging from 0.60 to 0.77, depending on the task. NEW & NOTEWORTHY Proprioceptive acuity varies among people, but it is not known how much of this variability is due to differences in their genes. This study is the first to report that proprioception, expressed as movement sense, position sense, and force sense, is substantially heritable, and it is conceivable that this may have implications for motor learning and control, neural development, and neurorehabilitation. © 2018 American Physiological Society

Plasticity in human motor cortex is in part genetically determined

Non-technical summary: Neuronal plasticity refers to the ability of the brain to change in response to different experiences. Plasticity varies between people, but it is not known how much of this variability is due to differences in their genes. In humans, plasticity can be probed by a protocol termed paired associative stimulation and the changes in the motor system that are brought about by such stimulation are thought to be due to strengthening synapses which connect different neurons. We examined pairs of sisters which were either genetically identical (monozygotic) or different (dizygotic). We found that the variability within the monozygotic sister pairs was less than the variability within the dizygotic sister pairs. That plasticity in human motor cortex is in a substantial part genetically determined may be relevant for motor learning and neurorehabilitation, such as after stroke.Abstract Brain plasticity refers to changes in the organization of the brain as a result of different environmental stimuli. The aim of this study was to assess the genetic variation of brain plasticity, by comparing intrapair differences between monozygotic (MZ) and dizygotic (DZ) twins. Plasticity was examined by a paired associative stimulation (PAS) in 32 healthy female twins (9 MZ and 7 DZ pairs, aged 22.6 ± 2.7 and 23.8 ± 3.6 years, respectively). Stimulation consisted of low frequency repetitive application of single afferent electric stimuli, delivered to the right median nerve, paired with a single pulse transcranial magnetic stimulation (TMS) for activation of the abductor pollicis brevis muscle (APB). Corticospinal excitability was monitored for 30 min following the intervention. PAS induced an increase in the amplitudes of the motor evoked potentials (MEP) in the resting APB, compared to baseline. Intrapair differences, after baseline normalization, in the MEP amplitudes measured at 25-30 min post-intervention, were almost double for DZ (1.25) in comparison to MZ (0.64) twins (P= 0.036). The heritability estimate for brain plasticity was found to be 0.68. This finding implicates that genetic factors may contribute significantly to interindividual variability in plasticity paradigms. Genetic factors may be important in adaptive brain reorganization involved in motor learning and rehabilitation from brain injury.Neuronal plasticity refers to the ability of the brain to change in response to different experiences. Plasticity varies between people, but it is not known how much of this variability is due to differences in their genes. In humans, plasticity can be probed by a protocol termed paired associative stimulation and the changes in the motor system that are brought about by such stimulation are thought to be due to strengthening synapses which connect different neurons. We examined pairs of sisters which were either genetically identical (monozygotic) or different (dizygotic). We found that the variability within the monozygotic sister pairs was less than the variability within the dizygotic sister pairs. That plasticity in human motor cortex is in a substantial part genetically determined may be relevant for motor learning and neurorehabilitation, such as after stroke. © 2010 The Authors. Journal compilation © 2010 The Physiological Society

The potential role of myostatin and neurotransmission genes in elite sport performances

Elite athletes are those who represent their sport at such major competition as the Olympic Games or World contests. The most outstanding athletes appear to emerge as a result of endogenous biologic characteristics interacting with exogenous influences of the environment, often described as a 'Nature and Nurture' struggle. In this work, we assessed the contribution given by 4 genes involved in muscles development (MSTN) and behavioural insights (5HTT, DAT and MAOA) to athletic performances. As for neurotransmission, 5HTT, DAT and MAOA genes have been considered as directly involved in the management of aggressiveness and anxiety.Genotypes and allelic frequencies of 5HTTLPR, MAOA-u VNTR, DAT VNTR and MSTN K153R were determined in 50 elite athletes and compared with 100 control athletes.In this work we found a significant correlation between the dopamine transporter genotype 9/9 and allele 9 and elite sport performances. On the contrary, no association was found between muscle development regulation or serotonin pathway and elite performances. Our data, for the first time, suggest a strong role of dopamine neurotransmitter in determining sport success, highlighting the role of emotional control and psycological management to reach high-level performances