ATP2A2 rs3026468 does not associate with quadriceps contractile properties and acute muscle potentiation in humans

The ATP2A2 gene encodes the SERCA protein required for active calcium reuptake to the sarcoplasmic reticulum in cardiac and slow-twitch skeletal muscle. The ATP2A2 rs3026468 variant has been associated with voluntary strength phenotypes in humans but requires further validation. Here we investigated a homogenous cohort of 80 young, healthy, active Caucasian males who were assessed for maximal isometric strength, voluntary activation, stimulated contractile properties, and muscle potentiation in the quadriceps. A dynamometer was used to record knee extensions, and electrical stimulation was applied to the thigh to elicit a twitch response. DNA was isolated from cheek swabs, and the rs3026468 genotypes were assessed by TaqMan primer quantitative PCR. The results show no association between ATP2A2 rs3026468 variants and muscle strength measures. We conclude there is no effect of the rs3026468 variant in our cohort and that functional influences do not likely contribute to contractile property differences in young healthy men.

Aftereffects of Sustained Convergence: Some Implications of the Eye Muscle Potentiation Hypothesis

Aftereffects of sustained convergence are generally explained as the result of eye muscle potentiation (EMP). Three implications of this hypothesis for aftereffects in distance perception were tested: (i) According to the EMP hypothesis the aftereffects are based on oculomotor distance cues only. The addition of secondary cues during the test period should therefore reduce or eliminate the aftereffects. This expectation was confirmed. (ii) According to the EMP hypothesis the critical variable determining the aftereffect should be the distance of the inspection stimulus from the observer but not from the test stimulus. In confirmation of the expectation the aftereffects of certain inspection stimuli were of the same direction for test stimuli which bounded the range of inspection distances on both sides. (iii) When the aftereffects are based on oculomotor distance cues only, the effect of secondary cues during the test period should remain unchanged when they are present during the inspection period as well. Contrary to this expectation the aftereffects did not depend on the cues available during the test. This suggests that they are based on secondary cues, too, provided they are present during the inspection period.