RESUMEN
The effect of emphasizing speed or accuracy on the learning of a high speed-high accuracy skill, the fastpitch softball pitch was investigated. 26 10- and 11-yr.-old girls were randomly assigned to two groups receiving feedback on speed of throwing or accuracy of throwing during a 6-wk. training. Measurements of speed and accuracy were made and recorded on all participants at each practice session and a videotape of their pitching technique was also made at each session. Data were subjected to 2 x 3 (2 groups by 3 testing times) repeated-measures analyses of variance. The speed group threw faster and with better technique during the study and was able to maintain speed and accuracy in the reversed test condition.
Asunto(s)
Béisbol/educación , Aprendizaje , Destreza Motora , Análisis de Varianza , Fenómenos Biomecánicos , Niño , Retroalimentación , Femenino , Humanos , Práctica Psicológica , Distribución AleatoriaRESUMEN
Variation at 23 putative enzyme-coding loci was scored in 424 lampreys, including 321 European brook lampreys (Lampetra planeri), 83 European river lampreys (L. fluviatilis), 11 Ukrainian brook lampreys (Eudontomyzon mariae), and nine sea lampreys (Petromyzon marinus). Twelve polymorphisms are described for Lampetra species (LDH*, SOD-2*, PNP*, AAT-1*, AK-1*, ES-2*, LGL*, MPI*, GPI-1*. GPI-2*, PGM*, IDHP-2*), and two each for E. mariae (GPI-1*, ME-2*) and P. marinus (MDH-1*, ME-2*). Diagnostic allozymes are presented for the discrimination of lamprey taxa, some of which are difficult to recognize from the morphology of ammocoetes larvae, the life stage usually encountered when collecting cyclostomes. The allelic markers described permit the clear allocation to a genus, except for the species L. fluviatilis and L. planeri, which are not differentiated by qualitative allozyme analysis.
Asunto(s)
Isoenzimas/genética , Lampreas/genética , Hígado/enzimología , Músculos/enzimología , Polimorfismo Genético , Animales , Electroforesis en Gel de Agar , Europa (Continente) , Marcadores Genéticos , Haplotipos , Isoenzimas/análisis , Lampreas/clasificación , Filogenia , Proteínas/análisisRESUMEN
The purpose of this research was to investigate changes in the control of movement, using EMG and kinematic variables, over practice by children. Children in three age groups, 7, 9, and 11 yr., performed 60 trials of an elbow-flexion movement. Correct movements consisted of a 60 degrees angular movement of the forearm in 800 msec. The analysis of biceps brachii and triceps brachii muscle EMG activity, movement displacement and timing error, and movement velocity patterns indicated changes in motor performance with practice. All age groups improved performance with practice and also exhibited a decrease in biceps EMG activity with practice. Only movement-time error and time to peak triceps muscle activity differed between the age groups. The 11-yr.-old group significantly altered the timing of the antagonistic response to stop the movement over the practice session. This change is suggested to be related to the greater information-processing ability of these children and the development of appropriate movement strategies to perform the movement task successfully. Other changes observed in the EMG data appear similar to changes observed in studies of adults.