Biomedical subjects

M A Guadagnoli

Publications and source records attributed to M A Guadagnoli.

6 recordsLinked to original sources

PubMed2001

Knowledge of results for motor learning: relationship between error estimation and knowledge of results frequency.

The authors of the present study investigated the apparent contradiction between early and more recent views of knowledge of results (KR), the idea that how one is engaged before receiving KR may not be independent of how one uses that KR. In a 2 &times: 2 factorial design, participants (N = 64) practiced a simple force-production task and (a) were required, or not required, to estimate error about their previous response and (b) were provided KR either after every response (100%) or after every 5th response (20%) during acquisition. A no-KR retention test revealed an interaction between acquisition error estimation and KR frequencies. The group that received 100% KR and was required to error estimate during acquisition performed the best during retention. The 2 groups that received 20% KR performed less well. Finally, the group that received 100% KR and was not required to error estimate during acquisition performed the poorest during retention. One general interpretation of that pattern of results is that motor learning is an increasing function of the degree to which participants use KR to test response hypotheses (J. A. Adams, 1971; R. A. Schmidt, 1975). Practicing simple responses coupled with error estimation may embody response hypotheses that can be tested with KR, thus benefiting motor learning most under a 100% KR condition. Practicing simple responses without error estimation is less likely to embody response hypothesis, however, which may increase the probability that participants will use KR to guide upcoming responses, thus attenuating motor learning under a 100% KR condition. The authors conclude, therefore, that how one is engaged before receiving KR may not be independent of how one uses KR.

Adult↗

PubMed2000

A test of a dual central pattern generator hypothesis for subcortical control of locomotion.

This study was designed to examine the nature of neural circuits involved in subcortical inter-limb coordination and reflex modulation mechanisms of locomotion. These circuits, called central pattern generators (CPGs), are believed to receive tonic input and generate rhythmically alternating sets of commands. Although CPGs have been theorized to exist in humans, their potential dual role in inter-limb coordination and reflex modulation is unclear. In the present study, nine participants walked on a treadmill, timing their heel-strikes to a metronome which varied the phase lag from 0.5 to 1.0 pi radians (0.1 pi intervals). A stimulus was delivered to the sural nerve and reflexes were measured in the ipsilateral and contralateral lower extremities through electromyography. The similarity between phase lag conditions for both temporal coordination (i.e., relative timing aspects between muscles and/or limbs) and reflex intensities suggested that they may be controlled by the same subcortical circuitry. Two plausible explanations exist: (1) a single CPG coordinates muscular contractions and phasically alters proprioceptive reflex modulation, as well as cutaneous input, using feed-forward control; (2) two separate circuits are strongly entrained, producing synchronous outputs for inter-limb coordination and reflex modulation. The out-of-phase task used in this study was limited in discerning such a difference, if it exists.

Adult↗

PubMed1999

The effect of hip position and electromyographic biofeedback training on the vastus medialis oblique: vastus lateralis ratio.

OBJECTIVE: PATELLOFEMORAL PAIN SYNDROME IS A PATELLAR TRACKING DYSFUNCTION USUALLY ASSOCIATED WITH VASTUS MEDIALIS OBLIQUE (VMO) WEAKNESS, AND SUBSEQUENTLY, A SMALL VMO: vastus lateralis (VL) ratio. Several early electromyographic (EMG) studies have defined specific limb positions (such as external rotation of the hip) that preferentially activate the VMO. However, whether preferential activation of the VMO successfully translates into increased VMO:VL ratios with training has not been investigated. The purpose of our study was to investigate the effects of hip rotation on the mean VMO:VL EMG ratio using EMG biofeedback training over a 5-day period. DESIGN AND SETTING: Subjects performed isometric quadriceps contractions, in terminal extension, in 1 of 3 hip positions: the anatomically neutral hip position (group A), external hip rotation (group B), and internal hip rotation (group C). Pretest to posttest data were analyzed with a 3 (group) x 2 (test) analysis of variance with repeated measures on the last factor. SUBJECTS: Thirty-six healthy female college students with no known right knee musculoskeletal dysfunction. MEASUREMENTS: Activity of the VMO and VL was recorded by EMG and reported as the VMO:VL ratio. RESULTS: The main effect for group was not significant, but the main effect for test was significant. No significant interaction between group and test was noted. CONCLUSIONS: The statistical analysis of our results suggests that hip position during EMG biofeedback training has no effect on the VMO:VL ratio. However, because subjects were able to significantly increase their VMO:VL ratio in 5 days regardless of hip position, EMG biofeedback can be recommended for the facilitation of VMO muscular recruitment.

Journal Article↗

PubMed1999

Authors' response.

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Journal Article↗

PubMed1996

Optimal length for summary knowledge of results: the influence of task-related experience and complexity.

Because manipulations of knowledge of results (KR) are critical to motor learning, researchers have attempted to establish an optimal length for summary KR. Experiment 1 of the present study investigated the option that optimal summary length may be dependent on a subject's task-related experience. Participants in a summary 1, 5, or 15 condition practiced a simple striking task for one session on three consecutive days with each day followed by a 24-hour no KR retention test. The retention test results indicated that optimal summary length is dependent on task-related experience. Experiment 2 investigated the nature of the relationship between task-related experience and complexity and optimal summary length (summary 1, 5, or 15). Again, striking tasks (simple and complex) were used. There was one practice session with either a simple or complex striking task for either novice or experienced performers, followed by a 24-hour no KR retention test. Data from the two experiments suggest that task complexity and performer experience interact in determining optimal summary length.

Adult↗

PubMed1991

After-contraction phenomenon: influences on performance and learning.

Three experiments investigated the influence of an after-contraction phenomenon on the performance and learning of a dynamic force-production task. The after-contraction effect refers to an involuntary potentiation (induced by a sustained precontraction) that is thought to summate with voluntary motor commands to bias subsequent responding. The precontraction involved a brief (20 s) static contraction. The subsequent influence of the precontraction on a dynamic force-production task was assessed. Experiments 1 and 2 were aimed at demonstrating the direct impact of the precontraction intensity on the magnitude and decay of the after-contraction effect. The results indicated that as the intensity of the precontraction increased, the magnitude of the induced bias increased. In Experiment 3, the indirect influence on subsequent retention of varying the precontraction intensity during acquisition was investigated. The results indicated that the performance of subjects experiencing varying precontraction intensities during acquisition was inferior to that of subjects experiencing a constant precontraction intensity, but the performance of the varied precontraction intensities group was superior on the test of retention. It is noted that the paradoxical reversal from acquisition to retention is similar to that found in contextual interference experiments and may arise from similar mechanisms.

Journal Article↗