Surfing the implicit wave.

Implicit learning was investigated in two experiments involving a complex motor task. Participants were required to balance on a stabilometer and to move the platform on which they were standing to match a constantly changing target position. Experiment 1 examined whether a segment (middle third) that was repeated on each trial would be learned without participants becoming aware of the repetitions (i.e., implicitly). The purpose of Experiment 2 was to determine the relative effectiveness of explicit versus implicit learning. Here, two identical segments were presented on each trial (first and last thirds), with participants only being informed that one segment (either first or last) was repeated. The acquisition results from both experiments indicated large improvements in performance across 4 days of practice, with performance on the repeated segments being generally superior to that on the non-repeated segment. On the retention tests on Day 5, errors on the repeated segment(s) were smaller than those on the random segment(s). Furthermore, in Experiment 2, the errors on the repeated-known segment, although smaller than those on the random segment, were larger than those on the repeated-unknown segment. Interview results indicated that participants were not consciously aware that a segment was repeated unless they were informed. These results suggest that implicit learning can occur for relatively complex motor tasks and that withholding information concerning the regularities is more beneficial than providing this information.

Performance and learning of generalized motor programs: relative (GMP) and absolute (parameter) errors.

The effects of practice (Experiment 1) and parameter variability (Experiment 2) on the learning of generalized motor programs (GMPs) and movement parameterization were investigated. In each experiment, 2 tasks with different relative force-time structures were tested. Participants (N = 32, Experiment 1; N = 40, Experiment 2) attempted to exert a pattern of force that resembled in force and time a waveform that was displayed on a computer monitor. In both experiments, the analysis suggested that the GMP, although refined over practice, was relatively stable (i.e., resistant to decay and interference), even early in practice (after 20 trials). In addition, the results indicated that constant and variable parameter practice did not differentially affect GMP learning but did degrade the learning of the parameter that was not varied. The data provided additional evidence for the dissociation of the GMP and the parameterization processes proposed in GMP theory. Contrary to schema theory, the present data suggest an interdependence between the force and the time parameters: The manipulation of 1 of the parameters has a negative effect on the learning of the other parameter.

Physical-guidance benefits in learning a complex motor skill.

The effects of physical guidance on learning to perform slalom-type movements on a ski-simulator were examined in 22 participants (18 in Experiment 1, 4 in Experiment 2). In Experiment 1, 1 group of participants practiced the task with ski-poles whereas another group practiced without poles. Retention tests without poles were performed at the end of each of the 2 practice days and 1 day later. Although the use of poles produced more effective performance in terms of movement amplitude during practice, both conditions led to similar amplitudes in immediate and delayed retention. With regard to the efficiency of the movement pattern, the pole group demonstrated a more efficient coordination pattern than the no-pole group did, not only during practice but also in immediate (Day 2) and delayed retention. In Experiment 2, how the poles functioned to enhance the learning of a more efficient movement pattern was examined more closely. The results suggest that physical guidance can have beneficial effects not only on performance during practice but also-under certain conditions-on the learning of motor skills.

Measuring fatigue relative to peak power output during high-intensity cycle sprinting.

The purpose of this report was to introduce and validate a method to account for variable fatigue rates during cycle sprinting by incorporating decline from peak power (30%) as a test termination criterion. Fifteen healthy men performed three maximal sprint tests separated by 20 min (Bouts 1 and 2) and 48 hours (Bout 3). Power curves were analyzed for peak power, time to peak, time to fatigue (decline of 30% from peak), total work, total test time, fatigue rate, and the fatigue index. High test-retest reliability was demonstrated for all variables (R = 0.85-0.98). No significant differences were detected between variables (Bouts 1, 2 and 3; p > 0.01). Fatigue rates varied widely among participants (range = 24.7-65.4 W.s-1), but the fatigue index was consistent (31.1 +/- 0.16; mean +/- standard error of measurement, range = 30.1-32.5%). Our data show that variable fatigue responses among participants are normalized to the percentage of decline from peak power by incorporating a relative fatigue cutoff criterion. This approach might inform mechanisms relating to short-term fatigue and recovery during consecutive sprint bouts.