This study examined the effect of non-contingent feedback on task performance, psychological response, motivation, and physiological activity. It also examined the effects on performance of a subsequent task. To assess task performance, choice reaction time task was employed. Thirty participants were assigned to either receive contingent feedback (i.e., rewards and punishments that were linked to their correct and incorrect reactions: CF) or non-contingent punishment feedback (i.e., always caused punishments to reactions: NCPF) and experienced each feedback during the priming task period. In the subsequent task period, all participants performed the same task which had contingent feedback. Results indicated that task performance was reliably worse in the NCPF group than in the CF group during both the priming task period (p < .01) and the contingent task period (p < .05). The scores of psychological measures indicated that the NCPF group had lower motivation to task than the CF group after both task periods (both p < .05). Blood pressure differed between the groups (p < .05) with the NCPF group having lower mean arterial pressure during the priming task period, however, there was no significant difference during the contingent task period. The NCPF group might have experienced activation of the behavioral inhibition system (BIS; Gray, 1987) not only in the priming task period but also in the contingent task period despite the absence of non-contingent feedback. It could be interpreted as the effect of non-contingent feedback carried over into subsequent period psychologically and behaviorally but not physiologically, despite a change in reward contingencies.
To determine adequate disturbance parameters for forward floor translation for backward balance training, the displacement of the center of pressure in the anterior-posterior direction (CoPy) was measured. Ten young subjects who maintained quiet standing posture with eyes closed on a force platform were perturbed by floor translation (S2) 2-s after an auditory warning stimulus (S1). Three velocities (10, 15, 20 cm/s) and amplitudes (3, 5, 10 cm) of floor translation were combined. CoPy and the electromyogram (EMG) of the tibialis anterior were recorded, and displacement of CoPy, background EMG activity, and integrated EMG (IEMG) were analyzed. IEMG was classified into early, middle and late phases. Displacement of CoPy was significantly correlated with the amplitude of translation. The strongest correlation was observed at 20-cm/s (r = 0.882). CoPy nearly reached the CoPy position in extreme backward leaning (EBL) at 10-cm amplitude and 15-cm/s, and moved significantly more posterior than EBL position at 10-cm amplitude and 20-cm/s. In both conditions, a preparatory increase in background activity before the translation and IEMG decrease in the middle and late phases after the translation were observed. Based on these results, we propose appropriate disturbance parameters for forward floor translation for backward balance training.
We investigated the effect of brain activation with maintenance of neck flexion on the training-related changes in anti-saccade performance and related frontal function. Subjects were 29 young adults who exhibited no significant shortening of anti-saccade reaction time by maintaining neck flexion posture. They were assigned to three groups: training group in a 20° neck flexion position (n = 10), training group in a neck rest position (n = 9), and untrained group (n = 10). Using visual stimuli that were alternately illuminated between a central fixation point and one of 4 lateral targets for a random duration of 1-3 s, anti-saccade training for 30 s was performed 20 times per day. The training was carried out 3-5 days a week for 3 weeks. Before and after the training period, horizontal eye movements, oxy-Hb concentration in the prefrontal cortex, and presaccadic negativity at Cz in anti-saccade tasks were measured in the neck resting and 20° neck flexion positions. Anti-saccade training shortened reaction time and decreased error rate, but these parameters showed no specific effect of incorporating maintenance of neck flexion into training. However, oxy-Hb concentration and presaccadic negativity were changed by the anti-saccade training with maintenance of neck flexion.
The aim of this study was to determine oxidative stress in skeletal muscle and examine the effect of exercise on tissue oxidative stress. Male wistar rats (8 weeks old, n = 30) were used in this study. Rats performed an intermittent downhill running exercise (DH) at -17 degree incline, 25 m/min for a total of 90 min (5-min bouts separated by 2-min rest, 18 bouts). Blood lactate level slightly increased after the DH (p < 0.05). Plasma CK increased 2-3 times immediately after DH and did not return to the pre- value in 2-day recovery period (p < 0.01). Muscle glycogen decreased by 39.2% in soleus (SOL) whereas there was no difference in medial gastrocnemius white portion (GMW) and red portion (GMR) (p < 0.05). Muscular DNA damage (8-OHdG/dG) increased at 24 h after DH in both GMW and GMR, but not in SOL (p < 0.05). Lipid hydroperoxide content increased at 24 h after DH in SOL, but not in GMW and GMR (p < 0.05). SOD activity increased at 24 h after DH in all muscles. Glutathione peroxidase activity increased immediately after DH in GMW. However, glutathione reductase activity reduced at 24 h and 48 h after DH in GMW. These results indicate the effect of exercise on muscular oxidative stress suggesting involvement of massive mechanical stress in enlargement of oxidative stress in fast-twitch fibers.
We used a device with high spatial resolution to measure changes in plantar pressure distribution under the metatarsal head while leaning forwards within a positional range where digital pressure did not rapidly increase. Twenty-six healthy individuals moved forwards while standing at uniform velocity by tracking a target spot displayed on a visual monitor in front of them. The center of pressure in the foot in the anteroposterior direction (CoPy) and the plantar pressure distribution were recorded during the tracking task. Positions of the foot and pressure are represented as either relative distance from the heel to the total length of the foot (%FL) or from the medial surface to the width of the foot (%FW). The force exerted on the metatarsal head increased according to the amount of forward lean, and began to decrease at around 65%FL. The mean position of maximal pressure under the metatarsal head in the quiet standing position (QSP) was located slightly posterior to or between the second or third metatarsal head. This position moved 8.3%FW inwards and 1.3%FL forwards when CoPy was moved from QSP to 60%FL position. The metatarsal head was separated into parts of 1st, 2nd-3rd, and 4th-5th. Among them, the increase in maximal force from QSP was the greatest in parts of 2nd-3rd, whereas the rate of change in pressure in each part was the greatest in parts of 1st. These properties of plantar pressure might provide important positional information for postural control while standing.