Between-minute stability in habituated human skill with modestly lowered blood glucose

Modestly lowered blood glucose (G) occurs with fasting and exercise, increasing variability in forces applied during repetitions of an habituated cycling task. Its effect was studied on stability of the movement cycle pattern of forces from minute to minute. Forces applied at 26 positions in the movement cycle were correlated with each other over 20 one minute samples. Six young men worked (a) 3 hr post-prandial, or as (a) but terminated by feeding 100 g (G) slurry (b) immediately before or (c) 30 minutes before exercise. For each sample, data were averaged over subjects, feet, exercise loads (100 W; 150 W) and 40 movement cycles. Over all conditions together, the movement cycle forces were strongly patterned, implying control by pre-set neural programs. Evoked depressions of blood G below fasting coincided with significant reduction in this patterning. It is suggested that in neural control circuits with modestly depressed blood G, there may be increased sensitivity to feedback over movement cycles.