Objective:

Monotonous driving involves low levels of stimulation and high levels of repetition and is essentially an exercise in sustained attention and vigilance. The aim of this study was to determine the effects of consuming a high or low glycemic load meal on prolonged monotonous driving performance. The effect of consuming caffeine with a high glycemic load meal was also examined.

Method:

Ten healthy, non-diabetic participants (7 males, age 51 ± 7 yrs, mean ± SD) completed a repeated measures investigation involving 3 experimental trials. On separate occasions, participants were provided one of three treatments prior to undertaking a 90 min computer-based simulated drive. The 3 treatment conditions involved consuming: (1) a low glycemic load meal + placebo capsules (LGL), (2) a high glycemic load meal + placebo capsules (HGL) and (3) a high glycemic load meal + caffeine capsules (3 mg kg− 1 body weight) (CAF). Measures of driving performance included lateral (standard deviation of lane position (SDLP), average lane position (AVLP), total number of lane crossings (LC)) and longitudinal (average speed (AVSP) and standard deviation of speed (SDSP)) vehicle control parameters. Blood glucose levels, plasma caffeine concentrations and subjective ratings of sleepiness, alertness, mood, hunger and simulator sickness were also collected throughout each trial.

Result:

No difference in either lateral or longitudinal vehicle control parameters or subjective ratings were observed between HGL and LGL treatments. A significant reduction in SDLP (0.36 ± 0.20 m vs 0.41 ± 0.19 m, p = 0.004) and LC (34.4 ± 31.4 vs 56.7 ± 31.5, p = 0.018) was observed in the CAF trial compared to the HGL trial. However, no differences in AVLP, AVSP and SDSP or subjective ratings were detected between these two trials (p > 0.05).

Conclusion:

Altering the glycemic load of a breakfast meal had no effect on measures of monotonous driving performance in non-diabetic adults. Individuals planning to undertake a prolonged monotonous drive following consumption of a morning meal may consider consuming caffeine as a means of improving vehicle control.