Feel Droopy Lifting Weights

[wenhung]

Hi,

Recently I am changing my strength workouts from low resistance/high reps to high resistance/low reps to develop max strength. The schedule looks like this: warm-up, one set of 20 ~ 50 reps with light weights, and then several sets of 3 ~ 6 reps with heavy weights. The problem is when I do the low reps with heavier weights I become somewhat droopy, not tired but sleepy and a little bored.

Is it because my body is hungry? I usually work out between 7 ~ 9 PM. Dinner is after that and usually I do not eat anything after lunch. But I do not feel droopy when doing speed / aerobic / light-weight-high-reps exercises.