Running: Invest in some intervals: Instead of just hitting the road at a steady stride, mix up your pace with short and fast intervals. Run full-blast for about 30 seconds, and then jog or even walk for another minute. Your overall distance may be less, but you'll
get a more intense workout in less time. If you're running on a curved track, run the straight-aways at full speed and jog the curves; if you're running on a street, sprint for several telephone poles and walk for a few more.