The Moneghetti Fartlek

Steve Moneghetti, a four-time Olympic marathoner for Australia, developed a unique fartlek workout that is now used by ZAP Fitness, an elite running team based in North Carolina. ZAP Fitness coach Pete Rea's version of the workout alternates between short bursts of fast and slow running.

o Run two sets of 90 seconds hard (five to 10 seconds per mile faster than 5-K race pace), 90 seconds easy (45 to 50 seconds per mile slower than the hard segments).
o Run four sets of 60 seconds hard, 60 seconds easy.
o Run four sets of 30 seconds hard, 30 seconds easy.
o Run four sets of 15 seconds hard, 15 seconds easy.

The workout sounds similar to Lockwood's recommendation.