A threshold is the point at which something changes. Anyone who has been carried (or has carried someone) across a threshold would agree that life changes dramatically thereafter. (For the better, of course!)
As a runner, the threshold you should be most concerned with is your lactate threshold the point at which, during exercise of increasing intensity, your blood-lactate level soars.
When its energy demands are being met aerobically (with oxygen), your body produces little lactate. But as work-out intensity increases and oxygen becomes scarcer, something called anaerobic glycolysis begins. This produces energy and lactic acid. When your lactic-acid level exceeds your bodys ability to deal with it, youre in trouble: blood lactate dramatically increases, energy production and muscle contraction decrease, fatigue ensues and performance drops.
Naturally, the faster you can run without crossing your lactate threshold, the better off youll be. A recent article in the Journal of Medical Science for Sport and Exercise showed that speed at lactate threshold is the best physiological predictor of distance-running performance. Indeed, Frank Shorter, the 1972 Olympic marathon champion was said to have had a modestly high VO2max, but was able to run at a high percentage of VO2max before reaching his lactate threshold. Untrained individuals may reach their lactate threshold at 50-60 per cent of VO2max, elite endurance runners at 70-90 per cent. By training at or slightly above this zone, you can gradually push your threshold upward, allowing you to race faster.
First you need to find your threshold. To do so, you can ask a physiologist to draw and analyse blood from your ear while you run a maximal test on a treadmill. Or, if thats somewhat inconvenient, here is an easy way to make a reasonably close guess: add 35-40 seconds per mile to your 5K race pace, or 15-25 seconds per mile to your 10K race pace.
Then you need to train to raise your threshold. Try the following two training sessions, both run at the same pace. Begin with a one- to two-mile warm-up and a few strides, and finish with a one- to two-mile cool-down.
Its no accident that most hard work-outs performed by Kenyan runners are variations on the tempo run. Take a hint from them, and build a weekly tempo run into your schedule. Run at a steady lactate threshold pace for at least 20 minutes. Over a period of four to six weeks, extend this 20-minute run to four and then five miles.
Run on a flat road or a track where you can check your mile splits to keep your pace steady. If you cant maintain an even pace through the end of the run, youre going too fast. This will be a hard run, but not a race. Remember, youre working at the edge of your threshold not beyond it.
Mexican Tempo Intervals
No, its not a new TGI Fridays lunchtime special. Rodolfo Gomez of Mexico who has coached such runners as German Silva and Adriana Fernandez, both New York City Marathon winners, and who himself finished second at New York in 1982 has had great success with this type of training.
These 1000m repetitions are run at lactate-threshold pace, but with only 60 seconds of recovery between them. Thats enough time to stop, shake your legs out, take a few deep breaths and begin again. These mini-breaks provide a mental break but are short enough to keep blood lactate at close to threshold level.
Gomezs athletes would sometimes run as many as 15 of these, but a more realistic goal would be to start with four and work up to 8-10. The key to this session is to keep the recovery short and the pace consistent. If youre begging for more recovery or your times are slowing after a few repetitions, you started too fast.