The fundamental concepts for improvement in endurance racing and training involve:

- Increasing your aerobic endurance
- Improving your lactate threshold heart rate (LTHR)

The first is accomplished by completing workouts involving aerobic exercises (swimming, biking, running, rowing, cross-country skiing, and so on) at an easy to moderate effort level. Over time, your ability to continue the exercise will improve through phsyiological adaptations to the specific exercise.

For example, if you are currently untrained or out of shape, a 30 minute bike ride may be challenging and near the limit of your ability. If you go and ride 20-30 minutes three times per week for a few weeks, your body will adapt by; increasing blood flow to the muscles being used; increasing muscle size (hypertrophy); improving blood flow through a process called capillarization (tiny veins to the muscles); increased mitochondrial density (aerobic enzymes) in the muscles; and a few other geeky details.

All these result in the ability to use oxygen as the main exercise energy source more efficiently, meaning you can now ride longer and not be tired at 30 minutes.

The second, improving lactate threshold, is accomplished by completing easier training sessions like the above, plus including more challenging workouts that raise your heart rate.

Lactate threshold is the point in exercise where your body produces more blood lactate than it can reabsorb (and manage other lactate by-products - look up "hydrogen & lactate & exercise" if you want some exciting reading) on a continuous basis. Well trained athletes can usually continue exercise at just below lactate threshold for about an hour. Go over lactate threshold though, and that time drops to 5-6 minutes.

For most people, the lactate threshold is about 20 heart beats per minute above the steady aerobic threshold. Any aerobic exercise, generally speaking, will help both points go a bit higher. But there is a point of diminishing returns. If you don't also include workouts that challenge your system by going just below to above your current lactate threshold, you will not maximize your ability in short distance to long distance events.

The secret or goal with lactate threshold training is to raise your threshold point to as close as possible to your maximum heart rate, and improve your ability to withstand that discomfort (if it was easy everyone would do it). If you never do harder workouts, then your lactate threshold will always remain below your possible maximum lactate threshold.

Raising your lactate threshold point, for the most part, will bring your steady aerobic threshold point up with it (as the 20 bpm relationship is fairly constant).

So. If you're training for an Ironman, from a specificity standpoint you want to train that steady aerobic threshold because that is more or less your race pace. But. You should include some LT training as well to raise that point a bit higher.

If. You're training for a sprint or olympic distance race, from a specificity standpoint you want to work more on that 2nd threshold. But. You shoud include quite a bit of aerobic steady training as that provides your 'foundation.'

Blah blah blah, how do I find my threshold and what are some workouts ideas!!?

Finding it:
Warm up 15-20 minutes then 30 minutes "race effort". As hard as you can go for 30 minutes. Take your heart rate average for the last 20 minutes. Bingo. = LTHR.

Biking:
2 x 20 minutes just below lactate threshold with 5 minutes easy between
5 x 5 minutes at lactate threshold with 3 minutes easy in between
5 x 3 minutes over lactate threshold with 3-5 minutes easy in between
8 x 1 minute well over lactate threshold with 2-3 minutes easy between

Running:
2 x 10 to 15 minutes (1 to 2 miles) just below threshold with 5 minutes easy between
4 or 5 x 4 minutes (800-1200m) at threshold with 2-3 minutes easy between
5 to 6 x 3 minutes (600-800m) over threshold with 3 minutes easy between
8 x 1 minute over threshold with 1 minute easy between
*generally speaking, running causes more breakdown so total "hard" training volume should not be more than 10-15% of weekly mileage.

Swimming:
4 x 400s just below threshold with 1-2 minute between each
12 to 16 x 100s at threshold with 10-15 seconds rest between each
8 x 50 over threshold with 30 seconds to 1 minute rest between each

There are plenty of other workouts, but the theme here is:
sub-threshold workouts take 10-25% interval rest
at-threshold workouts take 50-75% interval rest
over-threshold workouts take 100-200% interval rest

Advanced athletes can do more repetitions and/or take less rest; beginner athletes should do less repetitions and take more rest.

Marty Gaal, NSCA certified strength and conditioning specialist, is a USA Triathlon and USA Track and Field Coach. He works with age-group athletes spanning the ranges of athletic experience and age.